'Air pollution may increase premature death risk in elderly'

Short-term exposure to fine particulate air pollution and ozone - even at low levels - may increase the risk of premature death in the elderly, a US study warns.

The study published in the Journal of the American Medical Association (JAMA) found that the risk was even higher among elderly who were low-income, female, or non- white people.

"This the most comprehensive study of short-term exposure to pollution and mortality to date," said Francesca Dominici, a professor at Harvard T H Chan School of Public Health in the US.

"We found that the mortality rate increases almost linearly as air pollution increases. Any level of air pollution, no matter how low, is harmful to human health," said Dominici.

"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 Qian Di, lead author of the study and a PhD student at Harvard T H Chan School of Public Health.

Under the National Ambient Air Quality Standards (NAAQS) set by the US Environmental Protection Agency (EPA), long-term exposures to PM2.5 are considered safe if they average 12 microgrammes per cubic meter of air or less per day over the course of a year, researchers said.

They assessed daily air pollution exposures using prediction models that provided accurate estimates of PM2.5 and ozone for most of the US, including unmonitored areas.

The researchers then linked the air pollution data with mortality data from the entire US Medicare population residing in 39,182 zip codes (93 percent of all the zip codes in the US), over a 13-year period from 2000-2012.

During the study period, 22 million people in the study population died researchers said.

The study found that, for each 10 microgrammes per cubic meter daily increase in PM2.5 and 10 parts per billion (ppb) daily increase in warm-season ozone, the daily mortality rate increased by 1.05 percent and 0.51 percent, respectively.

While this may seem a small increase, the public health impact is enormous if it is applied to the whole US population of seniors, researchers said.

Certain subgroups were particularly vulnerable to short-term air pollution.

Among Medicaid-eligible (low income) recipients, the mortality increase linked with increased PM2.5 was three times higher than that of people not eligible for Medicaid.

Women and non-whites also faced a mortality risk that was 25 percent higher than those who were male or white, researchers said.