Malignant mesothelioma and asbestos exposure among auto mechanics: appraisal of scientific evidence

Abstract

In 1986 the U.S. Environmental Protection Agency (EPA) issued an official guideline on the prevention of asbestos disease among auto mechanics. In the EPA guideline, malignant mesothelioma was listed as a consequence of exposure to asbestos fibers from brake linings and clutch facings among auto mechanics. EPA formulated its 1986 opinion by relying solely on a few outdated case reports and not on epidemiologic studies. A review of the literature indicates that there are six epidemiologic studies providing relevant information on malignant mesothelioma among auto mechanics. Three of the six studies had already been published by 1986, the year in which EPA issued its guideline. The results of the six studies were remarkably consistent in that all six studies reported no increased risk of malignant mesothelioma among auto mechanics. The relative risks reported in the six studies ranged from 0.62 to 1.00. Based on a meta-analysis of the combined data of all six studies consisting of approximately 1500 malignant mesothelioma cases, the mesothelioma relative risk for auto mechanics is 0.90 (95% confidence interval 0.66-1.23). An application of Hill's causation criteria to epidemiologic data of malignant mesothelioma among auto mechanics clearly demonstrates that auto mechanics do not have an increased risk of malignant mesothelioma as a result of exposure to asbestos fibers from brake linings and clutch facings. However, in spite of the scientific evidence, EPA has not modified or revised its 1986 guideline. Occupational regulatory policies and guidelines, when based on proper scientific evidence, are invaluable and can prevent avoidable diseases in workers or other exposed individuals in the general public. On the other hand, it is the regulators' responsibility to develop, modify, and revise policies and guidelines in accordance with the most relevant and the latest scientific data. In this instance EPA as a regulator has not fulfilled its responsibility of providing the most accurate and up-to-date information to the workers or the general public.