Published by the World Health Organization for the International
    Programme on Chemical Safety (a collaborative programme of the United
    Nations Environment Programme, the International Labour Organisation
    and the World Health Organization)


    WHO Library Cataloguing in Publication Data

    International Programme on Chemical Safety

         Users' manual for the IPCS health and safety guides.

         1.Occupational exposure   2.Occupational diseases
         3.Hazardous substances    4.Guidelines   I.Title

         ISBN 92 4 154485 6          (NLM Classification: WA 465)

         The World Health Organization welcomes requests for permission to
    reproduce or translate its publications, in part or in full. 
    Applications and enquiries should be addressed to the Office of
    Publications, World Health Organization, Geneva, Switzerland, which
    will be glad to provide the latest information on any changes made to
    the text, plans for new editions and reprints and translations already

    (c) World Health Organization 1996

    Publications of the World Health Organization enjoy copyright
    protection in accordance with the provisions of Protocol 2 of the
    Universal Copyright Convention.  All rights reserved.

    The designations employed and the presentation of the material in this
    publication do not imply the expression of any opinion whatsoever on
    the part of the Secretariat of the World Health Organization
    concerning the legal status of any country, territory, city or area or
    of its authorities, or concerning the delimitation of its frontiers or

    The mention of specific companies or of certain manufacturers'
    products does not imply that they are endorsed or recommended by the
    World Health Organization in preference to others of a similar nature
    that are not mentioned.  Errors and omissions excepted, the names of
    proprietary products are distinguished by initial capital letters.






       1.1. The need to identify chemicals in the workplace and
            1.1.1. Basic chemistry
            1.1.2. Terminology
       1.2. Physical and chemical properties
            1.2.1. Physical state
            1.2.2. Smell and odour threshold
            1.2.3. Physical properties
            1.2.4. Composition
       1.3. Analytical methods
       1.4. Production and uses


       2.1. Exposure
            2.1.1. Inhalation
           Entry into the body
            2.1.2. Absorption through the skin
           Entry into the body
            2.1.3. Absorption through the eye
           Entry into the body
            2.1.4. Ingestion
           Entry into the body
       2.2. Processing of chemicals in the body
            2.2.1. Metabolism
            2.2.2. Excretion
            2.2.3. Storage or accumulation
       2.3. Toxic effects of chemicals
       2.4. Effects on body systems
       2.5. Dose, effects and response
       2.6. How is the toxicity of a chemical determined?

            2.6.1. Animal studies
           Acute toxicity tests
           Subchronic toxicity tests
           Chronic (lifetime) bioassays
           Short-term mutagenicity tests
           Reproductive studies
           Behavioural tests
            2.6.2. Human evidence
           Case reports
           Epidemiological studies
            2.6.3. Environmental assays
       2.7. Assessing hazards, risks and safety
            2.7.1. Hazard
            2.7.2. Risk
            2.7.3. Safety


       3.1. Identification
       3.2. Evaluation
       3.3. Safety organization
       3.4. Controlling the hazard
            3.4.1. Substitution
            3.4.2. Engineering controls
           Total enclosure
            3.4.3. Safe working procedures
            3.4.4. Reducing the number of exposed workers
                   and their duration of exposure
            3.4.5. Personal protective equipment
           Protective clothing
           Do you need a respirator?
           Types of respirators
           Training and fitting
           Respiratory protection programme
       3.5. Monitoring the hazard
            3.5.1. Environmental monitoring
            3.5.2. Biological monitoring


       4.1. First aid and emergencies
       4.2. Health surveillance
       4.3. Fire and explosion hazards

            4.3.1. Flammable substances
            4.3.2. Dust explosions
            4.3.3. Sources of ignition
            4.3.4. Fire-fighting
       4.4. Storage
       4.5. Spillage
       4.6. Disposal
            4.6.1. Means of disposal
            4.6.2. An example of the effects of incorrect waste


       5.1. How do chemicals get into the environment?
       5.2. How do chemicals affect the environment?
            5.2.1. Air
            5.2.2. Water and soil
       5.3. Factors affecting a cemical's environmental impact
       5.4. The importance of prevention



       7.1. Exposure limits
            7.1.1. Threshold limit value
            7.1.2. Maximum allowable concentration
            7.1.3. Other terms for occupational exposure limits
            7.1.4. Health-based exposure limits
            7.1.5. Exposure limits for food products
       7.2. Specific restrictions
       7.3. Labelling, packaging and transport




    ADI          Acceptable Daily Intake
    EC           European Community
    FAO          Food and Agriculture Organization of the United Nations
    HSG          Health and Safety Guide
    ICSC         International Chemical Safety Card
    ILO          International Labour Organisation
    IPCS         International Programme on Chemical Safety
    kPa          kilopascals
    MEK          methylethylketone
    mg/m3        milligram per cubic metre
    MSDS         material safety data sheet
    PCP          pentachlorophenol
    ppm          parts per million
    UN           United Nations
    WHO          World Health Organization


    This manual summarizes the basic information concerning chemical
    safety that is required for understanding the terms and concepts used
    in the IPCS Health and Safety Guides.  The first draft was prepared by
    the Workers Health Centre, Lidcombe, New South Wales, Australia.  It
    was distributed for comments to IPCS Participating Institutions, other
    agencies involved in chemical safety and nongovernmental organizations
    representing trade unions, employers and consumers.

    The efforts of all who provided comments and materials for the manual,
    of Mr L. Strange and Ms J. Connor in coordinating the preparation of
    the first draft and of Ms A. Rice and Ms M. Sheffer in undertaking the
    technical editing are gratefully acknowledged.  Production of the
    manual was supervised for the IPCS by the WHO Office of Global and
    Integrated Environmental Health.  Financial support was provided by
    the IPCS and the Federal Ministry for the Environment, Nature
    Conservation and Nuclear Safety, Germany.


    The rapid development of chemical products during the last 100 years
    has improved the quality of life.  However, this has not been without
    cost to the community, and particularly to those who work directly
    with chemicals.  It is estimated that chemical exposure at work alone
    is responsible for at least 4% of all deaths from cancer, reaching as
    high as 80% for certain types of cancer.  Large numbers of workers may
    suffer from other forms of illness caused by chemicals. The long-term
    effects of chemical pollution of the environment, and of our food, are
    only now beginning to be realized.  In some polluted areas, major
    outbreaks of poisoning have occurred; chemical food poisoning is an
    increasing concern.

    It is therefore essential that everyone involved in the manufacture,
    use, storage, transport and disposal of chemicals is fully aware of
    the dangers that many chemicals can pose to health.

    The International Programme on Chemical Safety (IPCS) (jointly
    sponsored by the United Nations Environment Programme, the
    International Labour Organisation (ILO) and the World Health
    Organization) produces a series of Health and Safety Guides (HSGs) and
    one of International Chemical Safety Cards (ICSCs), which summarize
    what is known about the health effects of chemicals commonly used in
    the working environment.

    The target audience of the HSGs includes occupational health services;
    individuals working in ministries, governmental agencies, industry and
    trade unions who seek to promote the safe use of chemicals and the
    avoidance of environmental health hazards; and those who wish to
    obtain more information on this topic.  The ICSCs are intended for use
    by workers on the "shop-floor" and other interested parties in
    factories, agriculture, construction and other places of work.

    An attempt has been made in both the HSGs and the ICSCs to use terms
    that are familiar to the reader.  However, some technical terms are
    inevitable, so this Manual provides some background to the technical
    terms and concepts used in the HSGs and ICSCs.  The principal target
    audience for this Manual consists of workers' health and safety
    representatives and members of community organizations active on
    environmental chemical issues.  Nevertheless, the HSGs will have a
    wider readership.

    This Manual demonstrates how the information in the HSGs can be put to
    practical use to improve the health and safety of workers and the
    general community. The methods for improving health and safety
    outlined in this Manual should thus be regarded as essential parts of
    the chemical production, use and disposal process.  They are not

    luxuries or optional requirements.  Rather, they are an integral part
    of chemical use for  all workers in  all workplaces -- in the
    factories, fields, offices and multitude of other locations that
    constitute the world's workplaces -- in both developed and developing
    nations. Chemical safety may be integrated relatively easily in
    "fixed" workplaces, in manufacturing and the larger downstream
    industries that are users of chemicals, as the resources and structure
    for medical services, occupational hygienists, joint worker/employer
    health and safety committees, etc. are often available.  Nevertheless,
    the information and principles outlined in this Manual also apply to
    users of chemicals in agriculture (many HSGs and ICSCs are concerned
    with pesticides) and other workplaces.

    The contents of this Manual will be reviewed and revised as new HSGs
    are published.  You can help by letting us know about any difficulties
    you have in using this Manual or the HSGs and ICSCs, and any sections
    or points that could be improved.

    Please address all comments to:

    The Director

    International Programme on Chemical Safety
    World Health Organization
    1211 Geneva 27


    The format of this Manual closely follows the format of the IPCS
    Health and Safety Guides.  Each chapter of the Manual relates to a
    corresponding  chapter in the HSGs.

    It is not necessary to read the Manual from cover to cover all at
    once. The Manual is best used as a reference in the practical tasks of
    worker protection.

    You can use an HSG on a particular chemical as follows:

    a)   Read Chapter 1 of this Manual -- "Product Identity and Uses".
    After reading this chapter, try to identify which chemicals are being
    used in your workplace.

    After drawing up a list of chemicals, obtain the relevant HSG (see the
    list of published guides in the Annex).  You may also wish to seek
    further health and safety information on the product concerned (see
    Chapter 8 -- "Getting Further Information").

    b)   Read each chapter of the HSG, followed by the corresponding
    chapter of the Manual.  (Although great effort has been made in this
    Manual to follow the layout and general headings of the HSGs, this
    has not always been possible.  This is especially the case when
    cross-references are made to sections of the text and numbers of some
    of the figures reproduced directly from the HSGs.  Moreover, the HSGs
    themselves have evolved over time, so that the numbering of sections
    within them has changed.  However, each chapter in the Manual does
    correspond to the relevant chapter in the HSGs.)  After reading each
    section, think about how the information in the HSG applies to your
    place of work.  Make a list of possible improvements that could be
    made to chemical storage, handling, usage and disposal, and of
    possible improvements that could be made to protect workers from
    unnecessary exposure to chemicals.  Also, list any questions about the
    hazards of chemicals used in your workplace.

    c)   Discuss this list of questions and proposals with representatives
    of your trade union or health and safety committee.  If these channels
    are not available, bring up the issues directly with your co-workers. 
    For more information on the role of trade unions and health and safety
    committees and some suggestions on how to organize for better safety,
    turn to the section entitled "Safety organization" in Chapter 3 of
    this Manual.  Safety questions and proposals can also be discussed
    with your immediate supervisor or safety officer.

    After discussions with your trade union or health and safety
    committee, formally present your comments to management and ask for a
    response within a specified time.

    If there is an unsatisfactory or no response from management, or if
    there is a positive response but no action, raise the matter again
    through the agreed grievance or dispute-settling procedures of your
    workplace. Always insist that reasonable time limits are set for the
    resolution of the dispute.

    If all of the above steps fail, contact the health and safety officer
    of your trade union or some other suitable official. Send a copy of
    your questions and suggestions to the Factory Inspectorate or other
    government body responsible for health and safety in the working
    environment.  In most countries you have the right to remain anonymous
    when contacting the Factory Inspectorate.

    If you are a member of the public who considers that harmful pollution
    of the environment by chemicals is occurring, contact your local
    member of government and the local or national government body
    responsible for pollution control, the environment and food safety.

    Many government departments can provide information about the health
    effects of chemicals in the workplace and general environment.
    Moreover, there is an increasing number of nongovernmental bodies,
    operated by trade union, industry and public interest groups, that
    offer similar information services.

    But before approaching any of these information services for further
    assistance, it is always helpful to collect as much information as
    possible about the names and manufacturers of chemicals used in your
    workplace. Refer to Chapters 6, 7 and 8 for details and ideas on where
    and how to find information on chemicals.


    This chapter should be read in conjunction with Chapter 1 (Product
    Identity and Uses) of the relevant HSG.

    1.1  The need to identify chemicals in the workplace and environment

    Everyone should have the right to know the identity and nature of any
    chemicals to which he or she may be exposed in the workplace or
    general environment (e.g. through contamination of air, water or

    Without knowledge of the health effects of the chemicals with which
    they work, workers and managers are unable to protect themselves, or
    others, effectively from any adverse health effects that these
    chemicals might cause.

    The first essential step is to determine the exact identity of the
    chemicals that are present in the workplace or environment. 
    Unfortunately, more often than not, chemicals are labelled in the
    workplace by trade name only or are known under a rare synonym.  To
    follow up on the potential health hazards, however, it is necessary to
    know the chemical name of the product (see Fig. 1).  Although the
    way in which chemicals are named may seem confusing or even
    intimidating, some basic knowledge of chemistry is all that is needed
    to determine their nature correctly.

    FIGURE 1

    1.1.1  Basic chemistry

    All matter (i.e. liquids, solid substances and gases) is made of
    elements.  An element is the simplest sort of matter that can exist
    by itself.  So far, 106 different elements are known, including
    oxygen, nitrogen, carbon, aluminium, copper and iron.

    An atom is the smallest unit of an element that can still retain the
    properties of the element.  The atoms of the same element are exactly
    alike, with the same mass, etc.  The atoms of different elements,
    however, have different masses and also differ in their ability to
    combine with other atoms.

    When atoms of one element combine chemically with atoms of the same
    element or other elements, the result is a molecule.  The process
    whereby atoms combine and rearrange themselves is known as a chemical
    reaction.  Chemical reactions may occur slowly, taking hours or days
    to complete, or they may occur suddenly or violently, as in an

    Combinations of two or more different elements are also called
    chemical compounds.  Substances such as water and carbon dioxide,
    which can be broken down into their constituent elements -- hydrogen
    and oxygen in the case of water, and carbon and oxygen in the case of
    carbon dioxide -- are examples of compounds.  There are nearly six
    million different chemical compounds known, each with its own
    particular combination of the atoms of various elements.  This number
    is increasing all the time.  However, the number of potentially useful
    chemical compounds is much less, and about 1500 chemicals account for
    90% of the total volume of all chemical compounds produced.

    A pure substance is a chemical that contains only a single chemical
    compound or element, i.e. all the molecules are the same.  The
    compound that makes up the pure substance may contain the atoms of
    many different types of elements, all combined chemically.  A
    mixture, on the other hand, is a substance that contains more than
    one chemical compound or element, the separate constituents of which
    will still have their own properties.

    A suspension is a mixture of a liquid and tiny particles of a solid
    substance (powder).  A mist or aerosol is the mixture of tiny droplets
    of a liquid, or tiny particles of a solid, in a gas.  Although the
    powder or droplets may be very fine, each particle of powder or each
    droplet contains many millions of molecules of the chemical compound. 
    In a solution, individual molecules of one substance (the solute)
    are dissolved in another substance (the solvent).

    1.1.2  Terminology

    Chemicals are identified in the HSGs as follows (see Fig. 2):

    Common name -- This is the name that appears on the cover of the HSG
    and is the commonly used name of the chemical in question.  Sometimes
    the common name refers to the elements that make up a chemical
    compound, e.g. hydrogen sulfide contains elements of hydrogen and

    Chemical formula -- The chemical formula uses symbols to represent
    the atoms of each element contained in each molecule of the chemical
    compound in question.

    Table 1 gives the symbols of some of the more common elements.  These
    symbols come from the Latin name (Au for gold -- Latin: Aurum; Cu for
    copper -- Latin: Cuprum).  Sometimes the first letter is the same in
    the English name (O for oxygen, C for carbon).

    A formula for a molecule will also show a small number (or
    subscript) below the level of the symbol, which indicates how many
    atoms of that particular element are present in the molecule.

    Using the example shown in Fig. 2, the chemical formula for phosphorus
    trichloride -- PCl3 -- shows that it consists of one atom of
    phosphorus and three of chlorine; the formula for phosphorus
    oxychloride -- POCl3 -- shows that the chemical is made of one atom
    of phosphorus, one of oxygen and three of chlorine.


    Figure 2.  Chemical identity (from HSG 35: Phosphorus Trichloride)

    1.1  Identity

                           Phosphorus               Phosphorus
                           Trichloride              Oxychloride

    Chemical formula:      PCl3                     POCl3

    Chemical structure:          Cl                    Cl
                                 |                     |
                           Cl -- P                  Cl P == O
                                 |                     |
                                 Cl                    Cl

    Common synonyms:       Phosphorus chloride;     Phosphorus
                           phosphorus chloride;     oxytrichloride

    Abbreviations:         Tri;  "Pickle"           Oxy;  "Pockle"

    CAS registry number:   7719-12-2                10025-87-3

    RTECS number:          TH3675000                TH4897000

    UN number:             1809                     1810 (II)

    Conversion     1 ppm = 5.62 mg/m3 and    1 ppm = 6.27 mg/m3 and
    factor:        1 mg/m3 = 0.178 ppm       1 mg/m3 = 0.159 ppm
                   [at 25C and 101.3 kPa    [at 25C and 101.3 kPa
                   (760 mmHg, 1 bar)]        760 mmHg, 1 bar)]

    Table 1.  Selected elements and their symbols

    Element        Symbol         Element         Symbol

    Aluminium        Al           Magnesium         Mg
    Bromine          Br           Mercury           Hg
    Calcium          Ca           Nitrogen          N 
    Carbon           C            Oxygen            O 
    Chlorine         Cl           Phosphorus        P 
    Chromium         Cr           Potassium         K 
    Copper           Cu           Silicon           Si
    Gold             Au           Sodium            Na
    Helium           He           Sulfur            S 
    Hydrogen         H            Tin               Sn
    Iron             Fe           Uranium           U 
    Lead             Pb           Zinc              Zn

    Chemical structure -- The chemical formula tells us how many atoms
    of each element are combined in a compound, but not about how these
    atoms are arranged.

    The chemical structure diagram is a graphical representation of the
    pattern in which atoms are combined in a chemical compound.  Such
    diagrams give information about the arrangement in two dimensions
    only: in real life, molecules are not flat.  Nevertheless, the
    chemical structure can constitute important information about the
    potential health effects of a chemical.

    It is possible for two different chemical compounds to have the same
    chemical formula (i.e. the same type and number of atoms in each
    molecule) but different chemical structures (i.e. the atoms have
    combined in a different arrangement).  When this is the case, the
    chemicals are known as isomers of each other.  Isomers are often
    identified by one or more numbers, letters or Greek symbols in front
    of the same chemical name.  For example, 1-butanol, 2-butanol,
    isobutanol and  tert-butanol all have the same chemical formula
    (C4H10O) but different chemical structures (see Fig. 3).

    There may be little or no difference between the effects of different
    isomers on the health of those exposed to them.  But in many cases
    there are very important differences between the health effects of

    For example, 1,1,2-trichloroethane has been shown to cause cancer in
    experimental animals, although the evidence is limited.  On the other
    hand, 1,1,1-trichloroethane has not been shown to cause cancer in
    animals.  The exposure limit for 1,1,1-trichloroethane in most
    countries is much higher than that for 1,1,2-trichloroethane,
    indicating that the former is thought to be much less hazardous.  It
    is easy to see that only a small change in the structure of a chemical
    may make it much more toxic (or less so).  The lesson from this is
    that numbers and letters are an important part of some chemical names,
    so these should be carefully noted when checking a substance.

    Common trade names -- Manufacturers often choose to give chemical
    compounds, or mixtures of chemical compounds, commercial names. 
    This is usually done to make advertising and selling of the product
    easier (many chemical names are very long or difficult to remember) or
    to distinguish a product from that of a competing manufacturer.  Often
    trade names refer to the name of the manufacturer or to the use of the
    product (e.g. Cellosolve was originally used to dissolve cellulose in
    lacquers).  A trade name may also be used because it conceals
    knowledge of what is in a product or how it is made.  However, this
    should never be accepted as a reason for concealing the identity of
    chemicals from those who work with them.

    Common synonyms -- Synonyms are alternative names for the same
    substance.  The same chemical may have a number of different names
    because of the many different chemical naming systems that have
    developed, e.g. phosphorus trichloride is also known as phosphorus
    chloride or trichlorophosphine.


    Figure 3.  Identity of chemical isomers
               (from HSGs on butanol isomers)

    1.1  Identity

    Chemical formula:       C4H10O

    Chemical structure:     CH3-CH2-CH2-CH2OH

    Primary constituent:    1-butanol

    1.1  Identity

    Chemical formula:       C4H10O

    Chemical structure:     CH3-CHOH-CH2-CH3

    Primary constituent:    2-butanol

    1.1  Identity

    Chemical formula:       C4H10O

    Chemical structure:     CH3

    Primary constituent:    isobutanol

    1.1  Identity

    Chemical formula:       C4H10O

    Chemical structure:          CH3
                            CH3 -- C -- CH3

    Primary constituent:     tert-butanol

    CAS registry number -- This is a number assigned to every chemical
    by the Chemical Abstracts Service, a section of the American
    Chemical Society, which publishes guides to chemical research.  Each
    chemical is given a unique number.

    The CAS number does not give any information about the properties of
    the chemical itself.  Its value is in overcoming the confusion caused
    by the different chemical naming systems (see "Common synonyms"
    above).  The CAS number will often be given in product information or
    literature that accompanies chemicals.

    RTECS number -- RTECS stands for Registry of Toxic Effects of
    Chemical Substances.  This is a list of scientific articles on the
    health effects of the chemicals.  The Registry is operated by the
    National Institute for Occupational Safety and Health, a government
    body in the United States.  Each chemical that is listed is given a
    unique number.  About 25 000 chemicals commonly used in industry are

    Other numbering systems and nomenclatures are also used for
    classifying chemicals.  Those used in the HSGs include the IUPAC
    (International Union for Pure and Applied Chemistry) name, EC numbers
    assigned by the European Community and UN numbers for the transport of
    dangerous goods.

    Conversion factor -- The concentration or amount of chemical present
    in air, water or food can be expressed in a number of different units. 
    The conversion factor allows these measurements to be converted from
    one to another: "ppm" stands for parts of the chemical per million
    parts of air and thus is a ratio of volumes; "mg/m3" stands for
    milligrams of the contaminant per cubic metre of air; "kPa" stands for
    kilopascals, a unit of pressure; and "mmHg" means millimetres of
    mercury (760 mmHg is the normal atmospheric pressure at sea level).

    1.2  Physical and chemical properties

    1.2.1  Physical state

    This section of the HSG includes a description of the physical form of
    the chemical.

    Chemicals may be gases, liquids or solids.  They can change
    between these "states" depending on temperature and pressure.  For
    instance, water is a liquid within the temperature range 0-100 degrees
    Celsius (C).  Below 0C, water is in a solid state (ice), and above
    100C it is in a gaseous state (steam) (see Fig. 4).  When the
    temperature of a solid is increased, it generally turns into a liquid,

    i.e. it melts.  If the liquid is heated further, it will turn into a
    gas or vapour and boil or evaporate.  If pressure is increased without
    a change in the temperature, gases may convert from the gaseous to a
    liquid state.

    Some chemicals can exist in only two states, passing from solid to gas
    and vice versa without going through a liquid phase.

    1.2.2  Smell and odour threshold

    The smell of a chemical can sometimes serve as a warning of exposure. 
    However, it must always be remembered that smell is not a
    reliable means of warning, as many chemicals have no smell
    at all.

    FIGURE 4

    The "odour threshold" is the concentration at which humans can first
    smell the substance in question.  Yet many chemicals are dangerous at
    concentrations well below the odour threshold.  Moreover, sense of
    smell varies greatly from person to person and can be affected by nose
    and throat infections or head injuries.  Finally, the sense of smell
    can become "tired" (known as olfactory fatigue or olfactory
    adaptation) if a person is exposed to the smell of a chemical for more
    than a few minutes.  If this happens, a large (and often dangerous)
    increase in the amount of chemical present may be necessary before it
    can again be smelt by those working with it.  IT IS DANGEROUS TO

    1.2.3  Physical properties

    The physical properties of each chemical are given in the
    International Chemical Safety Card, or Summary of Chemical Safety
    Information, contained in most HSGs (see Fig. 5).  The terms used are
    explained below.  Further information can be obtained from the Card
    Users' Guide, also produced by the IPCS to assist the user of the

    Boiling point -- The temperature at which all the substance changes
    from a liquid into a gas, e.g. water changes to steam at 100C.  It is
    important to be aware of this temperature because when a chemical
    substance is heated above the boiling-point, it will become a gas, and
    it is much more difficult to protect against exposure to gases than to
    protect against exposure to liquids or solids.  Therefore, many
    chemicals are more hazardous when heated.  As mentioned below (see
    Vapour pressure), some of the chemical will turn into a gas even at
    temperatures below the boiling point.  This can cause a dangerous
    build-up of gas.

    Melting point -- The temperature at which a substance changes from a
    solid to a liquid, e.g. ice changes to water at 0C.


    Figure 5.  Physical properties of a chemical (from HSG 9: Isobutanol)


    Boiling point (C)                    108      Colourless liquid with
    Melting point (C)                   -108      characteristic odour;
    Flash point (C)                      27       reacts with strong oxidants
    Auto-ignition temperature (C)        430      and alkali metals to form
    Relative density (water = 1)          0.8      combustible gas (hydrogen);
    Relative vapour density (air = 1)     2.6      attacks many plastics;
    Vapour pressure in mbar (20C)        12       substance may be absorbed
    Solubility in water                   95       into the body by inhalaltion
     (g/litre at 20C)
    Explosive limits (vol. % in air)    1.2-10.9
    Relative molecular mass               74.1
    Flash point (open or closed cup) -- The flash point is the
    temperature at which a substance gives off enough vapour to form an
    ignitable mixture with air, i.e. one that burns when exposed to a
    flame or spark.  Open and closed cup refer to the way in which the
    flash point is determined.  In general, the open cup method gives a
    better approximation of real-life situations.  If the flash point
    temperature is 20C or lower, a spark can ignite the vapour, even at
    normal room temperatures, and, in such cases, great care must be taken
    to reduce the risk of accidental fire.  The lower the flash point, the
    greater the fire risk.  Methods of reducing fire risk are discussed in
    Chapter 4.

    Auto-ignition temperature -- The lowest temperature at which a
    substance will burn without being exposed to a flame or spark.  The
    closer this value is to room temperature, the greater the risk of

    Relative density or specific gravity (at 20C) -- The weight
    of a specific volume of solid or liquid chemical substance compared to
    the weight of the same volume of water.  A substance with a specific
    density greater than 1 will sink in water; if the specific density is
    less than 1, the substance will float on water.

    Relative vapour density -- The weight of a specific volume of a
    gaseous chemical substance compared to the weight of the same volume
    of air.  This is also a very important safety consideration.  If the
    relative vapour density of a pure gas is less than 1, the gas will
    rise and collect at ceiling level (if indoors) or disperse into the
    atmosphere (if outdoors).  On the other hand, if the relative vapour

    density of a gas is greater than 1, the gas is heavier than air and
    will sink and tend to collect at floor level or in depressions.  Such
    collection can result in unexpectedly high exposures to the substance,
    can lead to a fire, or can represent an explosion hazard.  In some
    circumstances, gases that have a relative vapour density greater than
    1 may completely replace air, including the oxygen that is essential
    for life, leading to asphyxiation (suffocation).  This often occurs in
    tanks, pits or ship holds that are being cleaned or fumigated.  This
    situation can be avoided by ventilating areas in which gases or
    vapours may collect.  The vapours of most flammable liquids are
    heavier than air.  However, in workplace situations, the vapour
    concentrations are generally at the level of a few hundred parts per
    million (ppm), and the vapours will follow air streams and rise with
    heat.  In these situations, local exhaust should be as close to the
    emissions as possible.  Local exhaust near ground level is useful in
    case large amounts of liquid leak or are spilled, which could lead to
    noticeable vapour formation.

    Vapour pressure (kPa) -- The pressure of the vapour produced by a
    liquid or solid at room temperature.  A small amount of the substance
    is transformed from the solid or liquid state to the gaseous state
    (vapour) at all temperatures -- evaporation (or sublimation if the
    substance changes directly from a solid to a gaseous state without
    going through a liquid phase).  The higher the vapour pressure, the
    more vapour will form above the liquid or solid, i.e. the faster it
    tends to evaporate.  The vapour pressure of a chemical rises as the
    chemical is heated.  This vapour or gas could be inhaled by workers.

    Solubility in water (g/litre at 20C) -- The amount (by weight)
    of the substance that can be dissolved in 1 litre of water to form a
    solution.  The solubility in water may give some idea of what maximum
    concentrations might occur in water bodies.  A high solubility
    indicates quick dissipation in surface water, with a potential for
    causing acute toxic effects, e.g. to aquatic organisms in the case of
    large chemical spills.  For some compounds with low solubility,
    aquatic organisms will not be so readily threatened by exposure to
    potentially acute toxic concentrations.

    Flammability (explosive) limits -- The range of concentrations
    of a flammable gas or vapour in air at which it may explode in the
    presence of a spark or flame.  Below the lower limit (Lower Explosive
    Limit, or LEL) there is not enough chemical to burn; above the upper
    limit (Upper Explosive Limit, or UEL) the mixture is too rich,
    i.e. too much chemical is present and not enough oxygen.

    Relative molecular mass -- This is the relative weight of the
    molecule of a chemical compared to the weight of one atom of hydrogen
    (the lightest element).

    Octanol/water partition coefficient -- This number indicates
    how readily a chemical can dissolve in fats and oils.  If the
    octanol/water partition coefficient is high, e.g. for DDT it is about
    6, then the chemical can accumulate more readily in body fat and can
    be stored there for a very long time, as it may be excreted very
    slowly.  The octanol/water partition coefficient is therefore an
    indicator of bioaccumulation.  Chemicals that dissolve easily in
    fats can usually be absorbed through the skin and may thereafter enter
    the bloodstream.  An example of a chemical that does not pass easily
    through the skin is dimethyl sulfate (DMS), which has an octanol/water
    partition coefficient of -4.26.  However, DMS can burn the skin badly,
    so a low octanol/water partition coefficient should not be seen as
    evidence that a particular chemical will not have a negative health
    effect if it comes into contact with the skin.

    1.2.4  Composition

    This section gives details of other substances that may be mixed with
    the chemical in question.  In some cases, these other chemicals may be
    the unwanted result of the manufacturing process, in which case they
    are called contaminants or impurities.  In other cases, other
    chemicals are added deliberately, e.g., to prevent undesirable or
    unwanted chemical reactions, such as polymerization or oxidation.

    It is important to know what other chemicals may be present in a
    substance, as the combined health effects of the chemicals may be far
    greater than would be expected by simple addition of the health
    effects of the individual chemicals.  This increased effect of two or
    more chemicals is known as "synergism" and is discussed further in
    Chapter 2 of this Manual.

    1.3  Analytical methods

    This section deals with methods for determining the concentration of
    the chemical or its degradation products in the environment and in
    foodstuffs (see Fig. 6).


    Figure 6.  Analytical methods (from HSG 34: Fenvalerate)

    1.3  Analytical Methods

    For residue and environmental analysis, gas chromatography with
    electron-capture detection is used, the minimum detection level being
    0.005 mg/kg.  For product analysis, gas chromatography with flame
    ionization detection can be used.

    1.4  Production and uses

    The HSGs list the common uses for chemical substances. Many chemicals
    are used in a large variety of products and processes (Fig. 7).  For
    many chemicals it is not possible to list all possible uses.  A
    careful check should always be made of the chemical that will be used
    for a particular type of work or task.


    Figure 7.  Uses of methylene chloride
               (from HSG 6: Methylene Chloride)

    1.4  Uses

    Methylene chloride is widely used as a solvent and paint remover.
    It is also used as a blowing agent for polyurethane, as a propellant
    in aerosols such as insecticides, hair sprays, shampoos, and paints,
    as a component in fire-extinguishing products, as an insecticidal
    fumigant for grains, and as a coolant or refrigerant.

    Many HSGs are concerned with the use of chemicals as pesticides and
    the associated terminology may need some explaining.

    The word pesticide is used as a general term for any substance, or
    mixture of substances, intended for controlling the presence of
    unwanted plants, animals, insects, etc.  As much as possible,
    pesticides are designed to control only target species of pests; their
    general names then denote the type of pesticide, e.g.:

    *    acaricides         -->  spiders and ticks;
    *    fungicides         -->  fungi;
    *    herbicides         -->  weeds;
    *    insecticides       -->  insects;
    *    larvicides         -->  larvae of insects or other organisms;
    *    miticides          -->  mites;
    *    molluscicides      -->  snails; and
    *    rodenticides       -->  rats, mice and other rodents.

    Pesticides kill or control pests by interfering with one or more of
    their essential body systems.  Most pesticides belong to a few
    chemical groups, each of which has its own effect on certain systems,
    e.g. organophosphorus compounds affect nerve function by inhibiting
    the action of cholinesterase, an essential chemical for the passage of
    impulses along nerves.  Small changes in the chemical structure of
    compounds in a group can result in some species being affected more by
    those compounds than by others in the same group.  This is why some
    chemicals are more selective than others in their action on certain
    pests.  Pesticides that tend to kill a variety of organisms, including
    both pests and others, are known as broad-spectrum pesticides.

    Pesticides may act on target species in several ways: e.g. a pesticide
    that kills pests by first passing through the skin or outer layer is a
    contact poison; one that kills the pest by first passing into the
    stomach is a stomach poison.  A pesticide that kills a pest as it
    flies through the air is a fumigant.  Fumigants usually apply
    strictly to pesticides in the form of a gas or vapour, but sometimes
    when droplets or an aerosol of a pesticide acts on flying pests (i.e.
    essentially a contact poison), the pesticide is said to have a
    fumigant action.

    A systemic pesticide is one that can be readily absorbed and
    transported in plant tissue and, without affecting the plant, can
    exert its action on pests feeding on the plant.  It is usually applied
    to the leaves or the soil around the plant so that it can pass through
    the roots.  Systemic herbicides are designed to kill the plant
    itself if it is a weed.

    Pesticides are available as technological products, i.e. the
    pesticide chemical plus impurities that may be associated with its
    manufacture (as opposed to purer laboratory versions).  The pesticide
    chemical is also known as the active ingredient.  The active
    ingredient is usually mixed with other chemicals to facilitate its
    use.  It is then known as a formulation.  Some formulations may need
    further dilution.

    When a formulation is designed mainly to facilitate use and increase
    the effectiveness of the active ingredient, it may be modified to
    increase the safety of handling the pesticide.  Some examples include:

    *    soluble powders or granules to be added to water;
    *    dusts or dustable powders applied as such;
    *    pellets or paste used as baits;
    *    tablets to generate smoke, gas or vapour;
    *    emulsifiable concentrates to be added to water;
    *    aerosol generators;
    *    pour-ons for direct application to the skin of animals; and
    *    shampoos for humans.


    This chapter should be read in conjunction with Chapter 2 (Summary and
    Evaluation) of the relevant HSG (see Fig. 8).


    Figure 8.  Summary and evaluation (from HSG 7:  tert-Butanol)




    2.1    Exposure to tert-butanol                             13
    2.2    Uptake, metabolism, and excretion                    13
    2.3    Effects on organisms in the environment              13
    2.4    Effects on animals                                   13
    2.5    Effects on human beings                              14

    2.1  Exposure

    Chemicals are found everywhere, not only in the workplace but also in
    the general environment -- in the air, water and soil.  The heaviest
    exposures to some chemicals often occur during industrial or
    agricultural activities.  But significant exposure can also occur
    through contact with naturally occurring ores and the surrounding
    soil, from vehicle exhaust emissions, from building and insulating
    materials and from various foods. (Food itself may be contaminated or
    simply a medium for naturally occurring chemicals.)

    Chemicals are found everywhere in the environment; many different
    organisms are exposed to them -- whether they are plants exposed, for
    instance, to arsenic in the soil around arsenic mines or smelter
    wastes, microorganisms such as bacteria and fungi in soil, algae in
    water, or fish or birds exposed to pesticides.  Different species will
    respond in different ways, even to similar doses of the same chemical.

    What must be remembered, however, is that for a chemical to exert an
    effect, there must first be an exposure.  Not even the most toxic
    chemicals will cause harm to an organism, including humans, if there
    is no exposure.  The different ways in which humans can be exposed to
    chemicals are described below.  Environmental exposures and the
    effects of chemicals on the environment are discussed in Chapter 5,
    "How Chemicals Can Poison the Environment".

    There are four main exposure routes, or ways in which chemicals can
    enter the body (see Fig. 9):

    *    inhalation (breathing in);
    *    absorption (through the skin or eye);
    *    ingestion (through the digestive system by swallowing chemicals
         or eating contaminated food or drink); and
    *    transplacental transfer (across the placenta of the pregnant
         woman to the fetus).

    Most chemicals found in the workplace have the potential to be
    dispersed into the air as dust, in droplets (as mist, i.e. an
    aerosol) or as gas or vapour, and then inhaled.  People who handle
    chemicals directly are at risk of absorption via the skin or eyes. 
    Thus, the most important routes of exposure in the workplace leading
    to systemic effects are inhalation and skin absorption (see Fig. 10). 
    Everyone present in a workplace is also potentially at risk of
    exposure to chemicals through ingestion of contaminated food or drink. 
    Contaminated cigarettes are also a potential source of exposure via

    In addition, a fetus may be exposed through transplacental transfer of
    chemicals that are in the pregnant woman's bloodstream.

    In the case of each exposure route, chemicals can enter the
    bloodstream and thereafter be distributed to any or all of the organs
    and tissues of the body.  In this way, they can attack and harm organs
    that are distant from the original point of entry, as well as cause
    damage at the point of entry.

    Information on methods of preventing exposure to chemicals in the
    workplace and pollution of the environment is discussed in Chapters 3
    and 4.

    FIGURE 9


    Figure 10.  Occupational exposure
                (from HSG 19: Pentachlorophenol)

    Occupational exposure to technical PCP occurs mainly through
    inhalation and skin contact.  Virtually all workers exposed to
    airborne concentrations take up PCP via the lungs and the skin.  In
    addition, workers handling treated timber or maintaining PCP-
    contaminated equipment may be exposed to PCP in solution, and
    may absorb from one-half (based on urinary-PCP concentrations) to
    two-thirds (using serum levels) of their total PCP burden through
    the skin.

    2.1.1  Inhalation  Forms

    *    Gases and vapours -- Workplace chemicals can be emitted into the
         atmosphere in a number of different ways.  Evaporation is
         probably the most common.  Organic solvents, such as toluene,
         MEK (methylethylketone) or alcohols, generally evaporate more
         rapidly than water, acids or caustics.  Evaporation of a
         liquid produces vapours.  Vapours are formed from substances that
         exist as solids or liquids under normal temperature and pressure
         conditions. Substances that do not exist as solids or liquids at
         normal room temperatures and pressures are called gases.  Gases,
         as well as vapours, can contaminate the workplace air. 
         Chemicals with a high vapour pressure will generate more vapour
         than chemicals with a low vapour pressure. The amount of vapour
         released by a chemical also increases with increasing

    *    Mists and aerosols -- Some industrial processes produce tiny
         liquid droplets that are able to float in air.  Alternatively,
         mists sometimes form when a liquid breaks up, is splashed or is
         atomized. Examples include acid mists from electroplating, oil
         mists from cutting or grinding and paint spray mists from
         painting operations.

    *    Dusts, fumes and smoke -- Other workplace processes can generate
         tiny solid particles that are light enough to float in air; these
         are referred to as dusts, fumes or smoke.  Dusts are solid
         particles, often generated by some mechanical or abrasive
         activity.  They are usually of such a weight that they settle
         slowly to the ground.  Fumes are solid particles formed when a
         heated substance has evaporated in the air and then condensed
         back to a solid form (often after combining with oxygen in the
         air to form an oxide).  This often occurs during welding
         operations.  Fume particles are extremely small and may remain
         airborne indefinitely.  Smoke consists of carbon or soot and is

         formed during combustion.  Smoke particles can settle or remain
         airborne, depending on their size.  Entry into the body

    Contaminated air in the workplace is inhaled through the mouth and
    nose and then into the lungs (see Fig. 11).  An average person will
    breathe in and out about 12 times per minute.  Each inhalation brings
    about 500 ml of air into the lungs (corresponding to 6 litres of air
    per minute at rest), together with any contaminants that this air
    contains.  People undertaking hard physical work will breathe harder
    and take in more than 6 litres per minute.  Over an eight-hour working
    day, more than 2800 litres of air will pass through the lungs.  In
    conditions of hard physical work, up to 10 000 litres may be exchanged
    during the course of an eight-hour workshift.

    FIGURE 11

    Air breathed in through the nose is filtered by the nasal hairs;
    large, solid particles in the atmosphere are therefore prevented from
    passing any further into the body.  Small bones and cartilage inside
    the nose help the inhaled air to circulate.  Large contaminating
    particles may then be deposited in the nose, trapped by the moisture
    of the mucous lining (see below).

    Air inhaled through the nose and mouth reaches the back of the throat
    and enters the pharynx.  The pharynx, which is the entrance to the
    airways, divides into two tubes, one called the oesophagus, which
    carries food to the stomach, the other the trachea, which carries
    air to the lungs.  At the top of the trachea sits the larynx, where
    the vocal cords are situated.  Contaminated air passes into the
    trachea, which itself divides into two large tubes, each called a
    bronchus.  Each bronchus enters a lung.  Once inside the lung, each
    bronchus starts to divide like the branches of a tree -- the branches
    getting thinner and thinner as they spread.  Eventually, the tiniest
    tubes, which are called bronchioles, end in thin-walled air sacs,
    each of which is called an alveolus.  Collectively, they are called
    alveoli, and there are hundreds of thousands of these in each lung. 
    The walls of the alveoli are very thin and are richly supplied with
    tiny blood vessels (capillaries).

    The most important function of the lung is to bring oxygen into the
    body.  Oxygen in inhaled breath crosses the alveolar walls and enters
    the blood within the capillaries.  Once oxygen has become absorbed
    into the bloodstream, it is distributed throughout the body.  Chemical
    vapours, gases and mists that reach the alveoli in the lungs can also
    pass into the blood and therefore be distributed around the body.

    The airways contain a sticky, thick fluid called mucus.  Tiny hairs,
    known as cilia, on the inside of the tubes constantly carry the mucus
    upwards towards the back of the throat from which it is either
    expelled (spat out) through the mouth or swallowed and passed into the
    stomach.  Chemicals that are carried in air that has been inhaled can
    in this way enter the stomach.

    Solid particles that have reached the air sacs but which cannot pass
    through the thin wall of the sacs may become lodged there.  Some may
    dissolve, others may be attacked and destroyed by scavenger cells
    (macrophages) of the body's defence system.  Some particles that
    remain in the air sacs, if only in small quantities, do no apparent
    harm.  Other types of dust may damage the surrounding alveolar walls. 
    Such damage may be permanent and may result in the formation of scars,
    which eventually interfere with the lung's ability to expand and pass
    oxygen into the bloodstream.

    Some acids, caustics or organic chemicals, when inhaled in large
    amounts, can cause serious "burns" to the mouth, nose, trachea and

    Chemicals in the form of dust may settle on cigarettes or be
    transferred to them from the hands.  When a contaminated cigarette is
    smoked, toxic chemical fumes will be inhaled.  This may also occur if
    cigarettes are smoked in areas where chemical vapours or gases are
    present.  For these reasons, cigarettes should be stored outside the
    work area: no smoking should be allowed in a workplace where hazardous
    chemicals are used.

    2.1.2  Absorption through the skin  Forms

    Chemicals that pass through the skin are nearly always in liquid form. 
    Dusts, gases or vapours do not generally pass through the skin unless
    they are first dissolved in moisture on the skin's surface.  Chemicals
    that can dissolve easily in lipids (fats) will pass more readily
    through the skin.  The octanol/water partition coefficient (see
    Chapter 1 of this Manual) can be used as a measure of how
    lipid-soluble a chemical is.

    There are some chemicals, however, that can pass through the skin via
    other mechanisms.  Some highly toxic compounds such as sarin and
    parathion, for instance, penetrate the skin without causing overt
    damage.  Chemicals that cause local irritation or that are corrosive
    may be absorbed in greater quantity owing to increased blood flow to
    the skin or as a result of destruction of the outer skin barrier.  Entry into the body

    The skin consists essentially of two layers: a thin, outermost layer
    called the epidermis and a much thicker layer called the dermis (see
    Fig. 12).  The epidermis consists of several layers of flat, rather
    tightly packed cells, which form a barrier against infections, water
    and some chemicals.  This barrier is the external part of the
    epidermis.  It is called the keratin layer and is largely
    responsible for preventing water from escaping from the body.  It can
    also resist entry of water and weak acids but is much less resistant
    to organic and some inorganic chemicals.  The keratin layer contains
    fat and fat-like substances, which readily absorb chemicals that are
    solvents for fat, oil and grease.

    FIGURE 12

    Organic and caustic (alkaline) chemicals can soften the keratin cells
    and pass through this layer to the dermis, then enter the bloodstream. 
    Chemicals can also enter the body through cuts, punctures or scrapes
    of the skin, as these constitute breaks in the protective layer. 
    Contact with some chemicals such as detergents or organic solvents can
    cause dryness or cracking of the skin.  There can also be hives, or
    nettle-rash, ulcerations or skin flaking.  All these conditions weaken
    the protective layer of the skin, and chemicals are more likely to
    enter the bloodstream.

    Once in the bloodstream, the chemicals may be transported to any site
    or organ of the body, where they may exert their effects.

    Some chemicals are so corrosive that they may burn holes in the skin,
    through which infection or entry of other chemicals can occur.

    2.1.3  Absorption through the eye  Forms

    Any chemical, in the form of a liquid, dust, vapour, gas, aerosol or
    mist can enter the eye.  Entry into the body

    Eye splashes or eye contamination due to exposure to workplace
    chemicals is common.  Small amounts of chemicals can enter the eye by
    dissolving in the liquid surrounding the eye.  The eyes are richly
    supplied with blood vessels, and many chemicals can penetrate the
    outer tissues and pass into the veins.  The eye may be damaged during
    this process, depending on the corrosive nature of the chemical and
    its ability to penetrate the outer tissues.  For example, the organic
    solvent toluene can pass through the outer layers of the eye and
    probably enter the blood.  It can cause keratitis, which is an
    inflammation of the outer layer of the eye (see Fig. 13).  The
    majority of substances that become dissolved in tears are passed to
    the nose and eventually swallowed (see Fig. 14).  Only in very rare
    cases does absorption of chemicals through the eye cause acute
    systemic effects.

    2.1.4  Ingestion  Forms

    All forms of chemicals, whether they exist as liquids, solids, gases,
    vapours, mists, dusts, smoke or fumes, can -- directly or indirectly
    -- enter the digestive system.

    FIGURE 13

    FIGURE 14  Entry into the body

    Chemicals can enter the stomach following ingestion of contaminated
    food or mouth contact with contaminated cigarettes (see Fig. 15). 
    Food and drink can become contaminated when they are produced and also
    at the time of consumption by contact with unwashed hands, gloves or
    clothing, or if they are left exposed in the workplace.  Nail-biting
    is another potential source of ingested chemicals.  Some of the
    chemicals that are inhaled will be trapped in the mucus of the lungs,
    much of which will eventually be swallowed, thereby contributing to
    the total amount of the ingested chemicals.  In addition, chemicals in
    liquid form may enter the body by accidental ingestion.  For example,
    if a liquid is transferred to a bottle and not labelled adequately, a
    worker may mistake it for water or another beverage.

    FIGURE 15

    Once inside the mouth, chemicals pass down the oesophagus and into the
    stomach.  Food is digested with a strong acid produced by the stomach. 
    A few chemicals, such as alcohol, may pass across the stomach wall and
    enter the veins and bloodstream there.  But most chemicals move from
    the stomach into the small intestine.  The inside of the small
    intestine has hundreds of tiny finger-like projections called  villi
    that have very thin walls and are filled with tiny blood vessels. 
    This allows the digested food to pass from the small intestine across
    the walls of the villi and into the bloodstream.

    Some chemicals that contaminate food or drink can also pass across the
    thin walls of the villi and become absorbed into the bloodstream. 
    Other chemicals that are not soluble, or the basic units (molecules)
    of which are too big to pass across the villi walls, will stay in the
    gut and pass out through the faeces without being absorbed into the
    bloodstream to a great extent.  The absorption rate of a chemical
    indicates the percentage of the amount swallowed that becomes absorbed
    into the bloodstream.  Most chemicals are only partly absorbed.

    Some acids, caustics and organic chemicals may cause severe "burn"
    damage to the digestive system if ingested in high concentrations.

    2.2  Processing of chemicals in the body

    After a chemical enters the body, it undergoes one or more of three
    processes.  The chemical may be metabolized by the body, stored or
    accumulated in the body and/or excreted.

    2.2.1  Metabolism

    Metabolism is the process by which the body renders a 'foreign'
    chemical more easily excretable and less toxic. The body is full of
    special proteins called enzymes which initiate particular chemical
    reactions.  These reactions are necessary to, among other things,
    convert the food we eat into a form that can be used by the tissues
    and, combined with oxygen carried in the blood, to create heat and
    energy.  Some enzymes render foreign chemicals less toxic.  They do
    this by breaking down a chemical compound into simpler chemicals or by
    converting a foreign chemical into a form that the body can excrete
    more easily.  Once a foreign chemical has been metabolized, it becomes
    a different chemical, known as a metabolite.  The process of
    metabolism may involve many steps, and the result is many different

    Metabolism may occur anywhere or everywhere in the body, or in just
    one organ or type of tissue.  Generally, this process renders a
    chemical less toxic.  However, some metabolites are as toxic as or
    even more toxic than the original chemical.  Such metabolites are
    often called reactive metabolites.  For most chemicals, the liver is
    the main site of metabolism, but other organs such as the kidneys and
    testes are also capable of metabolizing chemicals, the products of
    which may be toxic.

    2.2.2  Excretion

    Excretion is the process by which unwanted chemicals are removed from
    the body.  Both foreign chemicals and those produced naturally by the
    body are excreted.  Most excretion occurs through the kidneys.  Some
    chemicals are excreted via the bile that passes from the liver into
    the intestines, after which the chemicals pass out of the body in the
    faeces.  Other chemicals are excreted as a gas that is exhaled from
    the lungs; small amounts may also be excreted in sweat.

    In the kidneys, blood (which may be carrying waste or foreign
    chemicals) is filtered through a set of small, twisting blood vessels
    called the glomeruli.  The fluid that is filtered off then passes
    through tiny tubes called tubules.  Here, water is reabsorbed and the
    level of various salts adjusted.  The combination of a glomerulus and
    a tubule is called a nephron.  There are hundreds of thousands of
    nephrons in each kidney.  The fluid that each nephron produces flows
    through more tubes (the collecting ducts and the ureters) into the
    bladder, from which urine is expelled from the body (see Fig. 16).

    For some chemicals, it is possible to calculate the amount absorbed by
    testing a urine sample.  The concentration of the original chemical or
    the concentration of a metabolite in the urine can also be determined. 
    Urine tests are often useful for determining whether absorption of a
    chemical has occurred.  For some chemicals, such as alcohol, exhaled
    air can be used as an indication of absorption.  Testing of urine,
    blood or other body fluids to determine absorption is discussed
    further in Chapter 3 of this Manual.

    FIGURE 16

    2.2.3  Storage or accumulation

    Chemicals that undergo a slow metabolism or excretion are often stored
    in various tissues of the body.  Sustained exposure may thus increase
    the amount of the chemical in tissues.  Chemicals that are stored in
    this way are said to accumulate.

    The time taken for half of the total amount of chemical in the body to
    be metabolized or excreted is called the half-time (or half-life)
    of the chemical.  If a chemical has a short half-time, it is
    metabolized or excreted quickly by the body. Some chemicals, such as
    cadmium, have a very long half-time of 15"20 years.  The half-time of
    a chemical varies from person to person, and this will influence how
    sensitive an individual is to a chemical.  An individual with a long
    half-time will accumulate more of the chemical in his or her body. 
    The average half-time is sometimes given in information about
    chemicals that are stored or that accumulate in the body.

    2.3  Toxic effects of chemicals

    The toxic effects, or toxicity, of a chemical can be defined as the
    potential of that chemical to poison the body -- of the person
    exposed, of an unborn baby (if the exposed person is pregnant), of a
    future offspring of the exposed person or even of an offspring of the
    exposed person's offspring.

    The potential that a chemical substance has for causing negative
    health effects depends principally on the toxicity of the chemical and
    the degree of exposure.  The toxicity is a property of the chemical
    itself, while the exposure depends on how the chemical is used, for
    example whether it is heated, sprayed or otherwise released into the
    workplace environment.  Another important concept in evaluating harm,
    however, is the individual susceptibility of exposed persons.  There
    can be marked differences in reactions between workers who are exposed
    to the same chemical, at the same worksite and in similar
    concentrations.  This may be due, for example, to gender (women, with
    a greater relative proportion of body fat, may be more susceptible
    than men to the harmful effects of solvents, for instance), age
    (children and the elderly are generally more susceptible to chemical
    hazards) or race (certain races may be genetically more vulnerable to
    certain chemical exposures).  Nutritional status may also have a
    considerable effect on the action of some compounds.

    Several concepts have been developed to help classify the toxic
    effects of chemicals.  These include:

    *    Acute effect -- The term acute means "of rapid onset and short
         duration" and, with reference to chemicals, usually means a short
         exposure with an immediate effect (see Fig. 17).  While an acute
         exposure can result in an acute effect, it can also result in a
         chronic disease, e.g. permanent brain damage can result from
         acute exposure to trialkyl tin compounds or from severe carbon
         monoxide poisoning.

    FIGURE 17

    *    Chronic effect -- The term chronic means "of slow onset and long
         duration" and usually refers to repeated exposure with a long
         delay between the first exposure and the appearance of adverse
         health effects (see Fig. 18).  The delay between the time of
         exposure and the onset of the health effect is called the
         latency period.

    *    Acute and chronic effects -- A substance may have both an acute
         and a chronic effect.  For example, a single exposure to high
         levels of carbon disulfide can result in unconsciousness (acute
         effect), but repeated daily exposure for years at much lower
         concentrations may result in damage to the central and peripheral
         nervous system, as well as to the heart, i.e. at concentrations
         that if experienced as a single exposure would not lead to
         adverse effects (chronic effects).

    FIGURE 18

    *    Reversible (temporary) effect -- An effect that disappears if
         exposure to that chemical ceases.  Contact dermatitis, headaches
         and nausea from exposure to solvents are examples of reversible

    *    Irreversible (permanent) effect -- An effect that will have a
         lasting, damaging effect on the body, even if exposure to the
         chemical causing that effect ceases.  Cancer caused by exposure
         to a chemical is an example of an irreversible effect.

    *    Local effect -- The harmful effect of a chemical at the point of
         contact or entry to the body, e.g. burns to the skin.

    *    Systemic effect -- The effect of a chemical on the organs and
         fluids of the body after absorption and transport from the point
         of entry.  Anaemia (a deficiency of haemoglobin due to a lack
         of red blood cells) is a typical systemic effect.  It can be
         caused by a number of chemicals, including lead, beryllium,
         benzene, cadmium and mercury compounds.

    *    Synergism -- The combined effect of exposure to more than one
         chemical at one time, or to a chemical in combination with other
         hazards such as heat, noise or radiation.  The resultant health
         effects of such exposure may be greater than the sum of the
         individual effects of each hazard by itself.  A mixture of sulfur
         dioxide and sulfur trioxide, for example, has been shown to have
         more severe effects on the functioning of respiratory passages
         than the mathematical sum of their individual effects on the
         respiratory system would suggest.

    The toxic effects (or the toxicity) of a chemical can be classified in
    the following ways:

    *    Corrosive -- A chemical that destroys or damages (burns) living
         tissue on contact (see Fig. 19).  For example, concentrated
         solutions of strong acids such as sulfuric acid, or alkalis such
         as caustic soda, cause chemical burns.  A splash of a corrosive
         liquid in the eye can result in permanent damage to eyesight.

    *    Irritant -- A chemical that will produce local irritation or
         inflammation of the skin, eyes, nose or lung tissue.

    *    Sensitizer -- A chemical that causes an allergic reaction.  A
         person who is sensitized to a chemical will experience a
         heightened reaction to it, whereas for the majority of
         individuals the chemical will not be harmful at the same,
         sometimes very low, dose.  For a sensitized person, any
         subsequent exposure -- whether through skin contact or by
         inhalation -- will represent a health risk.

    FIGURE 19

    *    Asphyxiant -- A chemical that interferes with the oxygenation of
         the body tissues.  There are two types of asphyxiation: simple
         asphyxiation, whereby oxygen in the air is replaced by a gas to
         a level at which it cannot sustain life; and chemical
         asphyxiation, whereby a direct chemical action interferes with
         the body's ability to transport and use oxygen.  Examples of
         chemical asphyxiants include carbon monoxide and cyanides.

    *    Carcinogen -- A chemical that causes cancer. Cancer is a group of
         diseases characterized by the manner in which abnormal cells in
         the body multiply and spread out of control.  The key feature of
         cancer is the "malignant" or deadly way that its cells crowd out
         other cells and interfere with the normal functioning of the body
         (see Fig. 20).

    *    Mutagen -- A chemical that can cause permanent damage to the
         deoxyribonucleic acid (DNA) in a cell (see Fig. 21).  DNA is
         a molecule that carries the genetic information controlling the
         growth and function of cells.  DNA damage in the human egg or
         sperm may lead to reduced fertility, spontaneous abortion
         (miscarriage), birth defects and heritable diseases.  Thus, any
         chemical known to be a mutagen must be treated with caution.


    Figure 20.  Carcinogenic effect (from HSG 19: Pentachlorophenol)

    The results of animal studies, designed to assess the carcinogenicity
    of PCP and reported to date, have been negative.  Carcinogenicity
    bioassays with one other chlorophenol (2,4,6-T3CP) and a mixture of
    two H6CDD congeners found in PCP have been positive.  Hence, the
    carcinogenic effects of long-term exposure of animals to technical PCP
    are not clear.


    Figure 21.  Mutagenic effect (from HSG 32: d-Phenothrin)

    d-Phenothrin is not mutagenic in a variety of  in vivo and  in vitro
    test systems that studied gene mutations, DNA damage, DNA repair, and
    chromosomal effects.

    *    Teratogen -- A chemical that, if present in the bloodstream of a
         pregnant woman, crosses the placenta, affecting the developing
         fetus and resulting in structural or functional congenital
         abnormalities, or cancer, in the child.  These effects may not be
         observable until the child becomes an adult.  One of the
         better-known examples of a teratogen is Thalidomide, which, in
         the 1960s, caused many cases of phocomelia (a reduction of the
         limbs to the extent that the hands and feet are attached directly
         to the body) in babies born to women who took the drug during the
         early stages of pregnancy. Several industrial chemicals have been
         shown to be experimental teratogens; some, such as ethylene
         dichloride and vinyl chloride, have been shown to be teratogenic
         in humans.

    *    Fetotoxicant -- A chemical that adversely affects the developing
         fetus, resulting in low birth weight, symptoms of poisoning at
         birth or stillbirth -- i.e. the fetus dies before it is born (see
         also Fig. 22).


    Figure 22.  Fetotoxic effect (from HSG 19: Pentachlorophenol)

    PCP is fetotoxic, delaying the development of rat embryos and
    reducing litter size, neonatal body weight, neonatal survival,
    and the growth of weanlings.  The no-observed-adverse-effect
    level for technical PCP is a maternal dose of 5 mg/kg body
    weight per day during organogenesis.  In one study, it was
    reported that purified PCP was slightly more embryo/fetotoxic
    than technical PCP, presumably because contaminants induced
    enzymes that detoxified the parent compound.

    2.4  Effects on body systems

    Chemicals may have toxic effects on all cells in the body, or they may
    affect only particular organs or body systems. Organs that are
    especially sensitive to the toxic effects of a particular chemical are
    known as target organs.  A toxic action on one particular organ or
    body system may be attributable to a particular property of the
    chemical or related to the way in which a chemical enters or
    circulates within the body.  Toxic effects of chemicals on particular
    organs and body systems include those on the:

    *    Lungs and the respiratory system.  Short-term effects are caused
         mainly by irritation (producing bronchitis or pneumonitis)
         and chemical burns.  Serious chemical burns inside the lungs can
         result in the lungs becoming filled with fluid (pulmonary oedema)
         and can be fatal.  Some chemicals can sensitize or cause an
         allergic reaction in the airways, leading to wheezing and
         shortness of breath (asthma) (see Fig. 23).

         Long-term (chronic) conditions include scarring of the lung
         tissue following exposure to chemical dusts (fibrosis or


    Figure 23.  Effects on the respiratory system
                (from HSG 35: Phosphorus Trichloride)

    Depending on their concentration, the vapours can be irritating or
    corrosive, but they may be less irritating than their hydrolysis
    products.  However, exposure to the vapours can cause necrosis of the
    tissues of the respiratory tract.  The vapours can be deeply inhaled
    and may reach the lower airways where they hydrolyse to produce
    hydrogen chloride and phosphorous or phosphoric acid.

    Irritation of the airways causes swelling and bronchospasm resulting
    in tightness of the chest, wheezing and difficulty in breathing. 
    Reactive secretion of mucus causes a cough with sputum and possible
    bronchial obstruction and local lung collapse.

    *    Liver.  Chemicals that can affect the liver are called
         hepatotoxins.  Most chemicals are metabolized in the liver, and
         many therefore have the potential to damage the liver cells. 
         Possible short-term effects of chemicals on the liver include
         inflammation of the liver cells (chemical hepatitis), necrosis
         (cell death) and jaundice.  Long-term effects include cirrhosis
         (scarring) of the liver and liver cancer.

    *    Kidneys and urinary tract.  Chemicals that can affect the kidneys
         are called nephrotoxins.  The effects of chemicals on the kidneys
         include sudden failure of the kidneys (acute renal failure),
         chronic renal failure and kidney or bladder cancer.

    *    Nervous system.  Chemicals that affect the nerves are called
         neurotoxins.  Exposure to certain chemicals may cause a slowing
         down of the function of the brain.  Symptoms include sleepiness
         and loss of alertness, followed by loss of consciousness (see
         Fig. 24).  Some of these effects are called "narcotic" effects,
         based on the Greek word  "narkos" meaning "sleep".  Some illegal
         drugs have narcotic effects and are therefore called narcotics. 
         Another term for these "sleep effects" is central nervous system
         depression (not to be confused with depression as a mental health
         problem). Other chemicals, particularly pesticides, can poison an
         enzyme in the nerves going to the muscles, causing muscle
         twitching and paralysis.  Yet another group of chemicals may
         slowly poison the nerves to the hands and feet, resulting in loss
         of feeling and weakness.


    Figure 24.  Effects on the nervous system
                (from HSG 3: 1-Butanol)

    Ingestion of the liquid or inhalation of the vapour may result in
    headache, drowsiness, and narcosis.  The occurrence of vertigo under
    conditions of severe and prolonged exposure to vapour mixtures of
    1-butanol and isobutanol has been reported.  From this study, it is
    not possible to attribute the vertigo to a single cause.  Symptoms are
    reversible when exposure ceases.

    *    Blood and bone marrow.  Some chemicals, such as arsine, damage
         the red blood cells, causing haemolytic anaemia.  Other chemicals
         can damage the bone marrow and other organs where blood cells are
         formed or can cause cancer of the blood-forming cells (e.g.
         benzene causes leukaemia).

    *    Heart and blood vessels (cardiovascular system). Some solvents
         (such as trichloroethylene) and gases can cause fatal
         disturbances of the heart rhythm.  Others, such as carbon
         disulfide, may cause an increase in blood vessel disease, which
         may lead to a heart attack.

    *    Skin.  Many chemicals irritate the skin, causing "irritant
         contact dermatitis", or they may sensitize the skin, causing
         "allergic contact dermatitis".  A rash results in both cases. 
         This rash may be very severe, widespread and disabling.  Other
         chemicals may cause acne (chloracne), loss of pigmentation
         (vitiligo), increased sensitivity to sunlight
         (photosensitization) or skin cancer.

    *    Reproductive system. Many chemicals are teratogens and
         experimental germ cell mutagens.  In addition, some chemicals can
         directly affect the ovaries and testes, resulting in disruption
         of menstruation and sexual function.  Such chemicals are called

    *    Other systems.  Chemicals can also affect the immune system,
         bones, muscles and particular glands, such as the thyroid gland.

    2.5  Dose, effects and response

    Increasing levels of exposure to or dose of a chemical will generally
    lead to more severe effects. For instance, higher concentrations of
    carbon monoxide in the air will progressively reduce the capacity of
    an exposed person's blood to carry oxygen.  The resultant lack of
    oxygen in the blood leads initially to headaches.  As the oxygen
    levels decline further, the symptoms worsen: nausea, unconsciousness
    and eventually death occur.  This progression in severity of effect as
    the dose increases is called the "dose-effect relationship".

    In the case of a population or group of workers, increasing exposure
    levels will also lead to an increasing proportion of the group
    manifesting a specific effect.  For example, increasing exposure to
    benzidine dyes will result in a higher incidence of bladder cancers
    among the exposed population.  Similarly, increasing exposure to lead
    will be reflected in a greater proportion of workers who undergo blood
    changes (FEP, ALAD, etc.; see Fig. 25).  This frequency of affected
    people in an exposed population is called "the response".  The
    increase in response with increasing exposure level or dose is known
    as the "dose"response relationship".

    Another important concept is "threshold dose" or the
    "no-observed-effect-level" (NOEL).  This means that at low levels
    of exposure to a chemical, the severity of the effect and the response
    decrease, and that at a certain point there is no effect on health. 
    Usually this level is determined by exposing animals to lower and
    lower concentrations of a chemical until a level is found at which no
    effect on the animals is observed.  It is impossible, however, to
    examine every aspect of a test animal, and therefore effects may be
    missed. Also, unless lifetime tests are performed (and they are not in
    every case), long-term or chronic effects may also be missed, even
    though subacute effects are noted.  In addition, only limited numbers
    of animals can be studied, whereas in real life many thousands of
    people may be exposed to a chemical, some of whom will be much more
    sensitive to its health effects than the majority.  Even a very low
    dose of a cancer-causing substance may increase the risk of cancer. 
    Studies of workers do not usually look at a sufficiently large group
    to prove that exposure to low doses does, or does not, increase cancer

    FIGURE 25

    When drawing up regulations for the permissible (although not
    necessarily safe) levels of chemicals in food, drinking-water and the
    environment, government bodies usually divide the NOEL from animal
    studies by a safety factor of 100 or 1000 (see Fig. 26).  Occupational
    exposure limits are usually set with a safety factor of 2-10 at the
    most and even sometimes with no safety factor.

    2.6  How is the toxicity of a chemical determined?

    Knowledge of the toxicity of chemicals is gathered by studying the
    effects of:

    *    exposure to the chemical in experimental animals, lower organisms
         -- such as bacteria -- and laboratory cultures of cells from
         mammals; and

    *    exposure of people to the chemical.


    Figure 26.  Use of safety factors (from HSG 19: Pentachlorophenol)

    The US National Academy of Sciences (1977) calculated an acceptable
    daily intake (ADI) for PCP of 3 g/kg body weight per day.  This ADI
    is based on data from a feeding study on rats and a 1000-fold safety
    factor.  The results of long-term studies indicate that the
    no-observed-adverse-effect level for rats is below 3 mg/kg body weight
    per day.  A recent human study has shown that the steady-state body
    burden is 10-20 times higher than the value extrapolated from rat
    pharmacokinetic data, suggesting that caution should be applied when
    extrapolating directly from the rat model to humans. Furthermore, the
    ADI in the USA was not based on an inhalation study, and does not
    account for the possibly greater toxicity of PCP via inhalation, as
    indicated by animal studies.  Hence, the safety factor of 1000 used to
    derive this ADI value is by no means too conservative.  The intake for
    a 60 kg adult exposed to concentrations of PCP at the ADI level would
    be 180 g/person per day.

    2.6.1  Animal studies  Acute toxicity tests

    *    LD50 and LC50 tests

    The standard test for acute (short-term) toxicity is to feed animals
    increasing amounts of a chemical over a period of 14 days until the
    animals start to die.  Alternatively, the chemicals can be applied to
    the animals' skin until a reaction is observed.  The amount of the
    chemical that kills 50% of the exposed animals is called the lethal
    dose for 50%, or the LD50.  The LD50 may be "oral" or "dermal",
    depending on the method of exposure (see Fig. 27).  Lethal doses with
    respect to inhalation of chemicals in the form of a gas or aerosol can
    also be tested.  In this case, the concentration of gas or vapour that
    kills half the animals is known as the lethal concentration for 50%,
    or the LC50.


    Figure 27.  Effects on animals (from HSG 3: 1-Butanol)

    The oral LD50 values for 1-butanol for the rat range from 0.7 to
    2.1 g/kg body weight.  Therefore, it is slightly toxic according to
    the classification of Hodge & Sterner.  It is markedly irritating to
    the eyes and moderately irritating to the skin.  The primary effects
    from exposure to vapour for short periods are irritation of mucous
    membranes, and central nervous system depression.  The potency of
    1-butanol for intoxication is approximately 6 times that of ethanol. 
    A number of investigations have shown non-specific membrane effects of
    1-butanol.  Effects of repeated inhalation exposure in animals include
    pathological changes in the lungs, degenerative lesions in the liver
    and kidneys, and narcosis.  However, it is not possible to determine a
    no-observed-adverse-effect level from the animal studies available. 
    1-Butanol has been found to be non-mutagenic.  Adequate data are not
    available on carcinogenicity, teratogenicity, or effects on

    The LD50 and the LC50 are very widely used as indices of toxicity. 
    The following criteria are often used for purposes of classification
    of acute toxic effects in animals (see Table 2):

    Table 2.  Classification of acute toxicity in animals


                 Oral LD50      Dermal LD50      Inhalation LC50
                    rat        rat or rabbit           rat
                  (mg/kg)         (mg/kg)          (mg/m3/4 h)

    Harmful      200-2000        400-2000           2000-20 000

    Toxic         25-200          50-400             500-2000

    Very toxic     < 25            < 50               < 500

    The scale of Hodge & Sterner is also often used, in this case to
    classify the acute toxicity of chemicals to humans (see Table 3):

    Table 3.  Classification of acute toxicity in humans

    Toxicity rating            Dosage         Probable lethal
                                              dose for average
                                              human adult

    1.  Practically non-toxic  > 15 g/kg      > 1 litre

    2.  Slightly toxic         5-15 g/kg      0.5-1 litre

    3.  Moderately toxic       0.5-5 g/kg     30-500 ml

    4.  Very toxic             50-500 mg/kg   3-30 ml

    5.  Extremely toxic        5-50 mg/kg     7 drops-3 ml

    6.  Supertoxic             < 5 mg/kg      A taste (< 7 drops)

    It is impossible to assess the health risk posed by a chemical on the
    basis of its LD50 or LC50 alone.  Moreover, the LD50 and LC50
    give no information about the mechanism or type of toxicity of a
    chemical, or its possible long-term or chronic effects.

    Thus, the LD50 and LC50 are very crude indices of toxicity.

    *    The fixed-dose procedure

    Many national and international bodies are now trying to modify or
    replace the LD50 and LC50 tests by simpler methods, e.g. a
    fixed-dose procedure that uses fewer animals.  The fixed-dose
    procedure requires only a small number of animals, and analysts can
    evaluate a chemical's toxicity without the animals having to die as an
    end-point.  The idea is to examine how a set dose of a chemical
    affects a group of animals, the dose being based on what is already
    known about the physical and chemical properties of the substance
    being evaluated.

    *    Irritation and corrosion tests

    Irritation and corrosion tests provide some specific information.  The
    chemical being tested is applied to the test animal's skin, and the
    area is examined over the next few days for signs of a rash or flared
    response.  Tests can also be carried out on the animal's eyes (this is
    known as the "Draize" test).  Subchronic toxicity tests

    Subchronic toxicity tests are normally 90-day inhalation or ingestion
    studies to check for specific and obvious effects of the chemical on
    the organs and biochemistry of the animal subjects.  These types of
    tests involve repeated exposure to the chemical being tested and are
    primarily directed at detecting toxic effects that are not evident
    from acute exposure.  Crude studies simply call for examination of the
    organs for gross abnormalities apparent to the naked eye; more
    sophisticated studies involve taking tissue slices and examining them
    under a microscope to check for abnormalities of the cells in the
    organs.  Most studies involve taking regular samples of blood or urine
    from the animals for examination and analysis. These tests form the
    basis for doses used in chronic bioassays (see next section).  Chronic (lifetime) bioassays

    The purpose of lifetime or chronic bioassays is to determine whether
    chemicals lead to any health effects that may take a long time to
    develop, such as cancer, or whether long-term exposure to chemicals
    leads to health effects on organs such as the kidneys (see Fig. 28).


    Figure 28.  Chronic bioassays (from HSG 34: Fenvalerate)

    In a long-term toxicity study, microgranulomatous changes were also
    observed in rats at 500 mg/kg in the diet.  The NOEL for these
    microgranulomatous changes was 150 mg/kg in the diet.

    Fenvalerate, when fed at dietary levels up to 3000 mg/kg for 78 weeks
    and 1250 mg/kg for 2 years, was not carcinogenic to mice.  Nor was it
    carcinogenic to rats when fed at dietary levels up to 1000 mg/kg for
    2 years.

    These studies are performed by exposing animals, by ingestion or
    inhalation, to the chemical being tested, for most or all of the
    animals' lifetime.  In rats, this may be two years; in mice, a little
    less.  In a typical test, 50 mice or rats of each sex are exposed to a
    high, but non-lethal, dose of the chemical under study. The test
    animals are compared throughout their lifetime with a similar number
    of "control" animals, which are similar in all respects except that
    they are not exposed to the chemical.  A good study exposes different
    groups of animals of both sexes to different doses of the chemical. 
    Up to 500 animals may be used in a study of the chemical.  Short-term mutagenicity tests

    Bacteria and animal cells grown in test-tubes and colonies of fruit
    flies or other insects are convenient for the rapid and cheap
    investigation of the potentially carcinogenic and mutagenic effects of
    chemicals.  The best-known and most widely used of these tests is the
     Salmonella mutagenicity test (commonly known as the Ames test). 
    This involves growing special bacteria in the laboratory and exposing
    them to the chemical in question.  The test detects mutations in the
    bacteria, i.e. it is a test for mutagenic effects.  There are a number
    of other short-term mutagenic tests or "mutagenicity assays", as they
    are often called.  These tests are often referred to as being  in
     vitro.  They are thus distinguished from  in vivo tests, which use
    living tissue such as animals and humans (see Fig. 29).

    Many, but not all, chemicals that cause cancer in animals and may
    cause cancer in humans are mutagenic.


    Figure 29.  Short-term mutagenicity tests
                (from HSG 34: Fenvalerate)

    Fenvalerate did not show any mutagenic or chromosome-damaging
    activities in several  in vitro and  in vivo assays.
                                                                       Reproductive studies

    Animal studies to check for the adverse effects of a chemical on
    reproduction involve exposing one or both parents to the chemical
    being tested, prior to mating, and then observing the effects on any
    offspring.  Sometimes only a pregnant animal is exposed.  Reproductive
    effects are classified according to whether the offspring are fewer in
    number, lower in birth weight deformed or damaged in some way. 
    Multigeneration studies are sometimes necessary to detect effects that
    may be passed on to future generations (see Fig. 30).  Behavioural tests

    The effects of chemicals on the behaviour of test animals and on their
    ability to learn (e.g. to find their way out of a maze) will often
    indicate subtle effects of a chemical on the brain and nervous system
    that are missed by other tests.  Behavioural tests have been used to
    show the effects of exposure to compounds such as organic solvents and


    Figure 30.  Reproductive effects (from HSG 34: Fenvalerate)

    Fenvalerate is not teratogenic to mice or rabbits at doses up to
    50 mg/kg body weight per day.  It did not show any toxic effects on
    reproductive parameters in a three-generation rat reproduction study
    at doses up to 250 mg/kg diet.

    2.6.2  Human evidence  Case reports

    Case reports are accounts, usually by occupational health physicians,
    of small numbers of workers or individual workers whose disease
    appears to be attributable to workplace exposure.  Often the part of a
    process at which the chemical may have caused the problem is known,
    but not the precise degree of exposure.  Much information about
    occupational health hazards has initially been found following
    examination of case reports.  Epidemiological studies

    Epidemiological studies investigate the health of a group of people to
    establish whether they are affected by the chemical to which they are
    exposed at work or in the general environment.  These studies involve
    comparing the disease outcome of an exposed group of people over time
    with that of unexposed persons.  Two of the more common methods of
    investigation in epidemiology are case-control studies and cohort

    Case-control studies are relatively simple to carry out and
    increasingly used to investigate the cause of diseases - especially
    rare diseases.  They basically compare people with the disease, or
    other outcome, under study with a suitable control group unaffected by
    the disease or outcome in an attempt to identify the cause.

    Cohort studies, also called follow-up or incidence studies, look
    at a group of people (a cohort) who are classified into subgroups
    according to exposure to a potential cause of disease or outcome. 
    Differences in exposure (to chemicals, for instance) are examined and
    measured and the whole cohort followed up to see how the subsequent
    development of the disease, or outcome, differs between the exposed
    and unexposed groups (see Fig. 31).

    FIGURE 31

    Although epidemiological investigations provide the most dependable
    proof that a given chemical has an adverse effect on the health of a
    population, they do have several disadvantages.  Only a small group of
    chemicals in use has been studied in this way because of the expense
    involved and the need for good exposure records and a sufficiently
    large number of exposed workers to ensure the validity of the
    statistical calculations.  New chemicals, of course, cannot be studied
    in this manner as there will be no history of exposure.  In addition,
    epidemiological studies may not be able to detect rare events or
    pinpoint the role of one particular chemical when workers are exposed
    to mixtures of chemicals.  But, above all, waiting for the results of
    such studies can mean many unnecessary and largely preventable deaths
    and illnesses among exposed persons. If information from epidemio-
    logical studies is lacking, preventive action should be instigated
    based on animal studies (see Fig. 32).


    Figure 32.  Human studies (from HSG 19: Pentachlorophenol)

    Past use of PCP has affected workers producing or using this chemical. 
    Chloracne, skin irritation and rashes, respiratory disorder,
    neurological changes, headaches, nausea, weakness, irritability, and
    drowsiness have been documented in exposed workers.

    Investigations of biochemical changes in woodworkers with long-term
    exposure to PCP have failed to detect consistently significant effects
    on major organs, nerves, blood, reproduction, or the immune system. 
    However, the statistical power of these studies has been limited as a
    result of the small sample sizes used.  Overall, the body of research
    suggests that long-term exposure to levels of PCP encountered in the
    workplace is likely to cause borderline effects on some organ systems
    and biochemical processes.

    Some epidemiological studies from Sweden and the USA have revealed an
    association between exposure to mixtures of chlorophenols, especially
    2,4,5-T3CP, and the incidences of soft-tissue sarcomas, lymphomas, and
    nasal and nasopharyngeal cancers.  Other studies have failed to detect
    such a relationship. It was not possible to address the effects of
    exposure to PCP itself in any of these studies.

    The theory behind animal tests is that humans and animals such as
    rats, mice or dogs share the same basic biochemistry and bodily
    processes.  Although there are differences between animals and humans,
    the similarities in terms of the way chemicals act on the body are far
    greater.  Animal tests make it possible to test the toxicity of a
    chemical before people are exposed to it.  Such results should be used
    in health and safety guidelines.  This should reduce the occurrence of
    unwanted effects of chemicals on human health.  Exposing workers or
    the general community to a chemical and waiting for human
    epidemiological data to appear before warning workers and acting to
    protect the general community are now unacceptable.  On the other
    hand, epidemiological studies will always be essential to monitor the
    health of people exposed to chemicals that are already in use and to
    check that preventive measures are effective.

    2.6.3  Environmental assays

    These tests attempt to predict whether a chemical will have unwanted
    effects on animals and plants in the environment and whether chemicals
    are likely to be present in water supplies and food.

    2.7  Assessing hazards, risks and safety

    In a general sense, the toxicity of a substance can be defined as the
    substance's capacity to harm a living organism.  A highly toxic
    substance will harm an organism even if only very small amounts are
    present in the body.  Conversely, a substance of low toxicity will not
    produce an effect unless the amount present in the body is very large. 
    The main factors that must be considered when assessing the toxicity
    of a substance include:

    *    the quantity of the substance absorbed (the dose) by the person
         exposed to that chemical;

    *    the route via which exposure to the chemical occurs (e.g.
         inhalation, ingestion, or absorption through the skin);

    *    the duration of exposure to the chemical and how often that
         exposure occurs;

    *    the type and severity of the injury caused by exposure to the
         chemical; and

    *    whether or not that injury is permanent or reversible, e.g.
         cancer is irreversible, although sometimes treatable.

    Three other terms are commonly used when the toxicity of a chemical is
    discussed: hazard, risk and safety.

    2.7.1  Hazard

    A hazard can be defined as the set of inherent properties of a
    chemical, mixture of chemicals or a process that, under production,
    usage or disposal conditions, has the potential to adversely affect
    the environment or the organisms it contains.  In other words, it is a
    source of danger.

    2.7.2  Risk

    It is important to distinguish risk from hazard.  Hazard refers to the
    intrinsic properties of a chemical, whereas risk refers to the chance
    or probability that the chemical will cause an adverse health effect. 
    If there is a high risk that a certain chemical will cause cancer in
    exposed workers, then it is very likely that some of those workers
    will develop cancer.  If the risk is low, then it is less likely that
    the workers will develop cancer.  However, even if the risk of some
    health effect is low, the chemical in question is still a hazard.
    Depending on the circumstances, a "low risk" may be acceptable to the
    people exposed.  Determining the "acceptable risk" is part of the
    process for setting safety standards.

    *    Risk assessment involves identification of the hazard
         (the chemical of concern, for instance, and its adverse effects,
         target populations and conditions of exposure); characterizing
         the risk; assessing exposure (by measuring and monitoring); and
         estimating the risk.  Thus, it consists of identification and
         quantification of the risk resulting from a specific use or
         occurrence of a chemical, taking into account the possible
         harmful effects on individuals of using the chemical in the
         manner and amount proposed, and all possible routes of exposure.

    *    Risk management covers the whole range of actions taken to
         prevent, minimize or otherwise control specific risks posed by a
         certain chemical or situation.  It is based on concepts of safety
         and therefore contains elements of policy relating to political,
         social and economic factors, as well as engineering and process

    2.7.3  Safety

    Safety is even more difficult to define than risk or hazard.  The
    safety of a chemical, in the context of human health, is the extent to
    which a chemical may be used in the amount necessary for the intended
    purpose, with a minimum risk of adverse health effects.  It can also
    be defined as a "socially acceptable" level of risk.  But it is
    usually unclear which part of society is judging the risk.  Workers
    that are exposed to the risk are likely to be more concerned about the
    safety of a chemical than others.  Therefore, it is very important to
    question statements such as "this chemical is safe" or "there is a
    high level of safety when using this chemical".  Safety is a
    subjective concept.


    This chapter corresponds to Chapter 3 of each HSG (Conclusions and
    recommendations), which evaluates the degree of hazard of a chemical
    and recommends control measures to limit exposure (see Fig. 33).


    Figure 33.  Conclusions and recommendations
                (from HSG 35: Phosphorus Trichloride)

    3.1  Conclusions

    Phosphorus trichloride and phosphorus oxychloride are highly reactive
    and hazardous corrosive chemicals.  Intense exposure to their vapours
    may leave a residual restrictive defect in the lungs.  Repeated minor
    overexposures may result in progressive impairment of lung function
    and can be fatal.  Apart from spillages that destroy plant and animal
    life in the immediate area, the impact of these chemicals on the
    environment is negligible.

    3.2  Recommendations

    Phosphorus trichloride and phosphorus oxychloride should only be used
    and handled under the careful supervision of managers who fully
    understand the hazards and the good handling and manufacturing
    practices necessary to control them.  These managers should train
    operators, maintenance personnel and contractors about the hazards and
    safety procedures.

    There are four steps in the prevention and control of workplace
    chemical hazards:

    *    identification of the hazard;

    *    evaluation of the hazard and risk;

    *    organization to prevent, control or eliminate the risk; and

    *    controlling the hazard through specific actions.

    FIGURE 34

    3.1  Identification

    All workers have the right to know the possible effects of their work
    on their health and safety.  This includes the right of access to
    information about the health effects of chemicals, other substances
    and work processes and about procedures for healthy and safe systems
    of work.

    In some countries, the right to know this information is backed up by
    special laws.  Under these laws, employers and manufacturers,
    suppliers and importers of chemicals must provide clear, detailed
    information about the particular chemical, substance or product, its
    possible health effects, including the results of animal tests and
    surveys of exposed workers (see Chapter 2), and means of protecting
    workers from any harmful effects.

    These legal rights may apply to each worker or to elected health and
    safety representatives or committees.  Find out from your employer,
    trade union or government occupational health agency if you are
    covered by such a law.

    3.2  Evaluation

    If "right-to-know" laws operate, employers, manufacturers and
    suppliers of chemical products are required to:

    *    produce Material Safety Data Sheets (MSDSs) for all chemicals
         used in the workplace;

    *    label chemical products clearly to indicate their (potentially)
         harmful effects, and provide guidance on how to use the products
         as safely as possible; and

    *    instruct workers in the meaning of labels and MSDSs.

    Development of a workplace chemical register is one means of
    evaluating hazards.  This is simply a list of every chemical used in
    the workplace.  An MSDS should be available for every chemical on the

    Workers should have the right to refuse to work with chemicals for
    which full health and safety information is not available.  If you
    experience difficulty obtaining full information from your employer,
    contact your government health or labour ministry, trade union or a
    workers' health or environmental organization for help.

    Most HSGs available from the IPCS also contain an ICSC or Summary of
    Chemical Safety Information for the chemical concerned.  Each ICSC is
    a brief, internationally reviewed summary of the properties, hazards,
    preventive methods and emergency treatment relating to the chemical in

    Workers' representatives should be given the opportunity to review
    complete health and safety information  before any new chemical is
    introduced into the workplace.  Arrangements for the safe use of new
    chemicals should be finalized and put into practice before a chemical
    is introduced.

    3.3  Safety organization

    All workplaces should implement effective safety procedures for
    protection against chemical hazards agreed jointly by employer and
    workers.  In some countries, these agreements will be negotiated as
    collective bargaining agreements or health and safety agreements
    between management and workers.  Sometimes these agreements are
    additional to the minimum obligations imposed on employers by
    workplace health and safety laws.

    The employer and elected worker health and safety representatives
    and/or committees in each workplace should participate in the
    identification and control of chemical hazards through:

    *    regular inspections with standard checklists for particular
         chemicals and chemical processes;
    *    investigation of workers' complaints;
    *    use of accident and sickness records;
    *    regular surveys of workers' health;
    *    environmental and biological monitoring;
    *    assessment of government inspectors'/consultants' reports;
    *    investigation of the causes of accidents and their prevention;
    *    development of a workplace chemical register.

    3.4  Controlling the hazard

    The prevention of adverse health effects arising from occupational
    exposure to chemicals requires a comprehensive control strategy. 
    Ideally, exposure should be prevented altogether, i.e. at the source,
    through substitution or enclosed processes, for example. If this
    cannot be achieved, the level of exposure should be reduced as much as
    possible, i.e. during the transmission stage, through ventilation and
    the use of protective clothing -- and, certainly, to levels at which
    neither health effects nor irritation occurs.  A third strategy

    comprises measures to counteract the effects of exposure through early
    diagnosis of any disease and attempts to prevent the progression of
    existing disease, through regular medical monitoring.

    The following controls may be used, in descending order of priority:

    *    substitution of hazardous chemicals or processes with less
         hazardous ones;
    *    engineering controls, e.g. improved ventilation;
    *    development of safe working procedures;
    *    reduction of the number of exposed workers;
    *    reduction of the duration and/or frequency of exposure of
    *    use of personal protective equipment, e.g. respirators, goggles;
    *    regular environmental and biological (medical) monitoring or
         surveillance to check that the above control methods are proving

    3.4.1  Substitution

    The most effective control measure for any hazardous chemical is to
    remove it entirely from the workplace and replace it with a less
    hazardous chemical.  This is crucial for very toxic chemicals,
    carcinogens, chemicals that can damage the reproductive system and
    sensitizing agents. This approach should, of course, be applied to all
    chemical hazards.

    An example of substitution is the replacement of the solvents
    2-methoxy- and 2-ethoxy-ethanol (commonly used in paints and lacquers)
    with the solvent 2-butoxy-ethanol.  Both 2-methoxy- and
    2-ethoxy-ethanol cause reproductive health effects (including
    shrinking of the testicles and birth defects) in animals at low levels
    of exposure; 2-butoxy-ethanol has not been found to cause these
    effects.  In terms of solvent properties, there is no significant
    difference between any of these three solvents.

    Care must be taken to obtain all available information on proposed
    alternative chemicals.  Substitutes may turn out to be just as
    hazardous as or even more hazardous than the materials they replace.

    It is also often possible to substitute safer processes.  In this
    connection, a process is the sequence of steps involved in the
    manufacture or use of a chemical.  The manufacture of chemicals
    usually entails a series of intermediate stages. The chemicals
    produced during these stages (called intermediates) are sometimes
    more toxic than the starting or final materials.  Whenever possible,
    dangerous processes should be substituted to avoid the production of
    toxic intermediates.

    3.4.2  Engineering controls  Total enclosure

    If a chemical hazard cannot be removed from the workplace by
    substitution, then the next best solution is to physically enclose the
    hazard to prevent it from coming into contact with either workers or
    the environment.  This is known as total enclosure or containment of
    a process (see Fig. 35).  For example, open tanks from which chemical
    vapours can escape into the workplace air can be replaced with closed
    tanks with inlet and outlet ports for filling and emptying.  Liquids
    such as solvents can be transferred by being pumped through sealed
    pipes rather than poured in the open air.

    FIGURE 35  Ventilation

    Ventilation systems are one means of removing contaminated air from
    the workplace.  There are two general types of ventilation:

    *    dilution or general ventilation; and

    *    local exhaust ventilation.

    Dilution ventilation is simply the process whereby clean air is mixed
    with contaminated air.  The concentration of the airborne
    contaminant is thus reduced, although the workplace air will still
    contain some of the contaminant.

    A simple dilution ventilation system consists of two major components:
    a source of clean air and an exhaust fan for removing the contaminated
    air.  The ventilation system can be totally passive, which means that
    the exhaust is a chimney or open vent in the ceiling from which the
    dirty air is expelled, and the source of clean air an open inlet in
    one of the workplace walls (see Fig. 36). This is the most basic, i.e.
    least effective, system.  An improvement on this system would be a fan
    at the exhaust forcing the dirty air out.  An even better system would
    have both an exhaust fan and an inlet fan.

    Dilution ventilation is rarely an adequate means of safeguarding
    health in the workplace, as:

    *    it does not prevent the release of a contaminant into the
         workplace air;

    *    it is ineffective against dusts, metal particles and metal fumes
         that are too heavy to be removed by gentle air movement;

    *    it does not provide sufficient protection against highly toxic
         chemical vapours and gases, carcinogens or chemicals causing
         reproductive effects;

    *    it is ineffective against "surges" of gases and vapours or
         irregular emissions of contaminants; and

    *    workers very close to a contaminant source may still experience
         very high levels of exposure.

    FIGURE 36

    Local exhaust ventilation systems remove airborne contaminants near
    their source.  Such systems must be properly designed and maintained
    and must work effectively so that workers will not inhale contaminated
    air.  For any work process that uses or produces moderately toxic or
    highly toxic chemicals that cannot be effectively enclosed, a local
    exhaust system is essential (see Fig. 37).

    A local exhaust ventilation system contains four major parts: a hood,
    ducts, an air cleaner and a fan.  Contaminants are drawn in
    through the hood, transported inside the ducts, removed by an air
    cleaner and sucked through the system by a fan.  A local exhaust
    system always needs a suitable inlet of clean replacement air.

    Some of the advantages of local exhaust ventilation include:

    *    the capture of hazardous contaminants at their source, and the
         removal of contaminants from the workplace;

    *    the capacity to handle all types of contaminants, including
         dusts, metal particles and metal fumes; and

    *    the capacity to protect workers close to the contaminant's

    To be effective, however, a local exhaust ventilation system must be
    carefully designed for the specific process, and the appropriate
    parts selected.  The hood should be close enough to capture all
    contamination and pull it away from, not past, the worker's breathing

    Moreover, local exhaust systems require regular cleaning, inspection
    and maintenance (e.g., regular filter changing, checking of the
    airflow rate with an anemometer, checking for leaks or holes in the
    ducting and checking for blockages).  It should be noted that exhaust
    air will be contaminated and may endanger the health of people outside
    the workplace.

    3.4.3  Safe working procedures

    Workers involved in the manufacture or use of chemicals are usually
    given a list of instructions by their employer on how to weigh,
    measure and combine the various chemicals used in their workplace. 
    Often these instructions tell the worker what to do to make the
    product but carry no information on the hazards or risks involved or
    on ways to protect against the chemical hazards present, e.g. how to
    operate ventilation systems or when to change filters on breathing

    FIGURE 37

    A safe working procedure should include instructions for each step in
    a process, as well as the steps necessary for workers to protect
    themselves from the health effects of the chemicals used in that

    A "Code of Practice" is a more general description of safety measures
    to be adhered to during a particular type of process or by a
    particular industry (see Fig. 38).  The International Labour
    Organisation (ILO) has developed codes of practice for some processes,
    and some countries have national codes of practice.  For shop-floor
    use, a relevant code of practice should include:

    *    a list of all chemicals used in that process;
    *    a summary of the health effects of those chemicals and the way in
         which exposure to, and absorption of, the chemicals may occur;
    *    an outline of the equipment necessary to complete a task
         correctly and safely;
    *    the procedures for operating that equipment correctly.  For
         example, if a chemical has to be heated, information should be
         included on the maximum temperature, the consequences of heating
         the chemical too much (the risk of explosion or fire) and the
         ventilation system required to protect workers and the general
         public against fumes or vapours of the heated chemical;
    *    a description of any personal protective equipment that may be
         necessary, such as face masks or gloves, together with the
         specifications and standards these must meet and information on
         exactly how and when the equipment should be used; and
    *    details of how often and what environmental and biological
         monitoring should be performed and of procedures for action if
         "trigger" levels (see below) are exceeded.  For example, carbon
         monoxide is a highly toxic but colourless and odourless gas
         produced by many industrial processes that involve heating or
         burning (e.g. blast furnaces and coke ovens).  The carbon
         monoxide level in the workplace air should be monitored
         continuously while the process is in operation.  When the carbon
         monoxide level reaches a set percentage of the exposure limit
         (see section 7.1 of this manual), an alarm should sound and
         workers should leave the workplace until the carbon monoxide
         level has fallen to a safe level.  This "action" or "trigger"
         level must be a small fraction of the exposure limit (around 10%)
         to allow room for error in measurement and delay in alerting
         workers to the hazard.

    FIGURE 38

    Some work procedures require clearance or a "permit-to-work"
    certification.  The latter is essentially a document that sets out the
    work to be done, the hazards involved and the precautions to be taken,
    such as testing the working area for chemicals before entering.  It
    predetermines a safe drill and is a record that all foreseeable
    hazards have been considered in advance and precautions taken.  It is
    of particular importance with respect to maintenance workers, for the
    repair of chemical-bearing lines, for work in confined spaces and so

    A permit-to-work system does not in itself make a job safe but is
    designed to protect the workers involved.  Workers should therefore be
    well trained in the accompanying procedures.

    3.4.4  Reducing the number of exposed workers and their duration
           of exposure

    Only those directly involved with a job or chemical process should be
    exposed to any chemical hazards present.  For example, if chemicals
    that give off vapours are being heated, then only those workers needed
    for the job should be in the area.  Maintenance workers, electricians,
    cleaners or other workers should do their work when the chemical
    hazard is not present.

    The risk to maintenance workers is often ignored or seriously
    underestimated when planning chemical control measures. Maintenance
    workers may be more highly exposed because normal control procedures
    are not geared to their work; these procedures may not be operational
    at times when they do their work; and they may be in closer proximity
    to hazardous plants and processes than other workers when they do
    repair or maintenance work.  Specific provisions for the protection of
    maintenance workers must be included in any chemical safety procedure.

    In certain circumstances, the reduction of the duration or the
    frequency of exposure of workers may be achieved by job rotation. 
    However, it is never acceptable to simply expose more workers less
    often to unacceptably high levels as an alternative to reducing
    exposure levels.

    3.4.5  Personal protective equipment  Principles

    Whereas engineering controls place a barrier around a hazardous
    process or chemical, personal protective equipment is often used to
    create a "barrier" around a worker to prevent chemicals already
    released into the workplace air from reaching the worker's lungs,

    skin, etc.  The use of personal protective equipment should be
    resorted to only after the methods outlined above -- substitution and
    engineering controls -- have first been considered and acted upon.

    Personal protective equipment is rated as the least effective method
    of protection and is often uncomfortable or difficult to work with.

    Personal protective equipment against chemicals includes:

    *    face shields, goggles and safety glasses;
    *    gloves;
    *    rubber boots;
    *    plastic or rubber overalls and aprons;
    *    hard hats;
    *    respirators; and
    *    dust masks.

    A personal protective equipment programme requires the following steps
    and resources:

    *    the correct equipment -- e.g. a respirator designed to protect
         against dust is useless if the hazardous chemical is present as a
         gas; and many solvents can rapidly penetrate natural rubber
    *    a thorough training programme for workers who are required to use
         the equipment, with follow-up training at regular intervals;
    *    tests to ensure that equipment fits correctly.  This is
         particularly important for face masks and respirators;
    *    a regular equipment maintenance programme.  This includes regular
         cleaning of equipment, inspection to ensure that it is operating
         correctly and regular replacement of items such as gloves or
         disposable parts such as respirator filters.  Respirator filters
         should be replaced at regular time intervals rather than only
         when they have become clogged; and
    *    a personal set of equipment for each worker and a secure and
         clean place in which to store it.

    In some situations, the use of personal protective equipment is
    unavoidable.  This applies particularly to eye goggles, face shields,
    boots and hard hats.  Because these items are designed to protect the
    worker against accidents and unexpected exposures, they must be worn
    at all times.  For some jobs, such as pesticide spraying by hand, no
    other means of protection is possible, in which case protective
    clothing, gloves and respirator masks must be worn.

    Other tasks that may be necessary from time to time, such as the
    cleaning of a ventilation system, will often require the wearing of
    personal protective equipment such as respirators.  When the chemicals
    are particularly dangerous or concentrations very high, air-supplied
    respirators are required.

    Chapter 4 of each HSG -- and also the ICSC or Summary of Chemical
    Safety Information -- provides general advice on types of personal
    protective equipment that are suitable for the chemical being used. 
    Workers should also seek information from the manufacturer of the
    chemical about suitable protective equipment.  Often this information
    is included in the chemical manufacturer's MSDS (see Chapter 8 on
    "Getting Further Information").  Protective clothing

    Not all protective clothing protects its wearer from all chemicals. 
    Gloves, aprons and overalls, for instance, must be made from a
    material that is not penetrable by the chemical in use at the time. 
    Otherwise, chemical solvents may pass unnoticed through the material,
    emerging in an invisible but hazardous form inside gloves or other
    protective clothing.  If this occurs, the chemical will come into
    contact with the skin and could prove as dangerous as would be the
    case if the individual were working without any protective clothing.  Gloves

    General advice about choosing protective gloves includes the

    *    For maximum protection against skin absorption, gloves should be
         of suitable material, fit properly and be in good condition.

    *    It is important to get information from the suppliers of
         protective equipment about what equipment has been tested and
         found to be resistant to the particular chemicals you are using. 
         Ask specifically about the chemical's breakthrough time, i.e. how
         long you can wear the gloves before the chemical penetrates
         through to your hands.  Some gloves, especially PVA (polyvinyl
         alcohol) gloves, actually disintegrate on contact with water.

    *    Only use gloves once when working with chemicals that have a
         quick breakthrough time.  Remember, the chemical may still be
         penetrating the gloves after you have removed them.

    *    Cotton flock or fabric lining in gloves helps absorb perspiration
         and also partly insulates the hands against heat or cold.

    *    Double gloving is recommended if little is known about the
         chemical in use.

    *    Unless gloves are thoroughly cleaned when they are taken off, any
         chemical picked up on the glove lining could come into contact
         with the skin.

    *    Dusts from recently activated resins are almost as irritating and
         harmful to the skin as the original liquid; gloves should be worn
         even when handling the resultant laminate.

    *    Some chemicals in combination will penetrate gloves more quickly
         than they would separately, e.g. pentane and trichloroethylene.

    *    Solvents may also carry other substances through the gloves; e.g.
         xylene carries organophosphates through PVC (polyvinyl chloride)

    *    Search for a listing of gloves available in your country and
         information on their suitability for different jobs.  The local
         safety inspectorate may have such a list.  Do you need a respirator?

    There are many different types of respirators available.  This section
    will help you to ask the right questions to make sure that you are
    being provided with the correct type of respirator for your work

    *    What are you exposed to?

    This will depend on the type of hazard, i.e. whether the contaminant
    is a gas, vapour, dust, mist or fume; whether there is a potential for
    oxygen deficiency (in the USA, if the oxygen level is likely to fall
    below 17%, or 19.5% in some countries, fresh air must be provided); or
    whether the atmosphere is immediately dangerous to life or health,
    e.g. high concentrations of cyanide fumes.

    *    What concentration of the chemical are you exposed to?

    It is important to know how much of the chemical is present in the air
    you are breathing, because different types of respirators have
    different levels of efficiency.  You should know what concentration of
    the chemical you are exposed to and the concentration that is
    classified as acceptable (see section 7.1 of this Manual on "exposure
    limits" for reasons why even these limits may not be safe inside a

    Once you know these two concentrations of the chemical, you will be
    able to work out the amount of protection you need from a respirator. 
    For example, if the acceptable level of exposure for Solvent B is 10
    ppm and the concentration in the workplace is 100 ppm, you will need
    an air filter with a "nominal protection factor" of 100/10 = 10.

    *    Does the chemical have any warning signs?

    You will need to know how long you can wear the respirator before you
    have to change the filter or cartridge/canister or before the air
    supply runs out in a self-contained breathing apparatus.  You will
    also need to know whether the chemical has a particular smell or is
    irritating (either will serve as a warning if the chemical begins to
    break through the absorbent material in the respirator).  This is
    particularly important when air-purifying respirators are used against
    gases and vapours.

    *    Is there any other chemical present that you also need protection

    If a mixture of gases or vapours or particulates is present, this will
    influence the choice of respirator.

    *    Can the chemical be absorbed through the skin?

    If the answer is "Yes", then the rest of the body, including the face,
    must be protected and a full-face respirator worn.

    *    Can the chemical irritate the eyes at the expected concentration?

    If "Yes", then the eyes must be protected -- either separately through
    the use of goggles or by use of a full-face respirator.

    BEEN ANSWERED.  Types of respirators

    I    Air-purifying respirators -- The air is drawn in through an
    absorbent material in the case of gaseous contaminants or through a
    filter in the case of particulate contaminants.

    a)   Air-purifying respirators for gaseous contaminants

    These consist of a face-piece with a cartridge or canister to remove
    the gas or vapour.  The face-piece can be quarter-mask, covering the
    nose and mouth but not fitting under the chin; half-mask, covering the
    nose and mouth and fitting under the chin; or full-face mask, covering
    the face from the hairline to under the chin.  The full-face mask
    offers greater protection than half- or quarter-masks, as the mask
    will fit the face more closely, giving a better seal.

    The cartridge or canister containing the material that removes the gas
    or vapour is fitted to the front of the face-piece and air drawn
    through it (see Fig. 39).  A cartridge offers less protection than a
    canister.  A cartridge can be used to protect against gases or vapours
    of relatively low toxicity.  A canister will remove limited
    concentrations of certain toxic gases or vapours for a specified time,
    after which the canister must be replaced.

    FIGURE 39

    b)   Air-purifying respirators for particulate contaminants

    These consist of a face-piece and a filter.  The face-piece can be a
    quarter-, half- or full-face mask.  The filters are classified as:

    *    low efficiency -- used against dusts and mists of low toxicity,
         in low concentrations;
    *    medium efficiency -- used against dust and fume concentrations up
         to 10 times the exposure standard, except where the dust or fume
         is highly toxic, e.g. hexavalent chromium; and
    *    high efficiency -- used, with a full face-piece respirator, where
         toxicity or concentration of a chemical is high.

    A combined gas and dust respirator should be used where both gases/
    vapours and dusts are present.

    c)   Air-purifying respirators for both gaseous and particulate

    These respirators can be used where a combined hazard is present, e.g.
    paint spraying or spraying with pesticides.  Some particulate filters
    will also absorb some gases/vapours, but you must insist that evidence
    is provided that they will protect against both.  The filters should
    be marked to show what they protect against.

    The length of time a cartridge or canister can be used depends on the
    concentration of gas, vapour or particulate and the activity of the
    wearer.  If you are doing hard physical work, you will breathe more
    deeply and the canister will become saturated sooner.

    Air-purifying respirators should not be used in a confined space, or
    there might be a shortage of oxygen.

    Face masks that do not fit the worker or that are worn out or blocked
    by particulates can result in serious injury, as the wearer believes
    him/herself protected and is therefore unaware that he or she is
    exposed. The presence of facial hair can also mean that the face mask
    does not fit perfectly, with the result that contaminated air could
    enter between the mask and the skin.

    II   Supplied air units -- These respirators supply clean air directly
    into the respirator, rather than filtering out the chemical from the
    air in the work environment (see Fig. 40).  There are two types:

    a)   Supplied air respirator -- Air is supplied through an air supply
    line or hose.  In the case of an air supply line, the air comes
    from a compressed air source through a high-pressure hose.  The air
    can be supplied to a half- or full-face mask, helmet, hood or complete

    suit.  These respirators can be used against particulates, gases or
    vapours.  They provide a high degree of protection but cannot be used
    in atmospheres immediately hazardous to life or health, as any fault
    with the air supply or air line could render the worker highly

    For hose masks, air is supplied from a clean-air area through a
    large-diameter hose to the face-piece.  Compressed air is not used. 
    The air can be either pumped in by a hand- or motor-operated blower or
    simply drawn in by the wearer.  These respirators always have a
    full-face mask, which must fit the face well.  They should also not be
    used in atmospheres immediately dangerous to life or health.

    FIGURE 40

    b)   Self-contained breathing apparatus -- This allows the wearer to
    carry a respirable breathing supply, which may last from a few minutes
    to four hours, depending on type.  With some, a negative pressure is
    created inside the face-piece when the wearer breathes in, so the air
    is drawn into the face-piece only when the wearer breathes in, instead
    of being supplied to the face-piece before the wearer breathes in.  If
    the face seal is not good and a negative pressure is created inside
    the face-piece, contaminated air may be sucked into the respirator
    through the gaps between the face and the face-piece.  These
    negative-pressure types of breathing apparatus should not be used in
    atmospheres immediately hazardous to life or health.  Training and fitting

    Workers must be trained as to why respirators must be worn and how to
    choose, fit and use them  before they are expected to use them. 
    Respirators are uncomfortable to wear, and workers will often not use
    them if they do not fully understand the health risks they face.  Respiratory protection programme

    If respirators are to be used correctly and effectively, a respiratory
    protection programme administered by a trained person should be
    established.  The programme should include written standard operating
    procedures and specifications for:

    *    respirators (selected on the basis of hazards);
    *    instruction and training of the user;
    *    cleaning and disinfection;
    *    storage;
    *    inspection;
    *    surveillance of work area conditions;
    *    evaluation of the respiratory protection programme;
    *    use of certified respirators; and
    *    medical review.

    3.5  Monitoring the hazard

    Monitoring should be performed to check the efficiency of control
    methods in the workplace.  There are two types of monitoring --
    environmental monitoring to measure workers' exposures to air
    contaminants, and biological monitoring of individual workers to
    test for degree of exposure, whether dermal, respiratory, via
    ingestion, etc.  The results can be compared with safety standards for
    workplace air or biological materials.

    3.5.1  Environmental monitoring

    Monitoring of the workplace environment for contaminants may be
    undertaken in two ways: through integrated sampling or, for some
    substances, use of direct reading instruments. Direct reading
    instruments give an immediate result, but for many substances such
    devices are not available.  In addition, they must be carefully
    calibrated.  Integrated sampling, on the other hand, can be used for a
    wider range of substances, although the result is available only
    following laboratory analysis.  Integrated sampling involves measuring
    the concentrations or levels of dusts, mists or gases in the workplace
    air, by sampling known amounts of air containing the dust, mist or gas
    with special pumps and filters and then chemically analysing the
    results.  This monitoring may be technically complicated and must
    usually be carried out by an industrial hygienist; in some cases, it
    is less complex and can be done by trained workers.

    There are two main types of integrated sampling:

    *    Static monitoring -- in which an air pump is set up at a fixed
         point.  This is useful for chemicals that are expected to spread
         evenly throughout the entire workplace.  Static monitoring may
         over- or underestimate the exposure individual workers are
         receiving, depending on where measurements are made.

    *    Personal sampling -- in which air is sampled from individual
         workers' breathing zones by a portable pump attached to the
         workers' clothing.  This method gives a much better indication of
         an individual worker's exposure to a chemical and, of the two air
         sampling techniques, is the method of choice.  The advantage over
         static or fixed-point monitoring is that a reading for exposure
         is obtained that better reflects contamination in the worker's
         breathing zone.  With static or fixed-point monitoring,
         concentrations in the worker's breathing zone will not be
         measured if the measurement is taken at too great a distance from
         the source.

    The following questions should be considered in any environmental
    monitoring programme:

    *    Are the samples being taken at the right place, i.e. near the
         breathing zones of operators?

    *    Is the sample being taken at the time when pollution levels are
         highest? The aim of environmental monitoring should always be to
         determine the highest level of exposure, not the average or usual
         level of exposure.

    *    Are all contaminants being measured?

    *    Have workers been involved in the planning of monitoring of their

    *    Are the test results being made available to safety
         representatives and safety committees regularly, and are the
         results being discussed?

    Environmental monitoring should be performed before decisions are made
    regarding methods for controlling chemical exposure.  In this way,
    control methods can be designed that cope with the highest levels of
    chemicals measured, not the average levels.  In other words, control
    measures must be able to cope with the "worst case".

    After methods to control exposure (e.g. exhaust ventilation) have been
    introduced, environmental monitoring should be repeated regularly to
    ensure that the control methods are operating satisfactorily.

    3.5.2  Biological monitoring

    Biological monitoring of chemical exposure aims to measure either the
    amount of a chemical that has been absorbed by a worker or the effect
    of that absorbed chemical on the worker (as opposed to environmental
    monitoring, which measures the level of exposure).

    Biological monitoring involves taking a sample of body fluid, usually
    blood or urine, and measuring the level of the chemical or its
    metabolite (see Chapter 2).  Alternatively, an effect of that chemical
    on the body may be determined by measuring the level of an enzyme or
    other chemical in the blood or urine.

    A good example is biological monitoring for lead absorption.  All
    workers regularly exposed to lead or to significant levels of lead
    should have blood samples taken regularly.  The level of lead in the
    blood can then be measured directly, and this will give an accurate
    estimate of how much lead that worker has recently absorbed.  One of
    the effects of lead on the body is the poisoning of red blood cells. 
    By measuring the level of protoporphyrin -- a chemical in the blood
    produced by poisoned red blood cells -- an estimate of the effects of
    lead absorption can be obtained (see Fig. 41).

    Many chemicals can be monitored biologically, but the results do not
    always reflect the level of absorption.  Each chemical should be
    considered separately when deciding whether to perform biological
    monitoring.  Lists of those chemicals for which biological monitoring
    is recommended are available, and some such chemicals may have a value
    -- i.e. a biological exposure index -- that should not be exceeded.


    Figure 41.  Biological monitoring (from EHC 3: Lead)

    Pb levels at which no more than 5% of the population will
    show the indicated intensity of effect

    Biochemical                                                     PbB
       effect          Intensity of effect     Population       (g/100 ml)

    ALAD inhibition    perceptible inhibition  adult, children      10
     in blood          >40% inhibition         adults              15-20
                       >70% inhibition         adults               30
                       >70% inhibition         children            25-30

    ALA in urine       perceptible increase    adults, children     40
                       >10 mg/litre            adults, children     50

    FEP in blood       perceptible increase    adult males          30
                                               adult females        25
                                               children             20

    ALA   = delta-aminolevulinic acid
    ALAD  = delta-aminolevulinic acid dehydratase
    FEP   = free erythrocyte porphyrins
    PbB   = blood lead level

    This chapter should be read in conjunction with chapter 4 of the
    relevant HSG, which outlines the main hazards of the chemical
    concerned (including a description of the fire and explosion risks),
    provides medical advice in case of exposure and outlines storage,
    transport and disposal considerations.

    Good safety organization, ventilation and engineering controls,
    adequate provision of information on the health hazards of chemicals
    and training of workers can reduce and control chemical exposures in a

    Nevertheless, poisonings may still occur, and it is important that
    training and proper equipment are available to workers so that
    emergency situations can be handled satisfactorily (see Fig. 42).

    4.1  First aid and emergencies

    The following general principles should be employed when designing a
    first-aid programme for a workplace where chemicals are used:

    *    There should be at least one worker present on every shift who
         has received approved first-aid training.  Follow-up or refresher
         courses should be offered regularly.

    *    All workers should receive training in the technique of cardio- 
         pulmonary resuscitation (CPR).  CPR is used when a person's heart
         has stopped beating or when he or she has stopped breathing.

    *    It is essential that any workers affected or injured by chemicals
         are removed from the area where the chemicals are present. 
         Rescuers should make sure of their own safety in any attempt at
         rescue and/or resuscitation.  Self-contained breathing apparatus
         (a respirator mask with its own air supply) may be necessary so
         that those attempting to rescue an injured or affected worker do
         not become poisoned themselves.

    *    Emergency showers and eye-baths should be situated close to the
         site of any potentially hazardous work processes.

    FIGURE 42

    *    First-aid boxes should be provided in all work areas and workers
         trained in emergency first-aid procedures for any accident or
         chemical exposure that may occur.

    *    Telephone numbers for medical assistance and ambulances should be
         prominently displayed in the workplace. A telephone must always
         be available for use in an emergency.

    *    There should be an "emergency response plan" in which individuals
         are assigned to perform certain tasks (such as summon help) while
         all other personnel quickly leave the workplace.  The plan should
         be written down and prominently displayed in the workplace and
         should be practised regularly.

    *    A system should operate whereby all accidents and injuries, no
         matter how slight, are reported in writing to the management or
         employer.  These accident records should be made available to
         workers and their representatives and analysed to determine how
         to prevent the same, or similar, accidents from occurring again. 
         In many countries, occupational accidents and injuries must be
         reported to government bodies.

    *    If an injured worker is sent to hospital or to see a doctor or
         nurse, it is essential that information on the chemicals involved
         in the accident be sent with the worker. The manufacturer's MSDS
         and the ICSC or Summary of Chemical Safety Information contained
         in HSGs (see Chapter 3) are usually suitable for this purpose.

    4.2  Health surveillance

    Health surveillance or medical monitoring consists of periodic
    examination of a worker by a doctor, nurse or other health worker in
    order to detect any health effects of a chemical, to monitor the
    progression or reversal of symptoms or to see if treatment or
    preventive measures are effective.  Tests of lung, heart, liver and
    kidney functions, for instance, may be performed. Although in some
    cases -- e.g. chemicals that cause asthma -- such testing is useful,
    it should always be remembered that medical monitoring can detect
    damage to health only after it has occurred (see Fig. 43).  Further
    damage can then be prevented, but medical monitoring does not actually
    prevent the occurrence of the initial health effects.


    Figure 43.  Health surveillance (from HSG 6: Methylene Chloride)

    4.2  Advice to Physicians

    No specific antidote is known. Treat symptomatically. Administer
    oxygen if needed. Do not administer fats, oils, alcohol, epinephrine,
    or ephedrine. Pay attention to signs of anoxaemia, impending
    pulmonary oedema, and ischaemia of the heart. Monitor ECG. Treat
    skin as for a thermal burn.

    4.3  Health Surveillance Advice

    Persons handling methylene chloride should frequently undergo
    periodic medical examination with emphasis on the functioning
    of the central nervous system and irritation of the skin and
    eyes. Monitoring of blood-carboxyhaemoglobin concentrations can
    give an indication of the extent of exposure.

    Medical monitoring is often unable to detect the long-term or chronic
    health effects of chemicals until they are quite advanced.  This
    applies particularly to:

    *    cancer caused by carcinogenic chemicals;
    *    effects on the brain and nervous system; and
    *    reproductive effects.

    Medical monitoring is useful for assessing the effectiveness of
    measures implemented to control chemical exposure, but it is not a
    substitute for environmental monitoring and control methods.

    4.3  Fire and explosion hazards

    Many chemicals used in the workplace will burn or explode easily. 
    Accidental fires or explosions of flammable or explosive chemicals
    represent major hazards.  Special precautions must be taken when
    handling, storing or transporting these chemicals to prevent fires or
    explosions (see Fig. 44).


    Figure 44.  Explosion and fire hazards
                (from HSG 6: Methylene Chloride)

    4.3   Explosion and Fire Hazards

    4.3.1  Explosion hazards

    Methylene chloride may react explosively with light metals (lithium,
    sodium, potassium, aluminium, magnesium) as well as with alloys of
    sodium.  Explosive mixtures are formed with dinitrogen tetroxide
    (N2O4) dinitrogen pentoxide (N2O5), nitric acid, and
    compressed oxygen.

    4.3.2  Fire hazards

    Methylene chloride is flammable in an atmosphere with an increased
    oxygen content.  In pure oxygen, the flammable limits (explosive
    limits) are 15.5% and 66.4%.  Methylene chloride is also flammable
    if small amounts of combustible material are added.  The compound
    decomposes in contact with open flames and glowing surfaces with the
    formation of harmful gases, such as hydrogen chloride, which forms
    mists of hydrochloric acid with moisture, and phosgene.

    4.3.3  Prevention

    Do not use methylene chloride in the vicinity of a fire, a hot
    surface (e.g. a portable heating unit), or during welding.  Do
    not smoke.  Do not add any combustible material to methylene
    chloride.  Avoid using compressed oxygen when handling
    methylene chloride.  Avoid contact between the compound and
    light metals, alloys of light metals, dinitrogen tetroxide,
    dinitrogen pentoxide, nitric acid, or liquid oxygen.  In case
    of fire, keep drums cool by spraying with water.

    Fire (or combustion) is the violent combination of oxygen in the air
    with a combustible chemical while producing heat (an exothermic

    In fires involving chemicals or chemical products, the chemicals
    usually become broken down into combustion by-products.  Many of
    these combustion by-products are highly toxic gases and fumes.  This
    may be the case even if the original chemical was not particularly
    toxic.  For example, the gas Freon 12, or dichlorodifluoromethane, is
    widely used as a refrigerant.  It is toxic only at very high
    concentrations.  However, the thermal decomposition products of Freon
    12 are very toxic gases, including phosgene, which causes potentially
    fatal pulmonary oedema (accumulation of water in the lungs), even at
    very low levels of exposure.  Similarly, polyurethane foam, which is

    commonly used as insulation in industry, has relatively low toxicity
    in the cured state.  However, when polyurethane foam burns, large
    amounts of highly toxic gases, including cyanide and hydrogen
    chloride, are released.

    4.3.1  Flammable substances

    A flammable substance is any chemical or material that will continue
    to burn after having been ignited.  A substance of high flammability
    is one that will easily ignite at room temperature on contact with
    low-energy ignition sources such as a spark.  A substance of low
    flammability will ignite only after heating or prolonged contact with
    a high-energy ignition source.  The flammability of a substance is
    often ranked according to its ability to catch fire at certain


    extremely flammable        < 0C

    highly flammable           0-21C

    flammable                  21-55C

    combustible                > 55C

    Other important information about the flammability of a substance can
    be gathered by looking at the flash point and the flammability
    (explosive) limits (see Chapter 1) for that substance.  This
    information is given in the Physical Properties section of the ICSC
    and usually appears on the MSDS supplied by the chemical manufacturer.

    4.3.2  Dust explosions

    Any solid material that is capable of burning in a finely divided form
    can give rise to a dust explosion hazard.  All that is necessary is
    for enough dust to be in the air and for a source of ignition to be
    present.  Flame from the source of ignition will spread in all
    directions through the cloud of dust, burning the dust and causing
    expansion, thus increasing pressure on the surroundings.  In a grain
    store, for example, this pressure could be great enough to cause the
    roof or walls to be blown off.  The first explosion can whip dust that
    is lying on window sills, pipework and equipment into the air, and a
    second explosion can result.

    Many dusts, including natural materials such as starch, sugar, flour,
    coal and wood, plastics and organic chemicals, and light metals such
    as aluminium, magnesium and titanium, can explode in this way. 
    Accordingly, dust explosion must be guarded against in agriculture,
    chemical, metallurgical and process industries, as well as coal

    4.3.3  Sources of ignition

    Flammable substances or dust clouds may be ignited in one of the
    following ways:

    *    Direct flames -- matches, cigarettes, soldering, welding or
         cutting torches.

    *    Heat radiation -- all sources of heat emit heat (thermal)
         radiation, which may ignite a flammable material at a distance.

    *    Electrical sparks -- produced by electric current in a number of
         ways, including during electric arc welding; by power supplies
         such as sockets and switches and sliding contacts; from electric
         motors in power tools or the ignition systems of internal
         combustion engines; by lightning; and as a result of static
         electricity build-up between two non-conducting materials such as
         belts on a pulley, rubber tyres on the ground or liquids pumped
         or poured through pipes.

    *    Mechanically produced sparks -- two hard materials rubbing
         against each other at high speed may produce sparks capable of
         igniting flammable chemicals, e.g. when grinding.

    *    Chemical reactions -- many chemical reactions produce heat.  The
         design of the chemical process should take this into account and
         make provision for the removal of excess heat.  However, excess
         heat may develop if the incorrect or wrong proportions of
         chemicals are used.  This may start a fire or trigger an

    *    Spontaneous combustion -- some substances oxidize (combine with
         oxygen) as soon as they are exposed to air.  Usually this occurs
         slowly, but with some chemicals it may happen rapidly and produce
         considerable heat in the process.  These chemicals must be stored
         in tanks or containers that allow all air to be removed and
         replaced with a gas that will not combine with the chemical
         (usually nitrogen).  If this mechanism fails and air enters the
         container, a fire or explosion may result.

    Safety information about fire hazards is given in chapter 4 of the
    HSGs and is also contained in the ICSCs.  Information on fire and
    explosion hazards should always be included in chemical manufacturers'

    4.3.4  Fire-fighting

    Equipment used to extinguish and control fires is of two types: fixed
    and portable.  Fixed systems include water equipment, automatic
    sprinklers, hydrants and special pipe systems for dry chemicals,
    carbon dioxide, foam, etc.  Special pipe systems are applicable to
    areas of high fire potential where water may not be effective, such as
    tanks for storage of flammable liquids.

    Fixed systems must be supplemented by portable fire extinguishers.  As
    well as providing a means of rapidly extinguishing a fire, they can
    often be used to prevent a small fire from spreading.

    To be effective, portable extinguishers must be appropriate for the
    type of fire; the HSGs provide information to this effect.  For
    example, water-based extinguishers can be used on ordinary
    combustibles such as wood, paper, textiles, etc., where a
    quenching/cooling effect is required.  Dry chemical or carbon dioxide
    extinguishers are used on flammable liquid and gas fires, such as oil,
    gasoline, paint and grease, where an oxygen-exclusion or
    flame-interrupting effect is necessary.  Dry powder agents are
    necessary to combat metal fires.

    In addition, portable extinguishers must be available in sufficient
    quantity to protect against potential fires in any area.  They should
    be located where they are readily accessible for immediate use,
    maintained in good operating condition, inspected frequently and
    recharged as necessary.  Workers should be trained to use them

    If a fire or explosion warrants intervention by outside fire service
    personnel, these personnel should be advised of the nature of the
    chemicals and the worksite so that they can evaluate what is needed
    for their own safety.

    4.4  Storage

    The HSGs give some advice on storage (see Fig. 45), but the
    manufacturers' or suppliers' MSDSs should give specific instructions
    on the storage of each chemical.  These conditions must be strictly
    adhered to, as storage requirements vary according to the nature of
    the chemical being stored.  Incorrect storage can have disastrous
    results, e.g. fire, explosion or release of toxic chemicals.

    The MSDS should include the following information:

    *    Need for isolation -- Certain chemicals must not be stored
         together, as any vapours or leaks may, if they intermingle, lead
         to an explosion.


    Figure 45.  Storage (from HSG 19: Pentachlorophenol)

    4.3   Storage

    Technical PCP is a solid.  The formulated product is usually a
    solution in oil or organic solvent, or an emulsifiable concentrate.

    All PCP products should be stored in secure, well-ventilated
    buildings under cool and dry conditions, and out of reach of
    children and unauthorized persons.  Keep away from food, drink,
    and animal feed.

    *    Flash point -- Chemicals must be stored at a temperature below
         their flash points. (Refer to Chapter 2 of this Manual for a
         discussion of flash point.)  Chemicals with flash points below
         34C are especially dangerous.

    *    Upper and lower flammable limits -- Information on flammable
         limits can be found in Chapter 2.  MSDSs often specify a
         "well-ventilated" store-room for particular chemicals, and it is
         essential to comply with this requirement.  More specific
         guidance on the amount of ventilation required can be obtained
         from the manufacturers of the chemicals and guidance can be
         checked by an industrial hygienist or ventilation engineer.

    *    Auto-ignition temperature -- The storage temperature must
         obviously be below the auto-ignition temperature (see Chapter 2).

    *    Type of container -- Chemicals may react with the material from
         which containers are made; the type of container required must be
         specified on the MSDS.  This is especially important if chemicals
         may be transferred from one container to another.  Also, there
         may be other requirements, such as pressure relief valves, which
         are relevant to the storage of particular chemicals.

    *    Type of flooring -- This should be specified, as the flooring
         must be resistant to, and not potentially reactive with, the
         chemical being stored.

    *    Dykes (berms or bunding) -- These are low walls or embankments
         that are constructed around the storage area to contain any leaks
         from storage containers.  The height of the dyke should be
         sufficient to contain any leaks that may occur and any water or
         foam sprayed in the event of a fire.

    *    Alarms -- Alarms should be fitted in areas where potentially
         dangerous chemicals are stored to give early warning of releases
         of those chemicals.

    4.5  Spillage

    Many spills can be prevented by thorough planning of work, provision
    of suitable equipment for carrying out the work, regular preventive
    maintenance and good training of workers.  Any spillages that do
    happen should be thoroughly investigated and remedial action taken to
    prevent their recurrence.

    Employers should ensure that they have the necessary plans and
    equipment to deal with spillages, that the workforce and their
    representatives have been consulted about all such planning and that
    the necessary training is carried out regularly.

    When a spillage occurs, suitable precautions must first be taken to
    protect workers from the dangers of the chemical (fumes, burns, etc.)
    before steps are taken to deal with the spillage (see Fig. 46).

    Some general measures that may apply include the following:

    *    use self-contained breathing apparatus and full protective
         clothing, when applicable;
    *    remove ignition sources;
    *    do not smoke;
    *    evacuate area;
    *    collect leaking liquid in sealable containers;
    *    prevent liquid from spreading or contaminating other areas,
         vegetation, waterways and cargo, with a barrier of the most
         suitable available material, e.g. soil or sand;
    *    in some cases (e.g. hydrazine), a foam can be applied to slow
         down vaporization;
    *    absorb spills in sand, soil, moist sawdust or other inert
         material and transfer to a suitable container; then remove to a
         safe place, with disposal in accordance with local regulations;
    *    sweep up solid products, and transfer to a suitable container;
    *    depending on the chemical, do not allow run-off into sewers: it
         may cause an explosion, kill wildlife or affect water supplies.


    Figure 46.  Spillage (from HSG 35: Phosphorus Trichloride)

    4.7.1  Spillage

    Liquid spillage should be handled only by trained personnel wearing
    protective clothing and full-face mask/positive-pressure breathing
    apparatus.  The spillage should be absorbed in dry sand or in an
    inert absorbent material and shovelled into sealable polyethylene-
    lined containers for disposal.

    Vapour drifting towards people can be "knocked-down" with water
    spray.  Do not wet the spillage itself and never use a water jet on
    a spillage.  When the absorbent medium has been cleared from the
    ground, flush the contaminated area with water until the fumes
    disappear; residues may be neutralized with soda ash (sodium
    carbonate or lime).

    If phosphorus trichloride or phosphorus oxychloride enters a
    watercourse or sewer, or contaminates soil or vegetation, warn the
    police and public authorities immediately.

    The actual steps taken will depend on the chemical in question, and
    information on this must already have been collected from the MSDS and
    from consultations with the manufacturers and/or suppliers and
    emergency services (e.g. fire authorities) and incorporated in the
    employer's written statement on spills.

    4.6  Disposal

    4.6.1  Means of disposal

    Given that enormous volumes of waste are generated in the production
    and use of chemicals, waste disposal has become a key issue in
    environmental protection.  As with protection of the workplace, a
    hierarchy of controls should be applied when dealing with chemical
    waste, as follows:

    *    reduction of waste at the source;
    *    segregation of waste;
    *    recovery and recycling;
    *    waste exchange;
    *    incineration;
    *    immobilization of intractable wastes;
    *    landfill;
    *    discharge into sewer; and
    *    storage.

    The volume of hazardous waste can be reduced by modifying a process or
    improving process control to produce less waste or to render the waste
    less hazardous.

    Waste can be segregated to assist analysis, control and treatment --
    thereby reducing disposal costs.

    *    Recycling -- The best-known form of recycling is the recovery of
         useful fractions for reuse.  These processes are usually carried
         out by specialist recovery operators off-site and involve
         recovery of materials such as oils and solvents, as well as other
         valuable materials, such as the silver in photographic waste.

         Not all wastes are suitable for recycling.  Even when valuable
         materials such as mercury or lead are present, full recovery
         might not be economically feasible owing to such factors as high
         processing costs, small volumes and irregular composition.  As
         extraction techniques improve, more waste products are likely to
         become eligible for recycling.

    *    Waste exchanges -- A considerable amount of waste is suitable for
         exchange.  The aim of the exchange is to put potential users of
         waste materials in touch with industries producing the waste, and
         vice versa. Waste exchanges reduce the volume of wastes requiring
         landfill or incineration and therefore reduce the load on
         disposal facilities and the environment, as well as the cost of

    *    Incineration -- This process, which involves burning in special
         high-temperature (1200C) incinerators, is the only
         environmentally acceptable means of disposing of some wastes,
         such as chlorinated hydrocarbons, polychlorinated biphenyls
         (PCBs) and dioxins (see Fig 47).  These chemicals are highly
         toxic, persistent and non-biodegradable. Incineration effectively
         destroys many organic wastes, and the energy in solvent and fuel
         waste can be exploited in the process.  On the other hand,
         inorganic chemical dyes in plastics may cause pollution problems
         when the plastics are incinerated, and dangerous dioxins may be
         formed if some organic materials are incinerated at too low


    Figure 47.  Disposal (from HSG 19: Pentachlorophenol)

    4.5.2  Disposal

    Surplus product, contaminated absorbents and containers should be
    burned at a high temperature in an appropriate incinerator with
    effluent gas scrubbing.  When no incinerator is available, bury in an
    approved dump, in an area where there is no risk of contamination of
    surface water or groundwater.  Comply with any local legislation.

    *    Immobilization of intractable wastes -- This is used to isolate a
         hazard physically and/or chemically from its surroundings.

    *    Chemical fixation -- Waste is incorporated into an inert matrix
         (framework) to limit or prevent its migration into the
         environment.  Should the waste block be fractured, the waste
         remains bound to the matrix, and leaching is prevented.

    *    Encapsulation -- The waste is sealed within a stable, inert
         material to prevent contact with the environment and prevent
         movement in the environment (migration).  Should the
         encapsulating jacket be broken, the waste could leach away. 
         Encapsulation is more suited to those wastes that pose a handling
         hazard but are relatively inert once buried (e.g. asbestos).

    *    Landfill -- Because of the limited amount of suitable land
         available for waste disposal, it is increasingly desirable that
         liquid wastes be treated by chemical and physical methods,
         followed by biological oxidation (digestion by special bacteria
         or algae).  After treatment, most of the liquid will be suitable
         for discharge to sewers.  The remaining liquid can be recycled or
         incinerated.  Landfills could then be used for most residual
         solids or pastes because they are of smaller volume and less
         likely to migrate through the soil.  A number of solid hazardous
         wastes are not regarded as suitable for disposal to normal
         chemical landfill facilities.  These wastes require the higher
         degree of safety afforded by secure landfill, whereby waste is
         poured into small cells lined with an impermeable clay or
         synthetic material and subsequently buried under a layer of soil. 
         However, it is highly unlikely that such a system would function
         without some leakage through the clay or synthetic material,
         without any damage to the cell and with 100% collection of any
         leaks.  Added to this are the potential problems of infiltration
         by rainwater and ensuring permanent maintenance of the cell if
         the company moves away or ceases to operate.

    *    Disposal of less hazardous waste to the sewer -- This is
         generally not recommended (see Fig. 48).  Most sewage authorities
         make regulatory provisions for the control of the kind and
         quantity of (less) hazardous waste that may be disposed of
         through the sewer.  Improper disposal to the sewer can disrupt
         the biological treatment of sewage and represent a hazard at
         sewer outfalls.  In addition, toxic chemicals (e.g. heavy metals)
         may accumulate in the sewage sludge and create hazards when they
         are disposed of.


    Figure 48.  "Avoid run-off into sewers"
                (from HSG 34: Fenvalerate)

    Never pour untreated waste or surplus products into public sewers or
    where there is any danger of run-off or seepage to streams, water
    courses, open waterways, ditches, fields with drainage systems, or to
    the catchment areas of boreholes, wells, springs, or ponds.

    *    Storage of intractable wastes -- A large volume of hazardous
         waste is currently stored -- usually in steel drums on industrial
         sites, awaiting the development of satisfactory disposal methods
         -- because it is too toxic to be disposed of legally into air,
         water or landfill sites. Most drums are stored in the open, and
         many contain corrosive materials.  There is an added risk of
         hazard from fires, structural damage and vandalism of such toxic
         waste stores.  It is likely that some of these drums will corrode
         and leak.  In some countries, such stores must be registered with
         authorities who, in turn, have a duty to inspect them.

    4.6.2  An example of the effects of incorrect waste disposal

    For years, the residents of Love Canal, a residential community near
    Niagara Falls, New York, USA, complained of noxious vapours in their
    basements, which they believed originated from a disused toxic waste
    dump beneath their housing estate.  Following prolonged rains and
    heavy snows in the winter of 1977, water seeped into the dump-site,
    causing it to overflow and forcing the chemicals out into the soil. 
    Two hundred and thirty-five families were evacuated, and Love Canal
    was declared a federal disaster area, the first instance of a national
    emergency being caused by chemical pollution.  Later, more families
    had to be moved when it was discovered that the toxic waste was
    migrating further afield via underground streams.

    Almost 22 000 tonnes of chemicals had been buried in Love Canal; the
    canal had been capped with clay and covered with soil in 1953.  The
    clay cap was apparently damaged during later building work on the
    site.  Approximately 300 different chemical compounds were buried
    there, although no records were kept of what, or how much, was dumped.

    Studies now reveal that the Love Canal area experienced three times
    the normal rate of miscarriages and three-and-a-half times the normal
    rate of birth defects, most notably cleft palate, mental retardation
    and club foot.

    In addition, US$30 million have been spent on cleaning up the area,
    and US$4.5 million on rehousing residents.


    This chapter is a background to chapter 5 of the HSG: "Hazards for the
    Environment and their Prevention".

    Almost any industrial or agricultural activity in which chemicals are
    used will, by its very nature, have an impact on the environment (see
    Fig. 49).


    Figure 49.  How chemicals can affect the environment
                (from HSG 35: Phosphorus Trichloride)


    Phosphorus trichloride and phosphorus oxychloride hydrolyse in water
    to form hydrochloric and phosphorous or phosphoric acids.  The toxic
    effects on organisms in the environment depend on the extent to which
    the hydrogen ion is diluted and buffered; organisms die if they come
    in contact with undiluted material.

    In general, an environmental hazard will occur only in the immediate
    area of a spillage or if disposed of improperly.  Recovery of soil
    and surface waters is rapid, and there are no residual effects on
    the environment.

    5.1  How do chemicals get into the environment?

    Chemicals are released from the workplace into the environment in the
    form of liquid, dust, fumes or gas.  Such releases can be planned
    (part of the work process, e.g. smokestack emissions, exhaust
    ventilation, waste water into rivers, etc.) or unplanned (accidental). 
    Chemicals can also enter the environment during transport (e.g. from
    the site of manufacture to the site of use), during their intended use
    (e.g. pesticide spraying) or through disposal in landfills and
    waterways.  Chemicals also enter the environment through
    non-occupational activities. Examples include exhaust fumes from motor
    vehicles. Additionally, naturally occurring chemicals such as metals
    in ores may be released by natural processes.

    Chemicals released as smoke and dust from factory chimneys will
    eventually fall to the earth's surface as dust and in rain.  Wind
    speed, air currents and other climatic conditions will determine when
    and where the chemicals will be deposited.  Some will settle on water
    in lakes, rivers and streams, eventually passing into sediments and
    nearby soils.  Others may be transported over long distances and may
    even affect the chemical and physical processes of the atmosphere and
    climate.  For example, the effects of sulfur and nitrogen oxides

    released in industrial areas have contributed to acid rain, often
    falling in countries other than those in which they were emitted. 
    Emissions of carbon dioxide, methane, ozone, etc. are thought to
    contribute to global warming.

    Once chemicals are released into the environment in this way, humans
    and animals will be exposed to them through breathing contaminated
    air, from direct contact with contaminated soil and water, through
    eating plants grown on contaminated soils, by drinking contaminated
    water supplies or by consuming food from contaminated animals (see
    Fig. 50).

    FIGURE 50

    5.2  How do chemicals affect the environment?

    Just as humans and animals can be affected by exposure to toxic
    chemicals (as outlined in Chapter 2), chemicals can also have an
    impact on the environment and the organisms living in the different
    environmental media -- the air, water and soil.

    5.2.1  Air

    Many chemical pollutants in the air begin to have an effect on plants
    and animals at extremely low concentrations, at even less than 1 g
    (or one-millionth of a gram) of chemical per cubic metre of air. 
    Plants and animals vary widely in their sensitivity to chemicals in
    the air.

    Fluorides released from aluminium smelters are an example of chronic
    air pollutants that have caused great damage to livestock over long
    periods of time.  Animals exposed to excessive fluoride pollution
    develop tooth, bone and joint diseases; they become unable to chew
    their food or move. As a result, they lose weight and eventually die. 
    Fluoride builds up in the teeth, bones and tissues of all grazing
    animals and has been found in large amounts in deer, rabbits and birds
    near aluminium smelters.  Humans can also be affected.

    Fluorides also affect plants, causing leaves to die, damage to fruit,
    a slowing of growth and the failure of seed to sprout.

    Plants that are sensitive to fluoride pollution, such as grape vines,
    begin to suffer significant damage if fluoride concentrations in air
    exceed 0.5 g/m3.

    Environmental contamination by chemicals can also occur following
    massive accidental releases, with large-scale immediate and long-term
    consequences.  For example, at least 2500 people died and 200 000
    people were injured when methyl isocyanate gas was released from the
    Union Carbide pesticide plant in Bhopal, India, on 3 December 1984. 
    According to an International Trade Union report, the disaster was
    attributable to poor process design, dangerous operating procedures,
    lack of proper maintenance, faulty equipment and major cuts in
    staffing levels, crew sizes, worker training programmes and skilled
    supervision.  Smaller releases of toxic chemicals had occurred,
    leading to one death and numerous injuries at the Union Carbide plant
    at Bhopal before the 1984 disaster, but little or nothing was done to
    correct these problems, despite vigorous protests by the union
    representing Union Carbide workers.

    Apart from the immediate deaths, reports indicate that other long-term
    health effects are being suffered by the survivors of the disaster. 
    These include lung problems and reproductive effects such as an
    increased rate of miscarriages and stillbirths.

    5.2.2  Water and soil

    As with chemicals in the air, very low concentrations of heavy metals
    and other chemicals in water can have an enormous impact, particularly
    on fish and other aquatic species.

    The effect a chemical pollutant has in water depends on the nature of
    the pollutant and on factors such as acidity (pH), temperature, water
    hardness, the presence of organic materials such as algae and weeds
    and the oxygen content of the water.  For example, the toxicity of
    certain (heavy) metals tends to increase as the acidity of the water

    5.3  Factors affecting a chemical's environmental impact

    The impact of a chemical on organisms and ecological systems will
    depend on the chemical's environmental transport, persistence,
    bioaccumulation and toxicity.

    *    Environmental transport, or mobility, refers to the ease
         with which a substance moves from one environmental medium to
         another (air, water, soil, sediment, etc.) by such processes as
         evaporation, leaching, weathering, etc.

    *    Environmental persistence is one aspect of a chemical's
         environmental fate, i.e. what happens to it when it enters the
         environment.  Once in the environment, a substance can degrade,
         in which case it is generally assumed to be non-hazardous to the
         environment, at least on a large scale, even though there may be
         local effects in the short term.  On the other hand, if a
         chemical is not readily degradable, it can persist in the
         environment for long periods and become widely dispersed. 
         Environmental persistence is therefore the opposite of
         degradation and can be measured in terms of half-life or
         half-time of a chemical in an environmental medium, i.e. the time
         required for the chemical to be reduced to half its original
         amount.  Local conditions may affect a chemical's persistence. 
         For instance, a chemical may persist for longer periods in colder
         climates, whereas it may be readily broken down in sunlight and
         at higher temperatures.

    The organochlorine pesticides are a group of chemicals well known for
    their persistence.  A study found that after only one application of
    the pesticide aldrin to soil, more than 34% was found to be present in
    the soil five years later.  Most of the remaining 66% must therefore
    have remained in water, air or soil, either as unchanged aldrin or in
    the form of other closely related chemicals formed by the
    decomposition of aldrin.  The process by which a chemical is modified
    by a living organism is called biotransformation.

    Bioaccumulation is the accumulation of a chemical by an organism to
    a concentration that exceeds that of the surrounding environment.  For
    example, the concentration of aldrin in the tissues of experimental
    snails has been found to be nearly 5000 times the concentration of

    aldrin in the water in which the snails live.  The more a chemical
    persists, the greater the potential for bioaccumulation.  Chemicals in
    the environment can become increasingly concentrated in the tissues of
    animals higher up in the food-chain, a process known as

    The octanol/water partition coefficient of a chemical (see Chapter 1
    for a discussion of this value) is a good indicator of its
    bioaccumulation potential: the higher the coefficient, the more a
    chemical will tend to bioaccumulate.

    *    Toxicity.  The impact of a chemical on the environment,
         resulting from its toxicity, is more complex.  Chemical
         pollutants affect some environmental media more than others,
         whether these are air, surface water, groundwater, soil or
         sediments.  As explained in Chapter 2, different species will
         react in varying ways and to different degrees to the same
         chemical.  What may be highly toxic to aquatic life may not be
         toxic to birds, for instance, even at the same dose.  Toxicity
         forms the basis of use of pesticides.  Pesticides are applied in
         order to damage or kill a target organism (i.e. the organism that
         is subject to the action of the pesticide).  But it is seldom or
         never possible to limit the effects to target organisms. 
         Pesticides are therefore often perceived as a particular threat
         to health and the environment.

    By determining the effects of a chemical on different species,
    toxicity studies are able to evaluate the environmental impact of that
    chemical.  The effects to be determined should include acute lethality
    (oral, dermal, inhalation LD50 and LC50); sublethal effects on
    non-mammals (soil organisms, bees, birds, etc.), mammals and plants
    (usually expressed as the percentage of growth reduction as a result
    of exposure to the chemical in water, air or soil); mutagenicity/
    genotoxicity; teratogenicity; and carcinogenicity.

    5.4  The importance of prevention

    Once chemicals have been released into the environment, little or
    nothing can be done to remove them.  Many chemicals will continue to
    damage animals and plants and poison food and water for years or
    decades.  Therefore, it is essential that chemical pollution of the
    environment be prevented at its source -- i.e., wherever chemicals are
    manufactured or used.  Good occupational hygiene principles should
    always be applied when using or handling any chemicals at work. 
    Chemicals must be controlled not simply in order to ensure compliance
    with government standards (exposure limits, etc.; see Chapter 7), but
    to prevent chemical contamination -- to the maximum extent possible --
    of the general environment.  In the first instance, this means
    judicious use of less toxic and/or more readily degradable chemicals

    and the use of more selective pesticides.  Chemical processes should
    be enclosed as far as possible to prevent release of chemicals as
    dust, fumes or gas.  Dust, fumes and gas that are generated during a
    process such as grinding or welding should be captured by local
    exhaust ventilation.  Contaminated air from such processes, together
    with contaminated air from ventilation of closed systems and general
    ventilation, should not be allowed to escape to the atmosphere inside
    the workplace, or outside, without first having had the contamination
    removed.  Some methods and principles for the prevention of
    environmental chemical pollution are given in Chapter 4 of this Manual
    (see sections on Storage, Spillage and Disposal).


    Most HSGs contain a Summary of Chemical Safety Information or an ICSC
    that summarizes information and advice on the relevant chemical.  It
    is designed for easy, quick reference for health workers concerned
    with, and users of, chemicals.  It should be displayed near entrances
    to areas where exposure to the chemical in question could potentially
    occur and, if possible, on processing equipment and containers.

    A sample is given below; the terms used are defined in Chapters 1 and
    2 of this Manual.  All persons potentially exposed to chemicals should
    have the instructions on the relevant ICSCs clearly explained to them.

    1,4-DIOXANE  ICSC: 0041
    1,4-Diethylene dioxide
    Molecular mass: 88.1

    FIGURE 51

    CAS #    123-91-1
    RTECS #  JG8225000
    ICSC #   0041
    ON #     1165
    EC #     603-024-00-5


    HAZARDS/      ACTIVE HAZARDS/                                                    FIRST AID/
    EXPOSURE      SYMPTOMS                        PREVENTION                         FIRE FIGHTING

    FIRE          Highly flammable.               NO open flames, NO sparks,         Powder, alcohol-resistant
                                                  and NO smoking. NO contact         foam, water spray, carbon
                                                  with strong oxidants. NO           dioxide.
                                                  contact with hot surfaces.


    EXPLOSION     Vapour/air mixtures are         Closed system, ventilation,        In case of fire: keep drums,
                  explosive. Risk of fire and     explosion-proof electrical         etc., cool by spraying with
                  explosion on contact with       equipment and lighting.            water.
                  incompatible materials: see     Prevent build-up of
                  Chemical Dangers.               electrostatic charges (e.g.,
                                                  by grounding) (see Notes).

    EXPOSURE                                      AVOID ALL CONTACT!

    INHALATION    Headache. Nausea. Cough. Sore   Ventilation, local exhaust,        Fresh air, rest. Refer for
                  throat. Abdominal pain.         or breathing protection.           medical attention.
                  Dizziness. Drowsiness.
                  Vomiting. Unconsciousness.

    SKIN          MAY BE ABSORBED! Redness.       Protective gloves. Protective      Remove contaminated clothes.
                                                  Clothing.                          Rinse skin with plenty of
                                                                                     water or shower.

    EYES          Redness. Pain. Watery eyes.     Face shield or eye protection      First rinse with plenty of
                                                  in combination with breathing      water for several minutes
                                                  protection.                        (remove contact lenses if
                                                                                     easily possible), then take
                                                                                     to a doctor.

    INGESTION     (further see Inhalation).       Do not eat, drink, or smoke        Rinse mouth. Refer for
                                                  during work.                       medical attention.


    SPILLAGE DISPOSAL                          STORAGE                                    PACKAGING & LABELLING

    Collect Leaking and spilled liquid in      Fireproof. Separated from strong           Airtight.
    sealable containers as far as              oxidants, strong acids. Cool. Dry.
    possible. Wash away reminder with          Keep in the dark. Store only if            F symbol
    plenty of water (extra personal            stabilized.                                Xn symbol
    protection: complete protective
    clothing including self-contained                                                     R: 11-19-36/37-40
    breathing apparatus).                                                                 S: 16-36/37

                                                                                          UN Hazard Class: 3
                                                                                          UN Packing Group: II

    ICSC: 0041 1.1                    Prepared in the context of cooperation between the International Programme on
                                      Chemical Safety % the Commission of the European Communities (C) IPCS CEC 1993

                  PHYSICAL STATE; APPEARANCE:                     INHALATION RISK:

                  COLOURLESS LIQUID, WITH CHARACTERISTIC ODOUR.   A harmful contamination of the air can be
                                                                  reached rather quickly on evaporation of this
    IMPORTANT     PHYSICAL DANGERS:                               substance at 20C on spraying much faster.
                  The vapour is heavier than air and may travel   EFFECTS OF SHORT-TERM EXPOSURE:
                  along the ground; distant ignition possible.
                  As a result of flow, agitation. etc.,           The substance irritates the eyes and the
                  electrostatic charges can be generated.         respiratory tract. The substance may cause
                                                                  effects on the central nervous system, Liver
                  CHEMICAL DANGERS:                               and kidneys. Exposure to high vapour
                                                                  concentrations my result in unconsciousness.
                  The substance can form explosive peroxides.
                  Reacts vigorously with strong oxidants and      EFFECTS OF LONG-TERN OR REPEATED EXPOSURE:
                  concentrated strong acids. Reacts explosively
                  with some catalysts (e.g., Raney-nickel above   The Liquid defats the skin. This substance is
                  210C). Attacks many plastics.                  probably carcinogenic to humans.



                  TLV: 25 ppm; 90 mg/m3 (as TWA) (skin)
                       (ACGIH 1992-1993).

                  ROUTES OF EXPOSURE:

                  The substance can be absorbed into the body by
                  inhalation of this vapour and through the skin.

    PHYSICAL      Boiling point:                      101C       Flash point:                         12C
    PROPERTIES    Melting point:                      12C        Auto-ignition temperature:           180C
                  Relative density (water = 1):       1.03        Explosive limits, vol% in air:       2-22.5
                  Solubility in water:                Miscible    Octanol/water partition coefficient
                  Vapour pressure, kPa at 20C:       4.1         as log Pow:                          -0.42
                  Relative vapour density (air = 1):  3.0
                  Relative density of the vapour/
                  air-mixture at 20C (air = 1):      1.08



    Use of alcoholic beverages enhances the harmful effect.
    Depending on the degree of exposure, periodic medical examination is indicated.
    The odour warning when the exposure limit value is exceeded is insufficient.
    Check for peroxides prior to distillation; render harmless if positive.

    EXPLOSION/PREVENTION: Do NOT use compressed air for filling, discharging, or handling. Use non-sparking handtools.

    Transport Emergency Card: TEC (R)-546
    NFPA Code: H2; F3; R1



    ICSC:  0041  1.1                                (C) IPCS, CEC, 1993                                1,4-DIOXANE

    Chapter 7 of the HSG outlines the regulations pertaining to particular
    chemicals that apply in certain countries.  Restrictions and safety
    precautions may operate in some of the countries where a certain
    chemical is registered.  A number of standards may be listed in the
    HSGs, as requirements sometimes vary between countries.

    One of the standards that most workers will come across in the
    workplace is the exposure limit, so this term is discussed in detail

    7.1  Exposure limits

    The term exposure limit was introduced by the ILO in 1977.  It is a
    general expression that embraces the various words currently used to
    refer to air quality limit values in the workplace and which are
    referred to in the HSG (see Fig. 51).

    7.1.1    Threshold limit value

    The term threshold limit value (TLV), used by the American Conference
    of Governmental Industrial Hygienists, refers to the amount of a
    substance found in workplace air to which it is believed nearly all
    workers may be repeatedly exposed day after day without adverse
    effect.  Because of wide variation in individual susceptibility,
    however, a small percentage of workers may experience discomfort from
    some substances at or below the threshold limit value.  A smaller
    percentage may be more seriously affected by aggravation of a
    pre-existing condition or by development of an occupational illness.

    Threshold limit values may be expressed as a Time-weighted Average
    (TLV-TWA), i.e. an average concentration for a normal eight-hour
    working day and a 40-hour working week; or a Short-term Exposure
    Limit (TLV-STEL), which is a 15-minute time-weighted average
    exposure that should not be exceeded at any time during a working day
    even if the eight-hour time-weighted average is within the TLV. 
    Exposures at the STEL should not exceed 15 minutes in duration and
    should not be repeated more than four times each day; there should be
    at least 60 minutes between successive exposures at the STEL.  The
    STEL values are useful for protecting against the health effects of
    fast-acting substances such as solvents.  A ceiling value -- i.e. an
    air concentration of a chemical that should not be exceeded for even
    an instant -- is often given for chemicals that affect health after
    only a very short exposure.  This applies to chemicals that are
    capable of producing severe irritation, lung oedema (fluid in the
    lungs) or an allergic sensitization.


    Exposure limit values

    Medium  Specification    Country/            Exposure limit description               Value           Effective
                             organization                                                                 date

    AIR     Occupational     Australia           Threshold limit value (TWA)              19 mg/m3        1983
                             Germany, Federal    Maximum worksite concentration (TWA)     19 mg/m3        1985
                             Republic of         Short-term exposure limit (5-min)        38 mg/m3        1985
                             Hungary             Maximum allowable concentration (TWA)    5 mg/m3         1978
                                                 Short-term exposure limit (30-min)       10 mg/m3        1978
                             Japan               Maximum allowable concentration (TWA)    19 mg/m3        1981
                             Sweden              Highest limit value (TWA)                4 mg/m3 b       1985
                                                 Short-term exposure limit (15-min TWA)   8 mg/m3         1985
                             USA (OSHA)          Permissible exposure level (TWA)         19 mg/m3        1974
                             USA (ACGIH)         Threshold limit value (TWA)              19 mg/m3        1984
                                                 Short-term exposure limit (TWA)          38 mg/m3        1984
                             USSR                Ceiling value                            0.3 mg/m3       1977

    AIR     Ambient          Czechoslovakia      Maximum allowable concentration
                                                 average per day                          0.01 mg/m3      1981
                                                 average per 0.5 h                        0.01 mg/m3      1981
                             USSR                Maximum allowable concentration
                                                 average per day                          0.003 mg/m3     1984
                                                 once per day                             0.01 mg/m3      1984

    Figure 51. Exposure limit values (from HSG 88: Phenol)

    7.1.2  Maximum allowable concentration

    The term maximum allowable concentration (MAC) is used widely in the
    former Soviet Union and Central and Eastern European countries, the
    Netherlands and Germany.  In the former Soviet Union, MAC is defined
    as that concentration of a harmful substance in the air of the
    workplace which, in the case of daily exposure at work for eight
    hours, throughout a worker's entire working life, will not cause any
    disease or deviation from a normal state of health to that worker or
    his or her offspring, detectable by current methods of investigation,
    whether during the work itself or in the long term.

    7.1.3  Other terms for occupational exposure limits

    Just as the regulations and guidelines of countries are subject to
    change, so too is the terminology concerning exposure limits. 
    Although TLV and MAC are terms that are well known because of their
    wide usage over a long time, some countries have developed their own
    terminology or evolved their own standards, criteria and methods for
    determining exposure limits.  These vary in practice between the
    stringent concept of MAC and the more elastic approach of TLV, which
    makes allowances for reversible clinical changes.

    Some of the expressions currently used in addition to TLV and MAC and
    that are used in the HSGs include:

    *    Maximum permissible concentration (MPC), used in Argentina,
         Finland and Poland, among others; this term is also used in
         relation to a chemical's concentration in drinking-water in
         several countries, including Japan, Germany and the USA.

    *    Permissible exposure limit (PEL), used in the United Kingdom
         and by the US Occupational Safety and Health Administration, etc.

    *    Technical guiding concentration (TRK) is a term applied in

    Information on the methodology, scientific basis and any other aspects
    related to the establishment of exposure limits should be requested
    from the relevant national bodies of your country.

    While the terms used above may give the impression that exposure to
    chemicals below their exposure limit is harmless and without adverse
    health effects, it should be stated that exposure limits are
    approximate guidelines only as to what is safe and what is dangerous. 
    They are not necessarily safe limits.

    Factors that must be taken into account when applying exposure limits
    and other environmental control values include:

    *    Length of work shift and working week -- Exposure limit values
         assume that workers will be exposed to chemicals in the workplace
         only for eight hours per day, five days per week.  If each shift
         is longer than eight hours, or if more than 40 hours are worked
         in each week, the exposure limit values must be lowered. If
         workers live near their workplace, environmental pollution may
         add to exposure levels.  This should be taken into account when
         assessing exposure risk.

    *    Environmental conditions -- Environmental or physical factors
         such as heat, ultraviolet and ionizing radiation and humidity may
         place added stress on the body. The effects of exposure at a
         threshold limit may therefore be altered. Most of these stresses
         act adversely to increase the toxic response of a substance.  The
         safety factors for most substances do not permit significant

    *    Combined exposures -- The combined health effects of exposure to
         two or more chemicals that produce similar effects are often much
         greater than the additive effects of separate exposure to each of
         the chemicals.  This is known as synergism (see Chapter 2). 
         Synergism may also occur if workers are taking prescribed or
         non-prescribed drugs.  Many prescribed drugs such as
         contraceptive pills or sleeping tablets can exacerbate the
         negative health effects of workplace chemicals.  Similarly,
         alcohol can worsen the effects of solvents.  A well-known example
         of synergism is the relationship between tobacco smoking and
         asbestos exposure. Smokers who work with asbestos have been shown
         to have a probability of dying from lung cancer that is greater
         than the sum of the probabilities arising from smoking and from
         working with asbestos.

         Chemicals that are handled in the workplace may not be pure, and
         the contaminants may pose a greater health hazard than the
         chemical itself.  This is often overlooked when exposure limits
         are set.

    *    Workload -- Heavy workloads may increase the absorption of
         chemicals present in the workplace air.  When performing heavy
         physical work, a worker will breathe faster and more deeply. 
         Therefore, more air (containing chemicals) will pass through the
         worker's lungs.  It has been estimated that for equal
         concentrations of a substance, the amount taken in by the lungs
         could vary from one work situation to another by as much as

    *    Reproductive effects -- Although greater efforts have been made
         recently to set exposure limits sufficiently low to protect
         workers and their offspring from reproductive health effects (see
         Chapter 2), knowledge in this area is still quite limited, and
         most exposure limits do not take reproductive hazards into

    *    Route of entry -- Although inhalation of airborne dust or
         droplets is the most common way in which chemicals enter the
         body, some chemicals for which exposure limits have been set may
         also enter by other routes such as the skin.  In these cases, a
         warning of this hazard appears in the HSG.

    *    Carcinogens -- Exposure to carcinogens should be kept as "low as
         is technically feasible".  This means that all available control
         methods (i.e. substitution, enclosure, ventilation and personal
         protective equipment when absolutely essential) should be used to
         keep worker exposure to the carcinogenic chemical to an absolute

    *    Average worker -- Exposure limits are set to protect the average
         worker from the effects of chemicals.  As most exposure limits
         have been developed in the industrialized countries, this average
         worker is often presumed to be a healthy, well-nourished, white
         male.  The clearest example of the average worker problem is that
         of the female worker, who may react quite differently to exposure
         to chemicals, such as solvents, because of her greater degree of
         body fat. Women's higher risk of reproductive complications
         should also be taken into account when exposure limits are set.

    *    Insufficient and sometimes biased information -- Many exposure
         limits have been set without sufficient information.  For
         example, very few chemicals have been adequately tested over a
         long period of time for their contribution to illnesses such as
         heart disease and cancer or to genetic effects.  Moreover, some
         exposure limits are based largely on information developed and
         evaluated by the chemical industry.  In general, workers and
         their representatives have little or no input into setting
         exposure limits, even though they are most at risk.

    7.1.4  Health-based exposure limits

    If the protection of workers were the only consideration, most
    exposure limits would be much more stringent.  This is the case with
    the WHO's "Recommended health-based occupational exposure limits",
    which are based on toxicity data and their relevance to the protection
    of workers' health.  Recommended health-based occupational exposure

    limits should not be seen as absolute levels above which effects will
    occur and below which they will not occur.  They are levels above
    which the probability that adverse health effects will occur starts to
    increase, and below which this probability is very low.  Recommended
    health-based exposure limits already exist for some metals, solvents,
    pesticides, vegetable dusts and irritant gases (published in the WHO
    Technical Report Series).  These WHO health-based limits are generally
    stricter and more protective than national safety standards.  This is
    because they are based on health considerations only.  They may be
    seen as the "ultimate goal" for standards.  In each country they can
    be used by representatives of government, employers and workers to set
    their own limits, taking into account other factors such as
    socioeconomic and technological constraints.

    7.1.5  Exposure limits for food products

    Many of the HSGs are for pesticide chemicals. In addition to
    occupational exposure during manufacture and use of these products,
    exposure may occur in the form of residues in and on food products. 
    The issue of whether any such residues pose a threat to health is
    therefore of some concern.

    Many governments and international bodies such as WHO and the Food and
    Agriculture Organization of the United Nations (FAO) have developed
    different standards and/or legally established limits to control
    exposure to and ingestion of residues (see Fig. 52).

    *    Maximum residue limit (MRL) is the maximum concentration of a
         pesticide residue (expressed in mg/kg) that is legally permitted
         or recognized as acceptable in or on a food, an agricultural
         commodity or animal feed.

    *    Acceptable daily intake (ADI) is the daily intake of a chemical
         (expressed in mg/kg of body weight) that, during an entire
         lifetime, appears to be without appreciable risk to the health of
         the consumer on the basis of all known facts at the time of the
         evaluation of the chemical. ADIs are established internationally
         by the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) and, in
         the case of many countries, by the national regulatory
         authorities (see Fig. 52).

    7.2  Specific restrictions

    A chemical may have special restrictions imposed on its use in any
    country, mainly as a result of concern about its effects on health or
    the environment.  However, regulatory decisions taken in a certain
    country can only be fully understood in the framework of the

    legislation of that country.  It does not therefore follow that a
    banned or restricted chemical in one country will be banned, or have
    the same restrictions imposed on it in other countries.


    Figure 52.  Exposure limits for food products in some countries
                (from HSG 73: Rotenone)


    7.1  Exposure limit values

    The Joint FAO/WHO Meeting on Pesticide Residues (JMPR) has not
    reviewed the compound to establish an ADI.  A threshold limit value,
    time weighted average (TWA) for rotenone of 5 mg/m3 has been
    recommended by the US ACGIH and adopted by several countries.

    Some exposure limits for food products are given in Table 1.

    Table 1.  Exposure limits for food products in some countries


    Country      Food product       Exposure        Value    Effective
                                      limit        (mg/kg)     date

    Austria      All products                       0.05         1988

    Germany      All products      Maximum           0.1         1990
                 of plant origin   residue limit

    France       Fruits and                         0.05         1989

    Italy        Specified                          0.04         1985
                 fruits and

    Netherlands  All products                       0.05         1988

    Asbestos, for instance, is a known human carcinogen -- it causes lung
    cancer -- and has been effectively banned in Sweden and Denmark, but
    its use is still permitted elsewhere.  Some countries may have
    restricted the use of certain types of asbestos (e.g. crocidolite or
    blue asbestos) or certain processes (e.g. spraying of asbestos).  In
    other countries the use of asbestos is actively encouraged,
    particularly for building and for piping.  In all countries, its
    health effects will be the same, but for various reasons -- mainly
    economic or political -- some countries see fit to allow its continued

    If you suspect that you may be working with an imported dangerous
    chemical, it would be worthwhile finding out what restrictions are
    imposed on the chemical in the country of origin or in other
    countries.  The HSGs outline such restrictions (see Fig. 53).

    7.3  Labelling, packaging and transport

    Labelling of a chemical to warn of potential health hazards is based
    on classification.  Classification is concerned with both acute and
    long-term effects of substances, not only with respect to systemic
    toxicity (carcinogenicity, mutagenicity and teratogenicity), but also
    with respect to allergic qualities and local effects on the skin and
    eyes, as well as fire and explosion risks.

    Some of the more commonly used terms for the purposes of
    classification include harmful, toxic, very toxic, irritant,
    corrosive, oxidizing material, etc.  For substances that have
    carcinogenic, mutagenic, allergenic or other subacute or chronic
    effects, the classification of very toxic, toxic or harmful should be
    used according to the magnitude of these effects.

    Appropriate symbols are used to provide immediate visual
    identification of the general nature and degree of hazard (see
    Fig. 54).  Label sizes, shapes, colours and borders will be specified,
    and the HSG outlines the appropriate specifications (see Fig. 55). 
    This is especially important if chemicals are to be transported.


    Figure 53.  Restrictions imposed on chemical use in various countries
                (from HSG 19: Pentachlorophenol)

    Specific restrictions

    The use of pentachlorophenol has been more and more restricted during
    the last few years as a result of the increasing concern about the
    potential health and environmental hazards of PCP and its impurities.

    To mention a few:

    *    Sweden banned all use of PCP in 1977 and the Federal Republic of
         Germany banned all use in 1987;

    *    the USA cancelled its registration for herbicidal and
         anti-microbial use and for the preservation of wood in contact
         with food, feed, domestic animals, and livestock.  The sale and
         use of PCP are restricted to certified applicators;

    *    the agricultural use of PCP has been suspended or restricted in,
         among others, Canada, Denmark, German Democratic Republic, and

    *    Canada and the Netherlands have suspended its use for indoor
         wood treatment.

    In addition to warning symbols, standard risk and safety phrases
    should also be used to describe in detail the nature of the risk and
    appropriate safety measures.  Thus, a complete label should give the
    name of the substance (including the internationally recognized
    chemical name), the name and address of the manufacturer, distributor
    or importer and whatever symbols and risk and safety phrases that may
    be appropriate.

    FIGURE 54


    Figure 55.  Labelling requirements (from HSG 9: Isobutanol)

    FIGURE 55

    The European Community legislation requires labelling as a
    dangerous substance using the symbol:

    FIGURE 55

    The label must read: flammable - harmful by inhalation; keep
    away from sources of ignition - no smoking.

    The European Community legislation on labelling of solvent
    preparations classifies isobutanol in class  II d for the
    purpose of determining the label for preparations containing
    isobutanol and other active ingredients (1980).

    The criteria for classification are too complex for inclusion here. 
    In addition, there are many different classification and labelling
    systems that depend on the user, i.e. the manufacturer, the shippers
    or the employers, all of whom will have different areas of interest --
    consumer products, shipping or environmental regulations or employee
    protection.  All of these are regulated by different national and
    international agencies (national departments of transportation,
    environmental protection agencies), local ordinances, the United
    Nations Committee of Experts on the Transport of Dangerous Goods and
    the International Maritime Organization.

    It is generally agreed that proper application -- and therefore proper
    interpretation -- of labelling of chemicals is often a difficult and
    frustrating task.  End-users are therefore advised to contact their
    trade union or appropriate national or international association for
    basic information on specific labelling.


    The information available to workers (and the general public) about
    the health and safety effects of chemicals is often inadequate.  Some
    suggestions for obtaining further information are given below.

    I.  Identify and list the chemicals used in your workplace

    II.  Approach your employer for full information

    It is the employer's responsibility to provide employees with full
    health and safety information for all chemicals and chemical processes
    used in a workplace.  You should always ask your employer for health
    and safety information as a first step.

    You may wish to do this through your trade union or through the
    workplace health and safety committee, if one exists.  Always put your
    requests in writing.  If the employer's reply is inadequate, you
    should inform your trade union.

    III.  Contact the chemical manufacturer or supplier

    If your employer is unwilling or unable to provide the requested
    information, it will be necessary to write to the chemical
    manufacturer or supplier.  Its name and address usually appear on the
    label of the chemical container.

    The manufacturer's or supplier's reply should include the following

    *    the manufacturer's trade name for the chemical;
    *    any code numbers that appear on the label;
    *    the proper chemical or generic names of the chemical, if
         available; and
    *    a brief description of how the chemical is used.

    IV.  Contact your government's Department of Occupational Health
         and Safety

    The government department responsible for occupational health and
    safety may provide an information service that can assist you in
    obtaining further information about particular chemicals.

    V.  Contact your trade union

    There may be services concerned with the safety of chemicals run by
    public interest groups or the trade union movement.

    VI.  Search for the information yourself

    Many large public libraries and most university or technical college
    libraries hold reference books on occupational health and safety and
    the hazards of chemicals.  Ask the librarian for help.  The following
    books may be particularly useful:

    *    IPCS Health and Safety Guides;
    *    IPCS Environmental Health Criteria (more detailed scientific
         information on each chemical);
    *    ILO Encyclopaedia of Occupational Health and Safety;
    *    Reports from the International Register of Potentially Toxic
         Chemicals (IRPTC/UNEP);
    *    Dangerous Properties of Industrial Materials -- Author: I. Sax;
    *    Patty's Industrial Hygiene and Toxicology;
    *    UN "Consolidated list of products whose consumption and/or sale
         have been banned, withdrawn, severely restricted or not approved
         by governments".  Fourth ed. New York, United Nations Department
         of International Economic and Social Affairs, 1991;
    *    ILO Convention No. 170 and Recommendation No. 177 on Safety in
         the Use of Chemicals at Work;
    *    ILO Convention No. 174 and Recommendation No. 181 on Prevention
         of Major Industrial Accidents;
    *    ILO Codes of Practice on "Safety in the Use of Chemicals at Work"
         and "Prevention of Major Industrial Accidents"; and
    *    ILO.  Safety and health in the use of chemicals at work: a
         training manual.

    Information on toxic effects of chemicals can also be obtained from
    several databases, some of which are available on electronic media
    such as CD-ROM.  Many national and international trade unions have
    access to such electronic information and can readily respond to
    requests from affiliated unions and members.

    See Also:
       Toxicological Abbreviations