EPA 749-F-94-011a

                    CHEMICAL SUMMARY FOR CYCLOHEXANE
                                 prepared by
                  OFFICE OF POLLUTION PREVENTION AND TOXICS
                     U.S. ENVIRONMENTAL PROTECTION AGENCY
                              September 1994

     This summary is based on information retrieved from a systematic
search limited to secondary sources (see Appendix A).  These sources
include online databases, unpublished EPA information, government
publications, review documents, and standard reference materials.  No
attempt has been made to verify information in these databases and
secondary sources.

I.   CHEMICAL IDENTITY AND PHYSICAL/CHEMICAL PROPERTIES

     The chemical identity and physical/chemical properties of
cyclohexane are summarized in Table 1.

        TABLE 1.  CHEMICAL IDENTITY AND CHEMICAL/PHYSICAL PROPERTIES 
                             OF CYCLOHEXANE
_______________________________________________________________________
Characteristic/Property   Data                        Reference
_______________________________________________________________________
CAS No.                   110-82-7          
Common Synonyms           hexahydrobenzene, 
                             hexamethylene, 
                             hexanaphthene            Budavari et al. 1989
Molecular Formula         C6H12             
Chemical Structure    
                      
Physical State            liquid                      Budavari et al. 1989
Molecular Weight          84.16                       Budavari et al. 1989
Melting Point             6.47C                      Budavari et al. 1989
Boiling Point             80.7C @760 mm Hg           Budavari et al. 1989
Water Solubility          55 mg/L @ 25C              CHEMFATE 1994
Density                   d20/4 C, 0.7781            Budavari et al. 1989
Vapor Density (air = 1)   2.90                        Verschueren 1983
KOC                       482 (calculated)            CHEMFATE 1994
Log KOW                   3.44                        CHEMFATE 1994
Vapor Pressure            77 mm Hg @ 20C             Verschueren 1983
Reactivity                flammable; reacts with
                          oxidizing materials         HSDB 1994
Flash Point               1F ( 18C) (closed cup)    Budavari et al. 1989
Henry's Law Constant      0.195 atm.m3/mol 
                             @ 25C (calculated)      CHEMFATE 1994
Fish Bioconcentration 
   Factor                 240 (calculated)            CHEMFATE 1994
Odor Threshold            300 ppm (in air); mild,
                          sweet odor (chloro-
                            form-like)                HSDB 1994
Conversion Factors        1 ppm = 3.49 mg/m3
                          1 mg/m3 = 0.29 ppm          Verschueren 1983
_______________________________________________________________________

II. PRODUCTION, USE, AND TRENDS

   A. Production

      There are four cyclohexane producers in the United States. 
      Table 2 lists producers, plant locations, and plant capacities.  
      Annual US capacity is approximately 378 million  gallons.  In 1992, 
      an estimated 338 million gallons of cyclohexane were produced in the 
      US.  During that same year, 5 million gallons were imported into the 
      US and 38 million gallons were exported (Mannsville 1993).

  B. Use

     Cyclohexane is used in a number of industrial applications.  The 
     primary use of cyclohexane, accounting for approximately 58 percent 
     of all use, is in the production of adipic acid, a nylon intermediate. 

     Cyclohexane is also used in the production of caprolactam, another 
     nylon intermediate.  Small amounts are used as a solvent for lacquers 
     and resins; as a paint and varnish remover; as an intermediate in the
     manufacture of benzene, cyclohexanone, and nitrocyclohexane; as fuel 
     for camp stoves; as an ingredient in fungicidal formulations; and in 
     the industrial recrystallization of steroids (Mannsville 1993).  
     Table 3 shows the estimated 1992 US end-use pattern for cyclohexane.

 C. Trends

    Demand for cyclohexane is expected to increase at a rate of 2 to 2.5 
    percent per year (Mannsville 1993).

             TABLE 2.  United States Producers of Cyclohexane
_______________________________________________________________________
Company             Plant Location              Plant Capacity
                                           (in millions of gallons)
_______________________________________________________________________

Champlin            Corpus Christi, TX               30
Chevron             Port Arthur, TX                  38
Phillips            Borger, TX                       45
                    Sweeny, TX                      110
                    Guayama, PR                      90
Texaco              Port Arthur, TX                  65
_______________________________________________________________________
Source:  Mannsville 1993.

TABLE 3.  Estimated 1992 United States End-Use Pattern of Cyclohexane
_______________________________________________________________________
Use of Cyclohexane                             Percentage of US
(typical Standard Industrial                    Cyclohexane Use
Classification (SIC) Code)    
(see end note 1)
_______________________________________________________________________

Adipic acid (production, SIC 2869)                   58%
Caprolactam (production, SIC 2865)                   35%
Miscellaneous (including solvent)
   (no applicable SIC Code(s))                        7%
_______________________________________________________________________
Source:  Mannsville 1993.

III. ENVIRONMENTAL FATE

     A. Environmental Release

        Cyclohexane occurs naturally in crude oil and may be released 
        to the environment from sites where petroleum products are refined, 
        stored, and used (HSDB 1994).  It is also released into the 
        atmosphere from volcanos and tobacco smoke.  The chemical is
present 
        in exhaust gases from motor vehicles and in fugitive emissions and 
        in wastewater from industrial facilities involved in its 
        production and use (HSDB 1994).  

        In 1992, environmental releases of the chemical, as reported to the 
        Toxic Chemical Release Inventory by certain types of U.S. 
        industries, totaled about 14 million pounds, including 13.6 million 
        pounds to the atmosphere; 21,039 pounds to surface water; 230,985 
        pounds by underground injection; and 107,748 pounds to land 
        (TRI92 1994).

        Air monitoring has detected the chemical in the air at various 
        US locations, including Los Angeles, CA; Houston, TX; Tulsa, 
        OK; and Jones State Forest, TX.  When reported, concentrations 
        were less than 25 ppb (CHEMFATE 1994).  Water samples collected 
        from the Hudson River Basin (28 sites), the Mississippi River 
        Basin (Alabama and Texas, 45 sites), and the Gulf of Mexico 
        contained less than 20 ppb of cyclohexane (CHEMFATE 1994).  
        The chemical has also been detected in samples of mother's milk in 
        Baton Rouge, LA; Bridgeville, PA; and Bayonne and Jersey City, NJ 
        (CHEMFATE 1994).

   B. Transport

      Cyclohexane is volatile (vapor pressure, 77 mm Hg @ 20C; Henry's 
      Law constant, 0.195 atm.m3/mol @ 25C) and is expected to partition 
      into the atmosphere from both water and soil (HSDB 1994).  The 
      estimated KOC for cyclohexane, 482 (CHEMFATE 1994), indicates a 
      moderate potential for soil adsorption.  Cyclohexane is slightly 
      soluble in water (55 ppm) and has the potential to leach through 
      soil into groundwater (HSDB 1994).

  C. Transformation/Persistence

     1. Air - In the atmosphere, cyclohexane degrades by reaction with 
        photochemically produced hydroxyl radicals.  One estimate of the 
        rate constant for the reaction between photochemically-produced 
        hydroxyl radicals and cyclohexane is 0.795 x 10-11 cm3/molecule- 
        sec (CHEMFATE 1994); an estimated half-life for this type of 
        reaction is 52 hours (HSDB 1994).  The half-life is shorter in the 
        presence of photochemical smog; in Los Angeles in sunlight, for 
        example, 39% of the chemical was degraded in 6 hours (HSDB 1994).  
        The products of the reaction are cyclohexyl nitrate, and 
        unidentified carbonyl compounds (HSDB 1994).

     2. Soil - Volatilization and leaching are the primary removal 
        mechanisms for cyclohexane in soil.  The chemical is resistant to 
        biodegradation under most conditions, unless other degradable 
        hydrocarbons, such as oil and gasoline, are present (CHEMFATE 1994; 
        HSDB 1994).

     3. Water - The primary route for the removal of cyclohexane from the 
        aquatic environment is volatilization (half-life in a model river, 
        2 hours) (HSDB 1994).

     4. Biota - The estimated fish bioconcentration factor for cyclohexane 
        of 240 (CHEMFATE 1994) indicates a potential for its limited 
        bioaccumulation in the aquatic food chain.

IV. HEALTH EFFECTS

    A. Pharmacokinetics

       1. Absorption - Cyclohexane is absorbed following inhalation (HSDB 
          1994) and nominally by the skin.  Massive applications of the 
          chemical to the skin of rabbits have produced microscopic changes 
          in the liver and kidneys (effective doses not given) (Sandmeyer
          1981).  Systemic toxicity observed in animals exposed orally 
          to cyclohexane (see section IV. B) indicates that gastro-
          intestinal absorption of the chemical also occurs .

          In workers exposed to atmospheric cyclohexane, 22.8% of the 
          total respiratory intake was absorbed, and a "significant amount" 
          of the absorbed cyclohexane was either retained or metabolized 
          (Longacre 1987).

       2. Distribution - Following inhalation exposure of Wistar rats to 
          concentrations of cyclohexane ranging from 300-2000 ppm, 
          perirenal fat concentrations of the chemical were 23- to 38-fold 
          greater than brain concentrations after one week of exposure and 
          50- to 80-fold greater than brain concentrations, after two
          weeks.  No information was found regarding distribution to other 
          organs.

       3. Metabolism - Cyclohexane is metabolized via the hepatic, 
          vascular, and renal systems (Sandmeyer 1981).  Microsomal 
          hydroxylases oxidize cyclohexane to cyclohexanol in the presence 
          of NADPH and oxygen (Longacre 1987).  Other metabolites
identified 
          in mammalian systems include trans-cyclohexane-1,2,-diol, cyclo-
          hexanone, and adipic acid (HSDB 1994).
                
      4. Excretion - Shoe factory workers exposed to atmospheric concentra-
         tions of cyclohexane ranging from 17 to 2484 mg/m3 excreted 
         cyclohexanol in the urine at concentrations of 0.27 to 7.18 
         micrograms/mL and at the rate of 0.05 to 3.23 micrograms/min.  
         The excretion rates of cyclohexanol correlated well with cyclo-
         hexane concentrations in the blood and in alveolar air (Longacre 
         1987).  In a study of alveolar excretion, workers were exposed to 
         cyclohexane for 4 hours and excretion was measured during a 6-hour 
         post-exposure period.  The post-exposure decline occurred in two
         phases: in the first, the half-life was 11.2 minutes, whereas in 
         the second, about one hour later, the half-life was 115.3 minutes. 

         The alveolar excretion of cyclohexane was approximately 9.1 mg for 
         an average alveolar ventilation of 5 L/minute.  Only 0.5 to 1.0%
         of the dose was excreted in the urine as cyclohexanol and 
         cyclohexanone (Longacre 1987).

         Portions of inhaled cyclohexane are excreted unchanged in the 
         urine and in exhaled air; the remainder is metabolized to 
         cyclohexanol and excreted in the urine, mainly as the sulfate or 
         glucuronide conjugate (HSDB 1994; Sandmeyer 1981).  Adult 
         chinchilla-doe rabbits given a single oral dose of 300-400 mg/kg 
         14C-cyclohexane excreted 35-45% of the dose in expired air 
         (10% as CO2 and 25-35% as unchanged cyclohexane), and eliminated 
         33-56% of the dose in the urine (Longacre 1987).  Animals given a 
         lower dose (0.3 mg/kg) of the radiolabeled cyclohexane excreted 
         no unchanged chemical in expired air, 5% as CO2, and 98% in the 
         urine.  The only urinary metabolites detected were the 
         glucuronides of cyclohexanol (30-40% and 60% of the high and 
         low dose, respectively) and transcyclohexane-1,2-diol (5-8% 
         and 17% of the high and low dose, respectively).  A total of 
         0.1-0.2% was excreted in the feces, and 2.4-2.6% of the dose 
         was recovered from the tissues.

    B. Acute Effects

       Cyclohexane has low acute toxicity, producing eye irritation in 
       humans and neurological symptoms (see section IV. G), other organ 
       effects, and death in animals at very high doses.

       1. Humans - According to one source, cyclohexane is detectable by 
          odor and is irritating to the eyes at 300 ppm; another source 
          suggested 25 ppm as the odor threshold (ACGIH 1991).  Undiluted 
          cyclohexane is also irritating to the skin (Longacre 1987).  No 
          other information was found in the secondary sources searched 
          for the acute toxicity of cyclohexane to humans.

      2. Animals - The oral LD50 for cyclohexane in rats ranges from 8.0 
         to 39 mL/kg (both greater than 5 g/kg), depending upon the age of 
         the animals (Sandmeyer 1981).  The oral LD50 for mice is 1.3 g/kg; 
         the minimum lethal oral dose in rabbits is 5.5-6.0 g/kg; and the 
         dermal LD50 in rabbits is >180 g/kg (Longacre 1987).  Within 1 to 
         1.5 hours, lethal doses to animals produced severe diarrhea, 
         vascular damage and collapse, hepatocellular degeneration and
toxic
         glomerulonephritis (Sandmeyer 1981).  Exposure of rabbits to 3330 
         ppm (duration not given) produced no effect; 18,500 ppm for 8
hours 
         was non-lethal; and 26,600 ppm for 1 hour was lethal (ACGIH 1991). 
         Application of 1.55 g/day of cyclohexane to the skin for 2 days 
         produced minimal irritation (Longacre 1987).

   C. Subchronic/Chronic Effects

      Cyclohexane administered subchronically is of low toxicity, producing 
      neurological effects (see section IV. G), ocular, gastrointestinal,
and 
      respiratory effects in animals at very high, lethal concentrations. 

      1. Humans - No information was found for the subchronic/chronic 
         toxicity of cyclohexane in humans in the secondary sources
searched.

      2. Animals - No effects were observed in rabbits exposed to 434 ppm 
         cyclohexane for fifty 6-hour periods or in rhesus monkeys exposed 
         to 1234 ppm under identical exposure conditions (Longacre 1987).  
         Concentrations of 7445 ppm, 6 to 8 hours/day for 2 to 26 weeks 
         were lethal to rabbits, producing neurological effects (see
         section IV. G) as well as closure of the eyes, conjunctival 
         infection, salivation, labored respiration, cyanosis and diarrhea 
         prior to death (Longacre 1987).  Rats exposed by inhalation to
1500
         or 2500 ppm cyclohexane for 9-10 hours/day, 5 days/week for 7, 14, 
         or 30 weeks exhibited no adverse effects (Longacre 1987).

     D. Carcinogenicity

        1. Humans - No information was found in the secondary sources 
           searched regarding the carcinogenicity of cyclohexane in humans.
           
        2. Animals - No information was found in the secondary sources 
           searched regarding the carcinogenicity of cyclohexane in
animals.

     E. Genotoxicity

        Cyclohexane was negative for viral enhanced cell transformation in 
        Syrian hamster embryo (SA7/SHE) cells and for histidine reverse
gene 
        mutation in Salmonella typhimurium (Ames assay) (GENETOX 1994).

     F. Developmental/Reproductive Toxicity

        1. Humans - No information was found in the secondary sources 
           searched regarding the developmental/reproductive toxicity of 
           cyclohexane in humans.

        2. Animals - No information was found in the secondary sources 
           searched regarding the developmental/reproductive toxicity of 
           cyclohexane in animals.

     G. Neurotoxicity

        The central nervous system is a major target organ for the toxicity 
        of cyclohexane.  High concentrations of the chemical produce
various 
        effects, ranging from trembling to death.

        1. Humans - At high concentrations, cyclohexane is a central
nervous 
           system depressant and may cause dizziness and unconsciousness 
           (Sandmeyer 1981).  No other information was found in the
secondary 
           sources searched regarding the neurotoxicity of cyclohexane in
           humans.
               
       2. Animals - Mice exposed to 50 mg/L (14,500 ppm) for 2 hours 
          exhibited minimal narcotic effects (Longacre 1987).  Exposure to 
          18,000 ppm produced trembling within 6 minutes, disturbed 
          equilibrium within 15 minutes, and complete recumbency within 
          30 minutes (Longacre 1987).  Following exposure of Wistar rats
          for 2 weeks to concentrations of cyclohexane ranging from
300-2000 
          ppm, cerebral levels of RNA, glutathione, glutathione peroxidase, 
          and azoreductase were evaluated.  The only effect noted was a 
          decrease in azoreductase activity (Longacre 1987).  The effect
          of cyclohexane on the vestibular function of rats was measured by 
          recording nystagmus induced by accelerated rotation.  Cyclohexane 
          caused an excitation of the vestibulo-oculomotor reflex
(threshold 
          blood level, 1.1 mmole/L) (HSDB 1994).  Concentrations of 7445
          ppm, 6 to 8 hours/day for 2 to 26 weeks were lethal to rabbits, 
          producing convulsions, tremors, narcosis, and paresis of the legs 
          (Longacre 1987).

V. ENVIRONMENTAL EFFECTS

   TLm values for fish range from 32 to 57.7 mg/L, indicating that the 
   chemical is moderately toxic to aquatic organisms in acute tests.  
   Cyclohexane is expected to be of low toxicity to terrestrial organisms 
   and has a smog-forming potential.
     
   A. Toxicity to Aquatic Organisms

      TLm values for fish (24-96 hr) are 43-32 mg/L (Pimephales promelas, 
      fathead minnow), 43-34 mg/L (Lepomis macrochirus, bluegill), 42.3 
      mg/L (Crassium auratus, goldfish), and 57.7 mg/L (Poecilia 
      reticulata, guppy) (Verschueren 1983).  Mussel larvae (Mytilus 
      edulis) exposed to 1 to 100 ppm (mg/L) cyclohexane exhibited a 10-20% 
      increase in growth rate (Verschueren 1983).  The threshold concentra-
      tion of cyclohexane in the cell multiplication inhibition assay,
      measured in the protozoa Uronema parduczi Chatton-Lwoff, was >50 mg/L 
      (Verschueren 1983).

   B. Toxicity to Terrestrial Organisms

      Based on the low toxicity of cyclohexane to laboratory animals, the 
      toxicity of the chemical to terrestrial animals is expected to be 
      low.

   C. Abiotic Effects

      Limited information indicates cyclohexane may have potential to 
      contribute to the formation of photochemical smog.  U.S.  EPA has 
      denied a petition to delist cyclohexane from the Toxic Release 
      Inventory on this basis and on the lack of adequate health effects 
      information.  The ozone-forming potential for cyclohexane has been 
      measured as 2 on a scale of 5 (HSDB 1994).  Ozone-forming potential 
      is an indicator of the smog-forming potential of a chemical.

VI. EPA/OTHER FEDERAL AND OTHER GROUP ACTIVITY

    The Clean Air Act Amendments of 1990 list cyclohexane as a hazardous 
    air pollutant.  Occupational exposure to cyclohexane is regulated by 
    the Occupational Safety and Health Administration  (OSHA).  The 
    permissible exposure limit (PEL) is 300 parts per million parts of air 
    (ppm) as an 8-hour time-weighted average (TWA) (29 CFR 1910.1000).

    Federal agencies and other groups that can provide additional
    information on cyclohexane are summarized in Tables 4 and 5.

                   TABLE 4.  EPA OFFICES AND CONTACT 
                 NUMBERS FOR INFORMATION ON CYCLOHEXANE
________________________________________________________________________
EPA OFFICE            LAW                                PHONE NUMBER
________________________________________________________________________
Pollution Prevention  Toxic Substances Control Act
 & Toxics               (Sec. 4/8A/8D/8E)                (202) 554-1404
                      Emergency Planning and Community
                       Right-to-Know Act (EPCRA)
                        Regulations (Sec. 313)           (800) 424-9346
                        Toxics Release Inventory data    (202) 260-1531
Air                   Clean Air Act                      (919) 541-0888
Solid Waste &         Comprehensive Environmental
 Emergency Response    Response, Compensation, and
                       Liability Act (Superfund)/
                      Resource Conservation and Recovery
                       Act / EPCRA (Sec. 304/311/312)    (800) 424-9346
Water                 Clean Water Act                    (202) 260-7588
________________________________________________________________________

         TABLE 5.  OTHER FEDERAL OFFICE/OTHER GROUP CONTACT NUMBERS 
                        FOR INFORMATION ON CYCLOHEXANE
_______________________________________________________________________

Other Agency/Department/Group                     Contact Number
_______________________________________________________________________

American Conference of Governmental
   Industrial Hygienists
 Recommended TLV-TWA (see end note 2): 300 ppm
 (ACGIH 1993-1994))                                   (513) 742-2020  
Consumer Product Safety Commission                    (301) 504-0994
Food & Drug Administration                            (301) 443-3170
National Institute for Occupational Safety & Health
(Recommended TWA (see end note 3): 300 ppm
  (NIOSH 1990))                                       (800) 356-4674
Occupational Safety & Health Administration
(Permissible TWA (see end note 2): 300 ppm
  (OSHA 1993))
(Check local phone book for phone number under Department of Labor)
_______________________________________________________________________

VII. END NOTES

1. Standard Industrial Classification code is the statistical 
classification standard for all Federal economic statistics.  The code
provides a convenient way to reference economic data on industries of
interest to the researcher.  SIC codes presented here are not intended
to be an exhaustive listing; rather, the codes listed should provide an
indication of where a chemical may be most likely to be found in
commerce.

2. TLV-TWA, Threshold Limit Value-Time Weighted Average

3. TWA, Time-Weighted Average

VIII.  CITED REFERENCES

ACGIH.  1993-1994.  American Conference of Governmental Industrial
Hygienists.  1993-1994 Threshold Limit Values for Chemical Substances
and Physical Agents and Biological Exposure Indices.  ACGIH, Cincinnati,
OH.

ACGIH.  1991.  American Conference of Governmental Industrial
Hygienists.  Cyclohexane.  In:  Documentation of the Threshold Limit
Values and Biological Exposure Indices, 6th ed.  ACGIH, Cincinnati, OH,
pp. 355-356.

Budavari S, O'Neil MJ, Smith A, Heckelman PE (Eds.).  1989.  The Merck
Index, 11th ed.  Merck & Co., Inc., Rahway, NJ, p. 426.

CHEMFATE.  1994.  Syracuse Research Corporation's Environmental Fate
Data Bases.  Syracuse Research Corporation, Syracuse, NY.  Retrieved
8/15/94.

GENETOX. 1994. U.S. EPA GENETOX Program, computerized database.
Retrieved September, 1993.

HSDB.  1994.  Hazardous Substances Data Bank.  MEDLARS Online
Information Retrieval System, National Library of Medicine.  Retrieved
June, 1994.

Longacre SL.  1987.  Cyclohexane.  In:  Ethel Browning's Toxicity and
Metabolism of Industrial Solvents, 2nd ed.  Snyder R, Ed.  Elsevier,
Amsterdam, pp. 225-235.

Mannsville, 1993.  Chemical Products Synopsis, Cyclohexane. Mannsville
Chemical Products Corporation, 1993.

NIOSH.  1990.  National Institute for Occupational Safety and Health. 
1990.  NIOSH Pocket Guide to Chemical Hazards.  NIOSH, Cincinnati, OH,
pp. 76-77.

OSHA.  1993.  Occupational Safety and Health Administration.  Table Z-2. 
Limits for Air Contaminants. 29 CFR Part 1910 Part 1910, p. 35343.

Sandmeyer EE.  1981.  Cyclic hydrocarbons.  In:  Clayton GD, Clayton FE. 
1981-1982.  Patty's Industrial Hygiene and Toxicology, 3rd ed., Vol. 2C. 
New York:  John Wiley & Sons. pp. 3225, 3227-3228.

TRI92.  1994.  Toxic Chemical Release Inventory.  Office of Pollution
Prevention and Toxics, U.S. EPA, Washington, DC.

Verschueren K.  1983.  Handbook of Environmental Data on Organic
Chemicals, 2nd ed.  Van Nostrand Reinhold Co., New York, pp. 418-419.

APPENDIX A.  SOURCES SEARCHED FOR FACT SHEET PREPARATION

ACGIH.  1993-1994.  American Conference of Governmental Industrial
Hygienists.  11993-1994 Threshold Limit Values for Chemical Substances
and Physical Agents and Biological Exposure Indices.  ACGIH, Cincinnati,
OH.

AQUIRE. 1994. Aquatic Information Retrieval online data base. Chemical
Information Systems, Inc., a subsidiary of Fein-Marquart Assoc.

ATSDR.  1989-1994.  Agency for Toxic Substances and Disease Registry. 
Toxicological Profiles.  Chamblee, GA: ATSDR.

Budavari S, O'Neil MJ, Smith A, Heckelman PE (Eds.).  1989.  The Merck
Index, 11th ed.  Rahway, N.J.:  Merck & Co., Inc.

CHEMFATE.  1994.  Syracuse Research Corporation's Environmental Fate
Data Bases.  Syracuse Research Corporation, Syracuse, NY.

Clayton GD, Clayton FE.  1981-1982.  Patty's Industrial Hygiene and
Toxicology, 3rd ed., Vol. 2C.  New York:  John Wiley & Sons.

GENETOX. 1994. U.S. EPA GENETOX Program, computerized database. 

HSDB.  1994.  Hazardous Substances Data Bank.  MEDLARS Online
Information Retrieval System, National Library of Medicine.

IARC. 1979-1994. International Agency for Research on Cancer.  IARC
Monographs on the Evaluation of Carcinogenic Risk of Chemicals to Man.
Lyon: IARC.

NIOSH (National Institute for Occupational Safety and Health).  1992. 
NIOSH Recommendations for Occupational Safety and Health.  Compendium of
Policy Documents and Statements.  Cincinnati, OH:  NIOSH.

NIOSH.  1990.  National Institute for Occupational Safety and Health. 
1990.  NIOSH Pocket Guide to Chemical Hazards.  NIOSH, Cincinnati, OH.

NTP.  1994.  National Toxicology Program.  Toxicology and Carcinogenesis
Studies.  Tech Rep Ser.

NTP.  1994.  National Toxicology Program.  Management Status Report. 
Produced from NTP Chemtrack system.  April 8, 1994.  National Toxicology
Program, Research Triangle Park, NC.

OSHA.  1993.  Occupational Safety and Health Administration.  Table Z-2. 
Limits for Air Contaminants. 29 CFR Part 1910 Part 1910, p. 35343.

RTECS.  1994.  Registry of Toxic Effects of Chemical Substances. 
MEDLARS Online Information Retrieval System, National Library of
Medicine.

U.S. Air Force.  1989.  The Installation Restoration Toxicology Guide,
Vols. 1-5.  Wright-Patterson Air Force Base, OH.

U.S. EPA (U.S. Environmental Protection Agency).  1991.  Table 302.4
List of Hazardous Substances and Reportable Quantities 40 CFR, part
302.4:3-271.

U.S. EPA.  Most current.  Drinking Water Regulations and Health
Advisories.  Office of Drinking Water, U.S. Environmental Protection
Agency, Washington, D.C.

U.S. EPA.  Most Current.  Health Effects Assessment Summary Tables. 
Cincinnati, OH:  Environmental Criteria and Assessment Office, U.S.EPA.

U.S. EPA reviews such as Health and Environmental Effects Documents,
Health and Environmental Effect Profiles, and Health and Environmental
Assessments.

U.S. EPA.  1994.  Integrated Risk Information System (IRIS) Online. 
Cincinnati, OH:  Office of Health and Environmental Assessment.