EPA 749-F-94-021a CHEMICAL SUMMARY FOR TOLUENE prepared by OFFICE OF POLLUTION PREVENTION AND TOXICS U.S. ENVIRONMENTAL PROTECTION AGENCY August 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 These sources include online databases, unpublished EPA information, government publications, review documents, and standard reference materials.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 toluene are summarized in Table 1. TABLE 1. CHEMICAL IDENTITY AND CHEMICAL/PHYSICAL PROPERTIES OF TOLUENE ___________________________________________________________________________ Characteristic/Property Data Reference ___________________________________________________________________________ CAS No. 108-88-3 Common Synonyms Methyl benzene, Toluol, Phenylmethane Budavari et al. 1989 Molecular Formula C7H8 Chemical Structure Physical State Liquid Budavari et al. 1989 Molecular Weight 92.13 Budavari et al. 1989 Melting Point -95øC Budavari et al. 1989 Boiling Point 110.6øC Budavari et al. 1989 Water Solubility 470 mg/L @ 16øC; 515 mg/L @ 20øC Verschueren 1983 Density 0.87 g/mL @ 20øC Keith and Walters 1985 Vapor Density (air = 1) 3.14 Verschueren 1983 KOC 259 U.S. Air Force 1989 Log KOW 2.73 Leo 1983 Vapor Pressure 22.0 mm Hg @ 20øC Verschueren 1983 Reactivity Reacts vigorously with strong oxidizing agents and may generate heat or possibly ignite or explode. NFPA 1975 Flash Point 4.40øC closed cup Hawley 1981 Henry's Law Constant 6.61 X 10-3 atm m3/mol @ 25øC U.S. Air Force 1989 Fish Bioconcentration Factor 20 (in bluegill), 24 (in crayfish) U.S. EPA 1984 Odor Threshold 2.90 ppm (in air) U.S. Air Force 1989 Conversion Factors 1 ppm = 3.77 mg/m3 1 mg/m3 = 0.27 ppm U.S. EPA 1990 ___________________________________________________________________________ II. PRODUCTION, USE, AND TRENDS A. Production Almost all toluene is derived from petroleum processing; most is never recovered. This 'contained' toluene, estimated to consider- ably exceed one billion pounds annually, is incorporated directly into gasoline. There are 20 toluene-producing companies in the United States with the capacity to isolate at least 15 million gallons per year: Amerada Hess, American Petrofina, Amoco Oil, Ashland Oil, BP Chemicals, Champlin, Chevron Chemical, Coastal Corp., Dow Chemical, Exxon Chemical, Koch Industries, Lyondell Petrochemical, Marathon Oil, Mobil Oil, Oxy Petrochemicals, Phillips Petroleum, Shell Chemical, Sun Company, Texaco, and Triangle Refining. These companies represent over 90 percent of US capacity. Annual production capacity for toluene is estimated at 1.5 to 1.7 billion gallons. In 1991, just over 800 million gallons of toluene were isolated in the US. In the same year, 62 million gallons were imported and 52 million gallons were exported (Mannsville 1992). B. Use The largest use for toluene is in the production of benzene. Toluene is also used as an octane booster or enhancer in gasoline, as a raw material for toluene diisocyanate, as a solvent, and in solvent extraction processes. As a solvent, it may be used in aerosol spray paints, wall paints, lacquers, inks, adhesives, natural gums, and resins, as well as in a number of consumer products, such as spot removers, paint strippers, cosmetics, perfumes, and antifreezes. Table 2 shows the estimated 1992 US end-use pattern for toluene. C. Trends Demand for toluene in the US is expected to experience modest growth over the next several years. Growth in demand for toluene in gasoline appears to be slowing, and benzene demand is expected to grow at approximately 3 percent per year. Demand for toluene in other uses is expected to remain stable. TABLE 2. Estimated 1992 United States End-Use Pattern of Toluene ___________________________________________________________________________ Use of Toluene Percentage of all US Toluene Use (typical Standard Industrial Classification (SIC) Code) (see end note 1) ___________________________________________________________________________ Benzene production (production, SIC 2865; use, various industries) 50% Gasoline blending (production, SIC 2911; sold in SIC 5541; use, various industries) 30% Toluene diisocyanate production (production, SIC 2865; use, various industries) 7% Solvents (used in many industries, including 2851 and 2893) 6% Miscellaneous chemicals (production, SIC 28; use, various industries) 7% ___________________________________________________________________________ Source: Mannsville 1992. III. ENVIRONMENTAL FATE A. Environmental Release Of the total toluene released to the environment almost all is released to the air. Toluene is a volatile liquid [vapor pressure, 22 mm Hg at 20øC (Verschueren 1983)], and is released into the atmosphere from industrial and consumer uses. The largest sources of toluene release are the evaporation from gasoline, which is 5-7% toluene, and release through car exhausts. Spills of gasoline and industrial releases to surface water and soil are believed to be only a small fraction of the amount released to the atmosphere (ATSDR 1993). In 1992 releases of toluene to environmental media, as reported to the Toxic Chemical Release Inventory by certain types of U.S. industries totaled about 193 million pounds. Of this amount, a total of 191 million pounds (99%) were released to the atmosphere, 84 thousand pounds were released to surface water, 1.6 million pounds were released to underground injection sites, and 708 thousand pounds were released to land (TRI92 1994). Levels of toluene in environmental media range from 1-30 micro- grams/m3 in suburban and urban air and 0.1-2.9 micrograms/L in drinking water. Toluene contamination was detected in a maximum of only about 1.2% of the underground water supplies tested, however. The maximum air concentrations of toluene are found indoors and in one study ranged from 37.8 to 71.1 micrograms/m3. The increased concentration compared to urban outside air could originate from household products such as paints, thinners, glue, infiltration from auto emissions, and from cigarette smoke. Cigarettes contain about 80 micrograms toluene/cigarette (ATSDR 1993). B. Transport The majority of toluene evaporates to the atmosphere from the water and soil. It is moderately retarded by adsorption to soils rich in organic material (Koc = 259), therefore, transport to ground water is dependent on the soil composition (ATSDR 1993). In unsaturated topsoil containing organic material, it has been estimated that 97% of the toluene is adsorbed to the soil and only about 2% is in the soil-water phase and transported with flowing groundwater. There is little retardation in sandy soils and 2-13% of the toluene was estimated to migrate with flowing water; the remainder was volatilized, biodegraded, or unaccounted for. In saturated deep soils with no soil-air phase, about 48% may be transported with flowing groundwater (U.S. Air Force 1989). C. Transformation/Persistence 1. Air - The main degradation pathway for toluene in the atmosphere is reaction with photochemically produced hydroxyl radicals. The estimated atmospheric half life for toluene is about 13 hours. Toluene is also oxidized by reactions with atmospheric nitrogen dioxide, oxygen, and ozone, but these are minor degradation pathways. Photolysis is not considered a significant degradative pathway for toluene (ATSDR 1993). 2. Soil - In surface soil, volatilization to air is an important fate process for toluene (U.S. Air Force 1993). Biodegradation of toluene has been demonstrated in the laboratory to occur with a half life of about 1 hour. In the environment, biodegradation of toluene to carbon dioxide occurs with a typical half life of 1-7 days (ATSDR 1993). 3. Water - An important fate process for toluene is volatilization, the rate of which depends on the amount of turbulence in the surface water (ATSDR 1993). The volatilization of toluene from static water has a half life of 1-16 days, whereas from turbulent water the half life is 5-6 hours. Degradation of toluene in surface water occurs primarily by biodegradation with a half life of less than one day under favorable conditions (presence of microorganisms, microbial adaptation, and optimum temperature). Biodegradation also occurs in shallow groundwater and in salt water at a reduced rate (ATSDR 1993). No data are available on anaerobic degradation of toluene in deep ground water conditions where aerobic degradation would be minimal (ATSDR 1993). 4. Biota - Bioaccumulation in most organisms is limited by the metabolism of toluene into more polar compounds that have greater water solubility and a lower affinity for lipids. Bioaccumulation in the food chain is predicted to be low (ATSDR 1993; U.S. EPA 1990). IV. HUMAN HEALTH EFFECTS A. Pharmacokinetics 1. Absorption - Studies in humans and animals have demonstrated that toluene is readily absorbed via the lungs and the gastrointestinal tract. Absorption through the skin is estimated at about 1% of that absorbed by the lungs when exposed to toluene vapor. Dermal absorption is expected to be higher upon exposure to the liquid; however, exposure is limited by the rapid evaporation of toluene (Faust 1994). 2. Distribution - In studies with mice exposed to radiolabeled toluene by inhalation, high levels of radioactivity were present in body fat, bone marrow, spinal nerves, spinal cord, and brain white matter. Lower levels of radioactivity were present in blood, kidney, and liver. Accumulation of toluene has generally been found in adipose tissue, other tissues with high fat content, and in highly vascularized tissues (Faust 1994). 3. Metabolism - The metabolites of inhaled or ingested toluene include benzyl alcohol resulting from the hydroxylation of the methyl group. Further oxidation results in the formation of benzaldehyde and benzoic acid. The latter is conjugated with glycine to yield hippuric acid or reacted with glucuronic acid to form benzoyl glucuronide. o- cresol and p-cresol formed by ring hydroxylation are considered minor metabolites (Faust 1994). 4. Excretion - Toluene is primarily (60-70%) excreted through the urine as hippuric acid. The excretion of benzoyl glucuronide accounts for 10-20%, and excretion of unchanged toluene through the lungs also accounts for 10-20%. Excretion of hippuric acid is usually complete within 24 hours after exposure (U.S. EPA 1990). B. Acute Toxicity Humans exposed to intermediate to high levels of toluene for short periods of time experience adverse central nervous system effects ranging from headaches to intoxication, convulsions, narcosis, and death. Similar effects are observed in short-term animal studies. 1. Humans - Toluene ingestion or inhalation can result in severe central nervous system depression, and in large doses, can act as a narcotic. The ingestion of about 60 mL resulted in fatal nervous system depression within 30 minutes in one reported case. Constriction and necrosis of myocardial fibers, markedly swollen liver, congestion and hemorrhage of the lungs and acute tubular necrosis were found on autopsy (Faust 1994). Central nervous system effects (headaches, dizziness, intox- ication) and eye irritation occurred following inhalation exposure to 100 ppm toluene 6 hours/day for 4 days. Exposure to 600 ppm for 8 hours resulted in the same and more serious symptoms including euphoria, dilated pupils, convulsions, and nausea (U.S. EPA 1994). Exposure to 10,000-30,000 ppm has been reported to cause narcosis and death (U.S. Air Force 1989). Toluene can also strip the skin of lipids causing dermatitis (Keith and Walters 1985). 2. Animals - LD50/LC50 values for rats, reported in the literature searched, are as follows for the various routes of exposure: 5.3-5.9 g/kg (oral), 4618 ppm for 6 hours (respiratory), 1.64 g/kg (i.p. injection) (U.S. EPA 1990). An LC50 value for mice of 5320 ppm for 7 hours was reported, and a rabbit LD50 of 14.1 mL/kg (12.3 g/kg) was reported for dermal exposure (U.S. EPA 1990). The initial effects are instability and incoordination, lacrimation and sniffles (respiratory exposure), followed by narcosis. Animals die of respiratory failure from severe nervous system depression. Cloudy swelling of the kidneys was reported in rats following inhalation exposure to 1600 ppm, 18-20 hours/day for 3 days (U.S. EPA 1990). C. Subchronic/Chronic Effects Repeat doses of toluene cause adverse central nervous system effects and can damage the upper respiratory system, the liver, and the kidney. Adverse effects occur as a result from both oral and the inhalation exposures. A reported lowest-observed-effect level in humans for adverse neurobehavioral effects is 88 ppm. EPA has derived both an oral RfD (0.2 mg/kg/day) and an inhalation RfC (0.4 mg/m3) for toluene exposures. 1. Humans - Chronic occupational exposure and incidences of toluene abuse have resulted in hepatomegaly and liver function changes. It has also resulted in nephrotoxicity and, in one case, was a cardiac sensitizer and fatal cardiotoxin. Neural and cerebellar dystrophy were reported in several cases of habitual "glue sniffing." An epidemiological study in France on workers chronically exposed to toluene fumes reported leukopenia and neutropenia. Exposure levels were not given in the secondary reference; however, the average urinary excretion of hippuric acid, a metabolite of toluene, was given as 4 g/L compared to a normal level of 0.6 g/L (Sandmeyer 1989). 2. Animals - The major target organs for the subchronic/chronic toxicity of toluene are the nervous system, liver, and kidney. Depressed immune response has been reported in male mice given doses of 105 mg/kg/day for 28 days (Faust 1994). Toluene in corn oil administered to F344 male and female rats by gavage 5 days/week for 13 weeks, induced prostration, hypoactivity, ataxia, piloerection, lacrimation, excess salivation, and body tremors at doses ò2500 mg/kg. Liver, kidney, and heart weights were also increased at this dose and histopathologic lesions were seen in the liver, kidneys, brain and urinary bladder. The no-observed-adverse effect level (NOAEL) for the study was 312 mg/kg (223 mg/kg/day) and the lowest-observed-adverse effect level (LOAEL) for the study was 625 mg/kg (446 mg/kg/day) (U.S. EPA 1994). Based on these data, the U.S. EPA (1994) calculated a chronic RfD (reference dose) for toluene of 0.2 mg/kg/day. A 13-week gavage study was also performed in B6C3F1 mice. Central nervous system effects were seen including subconvulsive jerking, prostration, impaired grasping reflex, bradypnea, hypo- thermia, ataxia, and hypoactivity. Body weight loss was seen in males at 2500 mg/kg; however, no other changes were noted. The NOAEL for this study was 1250 mg/kg. In an inhalation study with toluene, degeneration in the olfactory and respiratory epithelium of the nasal cavity was observed in Fisher 344 rats exposed 6.5 hours/day, 5 days/week for 103 weeks to 600 ppm toluene. A LOAEL of 600 ppm was determined, but a NOAEL could not be determined from the study (U.S. EPA 1994). Based on these data and the LOAEL of 88 ppm (332 mg/m3) from a human epidemiological study (Section IV G), the U.S. EPA (1994) calculated a chronic inhalation reference concentration (RfC) of 0.4 mg/m3 for toluene from the human exposure data. D. Carcinogenicity There is inadequate evidence for the carcinogenicity of toluene in both human and animal studies. 1. Humans - Epidemiology studies revealed no significant increased risk for cancer among workers who were exposed to toluene for at least 5 years. In one study, the incidence of respiratory tract tumors was increased among all workers exposed for a minimum of 3 months. However, when only those workers exposed for 5 years and a latency period of 10 years were considered, the significance of the increase was lost. In another study, the cohort exposed to toluene and other chemicals experienced fewer cancer deaths than the general population (Faust 1994). 2. Animals - Sprague-Dawley rats were given 500 mg toluene/kg 4-5 days/week for 2 years. At the end of the study, 8% of the treated males and 17.5% of the treated females developed hemolymphoreticular neoplasms compared to 7% of the male and 3% of the female controls. Two long-term inhalation studies in rats and mice found no evidence of toluene carcinogenicity. Rats were given up to 300 ppm, 6 hours/day, 5 days/week for 24 months. Mice were given 600 or 1200 ppm, 6.5 hours/day, 5 days/week for 24 months. Based on no human and inadequate animal data, the U.S. EPA cancer classification for toluene is D, not classified (U.S. EPA 1994). E. Genotoxicity Toluene has been extensively tested in a variety of genotoxicity tests. Toluene has been shown to be negative for gene mutations in bacteria, in yeast, and in the fruit fly. Conflicting results have been reported in mammalian cell tests. In vitro mammalian cell tests (including human cells) for sister chromatid exchange and chromosome aberrations have been reported as negative. Toluene was positive in rodent micronucleus tests when administered by injection but negative when administered by the oral route (McGregor 1994). F. Developmental/Reproductive Toxicity Exposures to high levels of toluene can result in adverse effects in the developing human fetus. Several studies have indicated that high levels of toluene can also adversely effect the developing offspring in laboratory animals. 1. Humans - Variable growth, microcephaly, CNS dysfunction, attentional deficits, minor craniofacial and limb abnormal- ities, and developmental delay were seen in three children exposed to toluene in utero as a result of maternal solvent abuse before and during pregnancy (U.S. EPA 1994). 2. Animals - Sternebral alterations, extra ribs, and missing tails were reported following treatment of CFY rats with 1500 mg/m3 toluene 24 hours/day during days 9-14 of gestation. Two of the dams died during the exposure. Another group of CFY rats received 1000 mg/m3 8 hours/day during days 1-21 of gestation. No maternal deaths or toxicity occurred, however, minor skeletal retardation was present in the exposed fetuses. CFLP Mice were exposed to 500 or 1500 mg/m3 toluene continuously during days 6-13 of pregnancy. All dams died at the high dose during the first 24 hours of exposure, however none died at 500 mg/m3. Decreased fetal weight was reported, but there were no differences in the incidences of skeletal malformations or anomalies between the treated and control offspring (U.S. EPA 1994). G. Neurotoxicity Available information indicate that toluene adversely affects the central nervous system of humans (by inhalation) and of laboratory animals (by oral and inhalation). 1. Humans - A battery of neurobehavioral tests were administered to workers exposed to 88 ppm (332 mg/m3, TWA) toluene and to a control group exposed to 13 ppm (49 mg/m3). A lowest- observed-adverse effect level (LOAEL) of 88 ppm (332 mg/m3) for neurobehavioral changes was determined (U.S.EPA 1994). Nervous system effects including fatigue, muscular weakness, confusion, impaired coordination, slight exhilaration, enlarged pupils and accommodation disturbances were reported in humans chronically exposed to 200-800 ppm toluene, 7-8 hours/day (U.S. EPA 1994). Exposure to 100 ppm for 6 hours resulted in fatigue, sleepiness, decreased manual dexterity, decreased color discrimination, and decreased accuracy in visual perception. The concentration of 100 ppm is roughly equivalent to 40.39 mg/kg over the 6-hour period. Prolonged abuse was reported to result in altered electroen- cephalogram, ataxia, tremors, CNS atrophy, and impaired speech, hearing, and vision (ATSDR 1993). Magnetic resonance imaging and brainstem auditory evoked response evaluations of the brains of chronic solvent abusers indicate that there are permanent changes in brain structure that correlate with the degree of dysfunction suggesting the neurological symptoms may result from permanent structural changes in the brain (ATSDR 1993). 2. Animals - Alterations in the concentrations of CNS neuro- transmitters were reported in male CD-1 mice following treatment with 5-105 mg toluene/kg/day given in drinking water for 28 days. The neurotransmitters affect mood, emotional state, and aggressive behavior. Exposure of mice to 1250 and 2500 mg/kg/day for 13 weeks resulted in increased relative brain weight in male mice at 2500 mg/kg/day and necrosis of brain tissue at both doses. Acute inhalation exposure of monkeys to 1000 and 2000 ppm toluene, which are below the concentrations known to cause neurological impairment, were reported to impair cognitive and motor abilities. Disturbances in the vestibular and optooculomotor systems of rats resulted from acute exposure to 1500 ppm toluene. Exposure of rats to 1500 ppm for 1 hour/day for 14 days also resulted in nystagmus. The cerebellum was suggested as a target site of toluene (ATSDR 1993). Exposure of rats to 1200 ppm for 5 weeks or 1000 ppm for 2 weeks produced permanent high-frequency hearing loss. The hearing loss occurred whether or not the exposure was continuous or episodic and was compounded by post-exposure high noise levels (ATSDR 1993). Decreased neuromuscular performance has been recorded in several studies. A single exposure for 4 hours to 810-6250 ppm toluene resulted in impaired performance in tests designed to measure neuromuscular performance. Daily 15 minute exposure to toluene for up to 4 weeks resulted in a dose- related increase on righting-reflex latency time. A decline in the ability of animals to perform trained neuromuscular responses was also seen following exposure of rats to 125-500 ppm toluene for 4 hours. In this case, recovery occurred in about 2 hours (ATSDR 1993). V. ENVIRONMENTAL EFFECTS A. Toxicity to Aquatic Organisms Toluene has moderate acute toxicity to aquatic organisms; several toxicity values are in the range of greater than 1 mg/L and 100 mg/L. Ninety-six-hour LC50 values for fish are: 12.6-72.0 mg/L for Pimephales promelas (fathead minnow), 13-24 mg/L for Lepomis macrochirus (bluegill), 28.2-59.3 mg/L for Poecilia reticulata (guppy), 240 mg/L for Ictalurus punctatus (channel catfish), and 22.8-57.68 g/L for Carassius auratus (goldfish) (AQUIRE 1994). Ninety-six-hour LC50 values for crustaceans are: 9.5 ppm for Palaemonetes pugio (grass shrimp), 28 ppm for Cancer magister (crab larvae stage 1), 4.3 ppm for Crangon franciscorum (shrimp), and 9.5 mg/L for Palaemonetes pugio (daggerblade grass shrimp) (AQUIRE 1994). The EC50 values for various parameters in algae are: 245 mg/L, growth, 24 hours for Chlorella vulgaris (green algae); 20 mg/L, photosynthesis effect, 8 hours for Skeletonema costatum (diatom); and 12.5 mg/L, growth, 72 hours for Selenastrum capricornutum (green algae) (AQUIRE 1994). B. Toxicity to Terrestrial Organisms No information was found in the secondary sources searched for terrestrial organism toxicity. The oral LD50 in the rat, 5.3-5.9 g/kg), suggests that the chemical would not be acutely toxic to terrestrial animals unless present in very high concentra- tions. Studies in laboratory animals also suggest that toluene would not cause developmental/reproductive effects in terrestrial species at expected environmental levels (see section IV.F). C. Abiotic Effects No information on abiotic effects of toluene was located in the secondary references. According to the definition provided in the Federal Register (1992), toluene is a volatile organic compound (VOC) substance. As a VOC, toluene can contribute to the formation of photochemical smog in the presence of other VOCs. VI. EPA/OTHER FEDERAL/OTHER GROUP ACTIVITY Voluntary reduction of toluene environmental releases has occurred since 1991, as a result of a joint industry/EPA pollution prevention initiative, the 33/50 program. The Clean Air Act Amendments of 1990 list toluene as a hazardous air pollutant. Occupational exposure to toluene is regulated by the Occupational Safety and Health Administra- tion (OSHA). The permissible exposure limit (PEL) is 200 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 informa- tion on toluene are listed in Tables 3 and 4. TABLE 3. EPA OFFICES AND CONTACT NUMBERS FOR INFORMATION ON TOLUENE ________________________________________________________________________ EPA OFFICE LAW PHONE NUMBER ________________________________________________________________________ Pollution Prevention Toxic Substances Control Act & Toxics (Sec. 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 Safe Drinking Water Act (Drinking Water Standard: 1.0 mg/L) (800) 426-4791 _________________________________________________________________________ TABLE 4. OTHER FEDERAL OFFICES/OTHER GROUP CONTACT NUMBERS FOR INFORMATION ON TOLUENE ___________________________________________________________________________ Other Agency/Department/Other Group Contact Number ___________________________________________________________________________ Agency of Toxic Substances & Disease Registry (404) 639-6000 American Conference of Governmental Industrial Hygienists (Recommended Exposure Limit: 50 ppm) (513) 742-2020 Consumer Product Safety Commission (301) 504-0994 Food & Drug Administration (301) 443-3170 National Institute for Occupational Safety & Health (Recommended Exposure Limit: 100 ppm) (800) 356-4674 Occupational Safety & Health Administration Check local phone (Permissible Exposure Limit: 200 ppm) 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. VIII. CITED REFERENCES AQUIRE. 1994. EPA ERL-Duluth's Aquatic Ecotoxicology Data Systems. U.S. EPA, Duluth, MN. Retrieved July 1994. ATSDR. 1993. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Toluene. U.S. Department of Health and Human Services, Public Health Service. Atlanta, GA. Budavari S, O'Neil MJ, Smith A, Heckelman PE (Eds.). 1989. The Merck Index, 11th ed. Rahway, N.J.: Merck & Co., Inc. Faust, R.A. 1994. Toxicity Summary for Toluene. U.S. Army Environmental Center, Aberdeen Proving Ground, Maryland. Federal Register. 1992. 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