Effects of airborne fine particles (PM_2.5) on deep vein thrombosis admissions in the northeastern United States

Summary: Background: Literature relating air pollution exposure to deep vein thrombosis (DVT) and pulmonary embolism (PE), despite biological plausibility, is sparse. No comprehensive study examining associations between both short- and long-term exposure to particulate matter (PM)_2.5 and DVT or PE has been published. Using a novel PM_2.5 prediction model, we study whether long- and short-term PM_2.5 exposure is associated with DVT and PE admissions among elderly across the northeastern United States. Methods: We estimated daily exposure of PM_2.5 in each ZIP code. We investigated the long- and short-term effects of PM_2.5 on DVT and PE hospital admissions. There were 453 413 DVT and 151 829 PE admissions in the study. For short-term exposure, we performed a case crossover analysis matching month and year and defined the hazard period as lag 01 (exposure of day of admission and previous day). For the long-term association, we used a Poisson regression. Results: A 10-μg m^-3 increase in short-term exposure was associated with a 0.63% increase in DVT admissions (95% confidence interval [CI] = 0.03% to 1.25%) and a 6.98% (95% CI = 5.65% to 8.33%) increase in long-term exposure admissions. For PE, the associated risks were 0.38% (95% CI = -0.68% to 1.25%) and 2.67% (95% CI = 5.65% to 8.33%). These results persisted when analyses were restricted to location-periods meeting the current Environmental Protection Agency annual standard of 12 μg m^-3. Conclusions: Our findings showed that PM_2.5 exposure was associated with DVT and PE hospital admissions and that current standards are not protective of this result.