Associations between long-term exposure to chemical constituents of fine particulate matter (PM2.5) and mortality in Medicare enrollees in the eastern United States

• Published in: Environmental health perspectives 2015-05, Vol.123 (5), p.467-467
• Main Authors: Chung, Yeonseung, Dominici, Francesca, Wang, Yun, Coull, Brent A, Bell, Michelle L
• Format: Article
• Language: English
• Subjects: Age; Aged; Air pollution; Air Pollution - adverse effects; Analysis; Carbon; Confounding (Statistics); Constituents; Control; Data analysis; Deviation; Environmental Exposure - adverse effects; Environmental Monitoring; Exposure; Female; Health aspects; Humans; Laws, regulations and rules; Male; Markov analysis; Mathematical models; Medicare; Mortality; Nitrates; Older people; Organic carbon; Particles; Particulate matter; Particulate Matter - toxicity; Pollutants; Postal codes; Silicon; Sodium; Statistical methods; Studies; Toxicity; United States
• ISSN: 0091-6765; 1552-9924
• DOI: 10.1289/ehp.1307549

Several epidemiological studies have reported that long-term exposure to fine particulate matter (PM2.5) is associated with higher mortality. Evidence regarding contributions of PM2.5 constituents is inconclusive. We assembled a data set of 12.5 million Medicare enrollees (≥ 65 years of age) to determine which PM2.5 constituents are a) associated with mortality controlling for previous-year PM2.5 total mass (main effect); and b) elevated in locations exhibiting stronger associations between previous-year PM2.5 and mortality (effect modification). For 518 PM2.5 monitoring locations (eastern United States, 2000-2006), we calculated monthly mortality rates, monthly long-term (previous 1-year average) PM2.5, and 7-year averages (2000-2006) of major PM2.5 constituents [elemental carbon (EC), organic carbon matter (OCM), sulfate (SO42-), silicon (Si), nitrate (NO3-), and sodium (Na)] and community-level variables. We applied a Bayesian hierarchical model to estimate location-specific mortality rates associated with previous-year PM2.5 (model level 1) and identify constituents that contributed to the spatial variability of mortality, and constituents that modified associations between previous-year PM2.5 and mortality (model level 2), controlling for community-level confounders. One-standard deviation (SD) increases in 7-year average EC, Si, and NO3- concentrations were associated with 1.3% [95% posterior interval (PI): 0.3, 2.2], 1.4% (95% PI: 0.6, 2.4), and 1.2% (95% PI: 0.4, 2.1) increases in monthly mortality, controlling for previous-year PM2.5. Associations between previous-year PM2.5 and mortality were stronger in combination with 1-SD increases in SO42- and Na. Long-term exposures to PM2.5 and several constituents were associated with mortality in the elderly population of the eastern United States. Moreover, some constituents increased the association between long-term exposure to PM2.5 and mortality. These results provide new evidence that chemical composition can partly explain the differential toxicity of PM2.5.