NICKEL AND ITS COMPOUNDS - EVALUATION OF RISKS TO HEALTH FROM ENVIRONMENTAL EXPOSURE IN CANADA

In this assessment of nickel as a Priority Substance under the Canadia n Environmental Protection Act, available data on exposure and potenti al health effects of various forms of nickel likely to be present in t he general environment were critically evaluated. Metallic nickel was considered to be ''unclassifiable with respect to carcinogenicity'', d ue to the limitations of identified studies, Concentrations of total n ickel in ambient air in Canada are more than 5,000 times less than lev els of metallic nickel which induced minimal effects in experimental a nimals. Each of oxidic, sulphidic and soluble nickel has been classifi ed as ''carcinogenic to humans'', based on the sufficient weight of ev idence of carcinogenicity in occupationally exposed populations. Based on comparison of concentrations of total nickel in air to the estimat ed potency of these forms of nickel to cause cancer (combined), the pr iority for analysis of options to reduce exposure in the general envir onment to oxidic, sulphidic and soluble nickel is considered to be mod erate to high, compared to that of other substances assessed in the Pr iority Substances Program. In addition, a Tolerable Daily Intake or Co ncentration for non-carcinogenic effects for soluble or oxidic nickel could be less than exposure in relevant environmental media in Canada. Available data also indicate that nickel (mostly soluble compounds) i nduces contact dermatitis in a proportion of the population.