Even brief exposure to low air pollution tied to deaths

Older adults are more likely to die on days when air pollution rises, even when contaminant levels are below the limit considered safe by U.S. regulators, a new study suggests.

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).

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.?