A meta-analysis that was recently published in thisJournal 1 suggested an association between excess pancreatic cancer risk and exposure to nickel and nickel compounds (meta-risk ratio 1.9, 95% confidence interval (95% CI) 1.2 to 3.2, based on four studies). Through correspondence with the authors (Ojajärvi et al), I learned that their analysis excluded the many epidemiological studies that had been conducted on workers in the nickel refining and alloy production industries. Although most of these studies could not contribute to the meta-analysis due to a failure to specifically examine risk of pancreatic cancer, I found two studies of nickel workers that provide relevant data.

I think that one of these studies, which examined mortality in 11 500 nickel mining and smelting workers,2 should have been included in the meta-analysis by Ojajärvi et al,1 based …