The amphibole hypothesis--a nested case-control study of lung cancer and exposure to chrysotile and amphiboles.

This paper describes a case control study investigating separately the lung cancer risk of exposure to chrysotile and to amphiboles. Logistic regression models were used to estimate separate exposure-response curves for the two fibre types, controlling for smoking. In the period longer than 15 years before lung cancer diagnosis, smokers above the 90th percentile of cumulative exposure to either chrysotile (OR = 1.8, 95% CI = 0.6-5.2) or amphibole (OR = 2.3, 95% CI = 0.9-6.2) had a somewhat higher risk than those with lower exposure. The author found suggestive evidence of an association between chrysotile and lung cancer, and especially between amphiboles and lung cancer. In this study, cumulative exposures to amphiboles were on average 40 times lower than cumulative exposures to chrysotile, and the author assumes that the amphibole effect would be much higher if the amphibole level of cumulative exposure were the same as that of chrysotile.