Children who live in polluted communities are five times more likely to have clinically low lung function — less than 80 percent of the lung function expected for their age. New data from the Children's Health Study suggests that pollutants from vehicle emissions and fossil fuels hinder lung development and limit breathing capacity for a lifetime.

The study was funded by the National Institute of Environmental Health Sciences (NIEHS), one of the National Institutes of Health, the California Air Resources Board and the Hastings Foundation. The results of the study, conducted by researchers at the University of Southern California Keck School of Medicine, are published in this week's issue of the New England Journal of Medicine.

"This is the longest study ever conducted on air pollution and children's health," said Dr. Kenneth Olden, director of NIEHS. "It shows that current levels of air pollution have adverse effects on lung development in children between the ages of 10 and 18."

Each year, pulmonary function data were collected from 1,759 children as they progressed from 4th grade to 12th grade. The researchers also tracked levels of air pollutants like nitrogen dioxide, acid vapor, elemental carbon, and particulate matter in the 12 Southern California communities where the children lived. The study encompassed some of the most polluted areas in the greater Los Angeles basin, as well as several less-polluted communities outside the Los Angeles area.

Over the eight year period, researchers found that children living in the most polluted communities had significant reductions in their "forced expiratory volume" — the volume of air that can be exhaled after taking a deep breath — as compared to children living in communities with cleaner air.

In healthy people, lungs grow to full capacity during the teenage years, but typically stop growing at age 18. Then, lung capacity gradually declines. Adults begin to lose lung function by 1 percent each year after age 20.

"Lung development in teenagers determines their breathing capacity and health for the rest of their lives," said John Peters, M.D., Hastings Professor of Preventive Medicine at the Keck School of Medicine. "The potential long-term effects of reduced lung function are alarming. It's second only to smoking as a risk factor for mortality. As lung function decreases, the risk of respiratory disease and heart attacks increases."

Deficits in lung function are associated with other short- and long-term effects. "If children or young adults with low lung function were to have a cold, they might have more severe lung symptoms, or wheezing," says W. James Gauderman, Ph.D., associate professor of preventive medicine at the Keck School and lead author on the study. "They may have a longer disease course, while children with better lung function may weather it much better."

Researchers are unsure how air pollution may retard lung development. Gauderman believes chronic inflammation may play a role, with air pollutants irritating small airways on a daily basis. Scientists also suspect that air pollutants might dampen the growth of alveoli, tiny air sacs in the lungs.

The research team will continue to follow the study participants into their early 20s, when their lungs will be fully mature. They want to find out whether the participants will experience respiratory symptoms, and if those who moved away from a polluted environment will show some improvement in lung function.

This research is part of the larger Children's Health Study, an ongoing study that was started in 1993. The study is the longest ever undertaken on the association between air pollution and children's health.