Chronic fine and coarse particulate exposure, mortality, and coronary heart disease in the Nurses' Health Study

Abstract

Background: The relationship of fine particulate matter < 2.5 microm in diameter (PM(2.5)) 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 microm (PM(10-2.5)), 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 PM(2.5) and PM(10-2.5) 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-microg/m(3) increase in annual PM(2.5) exposure. The association between fatal CHD and PM(10-2.5) was weaker.

Conclusions: Our findings contribute to growing evidence that chronic PM(2.5) exposure is associated with risk of all-cause and cardiovascular mortality.

Keywords: air pollution; cardiovascular disease; mortality; particulate matter.

Figure 1

HRs and 95% CIs for the association between all-cause and cause-specific mortality and a 10-μg/m³ change in average PM_2.5 and PM_10–2.5 for six time periods of exposure. aFine and coarse PM levels modeled simultaneously, stratified by age in months, adjusted for state of residence, year and season, smoking status, family history of MI, BMI, hypercholesterolemia, diabetes, hypertension, median family income in census tract of residence, physical activity, and median house value in census tract of residence.