Long-term Exposure to PM2.5 and Incidence of Acute Myocardial Infarction

BACKGROUND: A number of studies have shown associations between chronic exposure to particulate air pollution and increased mortality, particularly from cardiovascular disease, but fewer studies have examined the association between long-term exposure to fine particulate air pollution and specific cardiovascular events, such as acute myocardial infarction (AMI). OBJECTIVE: We examined how long-term exposure to area particulate matter affects the onset of AMI, and we distinguished between area and local pollutants. METHODS: Building on the Worcester Heart Attack Study, an ongoing community-wide investigation examining changes over time in myocardial infarction incidence in greater Worcester, Massachusetts, we conducted a case-control study of 4,467 confirmed cases of AMI diagnosed between 1995 and 2003 and 9,072 matched controls selected from Massachusetts resident lists. We used a prediction model based on satellite aerosol optical depth (AOD) measurements to generate both exposure to particulate matter <= 2.5 mu m in diameter (PM2.5) at the area level (10 x 10 km) and the local level (100 m) based on local land use variables. We then examined the association between area and local particulate pollution and occurrence of AMI. RESULTS: An interquartile range (IQR) increase in area PM2.5 (0.59 mu g/m(3)) was associated with a 16% increase in the odds of AMI (95% CI: 1.04, 1.29). An IQR increase in total PM2.5 (area + local, 1.05 mu g/m(3)) was weakly associated with a 4% increase in the odds of AMI (95% CI: 0.96, 1.11). CONCLUSIONS: Residential exposure to PM2.5 may best be represented by a combination of area and local PM2.5, and it is important to consider spatial gradients within a single metropolitan area when examining the relationship between particulate matter exposure and cardiovascular events.