Despite dramatic air quality improvement in the United States over the past decades, recent years have brought renewed scrutiny and uncertainty surrounding the effectiveness of specific regulatory programs for continuing to improve air quality and public health outcomes.
We employ causal inference methods and a spatial hierarchical regression model to characterize the extent to which a designation of “nonattainment” with the 1997 National Ambient Air Quality Standard for ambient fine particulate matter (PM2.5) in 2005 causally affected ambient PM2.5 and health outcomes among over 10 million Medicare beneficiaries in the Eastern United States in 2009–2012.
We found that, on average across all retained study locations, reductions in ambient PM2.5 and Medicare health outcomes could not be conclusively attributed to the nonattainment designations against the backdrop of other regional strategies that impacted the entire Eastern United States. A more targeted principal stratification analysis indicates substantial health impacts of the nonattainment designations among the subset of areas where the designations are estimated to have actually reduced ambient PM2.5 beyond levels achieved by regional measures, with noteworthy reductions in all-cause mortality, chronic obstructive pulmonary disorder, heart failure, ischemic heart disease, and respiratory tract infections.
These findings provide targeted evidence of the effectiveness of local control measures after nonattainment designations for the 1997 PM2.5 air quality standard.
From the Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, MA.
Submitted December 21, 2016; accepted October 24, 2017.
Data sets and code for reproducing the form of the analysis (with simulated Medicare health outcomes data) are available at https://dataverse.harvard.edu/dataverse/pm97naaqs and https://github.com/czigler/PM2.5-Nonattainment and are described in supplementary Appendix A.
This work was supported by research funding from NIHR01ES026217, R01GM111339, R01ES024332, and P50MD010428, EPA 83587201, and HEI 4909 and 4953. Its contents are solely the responsibility of the grantee and do not necessarily represent the official views of the US EPA. Further, US EPA does not endorse the purchase of any commercial products or services mentioned in the publication.
The authors report no conflicts of interest.
Supplemental digital content is available through direct URL citations in the HTML and PDF versions of this article (www.epidem.com).
Correspondence: Corwin M. Zigler, Department of Biostatistics, Building 2, 4th Floor, 655 Huntington Avenue, Boston, MA 02115. E-mail: firstname.lastname@example.org.