CHARLESTON, W.Va. - Cleaner air over the last two decades has added nearly five months to the average American life expectancy, according to a first-of-its-kind study published this week.

But parts of the country that haven't cut pollution as much - including the Kanawha Valley - have lagged behind the national life-span gain, according to the study published in Thursday's New England Journal of Medicine.

"Communities that had larger reductions in air pollution had larger increases in life expectancy," said C. Arden Pope, a Brigham Young University epidemiologist and lead author of the study.

For years, scientists have reported that air pollution is linked to a variety of ailments that cause premature death.

Researchers at Brigham Young and Harvard University took a different approach. They compared pollution cuts since the 1970s to improved life expectancy numbers.

They found that, between 1978 and 2001, Americans' average life span increased almost three years to 77. As much as 15 percent of that - or 4.8 months - could be attributed to cleaner air, study concluded.

"Such a significant increase in life expectancy attributable to reducing air pollution is remarkable," Pope said in a prepared statement. "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 new study focused on levels of particulate matter: very small bits of dust and droplets made up of a variety of acids, organic chemicals, metals and soil. Scientists have long know that particulates can lodge deep in the lungs, and raise the risk of lung disease, heart attacks and strokes. Particular matter comes from factories, power plants and motor vehicles.

In their study, scientists used government data to track particulate levels over two decades in 51 U.S. metropolitan areas. With death records and Census data, they compared these changes to life expectancies. Researchers also adjusted the results to take into account smoking and other factors that might affect the life expectancy figures.

CHARLESTON, W.Va. - Cleaner air over the last two decades has added nearly five months to the average American life expectancy, according to a first-of-its-kind study published this week.

But parts of the country that haven't cut pollution as much - including the Kanawha Valley - have lagged behind the national life-span gain, according to the study published in Thursday's New England Journal of Medicine.

"Communities that had larger reductions in air pollution had larger increases in life expectancy," said C. Arden Pope, a Brigham Young University epidemiologist and lead author of the study.

For years, scientists have reported that air pollution is linked to a variety of ailments that cause premature death.

Researchers at Brigham Young and Harvard University took a different approach. They compared pollution cuts since the 1970s to improved life expectancy numbers.

They found that, between 1978 and 2001, Americans' average life span increased almost three years to 77. As much as 15 percent of that - or 4.8 months - could be attributed to cleaner air, study concluded.

"Such a significant increase in life expectancy attributable to reducing air pollution is remarkable," Pope said in a prepared statement. "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 new study focused on levels of particulate matter: very small bits of dust and droplets made up of a variety of acids, organic chemicals, metals and soil. Scientists have long know that particulates can lodge deep in the lungs, and raise the risk of lung disease, heart attacks and strokes. Particular matter comes from factories, power plants and motor vehicles.

In their study, scientists used government data to track particulate levels over two decades in 51 U.S. metropolitan areas. With death records and Census data, they compared these changes to life expectancies. Researchers also adjusted the results to take into account smoking and other factors that might affect the life expectancy figures.

Particular matter levels fell on overage from 21 micrograms per cubic meter of air to 14 micrograms per cubic meter of air. At the same time, Americans lived an average of 2.72 years longer.

But in the Charleston area, particulate pollution levels dropped by only 4.3 microns per cubic meter, compared to the national average of 6.52 microns.

And, the Charleston-area life expectancy increased by 1.9 years, compared to the national average of 2.72 years.

"Charleston's improvement in life expectancy was less than average, while it's air quality improvement was also relatively poor," said Michael Hendryx, a West Virginia University researcher who is studying pollution impacts on the state's health. "The authors show that air quality improvements increase life expectancy, and so for Charleston that means we should be concerned about our air quality and work to improve it."

John Benedict, director of the state Department of Environmental Protection's Division of Air Quality said he believes the Kanawha Valley has show a "fairly marked improvement" in its air quality.

"We had some serious air quality problems in the 1970s, and we've seen a steady decline in the concentrations of a variety of air pollutants since then," Benedict said Thursday.

But last month, the U.S. Environmental Protection Agency placed the Charleston area on its list of areas that are not meeting a new EPA limit for very small particulate pollution. State officials will have three years to come up with a plan to meet the new standard.

"We recognize we've got some work to do," Benedict said. "We'll be moving forward with those plans."

Reach Ken Ward Jr. at kw...@wvgazette.com

or 304-348-1702