Researchers who compared data from 545 counties across the U.S. found that a drop in fine particulate matter, known as PM2.5, between 2000 and 2007 corresponded with an average rise in life expectancy of 0.35 of a year.
The study, led by researchers at the Harvard School of Public Health, is described as the largest to date to find public health benefits from ongoing reductions in U.S. air pollution levels.
Fine particles, which are about 1/30th the average width of a human hair, come from a variety of sources, including vehicles, smokestacks and fires. They also form when gases emitted by power plants, industry and vehicle engines react in the atmosphere.
The tiny particles can lodge deeply in the lungs, aggravating heart and lung diseases. Those most at risk include people who are active outdoors, children and the elderly.
Nationally, average concentrations of particulate matter, both fine and coarse, have fallen over the years. The researchers wanted to know whether the relatively smaller decreases in PM2.5 levels since 2000 are still improving life expectancy.
The study, which appeared in Monday's online edition of the journal Epidemiology, controlled for changes in other factors, such as smoking and socioeconomic status. The findings showed that cutting fine particle pollution had the greatest effect on life expectancy in urban areas - possibly because of differences in particle composition. Women also seemed to benefit more than men.
"This study provides strong and compelling evidence that continuing to reduce ambient levels of PM2.5 prolongs life," said co-author Francesca Dominici, professor of biostatistics at the Harvard School of Public Health.
Citing scientific evidence that exposure to particle pollution causes premature death and is linked to a variety of significant health problems, the U.S. Environmental Protection Agency has proposed strengthening air pollution standards for fine particles.
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