A determination of the health effects of metallic nickel is based mainly upon epidemiological studies of over 40,000 workers from various nickel-using industry sectors (nickel alloy manufacturing, stainless steel manufacturing, and the manufacturing of barrier material for use in uranium enrichment ). These workers were examined for evidence of carcinogenic risk due to exposure to metallic nickel and, in some instances, accompanying oxidic nickel compounds and nickel alloys. No nickel-related excess respiratory cancer risks have been found in any of these workers. Animal data on carcinogenicity are in agreement with the human data. A recent regulatory-compliant study on the inhalation of metallic nickel powder was negative for carcinogenicity. However, at levels above 0.1 mg Ni/m3, chronic respiratory toxicity was observed in the animals.
Data relating to respiratory effects associated with short-term exposure to metallic nickel are very limited. One case report of a fatality has been recorded in a man spraying nickel using a thermal arc process. However, the relevance of the case is questionable since the reported expo- sure to total nickel was extremely high (382 mg Ni/m3). Nevertheless, special precautions to reduce inhalation exposure to fine and ultrafine powders should be taken.
Collectively, animal and human data present a mixed picture with respect to the potential role that metallic nickel may play in non-malignant respiratory disease. A few cases of asthma or fibrosis have been reported in humans and certain inflammatory effects have been noted in animals. However, the overall literature shows that past exposures to metallic nickel have not resulted in excess mortality from such diseases. Additional studies on such effects would be useful.
Skin sensitization to nickel metal can occur wherever there is leaching of nickel ions from articles containing nickel onto exposed skin. Occupational exposures involving direct and prolonged skin contact with metallic nickel may elicit cutaneous allergy (allergic contact dermatitis) in nickel-sensitized workers. However, nickel dermatitis occurs mainly as the result of non-occupational exposures.