Risk of lung cancer following exposure to carbon black, titanium dioxide and talc: results from two case-control studies in Montreal

The International Agency for Research on Cancer (IARC) recently evaluated the carcinogenicity of three poorly soluble weakly-toxic substances: carbon black, titanium dioxide and talc. Though there is evidence of carcinogenity in experimental animals for these substances, the evidence in humans is sparse and equivocal. In the context of two large population based case-control studies of lung cancer carried out in Montreal, we were able to study the possible relationships between the exposure to each of these substances and subsequent risk of lung cancer. We were able to distinguish talc used for industrial purposes from that used for cosmetic purposes. Interviews for Study I were conducted in 1979-1986 (857 cases, 533 population controls, 1,349 cancer controls) and interviews for Study II were conducted in 1996-2001 (1,236 cases and 1,512 controls). Detailed lifetime job histories were elicited, and a team of hygienists and chemists evaluated the evidence of exposure to a host of occupational substances. Lung cancer risk was analysed in relation to each exposure, adjusting for several potential confounders, including smoking. Subjects with occupational exposure to carbon black, titanium dioxide, industrial talc and cosmetic talc did not experience any detectable excess risk of lung cancer. The results are consistent with the recent evaluations of the IARC Monographs.