Traffic pollution from freeways may stunt development of the lungs in children aged 10 to 18, according to a study by researchers from the University of Southern California.

Dr. W. James Gauderman and colleagues from the USC and other institutions found that development of the lungs in children who lived within 500 meters or one third of a mile of a freeway were significantly retarded by traffic pollution compared to those who lived three times farther away from a freeway.

Previous studies have shown that children living near highways are more likely to develop respiratory problems such as asthma. The current study, published on January 26, 2007 in The Lancet Early Online Publication , was meant to establish an association between residential exposure to freeways and other major roads and 8-year lung function growth.

Such an association between long exposure to car and truck exhaust and the growth of the lungs and their capacity has been unknown until the current study although it is well known the car exhausts are toxic.

In the study, Dr. Gauderman and colleagues followed 3,677 children starting at age 10 from 12 southern California communities including the cities of Alpine, Anaheim, Glendora, Lake Arrowhead, Lake Elsinore, Long Beach, Mira Loma, Riverside, San Bernardino, San Dimas, Santa Barbara, Santa Maria and Upland. The residential areas represented a wide range in regional air quality. They measured lung function in each child every year for eight years.

The researchers considered the range of age because lung development is fastest and more susceptible to environmental risks during the period between age 10 and 18. At age 18, the lungs get mature and stop development.

Children who lived within 500 meters of a freeway or motorway had substantial deficits in eight-year growth of forced expiratory volume in 1 s (FEV1), 81 ML less than that in children who lived at least 1,500 meters away from a freeway, the researchers found.

Likewise, children who lived closer to freeways had a smaller maximum midexpiratory flow rate (MMEF), 127ML/s less than that for children who lived farther away from freeways.

Study data showed that both local exposures to freeways and regional air pollution had detrimental, yet independent effects on lung-function growth. Previous studies have demonstrated a link between regional air quality and lung function growth.

In addition, at age 18, children who lived within 500 m of a freeway had pronounced deficits in attained lung function with mean percent-predicted 97ยท0 percent for FEV1 relative to that for those who lived 1,500 m or farther away from a freeway. The MMEF was reduced to 93.4 percent.

"Otherwise-healthy children who were non-asthmatic and non-smokers also experienced a significant decrease in lung function from traffic pollution," said Dr. Gauderman. "This suggests that all children, not just susceptible subgroups, are potentially affected by traffic exposure."

Researchers writes in their report that "local exposure to traffic on a freeway has adverse effects on children's lung development, which are independent of regional air quality, and which could result in important deficits in attained lung function in later life."

It remains unknown how these deficits in the lung functions would impact the lung functions after age of 18 years. It is also unknown how traffic population would affect the lung development in children younger than 10 years.

But "someone suffering a pollution-related deficit in lung function as a child will probably have less than healthy lungs all of his or her life," said Dr. Gauderman. "And poor lung function in later adult life is known to be a major risk factor for respiratory and cardiovascular diseases."

"This study shows there are health effects from childhood exposure to traffic exhaust that can last a lifetime," said David A. Schwartz, M.D., Director of the National Institute of Environmental Health Sciences (NIEHS).

The current study did not seek to explain why lung function was comprised in the children who lived in the vicinity of a freeway although the researchers claimed that traffic pollution was responsible.

In an early study, Dr. Jonathan Grigg and colleagues from University of Leicester, Leicester, United Kingdom found that tiny carbon particles generated from incomplete fuel combustion in traffic fumes could get into children's airways in the lungs, diminishing their lung function.

They found that every one micrometer-squired increase of carbon content in children lungs would result in 13 percent reduction in forced vital capacity (FVC), 17 percent reduction in forced expiratory volume in one second (FEV1), and 35 percent reduction in the forced expiratory flow.

The study published in the July 6 2006 issue of The New England Journal of Medicine involved 114 healthy children from Leicester, a city in England. The researchers examined valid sputum (mucous) samples from 64 children and assessed their lung function.

New reported cited Grigg as stressing that the damage to children's lungs is cumulative. According to the authors, the adverse effect of particle pollution on lung function growth was small, but cumulative. Long term exposure can exert a large negative effect.

The state of California in October, 2004 issued a fact sheet titled Air Pollution from Nearby Traffic and Children's Health to remind parents and schools of the danger of traffic pollution to children's health. Although the state did not realize at the time that living near freeways may harm development of the lungs in children, tips offered on how to prevent traffic pollution should still valid.

To minimize children's exposure to air or traffic pollution, California advises that

Drivers never leave your car idling in the garage.

Children should avoid standing near idling motor vehicles when possible.

Choose streets with less traffic if possible if you have to walk.

Close windows and doors during peak traffic hours and place the air conditioner setting on "re-circulate" if you live near freeways or roads with heavy traffic.

Try not to follow closely behind cars, trucks and buses that have visible smoke rising from the exhaust pipe when you drive.

Carpool and use alternative transportation when possible.

Buy a car with low exhaust emissions when you buy a new car.

The current study was funded by the California Air Resources Board, the National Institute of Environmental Health Sciences, the U.S. Environmental Protection Agency, the National Heart, Lung and Blood Institute and the Hastings Foundation.

Primary source:

W. James Gauderman, Hita Vora, Rob McConnell, Kiros Berhane, Frank Gilliland, Duncan Thomas, Fred Lurmann, Edward Avol, Nino Kunzli, Michael Jerrett and John Peters, "Effect of exposure to traffic on lung development from 10 to 18 years of age: a cohort study," The Lancet, Volume 368, February 2007.