2010 Feb. 9: SC, MA & CA: Scientific Paper: Chronic Fine and Coarse Particulate Exposure, Mortality, and Coronary Heart Disease in the Nurses’ Health Study
Robin C. Puett; Jaime E. Hart; Jeff D Yanosky; Christopher Paciorek; Joel Schwartz; Helen Suh; Frank E Speizer; Francine Laden
Posted: 02/09/2010; Environmental Health Perspectives. 2009;117(11):1697–1701 © 2009
Abstract and Introduction
Background: The relationship of fine particulate matter < 2.5 µm in diameter (PM2.5) air pollution with mortality and cardiovascular disease is well established, with more recent long-term studies reporting larger effect sizes than earlier long-term studies. Some studies have suggested the coarse fraction, particles between 2.5 and 10 µm (PM10–2.5), may also be important. With respect to mortality and cardiovascular events, questions remain regarding the relative strength of effect sizes for chronic exposure to fine and coarse particles.
Objectives: We examined the relationship of chronic PM2.5 and PM10–2.5 exposures with all-cause mortality and fatal and nonfatal incident coronary heart disease (CHD), adjusting for time-varying covariates.
Methods: The current study included women from the Nurses’ Health Study living in metropolitan areas of the northeastern and midwestern United States. Follow-up was from 1992 to 2002. We used geographic information systems–based spatial smoothing models to estimate monthly exposures at each participant’s residence.
Results: We found increased risk of all-cause mortality [hazard ratio (HR), 1.26; 95% confidence interval (CI), 1.02–1.54] and fatal CHD (HR = 2.02; 95% CI, 1.07–3.78) associated with each 10-µg/m3 increase in annual PM2.5 exposure. The association between fatal CHD and PM10–2.5 was weaker.
Conclusions: Our findings contribute to growing evidence that chronic PM2.5 exposure is associated with risk of all-cause and cardiovascular mortality.
A substantial body of literature has shown associations of particulate air pollution with mortality and specifically cardiovascular disease. Recent studies have focused on the fine fraction < 2.5 µm in diameter (PM2.5) (Eftim et al. 2008; Laden et al. 2006; Miller et al. 2007). However, some studies have suggested that the coarse fraction, particles between 10 and 2.5 µm (PM10–2.5), may be important as well (Brunekreef and Forsberg 2005; Host et al. 2008; Lipsett et al. 2006). A recent study in the Women’s Health Initiative (WHI) reported a 24% increase in the risk of a cardiovascular event [hazard ratio (HR) = 1.24; 95% confidence interval (CI), 1.09–1.41] and a 76% increase in the risk of death from cardiovascular disease (HR = 1.76; 95% CI, 1.25–2.47) for each 10-µg/m3 change in PM2.5 levels measured in 2000 (Miller et al. 2007). The magnitude of these estimates is higher than those reported in most long-term follow-up studies (Laden et al. 2006; Pope et al. 2002). Neither Pope et al. (2002) nor Miller and coauthors (2007) observed evidence of a positive association with PM10–2.5.
We previously observed a positive association of chronic PM10 (particles < 10 µm in aerodynamic diameter) exposures and all-cause mortality and fatal coronary heart disease (CHD) in the Nurses’ Health Study (NHS), a prospective cohort study of U.S. women (Puett et al. 2008). In the current study, we extend that study to look specifically at exposures to PM2.5 and PM10–2.5 in the same population. This longstanding cohort provides a unique opportunity with biennial updated assessment of covariates to examine these associations. With the geocoding of the nurses’ biennially updated residential addresses and the recent development of geographic information systems (GIS)–based spatial smoothing models, this study uses time- and space-resolved PM2.5 and PM10–2.5 exposures at the monthly level. This individual-specific exposure assessment approach has not been possible in many previous studies of chronic air pollutant effects.