Great Lakes Binational Toxics Strategy

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DRAFT Report on Level II Substances in the Binational Toxics Strategy

A U.S. Perspective

U.S. EPA
Great Lakes National Program Office
December 1, 1999

1.0 BACKGROUND

The Great Lakes Binational Toxics Strategy: Canada-United States Strategy for the Virtual Elimination of Persistent Toxic Substances in the Great Lakes, also known as the Binational Toxics Strategy, or BNS, was signed on April 7, 1997, by Environment Canada and the United States Environmental Protection Agency (USEPA). The Binational Toxics Strategy was set forth to protect and ensure the health and integrity of the Great Lakes ecosystem. Environment Canada and USEPA in consultation with other federal departments and agencies, Great Lakes States, the Province of Ontario, Tribes and First Nations have agreed to cooperate with their public and private partners toward the goal of virtual elimination of persistent toxic substances resulting from human activity.

Under the Strategy, action will occur first on "Level 1" substances. Level 1 substances have been identified for priority action by multiple screening criteria and processes. The Level 1 substances have been linked to or have the potential to cause deleterious environmental impacts in the Great Lakes Basin. They occur in the water, sediment or aquatic biota of the Great Lakes ecosystem and exert, singly or in a synergistic or additive combination, a toxic effect on aquatic, animal, or human life. The Level 1 substances represent an immediate priority for virtual elimination through pollution prevention and other actions that phase out their use, generation or release in a cost-effective manner. The governments (EC & USEPA) will concentrate and lead actions and efforts around these substances.

The Strategy also includes actions for "Level 2" substances. These substances have been identified by one or both countries as having the potential to cause a significant impact on the Great Lakes ecosystem. The two nations have agreed to share information regarding the persistence, bioaccummulation potential, and toxicity of Level 2 substances. Stakeholders will be encouraged to undertake pollution prevention activities to reduce levels in the environment of those substances nominated jointly by both governments. For those substances nominated by only one country stakeholders are encouraged to conform with the laws and policies of each country, including pollution prevention programs.

EC and the USEPA have promised to periodically examine the Level 2 substances in cooperation with their partners to determine whether any Level 2 substances should be elevated to the Level 1 list. If a Level 2 substance is elevated to Level 1 status, a binational virtual elimination challenge will be set.

Nominations of substances from Level 2 to Level 1 would occur through consultation with stakeholders on proposed changes to the lists at the biennial meetings or other appropriate forum. There will be no new nomination process initiated by the Strategy. Instead, existing processes for nominating or elevating substances will be used, i.e. Bioaccummulative Chemicals of Concern (BCCs) in the U.S., Toxic Substances Management Policy (TSMP), the Canada-Ontario Agreement (COA), and the Priority Substances List process under the Canada Environmental Protection Act (CEPA) in Canada or Lakewide Management Plans (LaMP) Critical Pollutants

The focus of this report is to provide a brief background on Level 2 substances in the United States, including sources, uses, and environmental levels, and to examine current activities related to these substances underway in the U.S., or internationally with U.S. involvement.

[It should be noted that the information in this draft report provides only a preliminary characterization based on the selected sources of information listed in Table 2 and is by no means a comprehensive assessment of the Level 2 substances.]

2.0 LEVEL 2 SUBSTANCES

Table 1 lists the substances designated as Level 2 substances under the Binational Toxics Strategy.

Table 1. Great Lakes Binational Toxics Strategy: Level 2 Substances

cadmium and cadmium compounds^2,4

1,4-dichlorobenzene²

3,3'-dichlorobenzidine²

dinitropyrene²

endrin⁵

heptachlor (and heptachlor epoxide)⁵

hexachlorobutadiene and hexachloro-1,3-butadiene¹

hexachlorocyclohexane^1,2,4,6

4,4'-methylenebis(2-chloroaniline)²

pentachlorobenzene¹

pentachlorophenol²

tetrachlorobenzene (1,2,3,4- and 1,2,4,5-)¹

tributyl tin²

PAHs as a group, including anthracene, benzo(a)anthracene, benzo(ghi)perylene, perylene, and phenanthrene²

Legend:

¹ U.S. BCC²Canadian COA³ IJC Critical Pollutant⁴ LaMP Lakewide Critical Pollutant⁵ POPs from CEC Council Resolution #95-5⁶ In Canada, all agricultural pesticides were excluded from the COA Tier II list and are dealt with separately under COA and are not Canadian nominations to this list.

Each Level 2 substance is discussed in more detail below. Table 2 lists the primary sources of information used to prepare this report. A glossary of terms and acronyms used in this report is provided in Table 3 at the end of the report.

Table 2. Sources of Information Used to Prepare this Report on Binational Toxics Strategy Level 2 Substances
Level 2 Substance	Data Sources¹				Current Activities
Level 2 Substance	RAPIDS	TRI	ATSDR	Other possible databases	Current Activities
cadmium	X	X	X	BRS, Superfund, HSDB, IADN	National Fish Study (Tier I), Urban Air Toxics Program, Great Waters Program, LaMPs, LRTAP
1,4-dichlorobenzene		X	X	BRS, Superfund, HSDB	National Fish Study (Tier II)
3,3'-dichlorobenzidine		X	X	BRS, Superfund, HSDB	National Fish Study (Tier II)
dinitropyrene					National Fish Study (Tier II)
endrin			X	BRS, Superfund, HSDB, IADN	National Fish Study (Tier I), UNEP POPs, LRTAP
heptachlor (and heptachlor epoxide)		X	X	BRS, Superfund, HSDB, IADN	National Fish Study (Tier I), UNEP POPs, LRTAP, NHANES, TRI PBT Rule
hexachlorobutadiene and hexachloro-1,3-butadiene		X	X	BRS, Superfund, HSDB	U.S. BCC, National Fish Study (Tier II)
hexachlorocyclohexane			X	BRS, Superfund, HSDB, IADN	U.S. BCC, National Fish Study (Tier I), LaMPs, Great Waters Program, LRTAP use restrictions
4,4'-methylenebis(2-chloroaniline)		X	X	BRS, Superfund, HSDB	National Fish Study (Tier II)
pentachlorobenzene				BRS, Superfund, HSDB	U.S. BCC, National Fish Study (Tier II), TRI PBT Rule
pentachlorophenol	X	X	X	BRS, Superfund, HSDB	National Fish Study (Tier I)
tetrachlorobenzene (1,2,3,4- and 1,2,4,5-)				BRS, Superfund, HSDB	U.S. BCC, National Fish Study (Tier II)
tributyl tin			(Tin)	BRS, Superfund, HSDB	National Fish Study (Tier I)
PAHs as a group, including anthracene, benzo(a)anthracene, benzo(ghi)perylene, perylene, and phenanthrene	PAHs as a group and benzo(a)-anthracene	polycyclic aromatic compounds, anthracene, and phenanthrene	PAHs as a group	BRS, Superfund, HSDB, IADN, CAA Section 112(c)(6) Inventory	LRTAP, National Fish Study (Tier I and Tier II), TRI PBT Rule

¹ See glossary in Table 3 for definition of acronyms.

2.1 CADMIUM AND ITS COMPOUNDS

Current Status: Commercially used

Sources
Cadmium [CAS Registry Number 7440-43-9] is an element found in the earth's crust at concentrations of 1-2 ppm, primarily in association with zinc ores. Cadmium is used for the production of nickel-cadmium batteries, metal plating, pigments, plastics and synthetics, and for alloys and other uses. Major industrial sources of cadmium use and release to the environment include zinc, lead, and cadmium smelting; coal and oil combustion; pigment manufacturing; and municipal and sewage sludge incineration.

Releases and Environmental Levels
The 1998 Great Lakes Regional Air Toxic Emissions Inventory reports 1993 estimated cadmium emissions to be distributed as follows: secondary nonferrous metals (69%), electrical generating facility (6%), metal coating and allied services (4%), and other sources (21%). Estimated U.S. air emissions of cadmium are expected to be included in the draft 1993 National Toxics Inventory due to be released by EPA in Fall 1999. Releases to surface and ground water include discharges from industrial facilities and sewage treatment plants and leaching from landfills or soil. Cadmium may also leach to drinking water supplies from distribution pipes. The use of phosphate fertilizer and the application of sewage sludge are the primary sources of cadmium to soil and may contribute to greater human exposures due to food chain accumulation in plants and animals. Cadmium was detected in soil at 287 of 388 NPL hazardous waste sites where it was measured.

Toxicity and Exposure
The International Agency for Research on Cancer (IARC) has determined that there is sufficient evidence in humans for the carcinogenicity of cadmium and cadmium compounds. For nonsmokers, food is the primary route of exposure to cadmium, particularly grain and cereal products. The results of an FDA Total Diet Study done in the mid-1980's found cadmium in nearly all samples analyzed, with the highest levels in leafy vegetables and potatoes. Smokers may have double the cadmium exposure due to inhalation of cigarette smoke, which contains cadmium taken up by tobacco. NIOSH recommends that cadmium be treated as a potential human carcinogen, and OSHA has set limits for allowable airborne exposure for employees.

Regulations
Releases of cadmium are reported to TRI. There are federal drinking water guidelines for cadmium, and cadmium is subject to effluent limitations as a toxic pollutant under the CWA. Cadmium wastes are subject to treatment, storage, and disposal regulations. Under RCRA regulations, cadmium must be managed as a hazardous waste, if so characterized, and pretreatment is required before land disposal. EPA limits apply for sludge applied to land used for production of food chain crops. Incineration of cadmium wastes is not recommended; scrap metals and batteries containing cadmium may be recycled.

Additional programs addressing cadmium include IADN monitoring, the Great Lakes Regional Air Toxic Emissions Inventory Project, the proposed National Study of Chemical Residues in Fish, EPA's Urban Air Toxics program, the Great Waters Program, and Great Lakes Lakewide Management Plans.

2.2 1,4-DICHLOROBENZENE

Current Status: Commercially produced

Sources
The principal use, accounting for 35%-50% of its use, of 1,4-dichlorobenzene [CAS Registry Number 106-46-7] is as a space deodorant for toilets and refuse containers and as a fumigant for control of moths, molds, and mildews. The production of polymer resin accounts for approximately 20% of 1,4-dichlorobenzene use. It is also used as an intermediate in the production of other chemicals (10%) and for the control of tree-boring insects and mold in tobacco seeds.

Releases and Environmental Levels
Because 1,4-dichlorobenzene is highly volatile, most environmental releases are to air. Use of consumer products is the major source of release; industrial releases comprise a much smaller percentage of total environmental releases. There are no natural sources of 1,4-dichlorobenzene. An estimated 51 million pounds of 1,4-dichlorobenzene was released to the atmosphere in 1990 from its use as a space deodorant and moth repellant.

Some industrial releases to surface water and publicly owned treatment works are reported, and releases to groundwater by underground injection and leaching from industrial and municipal landfills have also been reported. However, overall, very little 1,4-dichlorobenzene is estimated to be released to water. In 1982, 1,4-dichlorobenzene was reported in Great Lakes sediments at concentrations of 2-210 ppb and in sediments near a hazardous waste site.

Toxicity and Exposure
Based on evidence of carcinogenicity in animals, 1,4-dichlorobenzene is considered by IARC as possibly carcinogenic to humans. The primary route of human exposure is inhalation of 1,4-dichlorobenzene released to air as a result of uses as a space deodorant and moth repellant. Exposures from water and food are generally low. Studies from the 1980s indicate that the general population is exposed to 1,4-dichlorobenzene. Of 46 composite samples analyzed for The National Human Adipose Tissue Survey (NHATS), 1,4-dichlorobenzene was detected in 100% of samples at concentrations of 12-500 ppb. Dichlorobenzene was also identified in 100% of 42 human breast milk samples collected from five urban areas throughout the U.S. The highest exposures are occupational, resulting from the production or processing of 1,4-dichlorobenzene. NIOSH recommends that 1,4-dichlorobenzene be treated as a potential human carcinogen. OSHA has set a Permissible Exposure Limit for 1,4-dichlorobenzene (75 ppm for an 8-hour workday).

Regulations
Releases of 1,4-dichlorobenzene are reported to TRI. 1,4-Dichlorobenzene is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA), and standards of performance are required for equipment leaks of volatile organic compounds (VOCs) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI), which produces 1,4-dichlorobenzene (40 CFR 60.489). National emission standards for hazardous air pollutants (NESHAP) for the pesticide active ingredient production source category also apply under Section 112 of the CAA.

Federal, and several state, drinking water guidelines apply. 1,4-Dichlorobenzene is designated a toxic pollutant under the Clean Water Act and, as such, is subject to effluent limitations. Under CERCLA, 1,4-dichlorobenzene is designated a hazardous substance, and releases greater than or equal to 100 pounds must be reported to the National Response Center. Under TSCA, manufacturers of this chemical must report to EPA preliminary assessment information concerned with production, use, and exposure (40 CFR 712.30). EPA's Health and Safety Data reporting Rule, promulgated under Section 8(d) of TSCA, requires manufacturers, importers, and processors to submit to EPA copies and lists of unpublished health and safety studies (40 CFR 716.120). 1,4-Dichlorobenzene is subject to RCRA hazardous waste regulations and is included in the 1988 FIFRA pesticide re-registration amendments (USEPA/OPP; Status of Pesticides in Re-registration and Special Review (June, 1994) EPA 738-R-94-008). 1,4-Dichlorobenzene is included in the proposed National Study of Chemical Residues in Fish.

2.3 3,3'-DICHLOROBENZIDINE

Current Status: Commercially produced

Sources
3,3'-Dichlorobenzidine (3,3'-DCB) [CAS Registry Number 91-94-1] is used to produce yellow, orange, and red pigments for the printing ink, textile, paper, paint, rubber, plastic, and related industries. It is also used as a compounding ingredient for rubber and plastics, and in the formulation of a raw material used to produce polybenzimidazole (PBI), which is used in protective clothing such as firefighting and welding garments. The chemical does not occur naturally in the environment.

Releases and Environmental Levels
3,3'-DCB is released to the environment primarily though wastewaters, sludges, and solid wastes where emissions are poorly controlled during production and use. Closed systems required for its manufacture are thought to minimize air releases. 3,3'-DCB was detected in the ground and surface water at very few hazardous waste sites, but soil contamination was detected at 4.4% of approximately 500 hazardous waste sites.

3,3'-DCB may bioconcentrate in aquatic organisms, but biomagnification in the food chain is not certain. It was found to rapidly accumulate in bluegill sunfish as a result of exposure, but in 1979, was not detected in fish collected near textile and dye manufacturers using 3,3'-DCB. 3,3'-DCB is included in the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
3,3'-DCB is considered by IARC as possibly carcinogenic to humans. There is sufficient evidence of carcinogenicity in animals. NIOSH recommends that 3,3'-DCB be treated as a potential human carcinogen. Although no Permissible Exposure Limit has been set, OSHA has identified 3,3'-DCB as an occupational carcinogen and requires worker exposure to be controlled (29 CFR 1910.1007). The major routes of exposure appear to be associated with the production and use of 3,3'-DCB based dyes through inhalation of airborne dust, drinking contaminated water near hazardous waste sites, and dermal contact in occupational settings. Although NIOSH expects the greatest exposure to 3,3'-DCB to occur through dermal absorption or inhalation exposure by workers handling dry powders, EPA has concluded that dermal exposure by workers is probably a minor route of exposure. The risk of exposure may vary according to operating procedures and precautionary measures from plant to plant.

Regulations
Releases of 3,3'-DCB are reported to TRI. 3,3'-DCB is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). 3,3'-DCB is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). Under the CWA, EPA has also recommended criteria which correspond to levels which may result in incremental increase of cancer risk over the lifetime (USEPA; Quality Criteria for Water 1986: Dichlorobenzidine (May 1,1986) EPA 440/5-86-001). Under CERCLA, 3,3'-DCB is designated a hazardous substance, and releases greater than or equal to 1 pound must be reported to the National Response Center. 3,3'-Dichlorobenzidine is also subject to RCRA hazardous waste regulations (40 CFR 261.33).

2.4 DINITROPYRENE

Current Status: Diesel engine combustion product; present as three isomers

Sources
1,3-Dinitropyrene [CAS Registry No. 75321-20-9], 1,6-dinitropyrene [CAS Registry No. 42397-64-8], and 1,8-dinitropyrene [CAS Registry No. 42397-65-9] are members of a class of structurally related chemicals called nitroarenes. The chemicals in this class meet the criteria established for listing as "reasonably anticipated to be a human carcinogen", primarily on the basis of carcinogenicity results with experimental animals. These chemicals have limited intentional uses but are normally found in particulate emissions from many combustion sources, most notably diesel exhausts. The chemicals also show the ability to cause gene mutations or changes in the structure of DNA in the tissues of animals as well as humans.

Although 1,8-dinitropyrene has been reported to be a photosensitizer, there is no evidence that 1,6-dinitropyrene or 1,8-dinitropyrene are used for other than laboratory applications. However, for each of these compounds, one American company is known to produce (SRI, 1992) and three American suppliers have been identified (Chem Sources, USA, 1992). No data on imports or exports were available.

Toxicity and Exposure
The primary route of potential human exposure to 1,6-dinitropyrene and 1,8-dinitropyrene is inhalation. Detectable levels have been found in ambient atmospheric samples. Higher amounts have been reported in heavy industrialized areas than in non-industrialized urban and suburban sites. 1,6-Dinitropyrene and 1,8-dinitropyrene have been found in various concentrations in extracts of particles from the exhaust of heavy-duty and light-duty diesel engines. They have also been found in small amounts in particulate emissions from kerosene heaters and gas burners. Prior to 1980, some carbon black samples known to be used in photocopy machines were found to contain considerable quantities of 1,6-dinitropyrene and 1,8-dinitropyrene.

On the basis of a draft health assessment dated February 1, 1998, prepared by the Washington office of the National Center for Environmental Assessment, a risk assessing program in EPA's Office of Research and Development, EPA is considering additional restrictions on emissions from diesel cars and trucks.

Regulations
Neither 1,6-dinitropyrene nor 1,8-dinitropyrene is listed in the National Occupational Exposure Survey or the National Occupational Hazard Survey conducted by NIOSH. OSHA regulates 1,6-dinitropyrene and 1,8-dinitropyrene under the Hazard Communication Standard and as chemical hazards in laboratories. 1,6-Dinitropyrene and 1,8-dinitropyrene are included in IADN monitoring. Dinitropyrene is a recommended analyte for the proposed National Study of Chemical Residues in Fish.

2.5 ENDRIN

Current Status: Canceled pesticide

Sources
Endrin [CAS Registry Number 72-20-8] is a pesticide that is no longer manufactured in the U.S. since the voluntary cancellation of registration with the Office of Pesticide Programs in 1991. Food tolerances were revoked in 1993. Chemically similar to aldrin/dieldrin, endrin was used as a pesticide beginning in 1951 to control cutworms, voles, grasshoppers, and other pests on cotton, sugarcane, tobacco, apple orchards, and grain. Unlike aldrin/dieldrin, however, endrin was never used extensively to control termites or other pests in urban areas. It was used as an insecticide on bird perches and is toxic to raptors and migratory birds.

Releases and Environmental Levels
Endrin is expected to bioconcentrate significantly in aquatic organisms. Although endrin applied to the surface of soils will volatilize within days, it is thought to have limited mobility in soils and sediments. In air, endrin will absorb to particulates and may redeposit to water or soil by air deposition.

Based on the limited data available, current environmental levels in all media are below levels of concern. Endrin is not required to be reported to TRI. Endrin has been identified in air samples at 4 of 102 NPL hazardous waste sites, in surface water samples at 10 of 102 sites, in groundwater samples at 37 of 102 sites, and in soil at 44 of 102 sites. Some studies in Oklahoma indicate that endrin is still being released to surface water from farmland soils historically treated with endrin. Information from EPA's STORET database showed a significant number of detections for endrin in surface water (32% of 8,789 samples), though the national median concentration was near detection limits at 0.001 ppb. In 1991-1992, endrin was detected in initial stormwater runoff samples at 4 of 6 sites in Louisville, Kentucky, at levels above U.S. federal criteria but was not detected in 3-hour composite samples at any of the sites.

Toxicity and Exposure
Endrin is not classifiable as to carcinogenicity in humans. Although no significant releases to the U.S. environment are thought to remain, risk of exposure remains from endrin persisting in soils and sediments. This exposure is expected to steadily decrease over time. In addition, endrin may still be used as a pesticide agent in foreign countries.

The FDA has concluded that endrin levels in the environment are no longer a regulatory concern for contamination of food or feed stocks. Contamination of fish or shellfish is also not thought to present a significant risk of exposure to endrin. The current potential for exposure appears to be limited to imported foodstuffs, unused stocks, unregistered use, improper disposal, and hazardous waste sites.

Regulations
Endrin is included in the proposed National Study of Chemical Residues in Fish, IADN monitoring, and UN ECE Convention on Long-Range Transboundary Air Pollution (LRTAP) protocol and UNEP POPs negotiations.

2.6 HEPTACHLOR (AND HEPTACHLOR EPOXIDE)

Current Status: Canceled pesticide permitted for use in power transformers for fire ant control

Sources
Heptachlor [CAS Registry Number 76-44-8] was first registered for use in the U.S. in 1952, but nearly all registered uses were canceled in 1974 due to the potential cancer risk and persistence and bioaccummulation in the food chain. Heptachlor is a constituent of chlordane (approximately 10% by weight), and heptachlor epoxide [CAS Registry Number 1024-57-3] is an oxidation product of heptachlor and chlordane. The sale, distribution, and shipment of existing stocks of canceled heptachlor and chlordane products were prohibited in the U.S. in 1988. Heptachlor is still commercially produced today. The only remaining commercial use of heptachlor that is permitted is fire ant control in power transformers.

Heptachlor is a persistent insecticide. Between 1953 and 1974, heptachlor was used extensively as a soil and seed treatment on corn, small grains, and sorghum. It was also used to control ants, termites, maggots, cutworms, fireworms, and household insects. The use of existing stocks (mainly for termite control) by homeowners is still permitted.

Releases and Environmental Levels
Heptachlor is converted to heptachlor epoxide in the environment. Heptachlor epoxide degrades more slowly and is more persistent than heptachlor. Heptachlor epoxide has been found in food crops grown in soils previously treated with heptachlor. Both substances bioconcentrate in aquatic and terrestrial organisms and are significantly biomagnified in aquatic food chains.

Heptachlor has been found in air, surface water, ground water, soil, sediment, fish, wildlife, food, and humans. For example, in 1986, heptachlor was reported in seven of nine households in the southeastern U.S. at indoor air levels ranging to 0.02 ppb. Concentrations of heptachlor in groundwater from five states in EPA's Pesticides in Groundwater Database (1988) ranged from 0 to 0.81 ppb with a mean of 0.068 ppb. As part of the National Contaminant Biomonitoring Program conducted by the U.S. Fish and Wildlife Service, heptachlor concentrations in freshwater fish collected in 1984 were highest in Hawaii and the Midwest, especially in Lake Michigan and the Ohio and Illinois Rivers.

Toxicity and Exposure
Heptachlor has been shown to be carcinogenic in experimental animals and is possibly carcinogenic to humans. Exposure to heptachlor and heptachlor epoxide occurs primarily through the diet. Infants and toddlers may be exposed to higher levels than adults, particularly through milk. Individuals living near hazardous waste sites may also be exposed through inhalation of heptachlor and heptachlor epoxide that volatilizes from the soil or by ingestion of contaminated soil. Residents of homes treated for termites with heptachlor in the past may be exposed to higher than background levels, particularly people in the southeastern U.S., where a higher proportion of homes were treated with heptachlor for termite control. The United Nation's Food and Agriculture Organization and the World Health Organization have set an Acceptable Daily Intake for heptachlor of 0.5µg/kg/day. Heptachlor epoxide was found in 62% of human milk samples taken from Canadian women in 1982, and in 63% of breast milk samples collected from women in the U.S. The highest levels were detected in samples from women in the southeastern states of the U.S.

Workers exposed to heptachlor during its manufacture and application for fire ant control are also at increased risk. NIOSH has recommended that heptachlor be treated as a potential human carcinogen. OSHA has set a Permissible Exposure Limit of 0.5 mg/m³ for an 8-hour workday.

Regulations
Heptachlor releases are reported to TRI. Heptachlor is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). Heptachlor is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). Under the CWA, EPA has recommended criteria which correspond to levels that may result in incremental increase of cancer risk over a lifetime (USEPA; Quality Criteria for Water 1986: Heptachlor (May 1,1986) EPA 440/5-86-001). Under CERCLA, heptachlor is designated a hazardous substance, and releases greater than or equal to 1 pound must be reported to the National Response Center. Heptachlor is also subject to RCRA hazardous waste regulations (40 CFR 261.33).

Heptachlor is included in UN ECE Convention on Long-Range Transboundary Air Pollution (LRTAP) protocol and UNEP POPs negotiations. Heptachlor epoxide is included the National Health and Nutrition Examination Survey (NHANES) IV, the proposed National Study of Chemical Residues in Fish, and the IADN monitoring network.

2.7 HEXACHLOROBUTADIENE AND HEXACHLORO-1,3-BUTADIENE

Current Status: Inadvertent by-product; imported for commercial uses

Sources
The primary source of hexachlorobutadiene [CAS Registry Number 87-68-3] in the U.S. is its inadvertent production in the manufacture of chlorinated solvents such as tetrachloroethylene, trichloroethylene, and carbon tetrachloride. Waste streams generated from these production processes typically contain 33-80% hexachlorobutadiene. Hexachlorobutadiene is not produced in commercial quantities in the U.S. but is imported for use as a chemical intermediate in the production of rubber compounds, and to a lesser extent, as a solvent, heat-transfer liquid, hydraulic liquid, fluid for gyroscopes, and chemical intermediate in the manufacture of chlorofluorocarbons and lubricants. In other countries, hexachlorobutadiene is used as a fumigant. It is not known to occur naturally.

Releases and Environmental Levels
According to 1990 TRI reports, 4,906 pounds of hexachlorobutadiene were emitted to the air from facilities in the U.S. manufacturing it as a by-product. The average ambient air concentration of hexachlorobutadiene in the U.S., based on 72 samples from urban and source-dominated areas, reported in 1988, was 0.38µg/m³ (36 ppt). In 1984, hexachlorobutadiene was reported in Niagara River water at a concentration of 0.82 ppt and in river sediments at 2.9-11µg/kg. Hexachlorobutadiene was not reported in a 1984 study in rain water or urban storm water runoff for a number of U.S. cities but was detected in the Gulf of Mexico at 3-15 ppt. Hexachlorobutadiene was not reported above the median detection limit of 0.5 ppm in 196 sediment samples in the STORET database in 1985. Studies conducted in the 1980s generally found no detectable levels of hexachlorobutadiene in fish from the Great Lakes, with the exception of trout from Lake Ontario. Hexachlorobutadiene is included in the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
Hexachlorobutadiene has been identified as a suspected human carcinogen. Diet is not thought to be a major route of exposure. Hexachlorobutadiene was not detected in an analysis of milk, egg, and vegetable samples collected in the U.S. near chlorinated hydrocarbon plants. Residents and workers at or near hazardous waste sites and chlorinated solvent production plants may be more highly exposed to hexachlorobutadiene than the general population. NIOSH recommends that hexachlorobutadiene be regulated as a potential human carcinogen. A vacated 1989 OSHA Permissible Exposure Limit (0.02 ppm) is still enforced in some states.

Regulations
Releases of hexachlorobutadiene are reported to TRI. Hexachlorobutadiene is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). It is included in federal and several state drinking water guidelines. Hexachlorobutadiene is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). It has been listed as a Bioaccummulative Chemical of Concern in EPA's Great Lakes Water Quality Guidance. Under CERCLA, hexachlorobutadiene is designated a hazardous substance, and releases greater than or equal to 1 pound must be reported to the National Response Center. Under TSCA, manufacturers of this chemical must report to EPA preliminary assessment information concerned with production, use, and exposure (40 CFR 712.30). EPA's Health and Safety Data reporting Rule, promulgated under Section 8(d) of TSCA, requires manufacturers, importers, and processors to submit to EPA copies and lists of unpublished health and safety studies (40 CFR 716.120). Waste streams containing hexachlorobutadiene are subject to RCRA hazardous waste regulations (40 CFR 261.33). Incineration is the preferred method of disposal due to its greater than 99.9% destruction efficiency.

2.8 HEXACHLOROCYCLOHEXANE

Current Status: Registered pesticide (including lindane)
Hexachlorocyclohexane (HCH) [CAS Registry Number 608-73-1] has four major isomers, -HCH, -HCH, -HCH, and -HCH. Technical grade HCH is a mixture of all of the isomers. Lindane is the gamma isomer, -HCH, at least 99.5% pure. None of the isomers are naturally occurring substances.

Sources
HCH is not produced in the U.S. but is imported for use as a formulation component. HCH is used as an insecticide on fruit and vegetable crops, ornamentals, tobacco, greenhouse vegetables, and forestry (including Christmas tree treatment). It is also used in homes (e.g., for dog dips, house sprays, and shelf paper), commercial food or feed storage areas and containers, farms, and wood and wood structure sites. HCH is used medically in lotions, creams, and shampoos for the treatment of lice and scabies. A Notice of Intent to Cancel Pesticide Products Containing -HCH was issued by EPA in October 1983 and prohibited the use of -HCH for purposes involving direct aquatic application; it also restricted certain applications on livestock, structures, and domestic pets. In November 1993, EPA issued a Notice of Receipt of a Request for Amendments to Delete Uses for lindane, 99.5% technical HCH, and dust concentrate, to delete from the pesticide label most uses of lindane for agricultural crops and applications on animals and humans.

Releases and Environmental Levels
HCH is found in air, surface water, ground water, soil, sediment, fish, wildlife, food, and humans. The largest source of HCH release to air was the historical application of the pesticide lindane on agricultural lands. Current emissions result from the formulation of HCH in the U.S. and volatilization from treated soils and plants. Releases reported to TRI in 1991 indicated that 99% of the total 567 pounds of -HCH released to the environment involved air emissions from manufacturing and processing facilities. HCH is also found in surface water in many areas of the U.S. In a monitoring study conducted in 1980-1981 in the Niagara River near Lake Ontario, -HCH was detected in 99% of samples at a mean concentration of 2.1 ppt. A study in 1988 reported the mean annual loading of -HCH in urban storm water runoff to the Canadian Great Lakes Basin at 4.1 kg/yr. According to data in EPA's STORET database collected from 1978-1987, -HCH was detected in 33% of suspended sediment samples collected from the Niagara River at a mean concentration of 2 ppb.

Toxicity and Exposure
HCH has been classified as a probable human carcinogen in the U.S. Environmental Protection Agency's Integrated Risk Information System (IRIS). The major route of exposure for humans is through ingestion of plants, animals, and animal products containing HCH. Humans are also exposed through the use of consumer products and medications containing -HCH. Most exposures occur through misuse or accidental ingestion of products. Farm animals may be exposed through feed, air, water, or dermal application. The mean dietary intake of -HCH was estimated in FDA's Total Diet Analyses in 1988 to be 0.8 ng/kg bodyweight per day for 6-11 month-old infants, 1.4 for 14-16 year-old males, and 0.9 for 60-65 year-old females. A review of data from the National Human Adipose Tissue Survey (NHATS) available from 1970-1983 showed a decrease in the national median level but continued detection of -HCH in nearly 100% of the population. All isomers of HCH have been detected in the blood serum and adipose tissue of workers occupationally exposed to HCH in pesticide application. The exposure of the general population to HCH is limited due to regulations restricting its use.

Regulations
HCH is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). It has also been listed as a Bioaccummulative Chemical of Concern in EPA's Great Lakes Water Quality Guidance. HCH is included in the National Health and Nutrition Examination Survey (NHANES) IV, proposed National Study of Chemical Residues in Fish, IADN monitoring, the Great Waters Program, and Great Lakes Lakewide Management Plans, and has been recommended for use restrictions in the UN ECE Convention on Long-Range Transboundary Air Pollution (LRTAP) protocol.

2.9 4,4'-METHYLENEBIS(2-CHLOROANILINE)

Current Status: Commercially produced

Sources
4,4'-Methylenebis(2-chloroaniline) (MBOCA) [CAS Registry Number 101-14-4] is a commercially produced, man-made chemical. Although MBOCA was manufactured in the U.S. beginning in 1956, production was reported to have ceased in 1982, and all MBOCA used in the U.S. is imported. Approximately 2 million pounds of MBOCA were imported to the U.S. in 1991, primarily from Japan. MBOCA is used as a curing agent for isocyanate polymers and polyurethanes, which are used in the manufacture of boots and shoes, cameras, computers, reproducing equipment, home appliances, gun mounts, radar systems, jet engine turbine blades, and in nuclear submarines, missiles, and electric components.

Releases and Environmental Levels
Release of MBOCA to the environment is primarily through exhaust emissions from facilities that use it as a curing agent in the manufacture of polymers. Total releases of MBOCA to the atmosphere reported to TRI in 1991 were 1,362 pounds, with no discharges reported to surface water or to land. A specialty chemical manufacturing plant that produced MBOCA in the 1970s was found to have released significant quantities in its waste water; however, ground water contamination was not thought to have occurred. MBOCA levels in soil as high as 1,146 ppm have been detected in soil at a facility using MBOCA. Lesser concentrations were found in soil samples from residences adjacent to the site. Plants grown in MBOCA-contaminated soil have been found to contain MBOCA in the roots. MBOCA is included in the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
MBOCA is a suspected human carcinogen. NIOSH recommends that MBOCA be regulated as a potential human carcinogen. A vacated 1989 OSHA Permissible Exposure Limit (0.02 ppm) is still enforced in some states. Dermal absorption by workers occupationally exposed to MBOCA may be the most important exposure pathway. MBOCA is commonly found in the urine of humans exposed to the compound in the plastic industry. Engineering controls and protective clothing have been shown to decrease exposure levels. Indirect exposure also occurs through people occupationally exposed to MBOCA (e.g., family members of MBOCA-exposed workers). The general population is not likely to be exposed to MBOCA unless they live in a contaminated area (e.g., industrial sites) or consume root crops grown in MBOCA-contaminated soil.

Regulations
Releases of MBOCA are reported to TRI. MBOCA is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). Under CERCLA, MBOCA is designated a hazardous substance, and releases greater than or equal to 10 pounds must be reported to the National Response Center. Under RCRA, when MBOCA as a commercial chemical product or manufacturing chemical intermediate, or an off-specification commercial chemical product or a manufacturing chemical intermediate, becomes a waste, it must be managed according to Federal and/or State hazardous waste regulations (40 CFR 261.33).

2.10 PENTACHLOROBENZENE

Current Status: Commercial uses; inadvertent by-product

Sources
Pentachlorobenzene [CAS Registry Number 608-93-5] can be produced by the degradation of other organochlorine compounds, such as lindane and hexachlorobenzene. It has been suggested that pentachlorobenzene is a contaminant of hexachlorobenzene. Pentachlorobenzene is used as a starting reagent in the manufacture of the fungicide quintozene (pentachloronitrobenzene), and is a technical impurity of this pesticide. Other possible sources of chlorinated benzene contamination in the environment include use as chemical intermediates, as solvents in the manufacture of dyes, as lubricants and pesticides, and as transformer oils. Pentachlorobenzene is also produced in the combustion of plastics and chlorinated waste. Pentachlorobenzene was reported at concentrations of 95 and 300 ppb in the ash of municipal waste incinerators in the U.S. in 1990.

Releases and Environmental Levels
In 1982, pentachlorobenzene was reported in the drinking water of three cities in the Lake Ontario vicinity at 0.03-0.05 ppt. Pentachlorobenzene was detected in all 104 samples collected from 1981-1983 in the Niagara River at concentrations of 0.34-6.4 ppt and an average concentration of 1.1 ppt. Pentachlorobenzene was reportedly identified but not quantified in all 5 Great Lakes in 1984. In studies from the early 1980s, pentachlorobenzene was detected in 92% of sediment samples from Lake Superior (0-0.3 ppb, 0.1 ppb avg), 100% of the samples from Lake Huron (0.2-3.0 ppb, 1 ppb avg), 100% of the samples from Lake Erie (0.3-3 ppb, 1 ppb avg), 100% of the samples from Lake Ontario (9-320 ppb, 97 ppb avg), and in 96% of suspended sediment samples from the Niagara River at an average concentration of 58 ppb.

Pentachlorobenzene was detected in composite samples of sedentary fish from 8 of 16 sites at Lake Superior and Lake Huron tributaries sampled in the fall of 1983. The concentration on a fat basis of chemical found in the composite sample of carp from the Flint River, Michigan, was 8.9 ppb, 110 ppb in the composite sample from Saginaw Bay, Michigan, 11 ppb in the sample from the Ausable River, 21 and 16 ppb in the samples from two Chippewa River sites, 73 ppb in one of the samples from Saginaw Bay, and 49 ppb and 120 in the samples from two Saginaw River sites, Michigan. Pentachlorobenzene is included in the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
Pentachlorobenzene is not classifiable as to human carcinogenicity. The general population may be exposed to pentachlorobenzene via inhalation of ambient air and ingestion of food and drinking water. Occupational exposure to pentachlorobenzene may occur through inhalation and dermal contact at workplaces where pentachlorobenzene is produced or used. Exposure may also arise in occupations where the pesticide quintozene is produced and used. In human adipose tissue samples, pentachlorobenzene was detected, at a 1.9 ppb detection limit, but not quantified, in patients from six Ontario cities; pentachlorobenzene was not detected in the tissue of patients from Toronto. A 1987 report of a survey of human milk from the general and indigenous (Canadian Indian and Inuit mothers) population of Canada found pentachlorobenzene residues in 17% of 18 indigenous population samples at an average concentration of 2 ppb (milkfat basis) and in 97% of the general population (number of samples not reported) at an average concentration of 3 ppb (milkfat basis). Pentachlorobenzene was detected in 2 percent of all food products sampled in the U.S. between 1982-1984 and 1 percent of food products sampled between 1984-1986. Pentachlorobenzene was reported in peanut butter samples at an average concentration of 16 ppb (range 1.8-62 ppb).

Regulations
Pentachlorobenzene is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). It has also been listed as a Bioaccummulative Chemical of Concern in EPA's Great Lakes Water Quality Guidance. Under CERCLA, pentachlorobenzene is designated a hazardous substance, and releases greater than or equal to 10 pounds must be reported to the National Response Center. Under section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule which requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies (40 CFR 716.120). Pentachlorobenzene is included on this list. Hazardous waste streams containing pentachlorobenzene are subject to RCRA requirements (40 CFR 261.33) and must be managed according to Federal and/or State hazardous waste regulations.

2.11 PENTACHLOROPHENOL

Current Status: Commercially produced wood preservative, restricted-use pesticide

Sources
Currently the predominant use of pentachlorophenol (PCP) [CAS Registry Number 87-86-5] is as a wood preservative for the treatment of utility poles. PCP is also used in non-wood, manufactured pesticide products. However, as a restricted-use pesticide, it is no longer used in the wood treatment of products for new homes or agricultural buildings, and current releases are expected to be much less than historical releases.

Releases and Environmental Levels
PCP was once widely used as a biocide in the U.S. and is found in all environmental media as a result. PCP is released to air via volatilization from PCP-treated wood products. PCP emitted during production is considered insignificant and is restricted to one manufacturing facility. In the past, PCP was released to the atmosphere, surface waters, and waste water treatment plants from industries using it in cooling towers and in leather tanning and textile factories. PCP is no longer commonly used in these applications. The chlorination of phenolic compounds during water treatment may release PCP to water. Some pesticides or components of pesticides, namely lindane, hexachlorobenzene, pentachlorobenzene, and pentachloronitrobenzene, are metabolized to PCP in the environment. PCP is released to soil through spills at industrial facilities, hazardous waste sites, and leaching from treated wood products. Sludge solids from wood-treatment facilities may also contain PCP. PCP is included in the Great Lakes Regional Air Toxic Emissions Inventory Project and the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
Based on sufficient evidence of carcinogenicity in animals, PCP is classified as a probable human carcinogen. NIOSH has determined that PCP is immediately dangerous to life or health at a concentration of 2.5 mg/m³. OSHA has set a Permissible Exposure Limit for PCP (0.5 mg/m³) for an 8-hour workday. Human exposure occurs via inhalation of indoor air from PCP used to treat wood products, ingestion of contaminated food or water, and contact with PCP-treated wood products. PCP is classified by the FDA as an indirect food additive for use only as a component of adhesives (21 CFR 175.105).

Regulations
Releases of PCP are reported to TRI. PCP is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA), and standards of performance are required for equipment leaks of volatile organic compounds (VOCs) in the Synthetic Organic Chemical Manufacturing Industry (SOCMI), which produces chlorophenols (40 CFR 60.489). PCP is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). It is also designated as a hazardous substance under section 311(b)(2)(A) of the Federal Water Pollution Control Act. The ambient water quality criterion level for PCP in water is 30µg/L.

Under CERCLA, PCP is designated a hazardous substance, and releases greater than or equal to 10 pounds must be reported to the National Response Center. Under RCRA regulations, PCP must be managed as a hazardous waste, if so characterized, and discarded unused formulations containing tri-, tetra-, or pentachlorophenol or discarded unused formulations containing compounds derived from these chlorophenols are classified as a hazardous waste from a nonspecific source and must be managed according to Federal and/or State hazardous waste regulations. PCP meets the criteria of concern for oncogenicity, mutagenicity, and teratogenicity under FIFRA, and several registered uses have been canceled (e.g., PCP uses in cooling towers, pulp paper mills, and oil wells).

2.12 TETRACHLOROBENZENE (1,2,3,4- AND 1,2,4,5)

Current Status: Commercially produced and used as a dielectric fluid and organic intermediate

Sources
The major use of 1,2,3,4-tetrachlorobenzene [CAS Registry Number 634-66-2] is as a component of dielectric fluids and as a chemical intermediate in the synthesis of pentachloronitrobenzene. 1,2,4,5-Tetrachlorobenzene [CAS Registry Number 95-94-3] was formerly produced and used as an insecticide and intermediate in the production of herbicides and defoliants. Tetrachlorobenzene is a degradation byproduct of pentachlorobenzene and hexachlorobenzene and therefore may enter the environment as a result of the degradation of these compounds.

Releases and Environmental Levels
Release to the environment may occur through various waste streams. In 1982, 1,2,4,5-tetrachlorobenzene concentrations of 0.3-2 ng/L (1.2 ng/L avg) were reported in waste water effluents from four treatment plants discharging into Lake Ontario and the Grand River. 1,2,4,5-Tetrachlorobenzene was identified but not quantified in pulp mill effluents in Canada in 1988. Combined tetrachlorobenzene isomers were detected in 1985 at concentrations of 29 and 57µg/m³ in the effluent of municipal refuse incinerators located in Virginia and Ohio, respectively. In 1990, 1,2,4,5-tetrachlorobenzene was reported at concentrations of 450 and 100 ppb in the ash of municipal waste incinerators in the U.S.

Tetrachlorobenzene has been detected in air, soil, sediment, water, and biota. In 1992, 1,2,4,5- and 1,2,3,4-tetrachlorobenzene were reported in suburban air in Michigan at concentrations of 22-30 pg/m³ and 40-53 pg/m³, respectively. Soil samples taken from Niagara Falls, New York in the early 1980s contained 1,2,3,4-tetrachlorobenzene at mean concentrations of 940 and 1,340 pg/g. In 1988, detections of 1,2,3,4-tetrachlorobenzene were reported in sediment (32 ng/g) and suspended particulate matter (15 ng/g) in Lake Ontario. Tetrachlorobenzenes were detected in water from 9 of 14 stations in Lake Ontario sampled in October 1983 at concentrations ranging from 0.009-0.322 ng/L with an average of 0.064 ng/L. The concentrations of 1,2,4,5-tetrachlorobenzene detected in composite samples of carp collected in the fall of 1983 were 150 ppb in samples from Saginaw Bay, Michigan, and 66-74 ppm in samples from the Saginaw River, Michigan. 1,2,3,4-Tetrachlorobenzene was detected in trout from the Great Lakes at concentrations of 0.3-12 ng/g and in trout near the mouth of the Niagara River in Lake Ontario at a concentration of 4.3 ng/g (dry weight). The potential for bioconcentration in aquatic organisms is considered high. Tetrachlorobenzene is included in the proposed National Study of Chemical Residues in Fish.

Toxicity and Exposure
Occupational exposure may occur through inhalation and dermal contact at workplaces where 1,2,3,4-tetrachlorobenzene is produced or used. The general population may be exposed to 1,2,3,4-tetrachlorobenzene via inhalation of ambient air and ingestion of food and drinking water. The World Health Organization (WHO) estimates the average daily intake of all tetrachlorobenzene isomers for humans is less than 0.1 ng/kg body weight.

Regulations
1,2,4,5-Tetrachlorobenzene is designated a toxic pollutant under the Clean Water Act (CWA) and, as such, is subject to effluent limitations (40 CFR 401.15). Under CERCLA, 1,2,4,5-tetrachlorobenzene is designated a hazardous substance, and releases greater than or equal to 5,000 pounds must be reported to the National Response Center. Under section 8(d) of TSCA, EPA promulgated a model Health and Safety Data Reporting Rule which requires manufacturers, importers, and processors of listed chemical substances and mixtures to submit to EPA copies and lists of unpublished health and safety studies (40 CFR 716.120). 1,2,3,4-Tetrachlorobenzene and 1,2,4,5-tetrachlorobenzene are included on this list. Tetrachlorobenzene has also been listed as a Bioaccummulative Chemical of Concern in EPA's Great Lakes Water Quality Guidance.

2.13 TRIBUTYL TIN

Current Status: Commercially produced

Sources
Tributyl tin [CAS Registry Number: 56-35-9] is one of several man-made organotin compounds with various industrial uses. Tri-substituted organotins find uses as biocides in agriculture and industry. Tributyl tin may be used as an anti-fouling agent in marine paints within the limits set by the Organotin Antifouling Paints Control Act of 1988, which restricts the release rate of organotin paints used on ships in the U.S. Bis(tributyltin)oxide is used as a preservative for wood products, leather, ropes, fabrics, and paper. Tributyltin hydride may be used as a reducing agent for the conversion of alkyl halides to hydrocarbons and as a synthetic intermediate for other butyl tin compounds.

Releases and Environmental Levels
Data on industrial releases of tributyl tin could not be obtained, as tin and tin compounds are not required to be reported to TRI. Tributyl tin may be released to the environment (air, water, and soil) as a result of its production and use in agriculture and as an antifouling coating on ships. Organotin compounds have been detected in Lake Michigan sediments and in the lake water at concentrations of 10-1600 ng/L. The volatilization of tributyl tin from natural waters is not expected to be a significant process, and tributyl tin is not expected to adsorb to soil. Bioconcentration of tributyl tin in aquatic organisms is also not expected to be an important process, although tin in every form can be taken up by marine organisms, and concentrations can reach a few mg/kg. Tributyl tin, especially release to water from antifouling paints, is a concern due to its toxicity to aquatic life. Concentrations in harbor areas have been reported to range from not detected to 0.8µg/L.

Toxicity and Exposure
Organic tin compounds are potent central nervous system toxins as well as skin and eye irritants. Human exposure pathways for organotin compounds include inhalation, skin absorption, ingestion, and skin and/or eye contact. NIOSH has set a recommended 10-hour time-weighted average for organic tin compounds of 0.1 mg/m³. OSHA has set a Permissible Exposure Limit for organic tin compounds (0.1 mg/m³) for an 8-hour workday.

2.14 POLYCYCLIC AROMATIC HYDROCARBONS (PAHS)

Current Status: Primarily by-products of incomplete combustion; acenaphthene, acenaphthylene, and anthracene are produced commercially

Polycyclic aromatic hydrocarbons (PAHs) are a group of chemicals that generally occur as mixtures formed as a result of incomplete combustion. The physical and chemical properties of PAHs are not all alike, nor are their health effects. Nonetheless, because PAHs typically occur as a mixture, they are usually observed as a class of 7 PAHs of similar molecular weight (e.g., benzo(a)anthracene, benzo(a)pyrene) or as a broader class of 16 PAHs (e.g., anthracene, perylene, phenanthrene).

Sources
The primary source of PAH air emissions is incomplete combustion of wood or fuel. Sources include motor vehicles, non-road vehicles and equipment, residential wood combustion, industrial and commercial combustion, coke ovens, cigarette smoke, primary aluminum production, petroleum catalytic cracking, and charcoal broiled foods. PAHs also result from volcanoes, wildfires, and scrap tire fires. Stationary sources are estimated to account for 80% of total PAH emissions. Mobile sources (e.g., vehicle exhaust and emissions from gasoline and diesel powered engines) are major sources in urban areas. The 1998 Great Lakes Regional Air Toxic Emissions Inventory reports 1993 estimated PAH emissions as follows: residential wood combustion (95%) and gasoline service stations (5%).

Three PAHs, acenaphthene, acenaphthylene, and anthracene, are produced commercially in the U.S., although others may be produced in small quantities for research. Anthracene is manufactured for use in the production of dyes and synthetic fibers, in smoke screens and organic semiconductor research, as a diluent for wood preservatives, and in the synthesis of the chemotherapeutic agent Amsacrine.

Releases and Environmental Levels
Emission estimates for sources of 7 PAHs and 16 PAHs are provided in the 1990 Emissions Inventory of Clean Air Act (CAA) Section 112(c)(6) Pollutants and are expected to be included in the draft 1993 National Toxics Inventory due to be released by EPA in Fall 1999. Although emissions of PAHs from natural and man-made sources are largely to the atmosphere, PAHs may accumulate in surface water from atmospheric deposition and from discharge of industrial effluents, municipal waste water, urban runoff, and improper disposal of used motor oil. PAHs in surface water may volatilize to the atmosphere or accumulate in sediment. Sediments are major sinks of PAHs. PAHs in air may be transported long distances. The release of PAHs from anthropogenic combustion sources has resulted in increasing soil concentrations over the past 100-150 years. In general, soil concentrations are higher in urban areas than in rural areas. PAHs have been identified in 600 of 1,408 NPL hazardous waste sites.

Toxicity and Exposure
The class of 7 PAHs of similar molecular weight have been identified as animal carcinogens by the IARC. Indoor air contaminated with PAHs by tobacco smoke, space heaters, and cooking appliances is a significant source of PAHs. Hazardous waste sites, former manufactured gas plants, drinking water, contaminated food, and skin contact with soot or tar are additional sources of exposure. Foods that are grilled or smoked and foods obtained from polluted environments tend to have elevated PAH levels. Smokers and persons exposed to sidestream smoke may experience exposure levels significantly higher than that of the general population. PAHs are contained in coal tar preparations used to treat skin disorders. PAHs accumulate in terrestrial and aquatic life but can be metabolized by many plants and animals. Food chain uptake is not considered a major route of exposure. The benzene-soluble fraction of coal tar pitch volatiles and mineral oil mist, which contain several PAH compounds, are regulated by OSHA.

Regulations
PAHs are not consistently regulated as a group. Releases of polycyclic aromatic compounds are reported to TRI. Polycyclic organic matter, which includes PAHs, is listed as a hazardous air pollutant (HAP) under the Clean Air Act (CAA). PAHs are listed as a priority pollutant under the Clean Water Act (CWA) and are regulated by Clean Water Effluent Guidelines. Under CERCLA, specific quantities of individual PAHs must be reported to the National Response Center. Under RCRA, PAHs must be managed as hazardous wastes when they are discarded commercial chemical products, off-specification species, container residues, and spill residues. PAHs are included in the proposed National Study of Chemical Residues in Fish, the Great Lakes Regional Air Toxic Emissions Inventory Project, and the UN ECE Convention on Long-Range Transboundary Air Pollution (LRTAP) protocol.

Table 3. Glossary of Terms and Acronyms

ATSDR Agency for Toxic Substances and Disease Registry Toxicological Profiles

BCC Bioaccummulative Chemical of Concern

BRS RCRA Biennial Reporting System

CAA Clean Air Act

CAS Chemical Abstracts Service

CEC Commission for Environmental Cooperation

CERCLA Comprehensive Environmental Response, Compensation, and Liability Act

CFR Code of Federal Regulations

COA Canada-Ontario Agreement

CWA Clean Water Act

DCB Dichlorobenzidine

FDA Food and Drug Administration

FIFRA Federal Insecticide, Fungicide, and Rodenticide Act

HAP Hazardous Air Pollutant

HCH Hexachlorocyclohexane

HSDB Hazardous Substances Databank

IADN Integrated Atmospheric Deposition Network

IARC International Agency for Research on Cancer

IJC International Joint Commission

LaMPs Great Lakes Lakewide Management Plans

LRTAP Convention on Long-Range Transboundary Air Pollution

MBOCA 4,4'-Methylenebis(2-chloroaniline)

NESHAP National Emissions Standard for Hazardous Air Pollutants (HAPs)

NHANES National Health and Nutrition Examination Surveys

NIOSH National Institute for Occupational Safety and Health

NPL National Priority List

OSHA Occupational Safety and Health Administration

PAHs Polycyclic Aromatic Hydrocarbons

PBT Persistent, Bioaccummulative and Toxic

PCP Pentachlorophenol

POPs Persistent Organic Pollutants

ppb parts per billion

ppm parts per million

RAPIDS Regional Air Pollutant Inventory Development System used in the Great Lakes Regional Air Toxic Emissions Inventory Project

RCRA Resource Conservation and Recovery Act

SOCMI Synthetic Organic Chemical Manufacturing Industry

Tier I Tier I chemical recommended analyte for National Study of Chemical Residues in Fish

Tier II Tier II chemical recommended analyte for National Study of Chemical Residues in Fish

TRI Toxics Release Inventory

TSCA Toxic Substances Control Act

UN ECE United Nations' Economic Commission for Europe

UNEP United Nations Environmental Program

3.0 REFERENCES

U.S. Department of Health and Human Services, Public Health Service (1999) Agency for Toxic Substances and Disease Registry Toxicological Profiles, CRC Press LLC.

United States Environmental Protection Agency, "Great Lakes Regional Air Toxic Emission Inventory Report: Initial Inventory Using 1993 Data," Region 5, U.S. Environmental Protection Agency, August 1998.

U.S. National Library of Medicine (1999) Hazardous Substances Data Bank (HSDB), Issue: 99-3 (August, 1999).

Web sites

Great Lakes Binational Toxics Strategy

GLBTS Links

DRAFT Report on Level II Substances in the Binational Toxics Strategy

A U.S. Perspective

1.0 BACKGROUND

2.0 LEVEL 2 SUBSTANCES

3.0 REFERENCES

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