Fine particulate air pollution and hospital admission for cardiovascular and respiratory diseases

Context: Evidence on the health risks associated with short-term exposure to fine particles (particulate matter ≤2.5 μm in aerodynamic diameter [PM_2.5]) is limited. Results from the new national monitoring network for PM_2.5 make possible systematic research on health risks at national and regional scales. Objectives: To estimate risks of cardiovascular and respiratory hospital admissions associated with short-term exposure to PM_2.5 for Medicare enrollees and to explore heterogeneity of the variation of risks across regions. Design, Setting, and Participants: A national database comprising daily time-series data daily for 1999 through 2002 on hospital admission rates (constructed from the Medicare National Claims History Files) for cardiovascular and respiratory outcomes and injuries, ambient PM _2.5 levels, and temperature and dew-point temperature for 204 US urban counties (population >200 000) with 11.5 million Medicare enrollees (aged >65 years) living an average of 5.9 miles from a PM_2.5 monitor. Main Outcome Measures: Daily counts of county-wide hospital admissions for primary diagnosis of cerebrovascular, peripheral, and ischemic heart diseases, heart rhythm, heart failure, chronic obstructive pulmonary disease, and respiratory infection, and injuries as a control outcome. Results: There was a short-term increase in hospital admission rates associated with PM _2.5 for all of the health outcomes except injuries. The largest association was for heart failure, which had a 1.28% (95% confidence interval, 0.78%-1.78%) increase in risk per 10-μg/m³ increase in same-day PM_2.5. Cardiovascular risks tended to be higher in counties located in the Eastern region of the United States, which included the Northeast, the Southeast, the Midwest, and the South. Conclusion: Short-term exposure to PM_2.5 increases the risk for hospital admission for cardiovascular and respiratory diseases.