Researchers looked at concentrations of fine pollution particles known as PM2.5 across the country from 1999 to 2015. These tiny particles — 30 times smaller than the width of a human hair — come from the combustion of cars, coal-fired power plants and other industrial sources.
When these particles are inhaled, they lodge in the small blood vessels in the lungs, and can over time cause lung disease. The particles also find their way into the bloodstream, where they raise the risk for heart attack and stroke, the researchers added.
“More stringent air pollution regulations in the U.S. have the potential to save tens of thousands of deaths each year and improve the longevity throughout the country,” said lead researcher Majid Ezzati, chair of environmental health at the School of Public Health at Imperial College London.
Although PM2.5 levels have dropped overall since 1999, levels in many areas remain high, the researchers found.
And for the year 2015, the researchers extrapolated that air pollution still caused nearly 16,000 deaths in women and 15,000 in men in the United States.
These deaths were due to heart attacks and respiratory diseases such as asthma.
The deaths resulted in a lower life expectancy for both men and women, the researchers noted. Drops in life expectancy due to air pollution were seen in Los Angeles and some Southern states, including Alabama, Arkansas and Oklahoma.
Shortened life expectancy was highest in places where poor people lived and lowest in wealthy areas.
The acceptable PM2.5 level, set by the U.S. Environment Protection Agency, is 12 micrograms per cubic meter of air (ug/m3).
In 1999, the highest levels of PM2.5 were in Fresno County, Calif., at 22.1 ug/m3. By 2015, the highest levels were in Tulare County, Calif., at 13.2 ug/m3.