Health and Safety Guide No. 91






    This is a companion volume to Environmental Health Criteria
    174: Isophorone

    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

    Isophorone: health and safety guide.

    (Health and safety guide ; no. 91)

    1.Solvents - standards 2.Solvents - toxicity
    3.Hazardous substances - standards 4.Environmental exposure

    ISBN 92 4 151091 9          (NLM Classification: WA 240)
    ISSN 0259-7268

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         1.1. Identity
         1.2. Physical and chemical properties
         1.3. Conversion factors
         1.4. Analytical methods
         1.5. Production and use

         2.1. Environmental transport, distribution, and transformation
         2.2. Environmental levels and human exposure
         2.3. Kinetics and metabolism in laboratory animals
              and humans
         2.4. Effects on laboratory mammals and  in vitro
              test systems
         2.5. Effects on humans
         2.6. Effects on other organisms in the laboratory and field

         3.1. Conclusions
              3.1.1. General population exposure
              3.1.2. Occupational exposure
              3.1.3. The environment
         3.2. Recommendations
              3.2.1. General population and occupational exposure
              3.2.2. Further studies

         4.1. Main human health hazards, prevention and protection,
              first aid
              4.1.1. First aid and medical treatment
                Eye contact
                Skin contact
              4.1.2. Safe handling
                Personal protection
         4.2. Fire and explosion hazards
         4.3. Storage
         4.4. Transport
         4.5. Spillage and disposal
              4.5.1. Spillage
              4.5.2. Disposal


         6.1. Previous evaluations by international bodies
         6.2. Exposure limit values
         6.3. Specific restrictions
         6.4. Labelling, packaging, and transport
         6.5. Waste disposal



    The Environmental Health Criteria (EHC) monographs 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 Director
    International Programme on Chemical Safety
    World Health Organization
    1211 Geneva 27


    1.1  Identity

    Common name:                 Isophorone

    Synonyms:                    2-cyclohexen-1-one, 3,5,5,-trimethyl;
                                 alpha-isophorone; isoacetophorone;
                                 isoforone; izoforon;

    Empirical formula:           C9H14O

    Chemical structure:


    Relative molecular mass:     138.2

    CAS registry number:         78-59-1

    RTECs registry number:       GW7700000

    EEC number:                  606-012-00-8

    EINECS number:               1011260

    1.2  Physical and Chemical Properties

    Isophorone is a colourless liquid. Its odour has been described as
    similar to those of peppermint and camphor. It is soluble in water
    and is miscible in all proportions with aliphatic and aromatic
    hydrocarbons, alcohols, ethers, esters, ketones, and chlorinated
    hydrocarbons. Physical and chemical data are summarized in Table 1.

    Table 1. Physical and chemical data of isophorone


    Specific gravity (20 C/4 C)               0.922
    Boiling point at 1013 hPa                   215 C
    Freezing point                              -8.1 C
    Refractive index                            1.4775 n20D
    Viscosity at 20 C                          2.6m Pas
    Coefficient of cubic expansion              0.00085 C-1
    at 20 C                                    0.00078 C-1
    Surface tension at 20 C                    30 mN/m
    Vapour pressure                             0.4 mbar (20 C)
                                                0.26 mmHg (25 C)
    Vapour density (air=1)                      4.7
    Concentration in saturated air              approx. 1941 mg/m3 
      at 20 C and 1013 hPa                     (340 ppm)
    Solubility at 20 C
      Isophorone in water                       12.0-17.5 g/litre
      Water in isophorone                       53 g/litre
    Log Kow (20 C)                             1.67 (measured)
                                                1.7 (estimated)
    Solubility parameters (Hansen)
      delta                                     19.2 (J/cm3)1/2
      deltaD                                    16.6 (J/cm3)1/2
      deltaP                                    8.2 (J/cm3)1/2
      deltaH                                    7.4 (J/cm3)1/2
    Hydrogen bonding parameter, gamma           14.9
    Flashpoint, closed cup                      85 C
    Explosion limits in air                     0.8-3.8 vol-%
    Ignition temperature                        455-470 C
    Heat of evaporation at 215 C               349.2 kJ/kg
    Heat of combustion (p=const. at 20 C)      38 100 kJ/kg
    Relative permittivity at 20 C              19.9
    Specific resistivity                        1  107 ohm  cm

    A typical, commercial sample of isophorone may contain 1-3% of the
    isomer beta-isophorone (3,5,5-trimethyl-3-cyclohexene-1-one) with
    the sum of alpha- and beta-isomers exceeding 99%.

    Isophorone is stable and may be stored in steel or aluminium
    containers. Prolonged periods of storage may lead to slight

    1.3  Conversion Factors

    The following conversion factors have been calculated for 22 C and
    1013 hPa:

         1 ppm = 5.71 mg/m3

         1 mg/m3 = 0.175 ppm.

    1.4  Analytical Methods

    The purity of technical isophorone may be determined by capillary
    gas chromatography (GC) with a flame ionization detector (FID).
    Recommended conditions are shown in Table 2.

    Earlier methods for the determination of isophorone in air were
    based on adsorption on charcoal; however, it has been found that
    isophorone adsorbed on charcoal decomposes during storage. More
    recent methods involve adsorption on polymers, such as XAD resins or
    Tenax-GC, followed by desorption and analysis by capillary GC with

    The determination of isophorone in wastewater samples and fish
    tissues may be achieved using solvent extraction, clean-up with gel
    permeation chromatography, and analysis by GC/MS, in both the
    electron impact and chemical ionization modes.

    Table 2.  Gas chromatographic conditions for the analysis of
    technical isophorone


    Column                  Fused silica capillary   Macrobore
    Coating                 OV - 1701                CP Wax 52CB
    Dimensions              60 m/0.25 mm             25 m/0.53 mm
    Injector temperature    240 C                   250 C
    Temperature-Programme   6 min 70-220           10 min 105-120 
                              @ 4/min                 @ 6/min
                                                     2 min 120-150 
                                                       @ 10/min

    1.5  Production and Use

    Isophorone is produced commercially by the catalytic condensation of
    acetone at elevated temperature and pressure and is purified by
    distillation. Worldwide annual production capacity was estimated to
    be 92 000 tonnes in 1988.

    Isophorone is used as a chemical intermediate for the synthesis of a
    variety of organic chemicals.

    Isophorone is a solvent for a number of natural and synthetic resins
    and polymers, such as polyvinyl chlorides and acetates, cellulose
    derivatives, epoxy and alkyd resins, and polyacrylates. It is
    therefore used as a high boiling solvent in industrial air drying
    and stoving paints, nitro emulsion leather finishes, and the
    manufacture of vinyl resin-based printing inks for plastic surfaces.
    Isophorone is also used as a solvent for some pesticide
    formulations, especially for emulsifiable concentrates of anilides
    and carbamates.


    2.1  Environmental Transport, Distribution, and Transformation

    Isophorone may enter the environment from numerous industries, waste
    and waste-water disposal, and its use as a solvent and a pesticide
    carrier. Following release into water or soil, environmental
    concentrations decrease as a result of volatilization and
    biodegradation. Isophorone in the atmosphere is removed by
    photochemical processes with an estimated half-life of about 30 min
    (based on a mathematical model). In a Die-away test, isophorone was
    biodegraded by approximately 70% in 14 days and 95% after 28 days.
    The results of biodegradation studies are variable and limited.
    Water solubility, soil adsorption coefficients, and polarity
    indicate that significant adsorption by suspended solids and
    sediments is unlikely to occur.

    Although isophorone has been found in fish tissues, the data and the
    physical and chemical properties suggest that significant
    bioconcentration is unlikely. A half-life of one day has been
    measured in a single fish species.

    2.2  Environmental Levels and Human Exposure

    Isophorone has not been measured in ambient air. An isophorone
    concentration in coal fly ash of 490 g/kg (490 ppb) has been
    reported. Isophorone has been identified in surface waters
    (0.6-3 g/litre), groundwater (10 g/litre), urban run-off
    (10 g/litre), and landfill leachate (29 g/litre).

    Isophorone has been identified in industrial wastewater at
    100 g/litre. After classical secondary treatment, the concentration
    of isophorone in the effluent was 10 g/litre.

    Isophorone has been identified in lake sediments (0.6-12 g/kg dry

    It has also been identified in tissues from several species of fish
    at concentrations of up to 3.61 mg/kg wet weight.

    Isophorone was not detected in the edible parts of bean plants,
    rice, or sugar beet, following application as a pesticide carrier.

    2.3  Kinetics and Metabolism in Laboratory Animals and Humans

    Distribution studies on rats using 14C-isophorone showed that 93%
    of orally administered radioactivity appeared mainly in the urine
    and expired air within 24 h. The tissues retaining the highest
    concentration after this period were the liver, kidney, and
    preputial glands.

    The metabolites identified in the urine of rabbits after oral
    administration of isophorone resulted from the oxidation of the
    3-methyl group, reduction of the keto group, and hydrogenation of
    the double link of the cyclohexene ring, and were eliminated as
    such, or, in the case of the alcohols, as the glucuronide

    Percutaneous LD50 values indicate that isophorone is rapidly
    absorbed through the skin.

    2.4  Effects on laboratory mammals and  in vitro test systems

    The acute toxicity of isophorone is low, oral LD50 values being
    >1500 mg/kg in the rat, >2200 mg/kg in the mouse, and >2000 mg/kg
    in the rabbit. Dermal LD50 values were 1700 mg/kg in the rat and
    >1200 mg/kg in the rabbit. Acute effects from dermal exposure in
    rats and rabbits ranged from mild erythema to scabs. Conjunctivitis
    and corneal damage have been reported on direct application to the
    eye or exposure to high concentrations of isophorone. No skin
    sensitization was reported in guinea-pigs using the
    Magnusson-Kligman test.

    In acute and short-term oral studies on rodents given high doses
    (>1000 mg/kg), degenerative effects in the liver as well as CNS
    depression were seen and there were some deaths. In 90-day studies,
    the no-observed-effect levels (NOELs) in rats and mice were
    evaluated to be 500 mg/kg body weight per day. In a 90-day oral
    study on Beagle dogs (with limited numbers), no effects were seen at
    doses of up to 150 mg/kg body weight per day.

    In acute and short-term inhalation studies reviewed, irritation,
    haematological effects, and decreased body weights were noted. Since
    the study designs were inadequate, no NOEL could be determined and
    no inference for human health could be made.

    Isophorone does not induce gene mutations in bacteria, chromosomal
    aberrations  in vitro, DNA repair in primary rat hepatocytes, or
    bone-marrow micronuclei in mice. Positive effects were observed only
    in the absence of an exogenous metabolic system in L5178Y TK +/-
    mouse lymphoma mutagenesis assays as well as in a sister chromatid
    exchange assay. Isophorone induced morphological transformation  in
     vitro in the absence of an exogenous metabolism system. Isophorone
    did not induce sex-linked recessive lethal mutations in  Drosophila.
    The weight of the evidence of all mutagenicity data supports the
    contention that isophorone is not a potent DNA reactive compound. In
    an  in vivo assay, no DNA binding was observed in the liver and
    kidneys (organs affected in the carcinogenicity bioassays).

    In long-term oral toxicity studies on mice and rats, male rats
    showed several proliferative lesions of the kidney. The role of
    alpha2u-globulin accumulation in the etiology of these lesions has
    been recognized. Since significant amounts of alpha2u-globulin have
    not been detected in humans, this mechanism of carcinogenesis
    appears not to be relevant in humans. Preputial gland carcinomas
    were observed in five high-dose male rats and two clitoral gland
    adenomas were seen in low-dose female rats with exposure to
    isophorone. These may also be related to alpha2u-globulin
    accumulation. Isophorone exposure was associated with some
    neoplastic lesions of the liver, and the integumentary and the
    lymphoreticular systems of male mice, as well as nonneoplastic liver
    and adrenal cortex lesions, but this was not observed in treated
    female mice.

    In the only available long-term inhalation study on rats and
    rabbits, irritation of the eye and nasal mucosa as well as lung and
    liver changes were observed at approx. 1347 mg/m3 (250 ppm).
    However, this may have been because of limitations in the study.

    Very limited studies on rats and mice indicate that isophorone does
    not affect the fertility or cause developmental toxicity in
    experimental animals.

    The fact that central nervous system depression occurs in
    experimental animals could indicate a possible neurotoxic effect.
    Isophorone also elicited a positive effect in the behavioural
    despair swimming test.

    2.5  Effects on Humans

    The odour of isophorone can be detected at a concentration as low as
    1.14 mg/m3 (0.2 ppm). Eye, nose, and throat irritation have been
    reported at concentrations below 28.5 mg/m3 (5 ppm); above 1142
    mg/m3 (200 ppm) nausea, headache, dizziness, faintness, and
    inebriation have been reported.

    2.6 Effects on Other Organisms in the Laboratory and Field

    No data on terrestrial animals were available.

    Acute LC50 values are available for several freshwater and marine
    species. EC50s (96-h) (based on cell count and chlorophyll) ranged
    from 105 to 126 mg/litre; 48-h LC50s for  Daphnia magna ranged
    from 117 to 120 mg/litre, and 96-h LC50s for freshwater fish
    ranged from 145 to 255 mg/litre.

    LC50s (96-h) for marine invertebrates ranged from 12.9 to 430
    mg/litre. The 96-h LC50 for a single marine fish species was
    between 170 and 300 mg/litre. Data from studies with measured
    exposure concentrations did not differ from those of studies with
    nominal concentrations. NOELs for  Pimephales promelas, tested in
    different laboratories, ranged from 14 to 45.4 mg/litre.

    The available data suggest that the toxicity of isophorone for
    aquatic organisms is low.


    3.1  Conclusions

    3.1.1  General population exposure

    Isophorone is used as a solvent for resins, polymers, and pesticide
    formulations. Dermal and inhalation exposure may occur, but will
    most likely be minimal. Data are available that show that isophorone
    can occur in g/litre concentrations in drinking-water and fish. In
    view of the low toxicity of isophorone in experimental studies and
    the low levels of exposure from environmental sources, the risks for
    the general population appear to be minimal.

    3.1.2  Occupational exposure

    In the absence of adequate engineering controls and industrial
    hygiene measures, occupational exposure to isophorone may exceed
    acceptable levels and cause eye, skin, and respiratory irritation;
    other health effects may occur at higher concentrations. No studies
    on long-term health effects in workers were available for review by
    the Task Group.

    3.1.3  The environment

    Isophorone may be released into the environment following its use as
    a pesticide carrier and its ubiquitous use as a solvent. Low
    concentrations have been identified in several environmental
    compartments, though it has a low environmental persistence due to
    biodegradation, volatilization, and photochemical oxidation
    processes. The available data suggest that the toxicity of
    isophorone for aquatic organisms is low.

    3.2  Recommendations

    3.2.1  General population and occupational exposure

    Care should be taken to prevent contamination of groundwater and

    Workers involved in the manufacture or use of isophorone should be
    protected from exposure by means of adequate engineering controls
    and appropriate industrial hygiene measures. Levels of occupational
    exposure should be kept within acceptable limits and should be
    monitored regularly.

    3.2.2  Further studies

    Health surveillance of exposed workers should be conducted and
    reported on.

    Actual levels of isophorone in the waters surrounding industrial
    areas should be determined.

    Adequate short-term/long-term inhalation studies on experimental
    animals should be conducted, in order to determine safe levels of
    occupational exposure.

    Information is required on the anaerobic biodegradation of
    isophorone, especially as it has been identified in landfill


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

    Isophorone vapours are irritating to the eyes and the respiratory
    tract. Prolonged exposure may cause fatigue and malaise. Prolonged
    contact with liquid isophorone may irritate the skin.

    4.1.1  First aid and medical treatment  Eye contact

    Immediately flush eyes with plenty of water. Ensure adequate
    flushing of the eyes by separating the eyelids with fingers. Medical
    attention should be obtained.  Skin contact

    Contaminated clothing should be removed and the affected area of the
    skin thoroughly flushed with water. If skin irritation occurs,
    medical attention should be obtained.  Inhalation

    Provide fresh air. Monitor breathing, and give oxygen if breathing
    is difficult.  Ingestion

    Seek medical advice immediately. Wash out mouth with water. Emesis
    may be indicated soon after ingestion, unless the patient is
    unconscious. Let the victim ingest charcoal (30-100 g in adults) as
    a slurry, to limit absorption of isophorone from the intestine.

    4.1.2  Safe handling  Personal protection

    Atmospheric levels should be kept below the recommended occupational
    exposure limits by local exhaust ventilation. Respirators should be
    worn in areas where these limits are likely to be exceeded. Skin and
    eye protection should be worn where exposure is likely to occur.
    Nitrile rubber gloves are recommended.

    4.2  Fire and Explosion Hazards

    Isophorone is flammable. Suitable extinguishing media are water
    spray, carbon dioxide, foam, or dry powder.

    The explosion limits in air are 0.8-3.8 vol.%.

    4.3  Storage

    Containers should be kept tightly closed and stored in a
    well-ventilated area.

    4.4  Transport

    Local requirements regarding the movement of hazardous goods or
    wastes must be complied with. Containers should be checked to ensure
    that they are sound and labels undamaged before despatch. For
    regulations see section 6.4.

    4.5  Spillage and Disposal

    4.5.1  Spillage

    The area should be evacuated and sources of ignition removed.
    Self-contained breathing apparatus, gloves, goggles, face shield,
    and boots should be worn. Liquid should be prevented from entering
    sewers, basements, and workpits.

    Small-scale spillages should be absorbed on paper towels and the
    paper burnt, away from other combustible material.

    For medium-scale spillages, the liquid should be absorbed with sand
    or earth and all material should be removed to a safe place for
    subsequent incineration. The contaminated area should be washed out
    with plenty of water.

    For large-scale spillages, the spilt liquid should be prevented from
    spreading by the use of sand or earth. The liquid should be
    transferred to a salvage tank if possible; otherwise it should be
    treated as for medium-scale spillages. The local authorities should
    be informed at once, if the spilt liquid enters the surface-water

    4.5.2  Disposal

    This combustible material may be burned in a chemical incinerator.
    The product should not be buried or dumped in a landfill.


    The toxicity of isophorone for aquatic and terrestrial species is

    Industrial discharges and any spillage or unused product should be
    prevented from polluting the environment and spreading to vegetation
    or waterways and should be treated and disposed of properly (section


    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file and other United Nations sources. The intention is to give the
    reader a representative but non-exhaustive overview of current
    regulations, guidelines, and standards.

    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. Furthermore,
    the regulations and guidelines of all countries are subject to
    change and should always be verified with the appropriate regulatory
    authorities before application.

    6.1  Previous Evaluations by International Bodies

    None available.

    6.2  Exposure Limit Values

    Some exposure limit values are given in the table on the next page.

    6.3  Specific Restrictions

    In Germany, isophorone may not be handled by adolescents or
    pregnant, or nursing, women.

    6.4  Labelling, Packaging, and Transport

    The European Community legislation requires labelling as an irritant
    substance using the symbol:

    The label must read:

          Irritating to eyes, respiratory system and skin; in case of
          contact with eyes, rinse immediately with plenty of water and
          seek medical advice.

    Regulations on the Transport of Dangerous Goods:

         RID/ADR:                 Class 3, No. 32C
         ADNR:                    Class 3, No. 4, category K3
         GGVSee/IMDG-Code:        Not classified
         IATA-RAR:                Article No. 1939

    6.5  Waste Disposal

    In the USA, isophorone is rated as a persistent compound, and any
    non-domestic waste must be treated as a toxic pollutant. Specific
    instructions are given for notification and incineration. Permits
    are required for its discharge and discharge limits have been set.

        Exposure limit values in some countries

    Medium    Specification    Country/              Exposure Limit Description                Value                Effective
                               organization                                                                         date

    AIR                        Finland               Threshold limit value (TLV)               28 mg/m3 (5 ppm)     1987

                               Germany               Maximum worksite concentration (MAK)
                                                     - time-weighted average (TWA)             28.0 mg/m3           1980

                               Russian Federation    Ceiling value                             1.0 mg/m3            1978

                               Sweden                Hygienic limit value                      30.0 mg/m3           1985

                               United Kingdom        Recommended limit (RECL)
                                                     - time-weighted average (TWA)             25 mg/m3             1985
                                                     - short-term exposure level (STEL)        25 mg/m3

                               USA                   Permissible Exposure Limit (OSHA)
                               - DOL/OSHA            8-h time-weighted average (TWA)           23.0 mg/m3 (4 ppm)   1989
                               - NIOSH               Recommended Exposure Limit (REL)
                                                     up to a 10-h TWA                          23 mg/m3 (4 ppm)     1988
                               - ACGIH               Threshold limit value (TLV)
                                                     Ceiling value (15-min)                    28 mg/m3 (5 ppm)     1992



    CEC (1987)  Legislation in dangerous substances - Classification and
     labelling in the European Communities - Vol. 1 & 2, Commission of
    the European Communities, London, Graham & Trotman, Ltd.

    CEC/IPCS (1991)  International chemical safety card (ICSC) No. 0169
     on isophorone, Luxembourg, Grand Duchy of Luxembourg, Commission
    of the European Communities (CEC); Geneva, Switzerland,
    International Programme on Chemical Safety (IPCS), World Health
    Organization, 2 pp.

    IARC (1972-present)  IARC monographs on the evaluation of
     carcinogenic risk of chemicals to man, Lyon, International Agency
    for Research on Cancer.

    IPCS (in preparation)  Environmental Health Criteria 174:
     Isophorone, Geneva, World Health Organization.

    IRPTC (1985)  IRPTC file on treatment and disposal methods for waste
     chemicals, Geneva, International Register of Potentially Toxic
    Chemicals, United Nations Environment Programme.

    IRPTC (1986)  IRPTC legal file 1986, Geneva, International Register
    of Potentially Toxic Chemicals, United Nations Environment

    SAX, N.I. (1984)  Dangerous properties of industrial materials, New
    York, Van Nostrand Reinhold Company, Inc.

    UNEP/IEO (1990)  Storage of hazardous materials: a technical guide
     for safe warehousing of hazardous materials, Paris, United Nations
    Environment Programme - Industry and Environment Office, 80 pp.

    UNITED NATIONS (1986)  Recommendations on the transport of dangerous
     goods, 4th ed., New York, United Nations.

    US NIOSH/OSHA (1981)  Occupational health guidelines for chemical
     hazards, 3 Vol., Washington DC, US Department of Health and Human
    Services, US Department of Labor (Publication No. DHHS (NIOSH)

    See Also:
       Toxicological Abbreviations
       Isophorone (EHC 174, 1995)
       Isophorone (ICSC)
       ISOPHORONE (JECFA Evaluation)