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Notice Concerning the Assessment of the Priority Substance Carbon DisulfidePriority Substances Assessment Program Under the Priority Substances List provisions of the Canadian Environmental Protection Act (CEPA), the Minister of the Environment and the Minister of Health are required to develop a list of substances that should be given priority for assessment to determine whether they are "toxic" or capable of becoming toxic as defined under section 11 of the Act. The responsibility for assessing priority substances is shared by Environment Canada and Health Canada. The purpose of the assessments is to determine if a substance is entering or may enter the environment in a quantity or concentration under conditions: (a) having or that may have an immediate or long-term harmful effect on the environment; or
(b) constituting or that may constitute a danger to the environment on which human life depends; or (c) constituting or that may constitute a danger in Canada to human life or health. Determining a substance to be CEPA "toxic" is therefore a function of its presence in the environment, the resulting exposure, and its inherent toxicity.
Draft Priority Substance Assessment Report for Carbon Disulfide
Available scientific information covering the physical and chemical properties, environmental entry, fate, exposure, and toxicity of carbon disulfide has been reviewed. A draft report assessing whether or not carbon disulfide is "toxic" or is capable of becoming toxic as defined in section 11 of CEPA has been prepared. The draft Assessment Report for carbon disulfide may be obtained from the Priority Substances List (PLS) Public Comment Web Page (www.ec.gc.ca/cceb1/eng/public/index_e.html) or from the Inquiry Centre, Environment Canada, Hull, Quebec K1A 0H3 (1-800-668-6767). Draft Assessment Report Summary for Carbon Disulfide Carbon disulfide is commercially produced in Canada, with annual production of about 3 kilotonnes. It is mainly used as a precursor in the manufacture of xanthates, which are used as flotation agents in mineral refinery processes. Releases into the environment from human activities occur primarily as a result of its production as a by-product in oil and gas processing in Canada. Additional industrial releases result from its use in the chemical industry and tire manufacturing. Virtually all anthropogenic and natural releases are to air. Carbon disulfide is also produced naturally by several types of soil, sediment and aquatic microorganisms, vegetation, forest and grass fires and volcanoes. Worldwide, at least 40 percent and possibly as much as 80 percent of releases are a result of natural or biogenic activity. Carbon disulfide is ubiquitous throughout the environment. It has been detected in air, water, sediment and soil; however, it is found primarily in air. The highest concentrations of carbon disulfide in Canadian air have been measured near industrial sources, in particular near natural gas processing plants and sites with sulfur-containing natural gas flares. Carbon disulfide is removed from the air primarily by reaction with hydroxyl radicals, resulting in a half-life of 1-2 weeks. This half-life in air makes it a candidate for long-range transport; however, it is rapidly diluted to natural background levels. Carbon disulfide is rapidly metabolized by organisms and does not bioconcentrate or biomagnify. As carbon disulfide is mainly released to and detected in air, this is a critical compartment in the assessment of risk to the environment. In situations where carbon disulfide-containing effluents are released to surface waters, biota in water may be exposed. Selected assessment endpoints are, therefore, terrestrial plants and animals and freshwater organisms. Carbon disulfide is of moderate to low toxicity to aquatic biota. Based on concentrations measured in air and surface water in Canada and on the Estimated No-Effects Values derived from experimental data for terrestrial and aquatic biota, it is unlikely that organisms are exposed to harmful levels of carbon disulfide in the Canadian ambient environment. Carbon disulfide is not likely to contribute significantly to depletion of stratospheric ozone, ground-level ozone formation or climate change. Available data upon which to base estimates of human exposure to carbon disulfide in Canada are extremely limited; however, air appears to be the major route of exposure for members of the general population. Airborne exposures are estimated to be elevated for populations in the vicinity of industrial point sources in Canada. Based on the results of epidemiological studies of workers exposed to carbon disulfide and supporting data from experiments conducted on animals, the nervous system appears to be the critical target for carbon disulfide-induced toxicity, manifested most often as reduced conduction velocity in the peripheral nerves and impaired performance in psychomotor testing. Other effects for which there is considerable weight of evidence in humans exposed to carbon disulfide include alterations in serum lipids and blood pressure that are associated with increased risk of heart disease, damage to the blood vessels of the retina and (with higher exposures) increased mortality from heart disease. The estimated mean airborne exposure to carbon disulfide for the general population, and for populations in the vicinity of point sources, is considerably less than a Tolerable Concentration derived on the basis of a benchmark concentration for reduced peroneal motor nerve conduction velocity in a population of viscose rayon workers exposed to carbon disulfide. A Tolerable Concentration is the level to which it is believed a person may be exposed daily over a lifetime without deleterious effect. Based on available data, it is proposed that carbon disulfide is not entering the environment in a quantity or concentration or under conditions having or that may have an immediate or long-term harmful effect on the environment; or constituting or that may constitute a danger to the environment on which human life depends; or constituting or that may constitute a danger in Canada to human life or health. Thus, it is proposed that carbon disulfide not be considered "toxic" as defined in section 11 of the Canadian Environmental Protection Act (CEPA) and that evaluation of options under CEPA to reduce exposure not be considered a priority at this time. However, this is based on current use patterns; thus, future releases of this compound should continue to be monitored to ensure that exposure does not increase to any significant extent. Public Comment Period Environment Canada and Health Canada are offering interested parties the opportunity to comment on the draft Priority Substances Assessment Reports. Any person may file, in writing, a submission within 60 days of publication of this notice presenting scientific evidence disagreeing with or supporting the assessments and the proposed conclusions presented in the draft Assessment Report for carbon disulfide. Submissions made in this regard, or any inquiries on this notice, may be sent to the attention of the PSL Assessment Program, Commercial Chemicals Evaluation Branch, Department of the Environment, Hull, Quebec K1A 0H3, (819) 953-4936 (Facsimile), or by electronic mail to the PSL Webmaster, PSL.LSIP@ec.gc.ca. Comments will not be responded to individually. All comments received will be considered, and the Assessment Report will be revised as necessary. Comments received after the comment period has ended will not be considered. A brief summary of public comments for each draft Assessment Report may be published on the Web page following the closure of the public comment period for each report. Please note, submitted comments will become a matter of public record and may be cited, with attribution to the author, by the Government of Canada. J. A. BUCCINI
Director
Commercial Chemicals
Evaluation Branch On behalf of the Minister of the Environment
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