Associations of PM2.5 Constituents and Sources with Hospital Admissions: Analysis of Four Counties in Connecticut and Massachusetts (USA) for Persons ≥ 65 Years of Age

Background: Epidemiological studies have demonstrated associations between short-term -exposureto PM2.5 and hospital admissions. The chemical composition of particles varies across locations and time periods. Identifying the most harmful constituents and sources is an important health and regulatory concern. OBJECTIVES: We examined pollutant sources for associations with risk of hospital admissions for cardiovascular and respiratory causes. METHODS: We obtained PM2.5 filter samples for four counties in Connecticut and Massachusetts and analyzed them for PM2.(5) elements. Source apportionment was used to estimate daily PM2.5 contributions from sources (traffic, road dust, oil combustion, and sea salt as well as a regional source representing coal combustion and other sources). Associations between daily PM2.5 constituents and sources and risk of cardio-vascular and respiratory hospitalizations for the Medicare population (> 333,000 persons >= 65 years of age) were estimated with time-series analyses (August 2000-February 2004). RESULTS: PM2.5 total mass and PM2.5 road dust contribution were associated with cardio-vascular hospitalizations, as were the PM2.5 constituents calcium, black carbon, vanadium, and zinc. For respiratory hospitalizations, associations were observed with PM2.5 road dust, and sea salt as well as aluminum, calcium, chlorine, black carbon, nickel, silicon, titanium, and vanadium. Effect estimates were generally robust to adjustment by co-pollutants of other constituents. An interquartile range increase in same-day PM2.5 road dust (1.71 mu g/ m(3)) was associated with a 2.11% (95% CI: 1.09, 3.15%) and 3.47% (95% CI: 2.03, 4.94%) increase in cardio-vascular and respiratory admissions, respectively. CONCLUSIONS: Our results suggest some particle sources and constituents are more harmful than others and that in this Connecticut/ Massachusetts region the most harmful particles include black carbon, calcium, and road dust PM2.5.