Peng, RD; Chang, HH; Bell, ML; McDermott, A; Zeger, SL; Samet, JM; Dominici, F
Health risks of fine particulate matter of 2.5 mu m or less in aerodynamic diameter (PM sub(2.5)) have been studied extensively over the last decade. Evidence concerning the health risks of the coarse fraction of greater than 2.5 mu m and 10 mu m or less in aerodynamic diameter (PM sub(10-2.5)) is limited. OBJECTIVE: To estimate risk of hospital admissions for cardiovascular and respiratory diseases associated with PM sub(10-2.5) exposure, controlling for PM sub(2.5). Design, Setting, and Participants Using a database assembled for 108 US counties with daily cardiovascular and respiratory disease admission rates, temperature and dew-point temperature, and PM sub(10-2.5) and PM sub(2.5) concentrations were calculated with monitoring data as an exposure surrogate from January 1, 1999, through December 31, 2005. Admission rates were constructed from the Medicare National Claims History Files, for a study population of approximately 12 million Medicare enrollees living on average 9 miles (14.4 km) from collocated pairs of PM sub(10) and PM sub(2.5) monitors. MAIN OUTCOME MEASURES: Daily counts of county-wide emergency hospital admissions for primary diagnoses of cardiovascular or respiratory disease. RESULTS: There were 3.7 million cardiovascular disease and 1.4 million respiratory disease admissions. A 10- mu g/m super(3) increase in PM sub(10-2.5) was associated with a 0.36% (95% posterior interval [PI], 0.05% to 0.68%) increase in cardiovascular disease admissions on the same day. However, when adjusted for PM sub(2.5), the association was no longer statistically significant (0.25%; 95% PI, -0.11% to 0.60%). A 10- mu g/m super(3) increase in PM sub(10-2.5) was associated with a nonstatistically significant unadjusted 0.33% (95% PI, -0.21% to 0.86%) increase in respiratory disease admissions and with a 0.26% (95% PI, -0.32% to 0.84%) increase in respiratory disease admissions when adjusted for PM sub(2.5). The unadjusted associations of PM sub(2.5) with cardiovascular and respiratory disease admissions were 0.71% (95% PI, 0.45%-0.96%) for same-day exposure and 0.44% (95% PI, 0.06% to 0.82%) for exposure 2 days before hospital admission. CONCLUSION: After adjustment for PM sub(2.5), there were no statistically significant associations between coarse particulates and hospital admissions for cardiovascular and respiratory diseases.
