In recent years (2000–2007), ambient levels of fine particulate matter (PM2.5) have continued to decline as a result of interventions, but the decline has been at a slower rate than previous years (1980–2000). Whether these more recent and slower declines of PM2.5 levels continue to improve life expectancy and whether they benefit all populations equally is unknown.
We assembled a data set for 545 U.S. counties consisting of yearly county-specific average PM2.5, yearly county-specific life expectancy, and several potentially confounding variables measuring socioeconomic status, smoking prevalence, and demographic characteristics for the years 2000 and 2007. We used regression models to estimate the association between reductions in PM2.5 and changes in life expectancy for the period from 2000 to 2007.
A decrease of 10 μg/m3 in the concentration of PM2.5 was associated with an increase in mean life expectancy of 0.35 years (SD = 0.16 years, P = 0.033). This association was stronger in more urban and densely populated counties.
Reductions in PM2.5 were associated with improvements in life expectancy for the period from 2000 to 2007. Air pollution control in the last decade has continued to have a positive impact on public health.
aFrom the Department of Biostatistics, Harvard School of Public Health, Boston, MA; bDepartment of Economics, Brigham Young University, Provo, UT; cDepartments of Environmental Health and Epidemiology, Harvard School of Public Health, Boston, MA; dMRC-HPA Centre for Environment and Health and Department of Epidemiology and Biostatistics, Imperial College London, Norfolk Place, St Mary’s Campus, London, United Kingdom.
Submitted 28 March 2012; accepted 1 October 2012.
Supported by the U.S. Environmental Protection Agency (R-834894). Additional funding was provided by the U.S. EPA (RD-83479801), National Institutes of Health (ES019560 and ES012054), Harvard-NIEHS Center for Environmental Health (ES000002), NIEHS (T32ES007142), MRC Strategic Grant, and the Health Effects Institute.
The authors report no conflict of interest.
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Editors’ note: A commentary on this article appears on page 32.
Correspondence: Francesca Dominici, Department of Biostatistics, Harvard School of Public Health, 655 Huntington Avenue, HSPH Building 2, 4th Floor, Boston, MA 02115. E-mail: firstname.lastname@example.org.