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Nickel metal not associated with lung cancer risk.

Beveridge et al. [2010] concluded that occupational exposure to nickel is associated with lung cancer risk. The majority of workers exposed to nickel in their study were sheet metal workers, metal machinists, and metal product fabricators. There were no data on exposure levels or nickel species, but the primary form of nickel to which these workers would have been exposed (if at all) is nickel metal. Beveridge et al. [2010] noted that only 1–2% of nickelexposed workers were exposed to ‘‘substantial’’ levels. Relatively large cohorts exposed to metallic nickel at likely several-fold higher levels than those to which the workers assessed by Beveridge et al. [2010] were exposed did not experience excess cancer risks [ICNCM, 1990; Sivulka, 2005; Beveridge et al., 2010]. It is not scientifically plausible that lung cancer risks would increase at exposure levels far below those measured in other robust studies that did not show increased risks. Considerable evidence also indicates that only certain forms of nickel are carcinogenic, and nickel metal is not one of them [Sivulka, 2005; Oller et al., 2008]. The indication of lung cancer risk by Beveridge et al. [2010] is inconsistent with the vast body of literature indicating nickel metal is not carcinogenic. Beveridge et al. [2010] may have established associations between certain occupations and lung cancer, but because of the lack of specific exposure data, this study cannot evaluate whether associations are due to nickel, as all nickel-exposed workers were also exposed to many other things. For example, among those ever exposed to nickel, 49% were exposed to chromium and 8% to cadmium. These and other exposures included in statistical models were considered as binary variables (i.e., never vs. ever exposed), so the possibility for confounding from exposures not included in models, and residual confounding from those that were, is high. Given that the main nickel occupations in the Beveridge et al. [2010] study involve low exposures to nickel metal and the preponderance of evidence indicating nickel metal is not a lung carcinogen, results from this study should be viewed with caution.