Small amounts of air pollution linked to more death for senior citizens

'Safe'levels?

Brian Bienkowski for Environmental Health News

Elderly people have a higher risk of dying after short-term exposure to particulate air pollution and ozone, according to a new study from Harvard.

The levels of pollution linked to premature deaths were below current U.S. health standards set by the Environmental Protection Agency—and the impacts were disproportionately worse for the poor, women and black people.

The study is the "most comprehensive study of short-term exposure to pollution and mortality to date," said senior author of the study, Francesca Dominici, a professor of biostatistics and co-director of the Harvard Data Science Initiative.

"We wanted to know if air pollution at levels well below safety standards set by the EPA is possibly increasing mortality," she said. "The answer is yes."

Dominici and colleagues looked at daily levels of particulate matter 2.5 micrometers or less in diameter (PM 2.5) and ozone across the U.S. They compared the levels with deaths from people on Medicare from 2000 to 2012.

For each 10 microgram per cubic meter daily increase in PM2.5 and each 10 parts per billion daily increase in ozone during warm months, the daily mortality rate increased by 1.05 percent and 0.51 percent, respectively. 

During the study time, about 22 million people in the Medicare population died.

The risk was the same across the country: "No matter where you live—in cities, in the suburbs, or in rural areas—as long as you breathe air pollution, you are at risk," said lead author Qian Di, a PhD student in Harvard's Department of Environmental Health, in a statement.

For low-income people (measured in the study as those qualifying for Medicaid) deaths linked to PM 2.5 increases were three times higher than those not eligible for Medicaid.

Women and people of color had a 25 percent higher death risk from the pollution than white men.

Dominici said they aren't sure why women would have such a higher risk, but said people of color and those eligible for Medicaid, in general, have a higher risk of mortality and "tend to have less access to health care systems," she said, offering one reason for the disproportionate impact.

Past studies have shown similar links between air pollution and death but used air monitoring by the EPA to estimate exposure levels. Dominici said they used multiple sources to model air pollution—including satellite data. "By doing so we were able to include in our study 93 percent of all zip codes [in the U.S]," she said. "Previous studies were using a much smaller sample."

The research doesn't prove air pollution caused more deaths and it was limited in that the study did not examine links between long-term air pollution exposure and death. The researchers also didn't know cause of death, so they can't be sure pollution played a role.

However, in multiple studies air pollution has been linked to a host of health problems, including respiratory disease, heart problems, and, more recently, decline in brain function.

And the risks in this study "occurred at levels below current national air quality standards, suggesting that these standards may need to be reevaluated," the author wrote.