Breathing polluted air is bad for you, and some research has suggested that children who grow up in polluted areas have less well-developed lungs. Researchers in California looked at how pollution affects kids' lungs between ages 10 and 18, a time when lungs grow and develop rapidly.

What the researchers wanted to know: Does air pollution affect lung development?

What they did: The Children's Health study recruited 1,759 fourth graders from 12 communities in Southern California, from relatively clean-aired Lompoc to more heavily polluted Long Beach and Mira Loma. The children had their lung function tested every year from 1993 to 2001, by technicians who traveled from school to school. Starting in 1994, the researchers also collected continuous data in each community on the levels of ozone, nitrogen dioxide, particulates, and other pollutants.

What they found: Children who were exposed to more air pollution had less-developed lungs. That was true whether or not children had asthma or smoked. The lungs of children in polluted areas developed about as poorly as the lungs of children whose mothers smoke, as reported in other studies.

What the study means to you: Lung development is greatest at ages 10 to 18, the ages of the children in this study; girls' lungs are basically done developing at age 18, while boys' might keep developing into their early 20s. So that means these lung deficits are probably permanent—and could lead to health problems later.

Caveats: The study lost about 10 percent of children each year (most because they moved away), but the researchers say there's no reason to think that the children who left would have had different lung development than the children who stayed. Also, while they adjusted for a lot of variables, such as whether people around a child smoked, it's possible they missed some confounding variable.

Find out more: The California Air Resources Board has a website on the Children's Health Study, where you can see a map of the communities studied and read the final study report.

Read the article: Gauderman, W.J. et al. "The Effect of Air Pollution on Lung Development from 10 to 18 Years of Age." New England Journal of Medicine. Sept. 9, 2004, Vol. 351, No. 11, pp. 1057–67.

Abstract online: http://content.nejm.org