Canadian Environmental Protection Act: Priority Substances List: Chromium and its compounds
Canadian Environmental Protection Act
Priority Substances List Assessment Report
Government of Canada
Environment Canada
Health Canada
Gouvernement du Canada Environnement
Canada Santé Canada
Chromium and its Compounds
Synopsis
Chromium is a naturally occurring metal that is present principally in the trivalent or hexavalent forms in small amounts throughout the Canadian environment. Chromium ore is not currently produced in Canada; however, approximately 74 000 tonnes (gross weight) of various chromium-containing materials were imported into Canada in 1991. Chromium is used in a wide variety of industrial applications in Canada including the production of stainless and heatresistant steels, refractory products such as bricks and mortars, and in pigments, metal finishing, leather tanning, and wood preservatives. Both trivalent and hexavalent forms of chromium are released into the environment in Canada as a result of these industrial uses, as well as from the production and combustion of fossil fuels, and the smelting and refining of nonferrous base metals.
Typical (median or mean) concentrations of dissolved hexavalent chromium in Lake Ontario and Lake Brie, as well as in rivers and streams in parts of British Columbia, Alberta, Ontario, and Quebec are likely 5 to 15 times greater than the effects threshold estimated for the most sensitive aquatic species identified. Furthermore, average concentrations of chromium in soils contaminated with dissolved hexavalent chromium at several Canadian wood preservation facilities are 19 to 1700 times greater than levels of hexavalent chromium reported to harm some plants and microbial communities. Although trivalent chromium is likely the dominant chromium species in most sediments, soils, and biological tissues, there was insufficient information to determine whether organisms are adversely affected by exposure to trivalent chromium in Canada.
Chromium (in trivalent and hexavalent forms) occurs at low concentrations, primarily in particulate form in the atmosphere, and consequently it is unlikely to have a marked influence on the earth's solar radiation balance. Trivalent chromium is not oxidized by ozone and therefore cannot be linked to any ozone-depleting reactions in the atmosphere. As such, chromium is not expected to contribute significantly to global warming or depletion of stratospheric ozone. Based on an estimation of the average total daily intake of chromium (total) from air, drinking water, food, and soil for various age groups of the general population, food is likely the most significant source of human exposure in Canada. Based on the weight of evidence of carcinogenicity in occupationally exposed populations, the group of hexavalent chromium compounds as a whole (since available data do not permit an assessment of individual compounds within the group) is classified as "Carcinogenic to Humans", i.e., as substances for which there is believed to be some chance of adverse health effects at any level of exposure. For such substances, estimated exposure is compared to quantitative estimates of carcinogenic potency to characterize risk and provide guidance for further action, i.e., analysis of options to reduce exposure. For hexavalent chromium, such a comparison suggests that the priority for analysis of options to reduce exposure would be moderate to high. In addition, hexavalent chromium may induce skin sensitivity in a small portion of the general population.
Trivalent chromium is considered to be an essential element in human nutrition. Estimated average daily intake of total chromium does not exceed the recommended daily intake for trivalent chromium. Levels of trivalent chromium that are demonstrated to cause adverse effects in limited studies in experimental animals greatly exceed typical concentrations of total chromium in relevant environmental media in Canada. Based on these considerations, it has been concluded that dissolved and soluble forms of hexavalent chromium are entering or may enter the environment in a quantity or concentration or under conditions that are having or may have a harmful effect on the environment. There are insufficient data to determine if trivalent forms of chromium are entering or may enter the environment in a quantity or concentration or under conditions that are having or may have a harmful effect on the environment. It has been concluded that neither hexavalent nor trivalent forms of chromium are entering or may enter the environment in a quantity or concentration or under conditions that constitute or that may constitute a danger to the environment on which human life depends. It has also been concluded that the group of hexavalent chromium compounds as a whole is entering the environment in a quantity or concentration or under conditions that may constitute a danger in Canada to human life or health, while the group of trivalent chromium compounds as a whole is not entering the environment in a quantity or concentration or under conditions that may constitute a danger in Canada to human life or health.