Pleural plaques and lung function in the Marysville worker cohort: a re-analysis

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 D_LCO 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 D_LCO, 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.