Exposure-response modeling of non-cancer effects in humans exposed to Libby Amphibole Asbestos; update

The United States Environmental Protection Agency (EPA) developed a quantitative exposure-response model for the non-cancer effects of Libby Amphibole Asbestos (LAA) (EPA, 2014). The model is based on the prevalence of localized pleural thickening (LPT) in workers exposed to LAA at a workplace in Marysville, Ohio (Lockey et al., 1984; Rohs et al., 2008). Recently, Lockey et al. (2015a) published a follow-up study of surviving Marysville workers. The data from this study increases the number of cases of LPT and extends the observation period for a number of workers, thereby providing a strengthened data set to define and constrain the optimal exposure-response model for non-cancer effects from inhalation exposure to LAA. The new data were combined with the previous data to update the exposure-response modeling for LPT. The results indicate that a bivariate model using cumulative exposure and time since first exposure is appropriate, and the benchmark concentration is similar to the findings previously reported by EPA (2014). In addition, the data were also used to develop initial exposure-response models for diffuse pleural thickening (DPT) and small interstitial opacities (SIO).