Hexachlorobenzene

CAS number:
118-74-1

Date circular:
12/12/2008

Chemical name: Benzene, hexachloro-

Final regulatory action has been taken for the category: Industrial

Final regulatory action: The chemical is Severely Restricted

Use or uses prohibited by the final regulatory action:

The Regulations prohibit the manufacture, use, sale, offer for sale or import of HCB, with the exceptions listed below:

Use or uses that remain allowed:

The Regulations do not apply HCB that is:

·contained in a hazardous waste, hazardous recyclable material or non-hazardous waste;

·contained in a control product (e.g., pesticide);

·present as a contaminant in a chemical feedstock used in a process from which there are no releases of the substance and provided that the substance is destroyed or completely converted in that process to a substance that is not a toxic substance listed in the Regulations; or,

·used in a laboratory for analysis; in scientific research; or, as a laboratory analytical standard.

In addition, the Regulations do not apply in respect of the manufacture, use, sale, offering for sale or import of HCB if it is present, incidentally or not, in a mixture or product listed below if the concentration of HCB in the mixture or product is below the specified limit:

·Trichloroethylene, Concentration limit = 20 ppb

·Tetrachloroethylene, Concentration limit = 20 ppb

·Tetrachloromethane, Concentration limit = 20 ppb

·Magnesium salt (by-product from the magnesium industry), Concentration limit = 20 ppb

·Magnesium sludge (by-product from the magnesium industry), Concentration limit = 20 ppb

·Hydrochloric acid (by-product), Concentration limit = 20 ppb

·Ferric chloride, Concentration limit = 20 ppb

·Ferrous chloride, Concentration limit = 20 ppb

The Regulations also establish a permit system that provides a mechanism for temporarily exempting certain applications of a substance listed in the Regulations. A permit may be granted only if the Minister of the Environment is satisfied that there is no technically or economically feasible alternative or substitute available for the substance. In addition, the Minister must be satisfied that measures have been taken to minimize or eliminate any harmful effects of the substance on the environment and human health. Finally, the applicant must provide an implementation plan that identifies specific timelines for eliminating the substance. Each permit lasts for 12 months, and can be renewed only twice.

The final regulatory action was based on a risk or hazard evaluation: Yes

Summary of the final regulatory action:

Industrial: The Prohibition of Certain Toxic Substances Regulations, 2005 prohibit the manufacture, use, sale, offer for sale and import of toxic substances listed in Schedules 1 and 2 to the Regulations. HCB is found on Schedule 2, which lists substances that are subject to prohibitions related to concentration or use.

The reasons for the final regulatory action were relevant to: Human health and environment

Summary of known hazards and risks to human health:

Note that the information on the hazard and risk evaluation relates to the industrial regulatory action. No information is available on the hazard and risk evaluation conducted for the pesticide regulatory action.

The Canadian Environmental Protection Act (CEPA) requires the Ministers of the Environment and of Health to prepare and publish a Priority Substances List that identifies substances, including chemicals, groups of chemicals, effluents and wastes that may be harmful to the environment or constitute a danger to human health. HCB was placed on this list and was given priority for assessment to determine whether it is "toxic" under CEPA. As HCB was assessed under the original CEPA (CEPA was reviewed and updated in 1999), it was assessed against the definition for "toxic" as interpreted in section 11 of the 1988 Act, which stated:

"a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions

(a) having or that may have an immediate or long-term harmful effect on the environment;

(b) constituting or that may constitute a danger to the environment on which human life depends;

The assessment of whether HCB is "toxic," as interpreted in CEPA 1988, was based on the determination of whether it entered or likely entered the Canadian environment in a concentration or quantities or under conditions that could have lead to exposure of humans or other biota at levels that could cause adverse effects.

For the human health-related portion of the assessment, a background review was prepared under contract in February of 1990. For the period of 1983 to 1989, a literature survey was conducted by the contractor by searching a number of databases to identify toxicological data and data relevant to the estimation of exposure of the general population to HCB. Representatives of the Drinking Water Surveillance and of the Sport Fish Contaminant Monitoring Programs of Ontario were contacted for unpublished information. The Canadian Chemical Producers Association was consulted concerning relevant data for consideration.

Although much of the research on HCB was conducted outside of Canada, available Canadian data on sources, fate, levels and effects of HCB on the Canadian environment and human population were emphasized.

Review articles were consulted where considered appropriate; however, all original studies that formed the basis for the determination of "toxic" under CEPA were critically evaluated by staff of Health Canada (human exposure and effects on human health) and Environment Canada (entry, environmental exposure and effects).

Human Life or Health

Population Exposure

Based on the most representative concentrations of HCB in air, water, food and soil, and standard values for body weights and intakes of these environmental media, the mean daily intakes of HCB were estimated for various age classes of the general population (Table 4, attached). In addition, estimates were made for more highly exposed subgroups of the population, including recreational fishermen who consumed salmonids from Lake Ontario, and Inuit from the high Arctic who consumed large quantities of marine mammals. Exposure of populations in the vicinity of industrial sources may also have been greater than that for the general population, but the available data were considered inadequate as a basis for quantitative estimation. Since intakes vary considerably during the course of the lifespan and the critical toxicological effect is associated with long-term exposure to HCB, estimates of the average daily intake of HCB over a lifetime were also calculated based on these age-specific intakes.

Effects

HCB was classified in Group II (probably carcinogenic to man) of the classification scheme developed by the Bureau of Chemical Hazards for use in the derivation of the "Guidelines for Canadian Drinking Water Quality". Substances classified in Groups I and II on the basis of the weight of evidence of carcinogenicity are considered non-threshold toxicants, substances for which there is some probability of harm for the critical effect at any level of exposure. HCB was, therefore, considered to be "toxic" to human life or health.

This approach is consistent with the objective that exposure to non-threshold toxicants should be reduced wherever possible and obviates the need to establish an arbitrary de minimis level of risk for determination of "toxic" under the Act.

Overall Conclusion

The data presented indicated that HCB, at the concentrations found in Canada, had potential to cause adverse effects on the environment and on human life or health. Therefore, HCB was considered to be "toxic" to the environment and to human life or health.

Expected effect of the final regulatory action in relation to human health:

Sources addressed by the Industrial Regulations protect the health of Canadians and ecosystems by ensuring that future production, importation and the use of HCB is prohibited with very limited exemptions.

Note that sources of HCB emissions addressed by the Industrial Regulations are relatively small compared to the principal sources, identified as being the application of chlorinated pesticides containing HCB as a micro contaminant, and the incineration of wastes. Sources not addressed are subject to various non-regulatory initiatives contributing to the reduction of HCB releases.

Summary of known hazards and risks to the environment:

The Canadian Environmental Protection Act (CEPA) requires the Ministers of the Environment and of Health to prepare and publish a Priority Substances List that identifies substances, including chemicals, groups of chemicals, effluents and wastes that may be harmful to the environment or constitute a danger to human health. HCB was placed on this list and was given priority for assessment to determine whether it is toxic under CEPA. As HCB was assessed under the original CEPA (CEPA was reviewed and updated in 1999), it was assessed against the definition for toxic as interpreted in section 11 of the 1988 Act, which stated:

a substance is toxic if it is entering or may enter the environment in a quantity or concentration or under conditions

(a) having or that may have an immediate or long-term harmful effect on the environment;

(b) constituting or that may constitute a danger to the environment on which human life depends;

The assessment of whether HCB is toxic, as interpreted in CEPA 1988, was based on the determination of whether it entered or likely entered the Canadian environment in a concentration or quantities or under conditions that could lead to exposure of humans or other biota at levels that could cause adverse effects.

Data relevant to the environmental portions of the assessment were identified through searches of commercial and government databases. Additional information was identified in review documents. Relevant unpublished data were also acquired from the Canadian Wildlife Service. A background report on the fate and levels of HCB in the Canadian environment was prepared under contract.

Review articles were consulted where considered appropriate; however, all original studies that formed the basis for the determination of toxic under CEPA were critically evaluated by staff of Health Canada (human exposure and effects on human health) and Environment Canada (entry, environmental exposure and effects).

Environment

The highest concentrations of HCB were observed near point sources in the Great Lakes and connecting channels. Levels in air, water and forage fish from this area at the time the assessment was conducted had the potential to cause harmful effects to fish-eating mammals, such as mink. The available data on these levels further indicated that HCB ha the potential to cause reproductive impairment to predatory bird species across Canada, including the endangered peregrine falcon.

Conclusion

On the basis of the available data on levels of HCB in Canadian air, water and forage fish, and the potential effects of exposure at these levels on predatory birds and fish-eating mammals, HCB was considered to be "toxic" to the environment.

Environment on Which Human Life Depends

HCB absorbs infrared light at several wavelengths (7, 13 and 14 µm) characteristic of trace gases associated with global warming. Substances that absorb strongly between 7 and 13 µm act to absorb thermal radiation from the Earth's surface that would otherwise escape into space. HCB is, however, removed from the troposphere by photolysis (t_½� 80 days) and deposition to soil and water, and thus levels of HCB in the atmosphere at the time the assessment was conducted were low ( 0.2 ng/m³). HCB was, therefore, unlikely to have a significant impact on global warming.

In general, substances such as HCB with tropospheric sinks or removal processes (e.g., photolysis, deposition to soil or water) are not transported to the stratosphere. These processes, combined with the low levels of HCB in the troposphere, indicated that little, if any, HCB was expected to reach the stratosphere. HCB is, therefore, unlikely to be associated with stratospheric ozone depletion.

Conclusion

Therefore, on the basis of available data, HCB was not considered to be "toxic" to the environment on which human life depends.

Overall Conclusion

Expected effect of the final regulatory action in relation to the environment:

Date of entry into force of the final regulatory action: 15/05/2005