New Perspectives on the Relationship Between Formaldehyde and Lung Cancer. J. E. Korte, I. Hertz-Picciotto, and M. R. Schultz, Department of Epidemiology, University of North Carolina, Chapel Hill, NC 27599-7400; and L. M. Ball, Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC 27599-7400
Formaldehyde is recognized as a nasal carcinogen in humans. Its lung carcinogenicity has been the subject of controversy, with debate surrounding an occupationally exposed cohort first analyzed by Blair et al. We evaluated the plausibility of the dose-response curve presented in support of lung carcinogenesis by Sterling & Weinkam, who challenge Blair & Stewart’s conclusion that other exposures cause the lung cancer in the cohort. Exposure assessment proceeded as follows. Mainstream smoke from a typical cigarette contains 54 (g formaldehyde, and sidestream smoke contains 700 (g. We assumed smokers inhale 100% of mainstream and 3.3% of sidestream smoke. The carcinogenic potency of formaldehyde was estimated using the Sterling & Weinkam dose-response curve. Lifetime risks of lung cancer were calculated for never, light (20 cigarettes/day), and heavy smokers (40 cigarettes/day), using lifetables to adjust for competing causes and to quantify the formaldehyde contribution at the calculated potency. The results showed that, depending on the number of daily cigarettes, between 44 and 122 smoking-induced lung cancer deaths occur per 1000 smokers. Using the potency derived from Sterling & Weinkam’s results, formaldehyde alone is estimated to account for 54% to 66% of these deaths (95% upper confidence limits, 75% to 83%). However, cigarette smoke contains significant doses of well-established lung carcinogens (e.g. nickel, cadmium, chromium, arsenic, polycyclic aromatic hydrocarbons, nitrosamines, and radioactive elements) in addition to formaldehyde. We therefore conclude that Sterling & Weinkam’s dose-response curve overestimates the carcinogenic potency of formaldehyde, and results in implausibly high predictions relative to observed lung cancer mortality in smokers.
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