Scope Study for Expanding the Great Lakes Toxic Emission Regional Inventory to include Estimated Emissions from Mobile Sources

Chapter 2 Identification and Characterization of Toxic Air Pollutants from Mobile Sources

• 2-1. Chemicals of Concern
  • 2-1-1. Section 112(b) of the 1990 Clean Air Act Amendments
  • 2-1-2. Section 112(c)(6) of the 1990 Clean Air Act Amendments
  • 2-1-3. Great Lakes Regional Air Toxic Emission Inventory Project
  • 2-1-4. EPA Final Water Quality Guidance for the Great Lakes System
  • 2-1-5. U.S. EPA First Report to Congress on Deposition of Air Pollutants to the Great Waters
  • 2-1-6. Great Lakes Water Quality Agreement between the United States and Canada
• 2-2. Chemicals Emitted from Mobile Sources
  • 2-2-1. EPA SPECIATE Version 1.5
  • 2-2-2. State of California Air Resource Board Speciation Manual, Second Edition
  • 2-2-3. Auto/Oil Air Quality Improvement Research Program Database
  • 2-2-4. Cumulative Exposures to Air Toxics: Emission Inventories for Mobile and Stationary Sources
  • 2-2-5. EPA Factor Information Retrieval System version 5.1
  • 2-2-6. Pollutants of Concern and Emitted from Mobile Sources
• 2-3. Pollutant Characterization
  • 2-3-1. Acetaldehyde
  • 2-3-2. Acridine
  • 2-3-3. Acrolein
  • 2-3-4. Anthracene
  • 2-3-5. Benzene
  • 2-3-6. Benzo(a)pyrene (B[a]P)
  • 2-3-7. Benzo(ghi)perylene
  • 2-3-8. Benz(a)anthracene
  • 2-3-9. Biphenyl
  • 2-3-10. 1,3-Butadiene
  • 2-3-11. Chlorine
  • 2-3-12. Chlorobenzene
  • 2-3-13. Chrysene
  • 2-3-14. Cresols
  • 2-3-15. Cumene
  • 2-3-16. Cyclohexane
  • 2-3-17. 1,4-Dichlorobenzene
  • 2-3-18. Ethylbenzene
  • 2-3-19. Ethylene Dibromide (Dibromoethane)
  • 2-3-20. Fluoranthene
  • 2-3-21. Formaldehyde
  • 2-3-22. Hexane
  • 2-3-23. Isoprene (2-Methyl-1,3-butadiene)
  • 2-3-24. Methanol
  • 2-3-25. Methyl Chloroform (1,1,1-Trichloroethane)
  • 2-3-26. Methyl Ethyl Ketone (2-Butanone)
  • 2-3-27. Methyl Tert Butyl Ether
  • 2-3-28. Naphthalene
  • 2-3-29. Perylene
  • 2-3-30. Phenanthrene
  • 2-3-31. Phenol
  • 2-3-32. Propionaldehyde
  • 2-3-33. Pyrene
  • 2-3-34. Styrene
  • 2-3-35. Toluene
  • 2-3-36. 2,2,4-Trimethylpentane
  • 2-3-37. Xylenes (Isomers and Mixture)
  • 2-3-38. m-Xylene
  • 2-3-39. o-Xylene
  • 2-3-40. p-Xylene
  • 2-3-41. Aluminum and Compounds
  • 2-3-42. Ammonia and Compounds
  • 2-3-43. Antimony and Compounds
  • 2-3-44. Arsenic and Compounds (Inorganic Including Arsine)
  • 2-3-45. Barium and Compounds
  • 2-3-46. Bromine and Compounds
  • 2-3-47. Cadmium and Compounds
  • 2-3-48. Calcium and Compounds
  • 2-3-49. Chromium and Compounds
  • 2-3-50. Cobalt and Compounds
  • 2-3-51. Copper and Compounds
  • 2-3-52. Cyanide Compounds
  • 2-3-53. Iron and Compounds
  • 2-3-54. Lead and Lead Compounds
  • 2-3-55. Manganese and Compounds
  • 2-3-56. Mercury and Compounds
  • 2-3-57. Nickel and Compounds
  • 2-3-58. Nitrogen Compounds
  • 2-3-59. Phosphorus and compounds
  • 2-3-60. Potassium and Compounds
  • 2-3-63. Sodium and Compounds
  • 2-3-64. Strontium and Compounds
  • 2-3-65. Sulfur Compounds
  • 2-3-66. Titanium and Compounds
  • 2-3-67. Vanadium and Compounds
  • 2-3-68. Zinc and Compounds
  • 2-3-69. Zirconium and Compounds
  • 2-3-70. Total Polycyclic Aromatic Hydrocarbons (PHAs)
  • 2-3-71. Polycyclic Organic Matter (POM)
• 2-4. References

2-1. Chemicals of Concern

A chemical of concern, as used in this scope study, is one addressed in any of the following documents:

• Section 112(b) of the 1990 Clean Air Act Amendments (CAA, 1990)
• Section 112(c)(6) of the 1990 Clean Air Act Amendments (CAA, 1990)
• Great Lakes Regional Air Toxics Emission Inventory Project (Radian, 1994)
• EPA Final Water Quality Guidance for the Great Lakes System (EPA, 1995)
• U.S. EPA first report to Congress on deposition of air pollutants to the Great Waters (EPA, 1994)
• Great Lakes Water Quality Agreement between the United States and Canada (IJC, 1987)

The criteria for selection of pollutants in each document are described below.

2-1-1. Section 112(b) of the 1990 Clean Air Act Amendments

The 1990 Clean Air Act Amendments (CAA) define the term "hazardous air pollutant (HAP)" as any air pollutant listed in Section 112(b). EPA periodically reviews the list, adding or deleting pollutants as appropriate. EPA shall add pollutants that "present, or may present, through inhalation or other routes of exposure, a threat of adverse human health effects (including, but not limited to, substances which are known to be, or may reasonably be anticipated to be, carcinogenic, mutagenic, teratogenic, neurotoxic, which cause reproductive dysfunction, or which are acutely or chronically toxic) or adverse environmental effects whether through ambient concentrations, bioaccumulation, deposition, or otherwise..." (CAA, 1990). EPA shall delete a substance upon a showing that "there is adequate data on the health and environmental effects of the substance to determine that emissions, ambient concentrations, bioaccumulation or deposition of the substance may not reasonably be anticipated to cause adverse effects to the human health or adverse environmental effects." (CAA, 1990).

2-1-2. Section 112(c)(6) of the 1990 Clean Air Act Amendments

The CAA also list 7 specific pollutants in Section 112(c)(6). These pollutants are Great Lakes HAPs of concern. EPA must, not later that 5 years after the date of enactment of the 1990 CAA, "list categories and subcategories of sources assuring that sources accounting for not less than 90 per centum of the aggregate emissions of each such pollutant are subject to" emission standards.

2-1-3. Great Lakes Regional Air Toxic Emission Inventory Project

The list of target compounds in the Great Lakes Regional Air Toxic Emission Inventory Project (RAPIDS) (Radian, 1994) are identified as significant contributors to the contamination of the Great Lakes. This list includes 49 pollutants addressed in the Great Lakes Water Quality Agreement between the United States and Canada (IJC, 1987) and in Section 112(c)(6) of the CAA, pollutants suggested by individual Great Lakes States, the U.S. EPA Office of Air Quality Planning and Standards, Factor Information Retrieval (FIRE) System developers, U.S. EPA Great Waters/Section 112(m) and Urban Area Source 112(c)(6) program staff.

2-1-4. EPA Final Water Quality Guidance for the Great Lakes System

EPA and the Great Lakes States established a list for the chemicals of most concern because of the physical, chemical, and biological characteristics of the Great Lakes system, and the documented environmental harm to the ecosystem from the past and continuing presence of these types of pollutants. This list consists of two parts: pollutants that are bioaccumulative chemicals of concern (BCCs) and pollutants that are not bioaccumulative chemicals of concern. The definition of a bioaccumulative chemical of concern in the EPA Final Water Quality Guidance for the Great Lakes System (GLWQI) (1995) is "any chemical that has the potential to cause adverse effects which, upon entering the surface water, by itself or as its toxic transformation products in aquatic organisms by a human health bioaccumulation factor greater than 1000, after considering metabolism and other physicochemical properties that might enhance or inhibit bioaccumulation..." Chemicals with half-lives of less than eight weeks in the water column, sediment, and biota are not BCCs. BCCs include, but are not limited to, the pollutants identified as BCCs in the GLWQI.

2-1-5. U.S. EPA First Report to Congress on Deposition of Air Pollutants to the Great Waters

Fifteen pollutants are addressed in the EPA’s first report to Congress on deposition of air pollutants to the Great Waters (EPA, 1994). All of them are known air pollutants in the vicinity of at least some of the Great Waters and to be present in atmospheric deposition. Also, all of the pollutants, except nitrogen, are persistent in the environment, have the potential to bioaccumulate, and have high toxic potencies to humans and the environment. The potential effects associated with exposure to these pollutants (except for nitrogen) include cancer, effects to the reproductive system and endocrine system (hormone production and function system), developmental effects, neurological effects, and other non-cancer effects. Nitrogen compounds are considered because of nitrogen’s role in nutrient enrichment in coastal waters and because of significant atmospheric loadings of nitrogen to Chesapeake Bay. Excessive loadings of nitrogen can cause accelerated eutrophication and oxygen depletion, resulting in ecological effects such as reduced fish and shellfish populations.

2-1-6. Great Lakes Water Quality Agreement between the United States and Canada

Two categories of pollutants are identified in the Great Lakes Water Quality Agreement between the United States and Canada (GLWQA) by the International Joint Commission (IJC, 1987): hazardous polluting substances and potentially hazardous polluting substances. The criteria to be applied to the selection of substances as candidates for the first category are:

(a) Acute toxicological effects, as determined by whether the substance is lethal to:

1. One-half of the test population of aquatic animals in 96 hours or less at a concentration of 500 mg/L or less; or
2. One-half of the test population of animals in 14 days or less when administered in a single oral dose equal to or less that 50 mg/kg of body weight; or
3. One-half of the test population of animals in 14 days or less when dermally exposed to an amount equal to or less than 200 mg/kg of body weight for 24 hours; or
4. One-half of the test population of animals in 14 days or less when exposed to a vapor concentration equal to or less than 20 cm³/m³ in air for one hour; or
5. Aquatic flora as measured by a maximum specific growth rate or total yield of biomass which is 50 % lower than a control culture over 14 days in a medium at concentrations equal to or less than 100 mg/L.

(b) Risk of discharge into the Great Lakes System, as determined by:

1. Gathering information on the history of discharges or accidents;
2. Assessing the modal risks during transport and determining the use and distribution patterns;
3. Identifying quantities manufactured or imported.

The substances in the second category, potential hazardous polluting substances, are based on documented information concerning aquatic toxicity, mammalian and other vertebrate toxicity, phototoxicity, persistence, bioaccumulation, mutagenicity, teratogenicity, carcinogenicity, and environmental translocation or based on documented information on risk of discharge to the environment.

As discussed above, these various documents had different selection criteria that determined whether a pollutant was included as one of concern. Including all pollutants of concern from the six referenced documents provides the most comprehensive list of the chemicals that need to be considered for this scope study and this list is provided in Table 2-1. A total of 593 pollutants is shown in the list.

2-2. Chemicals Emitted from Mobile Sources

Chemicals can be emitted from mobile sources through direct vapor emissions and exhaust emissions. Hundreds of chemical compounds have been identified in mobile source emissions. In this section, air pollutants in six documents are reviewed:

• EPA SPECIATE Version 1.5 (EPA, 1993)
• State of California Air Resource Board Speciation Manual, Second Edition (CARB, 1991)
• Auto/Oil Air Quality Improvement Research Program database (Sawyer, 1993)
• Cumulative exposures to air toxics: emission inventories for mobile and stationary sources (Ligocki, 1995)
• U.S. Factor Information Retrieval System version 5.1a (EPA, 1996a)

Below is a discussion of the data contained in each of these documents.

2-2-1. EPA SPECIATE Version 1.5

The EPA SPECIATE Version 1.5 (EPA, 1993) contains about 700 chemical speciation profiles for particulate matter (PM) and volatile organic compounds (VOC) emissions. A wide variety of stationary point, stationary area, and mobile source categories are addressed by the profiles. These VOC/PM profiles are based on a variety of test data obtained from various research programs. Since the number of source categories, identified by Source Classification Codes (SCCs), is much larger than the available profiles, engineering judgment has also been used to link a VOC profile to a source category that does not have original test data. For several SCCs, industry-specific average profiles were developed from original profiles representing other SCCs within the same industry group.

2-2-2. State of California Air Resource Board Speciation Manual, Second Edition

The State of California Air Resource Board (CARB) Speciation Manual, Second Edition (CARB, 1991) uses mostly EPA’s VOC speciation profiles and has supplemented some of them with species data from other studies. The CARB Speciation Manual uses most of the PM profiles from a study done by KVB, Inc. (Taback, 1979). These profiles were developed, in a similar manner as used by EPA, from chemical analyses of emissions from various sources and the application of good engineering judgment in assigning a profile to emissions from an unanalyzed source category. Also, the CARB Speciation Manual has supplemented some PM profiles with species data from other studies.

2-2-3. Auto/Oil Air Quality Improvement Research Program Database

Hydrocarbon speciation of industry average gasoline, EPA certification gasoline, and M-85 (85% methanol, 15% gasoline) is from the Auto/Oil Air Quality Improvement Research Program database (Sawyer, 1993). The Auto/Oil Air Quality Improvement Research Program was established in 1989 by 14 oil companies and 3 domestic automakers. The overall objective of this program is to develop data to help legislators and regulators meet the nation’s clean air goals through extensive vehicle emission measurements, air-quality modeling studies to predict the effects of the measured emissions on ozone formation, and economic analysis of the fuel/vehicle systems.

2-2-4. Cumulative Exposures to Air Toxics: Emission Inventories for Mobile and Stationary Sources

Ligocki et al.(1995) reviewed speciation data that have been developed and used in recent years, including the speciation profiles in EPA SPECIATE Version 1.5, CARB Speciation Manual, Auto/Oil Air Quality Improvement Research Program database, and other documents. They modified these profiles to incorporate specific fuel properties that are characteristic of fuels sold in each EPA region. They also summarized the modified speciation profiles for HAPs and HAP precursors in total organic gases of mobile source emissions.

2-2-5. EPA Factor Information Retrieval System version 5.1

The EPA Factor Information Retrieval (FIRE) System version 5.1 contains emission factors which are recommended by the EPA. These emission factors are used to estimate air pollutant emissions when actual emission data are not available. In this version, the EPA compiled emission factors for a total of 337 toxic air pollutants. However, the information for mobile sources is limited to 10 toxic air pollutants for one vehicle type.

2-2-6. Pollutants of Concern and Emitted from Mobile Sources

Table 2-2 shows chemicals emitted from mobile sources, with associated references. A total of 371 chemicals and compound groups are identified in the table.

The secondary pollutant list shown in Table 2-3 includes those chemicals common to both Table 2-1, chemicals of concern, and Table 2-2, chemicals emitted from mobile sources. As mentioned previously, the chemical speciation was obtained based on a variety of test data. Because the laboratory analyses of PM provide elemental data only, and not what form the elements are in, the metals are listed as the element and its compounds in combination in Table 2-3 instead of individual metal compounds. The testing methods also do not provide sufficient information to determine the molecular makeup of the compounds containing the ions such as . Therefore, we grouped ammonia, cyanide, nitrogen, and sulfur- containing compounds. Results indicate seventy two pollutants emitted from mobile sources are of concern in the Great Lakes basin.

2-3. Pollutant Characterization

The information in this section provides brief characterizations of the pollutants in the secondary list (Table 2-3). For the first 41 individual chemicals, the characterizations include physical and chemical properties: physical descriptions, molecular weights, melting points, boiling points, formulas, vapor pressures, aqueous solubility, and specific gravities. Fire and explosion hazards are briefly summarized. Also included in the characterizations are human health impacts, such as carcinogenic and non-cancer effects, atmospheric reactivity, and environmental transfer and fate whenever the information is available. For the remaining 31 substances indicated as compound groups, many hundreds of chemicals belong to each group. We have selected representative members of each group and provided general information for each group and the selected chemicals.

2-3-1. Acetaldehyde

Acetaldehyde, CH₃CHO, is a flammable, volatile colorless fuming liquid with a characteristic green sweet, ripened apple odor (Verschueren, 1983; Sittig, 1985). Selected chemical and physical properties of acetaldehyde are shown in Table 2-4. Acetaldehyde can react vigorously with strong oxidizers, acids, bases, alcohol, ammonia. amines, phenols, ketones, HCN, and H₂S (Sittig, 1985; Keith, 1995).

Table 2-4. Selected chemical and physical properties of acetaldehyde

Acetaldehyde can enter the human body through inhalation of vapor and ingestion. It is also formed in the liver during ethanol metabolism. Exposure to low levels of vapor may cause skin, eye, mucous membrane, upper respiratory, and bronchi irritation. Repeated exposure may result in dermatitis, and rarely in skin sensitization. Acute exposure to high levels of acetaldehyde vapor may cause pulmonary edema, preceded by excitement, followed by narcosis (Sittig, 1985). Large doses may cause death due to respiratory paralysis. Evidence also shows that exposure to acetaldehyde may cause slow mental response, loss of intelligence, even unconsciousness, chronic respiratory disease, and kidney and liver damage (Keith, 1995).

2-3-2. Acridine

Acridine, C₁₃H₉N, is a colorless or light yellow crystal with a small needle shape (Sittig, 1985; Verschueren, 1983). It is very soluble in boiling water (Sittig, 1985). Selected chemical and physical properties of acridine are shown in Table 2-5. Inhalation of vapor is the route of entry of acridine into the human body. It is a severe irritant to conjunctiva of eyes, mucous membranes of the respiratory tract, and skin. It causes skin photosensitization and sneezing on inhalation. It may also cause yellowish discoloration of sclera and conjunctiva (Sittig, 1985).

Table 2-5. Selected chemical and physical properties of acridine

2-3-3. Acrolein

Acrolein, CH₂CHCHO, is a clear, yellowish liquid with a piercing, disagreeable odor (Sittig, 1985; Verschueren, 1983). Selected chemical and physical properties of acrolein are shown in Table 2-6. Acrolein is reactive and liable to polymerize violently. It is sensitive to heat, light, and air (Keith, 1995).

Table 2-6. Selected chemical and physical properties of acrolein

Acrolein can enter the human body through inhalation of vapor, percutaneous absorption, ingestion, and skin or eye contact. It causes intense irritation to eyes and mucous membranes of the respiratory tract. Prolonged or repeated exposure may result in skin burns and dermatitis. Acute exposure to acrolein may lead to bronchitis or pulmonary edema because of bronchial inflammation (Sittig, 1985). Exposure to acrolein may also cause delayed hypersensitivity with multiple organ involvement and central nervous system effects. Severe gastrointestinal distress with pulmonary congestion may occur due to ingestion of acrolein (Keith, 1995).

2-3-4. Anthracene

Anthracene, C₁₄H₁₀, is a colorless crystalline solid with violet fluorescence. It is combustible when exposed to heat, flame, or oxidizing materials. Anthracene is a skin irritant and allergen. Although experimental data have indicated its carcinogenic effects, there is not adequate evidence to classify anthracene as to human carcinogenicity (Lewis, 1992; EPA, 1996).

Anthracene one of the sixteen members of the polycyclic aromatic hydrocarbon (PAH) group. Selected chemical and physical properties of anthracene are shown in Table 2-7. For more information, please see Section 2-3-70, PAHs.

Table 2-7. Selected chemical and physical properties of anthracene

2-3-5. Benzene

Benzene, C₆H₆, is a clear, volatile, colorless, highly flammable liquid with a characteristic, sweet odor (Sittig, 1985; ATSDR 3, 1993). It is hygroscopic and sensitive to heat. Selected chemical and physical properties of benzene are shown in Table 2-8. Benzene is incompatible with oxidizers and strong acids (Keith, 1995). Although it is a highly stable aromatic hydrocarbon, it can react with a variety of chemicals primarily by substitution of a hydrogen atom (EPA, 1993a).

Table 2-8. Selected chemical and physical properties of benzene

Use of oil and gasoline is the main release of benzene to the environment. Benzene is easy to evaporate, and its vapor mixes with air very quickly. It breaks down within a few days in air, but more slowly in water. Benzene in liquid form also mixes easily with water. In water, it evaporates quickly into air. Benzene does not accumulate to high levels in plants and animals (ATSDR 3, 1993).

Because of its volatility, the most common route of exposure to benzene is inhalation (ATSDR 8803, 1989). Benzene can enter the human body through ingestion, skin and eye contact, but it is poorly absorbed through these routes (Sittig, 1985). Exposure to benzene may produce irritation to skin, eyes, and upper respiratory tract (Sittig, 1985; Keith, 1995). Acute exposure to benzene may cause central nervous system depression. Symptoms include headache, dizziness, nausea, convulsions, and coma (Sittig, 1985). Exposure to high levels may result in death (Sittig, 1985; ATSDR 8803, 1989). Benzene has been identified as a carcinogen by the U.S. Department of Health and Human Services. Epidemiological studies show that leukemia (cancer of the tissues that form the white blood cells) and subsequent death from cancer have occurred due to long-term exposure to benzene (ATSDR 8803, 1989). Chronic exposure to benzene may also affect normal blood production, possibly causing severe anemia and internal bleeding (Sittig, 1985; ATSDR 8803, 1989). In addition to its harmful effects on the tissues that form blood cells, benzene has adverse effects on the human immune system, lowering the body’s defense against infections and tumors. Generic changes have been also found associated with benzene exposures (ATSDR 8803, 1989).

2-3-6. Benzo(a)pyrene (B[a]P)

Benzo(a)pyrene, C₂₀H₁₂, is a yellowish crystal (Sittig, 1985). It consists of five benzene rings joined together. It combines with dust particles in the atmosphere and can be transported into water and onto soil and crops (ATSDR 8805, 1990). Selected chemical and physical properties of B[a]P are shown in Table 2-9. B[a]P is one of the most commonly found and hazardous members of the sixteen polycyclic aromatic hydrocarbon (PAH) compounds (see Section 2-3-70).

Table 2-9. Selected chemical and physical properties of benzo(a)pyrene

The general population may be exposed to B[a]P through inhalation of dust or other particles that contain B[a]P or ingestion of foods that are grown in B[a]P contaminated soil or air. Low levels of B[a]P have also been found in drinking water. Skin contact may cause small amounts of B[a]P to enter the body by absorption (ATSDR 8805, 1990). However, inhalation is the most common route by which B[a]P enters the body.

B[a]P has been reasonably determined to be a carcinogen. Harmful effects on the reproductive system also have been found in laboratory animals when they are exposed to B[a]P (ATSDR 8805, 1990).

2-3-7. Benzo(ghi)perylene

Benzo(ghi)perylene, C₂₂H₁₂, consists of six benzene rings joined together (Verschueren, 1983). It is stable in water, soil, and groundwater where it may persist for several years. However, benzo(ghi) perylene is easily broken down in air under sunlight where its environmental half life is about 0.3 to 3 hours (Howard, 1991). Selected chemical and physical properties of benzo(ghi)perylene are shown in Table 2-10. There is not adequate evidence to classify benzo(ghi)perylene as to human carcinogenicity (EPA, 1996). Benzo(ghi)perylene is one of the 16 polycyclic aromatic hydrocarbon (PAH) compounds for which more information is presented in Section 2-3-70.

Table 2-10. Selected chemical and physical properties of benzo(ghi)perylene

2-3-8. Benz(a)anthracene

Benz(a)anthracene, C₁₈H₁₂, is colorless leaflets or plates. Selected chemical and physical properties of 1,3-butadiene are shown in Table 2-11. EPA has been classified benz(a)anthracene as a probable human carcinogen. Although there are no human data that specifically link exposure to benz(a)anthracene to human cancers, benz(a)anthracene is a component of mixtures that have been associated with human cancers. Also sufficient data from animal bioassays suggest the carcinogenicity of benz(a)anthracene (EPA, 1996). Benz(a)anthracene is one of the sixteen PAHs, please refer Section 2-3-70 for more information.

Table 2-11. Selected chemical and physical properties of benz(a)anthracene

2-3-9. Biphenyl

Biphenyl, C₁₂H₁₀, is a white solid crystallizing in a scales with a pleasant odor (Keith, 1995; Lewis, 1992). It is insoluble in water but soluble in most organic solvents. It is combustible and can react with oxidizing materials. Biphenyl is one of the most thermally stable organic compounds (HSDB, 1991). Selected chemical and physical properties of 1,3-butadiene are shown in Table 2-12.

Table 2-12. Selected chemical and physical properties of biphenyl

Probable routes of human exposure to biphenyl are inhalation, ingestion, and eye and skin contact (HSDB, 1991). Biphenyl is a powerful irritant by inhalation, inhalation of very small amounts of biphenyl may cause flaccid paralysis, nausea, or vomiting (Lewis, 1992). Exposure to high vapor concentrations have reported peripheral and central nervous system effects, liver and kidney injury (HSDB, 1991). Long-term exposure may also result in effects of the central nervous system including headache, fatigue, tremor, insomnia, sensory impairment, and mood changes (Sittig, 1985). No data are available on the carcinogenic effects in humans (EPA, 1996).

2-3-10. 1,3-Butadiene

1,3-Butadiene, C₄H₆, is a colorless, flammable gas with a mild gasoline-like odor (Sittig, 1985; ATSDR 28, 1995). It evaporates very easily and moves quickly from water or soil to air. It also breaks down quickly in air by sunlight (ATSDR 28, 1995). Selected chemical and physical properties of 1,3-butadiene are shown in Table 2-13.

Table 2-13. Selected chemical and physical properties of 1,3-butadiene

1,3-butadiene can enter the body through inhalation and eye and skin contact. It is slightly irritating to the eyes, nose, and throat (Sittig, 1985). Exposure to high levels of 1,3-butadiene may cause central nervous system damage, blurred vision, nausea, fatigue, headache, decreased blood pressure and pulse rate, and unconsciousness. Low-level and long-term exposure to 1,3-butadiene may cause heart and lung damage, but this effect has not been fully studied. Animal studies show that inhalation of 1,3-butadiene can cause kidney and liver disease, lung damage, and birth defects. Based on animal studies, the Department of Health and Human Services has determined that 1,3-butadiene may reasonably be anticipated to be a carcinogen (ATSDR 28, 1995).

2-3-11. Chlorine

Chlorine, Cl₂, is a greenish-yellow gas with a pungent, irritating odor (Sittig, 1985; Keith, 1995). It is one of the most chemically reactive elements. Selected chemical and physical properties of chlorine are shown in Table 2-14.

Table 2-14. Selected chemical and physical properties of chlorine

Humans can be exposed to chlorine via inhalation and eye and skin contact (Sittig, 1985). Chlorine is extremely irritating to skin, eyes, mucous membranes, and the respiratory tract, and may cause corrosion of teeth (Sittig, 1985; Keith, 1995). In high concentrations, it acts as an asphyxiant causing cramps in muscles of the larynx (choking), swelling of the mucous membranes, nausea, vomiting, anxiety, and a temporary suspension of consciousness (Sittig, 1985). Tracheobronchitis, pulmonary edema, and pneumonia may supervene with acute exposures (Sittig, 1985; Keith, 1995).

2-3-12. Chlorobenzene

Chlorobenzene, C₆H₅Cl, is a colorless liquid with an almond-like odor (Sittig, 1985; ATSDR 9006, 1990). It reacts vigorously with oxidizers (Keith, 1995). Selected chemical and physical properties of chlorobenzene are shown in Table 2-15.

Table 2-15. Selected chemical and physical properties of chlorobenzene

Humans are potentially exposed to chlorobenzene by inhalation, ingestion, and eye and skin contact. When chlorobenzene enters the body, most of it is breathed out or excreted in urine (ATSDR 9006, 1990). Chlorobenzene is a strong narcotic and its vapor or mist is an irritant (Keith, 1995). Exposure to high levels of chlorobenzene may affect the brain, liver, and kidneys and cause headaches, numbness, sleepiness, nausea, and vomiting. Animal studies show some evidence of cancer risk from exposure to chlorobenzene, but the evidence is not sufficient to classify chlorobenzene as a human carcinogen (ATSDR 9006, 1990).

2-3-13. Chrysene

Chrysene, C₁₈H₁₂, is a crystal (Verschueren, 1983) consisting of four benzene rings joined together. Chrysene combines with dust particles in the air and can be transported into water and soil and onto crops (ATSDR 8811, 1990). Selected chemical and physical properties of chrysene are shown in Table 2-16.

Table 2-16. Selected chemical and physical properties of chrysene

People may be exposed to chrysene from air, water, and soil, but the most common way chrysene enters the body is through inhalation. Chrysene has been determined to be a possible human carcinogen by the International Agency for Research on Cancer (ATSDR 8811, 1990). It is one of the sixteen PAHs. More information is presented in Section 2-3-70.

2-3-14. Cresols

Cresols, C₇H₈O, are colorless solids, but usually they occur as a brown liquid mixture. Cresols have a medicinal odor (EPA, 1994c). They are flammable when exposed to heat and flame (Lewis, 1992). There are three forms of cresols: ortho-cresol (o-cresol), meta-cresol (m-cresol, and para-cresol (p-cresol). The o- and m- cresol are soluble in water and solutions of fixed alkali hydroxides. p-Cresol is soluble in organic solvents and volatile in steam (CARB, 1996). Selected chemical and physical properties of cumene are shown in Table 2-17.

Table 2-17. Selected chemical and physical properties of cresols

Cresols break down quickly in the environment, but may last longer in deep ground water or water where bacteria do not exist. Cresols do not appear to bioaccumulate (ATSDR 34, 1995).

Short-term inhalation exposure to cresols results in respiratory tract irritation, with symptoms such as dryness, nasal constriction, and throat irritation. Cresols are also strong dermal irritants. However, very little information is available on the long-term effects of cresols in humans. Only anecdotal information is available on the carcinogenic effects of mixed cresols in humans. Several animal studies suggest that o-cresol, m-cresol, and p-cresol may act as tumor promotors. EPA has classified o-cresol, m-cresol, and p-cresol as Group C, possible human carcinogens.

2-3-15. Cumene

Cumene, C₉H₁₂, is a colorless liquid with a sharp, penetrating aromatic odor (Keith, 1995). It can react with oxidizing materials (Keith, 1995). Selected chemical and physical properties of cumene are shown in Table 2-18.

Table 2-18. Selected chemical and physical properties of cumene

Inhalation, ingestion, and skin and eye contact are the routes of cumene entry to the body. It is mildly toxic by inhalation and skin contact, and moderately toxic by ingestion (Keith, 1995). Cumene may cause irritation of eyes and mucous membranes, headaches, dermatitis, narcosis, even coma (Sittig, 1985). Exposure to cumene can also act as a central nervous system depressant (Keith, 1995).

2-3-16. Cyclohexane

Cyclohexane, C₆H₁₂, is a colorless, flammable liquid with a mild, sweet odor. It reacts with oxidizers (Sittig, 1985). Selected chemical and physical properties of cyclohexane are shown in Table 2-19.

Table 2-19. Selected chemical and physical properties of cyclohexane

Cyclohexane can enter the body through inhalation, ingestion, and skin and eye contact. It has relatively low toxic potency in chronic exposure because it does not accumulate in the body. Repeated and prolonged contact with cyclohexane liquid may result in defatting of the skin and a dry, scaly, fissured dermatitis. Acute exposure to cyclohexane may cause mild conjunctivitis. It is a central nervous system depressant causing excitement, loss of equilibrium, stupor, coma, and, rarely, death (Sittig, 1985).

2-3-17. 1,4-Dichlorobenzene

1,4-Dichlorobenzene, C₆H₁₂, is a colorless or white, volatile crystal with a characteristic penetrating odor (Keith, 1995; ATSDR 8814, 1989). It is incompatible with oxidizing agents (Keith, 1995). Selected chemical and physical properties of 1,4-dichlorobenzene are shown in Table 2-20.

Table 2-20. Selected chemical and physical properties of 1,4-dichlorobenzene

1,4-Dichlorobenzene can enter the body through inhalation, ingestion, and skin and eye contact. The major route of 1,4-dichlorobenzene exposure is inhalation. High levels of 1,4-dichlorobenzene may cause headaches and dizziness (ATSDR 8814, 1989). Exposure to 1,4-dichlorobenzene may also lead to allergic skin reactions and damage to the liver and kidneys (Keith, 1995). Some evidence suggests that 1,4-dichlorobenzene exposure can cause birth defects. Based on animal studies, 1,4-Dichlorobenzene may reasonably be anticipated to be a human carcinogen (ATSDR 8814, 1989).

2-3-18. Ethylbenzene

Ethylbenzene, C₆H₅CH₂CH₃, is a clear, colorless, flammable liquid with a pungent gasoline-like odor (Keith, 1995, Sittig; 1985, ATSDR 9015, 1990). It can react vigorously with strong oxidizing agents (Keith, 1995). Selected chemical and physical properties of ethylbenzene are shown in Table 2-21. Ethylbenzene moves easily into air from water and soil. In air, it is broken down in about 3 days by reacting with other chemicals with the aid of sunlight. Ethylbenzene moves very quickly from soil to groundwater because of poor soil binding (ATSDR 9015, 1990).

Table 2-21. Selected chemical and physical properties of ethylbenzene

Ethylbenzene can enter the body rapidly and completely through inhalation and ingestion, and may also enter the body through skin and eye contact. Most ethylbenzene that enters the human body leaves in the urine within 2 days with a small amount released through the lungs and feces (ATSDR 9015, 1990).

Low-level exposure of ethylbenzene may cause irritation of the eyes and throat. Exposure to high levels of ethylbenzene may lead to more severe effects such as decreased movement and dizziness. Animal studies show that exposure to ethylbenzene may cause liver and kidney damage, nervous system changes, and blood changes. Ethylbenzene is not classifiable as to human carcinogenicity (ATSDR 9015, 1990).

2-3-19. Ethylene Dibromide (Dibromoethane)

Ethylene dibromide, BrCH₂CH₂Br, is a colorless, heavy, nonflammable liquid with a mild, sweet odor (Sittig, 1985; ATSDR 37, 1995). It was used as an additive in leaded gasoline, however, it is no longer used for this purpose under a ban of leaded gasoline. Ethylene dibromide is incompatible with oxidizing agents and reacts with chemically active metals such as sodium, potassium, calcium, powdered aluminum, zinc, magnesium, and liquid ammonia (Sittig, 1985; Keith, 1995). Selected chemical and physical properties of ethylene dibromide are shown in Table 2-22. Ethylene dibromide evaporates quickly from water and soil to air. In air, it breaks down slowly in about 4-5 months. Ethylene dibromide can move quickly through soil to groundwater. It breaks down in about 2 months in surface water, but is very difficult to break down in groundwater. Ethylene dibromide is unlikely to build up in plants or animals (ATSDR 37, 1990).

Table 2-22. Selected chemical and physical properties of ethylene dibromide

Ethylene dibromide can enter the body through inhalation, ingestion, and skin and eye contact (Sittig, 1985). As an irritant, it may cause skin, eye, mucous membrane and respiratory tract irritation (Keith, 1995). Based on animal studies, exposure to high levels of ethylene dibromide may result in liver and kidney damage, depression, collapse, and adverse effects on the brain (ATSDR 37, 1995). Death may occur due to respiratory or circulatory failure (Keith, 1995). Exposure to ethylene dibromide may also lead to reproductive changes and birth defects in animals (ATSDR 37, 1995). EPA has classified ethylene dibromide as a Group B2, probable human carcinogen (EPA, 1996).

2-3-20. Fluoranthene

Fluoranthene, C₁₆H₁₀, is a colorless solid. It is combustible when exposed to heat or flame. It is moderately toxic by ingestion and skin contact. Experiments show some evidence of its carcinogenic effects (Lewis, 1992). However, fluoranthene is not classifiable to human carcinogenicity because of a lack of human data and inadequate animal bioassays (EPA, 1996). It is one of the sixteen PAHs. Selected chemical and physical properties of fluoranthene are shown in Table 2-23. Section 2-3-70 discusses more detail information for the PAHs as a group.

Table 2-23. Selected chemical and physical properties of fluoranthene

2-3-21. Formaldehyde

Formaldehyde, HCHO, is a nearly colorless, combustible gas with a pungent, suffocating odor. It is the simplest member of the family of aldehydes. Formaldehyde is a strong reducing agent that reacts with strong oxidizers, strong alkalis, and acids (Keith, 1995). It is also incompatible with phenols and urea (Sittig, 1985). In the presence of air and moisture, formaldehyde readily polymerizes to paraformaldehyde at room temperature. Formaldehyde dissolves easily in water, alcohols, and other polar solvents. Selected chemical and physical properties of formaldehyde are shown in Table 2-24. Formaldehyde is sensitive to light, but oxidizes slowly in air (Keith, 1995).

Table 2-24. Selected chemical and physical properties of formaldehyde

Formaldehyde may enter the body through inhalation, ingestion, and skin and eye contact. Inhalation of formaldehyde may lead to irritation of eyes, mucous membranes, and the upper respiratory tract (Keith, 1995). Exposure to formaldehyde in high levels or for a long time can cause coughing or choking, and even death due to throat swelling or due to chemical burns to the lungs (ATSDR 9, 1995). Formaldehyde has been identified as a probable human carcinogen by EPA (EPA, 1996). Long-term, repeated exposure to formaldehyde may result in cancer of the nasal passages, mouth, lungs, or bone marrow (ATSDR 9, 1995).

2-3-22. Hexane

Hexane, CH₃(CH₂)₄CH₃, is a colorless, volatile liquid (Sittig, 1985; Keith, 1995). It is highly flammable (Sittig, 1985). It reacts with strong oxidizers and strong acids (Sittig, 1985; Keith, 1995). Selected chemical and physical properties of hexane are shown in Table 2-25.

Table 2-25. Selected chemical and physical properties of hexane

Hexane may enter the body through inhalation, ingestion, and skin and eye contact. Hexane may cause dermatitis and irritation of eyes, skin, and mucous membranes of the upper respiratory tract (Keith, 1995). It is also narcotic in high concentrations, causing nausea, headache, dizziness, vomiting, and unconsciousness (Sitting, 1985, Keith, 1995). Hexane may cause asphyxia resulting in brain damage or cardiac arrest (Keith, 1995). Chronic exposure to hexane may be related to the development of polyneuropathy (Sittig, 1985).

2-3-23. Isoprene (2-Methyl-1,3-butadiene)

Isoprene, CH₂C(CH₃)CHCH₂, is a colorless, volatile, flammable liquid (Verschueren, 1983; Clayton, 1994). It is highly reactive and undergoes explosive polymerization (Clayton, 1994). Selected chemical and physical properties of isoprene are shown in Table 2-26.

Table 2-26. Selected chemical and physical properties of isoprene

Isoprene may enter the body through inhalation, ingestion, and skin and eye contact. It is an irritant and, at high concentration, a central nervous system depressant and asphyxiant. Experiments show that 20% of inhaled isoprene may be absorbed in the upper respiratory tract and a total of 70-99% may remain in the lungs. It may cause irritation of mucous membranes of the upper respiratory tract, larynx, and pharynx and reduction of tracheal mucous flow (Clayton, 1994).

2-3-24. Methanol

Methanol, CH₃OH, is a colorless, volatile liquid with a sweet small (Sittig, 1985; Verschueren, 1983). It is flammable and can react with strong oxidizers, acids, reducing agents, and alkali metals (Sittig, 1985; Keith, 1995). Selected chemical and physical properties of methanol are shown in Table 2-27.

Table 2-27. Selected chemical and physical properties of methanol

Methanol may enter the body through inhalation, ingestion, and skin and eye contact. It is an irritant and narcotic (Keith, 1995). Skin contact with liquid may cause defatting and mild dermatitis. Exposure to methanol may cause optic nerve damage, blurring of vision, pain in eyes, loss of central vision, and blindness (Sittig, 1985). Other symptoms of exposure may include headache, nausea, giddiness, loss of consciousness, acidosis, circulatory collapse, and respiratory failure (Sittig, 1985, Keith, 1995).

2-3-25. Methyl Chloroform (1,1,1-Trichloroethane)

Methyl chloroform, C₆H₃Cl₃, is a colorless, nonflammable liquid with a chloroform-like odor (Sittig, 1985; Keith, 1995). It is hygroscopic. Methyl chloroform reacts with chemically active metals and can be oxidized by atmospheric oxygen at high temperatures. At high altitudes, it is reactive to sunlight (Keith, 1995). Selected chemical and physical properties of methyl chloroform are shown in Table 2-28.

Table 2-28. Selected chemical and physical properties of methyl chloroform

Methyl chloroform may enter the body through inhalation, ingestion, and skin and eye contact. It is an irritant. Acute exposure may cause mild conjunctivitis, but recovery is usually rapid. Repeated skin contact with it may cause defatting effects such as a dry, scaly, and fissure dermatitis. Methyl chloroform is also a narcotic (Sittig, 1985). Acute exposure may cause headache, dizziness, uncoordination, drowsiness, increase of reaction time, loss of consciousness, and death (Sittig, 1985, Keith, 1995). Due to a lack of human data and inadequate animal bioassays, methyl chloroform is not classified as to human carcinogenicity (EPA, 1996).

2-3-26. Methyl Ethyl Ketone (2-Butanone)

Methyl ethyl ketone (MEK), CH₃COCH₂CH₃, is a clear, colorless, flammable liquid with a fragrant, mint-like, moderately sharp odor (Sittig, 1985; Keith, 1995). It breaks down easily in air under sunlight but more slowly in water. It dissolves in water but does not adhere to soil (ATSDR 29, 1995). MEK reacts with very strong oxidizers (Sittig, 1985). Selected chemical and physical properties of MEK are shown in Table 2-29.

Table 2-29. Selected chemical and physical properties of methyl ethyl ketone

MEK may enter the body through inhalation, ingestion, and skin and eye contact. As an irritant, it causes irritation of eyes, nose, throat, and skin (Sittig, 1985; ATSDR 29, 1995). MEK may also be a narcotic at high concentrations, causing headache, dizziness, vomiting, incoordination, drowsiness, and increased reaction time (Sittig, 1985; Keith, 1995). Because of a lack of human data and inadequate animal bioassays, MEK is not classified as to human carcinogenicity (EPA, 1996).

2-3-27. Methyl Tert Butyl Ether

Methyl tert butyl ether (MTBE), C₅H₁₂O, is a flammable liquid. It is unstable in acid solution (Keith, 1995). MTBE is used as an octane booster in unleaded gasoline. Selected chemical and physical properties of MTBE are shown in Table 2-30.

Table 2-30. Selected chemical and physical properties of methyl tert butyl ether

It may enter the body through inhalation, ingestion, and skin and eye contact. Exposure to MTBE may cause nausea, vomiting, and sedation followed by depression of the central nervous system and respiratory system. Chronic inhalation of MTBE may result in tracheal and nasal inflammation (Keith, 1995).

2-3-28. Naphthalene

Naphthalene, C₁₀H₈, is a white crystalline solid with a characteristic tar or mothball odor (Sittig, 1985; Verschueren, 1983). It is also one of the sixteen PAHs. It evaporates easily from water and soil into air. In air, it is broken down by humidity and sunlight within a few hours. In water and soil, it remains only a few hours or days, either destroyed by bacteria or evaporating into the air (ATSDR 9018, 1990). Naphthalene reacts with strong oxidizers (Sittig, 1985). Selected chemical and physical properties of naphthalene are shown in Table 2-31.

Table 2-31. Selected chemical and physical properties of naphthalene

Naphthalene may enter the body through inhalation, ingestion, and skin and eye contact. Human exposure to naphthalene occurs mainly by breathing naphthalene-contaminated air. The primary health concern for naphthalene exposure is hemolytic anemia (a condition involving the breakdown of red blood cells) (ATSDR 9018, 1990). Naphthalene is an allergen and primary irritant. Repeated contact with naphthalene causes erythema and dermatitis, especially, in hypersensitive individuals (Sittig, 1985). Exposure to naphthalene may also cause other effects such as nausea, vomiting, diarrhea, kidney damage, jaundice (yellowish skin or eyes), and liver damage (ATSDR 9018, 1990). Because of a lack of human data and inadequate animal bioassays, naphthalene is not classified as to human carcinogenicity (EPA, 1996).

2-3-29. Perylene

Perylene, C₂₀H₁₂, exists as yellow to colorless crystals. It is a PAH but does not belong to the 16-PAH group. When heated to decomposition, it emits irritating fumes and acrid smoke. Perylene is a questionable carcinogen with inadequate evidence from animal studies (Windholz, 1983). Selected chemical and physical properties of perylene are shown in Table 2-32.

Table 2-32. Selected chemical and physical properties of perylene

2-3-30. Phenanthrene

Phenanthrene, C₁₅H₁₀, as an isomer of anthracene, is a crystalline solid (Clayton, 1994; Verschueren, 1983). It is also one of the sixteen PAHs. Selected chemical and physical properties of phenanthrene shown in Table 2-33.

Table 2-33. Selected chemical and physical properties of phenanthrene

Phenanthrene is a dermal photosensitizer and a mild allergen (Clayton, 1994). Because of a lack of human data and inadequate animal bioassays, phenanthrene is not classified as to human carcinogenicity (EPA, 1996). Please refer to Section 2-3-70 for more detail information of the PAH group.

2-3-31. Phenol

Phenol, C₆H₅OH, is a white crystalline solid with a strong, sickeningly sweet and irritating odor (Sittig, 1985; ATSDR 8920, 1989). It is combustible (Keith, 1995). Phenol dissolves well in water and evaporates more slowly than water. When phenol is released in small amounts, it does not stay long in the environment, usually half is removed from air in less than 1 day. Complete removal from soil takes 2-5 days, but it may remain in water for longer than 9 days. However, if a large amount is released or a steady amount is released over a long time, phenol can stay in the environment for a much longer period (ATSDR 8920, 1989). Selected chemical and physical properties of phenol are shown in Table 2-34. Phenol can react with strong oxidizers and calcium hypochlorite (Sittig, 1995).

Table 2-34. Selected chemical and physical properties of phenol

Phenol may enter the body through inhalation, ingestion, and skin and eye contact. It may cause death by all these routes. Phenol penetrates the skin rapidly (Keith, 1995). Most phenol that enters the body leaves in the urine within 24 hours (ATSDR 8920, 1989). Phenol is a severe irritant and is corrosive (Keith, 1995). Repeated exposure to low levels of phenol may result in diarrhea, mouth sores, lack of appetite, headache, dizziness, and mental disturbances (Sittig, 1985; ATSDR 8920,1989). Exposure to phenol may also cause severe eye damage, blindness, and severe skin burn. Other effects include shock, cyanosis, excitement, liver and kidney damage (Sittig, 1985). Phenol may have positive health effects when used for medical reasons such as used as an antiseptic to kill germs (ATSDR 8920, 1989).

2-3-32. Propionaldehyde

Propionaldehyde, CH₃CH₂CHO, is a colorless, flammable liquid with a sweet, ester, and irritating odor (Verschueren, 1983; Keith, 1995). It dissolves well in water and reacts with water. Propionaldehyde may also react with strong oxidizers and calcium hypochlorite (Keith, 1995). Selected chemical and physical properties of propionaldehyde are shown in Table 2-35.

Table 2-35. Selected chemical and physical properties of propionaldehyde

Propionaldehyde may enter the body through inhalation, ingestion, and skin and eye contact. Exposure to propionaldehyde may cause irritation of eyes, skin, mucous membranes, and the upper respiratory tract. Other effects include coughing, pulmonary edema, narcosis, nausea, vomiting, diarrhea, and respiratory failure (Keith, 1995).

2-3-33. Pyrene

Pyrene, C₁₆H₁₀, is a colorless solid. It chemical structure consists of four benzene rings joined together. It is insoluble in water but soluble in organic solvents. Pyrene is moderately toxic by ingestion. It is a skin irritant (Lewis, 1992). Because of data inadequacies, pyrene is not classified as to human carcinogenicity (EPA, 1996).

Pyrene is also one of the sixteen PAHs. Selected chemical and physical properties of pyrene are shown in Table 2-36. More information on the PAH group is presented in Section 2-3-70.

Table 2-36. Selected chemical and physical properties of pyrene

2-3-34. Styrene

Styrene, C₆H₅CH=CH₂, is a colorless or yellowish, very refractive, oily, flammable liquid with a sweet odor (ATSDR 53,1995; Keith, 1995). It evaporates easily, but does not dissolve easily in water. Styrene does not adhere to soil and travels through soil to groundwater. It is broken down quickly, within 1-2 days in air, a few days in surface water, but the breakdown takes much longer in groundwater, with a half-life of between 6 weeks and 7.5 months. Styrene is not expected to bioaccumulate in animals (ATSDR 53, 1995). Selected chemical and physical properties of styrene are shown in Table 2-37.

Table 2-37. Selected chemical and physical properties of styrene

Styrene can react violently with chlorosulfonic acid, oleum, sulfuric acid, and alkali metal graphite (Keith, 1995). It is incompatible with oxidizers (Sittig, 1985). Styrene may be polymerized when heated or exposed to light or a peroxide catalyst (Keith, 1995).

Styrene may enter the body through inhalation, ingestion, and skin and eye contact. It leaves the body quickly (ATSDR 53, 1995). Styrene may be an irritant and narcotic (Keith, 1995). Exposure to high levels of styrene may cause nervous system effects such as depression, loss of concentration, muscle weakness, tiredness, and nausea. It also causes irritation of eyes, nose, and throat (ATSDR 53, 1995). Acute exposure may lead to death due to respiratory center paralysis (Sittig, 1985). Animal studies show that exposure to styrene may cause damage to the liver, kidneys, brain, and lungs. Studies in animals also suggest that styrene is weakly carcinogenic (ATSDR 53, 1995). Human studies have showed that styrene is a neurotoxin. The human carcinogenicity of styrene is under review by the EPA (EPA, 1996).

2-3-35. Toluene

Toluene, C₆H₅CH₃, is a clear, colorless-to-amber, flammable liquid with a sweet pungent, benzene-like odor (Sittig, 1985; Keith, 1995). It evaporates quickly but does not remain in the environment for a long time. In air, toluene can combine with oxygen to form benzaldehyde and cresol. In soil, it is easily broken down by microorganisms (ATSDR 56, 1995). It reacts with strong oxidizers (Sittig, 1985). Although toluene can be taken up by fish, plants, and animals living in water, it does not build up to high levels in them (ATSDR 56, 1995). Selected chemical and physical properties of toluene are shown in Table 2-38.

Table 2-38. Selected chemical and physical properties of toluene

Toluene may enter the body through inhalation, ingestion, and skin and eye contact. Most toluene that is taken by the body leaves within 12 hours (ATSDR 56, 1995). Toluene may be toxic and irritating (Keith, 1995). Repeated or prolonged exposure through skin contact may remove natural lipids from skin and cause dry and fissured dermatitis (Sittig, 1985). The most important health concern is its harmful effects on the nervous system. Exposure to moderate levels of toluene for a short time may produce fatigue, confusion, general weakness, drunk-type actions, memory loss, nausea, and loss of appetite. Acute exposure to toluene may cause light-headedness and euphoria followed by dizziness, sleepiness, unconsciousness, and even death due to respiratory center paralysis (ATSDR 8923, 1989). Long-term exposure to toluene may cause permanent damage to brain with effects such as problems with speech, vision, and hearing; loss of muscle control; loss of memory and balance; and reduced scores on psychological test. The National Toxicology Program found that toluene did not cause cancer in workers and animals (ATSDR 8923, 1989). Because of a lack of human data and inadequate animal bioassays, EPA has not classified toluene as to human carcinogenicity (EPA, 1996).

2-3-36. 2,2,4-Trimethylpentane

2,2,4-Trimethylpentane, C₈H₁₈, is a clear, colorless, highly flammable liquid with gasoline-like odor. It is insoluble in water. 2,2,4-trimethylpentane reacts vigorously with reducing agents (Keith, 1995). 2,2,4-Trimethylpentane is a very dangerous fire hazard when exposed to heat, flame oxidizers (Lewis, 1992). Selected chemical and physical properties of 2,2,4-trimethylpentane are shown in Table 2-39.

Table 2-39. Selected chemical and physical properties of 2,2,4-trimethylpentane

Exposure to high concentrations of 2,2,4-trimethylpentane may cause narcosis (Keith, 1995).

2-3-37. Xylenes (Isomers and Mixture)

Xylene, C₆H₄(CH₃)₂, is a colorless, flammable liquid with a sweet odor (ATSDR 9030, 1990; Keith, 1995). It exists in three isomers: meta-xylene, ortho-xylene, and para-xylene (m-, o-, and p-xylene). Xylene easily dissolves fats, oils and waxes (Keith, 1995). Xylene evaporates quickly but does not mix well with water. In air, xylene can be broken down by sunlight within several days. However, in water, soil, and groundwater, xylene may remain for 6 months or longer before it is broken down (ATSDR 9030, 1990). Xylene can reacts with strong oxidizers (Sittig, 1985). Selected chemical and physical properties of xylene are shown in Table 2-40.

Table 2-40. Selected chemical and physical properties of xylene

Xylene may enter the body through inhalation, ingestion, and skin and eye contact. It is most likely to enter the body through inhalation of its vapors. After inhalation, 50% to 75% of xylene is rapidly absorbed by the lungs. Ingested xylene is absorbed rapidly and completely. Skin absorption of xylene is also quick. Once xylene enters the body, it passes into the blood and is broken down in the liver and kidneys. Most xylene leaves the body within 18 hours (ATSDR 9030, 1990).

Xylene may be toxic and irritating, and it can also be narcotic at high concentrations (Keith, 1995). Exposure to xylene may cause irritation of eyes, skin, nose, and throat; breathing difficulty; impaired lung function; delayed response to a visual stimulus; impaired memory; stomach discomfort; and possible changes in the liver and kidneys. Acute exposure may lead to death (ATSDR 9030, 1990). Other effects of exposure include headaches, lack of muscle coordination, dizziness, confusion, and unconsciousness (Keith, 1995, ATSDR 9030, 1990).

2-3-38. m-Xylene

m-Xylene, C₆H₄(CH₃)₂, is a colorless, flammable liquid with a sweet odor (ATSDR 9030, 1990; Keith, 1995). Selected chemical and physical properties of m-xylene are shown in Table 2-41. Please refer to Section 2-3-37 for more information.

Table 2-41. Selected chemical and physical properties of m-xylene

2-3-39. o-Xylene

o-Xylene, C₆H₄(CH₃)₂, is a colorless, flammable liquid with a sweet odor (ATSDR 9030, 1990; Keith, 1995). Selected chemical and physical properties of o-xylene are shown in Table 2-42. Please refer to Section 2-3-37 for more information.

Table 2-42. Selected chemical and physical properties of o-xylene