Led by researchers at the University of Southern California, the studies suggest that air pollution -- particularly from vehicles -- may be worse for people's health than previously thought.
Children are especially susceptible to air pollution because their bodies are still developing and they breathe more rapidly than adults.
By measuring tailpipe pollution at the children's homes and analyzing traffic on nearby roadways, researchers in one study found the closer children lived to a freeway, the higher their chance of developing asthma.
The study, led by James Gauderman of USC's Keck School of Medicine, demonstrates that breathing vehicle exhaust can play a role in developing asthma, and it joins a growing library of research showing that air pollution can cause asthma.
Gauderman said he hopes people will consider the potential health problems from building schools and housing tracts next to freeways.
"Even if you lived in a generally low-polluted area, but lived near a freeway, the risks were increased there as well," he said. "We need to think a little more about that before we place people so close to a source of fresh vehicle exhaust."
Los Angeles City Councilwoman Jan Perry, who also sits on the South Coast Air Quality Management District, said the study is a wake-up call to planners.
"Family housing should not be encouraged next to freeways. You can use that for light-industrial uses. It doesn't necessarily have to be for housing."
Bonnie Holmes-Gen, vice president of government relations for the American Lung Association of California, said the findings do not definitively prove that air pollution can cause asthma, but they're surprising.
"We expect more research will come out showing the linkage between asthma and air pollution," Holmes-Gen said.
In a separate study led by USC Keck School of Medicine professor Michael Jerrett, researchers studied two decades of data on Los Angeles area residents and found that, as the levels of fine particulate matter increased, so did the risk of death.
Jerrett's research also saw a link between particulate-matter levels and death from heart attack and lung cancer.
Researchers plan to conduct a similar study in New York City to see if they find a similar trend.
Fine particulate matter is created from vehicles' exhaust, including diesel exhaust, and from fires and industrial pollution. It's made up a microscopic bits of acids, chemicals, metals, dusts and allergens that can reach deep into the lungs and enter the bloodstream. l=8s=8 Kerry Cavanaugh, (818) 713-3746 firstname.lastname@example.org