Modeling mesothelioma risk factors from amphibole fiber dimensionality: mineralogical and epidemiological perspective

Amphiboles are common rock-forming minerals but when they form asbestos, they are known carcinogens. Mesothelioma mortality among miners and millers per the unit of asbestiform amphibole exposure varies significantly across cohorts when asbestos exposure measurements are based on the membrane filter method. Because the cohorts were exposed to different occurrences of asbestiform amphibole, variance in mesothelioma potency (R_M ) among cohorts is likely due to differences in exposure characteristics not reflected by the membrane filter method. In this paper using both linear and nonlinear models we correlate R_M from four mining and milling cohorts with two-dimensional parameters of the exposure. The parameters are based on the proportion of elongated minerals that are >5 μm in length from each occurrence that also have either (a) width ≤ 0.15 μm, or (b) width ≤ 0.25 μm. Based on the models we derived, it was possible to quantify R_M for the occurrences of asbestiform amphibole associated with mesothelioma excess but for which epidemiologically based R_M has not been published. It was demonstrated that modeled R_M for amphibole occurrences in nonasbestiform habits are lower (fibrous glaucophane) or not significant (cleavage fragments). The results of the study can be used in a risk assessment of elongated mineral particles and have implications for public policy and regulations.