Pleural thickening in a population environmentally exposed to amphibole asbestos as children

Abstract

Introduction. Residents of Libby, MT, a small community in the northern Rocky Mountains, were exposed to a mined material that was naturally contaminated with amphibole asbestos (LA). The purpose of this study was to evaluate lung findings among adults who were exposed to this material during childhood. Methods. Eligible participants lived in Libby for a minimum of six months but left the area prior to ages 23 for males and 21 for females. Cumulative exposure to LA via several environmental pathways was characterized from exposure history questionnaire, and people were excluded if they had worked for the local mining company. Participants underwent chest computed tomography (CT) and pulmonary function tests. A pleural score (PS) was calculated among those with pleural thickening (PT). Logistic and multivariate linear regression was used to evaluate associations between LA exposure, PT and pulmonary function measures. Results. A total of 198 subjects (59% female) were recruited with a mean (sd) age of 50.2 (11.4). PT was demonstrated in 96 (48%). The OR (and 95% CI) for presence of PT adjusted for age, gender and body mass index was 1.73 (1.14-2.64) per interquartile increase in the cumulative metric for environmental exposure. Among those with PT, unit increase in PS was inversely associated with change in percent predicted for forced vital capacity (adjusted parameter coefficient (95% CI) = -0.92 (-1.5, -0.36)), total lung capacity (-0.74 (-1.3, -0.19)) and diffusing capacity of the lung (-1.6 (-2.4, -0.72)). Conclusions. Participants in this study experienced low, non-occupational exposure to LA only during childhood, yet almost half had PT. We demonstrated that the extent of PT was associated with lower pulmonary function measures. Prospective follow-up will be necessary to examine related risk of restrictive asbestos-related pleuropulmonary disease among this environmentally exposed population.