Deaths from exposure to air pollution levels above those recommended by the American Thoracic Society (ATS) have fallen by nearly half in the U.S. during the last decade, primarily due to reductions in particulate-matter exposure, researchers reported.
Improvements in mortality attributable to lower levels of particulate matter of 2.5 microns or smaller (PM2.5) were seen across most regions in the U.S., but they were especially pronounced in cities with the highest pollution-related health issues, according Kevin Cromar, PhD, of the Marron Institute of Urban Management at New York University in New York City, and colleagues.
Based on the third annual analysis of EPA Air Quality System data from 2008 through 2017, the “Health of the Air” report estimated a reduction in PM2.5-related mortality of nearly 60% during the period.
But mortality from ozone pollution was largely unchanged, they reported in the Annals of the American Thoracic Society.
“This analysis shows a dramatic improvement in the health impact for particulate matter over much of the country,” Cromar told MedPage Today.
The analysis also showed a leveling off in the health gains due to particulate pollution declines since 2014.
The concern is that recent federal efforts to do away with regulations aimed at improving air quality could reverse the mortality and health gains shown in the report, Cromar said.
“We see the National Highway Traffic Safety Administration (NHTSA) rolling back fuel efficiency standards and the EPA rolling back CO2 standards, along with the repeal of the Clean Power Plan and the introduction of the Affordable Clean Energy Act, which is much less effective in reducing air pollution,” he said. “All of these actions, taken together, are moving us in the wrong direction.”
Cromar noted that the latest version of the report is the first to examine air quality-related health trends over time.
The researchers analyzed daily air pollution (PM2.5 and ozone) values obtained from the EPA Air Quality System for monitors in the U.S. for each year from 2008 to 2017.
These values were used to create annual baseline and control datasets using a 24-hour metric for PM2.5 and three separate metrics — 1-hour maximum, 8-hour maximum, and 24-hour mean — for ozone, with baseline values equivalent to the rolling 3-year design values for each monitor.
“These design values correspond to the 3-year average of the annual mean concentration for PM2.5; the 3-year average of the 24-hour 98th percentile value for PM2.5; and the 3-year average of the fourth highest daily 8-hour maximum O3 concentration,” the researchers wrote. “Control values were based on ATS recommendations of 11 μg/m3 for annual PM2.5, 25 μg/m3 for 24-hour PM2.5, and 60 ppb for O3.”
The recommended cutoffs were lower than the existing National Ambient Air Quality Standards (NAAQS) of 12 μg/m3 for annual PM2.5, 35 μg/m3 for 24-hour PM2.5, and 70 ppb for ozone.
“The ATS-recommended levels used in this analysis are in accordance with previous ATS publications, which find that existing NAAQS are insufficient in protecting human health and emphasize the need for more health-protective regulations,” Cromar and colleagues wrote.
Concentration-response relationships from epidemiological studies, based on EPA standard health functions, were used to calculate mortality impacts of pollution levels above ATS recommendations for each county.
According to the analysis, deaths from air pollution levels greater than the ATS recommendations decreased from approximately 12,600 (95% CI 5,470-21,040) in 2010 to 7,140 (95% CI 2,290-14,040) in 2017.
Also, mortality related to PM2.5 decreased from approximately 8,330 annually to 3,260 annually over the same period, while the ozone-related mortality rate did not change significantly.
Of the 530 counties with valid PM2.5 design values, only 78 (15%) did not meet ATS-recommended concentrations; while 599 (83%) of the 726 counties with valid ozone design values did not meet ATS recommendations.
“There has been real improvement in terms of health impact for particulate matter, but when we look at the health impact for ozone we really haven’t seen a significant trend toward improvement in any part of the U.S.,” Cromar said. “This is an issue that is not going away on its own. And when we look at the numbers we see important health impacts from exposure to ozone pollution.”
He added that while air quality needs to be addressed at the local and state level, as well as by federal officials, federal regulation is the most effective and efficient path to lowering air pollution levels.
“If the EPA and the federal government elect not to take advantage of opportunities, or, worse yet, roll back effective regulations, that will require cities and states to act to improve their air quality,” he said. “Their only options are less efficient ways of addressing air quality that are also much more costly.”
The report was funded by the American Thoracic Society and the Marron Institute of Urban Management at New York University.