Response to letter from S.K. Seilkop [letter to the editor].
Cancer Causes Control 2002 Oct; 13(8):785
Woe to the author of articles about silica who foolishly dabbles in data about nickel. It does appear that we have misrepresented the summary of nickel data presented in the 1990 report by the International Committee on Nickel Carcinogenesis in Man (ICNCM) . To illustrate the relatively low lung carcinogenicity of silica compared to nickel (as well as to other metals), we used lung cancer rates ratios for low and high exposure to soluble nickel from Table 34 of that report, collapsing across strata of sulfidic and oxidic nickel. As noted by Steven Seilkop, the ICNCM report in fact is cautious in its assessment of the independent role of soluble nickel, noting that ''there was also evidence that soluble nickel exposure increased the risk of these (lung and nasal) cancers and that it may enhance risks associated with exposures to less soluble forms of nickel''. Given that the evidence that oxidic and/or sulfidic nickel causes lung cancer is more straightforward than the evidence for soluble nickel, which may act primarily as an effect modifier (although the issue is difficult because exposure to these different species of nickel often occurs simultaneously), we should have used rate ratios for the less soluble species of nickel to illustrate our point about the relative carcinogenic potency of silica.
Silicates; Silica-dusts; Nickel-compounds; Carcinogens; Carcinogenicity; Carcinogenesis; Lung-cancer; Exposure-levels; Exposure-assessment; Risk-factors; Risk-analysis
NIOSH R13, Dept. of Health and Human Services, Robert A. Taft Laboratories, 4676 Columbia Parkway, Cincinnati, OH 45226, USA
Cancer Causes and Control