Background: Ambient fine particulate matter (PM2.5) has been linked to cardiovascular mortality and morbidity, possibly arising from systemic inflammation, endothelial dysfunction, and oxidative stress, which may induce vasoconstriction and insulin resistance. Method: To determine whether long-term exposure to PM2.5 is associated with incident diabetes, we assembled a cohort of 62,012 nondiabetic adults who lived in Ontario, Canada, and who completed one of five population-based health surveys between 1996 and 2005. We also assembled a second cohort comprising the entire adult population of Ontario between 1996 and 2010 (～7 million). Follow-up extended until December 31, 2010. Incident diabetes, mostly type-Ⅱ, among cohort members was ascertained using the Ontario Diabetes Database, a validated registry (sensitivity=86% and specificity=97%). Long-term annual mean concentrations of PM2.5 at the residences of subjects were derived from satellite observations. We used Cox proportional hazards models, adjusting for numerous individual and contextual risk factors such as hypertension, body-mass index, smoking, diet, and neighbourhood income. We repeated the analysis for the entire Ontario cohort, but adjustment was limited to fewer covariates. We conducted several sensitivity analyses, including, assessing the impact of residential mobility on the effect estimates and examining whether the effects of PM2.5 changed over time. Results: Between 1996 and 2010, yearly incidence rate of diabetes in both cohorts was about 12 per 1000. In the analysis of the cohort from the surveys, for every 10μg/m3 increase of PM2.5, the adjusted hazard ratio (HR10) was 1.11 (95% confidence interval (CI): 1.02-1.21). For the entire Ontario cohort, we observed an adjusted HR10 of 1.15 (95%CI: 1.14-1.15). The estimates of association were unchanged in our sensitivity analyses. Conclusions: Results from this study contribute to a small, but growing body of literature suggesting an association between PM2.5 and development of diabetes.
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