The study is the first of its kind to analyze the effects of "stop and go" bus and truck diesel traffic versus highway traffic on infant respiratory health.
Published in the August issue of the Journal of Allergy and Clinical Immunology, results of the four-year study suggest that the type of traffic and distance from it-- not just traffic volume--are associated with infant wheezing. Previous air pollution studies had not addressed these factors in infants.
"During the first year of life, an infant's lungs and immune system are still developing," said Patrick Ryan, lead author for the study in UC's Department of Environmental Health. "Overexposure to harmful particulates at such a young age may play a role in the development of allergic conditions."
The researchers tracked the respiratory health of 622 infants living near three traffic conditions: highway traffic, "stop and go" traffic, and areas unexposed to major roads or bus routes. A "stop and go" traffic area was defined as being within 100 meters (about 100 yards) of a bus or state route with a posted speed limit of 50 mph or less.
Research showed that infants living within 100 meters of "stop and go" traffic wheezed twice as often as those living within 400 meters (about 400 yards) of interstates, and more than three times as often as unexposed children.
African American infants living near "stop and go" traffic experienced the highest wheezing rate--25 percent.
"Our study illustrates that living within a football field's distance of 'stop and go' traffic puts infants at a higher risk for wheezing," said Ryan. "Traditional wisdom told us that highway traffic was to blame. We now know that's not necessarily the case."