Trends in Excess Morbidity and Mortality Associated with Air Pollution above American Thoracic Society-Recommended Standards, 2008-2017.

Rationale: Air quality improvements are increasingly difficult to come by as modern pollution control technologies and measures have been widely implemented in the United States. Although there have been dramatic improvements in air quality over the last several decades, it is important to evaluate changes in the health impacts of air pollution for a more recent time period to better understand the current trajectory of air quality improvements.
Objectives: To provide county-level estimates of annual air pollution-related health outcomes across the United States and to evaluate these trends from 2008 to 2017, presented as part of the annual American Thoracic Society (ATS)/Marron Institute "Health of the Air" report.
Methods: Daily air pollution values were obtained from the U.S. Environmental Protection Agency's Air Quality System for monitors in the United States from 2008 to 2017. Concentration-response functions used in the ATS/Marron Institute "Health of the Air" report were applied to the pollution increments corresponding to differences between the rolling 3-year design values (reported as the third year) and ATS-recommended levels for annual particulate matter less than or equal to 2.5 μm in aerodynamic diameter (PM2.5; 11 μg/m3), short-term PM2.5 (25 μg/m3), and ozone (O3; 60 ppb). Health impacts were estimated at the county level in locations with valid monitor data.
Results: Annual excess mortality in the United States due to air pollution levels greater than recommended by the ATS decreased from approximately 12,600 (95% confidence interval [CI], 5,470-21,040) in 2010 to 7,140 (95% CI, 2,290-14,040) in 2017. This improvement can be attributed almost entirely to reductions in PM2.5-related mortality, which decreased by approximately 60% (reduced from 8,330 to 3,260 annual deaths), whereas O3-related mortality remained largely unchanged, other than year-to-year variability, over the same time period (reduced from 4,270 to 3,880 annual deaths). Conclusions: Improvements in health impacts attributable to ambient PM2.5 concentrations have been observed across most regions of the United States over the last decade, although the rate of these improvements has leveled off in recent years. Despite two revisions of the National Ambient Air Quality Standards strengthening the standard for O3 in 2008 and 2015, there has not yet been a substantial improvement in the health impacts attributable to O3 during this time period. In many U.S. cities, an increase in the exposed population over the last decade has outpaced the improvements in ambient O3 concentrations, resulting in a net increase in O3-related health impacts over time.