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2. Nickel-containing substances can be grouped into five main classes based on their physicochemical characteristics: nickel carbonyl (gas) metallic nickel (e.g. elemental nickel nickel-containing alloys) oxidic nickel (e.g. nickel oxides hydroxides silicates carbonates complex nickel oxides) sulfidic nickel (e.g. nickel sulfide nickel subsulfide) and water-soluble nickel compounds (e.g. nickel sulfate hexahydrate nickel chloride hexahydrate). Exposures during nickel refining may contain several of these nickel species depending on the type of process used.
3. Comparative carcinogenic effects of nickel subsulfide, nickel oxide, or nickel sulfate hexahydrate on chronic exposures in the Iung;Dunnick JK;Cancer Res,1995
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5. ACGIH
. Threshold Limit Values and Biological Exposure Indices for Chemical Substances and Physical Agents. Cincinnati OH:American Conference of Governmental Industrial Hygienists 1998;51.