Healthy Worker Effect, Occupational Exposure to PM and Cardiopulmonary Mortality

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DESCRIPTION (provided by applicant): The goal of this revised proposal is to examine the relation between long-term quantitative exposure to metalworking fluids (MWF) and cardiopulmonary mortality. MWF are complex mixtures of oils and chemical additives widely used in industrial settings to cool and lubricate metal machining operations. Oil-based MWF contain polyaromatic hydrocarbons and metals, constituents also present in the fine particulate mass (PM2.5) of traffic-related air pollution, a well established cardiovascular hazard. Moreover, occupational exposure to MWF occurs at high concentrations - orders of magnitude higher than ambient air pollution - providing further support for the hypotheses of interest. The proposal builds on our recent application of g-estimation to control for healthy worker survivor effect (HWSE) in a cohort study of Michigan autoworkers exposed to MWF; the first implementation of this causal method in an occupational study. New results based on g-estimation reported since our previous submission suggest that duration of exposure to oil-based MWF significantly increases the risk of mortality due to both ischemic heart disease and chronic obstructive pulmonary disease. Both relationships were only detected after adjustment for HWSE. We now propose to extend the g-estimation framework from binary exposure to concentration - by taking advantage of existing quantitative measures of size fractionated particle mass (PM) of MWF (mg/m3). The United Autoworkers - General Motors cohort study is a rich resource due to its size (almost 40,000 subjects), diversity, 60 year vital status follow-up period, and quantitative metrics of exposure to oil-and water-based MWF (PM3.5 and PM3.5-9.8). Using available samples, we will compare the physicochemical composition of MWF with air pollution and cigarette smoke - by particle size fractions of PM3.5 and PM3.5-9.8 - using common analytic techniques. These chemical results will complement the epidemiologic findings. There is no specific health standard for MWF; they are subject only to generic exposure limits for particles not otherwise regulated. In April 2010, the United Autoworkers again petitioned OSHA for a MWF standard on the basis of asthma, hypersensitivity pneumonitis and cancer, underscoring the significance and timeliness of this application. The proposal addresses a critical gap in knowledge about the cardiopulmonary health risks of occupational exposures to small particles in general, and to MWF in particular. With the growth of the green manufacturing sector, e.g., fuel efficient automobiles, light rail cars and wind turbine systems, the number of workers exposed to MWF will likely increase. Given widespread industrial exposure combined with the high incidence of these chronic diseases, even a modestly elevated mortality rate ratio would imply a substantial occupational burden. PUBLIC HEALTH RELEVANCE: The goal of the proposed research is to examine cardiovascular and chronic obstructive pulmonary disease mortality in relation to long-term quantitative exposure to metalworking fluids (MWF) in a heavily exposed UAW-GM autoworker cohort with over 60 years of follow-up. The proposal builds on recent findings suggesting that duration of exposure to oil-based straight MWF significantly increases the risk of mortality due to both ischemic heart disease and COPD, but only after adjustment for healthy worker survivor effect. We will extend the g-estimation framework from duration of exposure to concentration by taking full advantage of existing quantitative measures of MWF (respirable, thoracic and total particulate matter). Results will contribute to the prevention of cardiopulmonary diseases in workers exposed to metal working fluids throughout the manufacturing sector.