When children living under polluted, hazy skies move away to communities with cleaner air, their lungs begin to grow more quickly, according to a study by researchers at the Keck School of Medicine of USC.

Preventive medicine researchers followed more than 100 children through their teen years and compared those who stayed in the Los Angeles area to those who moved away to other communities in the West. The resulting changes in air pollution exposure, on average, affected annual rates of lung function growth, the team reported in the December issue of the American Journal of Respiratory and Critical Care Medicine.

"This study confirms our earlier work showing that air pollution can have long-term effects on lung health in children. It also shows that cleaning up the air actually has a measurable effect on children’s health," said Edward L. Avol, associate professor of research in preventive medicine at the Keck School and the study’s lead author.

"On average, children who moved away to areas with lower levels of pollution had increased rates of lung function growth, while children who moved to areas with higher pollution had decreased rates. So, air quality can affect lung growth rates, and reducing community air pollution can make a measurable difference," he said.

The research is part of the USC-led Children’s Health Study, an extensive investigation into pollution and kids’ health. Researchers have tracked levels of major pollutants in 12 Southern California communities since 1993, all while monitoring the pulmonary health of more than 6,000 students in the areas.

This study underscores the group’s earlier findings that high levels of pollution in the air can dramatically slow the healthy growth and development of children’s lungs.

The team studied 110 children who had lived in Southern California in the 1990s but later moved away. Children were first tested at about age 10 in Southern California, then followed up at age 15 – after they had relocated to other communities in California, Oregon, Nevada, Washington, Arizona or Utah.

Researchers tested lung function by having each child take a deep breath, then measuring how much and how fast kids could blow out the air. The more they could blow, the higher the level of lung function.

Researchers found that students who had moved to areas with less particulate matter – microscopic particles in the air such as dust and smoke – showed increased growth in lung function. Those who moved to areas with more particulate matter showed a slowdown in lung function growth. The trend seemed strongest for those who had moved away three years or more before they were tested.

Particulate matter is just one ingredient of the hazy cocktail of airborne pollutants that come from the burning of fossil fuels (the exhaust from a car or truck, for example), as well as from emissions from factories or other sources. Scientists suspect that children with decreased lung function might be more susceptible to respiratory disease and more likely to have chronic respiratory problems as adults.

Millions of Southern Californians breathe polluted air every day, and pollution levels exceed federal and state standards for air quality in several areas of Los Angeles. Although polluted air is known to cause immediate discomfort such as eye irritation, coughing and chest tightness, long-term effects have been less clear.

Researchers were also interested in lung function during adolescence, when lungs grow quickly.

"Girls’ lungs grow until their late teens, and boys’ lungs until their early 20s," Avol explained. "Lung function typically peaks in the 20s, and then slowly declines with age. So what happens during that big growth spurt during the teen years may be especially important later in life."

Avol and colleagues hope to follow the children as they progress into adulthood.

The study was supported by grants from the U.S. EPA, the California Air Resources Board, the National Institute for Environmental Health Sciences and the Hastings Foundation.