Neurologic and reproductive effects of solvents on automotive repair workers: Assessment of Exposure for the Bay Area Solvent Study (BASS)

Abstract

Background: Peripheral neuropathy was diagnosed in automotive technicians visiting an occupational health clinic, although subsequent measurements indicated exposures to n-hexane, used for cleaning, were low. Furthermore, animal studies suggest n-hexane may also cause testicular toxicity. Aims: This epidemiologic study aims to investigate neurologic and reproductive effects of solvents on automotive repair workers. Methods: Industrial hygienists evaluated work practices of automechanics through site-visits, air measurements, and interviews to prepare questions about the frequency of task performance, work practices, and products used for an occupational history. Participants were recruited from the International Association of Machinists and Aerospace Workers. Clinical exams included tests for peripheral neuropathy, neurocognitive effects, color discrimination, time to pregnancy, and urinary reproductive hormonal metabolites. Results: The 835 participants who visited the BASS clinic for a two hour interview and examination had worked over 3,000 jobs at 1,952 shops. Algorithms were developed to estimate solvent exposures in each year (average intake of solvents each day) by integrating self-reported frequency of performing tasks (e.g., use of aerosol spray cans and solvent tanks) with MSDSs, measured and modeled airborne concentrations and estimates of dermal absorption. Major changes occurred in source of exposures over time, e.g., cleaning with solvent tanks accounted for 71% of solvent exposures in the 1960s, 30% in 2000-04, but only 7% in 2005-2012; concomitantly, exposures from aerosol cans rose from 23% to 64% and then 84%, and composition changed dramatically, notably for hexane and perchloroethylene. Conclusions: Work histories were more complex than indicated in the pilot of 39 mechanics. Exposures were significantly affected by temporal trends in cleaning methods, composition of materials, and work practices. Epidemiologic studies must account for these changes.