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Abstract
Background: In the 2014 Integrated Risk Information System (IRIS) assessment for Libby amphibole asbestos (LAA), US EPA calculated a reference concentration (RfC) based on the prevalence of pleural plaques in a group of vermiculite workers in Marysville, Ohio. This RfC is based on the assumption that pleural plaques are associated with adverse lung function. In this study, we evaluated the association between pleural plaques and lung function in the Marysville worker cohort to determine whether they are associated with adverse effects or, rather, are more likely a biomarker of cumulative exposure to LAA.
Methods: We obtained the dataset on the Marysville worker cohort from University of Cincinnati, which included information on demographics, occupational exposures and results of chest high-resolution computed tomography (HRCT)/computed tomography (CT) scans and pulmonary function tests (PFTs). We used multivariate linear regression to estimate mean differences in several lung function parameters, and logistic regression to evaluate the odds of abnormal ventilatory patterns, among men with different pulmonary findings on HRCT/CT scans.
Results: No statistically significant differences in FEV1, FVC, FEV1/FVC, TLC, RV or DLCO were observed between workers with normal scans and those with pleural plaques but no other abnormalities. In contrast, workers with other abnormal findings had statistically significant lower FEV1, FVC, TLC and DLCO, compared with those with normal scans.
Conclusions: This study does not indicate that pleural plaques have a significant effect on lung function when past asbestos exposure is accounted for.
Declaration of interest
Drs. Zu, Tao, and Goodman are employees at Gradient, an independent environmental and risk science consulting firm, in Cambridge, MA. Through a consulting contract between Gradient and W. R. Grace and Company, Drs. Zu, Tao, and Goodman have served as scientific consultants to W. R. Grace and Company on issues related to asbestos exposure and asbestos-related health risks. W. R. Grace and Company has provided research funding to Gradient for a systematic review of pleural plaques and lung function, recently published in Inhalation Toxicology. W.R. Grace and Company operated the mine in Libby, Montana, which produced the asbestos-containing vermiculite to which the Maryville plant workers were exposed, from 1963 to 1990. The work reported in this paper was conducted by the authors during the normal course of employment, and the authors have the sole responsibility for the writing, content, and conclusions in this article. Dr. Goodman has served as an expert witness on cases involving chrysotile asbestos and cancer risk and has received funding from Tucker Ellis & West LLP for the preparation of scientific manuscripts regarding radiation, mesothelioma and lung cancer. She previously worked at the National Cancer Institute as a Cancer Prevention Fellow.