EVERYONE is familiar with the gray-brown haze that often blankets Los Angeles, and the fact that the city consistently ranks as one of the most polluted in America. But what many may forget is that the dismal reports of L.A.'s air pollution only capture the average amounts of toxins in the air, and that some places within the urban sprawl are far dirtier than others. Official numbers do not take into account the fact that pollutants are at much higher levels within a few hundred feet of the freeways that crisscross the city -- and for the adults and kids who live, work or go to school there, the effects add up.

For kids, whose lungs are still growing, these effects can be especially damaging. Mounting scientific evidence reveals that exposure to air pollution interferes with the development of children's lungs, reducing their capacity to breathe the air they need. Although the long-term consequences aren't known, it is known that growth in lung function is nearly complete by the end of adolescence. Because lung capacity diminishes as people grow older, children exposed to air pollution may enter adulthood with the deck stacked against them.

Proximity to freeways appears to matter. Recently, studies have shown that the lung capacity of children who live within 500 meters (1,650 feet) of a freeway is significantly reduced compared with those who live more than 1,500 meters (4,950 feet) away. For kids who already live in an area with high levels of pollution, living near a freeway is "adding insult to injury," says Dr. John Balmes, professor of medicine at UC San Francisco and professor of public health at UC Berkeley.

To help protect children from the heightened effects of this extra dose of air pollution, California passed a law in 2003 prohibiting schools from being built within 500 feet of major roadways. Districts are allowed to build within this buffer zone only if space limitations leave no option or the district can find ways to mitigate the increased air pollution. Yet a September article in The Times reported that the L.A. Unified School District was building five schools within 500 feet of a freeway and had plans for two more.

The district is now reconsidering its plans and working on new policies aimed at limiting students' exposure to pollution at schools built near freeways, but such laws can do only so much. Even if they aren't going to school near a freeway, children may still be walking down the street or playing in their backyard near one. Thousands will still be exposed to dangerous levels of air pollution.

Stunted lung development
In 2004, USC researchers reported that children living in areas with higher pollution, such as San Dimas and Riverside, had stunted lung development compared with children living in areas with lower pollution, such as Atascadero and Alpine. The findings came from the Children's Health Study, which in 1993 recruited about 1,700 fourth-graders from 12 California communities and studied their lung function over eight years.

The effects on children's lungs were both statistically and clinically significant: The proportion of children with low lung function was 4.9 times greater in the community with the highest level of fine-particle pollution (Mira Loma) compared with the community (Lompoc) with the lowest levels (7.9% versus 1.6%). Results were similar when the researchers looked at other categories of pollution, such as nitrogen dioxide and elemental carbon.

In February, the USC group published another report, in the journal the Lancet, showing that living near a freeway could further affect a child's lung development. As in the 2004 study, researchers followed the group of fourth-graders recruited in 1993, as well as a later group recruited in 1996. In this study, however, the children in each city were further subdivided into those who lived close to (within 500 meters) or far (more than 1,500 meters) from a freeway or other major road.

As in the other study, researchers would visit the children every year at their schools and measure with a device called a spirometer how much and how fast each child could exhale. They found that children who lived close to a freeway in a low-pollution community had about a 4% decrease in their lung function compared with children living in the same community but far from a freeway. This decrease was similar to that seen in children who lived in highly polluted communities but far from a major road.

The results were worst for the children who lived near a freeway within a polluted city. They had the greatest reduction in lung function over the course of the eight years each child was tracked -- about 9%, compared with the kids in clean cities who lived at least 1,500 meters from a major road.

Lung development is nearly complete by age 18 -- meaning that someone with a deficit in lung function at the end of adolescence will probably continue to have less than healthy lung function for the rest of his or her life. And that could lay the adult open to a variety of maladies. "Poor lung function in later adult life is known to be a major risk factor for respiratory and cardiovascular diseases, as well as for mortality," said W. James Gauderman, an epidemiologist at the USC Keck School of Medicine and leader of both studies.

(By Erin Cline Davis, Los Angeles Times, 10/12/2007)