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Exposure to PM2.5, Ozone at Low Levels Linked to Mortality

WEDNESDAY, Dec. 27, 2017 -- Short-term exposure to ambient fine particulate matter (PM2.5) and warm-season ozone at levels below current national air quality standards is associated with increased risk of mortality in the U.S. Medicare population, according to a study published in the Dec. 26 issue of the Journal of the American Medical Association.

Qian Di, from the Harvard T.H. Chan School of Public Health in Boston, and colleagues examined the correlation between short-term exposure to PM2.5 or ozone at levels below National Ambient Air Quality Standards and mortality in the United States. The entire Medicare population from Jan. 1, 2000, to Dec. 31, 2012, was included.

The researchers found that 93.6 percent of all case and control days had PM2.5 levels below 25 µg/m³, during which time 95.2 percent of deaths occurred; 93.4 percent of deaths occurred during the 91.1 percent of days that had ozone levels below 60 parts per billion. For the entire year and warm season, the baseline daily mortality rates were 137.33 and 129.44 per one million individuals at risk, respectively. There were statistically significant associations for each short-term increase of 10 µg/m³ in PM2.5 and 10 parts per billion in warm-season ozone with a relative increase of 1.05 and 0.51 percent in daily mortality rates, respectively. Per one million individuals at risk per day, the absolute risk differences in daily mortality rates were 1.42 and 0.66, respectively.

"In the U.S. Medicare population from 2000 to 2012, short-term exposures to PM2.5 and warm-season ozone were significantly associated with increased risk of mortality," the authors write. "This risk occurred at levels below current national air quality standards, suggesting that these standards may need to be reevaluated."

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Posted: December 2017