Chronic exposure to particulate matter and risk of cardiovascular mortality: Cohort study from Taiwan

Background: Evidence on the association between long-term exposure to air pollution and cardiovascular mortality is limited in Asian populations. Methods: We conducted a cohort study on the association between fine particulate matter (PM_2.5) and cardiovascular mortality using 43,227 individuals in a civil servants health service in Taiwan. Each participant was assigned an exposure level of particulate matter based on their district of residence using air pollution data collected by the Taiwan Environmental Protection Agency and with modeling using geographic information systems. The participants were followed up from 1989 to 2008 and the vital status was ascertained from death records. Cox regression models were used to adjust for confounding factors. Results: The district-level average of PM_2.5 ranged from 22.8 to 32.9 μg/m³ in the study area. After a median follow-up of 18 years, 1992 deaths from all causes including 230 cardiovascular deaths occurred. After adjustment for potential confounders, PM_2.5 levels were not significantly associated with mortality from cardiovascular disease [Hazard Ratio (HR) 0.80; 95 % Confidence Interval (CI), 0.43 to 1.50 per 10 μg/m³ increase in PM_2.5] or all causes (HR 0.92; 95 % CI, 0.72 to 1.17 per 10 μg/m³ increase in PM_2.5). The results were similar when the analysis was restricted to the urban areas and when the PM_2.5 measurement was changed from the period average (2000-2008) to annual average. Discussion: Our findings are different from those in prior cohort studies conducted in Asia where ambient air pollutionwas associated with an increased risk of cardiovascular mortality. The high background level of air pollutionin our study area and the small number of event cases limited the power of this study. Conclusions: In this population-based cohort study in Taiwan, we found no evidence of increased risk for all-cause or cardiovascular mortality with long-term exposure to PM_2.5.