Gene (HPRT) and chromosomal (MN) mutations of nickel metal powder in V79 Chinese hamster cells.

Nickel metal is a naturally occurring element used in many industrial and consumer applications. Human epidemiological data and animal cancer bioassays indicate that nickel metal is not likely to be a human carcinogen. Yet, nickel metal is classified as a suspected human carcinogen (CLP) and possibly carcinogenic to humans (IARC). There are no reliable studies on the potential for nickel metal to induce gene and micronucleus (MN) mutations. To fill these datagaps and increase our understanding of the mechanisms underlying the lack of nickel metal carcinogenicity, gene and micronucleus mutation studies were conducted with nickel metal powder (N36F) in V79 Chinese Hamster cells following OECD 476 and 487 guidelines, respectively, under GLP. Gene mutation at the hprt locus was tested, with and without metabolic activation, after 4-h treatment with 0.05-2.5 mM nickel metal powder. Cytokinesis-block MN frequency following exposure to 0.25-1.5 mM nickel metal was tested after 4-h treatment, with and without metabolic activation, followed by a 24-h treatment without metabolic activation. In the gene mutation assay, there were modest increases in hprt mutants observed at some test concentrations, not exceeding 2.2-fold, which were either within the historical control values and/or showed no concentration-response trend. The positive controls showed increases of at least 7-fold. Likewise, no increases in the MN frequency exceeding 1.5-fold were observed with nickel metal, with no concentration-response trends. Taking these results together, it can be concluded that nickel metal is non-mutagenic and does not cause gene nor chromosomal mutations.