Malignant pleural mesothelioma in US automotive mechanics: Reported vs expected number of cases from 1975 to 2007

Until the 1980s, chrysotile asbestos was a component of automotive brakes manufactured in the US. The current OSHA Bulletin (2006) for brake repair cites a single study (Lemen, 2004) which concluded that the number of mesothelioma cases reported in the literature in "end-product users of friction materials" indicated an asbestos-related risk for auto mechanics. However, Lemen (2004) did not compare the reported number of cases to an "expected" value, even though pleural mesothelioma occurs in the general population in the absence of asbestos exposure. We compare the number of malignant pleural mesothelioma (MPM) cases reported in the US literature among auto mechanics between 1975-2007 to an expected value derived from estimated numbers of current and former auto mechanics. A total of 106 cases categorized as mesothelioma or malignant neoplasm of the pleura were found in the literature. Using background incidence rates for MPM of two and three cases per million individuals per year, we estimated that a range of 278-515 cases of non-asbestos-related MPM, respectively, would have occurred in current or former auto mechanics from 1975-2007. Our findings are consistent with the numerous epidemiology studies that have found no increased risk of MPM in auto mechanics.