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 Researchers looked at 22 million deaths nationwide to see if there
was any connection between fatalities and fluctuations in daily
concentrations of ozone, an unstable form of oxygen produced when
pollution reacts with sunlight, and so-called PM 2.5, tiny particles
that include dust, dirt, soot and smoke.
Most of the deaths in the study occurred on days when ozone and PM
2.5 levels were below the limits set by the U.S. Environmental
Protection Agency (EPA).
Previous studies have linked air pollution to an increased risk of
chronic health problems and premature death, but those studies
focused on cities, said study co-author Joel Schwartz of the Harvard
T.H. Chan School of Public Health in Boston.
“So we did not know if the same association held in small cities,
towns, or rural areas,” where pollution levels are lower, Schwartz
said by email. “Now we have them all, so we know that it does apply
everywhere, not just in big cities.”
The study focused on deaths from 2000 to 2012 for people in more
than 39,000 ZIP codes nationwide who were insured by Medicare, the
U.S. health program for the elderly and disabled.
Researchers compared satellite data on daily PM 2.5 and ozone levels
on the days people died in specific ZIP codes to air quality levels
on another day within a week or two of each fatality.
EPA standards cap 24-hour PM 2.5 at 35 micrograms per cubic meter of
air (ug/m3) and 8-hour ozone at 70 parts per billion (ppb).
During all of the days examined in the study, 94 percent had PM 2.5
levels below 25 ug/m3, and 95 percent of the deaths occurred on
these days, the study found.
At the same time, 91 percent of the days examined had ozone levels
below 60 ppb, and 93 percent of the deaths occurred on these days.
Even when air quality still met EPA standards, each 10 ug/m3 daily
increase in PM 2.5 levels was associated with an increase of 1.42
deaths per day for every million people, the researchers report in
the Journal of the American Medical Association. Each 10 ppb
increase in daily ozone levels was associated with 0.66 more deaths
for every million people.
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The increased risk of death associated with daily spikes in PM 2.5
and ozone levels persisted even when researchers restricted their
analysis to days when the air quality complied with EPA standards.
Among other things, breathing polluted air can worsen existing
respiratory conditions, such as asthma or chronic obstructive
pulmonary diseases, said Griffith Bell, a researcher at the Eunice
Kennedy Shriver National Institute for Child Health and Human
Development in Bethesda, Maryland.
“In children or young people, these exacerbations might not have
serious consequences, but in the elderly and the very ill, who may
already have difficulty breathing, breathing very polluted air might
push them over the edge,” Bell, who wasn’t involved in the study,
said by email.
Beyond a lack of data on young people, another limitation of the
study is the lack of data on the long-term air pollution exposure,
the authors note.
Still, people should be aware of the health effects of air pollution
even when they don’t live in urban areas where traffic and smog may
be well-known health risks, said Junfeng Zhang, author of
accompanying editorial and an environmental health researcher at
Duke University in Durham, North Carolina.
“Even those who live in rural areas with relatively low air
pollution levels can get higher exposures on days when the regional
air pollution levels are higher due to bad weather conditions or
during a fire,” Zhang said by email. “They can also get higher
exposures by spending time near roadways or diesel-powered
equipment, and they can get higher exposures while driving.”
SOURCE: http://bit.ly/2BYt3zQ JAMA, online December 26, 2017.
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