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    IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
    Health and Safety Guide No. 59

     n-HEXANE
    HEALTH AND SAFETY GUIDE






    UNITED NATIONS ENVIRONMENT PROGRAMME

    INTERNATIONAL LABOUR ORGANISATION

    WORLD HEALTH ORGANIZATION




    WORLD HEALTH ORGANIZATION, GENEVA 1991

    This is a companion volume to Environmental Health Criteria 122:
     n-Hexane

    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)

    This report contains the collective views of an international group of
    experts and does not necessarily represent the decisions or the stated
    policy of the United Nations Environment Programme, the International
    Labour Organisation, or the World Health Organization

    WHO Library Cataloguing in Publication Data

    Health and safety guide for n-Hexane

    (Health and safety guide ; no. 59

    1.Hexanes - standards  I.Series

    ISBN 92 4 151059 5          (NLM Classification: QV 633)
    ISSN 0259-7268

    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 available.

    (c) World Health Organization 1991

    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
    boundaries.

    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.

    CONTENTS

    INTRODUCTION

    1. PRODUCT IDENTITY AND USES
         1.1. Identity
         1.2. Physical and chemical properties
         1.3. Analytical methods
         1.4. Uses

    2. SUMMARY AND EVALUATION
         2.1. Human exposure to  n-hexane
         2.2. Uptake, metabolism, and excretion
         2.3. Effects on animals
         2.4. Effects on human beings

    3. CONCLUSIONS AND RECOMMENDATIONS

    4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY
         ACTION
         4.1. Main human health hazards, prevention and protection,
               first aid
               4.1.1. Advice to physicians
                       4.1.1.1   Symptoms of poisoning
                       4.1.1.2   Medical advice
               4.1.2. Health surveillance advice
         4.2. Safety in use
         4.3. Explosion and fire hazards
               4.3.1. Flammability and explosion
               4.3.2. Fire
         4.4. Storage
         4.5. Transport

         4.6. Spillage and disposal
               4.6.1. Spillage
               4.6.2. Disposal

    5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    6. SUMMARY OF CHEMICAL SAFETY INFORMATION

    7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
         7.1. Regulation of emissions
         7.2. Regulation of food
         7.3. Exposure limit values
         7.4. Labelling and packaging

    BIBLIOGRAPHY
    

    INTRODUCTION

    The Environmental Health Criteria (EHC) documents produced by the
    International Programme on Chemical Safety include an assessment of
    the effects on the environment and on human health of exposure to a
    chemical or combination of chemicals, or physical or biological
    agents. They also provide guidelines for setting exposure limits.

    The purpose of a Health and Safety Guide is to facilitate the
    application of these guidelines in national chemical safety
    programmes. The first three sections of a Health and Safety Guide
    highlight the relevant technical information in the corresponding EHC.
    Section 4 includes advice on preventive and protective measures and
    emergency action; health workers should be thoroughly familiar with
    the medical information to ensure that they can act efficiently in an
    emergency. Within the Guide is a Summary of Chemical Safety
    Information which should be readily available, and should be clearly
    explained, to all who could come into contact with the chemical. The
    section on regulatory information has been extracted from the legal
    file of the International Register of Potentially Toxic Chemicals
    (IRPTC) and from other United Nations sources.

    The target readership includes occupational health services, those in
    ministries, governmental agencies, industry, and trade unions who are
    involved in the safe use of chemicals and the avoidance of
    environmental health hazards, and those wanting more information on
    this topic. An attempt has been made to use only terms that will be
    familiar to the intended user. However, sections 1 and 2 inevitably
    contain some technical terms. A bibliography has been included for
    readers who require further background information.

    Revision of the information in this Guide will take place in due
    course, and the eventual aim is to use standardized terminology.
    Comments on any difficulties encountered in using the Guide would be
    very helpful and should be addressed to:

    The Manager
    International Programme on Chemical Safety
    Division of Environmental Health
    World Health Organization
    1211 Geneva 27
    Switzerland

    THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING POINT
    TO A COMPREHENSIVE HEALTH AND SALTY PROGRAMME

    1.  PRODUCT IDENTITY AND USES

    1.1  Identity

    Common name:             n-hexane (normal hexane)

    Chemical structure:         H   H   H   H   H   H
                                '   '   '   '   '   '
                            H - C - C - C - C - C - C - H
                                '   '   '   '   '   '
                                H   H   H   H   H   H

    Chemical formula:       C6H14

    Relative molecular
    mass:                   86.18

    CAS registry
    number:                 110-54-3

    RTECS registry
    number:                 MN9275000

    Purity:                 Purified material contains 95-99.5%  n-hexane
                            with small amounts of other hexane isomers as
                            impurities. Commercial hexane contains a
                            mixture of hexane isomers ( n-hexane, 2-methyl
                            pentane, 3-methyl pentane, 2,3-dimethyl
                            butane), cyclohexane, methyl cyclopentane,
                            pentane and heptane isomers, acetone, methyl
                            ethyl ketone, dichloromethane, and
                            trichloroethylene. Phthalate esters, adipate
                            esters, and organophosphorous compounds have
                            been identified as minor components. The
                             n-hexane content of commercial hexane varies
                            from 20 to 80%.

    1.2  Physical and Chemical Properties

     n-Hexane is a colourless, highly volatile liquid that is poorly
    soluble in water and is miscible with most organic solvents.
    Commercial hexane has been reported as having a slightly disagreeable
    odour; the odour threshold is approximately 210 mg/m3 (60 ppm).

    Some physical and chemical properties of  n-hexane are given in the
    Summary of Chemical Safety Information (section 6).

     n-Hexane is dangerous when exposed to heat, flame, or oxidizing
    materials.

    1.3  Analytical Methods

    Gas chromatography combined with flame ionization or mass spectroscopy
    is a suitable technique for the determination of  n-hexane in air,
    liquids, or biological samples. Metabolites of  n-hexane can be
    determined using high performance liquid chromatography.

    1.4  Uses

     n-Hexane is most often used commercially in the form of a mixture
    with other hexane isomers and other solvents. Hexanes are mainly used:
    for the extraction of vegetable oil from soybeans, flaxseed, peanuts,
    safflower, corn germ, and cottonseed; as solvents in various products,
    including the polyolefins; and as solvents in industrial processes,
    such as rubber polymerization.  n-Hexane is also used: as a
    cleaning agent; as a laboratory chemical; in food processing; in
    low-temperature thermometers; and in other products (e.g., adhesives
    and lacquers).

    2.  SUMMARY AND EVALUATION

    2.1  Human Exposure to n-Hexane

     n-Hexane can be isolated from natural gas and crude oil. It is used
    in food processing, including the extraction of vegetable oils, and as
    a solvent in various products and processes. In the atmosphere, the
    half-life of  n-hexane is estimated to be less than 2 days.

    Occupational exposure to  n-hexane is mainly via inhalation, though
    skin and eye contamination may also occur.

    2.2  Uptake, Metabolism, and Excretion

    In mammals,  n-hexane is absorbed rapidly through the lungs and is
    distributed widely in the adult body, as well as to fetal tissues.
    Dermal absorption is limited.  n-Hexane undergoes oxidative
    metabolism to form a number of metabolites, including 2,5-hexanedione,
    which is thought to be the neurotoxic agent. Particularly high levels
    of  n-hexane and 2,5-hexanedione can be found in the sciatic nerve of
    exposed rats. Most  n-hexane is excreted unchanged in exhaled air and
    as metabolites in exhaled air and urine.

    2.3  Effects on Animals

    The acute toxicity of  n-hexane is low, with reported LD50 values
    in the range of 15-30 g/kg and an LC50 (1-h) of 271040 mg/m3.
    Testicular toxicity and neurotoxicity, both peripheral and central,
    appear to be the principal toxic effects of repeated  n-hexane
    exposure in rats. Irreversible testicular lesions were seen in rats
    exposed to 17 600 mg/m3 (5000 ppm) for 16 h/day, 6 days/week, for 2
    weeks. The metabolite 2,5-hexanedione also produced testicular
    toxicity following oral exposure in rats.

    The neurotoxic effect  of n-hexane is characterized clinically by
    hind limb weakness, which can progress to paralysis. Clinical signs
    have been seen in rats after a 10-week exposure to 560 mg/m3
    (3000 ppm) for 12 h/day and 7 days/week. Axonal swellings have been
    observed in hind limb nerves, and in the brain and spinal cord, prior
    to the appearance of hind limb weakness. A no-observed-effect level
    (NOEL) was not established in continuous, 6-month, inhalation studies;
    nerve lesions were seen at  n-hexane levels of 1760 mg/m3 (500 ppm)
    or more.  n-Hexane-induced neurotoxicity can be enhanced by combined
    exposure to methyl ethyl ketone, methyl isobutyl ketone, and lead
    acetate. The lungs, kidneys, and liver have also been reported to be
    affected by the inhalation of  n-hexane at relatively high
    concentrations.

    Severe microscopic lesions were noted in the skin following the dermal
    application of  n-hexane, under occlusive dressings, for short
    periods. Prolonged exposure to 10 560 mg  n-hexane/m3 (3000 ppm)
    caused conjunctival irritation in the eyes of rats and ocular
    irritation in rabbits.

    There is no evidence of embryotoxicity or teratogenicity in rats or
    mice, but these aspects have not been studied adequately.

    The carcinogenic potential of  n-hexane has also not been studied
    adequately. The results of assays for point mutations and for DNA
    repair in bacterial and mammalian cells were negative, though there is
    evidence for the production of chromosomal aberrations  in vitro and
     in vivo. The results were also negative in a limited study on skin
    rumour formation in mice treated with  n-hexane.

    2.4  Effects on Human Beings

    The available data suggest that the acute toxicity of  n-hexane is
    low. Single exposures to  n-hexane can cause vertigo, giddiness, and
    drowsiness.  n-Hexane is a mild skin irritant that causes transient
    erythema when in short-term contact with skin; it can also irritate
    the eyes. There are no reports of skin sensitization.

    A number of studies have linked occupational exposure to  n-hexane
    with the incidence of peripheral neuropathy, though adequate exposure
    data have usually been lacking. Exposure to air concentrations of
     n-hexane reported to have varied from 106 mg/m (30 ppm) to 8800 mg/m3
    (2500 ppm), has been associated with neuropathy, but the previous
    exposures of these cases may have been higher. Mild subclinical
    neurological effects have been reported from cross-sectional studies
    on workers exposed to 70-352 mg  n-hexane/m (20-100 ppm), but no
    cases of clinically overt peripheral neuropathy were identified at
    these concentrations.

    Thus, while there is evidence for an effect of  n-hexane on the
    central nervous system, it is not possible to relate this to defined
    exposure levels, on the basis of the available information.

    3.  CONCLUSIONS AND RECOMMENDATIONS

     n-Hexane is unlikely to present hazards for the environment, except
    in the case of major spills or discharges, where there could be
    transient local effects.

    On the information available, it is concluded that workers who come
    into contact with  n-hexane will not be at risk, providing exposure
    levels in the workplace are kept within the prescribed control limits.

    Because of the mild irritant effects of  n-hexane and the possibility
    of skin absorption, contact with the skin and eyes should be avoided.

    4.  HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION

    4.1   Main Human Health Hazards, Prevention and Protection, First Aid

    The principal adverse effect of exposure to  n-hexane is
    neurotoxicity. It is therefore essential that appropriate precautions
    should be taken during handling and use.

    4.1.1  Advice to physicians

    4.1.1.1  Symptoms of poisoning

    A single exposure to  n-hexane can produce vertigo, giddiness, and
    drowsiness. Longer-term exposures can lead to peripheral neuropathy,
    the first signs of which are symmetrical paraesthesia and weakness,
    particularly in the lower extremities. Headache, anorexia, dizziness,
    and sensory impairment may precede, or accompany, the neuropathy. Most
    patients show diminished reflexes; there may be loss of body weight.

    4.1.1.2  Medical advice

    In case of poisoning by  n-hexane, the nearest Poisons Information
    Centre should be contacted for detailed advice on treatment.
    Information on first aid is provided in the Summary of Chemical Safety
    Information (section 6). If breathing has stopped, artificial
    respiration and oxygen should be applied. Following ingestion,
    vomiting should not be induced, because of the danger of aspiration
    into the lungs. Gastric lavage should only be given where aspiration
    into the lungs can be avoided by the use of a cuffed endotracheal
    tube.

    4.1.2  Health surveillance advice

    A pre-employment medical examination is advisable for workers who will
    be regularly exposed to  n-hexane. In routine medical checks,
    emphasis should be placed on examination of the central and peripheral
    nervous system and male reproductive function.

    4.2  Safety In Use

    Atmospheric levels should be kept as low as practicable, and certainly
    below the recommended occupational exposure limits, by suitably
    designed work processes and by engineering controls, such as local
    exhaust ventilation. Protective clothing, resistant to permeation by
     n-hexane, and approved, effective, respiratory protection should be
    readily available for use in enclosed spaces, in case of emergencies,
    and for certain maintenance operations.

    4.3  Explosion and Fire Hazards

    4.3.1  Flammability and explosion

     n-Hexane is highly flammable. Adequate ventilation should be
    provided and smoking prohibited. There should be no sources of sparks
    or heat, and electrical equipment should be designed according to a
    recognized explosion-proof standard.

    4.3.2  Fire

    Flashback along a vapour trail may occur, since the vapour is heavier
    than air. Fire extinguishers containing carbon dioxide, dry chemical,
    or foam are recommended. Water sprays should not be used, since these
    may cause the fire to spread, though a water spray can be used to cool
    containers.

    4.4  Storage

    Drums should be stored in a well-ventilated area in fire-resistant
    containers. Metal containers should be electrically-grounded, when
    liquid is being transferred.

    4.5  Transport

    Comply with legal and other requirements regarding the transport of
    hazardous material. Containers should be in good condition and
    properly labelled, and should be kept in a well-ventilated place, away
    from sources of ignition.

    4.6  Spillage and Disposal

    4.6.1  Spillage

    In the event of spillage, naked flames, sparks, and heat should be
    avoided; approved, efficient, protective clothing and respirators
    should be provided. Small-scale spillage should be absorbed on paper
    towels or sawdust; sand or earth can be used for larger spills.
    Fire-fighting foam can be used in large spillages to reduce
    evaporation. If possible, liquid spills should be recovered for
    recycling.

    4.6.2  Disposal

    The International Register of Potentially Toxic Chemicals recommends:
    "Incineration, open burning, use as a boiler fuel, evaporation. Spray
    into the furnace. Incineration will become easier by mixing with a
    more flammable solvent. Care, highly inflammable, evaporate only small
    amounts. Landfill is not recommended".

    5.  HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    Industrial discharges from the manufacture, formulation, or technical
    applications of  n-hexane should be minimized and may be regulated
    (section 7). With adequate controls,  n-hexane in the environment is
    not likely to produce toxic effects on aquatic organisms, since the
    LC50 is reported to be greater than 1000 mg/litre (1000 ppm).

    It is not expected to have any marked effect on the physical
    properties of the atmosphere and its half-life in the atmosphere is
    estimated to be less than 2 days.

    6.  SUMMARY OF CHEMICAL SAFETY INFORMATION

     This summary should be easily available to all health workers
     concerned with, and users of, n-hexane. It should be displayed at, or
     treat, entrances to areas where there is potential exposure to
     n-hexane, and on processing equipment and containers. The summary
     should be translated into the appropriate language(s). All persons
     potentially exposed to the chemical should also have the instructions
     in the summary clearly explained.

     Space is available for insertion of the National Occupational
     Exposure Limit, the address and telephone number of the National
     Poison Control Centre, and local trade names.


         n-HEXANE
    Chemical formula: C6H14
    CAS registry number: 110-54-3: RTECS registry number: MN9275000
                                                                                                                                                

    PHYSICAL PROPERTIES                                                           OTHER CHARACTERISTICS
                                                                                                                                                

    Boiling point (C)                             69                             Colourless, volatile liquid; commercial
    Melting point (C)                             -95                            hexane has a slightly disagreeable odour with an
    Relative density (D420)                        0.6603                         odour threshold of approximately 210 mg/m3 (60 ppm)
    Vapour pressure (mmHg) (25C)                  150
    Relative molecular mass                        86.18
    1-Octanol/water partition
    coefficient (log Pow; 25C)                    3.6
    Solubility in water (mg/litre) (25C)          9.5
    Solubility in solvents                         soluble in most solvents
                                                   including ethanol
    Vapour density                                 2.97
    Autoignition temperature (C)                  225
    Explosive limits in air (% by volume)          1.1-7.5
    Closed-cup flash point (C)                    -21.7
                                                                                                                                                

                                                                                                                                                

    HAZARDS/SYMPTOMS                           PREVENTION AND PROTECTION                 FIRST AID
                                                                                                                                                

    Vapour/fumes

    EYES: Irritation and lacrimation;          Proper containment or efficient local     Remove from exposure; irrigate eyes for at
    discomfort, pain, red eyes, blurred        exhaust ventilation, so that breathing    least 15 minutes with a gentle flow of fresh
    vision                                     zone concentrations are below the         potable water or sterile eye irrigation fluid;
                                               occupational exposure limit; otherwise,   send to a doctor
                                               positive pressure demand, compressed
                                               air, breathing apparatus or other
                                               effective respiratory protection
                                               with full facepiece should be worn,
                                               so that complete protection of the
                                               eyes and respiratory tract is assured

    SKIN: n-Hexane can be                      Avoid skin contact, wear protective       Remove contaminated clothing immediately;
    absorbed through the skin;                 clothing resistant to permeation          the skin should be thoroughly washed with
    it may also cause dry skin or              by n-hexane                               soap and plenty of water
    inflammation

    INHALATION: Affects the nervous            Control levels in the work environment    Remove patient to fresh air and keep warm;
    system; vertigo, giddiness, drowsiness;    to within recommended exposure limit;     if breathing has stopped,. apply artificial
    long-term exposures have produced          otherwise provide respiratory             respiration; obtain medical attention
    peripheral neuropathy                      protection, such as a supplied-air
                                               respirator or self-contained, breathing
                                               apparatus

    INGESTION: Abdominal pain;                 Do not eat, drink, or smoke during        Vomiting should not be induced; keep
    nausea and, if absorbed, symptoms work     patient warm; obtain medical attention
    of nervous system effects, similar to
    those following inhalation; should
    not occur with good work practices
                                                                                                                                                

                                                                                                                                                

    HAZARDS/SYMPTOMS                           PREVENTION AND PROTECTION                 FIRST AID
                                                                                                                                                

    ENVIRONMENT: Should not                    Industrial discharges should be
    pose a risk, provided that there are       minimized and may be regulated
    adequate controls to minimize
    emissions
                                                                                                                                                

    SPILLAGE                                   STORAGE                                   FIRE AND EXPLOSION
                                                                                                                                                

    Take appropriate personal                  Store drums in a well-ventilated          Adequate ventilation should be provided
    precautions; absorb spillage on            area, in fire-resistant containers;       and there should be no sources of sparks,
    paper towels, sawdust, earth, or           metal containers should be                heat, or naked flames; flashback along a
    sand, for subsequent incineration;         electrically-grounded, when liquid        vapour trail may occur; fire extinguishers
    if possible, liquid spills should be       is being transferred                      containing carbon dioxide, dry chemical,
    recovered for recycling                                                              or foam are recommended; water sprays
                                                                                         should not be used, except to cool containers
                                                                                                                                                

    WASTE DISPOSAL                             LABELLING
                                                                                                                                                

    Waste material should be                   National Occupational Exposure            United Nations
    incinerated in an approved;                Limit:                                    Hazard Class 3.1 (flammable liquid)
    manner; disposal should not be                                                       Packaging Class II (medium danger)
    via landfill burial, or drains             National Poison Control Centre:

                                               Local trade names:
                                                                                                                                                
        7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS

    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file. A full reference to the original national document from which
    the information was extracted can be obtained from IRPTC. When no
    effective date appears in the IRPTC legal file, the year of the
    reference from which the data are taken is indicated by (r).

    The reader should be aware that regulatory decisions about chemicals,
    taken in a certain country, can only be fully understood in the
    framework of the legislation of that country The regulations and
    guidelines of all countries are subject to change and should always be
    verified with appropriate regulatory authorities before application

    7.1  Regulation of Emissions

    In the Federal Republic of Germany,  n-hexane belongs to Class III
    substances, the total emission of which (as a sum of all compounds in
    this class) must not exceed 150 mg/m3, at a mass flow of 3 kg/h. In
    the USER, the ambient air concentration of  n-hexane must not exceed
    300 mg/m3.

    7.2  Regulation of Food

    FAO/WHO have not allocated an acceptable daily intake for  n-hexane,
    but recommend that the solvent should be used only in accordance with
    good manufacturing practice, to ensure minimal residues in food.

    In the USA, cottonseed products and hop extract, modified for human
    consumption, must contain not more than 60 mg  n-hexane/kg and 25 mg
     n-hexane/kg, respectively. The latter limit also applies to specified
    food colouring agents containing  n-hexane.

    7.3  Exposure Limit Values

    Some exposure limit values are given in the following table.

    7.4  Labelling and Packaging

    The United Nations places  n-hexane in Hazard Class 3.1, flammable
    liquid. For packaging, the United Nations places  n-hexane in Group
    II, substance presenting medium danger.

    In the EEC,  n-hexane is classified as a harmful substance (Class II/A)
    and  n-hexane and mixtures (if  n-hexane is more than 5% of a
    mixture) should be labelled as follows:

     Highly flammable. Hazard by inhalation and in contact with skin.
     Possible risks of irreversible effects. Keep container in a
     well-ventilated place. Keep away from sources of ignition -
     no smoking. Do not breathe gas/fumes/vapour/spray.

    In the United Kingdom, road tankers transporting  n-hexane must be
    labelled "Flammable liquid".


        OCCUPATIONAL AIR EXPOSURE LIMIT VALUES
                                                                                                                       

    Country                Exposure limit descriptiona                     Value             Effectiveb date
                                                                                                                       

    Australia              Threshold limit value (TLV)
                           - Time-weighted average (TWA)                   360 mg/m3         1985(r)

    Belgium                Threshold limit value (TLV)
                           - Time-weighted average (TWA)                   180 mg/m3         1989(r)

    Canada                 Threshold limit value (TLV)
                           - Time-weighted average (TWA)                   180 mg/m3         1989

    Finland                Maximum permissible concentration (MPC)
                           - Time-weighted average (TWA)                   180 mg/m3         1989(r)
                           - Short-term exposure limit (STEL)              530 mg/m3

    Germany, Federal       Maximum acceptable concentration (MAK)
    Republic of            - Time-weighted average (TWA)                   180 mg/m3
                           - Short-term exposure limit (STEL)              360 mg/m3         1989(r)
                           - Biological tolerance value (BAT)
                           urine: hexane-2,5-dione plus                    9 mg/litre
                           4,5-dihydroxy-2-hexanone, at end
                           of exposure or end of shift

    Germany, Democratic    Maximum acceptable concentration (MAC)
    Republic of            - Time-weighted average (TWA)                   100 mg/m3
                           - Short-term exposure limit (STEL)              400 mg/m3         1988(r)

    Italy                  Threshold limit value (TLV)
                           - Time-weighted average (TWA)                   360 mg/m3         1985(r)
                                                                                                                       

    OCCUPATIONAL AIR EXPOSURE LIMIT VALUES (cont'd).
                                                                                                                       

    Country                Exposure limit descriptiona                     Value             Effectiveb date
                                                                                                                       

    Japan                  Maximum acceptable concentration (MAC)
                           - Time-weighted average (TWA)                   141 mg/m3         1985
                           (skin absorption must also be considered)

    Poland                 Maximum permissible concentration (MPC)
                           - Ceiling value (CLV)                           400 mg/m3         1986(r)

    Romania                Maximum permissible concentration (MPC)
                           - Time-weighted average (TWA)                   1200 mg/m3
                           - Ceiling value (CLV)                           1500 mg/m3        1975(r)

    Switzerland            Maximum acceptable concentration (MAK)
                           - Time-weighted average (TWA)                   180 mg/m3         1987

    Sweden                 Hygienic limit value (HLV)
                           - Time-weighted average (TWA)                   90 mg/m3
                           - Short-term exposure limit (STEL)              180 mg/m3         1990(n)

    United Kingdom         Guidance Limit (to be reviewed)
                           - Time-weighted average TWA)                    360 mg/m3
                           - Short-term exposure limit (STEL)              450 mg/m3         1990(n)
                                                                           (10-min)
                                                                                                                       

    OCCUPATIONAL AIR EXPOSURE LIMIT VALUES (cont'd).
                                                                                                                       

    Country                Exposure limit descriptiona                     Value             Effectiveb date
                                                                                                                       

    USA (ACGIH)            Threshold limit value (TLV)
                           - Time-weighted average (TWA)                   176 mg/m3         1989(r)
                           - Biological exposure index (BEI)               5 mg/litre
                           2,5-hexanedione in urine
                           (end of shift)
                           n-hexane in end-exhaled air                     144 mg/m3
                           (during shift)

    USA (OSHA)             Permissible exposure limit (PEL)                1800 mg/m3        1987(r)

    Yugoslavia             Maximum permissible concentration (MAC)
                           - Time-weighted average (TWA)                   1800 mg/m3        1971(r)
                                                                                                                       

    a  TWA  = a maximum mean exposure limit based on the period of a working day (generally 8 or 12 h).
       STEL = a maximum concentration of exposure for a specified time duration (generally 15 or 30 min).
    b  n = Notified direct by country.
        BIBLIOGRAPHY

    ACGIH (1986)  Documentation of the threshold limit values and
     biological exposure indices. Cincinnati, American Conference of
    Governmental Industrial Hygienists.

    ACGIH (1989)  Threshold limit values and biological exposure indices
     for 1989-1990. Cincinnati, American Conference of Governmental
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    CLAYTON, G.D. & CLAYTON, F.E. (1981)  Patty's industrial hygiene and
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    DUTCH CHEMICAL INDUSTRY ASSOCIATION (1989)  Handling chemicals safely.
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    GOSSELIN, R.E., HODGE, H.C., SMITH R.P., & GLEASON, M.N. (1976)
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    IRPTC (1988)  Data profile (legal file). Geneva, International
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    SAX, N.I. (1984)  Dangerous properties of industrial materials. New
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    US NIOSH (1976)  A guide to industrial respiratory protection.
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    US NIOSH/OSHA (1981)  Occupational health guidelines for chemical
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    US NIOSH/OSHA (1985)  Pocket guide to chemical hazards. Washington
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    See Also:
       Toxicological Abbreviations