New research shows that teenagers who grow up in heavy air pollution have reduced lung capacity, putting them at risk for illness and premature death as adults.
In the longest study to date of pollution's impact on developing lungs, University of Southern California researchers followed children raised in communities around Los Angeles _ some very polluted, some not _ for eight years.
They found about 8 percent of 18-year-olds had lung capacity less than 80 percent of normal, compared with about 1.5 percent of those in communities with the least pollution.
``What they found here, until they find otherwise, I would expect would apply to other cities,'' said Patrick Breysse, director of the Division of Environmental Health Engineering at Johns Hopkins Bloomberg School of Public Health. He was not involved in the study.
The effects were the same for boys or girls, and whether or not the children had asthma or smoked.
``We're seeing air pollution effects on all kids, not just sensitive subpopulations,'' said lead researcher James Gauderman, associate professor of preventive medicine at USC's Keck School of Medicine.
The study was reported in Thursday's edition of the New England Journal of Medicine.
The researchers studied 1,759 children in 12 Southern California communities from spring 1993 through spring 2001, testing their lung capacity annually between ages 10 and 18, when lungs grow substantially and reach full capacity.
Meanwhile, monitoring stations in each community collected continuous data on levels of several common pollutants spewed from car and truck exhaust pipes, factories and power plants.
Reduced lung function was linked to high levels of nitrogen dioxide, vapor containing nitric acid and other acids, and carbon contained in the tiniest particles of soot, which can penetrate deep into the lungs. The U.S. Environmental Protection Agency recently set new standards limiting emissions of such fine particles, which are about one-30th the width of a human hair.
Ozone, which is found at lower levels indoors than the other pollutants, did not appear to affect lung capacity.
The Los Angeles metro area has the country's worst year-round fine particle pollution, and Bakersfield, Fresno and other California cities also are among the 10 worst, according to the American Lung Association. Other metropolitan areas on that list include Pittsburgh, Detroit, Atlanta, Cleveland and Birmingham, Ala.
The lung capacity of children raised in the most-polluted communities grew by about 100 milliliters less over the eight years, compared to children in the least-polluted areas, said lead researcher James Gauderman, associate professor of preventive medicine at USC's Keck School of Medicine.
That's about 7 percent reduced lung capacity for girls, ``a fairly significant amount,'' Gauderman said. For boys, who normally can inhale and exhale about one-third more air than girls, capacity was reduced about 4 percent.
``They may not notice it today because at age 18 these kids are at their peak lung capacity,'' Gauderman said, but they could develop health problems in their 40s and 50s.
He thinks the pollutants limit breathing capacity by causing chronic inflammation in the small airways deep in the lungs.
The worst cities studied, Gauderman said, were near Los Angeles: Long Beach, Mira Loma, Riverside, San Dimas and Upland.
The results are similar to findings announced four years ago but go beyond it in showing that pollution's effects are cumulative. No children with lung problems in the first four years appeared to improve later, noted Gauderman. He and his colleagues are continuing to follow the teens to see if any develop lung-related health problems.
John Bachmann, associate director of science policy in the EPA's Air Office, said the ``very well-conducted study'' shows ``that particular mix of pollutants has serious long-term effects in children.''
He noted earlier research _ mostly on people with asthma and other lung problems _ suggesting long-term exposure to air pollution leads to earlier death. Bachmann said the new research improves on earlier work by studying a mix of common pollutants rather than one and by including some not routinely measured, such as carbon particles.
``It's a reason to keep working hard on air pollution,'' said Bachmann. ``This kind of study contributes to our understanding of how far we need to go.''
Besides the new particle standards, EPA is making power plants cut levels of smog-causing nitrogen dioxide by 40 percent by 2015. Some environmental groups argue the agency isn't doing enough to prevent thousands of deaths annually from air pollution.
The Clean Air Act and other pollution laws enacted since 1967 ended most ``extremely severe episodes of air pollution'' in the United States, C. Arden Pope III of Brigham Young University wrote in an editorial in the journal. However, there's growing evidence that fine particles coated with acids, metals and other contaminants increase risk of heart and respiratory disease and death.
``Decreasing these concentrations offers substantial opportunities for disease prevention,'' Pope wrote.
In the meantime, Breysse, the Johns Hopkins professor, urged children and adults to limit time working and exercising outdoors on days when air pollution is high.
``People tend to think air pollution is sort of a nuisance, that it's benign,'' he said, ``but it's a serious public health problem.''