Dose-Response Relationship Between Airborne and Lung Asbestos Fibre Type, Length and Concentration, and the Relative Risk of Mesothelioma

Abstract

In a case-control study of mesothelioma, univariate analysis and multivariate risk models found increasing relative risk (odds ratio) with increasing residual lung asbestos fibre burdens and fibre length for crocidolite, amosite and chrysotile determined by Transmission Electron Microscopy (TEM). By comparing cumulative exposures derived from occupational histories and lung fibre burdens an approximate 1000-fold difference in lung clearance rates between chrysotile and amphiboles was found. Using a simplistic application of this clearance rate to the additive relative risk model (R = 1 + ∑b_ix_i), additive risk coefficients for airborne exposure were as follows: crocidolite ≥ 10 μm (9.1); amosite ≥ 10 μm (5.2); and chrysotile < 10 μm (0.006–0.01013). This is consistent with the occupational histories which show a dominance of crocidolite followed by amosite. It is difficult to assess the risk of chrysotile alone due to the considerable differential in clearance rates and the almost universal mixed exposure to chrysotile and amphiboles.