BOSTON, Jan. 31 (AP) — The fine grit in polluted air increases the risk of heart disease in older women much more sharply than scientists realized, a federally financed study has found, raising questions of whether environmental standards are strict enough.
The Environmental Protection Agency tightened its daily limit for the tiny specks, or fine particulates, in September.
But the new standard left the average annual limit untouched, allowing a concentration of 15 millionths of a gram for every cubic meter of air.
In this study of 65,893 women, the average exposure was 13 millionths, with two-thirds of the subjects falling under the national standard.
But every increase of 10 millionths, starting at zero, increased the risk of fatal cardiovascular disease by about 75 percent. That is several times higher than in a study by the American Cancer Society.
“There was a lot of evidence previously suggesting that the long-term standard should be lower, and this is adding one more study to that evidence,” said Douglas Dockery, a pollution specialist at the Harvard School of Public Health.
Dr. Dockery wrote an accompanying editorial for the study, which is in the Thursday issue of The New England Journal of Medicine.
The researchers, based at the University of Washington, worked from data collected for the Women’s Health Initiative, a research project that previously showed the heart dangers of hormone supplements.
It has long been known that particulates can contribute to lung and heart disease, with women perhaps more susceptible than men to heart problems, perhaps because of their smaller blood vessels and other biological differences.
But the degree of risk for older women was less clear. This study started with women who had gone through menopause and were 50 to 79 years old.
Unlike earlier studies, it looked not just at deaths, but also at heart attacks, coronary disease, strokes and clogged arteries.
Those problems were 24 percent more likely with every 10-unit increase in particles. Almost 3 percent of the women had some kind of cardiovascular problem.
The risk varied along with the varying levels of these particles in different neighborhoods in the same city.
In their calculations, the researchers tried to adjust for lower income and other health problems that have been blamed for the higher rates of disease in past studies.
“I think the major contribution is answering the critics of the prior studies,” said the paper’s senior researcher, Dr. Joel Kaufman of the University of Washington.
“The effect,” Dr. Kaufman said, “seems large and important and should be taken seriously.”
States and other groups demanding a lower annual standard sued the E.P.A. last year, accusing it of disregarding the advice of its own scientists. Some agency scientists are also pushing for tighter rules on ozone, the chemical that creates smog and contributes to asthma and lung disease. The E.P.A. is scheduled to take another look at its standard for particulate matter and finish it by 2011.
The grit is thought to reach deep into the lungs to spur inflammation that leads to heart attack and stroke. It would take about 30 particles to equal the thickness of a human hair.
The particles, made of dust, soot and various chemicals, come from burning fuel in cars, factories and power plants. While individual particles are too small to see, they can be observed collectively as urban haze.
