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

2-3-40. p-Xylene

p-Xylene, C₆H₄(CH₃)₂, is a colorless, flammable liquid with a sweet odor (ATSDR 9030, 1990; Keith, 1995). Selected chemical and physical properties of p-xylene are shown in Table 2-43. Please refer to Section 2-3-37 for more information.

Table 2-43. Selected chemical and physical properties of p-xylene

2-3-41. Aluminum and Compounds

Starting from this section, the discussions are on compound groups. As indicated previously, each group many include hundreds of chemicals. Since the information of mobile source emissions is not sufficient to determine the molecular makeup of the metal, ammonia, cyanide, nitrogen, and sulfur- containing compounds, the general information is provided for each group and the representative chemicals. The representative members of these groups are selected from Table 2-1, chemicals of concern. For metal compounds, discussions are also had on metal elements. For groups, such as PAH and POM, the available definitions are used.

Aluminum, Al, is a light, silver-white, soft, ductile, malleable amphoteric metal. It is flammable as a powder. Aluminum dissolves in acids or alkali but is insoluble in water (Sittig, 1985). When released, aluminum and compounds bind to particles in the air, therefore, inhalation of dust or fume is the main route for them to enter the body (Sittig, 1985, ATSDR 22, 1995). Aluminum and compounds may also enter the human body through ingestion and skin and eye contact (ATSDR 22, 1995).

Low-level exposure to aluminum may not be harmful to human health, however, high-level exposure to aluminum may result in respiratory problems such as coughing and asthma (ATSDR 22, 1995). When deposited in eyes, aluminum may cause necrosis of the cornea. Exposure to aluminum compounds may cause dermatoses, eczema, conjunctivitis, and irritation of mucous membranes of the upper respiratory system (Sittig, 1985). High levels of aluminum built up in the brain may be linked to Alzheimer’s disease. Human studies suggest that aluminum may cause skeletal problems (ATSDR 22, 1995).

2-3-42. Ammonia and Compounds

Discussions in this section focus on ammonia and several selected compounds. The selection of compounds is intended to give examples of ammonium compounds. It is not a comprehensive list.

2-3-42-1. General

Ammonia, NH₃, is a colorless, strong alkaline gas with a very sharp odor (Sittig, 1985; ATSDR 9003, 1990). It is extremely soluble (Sittig, 1985). In water, most of ammonia may exist in an ammonia-ammonium equilibrium (ATSDR 9003, 1990). It is incompatible with strong oxidizers, calcium, hypochlorite bleaches, gold, mercury, silver, and halogens (Sittig, 1985). Ammonia persists a few days in soil and about one week in air (ATSDR 9003, 1990).

Ammonia may enter the body through inhalation, ingestion, and skin and eye contact. Most inhaled ammonia is breathed out again, but ingested ammonia is readily absorbed and carried throughout the body within minutes. After entering the body, ammonia changes rapidly to other harmless substances. A small amount of ammonia may persist in the body prior to excretion in urine within a couple of days (ATSDR 9003, 1990).

Exposure to high levels of ammonia may cause coughing and irritation of the eyes, skin, throat, and lungs. The irritation may be serious enough to result in permanent blindness, lung disease, or death (ATSDR 9003, 1990).

2-3-42-2. Examples

Ammonium chloride, NH₄Cl, is a white crystalline solid. It may enter the body through inhalation, ingestion, and skin and eye contact. Ammonium chloride is a mild irritant and has relatively low toxic potency. It may cause irritation of skin and the respiratory system (Sittig, 1985).

Ammonium sulfamate, NH₂SO₃NH₄, is a colorless and odorless solid. It reacts with strong oxidizers and is incompatible with hot water. It may enter the body through inhalation, ingestion, and skin and eye contact. It is moderately toxic potency and may cause gastrointestinal disease (Sittig, 1985).

2-3-43. Antimony and Compounds

Discussions in this section focus on antimony and several selected compounds. The selection of compounds is intended to give examples of antimony compounds. It is not a comprehensive list.

2-3-43-1. General

Antimony, Sb, is a silvery-white, soft metal (Sittig, 1985; ATSDR 23, 1995). It is insoluble in water and organic solvents. Antimony reacts with oxidizers, acids and halogenated acids (Sittig, 1985). In air, it is attached to small particles and may be suspended in air for a long time. Antimony also attaches strongly to particles in soil (ATSDR 23, 1995).

Antimony may enter the body through inhalation, ingestion, and skin and eye contact. (ATSDR 9003, 1990). It is an irritant and has relatively high toxic potency (Keith, 1995). Long-term inhalation of high levels of antimony may cause irritation of eyes and lungs, problems in lungs and heart, stomach pain, diarrhea, vomiting, and stomach ulcers. Animal studies show that short-term inhalation of very high levels of antimony may lead to lung, heart, liver, and kidney damage and death. Breathing very low levels of antimony may cause eye irritation, hair loss, lung damage, and heart problems in animals. Ingestion of a large amount of antimony may cause vomiting (ATSDR 23, 1995).

2-3-43-2. Examples

Antinomy oxide, Sb₂O₃, is a white crystalline powder. It is not easily soluble in water. Antinomy oxide may be toxic and an irritant. Exposure to antimony oxide may cause skin irritation and eczema, mucous membrane inflammation, sleeplessness, fatigue, dizziness, irritability, metallic taste, stomatitis, vomiting, diarrhea, and muscle and neuralgic pains (Keith, 1995).

Antimony potassium tartrate, C₄H₄KO₇Sb, is a colorless crystal or white granular powder. It can react with tannic acid, alkalis and their carbonates, lead salts, acids, and strong oxidizers. Antimony potassium tartrate is an irritant and may be toxic through ingestion. Exposure to antimony potassium tartrate may cause cough, metallic taste, salivation, nausea, diarrhea, skin rash, eye and respiratory tract irritation, headache, dizziness, dyspnea, anaphytoxis, hypotension and weakness. High-level exposure may result in liver damage (Keith, 1995).

2-3-44. Arsenic and Compounds (Inorganic Including Arsine)

Arsenic is usually combined with one or more other elements. When arsenic is combined with oxygen, chlorine, and sulfur, it is referred to as inorganic arsenic. Discussions in this section focus on arsenic and several selected compounds. The selection of compounds is intended to give examples of arsenic compounds, not to comprise a comprehensive list.

2-3-44-1. General

Arsenic, As, is a gray-colored metal. Pure arsenic does not exist commonly in the environment (ATSDR 8802, 1989). It is flammable by chemical reaction with powerful oxidizers. Arsenic materials may react with any reducing agent (Keith, 1995).

Arsenic may enter the body through inhalation, ingestion, and skin contact (Sittig, 1985; ATSDR 8802, 1989). However, the principal route of entry is ingestion. Skin contact is usually unimportant. Once ingested or inhaled, most arsenic is quickly absorbed through the gastrointestinal tract or lungs and enters the bloodstream. Arsenic in blood is converted by the liver to a less-toxic form excreted efficiently in the urine. Arsenic does not tend to accumulate in the body except at high exposure levels (ATSDR 8802, 1989).

Exposure to inorganic arsenic may cause irritation of the gastrointestinal tract, resulting in pain, nausea, vomiting, and diarrhea. The exposure may also cause decreased production of red and white blood cells; abnormal heart function; damage of blood vessels, liver, and kidneys; and impaired nerve function. The most characteristic effect of oral exposure is skin abnormalities such as dark and light spots on the skin, and small "corns" on the palms, soles, and trunk. These skin changes may lead to skin cancer. Arsenic exposure may also lead to increased risk of cancer in liver, bladder, kidneys, and lungs. Exposure to arsenic compounds through direct dermal contact may result in mild to severe irritation of the skin, eyes, or throat (ATSDR 8802, 1989).

2-3-44-2. Examples

Arsenic trioxide, As₂O₃, occurs as white or transparent, amorphous lumps or crystals, having a glassy appearance. It reacts with oxidizing agents, causing irritation of gastrointestinal tract with nausea, vomiting and diarrhea. The vomitus and stools may be bloody. In severe cases, exposure to arsenic trioxide may result in collapse and shock; constipation; liver damage; disturbance of blood, kidneys, and nervous system; skin abnormalities; constriction of the throat; or difficulty in swallowing (Keith, 1995).

Arsine, AsH₃, is a colorless, flammable gas (Keith, 1995). It reacts with strong oxidizers, chlorine, and nitric acid. Arsine has extremely high toxic potency and may be fatal if sufficient quantities are inhaled. Acute exposure causes massive intravascular hemolysis of the circulating red cells. Early effects include general malaise, apprehension, giddiness, headache, shivering, thirst, and abnormal pain with vomiting. In severe acute poisoning, it causes bloody vomiting followed by diarrhea and pulmonary edema. Low-level and prolonged exposure may be associated with general tiredness, pallor, breathlessness on exertion, and palpitations. Damage of the eyes may occur with high-level exposure (Sittig, 1985).

2-3-45. Barium and Compounds

Barium, Ba, is a silver-white metal (ATSDR 24, 1995). It may ignite spontaneously. Although barium is insoluble in water, most of the barium compounds are soluble in water (Sittig, 1985). Therefore, some barium compounds may be found in lakes, rivers, and streams. Fish and aquatic organisms are expected to accumulate barium (ATSDR 1995). Some barium compounds are reactive, such as its peroxide, nitrate, and chlorate (Sittig, 1985).

Barium and compounds can enter the body through ingestion, inhalation of dust or fumes, or skin and eye contact. The health effects of barium compounds depend on their solubility in water. The soluble, ionized barium compounds may cause harmful effects on people such as markedly increasing contractility of all muscles, including the heart muscle (Sittig, 1985). Other effects include difficulties in breathing, increased blood pressure, stomach irritation, brain swelling, damage to liver, kidneys, heart, and spleen (ATSDR 24, 1995). Exposure to hydroxide, carbonate, and other alkaline barium compounds may cause irritation to eyes, nose, throat, and skin (Sittig, 1985). Barium has not been classified as to its human carcinogenicity (ATSDR 24, 1995).

2-3-46. Bromine and Compounds

Discussions in this section focus on bromine and several selected compounds. The selection of compounds is intended to give examples of bromine compounds, not to comprise a comprehensive list.

2-3-46-1. General

Bromine, Br₂, is a dark reddish-brown, volatile, diatomic liquid with a suffocating odor. It vaporizes rapidly at room temperature and dissolves completely in water at 25^oC. It is a halogen but less reactive than chlorine. Bromine may react with alkali hydroxides; arsenites; ferrous, mercurous salts; hypophosphites; and other oxidizable substances (Widholz, 1983).

Bromine may enter the body through inhalation, ingestion, and skin and eye contact. As an irritant, it may cause dermal corrosion and serious irritation of the respiratory tract. Exposure to bromine via ingestion may result in severe gastroenteritis and death (Widholz, 1983).

2-3-46-2. Examples

Bromoform, CHBr₃, is a colorless, heavy liquid. It does not dissolve easily in water and can react with chemically active metals. Bromoform may be irritating and narcotic, it is also a lachrymator. Exposure to bromoform may cause irritation of eyes, skin, and the respiratory tract; respiratory difficulties; tremors; and unconsciousness. Ingestion and inhalation of bromoform may lead to death. Other health effects may include liver and kidney damage, central nervous system depression, dizziness, disorientation, and slurred speech (Keith, 1995).

Bromobenzene, C₆H₅Br, is a clear liquid with an aromatic odor (Clayton, 1994; Widholz, 1983). It is an irritant and causes irritation of eyes, skin, and the respiratory tract. Exposure to bromoform may cause damage to liver, kidneys, and lungs (Clayton, 1994).

2-3-47. Cadmium and Compounds

Discussions in this section focus on cadmium and several selected compounds. The selection of compounds is intended to give examples of cadmium compounds, not to comprise a comprehensive list.

2-3-47-1. General

Cadmium, Cd, is a soft silver-white, blue tinged and lustrous metal (Keith, 1995; ATSDR 8808, 1989). It is insoluble in water (Keith, 1995). Pure cadmium is not common in the environment, rather, it combines with other elements such as oxygen, chlorine, and sulfur to form cadmium compounds. These compounds are all stable solids and do not evaporate (ATSDR 8808, 1989).

Cadmium can enter the body by inhalation and ingestion of fumes and dust (Sittig, 1985). Only very little cadmium may enter the body via skin contact. About 1-5% of ingested cadmium and about 30-50% of inhaled cadmium is taken up into the blood and is retained very strongly in the body. Therefore, even low-dose exposure may lead to significant cadmium levels in the body if the exposure is prolonged enough (ATSDR 8808, 1989).

Cadmium and compounds may be highly toxic, and certain cadmium compounds may be carcinogens. Ingestion of cadmium and solvated compounds may cause irritation to the stomach leading to salivation, choking, vomiting, abdominal pain, anemia, renal dysfunction, diarrhea and tenesmus (ATSDR 8808; 1989; Keith, 1995). Exposure via inhalation may cause throat dryness, cough, headache, vomiting, chest pain, extreme restlessness and irritability, pneumonitis, and possibly bronchpneumonia (Keith, 1995). Other effects associated with exposure include kidney damage; lung damage; high blood pressure; and injuries to the liver, immune system, and the nervous system. Long-term inhalation of cadmium can lead to increase risk of lung cancer (ATSDR 8808, 1989).

2-3-47-2. Examples

Cadmium chloride, CdCl₂, exists as colorless or white hexagonal crystals. It reacts violently with bromine trifluoride and potassium. It also reacts with oxidizers, acids, elemental sulfur, selenium, and tellurium. Cadmium chloride is an irritant and highly toxic. Exposure to cadmium chloride may cause tightness in chest; emesis; tubular dysfunction and necrosis of kidneys and liver; irritation of skin, eyes, the gastrointestinal tract, and the respiratory tract (Keith, 1995).

Cadmium oxide, CdO, is red-brown or colorless crystals. It reacts violently with magnesium. Cadmium oxide is an irritant. Harmful effects of exposure to cadmium oxide include nausea, vomiting, diarrhea, head and muscle aches, salivation, abdominal pain, shortness of breath, chest pain, cough with foamy or bloody sputum, and weakness. Cadmium oxide may also cause severe to fatal lung irritation, elevated blood pressure, kidney and liver injuries (Keith, 1995).

2-3-48. Calcium and Compounds

Discussions in this section focus on calcium and several selected compounds. The selection of compounds is intended to give examples of calcium compounds, not to comprise a comprehensive list.

2-3-48-1. General

Calcium, Ca, is a silver-white, lustrous metal. It ignites in air when finely divided, then burns with crimson flame. Calcium reacts with water, alcohols, and halogens (Widholz, 1983). In general, calcium compounds are toxic only when they contain toxic components, such as arsenic, or as calcium oxide or hydroxide (Lewis, 1992).

2-3-48-2. Examples

Calcium arsenate, Ca₃(AsO₄)₂, is a white flocculent powder. It can enter the body through inhalation, ingestion, and skin and eye contact. Exposure to calcium arsenate may cause weakness, gastrointestinal distress, peripheral neuropathy, hyperpigmentation, palmar-plantar hyperkeratoses, or dermatitis. As a carcinogen, it may cause skin cancer, and cancer of the lungs, larynx and lymph (Sittig, 1985).

Calcium carbide, CaC₂, is a grayish-black, flammable solid. It is incompatible with water. The main routes of entry to the body for calcium carbide are inhalation and ingestion. Exposure to calcium carbide may cause irritation of skin, eyes, and the respiratory tract; and lung edema (Sittig, 1985).

Calcium cyanamide, CaCN₂, is a blackish-grey, shiny, flammable powder. It enters the body through inhalation, ingestion, and skin and eye contact. Calcium cyanamide is a primary irritant, causing irritation to skin, eyes, and mucous membranes of the respiratory tract. Exposure to calcium cyanamide may cause a characteristic vasomotor reaction, including erythema of the upper portion of the body, face and arms accompanied by nausea, fatigue, headache, dyspnea, vomiting, oppression in the chest and shivering. In severe cases, circulatory collapse may occur, pneumonia or lung edema may develop (Sittig, 1985). Calcium cyanamide may be a carcinogen (Lewis, 1992).

Calcium hydroxide, Ca(OH)₂, is a soft white crystalline powder. It is a moderately caustic irritant, causing irritation to all exposed body surfaces (Sittig, 1985). Calcium hydroxide is mildly toxic by ingestion (Lewis, 1992).

Calcium oxide, CaO, is white or grayish-white lumps or powders. It reacts with water exothermically. Because of this reaction and the alkalinity of calcium oxide, it may irritate skin, conjunctiva, the cornea, as well as mucous membranes of the upper respiratory tract. Inhalation of calcium oxide may also result in bronchitis and pneumonia (Sittig, 1985).

2-3-49. Chromium and Compounds

Discussions in this section focus on general information of chromium and compounds. Chromic acid is selected to give an example of chromium compounds, not to comprise a comprehensive list.

2-3-49-1. General

Chromium may exist in the environment in one of three major states: chromium metal, chromium (III), and chromium (VI) (ATSDR 8810, 1989). There is no odor or taste associated with chromium compounds (ATSDR 7, 1993). Chromium metal, Cr, is a very hard, steel-gray solid (Keith, 1995; ATSDR 8810, 1989). It can react violently with ammonium nitrate, nitrogen dioxide, nitrogen oxide, lithium, potassium chlorate, and sulfur dioxide (Keith, 1995). Chromium (III) and chromium (VI) are in the trivalent form and hexavalent form, respectively. Chromium (III) compounds are stable and a very small amount of chromium (III) is an essential nutrient. A daily ingestion of 50-200 mg per day has been estimated to safe and adequate (ATSDR 7, 1993).

Chromium binds strongly with soil, and only small amounts move to groundwater. In water, it adheres to dirt particles. Chromium is not expected to bioaccumulate (ATSDR 7, 1993).

Chromium may enter the body through inhalation, ingestion, and skin and eye contact. The major health concern is for chromium (VI). Chromium (VI) is an irritant. Acute exposure to chromium (VI) may cause ulcers of skin, irritation of nasal mucosa and perforation of the nasal septum, and irritation of the gastrointestinal tract. It may also lead to adverse effects in kidneys and liver (ATSDR 8810, 1989). Chromium (VI) is a human carcinogen (EPA, 1996). Long-term exposure to chromium (VI) has been associated with lung cancer. Chromium (III) compounds are of a low order of toxicity. Exposure to chromium metal is less common and health effects of the exposure have not been well characterized (ATSDR 8810, 1989).

2-3-49-2. Example

Chromic acid, CrO₃, is dark, red crystals, flakes or powders. It is combustible and very soluble in water. It is also a powerful oxidizer. Chromic acid reacts violently with most organic substances in a possibly explosive manner (Keith, 1995). It also reacts with other readily oxidizable materials such as paper, wood, sulfur, aluminum, and plastics (Sittig, 1985). Chromic acid is a severe irritant and is toxic and carcinogenic. Exposure to chromic acid may cause dermal irritation, ulceration, and allergic eczema; nasal irritation and septal perforation; pulmonary irritation; bronchogenic carcinoma; and violent gastrointestinal irritation (Keith, 1995).

2-3-50. Cobalt and Compounds

Cobalt, Co, is a silver-gray, hard, brittle, shiny, and magnetic metal (Sittig, 1985; ATSDR 33, 1995). Cobalt metal is insoluble in water, but some of its compounds dissolve in water. Cobalt stays in air only for a few days but may remain in water and soil for years. Plants can take up cobalt from the soil (ATSDR 33, 1995).

Cobalt may enter the body through inhalation, ingestion, and skin and eye contact. It has both harmful and beneficial effects on human health. Cobalt is part of Vitamin B₁₂, an essential nutrient. However, exposure to high levels of cobalt may cause asthma, pneumonia, and wheezing (ATSDR 33, 1995). Cobalt is also a mild irritant and allergen, and it causes irritation to eyes and skin and allergic sensitivity type dermatitis (Sittig, 1985). It has been designated as a possible human carcinogen by the International Agency for Research on Cancer (ATSDR 33, 1995).

2-3-51. Copper and Compounds

Copper, Cu, is a reddish-brown, ductile metal. It does not dissolve in water, but is soluble in nitric acid and hot sulfuric acid. Copper can form both mono-and divalent compounds (Sittig, 1985). Most copper compounds in the environment are strongly attached to dust and dirt. Some copper compounds bind to particles less tightly and may be taken up by animals and plants (ATSDR 9008, 1990).

Copper and compounds can enter the body through inhalation of dust or fumes, ingestion, and skin and eye contact. Once copper enters the body through ingestion, it rapidly goes to the bloodstream and is distributed throughout the body. Ingestion of high levels of copper may cause vomiting and diarrhea, which helps copper from entering the bloodstream. Copper that enters the body may stay in there for several day then leave the body in feces and urine (ATSDR 9008, 1990).

Copper salts are irritants to skin and eyes, causing itching, erythema; dermatitis, conjunctivitis, and ulceration and turbidity of the cornea. Skin contact with metallic copper may cause keratinization of the hands and soles of the feet. Inhalation of copper fumes and dust may result in irritation of the upper respiratory tract, metallic taste, nausea, and metal fever (Sittig, 1985). Ingestion of copper salts may also produce irritation in the gastrointestinal tract, causing salivation, nausea, vomiting, gastric pain, stomach cramps, and diarrhea (Sittig, 1985; ATSDR 9008, 1990). Long-term and high-level exposure to copper may cause liver damage and death, particularly in very young children (ATSDR 9008, 1990).

2-3-52. Cyanide Compounds

As defined in the Clean Air Act Amendments (1990), cyanide compounds are "X’CN where X = H’ or any other group where a formal dissociation may occur. For example KCN or Ca(CN)₂." People are most likely to have contact with compounds such as hydrogen cyanide, sodium cyanide, and potassium cyanide (ATSDR 8812, 1989).

Hydrogen cyanide, HCN, is a colorless or pale blue liquid or gas with a strong, irritating, bitter almonds odor. Its boiling point is 26^oC. It is miscible and soluble in water. When it is exposed to heat, flame or oxidizers, a very dangerous fire hazard can occur (Keith, 1995). Potassium cyanide, KCN, is a white granular powder. Sodium cyanide, NaCN, is a nonflammable, white crystalline powder (Keith, 1995). Both potassium cyanide and sodium cyanide have a slight, bitter almond odor (ATSDR, 8, 1993).

In water and soil, cyanide compounds generally form hydrogen cyanide that goes into the air and remains there for several years. Cyanide compounds are not accumulated in fish.

Cyanide compounds can enter the human body through inhalation, ingestion, and skin and eye contact. Very small amounts of cyanide, in the form of vitamin B₁₂, are needed by human to prevent iron poor blood, or anemia. The harmful effects of cyanide compounds are due to their ability to affect tissues’ oxygen use (ATSDR 8, 1993). High-level exposure to cyanide for a short time may cause damage to the central nervous system, respiratory system, and cardiovascular system, resulting in coma and death. Exposure to lower levels of cyanide for a short time may also result in rapid, deep breathing, shortness of breath, convulsions, and loss of consciousness (ATSDR 8812, 1989). Other symptoms associated with lower-level exposure include pain in the heart area, vomiting, blood changes, headaches, and enlarged thyroid glands (ATSDR, 8, 1989). Long-term exposure to cyanide may lead to damage of the central nervous system, causing deafness, vision problems, and loss of coordination. Effects on the thyroid gland result in retarded physical and mental growth in children, and enlargement and overactivity of the gland (ATSDR 8812, 1989).

2-3-53. Iron and Compounds

Iron, Fe, is a malleable, silver-gray metal. It is insoluble in water. Iron is potentially toxic. Inhalation of iron dust is the main route of entry of iron to the human body (Sittig, 1985). High-level inhalation of iron dust may cause iron pneumoconiosis. Long-term exposure to excess levels of iron may lead to pathological deposition of iron in the body tissues, causing fibrosis of the pancreas, diabetes mellitus, and liver cirrhosis (Lewis, 1992).

The toxicity of iron compounds varies with the element with which the iron is combined. Soluble iron compounds, especially ferric chloride (FeCl₃) and ferric sulfate (Fe₂(SO₄)₃), are dermal irritants, causing irritation to eye, skin, and the respiratory tract (Sittig, 1985; Lewis, 1992). Ferric chloride is also moderately toxic by ingestion and may cause reproductive effects.

In general, ferrous compounds are more toxic than ferric compounds. Short-term exposure to high levels of ferrous compounds may cause liver and kidney damage, altered respiratory rates, and convulsions. As one example of ferrous compounds, ferrous sulfate, FeSO₄, dissolves in water slowly. It is a human poison by ingestion. The health effects associated with ingestion of ferrous sulfate include aggression, somnolence, diarrhea, nausea or vomiting, bleeding from the stomach, and coma (Lewis, 1992).

2-3-54. Lead and Lead Compounds

Discussions in this section focus on lead and several selected compounds. The selection of compounds is intended to give examples of lead compounds, not to comprise a comprehensive list.

2-3-54-1. General

Lead, Pb, is a soft, silver-bluish white metal. In air, lead attaches to particulates and can be transferred long distances. It is insoluble in water and can stay in soil for many years. The main routes of entry to the human body for lead are inhalation and ingestion. Not much lead passes through skin to the body via contact with lead-containing dust and dirt . Almost all of the inhaled lead enter the bloodstream and is transported throughout the body. In contrast, only very small amounts of ingested lead enters the bloodstream from the gastrointestinal tract in adults. However, in children, much more ingested lead enters the blood and moves to other parts of the body. Most of the lead that enters the body is stored in bone and teeth (ATSDR 8817, 1990).

Exposure to lead is especially dangerous for pregnant women, because lead can be carried to the fetuses, causing premature birth, low birth weight, abortion, and other harmful effects on the unborn children. For infants and young children, exposure to lead may cause decreased intelligence (IQ) scores, slow growth, and hearing problems. Moreover, these effects may be irreversible or may last a long time.

High-level exposure may result in severe damage to brain and kidneys. Lead exposure may also cause damage to the male reproductive system and increased blood pressure in middle-aged men (ATSDR 8817, 1990).

Lead compounds can enter the body through inhalation, ingestion, and skin and eye contact. Skin and eye contact is specially important for organic compounds of lead but not for inorganic compounds of lead. The toxicity of lead compounds depends on their solubility in the body fluids and the particle size distribution during exposure. Organolead compounds usually are rapidly absorbed via all routes (Lewis, 1992). Lead and its inorganic compounds are probable human carcinogens (EPA, 1996).

The burning of leaded gasoline was the most significant source of lead emissions to air. Less lead comes from gasoline now because of the results of federal regulatory actions. Since January 1, 1996, leaded gasoline has been prohibited for use in highway vehicles by the mandate of the 1990 Clean Air Act Amendments. Lead emissions from mobile sources are expected to be further decreased as a result of this ban on leaded gasoline.

2-3-54-2. Examples

Lead sulfate, PbSO₄, is a white crystalline solid and, along with lead carbonate and lead monoxide, is a considered to be more toxic than metallic lead or other lead compounds. It is moderately toxic by ingestion. Lead sulfate is also a corrosive irritant to skin, eyes, and mucous membranes (Lewis, 1992).

Lead acetate, PbC₄H₆O₄, exists as colorless or white crystals. It may have high toxic potency. The human body may absorb lead acetate at about 1.5 times the rate of other lead compounds. Exposure to lead acetate may cause fatigue, disturbance of sleep, and constipation. In more severe cases, it may cause abdominal pain, nausea, headache, loss of appetite, metallic taste, muscle and joint pain, dizziness, and hypertension. Long-term overexposure may result in severe damage to blood cell formation, the central nervous system, the peripheral nervous system, kidneys, and liver. Death may result from high levels of lead acetate in the blood. It may also damage fetuses and impair male and female reproductive systems. (Keith, 1995). Lead acetate may be a carcinogen (ATSDR 8817, 1990).

Lead arsenate, PbAsHO₄, exists as white crystals. It is very toxic because of the presence of the arsenic ion. It has been confirmed as a human carcinogen (Lewis, 1992).

2-3-55. Manganese and Compounds

Manganese, Mn, is a reddish-gray or silvery, brittle metal. It is insoluble in water. Manganese is flammable and moderately explosive in the form of dust or powder when exposed to flame. Exposure to manganese by inhalation may cause degenerative brain changes, changes in motor activity, and muscle weakness. It is also a skin and eye irritant. While certain experimental data have suggested that manganese is carcinogenic, studies to-date are inadequate to fully assess its carcinogenicity (Keith, 1995).

Manganese and compounds may enter the human body mainly through inhalation of fumes and dust. Exposure to manganese compounds may cause damage to the central nervous system and pulmonary system. Chronic exposure may begin with complaints of languor and sleepiness, followed by weakness in legs and development of solid, mask-like faces. Then muscular twitching occurs, and nocturnal leg cramps may appear. There is also a slight increase in tendon reflexes, ankle and patellar clonus, and a typical Parkinsonian slapping gait. In severe cases, permanent disability may result (Lewis, 1992).

2-3-56. Mercury and Compounds

Mercury exists in the environment in three forms: metallic mercury, inorganic, and organic mercury compounds. In the environment, mercury has a long residence time and can change between organic and inorganic forms. Some or all organic mercury will be slowly broken down to inorganic mercury. Some inorganic mercury will be also changed slowly to organic mercury in water and soil (ATSDR 8916, 1990).

Metallic mercury, Hg, is a silver-white, heavy, odorless, mobile liquid. It is noncombustible. Metallic mercury is a virulent poison. It can enter the human body through inhalation, ingestion, and skin and eye contact, and it is readily absorbed by the body via all these routes (Keith, 1995). Because metallic mercury has high vapor pressure at ambient temperatures, 0.002 mm Hg at 25^oC (Lewis, 1992), dangerous levels of mercury are easily accumulated in air. Metallic mercury is corrosive to skin, eyes, and mucous membranes. Exposure to mercury by inhalation may cause wakefulness, muscle weakness, anorexia, headache, tinnitus, hypermotility, diarrhea, liver changes, dermatitis, and fever. The most consistent and pronounced effects of chronic exposure to mercury vapor are on the central nervous system. Experiments also show metallic mercury may cause reproductive effects and mutagenic effects (Keith, 1995).

Inorganic mercury compounds are the combinations of metallic mercury with other inorganic chemicals, such as chlorine, sulfur, or oxygen. Most inorganic mercury compounds are white powders or crystals. A number of inorganic mercury compounds are explosively unstable or undergo hazardous reactions. In this form, mercury still can enter the human body through inhalation, ingestion, and skin and eye contact, and is readily absorbed by the body via all these routes. Once absorbed by the body, it circulates in the blood and then is stored in the liver, kidneys, spleen, and bone. The principal effect is on the central nervous system, mouth, and gums. The cardinal symptoms include stomatitis, tremors, and psychic disturbances. Exposure to inorganic mercury compounds in the early stage may cause excessive salivation and painful chewing. In severe cases, it may result in gingivitis with loosening of the teeth, and a dark line on the gum margins. Psychic disturbances include loss of memory, insomnia, lack of confidence, irritability, vague fears and depression. Some mercury compounds can cause skin irritation, and are strong allergens. Generally, soluble salts have violent corrosive effects on skin and mucous membranes, causing severe nausea, vomiting, abdominal pain, bloody diarrhea, kidney damage, and death usually within 10 days (Lewis, 1992).

The organic mercurials include a number of compounds which are explosively unstable or undergo hazardous reactions. Organic mercury compounds seem to have an affinity for lipoid-containing organs, causing central nervous system disturbances. However, their toxicity varies with the organic moiety. For example, alkyl mercurials have very high toxicity, but aryl compounds, particularly the phenyls, are much less toxic. Both alkyls and aryls commonly cause skin irritation and can be absorbed through the skin. Exposure to alkyl mercurials may cause permanent damage to the brain or death. Phenyl mercurials appear to be no more toxic than metallic mercury. Maternal exposure to organic mercury may result in brain damage in fetuses (Lewis, 1992).

Methylmercury, , is produced (methylated) mainly by small organisms in water and soil. The level of methylmercury increases with the amount of mercury in the environment (ATSDR 46, 1995). It can build up in certain fish. Therefore, low levels of mercury in the ocean and lakes can contaminate these fish. Eating fish or shellfish contaminated with methylmercury may result in high-level exposure to mercury (ATSDR 8916, 1990). Besides the adverse health effects described above, methylmercury has been classified as a possible human carcinogen (EPA, 1996).

2-3-57. Nickel and Compounds

Nickel, Ni, is a hard, silver, nonflammable metal. However, its dust or powder is combustible and can form explosive mixtures in air. Nickel is insoluble in water. It also combines with other chemicals such as chlorine, sulfur, and oxygen to form nickel compounds, which are tasteless and odorless. Many of them can dissolve easily in water and the solutions have a characteristic green color (ATSDR 15, 1993).

When released to air, nickel attaches to small dust particles and stays in the air for months. This nickel dust may settle to the ground or be washed from air by rain and snow then attach to soil or sediment particles. Nickel will not build up in fish but may accumulate in plants and land animals (ATSDR, 15, 1993).

Nickel can enter the human body through inhalation, ingestion, and skin contact. Very small amounts of nickel may be essential to humans, however, high-level exposure to nickel can harm human health. The most common adverse effects of exposure to nickel and compounds are skin allergies. The allergic responses include skin rashes and asthma. Inhalation of high levels of nickel may link to higher death rates from lung diseases. Long-term exposure to nickel may cause cancer of the lung and nasal sinus. Effects on heart, blood, and kidneys are also observed (ATSDR 8819, 1988; ATSDR 15, 1993). Ingestion of soluble nickel compounds may cause nausea, vomiting, diarrhea, intestinal disorders, convulsions, and asphyxia (Lewis, 1992). Animal studies show that exposure to high-levels of certain nickel compounds during pregnancy may cause miscarriages, pregnancy complications, and low birth weight in newborns (ATSDR 8819, 1988). Nickel and certain nickel compounds may be carcinogens (ATSDR 8819, 1988; ATSDR 15, 1993). For example, nickel subsulfide is confirmed to cause lung and nasal cancers in humans, and nickel carbonyl is a probable human carcinogen and may cause lung cancer (EPA, 1996).

2-3-58. Nitrogen Compounds

The chemicals described below are intended as selected examples of nitrogen compounds and do not comprise a comprehensive list.

2-3-58-1. Nitrates

Organic nitrates, nitro compounds, are a combination of the nitro (-NO₂) group and an organic radical. Inorganic nitrates are a combination of metal and the mono-valent NO₃ radical. Nitrates are flammable by spontaneous chemical reaction. Practically, all of them are powerful oxidizers which may cause violent reaction with reducing materials. Some nitrates may explode when shocked, exposed to heat or flame, or by spontaneous chemical reaction. Under certain conditions, all the inorganic nitrates can give up their oxygen to other materials that may in turn detonate. Ammonium nitrate, especially, is able to detonate by itself under proper conditions.

Ingestion of large amounts of nitrates may lead to serious or even fatal effects. The symptoms include dizziness, abdominal cramps, vomiting, bloody diarrhea, weakness, convulsions, and collapse. Prolonged exposure to small amounts of nitrates may cause weakness, general depression, headache and mental impairment. Some evidence shows increased cancer incidence associated with exposure to nitrates (Lewis, 1992).

2-3-58-1-1. Nitrobenzene

Nitrobenzene, C₆H₅NO₂, is a colorless or pale yellow to brown, oily liquid with a odor of bitter almond oil. Its melting point is 5.7^oC. It dissolves slightly in water, but is very soluble in oils, ether, and benzene. Nitrobenzene is combustible and reacts with reducing agents (Keith, 1993).

Nitrobenzene is an eye and skin irritant. It can be rapidly absorbed through skin and cause irritation on contact. It can also enter the human body through inhalation and ingestion. Its vapors are toxic. Nitrobenzene and its breakdown products leave the body within a few days (ATSDR 9019, 1990). Exposure to nitrobenzene by ingestion may cause general anesthetic, respiratory stimulation, and vascular changes. It may also cause cyanosis due to formation of methemoglobin which affects the ability of the blood to carry oxygen. Experiments indicate reproductive and mutagenic effects of nitrobenzene exposure (Lewis, 1992).

2-3-58-1-2. 4-Nitrobiphenyl

4-Nitrobiphenyl, C₁₂H₉NO₂, is a white to yellow, needle-like crystalline solid with a sweetish odor. It is insoluble in water and very soluble in ether. It reacts with strong reducing agents.

Short-term exposure to 4-nitrobiphenyl may results in irritation of the eyes, mucous membranes, and the respiratory tract. The exposure may also cause headache, nausea, vomiting, and fatigue. Long-term exposure to high concentrations of 4-nitrobiphenyl may result in effects on the peripheral and central nervous systems, liver, and kidney (EPA, 1994c). Nitrobenzene is a human carcinogen (Keith, 1995).

2-3-58-1-3. 4-Nitrophenol

4-Nitrophenol, C₆H₅NO₃, is a colorless to slightly yellow crystalline solid with very little odor. 4-Nitrophenol can be formed in air as a result of the breakdown of many other chemicals. In the environment, most of 4-nitrophenol goes to water and soil. It breaks down easily in surface water, but stays a long time in deep soil and ground water (ATSDR 50, 1995). 4-Nitrophenol is combustible and reacts with oxidizers, many organic combustible substances, and reducing agents (Keith, 1995).

4-Nitrophenol may be toxic by ingestion, inhalation, and absorption through the skin (ATSDR 50, 1995). Acute inhalation or ingestion of 4-nitrophenol may cause headaches, drowsiness, nausea, and cyanosis (blue color in lips, ears, and fingernails). Contact with eyes causes irritation. An animal study reported dermal irritation consisting of erythema, scaling, scabbing, and cracking of the skin (EPA, 1994c).

2-3-58-1-4. N-Nitrosodimethylamine

N-Nitrosodimethylamine, C₂H₆NO₂, is a yellow, combustible liquid. It is soluble in water alcohol, and ether. It reacts with strong oxidizers and strong bases. N-Nitrosodimethylamine is sensitive to light, especially ultraviolet light.

N-Nitrosodimethylamine can enter the human body through inhalation, ingestion, and skin and eye contact. It is an irritant (Keith, 1995). Exposure to N-nitrosodimethylamine for a short time may damage the liver in humans with symptoms that include nausea, vomiting, headaches, and malaise. Prolonged exposure to N-nitrosodimethylamine may cause liver damage and low platelet counts. EPA has classified N-nitrosodimethylamine as a Group B2, probable human carcinogen (EPA, 1994c).

2-3-58-1-5. N-Nitrosomorpholine

N-Nitrosomorpholine, C₄H₈N₂O₂, is a yellow crystalline solid. Its melting point is 29^oC. It dissolves in water and most organic solvents. It reacts with strong oxidizers. N-Nitrosomorpholine is sensitive to light, especially ultraviolet light.

Limited information is available on the health effects of N-nitrosomorpholine. Animal studies have reported tumors of the lung, liver, kidneys, and blood vessels from ingestion of N-nitrosomorpholine. The International Agency for Research on Cancer (IARC) has classified it as a Group 2B, possible human carcinogen. However, EPA has not classified N-nitrosomorpholine for carcinogenicity (EPA, 1994c).

2-3-58-2. Nitrides

Nitrides are compounds with trivalent N as the anion, such as Li₃N, Ca₃N₂. The toxicity of nitrides as a group are unknown in detail. However, many nitrides can react with moisture in air to evolve ammonia gas which is an irritant to mucous membranes (Lewis, 1992).

2-3-58-3. Nitrites

Nitrites are salts of nitrous acid, HNO₂. They are generally powerful oxidizing agents, have violent reactions with readily oxidized materials, and may cause fire or explosion. Organic nitrites may decompose violently on contact with NH₄, salts, cyanide, KCN.

Ingestion of large amounts of nitrites may produce nausea, vomiting, cyanosis, collapse, and coma. Long-term exposure to small amounts of nitrites may cause a fall in blood pressure, rapid pulse, headache, and visual disturbances. Nitrites may react with organic amines in the body to form carcinogenic nitrosamines. Some evidence implicates increased cancer incidence associated with exposure to nitrites (Lewis, 1992).

2-3-59. Phosphorus and compounds

Discussions in this section focus on phosphorus. The general information of inorganic phosphorus compounds is also provided.

2-3-59-1. Phosphorus

Phosphorus, P, exists in three main allotropic forms: white, black, and red. Phosphorus atoms exist as symmetrical, tetrahedral P₄ molecules as liquid and vapor below 800^oC, molecules dissociate to P₂ when the temperature is above 800^oC.

Black phosphorus is polymorphic in orthorhombic crystalline form. It is very stable and insoluble in most solvents (CARB, 1996).

White phosphorus is a colorless to yellow, transparent, cubic crystals with a waxy appearance. It is insoluble in water and alcohol, but is soluble in carbon disulfide, some organic solvents, and oils (CARB, 1996). When exposed to air, it spontaneously ignites to form white fumes and greenish light. White phosphorus is very reactive (EPA, 1994c). It forms compounds with halogens, sulfur, metals, nitric acid, and alkali hydroxides (CARB, 1996).

Red phosphorus exists as a reddish-brown powder. It is flammable at 500^oC but less reactive than white phosphorus (Lewis, 1992). Red phosphorus is insoluble in most solvents. Its properties are intermediate between white and black phosphorus (CARB, 1996).

Selected chemical and physical properties of phosphorus are shown in Table 2-44.

Table 2-44. Selected chemical and physical properties of phosphorus

Phosphorus may enter the human body through inhalation, ingestion, and dermal contact (Sittig, 1985). White phosphorus is extremely toxic to human and short-tern exposure may be fatal with a dose of 15 to 100 mg for adults. Other forms of phosphorus are much less toxic. Acute exposure to high level of white phosphorus may cause gastrointestinal effects and effects on the kidneys, liver, and cardiovascular system. Dermal exposure to white phosphorus may results in severe skin burns(EPA, 1994c). Red phosphorus may also cause eye irritation (Sittig, 1985). Long-term exposure to white phosphorus may lead to necrosis of the jaw, termed "phossy jaw" (EPA, 1994c). EPA has classified white phosphorus as a Group D, not classifiable as to human carcinogenicity, based on no human and animal data regarding the carcinogenic effects of white phosphorus (EPA, 1996).

2-3-59-2. Inorganic Phosphorus Compounds

Most inorganic phosphorus (except phosphine) have relatively low toxic potency, but in large doses they may cause serious disturbances in calcium metabolism. Phosphorus sulfides behave similarly. Metaphosphates may have high toxic potency and cause irritation and hemorrhages in the stomach and damage in the kidneys and liver (Lewis, 1992).

2-3-60. Potassium and Compounds

Potassium, K, is a soft, ductile, silver-white, very reactive metal. Its melting point is 63.65^oC. It is flammable. Potassium is also dangerous when wet. It reacts with moisture and oxygen at room temperature. Potassium may also have explosive reactions with a lot of materials. Potassium’s toxic potency is relatively low (Lewis, 1992). The following compounds are selected to give examples of potassium compounds, not to comprise a comprehensive list.

Potassium arsenite, AsH₃O₃.xK, is a white, hygroscopic powder. It is soluble in water. Potassium arsenite is a confirmed human skin and liver carcinogen. Humans are exposed to potassium arsenite mainly through ingestion and skin contact. The systemic effects include dermatitis and liver changes (Lewis, 1992).

Potassium bichromate, K₂Cr₂O₇, is a bright, yellowish-red, transparent crystalline solid with a bitter and metallic taste. It is a powerful oxidizer and can react explosively with hydrazine. Potassium bichromate is also a confirmed human carcinogen and a poison by ingestion (Lewis, 1992).

Potassium chromate, K₂CrO₄, exists as rhombic, yellow crystals. It is soluble in water but not in alcohols. Potassium chromate is a powerful oxidizer. It is a confirmed carcinogen (Lewis, 1992).

Potassium cyanide, KCN, exists as white crystals with a faint odor of bitter almonds. It dissolves in water and glycerol but is slightly soluble in alcohols. Potassium cyanide reacts with acids and acid fumes to release HCN. It also has explosive reactions with nitrogen trichloride, sodium nitrite, perchloryl fluoride, mercury nitrate at certain conditions. Potassium cyanide can enter the human body through ingestion, inhalation, and absorption via injured skin. It may cause death by all these routes. Strong solutions are corrosive to skin, eyes, and mucous membranes (Lewis, 1992)

2-3-61. Selenium and Compounds

Selenium, Se, is a steel-gray, nonmetallic element. It is insoluble in water and alcohols. It reacts explosively with metal amides (Lewis, 1992). Selenium is often found in combination with other chemicals (ATSDR 8921, 1989; Lewis, 1992). Aquatic organisms easily take up and accumulate selenium and its compounds. Selenium is an essential element for humans and animals, it helps prevent damage by oxygen to tissues. However, excess levels of selenium cause harm to humans and animals. The National Academy of Sciences recommends 200 mg/day as a safe intake level (Longnecker, 1989).

Many selenium compounds are solids, but some are gases such as hydrogen selenide, which is probably the only gaseous selenium compound with a health concern in occupational exposures. Humans can be exposed to selenium in their food (organic compounds) and drinking water (inorganic compounds such as sodium selenate and sodium selenite) but not normally to large amounts of selenium in air, unless selenium dust or volatile selenium compounds are in air. The human body easily absorbs the ingested selenium compounds in the digestive tract and changes inorganic compounds into forms the body can use. Selenium can accumulate in the human body, mostly in the liver and kidneys and, to a lesser extent, in the blood, lungs, heart, testes, and hair (ATSDR 8921, 1989).

Ingesting large amounts of sodium selenate or sodium selenite may cause death without immediate treatment. Prolonged selenium ingestion only slightly above dietary requirements may lead to brittle hair, deformed nails, and even loss of feeling and control in arms and legs (ATSDR 8921, 1989). EPA has classified selenium sulfide and selenium disulfide as Group B2, probable human carcinogens (inadequate human data and sufficient evidence in animals) (EPA, 1996).

2-3-62. Silver and Compounds

Silver, Ag, is a soft, ductile, malleable, lustrous, white metal. Its dust is flammable when exposed to flame or by chemical reaction with some chemicals (Lewis, 1992). Silver is stable but its form depends on environmental conditions. Silver and compounds may be carried long distances in air and water (ATSDR 9024, 1992).

Silver and compounds enter the human body through ingestion, inhalation, or skin contact with solutions containing silver compounds. However, much less silver enters the body through the dermal route than through the lungs and stomach. Most of the silver that enters the body is excreted in feces within about a week. Very little passes through the urine. Silver may accumulate in the body (ATSDR 9024, 1992).

The water-soluble silver compounds are irritants to the skin and mucous membranes and may cause death if ingested (Lewis, 1992). Skin contact with some silver compounds may also cause allergic reactions including rash, swelling, and inflammation. Long-term silver inhalation and ingestion may cause a condition known as argyria at which some areas of the skin and other body tissues turn gray or blue-gray. Argyria is permanent, through it is thought to be only a "cosmetic" problem. Inhalation of high levels of silver compounds, such as silver nitrate or silver oxide, may result in breathing problems, lung and throat irritation and stomach pain. Animal studies suggest that silver may cause kidney problems, however, more studies are needed to determine the human health effects of silver compounds (ATSDR 9024, 1992).

2-3-63. Sodium and Compounds

Sodium, Na, is a light, soft, ductile, malleable, silver-white metal. Its melting point is 97.81^oC. It is flammable and is an explosion hazard when exposed to moisture in any form. Metallic sodium can react exothermically with body moisture or tissue surfaces, causing thermal and chemical burns. Since sodium in elemental form is highly reactive, it combines with other substances in the environment (Lewis, 1992).

The toxicity of sodium compounds varies according to the anion involved. Sodium ion in the compounds is practically nontoxic. For example, sodium hydroxide, NaOH, being strongly basic, is very corrosive and caustic due to the concentration of hydroxyl ion (Lewis, 1992). The following compounds are selected to give examples of sodium compounds, not to comprise a comprehensive list.

Sodium arsenite, NaAsO₂, is a white or grayish-white powder, very soluble in water, and slightly soluble in alcohols (Lewis, 1992). It is nonflammable. Sodium arsenite can absorb carbon dioxide from air. It may be highly toxic via inhalation and ingestion routes (Keith, 1995). It can also enter the human body through skin contact (Lewis, 1992). Exposure to its dust may cause eye irritation. Ingestion or excessive inhalation of its dust may lead to irritation of the stomach and intestines with nausea, vomiting and diarrhea, bloody stools, shock, rapid pulse and coma (Keith, 1995).

Sodium cyanide, NaCN, is an odorless, nonflammable, white crystalline powder. It dissolves in water easily but is only slightly soluble in alcohols. It reacts with acids, releasing highly flammable and toxic hydrogen cyanide gas. Even carbon monoxide in the air is sufficiently acidic to liberate the toxic gas on contact with sodium cyanide. Sodium cyanide can have a mild reaction with water and steam. Its aqueous solutions are strongly alkaline and can readily dissolve gold and silver in the presence of air. Sodium cyanide may be extremely toxic through inhalation, ingestion, or skin absorption. It is a corrosive irritant and can be rapidly absorbed through the skin. Please refer to Section 2-3-49, Cyanide and Compounds, for further health effects of sodium cyanide (Lewis, 1992).

2-3-64. Strontium and Compounds

Strontium, Sr, is a silver-white metal that ignites spontaneously in air. Its dust is moderately explosive by spontaneous chemical reaction or when exposed to flame. Strontium reacts vigorously with water or steam to evolve hydrogen. It also reacts vigorously with oxidizing materials. Its reaction with halogens may lead to ignition. The isotope, ⁹⁰Sr, is a radioactive hazard (Lewis, 1992).

Strontium resembles calcium in its metabolism and behavior. About 5 to 25% soluble strontium is absorbed by the gastrointestinal tract. Acute exposure to strontium compounds may cause excessive salivation, vomiting, colic and diarrhea, and possibly respiratory failure. Strontium ion has relatively low toxic potency. Among strontium compounds, strontium salicylate is the most toxic. Strontium oxides and hydroxides are moderately caustic materials. The toxicity of other strontium compounds may depend upon the anions. Compounds containing the isotope, ⁹⁰Sr, are radioactive hazards (Lewis, 1992). The following compounds are selected to give examples of strontium compounds.

Strontium chromate, SrCrO₄, exists as monoclinic, yellow crystals. It is a confirmed human carcinogen. It also shows moderately toxic potency by ingestion (Lewis, 1992).

Strontium nitrate, SrN₂O₆, is a white powder and a powerful oxidizer. It has moderately toxic potency by ingestion (Lewis, 1992).

2-3-65. Sulfur Compounds

The chemicals described below are intended as selected examples of sulfur compounds, not a comprehensive list.

2-3-65-1. Sulfates

Sulfates are substances containing the sulfate, , ion. The toxicity of sulfates varies. In general, the toxic properties of the sulfates are those of the cation materials with which the sulfate anion is combined (Lewis, 1992).

2-3-65-2. Sulfides

Sulfides are compounds containing S as the anion, such as PbS or Na₂S. They are flammable by spontaneous chemical reaction or when exposed to flame. Many of them ignite easily in air at room temperature. When in contact with moisture or acid, sulfides evolve hydrogen sulfide gas. They may ignite violently on contact with powerful oxidizers.

The toxicity of sulfides varies; hydrogen sulfide is the most toxic. The alkaline sulfides (potassium, calcium, ammonium, and sodium) have similar action to alkalies. They may cause softening and irritation of the skin. They are also corrosive and irritating through ingestion due to the liberation of hydrogen sulfide and free alkali. Sulfides of the heavy metals are generally insoluble in water and have relatively low toxicity except through the liberation of hydrogen sulfide (Lewis, 1992).

2-3-65-3. Sulfites

Sulfites are salts of sulfurous acid, H₂SO₃. They can react with water, steam, or acids to produce a toxic and corrosive material. Since sulfites are rapidly oxidized to sulfates, human may tolerate fairly large amounts, although ingestion may cause irritation of the stomach. Experiments show that sodium sulfite may cause retarded growth, nerve irritation, atrophy of bone marrow, and depression (Lewis, 1992).

2-3-66. Titanium and Compounds

Titanium, Ti, is a dark gray amorphous powder or lustrous white metal. It is flammable during reaction or when exposed to heat or flame. It can burn in an atmosphere of carbon dioxide, nitrogen or air. Some experimental data indicate carcinogenic effects of titanium, but generally are insufficient to determine human carcinogenicity.

In general, titanium compounds are considered to be physiologically inert. However, titanium tetrachloride, TiCl₄, is an irritant, corrosive, colorless liquid with a boiling point of 136.4^oC. It dissolves in cold water and alcohols and can be decomposed by hot water. It can cause irritation of skin, eyes, and mucous membranes (Lewis, 1992).

2-3-67. Vanadium and Compounds

Vanadium, V, is a bright, white, soft, ductile metal. Its dust is flammable when exposed to heat, flame, or sparks (Lewis, 1992). It does not dissolve well in water and can stay in air, water, and soil for a long time. Although low levels of vanadium have been found in plants, it is not likely to accumulate in the tissues of animals.

Humans may be exposed to vanadium through inhalation, ingestion, and skin contact. However, vanadium is not readily absorbed by the body through the gastrointestinal tract or skin. The major health effects following inhalation of high concentrations of vanadium are on the lungs, throat, and eyes, causing lung irritation, coughing, wheezing, chest pain, runny nose, and sore throat. These effects are relatively short-term (ATSDR, 58, 1995). Some experimental data show carcinogenic effects of vanadium, but the data are not sufficient to classify vanadium as to human carcinogenicity (Lewis, 1992).

Vanadium usually combines with other substances such as oxygen, sodium, sulfur or chloride to form vanadium compounds (ATSDR 58, 1995). Vanadium compounds have variable toxicity. They act mainly as an irritant to the conjunctiva and respiratory tract. Acute and chronic exposure to them may cause conjunctivitis, rhinitis, bronchospasms, and in severe cases, asthma-like disease (Lewis, 1992).

2-3-68. Zinc and Compounds

Zinc, Zn, is a bluish-white, lustrous, shiny, flammable metal. It is stable in dry air but unstable when wet. Zinc dust reacts explosively with acids (Lewis, 1992).

Zinc combines with other substances to form zinc compounds in the environment. When released, zinc and compounds attach to soil, sediments, and dust particles in air. They can move from air into soil, lakes, stream, and rivers by rain and snow. Zinc can build up in fish but not in plants (ATSDR 60, 1995).

Zinc is an essential human nutrient. The recommended dietary allowance for zinc is about 5-15 mg/day. Ingestion of large amounts of zinc may cause stomach cramps, nausea, and vomiting. Long-term exposure to zinc by ingestion may cause anemia, pancreas damage, and lower levels of high density lipoprotein cholesterol (the good form of cholesterol). Zinc is also a skin irritant (ATSDR 60, 1995). Pure zinc is relatively non toxic. When heated, fumes of zinc oxide are evolved and inhaled may cause throat dryness, cough, weakness, general aches, chills, fever, nausea, and vomiting (Lewis, 1992).

Zinc compounds have variable toxicity, but, generally, low toxic potency. However, zinc salts, such as chromates and arsenates, may be carcinogens. Soluble zinc salts have a harsh metallic taste. Exposure to small amounts of these salts may cause nausea and vomiting, while exposure to large amounts of them may cause violent vomiting. Zinc chloride and zinc sulfate are caustic and can cause ulceration of the fingers, hands, and forearms (Lewis, 1992).

2-3-69. Zirconium and Compounds

Zirconium, Zr, is a flammable grayish-white, lustrous metal. It may ignite spontaneously. Its dust is an explosion hazard by chemical reaction with air and certain substances. Inhalation of zirconium-containing aerosols can cause lung granulomas. Most zirconium compounds are insoluble and considered inert, but some soluble zirconium compounds may pose harmful effects on human health (Lewis, 1992). Several zirconium compounds are described below as examples.

Zirconium nitrate, ZrN₄O₁₂, forms white hygroscopic crystals that are very soluble in water and alcohols. Zirconium nitrate is a powerful oxidizer. It has moderate toxicity by inhalation and ingestion (Lewis, 1992). More information is presented in Section 2-3-57-1, Nitrates.

Zirconium oxychloride, ZrCl₂O, is very soluble in water and alcohols. It is a potential carcinogen. It is moderately toxic by ingestion (Lewis, 1992).

Zirconium sulfate, Zr(SO₄)₂, forms a tetrahydrate, crystalline solid. It has moderately toxic potency by ingestion. Experimental data have show reproductive effects associated with its exposure, but the data are preliminary (Lewis, 1992). More information is presented in Section 2-3-65-1, Sulfates.

2-3-70. Total Polycyclic Aromatic Hydrocarbons (PHAs)

PAHs are a group of chemicals which are the dominant components of polycyclic organic matter (POM). In Section 112 (C)(6) emission inventory (EPA, 1994c), EPA has identified a subset of 16 PAHs which include compounds in Table 2-45.

The Great Lakes Commission Regional Emission Inventory of Toxic Air Contaminants Steering Committee intend to use a sum of the 16-PAH emissions to represent the total PAH emissions, if an emission factor for the total PAHs is not specified.

PAHs generally exist as colorless, white, or pale yellow-green solids and do not burn easily (Sittig, 1985; ATSDR 9020, 1990). Most PAHs are not found alone, but rather as mixtures of two or more compounds. Some PAHs readily evaporate into the air, but most PAHs do not dissolve easily in water. PAHs can persist in the environment for months to years (ATSDR 9020, 1990).

Humans may be exposed to PAHs through inhalation of PAH vapors or PAHs that are attached to dust and other particles in the air. Humans may also be exposed to PAHs through drinking water or swallowing food, soil, or dust particles that contain PAHs. PAHs may enter the human body by skin contact. When PAHs enter the human body, they tend to be distributed to and stored mostly in fatty tissues, kidneys, and liver, with smaller amounts in spleen, adrenal glands, and ovaries. Most PAHs leave human body within a few days, primarily in the feces and urine (ATSDR 9020, 1990).

Seven of the sixteen PAHs are anticipated to be carcinogens (Table 2-45). Animal studies show that exposure to PAHs may cause harmful effects on skin, body fluids, and the immune system (ATSDR 9020, 1990).

2-3-71. Polycyclic Organic Matter (POM)

Polycyclic organic matter (POM) is a group of organic compounds which consists of more than one benzene ring, and which have a boiling point greater than or equal to 100^oC (CAA, 1990). PAHs are the most commonly encountered POM. POM is produced by the incomplete combustion of fossil fuels and vegetable matter (CARB, 1996). The Great Lakes Commission Regional Emission Inventory of Toxic Air Contaminants Steering Committee intend to use a sum of the 16-PAH emissions to represent the POM emissions, if an emission factor for the POM is not specified. More information is presented in Section 2-3-70, Total Polycyclic Aromatic Hydrocarbons.

2-4. References

ATSDR 15, Fact sheet: Nickel, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts15.html, April, 1993.

ATSDR 22, Fact sheet: Aluminum, Agency for Toxic Substances and Disease Registry, ht.//atsdr1.atsdr.cdc.gov:8080/tfacts22.html, September 1995.

ATSDR 23, Fact sheet: Antimony, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts23.html, September 1995.

ATSDR 24, Fact sheet: Barium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts24.html, September 1995.

ATSDR 28, Fact sheet: 1,3-Butadiene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts28.html, September 1995.

ATSDR 29, Fact sheet: 2-Butanone, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts29.html, September 1995.

ATSDR 3, Fact sheet: Benzene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts3.html, April, 1993.

ATSDR 33, Fact sheet: Cobalt, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts33.html, September, 1995.

ATSDR 34, Fact sheet: Cresol, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts37.html, September 1995.

ATSDR 37, Fact sheet: 1,2-Dibromoethane, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts37.html, September 1995.

ATSDR 46, Fact sheet: Mercury, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts46.html, September, 1995.

ATSDR 50, Fact sheet: Nitrophenols, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts50.html, September, 1995.

ATSDR 53, Fact sheet: Styrene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts53.html, September 1995.

ATSDR 56, Fact sheet: Toluene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts56.html, September 1995.

ATSDR 58, Fact sheet: Vanadium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts58.html, September, 1995.

ATSDR 60, Fact sheet: Zinc, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts60.html, September, 1995.

ATSDR 7, Fact sheet: Chromium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts7.html, April 1993.

ATSDR 8, Fact sheet: Cyanide, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/tfacts8.html, April, 1993.

ATSDR 8802, Public Health Statement: Xylene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8802.html, March 1989.

ATSDR 8803, Public Health Statement: Polycyclic Aromatic Hydrocarbon (PAHs), Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8803.html, May 1989.

ATSDR 8805, Public Health Statement: Benzo(a)pyrene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8805.html, May 1990.

ATSDR 8808, Public Health Statement: Cadmium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8808.html, March 1989.

ATSDR 8810, Public Health Statement: Chromium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8810.html, July 1989.

ATSDR 8811, Public Health Statement: Chrysene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8811.html, March 1990.

ATSDR 8812, Public Health Statement: Cyanide, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8812.html, December, 1989.

ATSDR 8814, Public Health Statement: 1,4-Dichlorobenzene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8814.html, January 1989.

ATSDR 8817, Public Health Statement: Lead, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8817.html, June, 1990.

ATSDR 8819, Public Health Statement: Nickel, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8819.html, December, 1988.

ATSDR 8916, Public Health Statement: Mercury, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8916.html, December, 1990.

ATSDR 8920, Public Health Statement: Phenol, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8920.html, December 1989.

ATSDR 8921, Public Health Statement: Selenium, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8921.html, December, 1989.

ATSDR 8923, Public Health Statement: Toluene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs8923.html, December 1989.

ATSDR 9, Formaldehyde Patient Information, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/mmg9.html, July 1, 1995.

ATSDR 9006, Public Health Statement: Chlorobenzene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9006.html, December 1990.

ATSDR 9008, Public Health Statement: Copper, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9008.html, December, 1990.

ATSDR 9015, Public Health Statement: Ethylbenzene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9015.html, December 1990.

ATSDR 9019, Public Health Statement: Nitrobenzene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9019.html, December, 1990.

ATSDR 9020, Public Health Statement: Polycyclic Aromatic Hydrocarbon (PAHs), Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9020.html, December 1990.

ATSDR 9024, Public Health Statement: Silver, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9024.html, March, 1992.

ATSDR 9030, Public Health Statement: Xylene, Agency for Toxic Substances and Disease Registry, http://atsdr1.atsdr.cdc.gov:8080/ToxProfiles/phs9030.html, December 1990.

CAA, Clean Air Act Amendments, Public Law #101-549, Section 301, November 15, 1990.

CARB, Speciation Manual, Volume 1: Identification of Volatile Organic Compound Species Profiles, Volume 2: Identification of Particulate Matter Species Profiles, 2nd Edition, State of California Air Resource Board, August 1991.

CARB, Toxic Air Contaminant Identification List: Compound Summaries, Draft, State of California Air Resource Board, January 1996.

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