February 2, 2009

Cleaner Air May Lengthen Life

Photo of a city shrouded in smog

A 2-decade decline in air pollution in dozens of U.S. cities has added an average of about 5 months to residents’ lives, according to a new study.

Scientists already had ample evidence of the harmful health effects of air pollution. Several studies over the past 40 years have linked increased air pollution to shorter lifespans and higher risks for cardiovascular and lung disease. The new research provides strong support for an opposite, positive effect when air pollution levels drop.

Dr. C. Arden Pope III of Brigham Young University and his colleagues at Harvard School of Public Health focused their attention on fine-particle air pollution, which generally comes from power plants, industry and car exhaust. These fine airborne particles measure up to 2.5 microns in size. That’s about 1/30th the width of a human hair.

The researchers identified 51 city regions where fine-particle air pollution had been measured for several years around the early 1980s and then again about 20 years later, around the early 2000s. The scientists then matched these data to the residents’ life expectancies during those years, which were calculated using mortality statistics and population data. Their research was funded by NIH’s National Institute of Environmental Health Sciences (NIEHS), the U.S. Centers for Disease Control and Prevention, the U.S. Environmental Protection Agency and others.

In the January 22, 2009, issue of the New England Journal of Medicine, the scientists reported that fine-particle air pollution levels dropped in all 51 metropolitan areas during the 20-year study period, and life expectancy rose on average by nearly 3 years. After adjusted for income, education, smoking and other factors that affect longevity, the scientists found that improved air quality accounted for up to 15% of the overall increase in lifespan, or an average gain of 4.8 months of life.

For every decrease of 10 micrograms per cubic meter of fine-particle pollution, the average life expectancy of city residents rose by more than 7 months. Overall, in all 51 cities, particulate air pollution declined by an average of 6.5 micrograms per cubic meter. However, in cities like Pittsburgh and Buffalo, where fine-particle pollution dropped most dramatically—by about 14 micrograms per cubic meter—the improved air quality appeared to boost longevity by nearly 10 months. Even cities that started off with relatively clean air, like Albuquerque, gave residents a modest lift in lifespan when air quality improved slightly during the study period.

“We find that we're getting a substantial return on our investments in improving our air quality,” says Pope. “Not only are we getting cleaner air that improves our environment, but it is improving our public health.”

—by Vicki Contie

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