Synopsis

This assessment of "nickel and its compounds" focuses on the forms of nickel most likely to be present in the environment, i.e., several forms of inorganic nickel. Nickel is a naturally occurring element that is ubiquitous in the environment principally in the divalent state. Approximately 197 000 tonnes (t) of nickel are currently produced per year in Canada, most of which is sold abroad. Nickel and its alloys are used in a wide variety of industrial applications for the automobile, shipbuilding, electrical, oil, food, and chemical industries. Nickel enters the Canadian freshwater and terrestrial (soil) environment as a result of natural weathering and erosion of geological materials, e.g., glacial overburden and bedrock. Nickel is also released into the environment in Canada as a result of human activities including mining, smelting, refining, alloy processing, scrap metal reprocessing, other metal operations, fuel combustion, and waste incineration.

The assessment of effects to the environment focused on aquatic biota and terrestrial plants since they are most likely to be affected by exposure to nickel in Canada. Comparison of reported effect levels to environmental concentrations indicates that dissolved and soluble forms of inorganic nickel likely cause harmful effects to sensitive pelagic organisms and terrestrial plants in the vicinity of major anthropogenic and natural sources. Nickel occurs at low concentrations in suspended particulate material in the atmosphere, has an atmospheric residence time of 5 to 8 days, and does not absorb infrared radiation. The only significant gaseous nickel compound, nickel carbonyl, degrades in air with a half-life of less that one minute. Consequently, inorganic forms of nickel are not expected to contribute to global warming or to the depletion of stratospheric ozone.

Based on the estimation of the average daily intake of nickel (total) from air, drinking water, food, and soil for various age groups in the general population, food is likely the most significant source of human exposure in Canada.

There was no evidence that occupational exposure to metallic nickel was associated with cancer in humans, although there is some limited evidence that metallic nickel may be carcinogenic in experimental animals exposed by routes less relevant to assessment of effects in humans. Concentrations of total nickel in ambient air in Canada, of which metallic nickel is believed to comprise only a small proportion, are more than 5000 times less than the levels that induced minimal effects in experimental animals.

Based principally on the sufficient weight of evidence of carcinogenicity in occupationally exposed human populations for the groups of compounds examined in a recent extensive epidemiological analysis and some limited supporting data on individual compounds in experimental animals, each of the groups, "oxidic" (including nickel oxide, nickel-copper oxide, nickel silicate oxides, and complex oxides), "sulphidic" (including nickel subsulphide), and "soluble" (primarily nickel sulphate and nickel chloride) nickel compounds has been classified as "Carcinogenic to Humans", i.e., substances for which there is believed to be some chance of adverse health effects at any level of exposure.

Available data were inadequate to address individual compounds within these groups. For such groups, where data permit, estimated exposure is compared to quantitative estimates of cancer potency to characterize risk and provide guidance for further action, i.e., analysis of options to reduce exposure, under CEPA. For "oxidic", "sulphidic", and "soluble" nickel compounds (combined), such a comparison suggests that the priority for analysis of options to reduce exposure would be moderate to high. Available data also indicate that nickel (mostly "soluble" compounds) induces contact dermatitis in a proportion of the population. Moreover, a Tolerable Daily Intake (TDI) for non-carcinogenic effects developed for "soluble" nickel compounds would be less than the estimated total intake of nickel for the Canadian population through ingestion. A Tolerable Daily Intake is the intake to which it is believed that a person can be exposed over a lifetime without deleterious effect.

Based on these considerations, it has been concluded that dissolved and soluble* forms of inorganic nickel 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 the substance "nickel and its compounds" does not or may not enter the environment in a quantity or concentration or under conditions that constitute or may constitute a danger to the environment on which human life depends. It has also been concluded that metallic nickel does not constitute a danger in Canada to human life or health, however, each of the groups, "oxidic" (including nickel oxide, nickel-copper oxide, nickel silicate oxides, and complex oxides),  sulphidic" (including nickel subsulphide), and "soluble" (primarily nickel sulphate and nickel chloride) nickel 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.