NICKEL AND NICKEL COMPOUNDSNickel and nickel compounds were considered by previous IARC Working Groups in 1972, 1975, 1979, 1982, 1987, and 1989 (IARC, 1973, 1976, 1979, 1982, 1987, 1990). Since that time, new data have become available, these have been incorporated in the Monograph, and taken into consideration in the present evaluation.
1. Exposure Data
1.1 Identification of the agents
Synonyms, trade names, and molecular formulae for nickel, nickel alloys, and selected nickel compounds are presented in Table 1.1. This list is not exhaustive, nor does it necessarily reflect the commercial importance of the various nickel-containing substances, but it is indicative of the range of nickel alloys and compounds available, including some compounds that are important commercially, and those that have been tested in biological systems. Several inter-mediary compounds occur in refineries that cannot be characterized, and are thus not listed.
1.2 Chemical and physical properties of the agents
Nickel (atomic number, 28; atomic weight, 58.69) is a metal, which belongs to group VIIIB of the periodic table. The most important oxida-tion state of nickel is +2, although the +3 and +4 oxidation states are also known (Tundermann et al., 2005). Nickel resembles iron, cobalt, and copper in its chemical properties. However,
unlike cobalt and iron, it is normally only stable in aqueous solution in the + 2 oxidation state (Kerfoot, 2002). Selected chemical and physical properties for nickel and nickel compounds, including solubility data, were presented in the previous IARC Monograph (IARC, 1990), and have been reported elsewhere (ATSDR, 2005).
1.3 Use of the agents
The chemical properties of nickel (i.e. hard-ness, high melting point, ductility, malleability, somewhat ferromagnetic, fair conductor of heat and electricity) make it suitable to be combined with other elements to form many alloys (NTP, 2000; Tundermann et al., 2005). It imparts such desirable properties as corrosion resistance, heat resistance, hardness, and strength.
Nickel salts are used in electroplating, ceramics, pigments, and as intermediates (e.g. catalysts, formation of other nickel compounds). Sinter nickel oxide is used in nickel catalysts in the ceramics industry, in the manufacture of alloy steel and stainless steel, in the manu-facture of nickel salts for specialty ceramics, and in the manufacture of nickelcadmium (NiCd) batteries, and nickelmetal-hydride batteries. Nickel sulfide is used as a catalyst in