If the air in your city is clean, you can tack on about five months to your life. So suggests a new study by researchers at Brigham Young University and Harvard School of Public Health.
This study found that the average life expectancy in 51 cities in the United States increased by nearly three years in recent decades and that approximately five months of that increase came as a result of cleaner air.
"Life expectancy is a well-understood indicator for public health," said C. Arden Pope III, a Brigham Young University epidemiologist and lead author on the study in the Jan. 22 issue of the New England Journal of Medicine. "We find that we are getting a substantial return on our investments in improving our air quality."
Pope is no stranger to this issue. He and co-author Douglas Dockery, chair of the Department of Environmental Health at Harvard School of Public Health, teamed up with other researchers on important studies in the 1990s that revealed the negative health effects of infinitesimally small particles of pollution.
So small are these particles, known as "PM2.5," that you would have to line up 25 of them end to end to span the width of a human hair. The danger of these tiny particles is that they can find their way deep into the respiratory system when inhaled.
Dr. Joel Schwartz, an environmental epidemiologist at the Harvard School of Public Health, agreed that the research "suggests that there is a phenomenon in the United States regarding increase in air pollution and shortened life span that is greater than the six locations studied in [previous research]."
The U.S. Environmental Protection Agency tightened air pollution standards in 1997 based on earlier data. But the new research suggests that it may be time to tighten these standards even further.
"This is a compelling paper," said Dr. David Peden, chief of pediatric immunology at the University of North Carolina at Chapel Hill. "The results speak to the need for better standards from the U.S. Environmental Protection Agency."
And now that the new research attaches a specific benefit in terms of life span, curbing air pollution could garner more attention from the general public.
"This study certainly confirms an association between air pollution and bad health, which has been suggested by other studies," Pope said. "What is unique is that the increase in life expectancy suggested by the results [in our study] was larger and more robust than originally thought."
Specifically, the study concluded that for every decrease of 10 micrograms per cubic meter of particulate pollution in a city, its residents' average life expectancy increased by more than seven months. For this effect to be seen in Atlanta, for example, its current level of pollution would have to drop from about 18 micrograms per cubic meter to 8 micrograms per cubic meter.
Overall, it appears that we have made progress in improving air pollution levels. The study states that during the 1980s and 1990s the average PM2.5 levels in the 51 U.S. cities studied dropped from 21 to 14 micrograms per cubic meter.
But Pope said there is still room for improvement.
"There is more work to do," Pope said. "Further studies can build on this data and look at changes in air pollution after 1999 when levels were monitored closely."