Cuts in air pollution increased life expectancy an average of five months in Boston and dozens of other American cities in recent decades, a study from Harvard and Brigham Young universities strongly suggests.
The researchers looked at the amount of small-particle pollutants in 51 US cities - including Boston, Worcester, Springfield, and Providence - during the 1980s and '90s and found that the predicted lifespan increased most significantly in cities where air quality increased most dramatically.
The study, which appears in today's New England Journal of Medi cine, signals that efforts to curtail the small, toxic particles spewed by power plants, factories, cars, and trucks and inhaled by city-dwellers had significant health benefits over those two decades. Several clean-air advocates and public health specialists said the results show that even stronger standards for air pollutants are needed.
"We had known with reasonable confidence for a while now that air pollution is bad for people's health," said Majid Ezzati, a professor at the Harvard School of Public Health and one of the study's authors. "The question still lingering was: Does lowering pollution have health benefits? The answer is yes."
Boston's share of fine particulate matter - solid particles 30 times smaller in diameter than a human hair - decreased about 7 micrograms per cubic meter of air between 1980 and 2000. That reduction was close to the average among cities evaluated across the nation. Life expectancy in Boston increased by more than three years during that time period, about five months of which the researchers found could be attributed to cleaner air.
Other factors that have improved the predicted lifespan in recent decades range from medical advances, education, and income growth to changes in lifestyle, including healthier eating habits and quitting smoking.
Life expectancy does not directly indicate how long people live. Rather, it predicts how long the average person in a population would live if the death rate at a given time persisted for the person's lifetime.
Kirk Smith, a professor of environmental health at the University of California at Berkeley, who was not affiliated with the study, said the study helps to confirm that air pollution is harmful. "It adds another nail in the coffin that particulate air pollution has a significant impact on health," Smith said.
Over the past few decades, a large body of research has shown that when people inhale the tiny particles in air pollution, that foreign matter inflames lung tissue and increases the plaque that forms in arteries, contributing to heart and lung disease.
Daniel Greenbaum, president of the Health Effects Institute, a scientific research group based in Boston that evaluates studies about air pollution and health, said that New England "is fortunate to not have particulate matter levels as high as the rest of the country." But, he added, as the population ages over the coming decade, more people could become vulnerable to health problems from air pollutants.
If cleaner air improves predicted lifespan, life expectancy has probably further increased in many parts of the nation during the past decade. Since 2000, air monitoring data show that the national average concentration of fine particles has decreased 11 percent, said Cathy Milbourn, spokeswoman for the US Environmental Protection Agency.
Still, clean-air advocates and some public health specialists said that the Bush administration did not do enough to decrease small-particle pollution.
According to the Clean Air Task Force, a Boston-based nonprofit, 24,000 people each year die as a result of fine particle pollutants from power plants in the United States, and 21,000 people each year die from diesel exhaust particles. While the Bush administration carried forth rules passed under President Clinton that require new diesel engines to lower small-particle pollution significantly, the rules do not apply to most of the 11 million diesel engines in the United States, said Conrad Schneider, advocacy director for the task force.
The group is calling for the Obama administration to support large incentives to retrofit current diesel engines - a measure included in the economic stimulus bill - and to issue new rules to regulate power-plant emissions of particulates and carbon dioxide, the key contributor to global warming.
Bina Venkataraman can be reached at email@example.com.