Reducing pollution produces measurable health gains, according to a new study that found cleaner air had lengthened life expectancy by five months in 51 US cities.
Researchers at Brigham Young University and Harvard School of Public Health found that average life expectancy increased by three years between 1980 and 2000 in those cities, and that approximately five months of that gain owed to cleaner air.
"Such a significant increase in life expectancy attributable to reducing air pollution is remarkable," said C. Arden Pope III, a BYU epidemiologist and lead author on the study, published in the New England Journal of Medicine.
"We find that we're getting a substantial return on our investments in improving our air quality. Not only are we getting cleaner air that improves our environment, but it is improving our public health."
The researchers compared data in 51 US cities on changes in air pollution between those 20 years and the life expectancies of residents during those years.
They applied advanced statistical models to account for other factors possibly affecting life spans, such as changes in demographics, income, migration, population, education and cigarette smoking.
Cities that had previously been the most polluted and saw the most extensive clean-ups added an average 10 months to residents' lives.
By the end of the study period, life expectancy had increased by 2.72 years in the cities studied, with up to five months, or 15 percent of that gain owing to reduced air pollution.
Other studies have shown that these gains probably owe to a decrease in cardiovascular and cardiopulmonary diseases often linked to air pollution.
Pope and study co-author Douglas Dockery of Harvard teamed up with other researchers on studies published in the early 1990s that found that "PM2.5", pollutants less than 2.5 microns in diameter, had negative health effects.
The Environmental Protection Agency (EPA) used those and other studies as a basis to tighten air pollution standards in 1997.
Analysis in the latest study found that for every decrease of 10 micrograms per cubic meter of particulate pollution in a city, the average life expectancy of residents in the city grew by more than seven months.
The average PM2.5 levels in the 51 cities studied dropped from 21 to 14 micrograms per cubic meter during the 1980s and 1990s. Health gains were also found in cities that initially had relatively clean air but then made further improvements in reducing air pollution.
"There is an important positive message here that the efforts to reduce particulate air pollution concentrations in the United States over the past 20 years have led to substantial and measurable improvements in life expectancy," Pope said.
The study was financed by the EPA, the Centers for Disease Control and the National Institute of Environmental Health Sciences, among others.