June 19 (HealthDay News) -- A child's risk of developing allergies increases by up to 50 percent from pollution caused by traffic, a rate that increases the closer the child grows up next to major roads, a new study says.

The findings, published in the June issue of the American Journal of Respiratory and Critical Care Medicine, revealed significant links between the distance to the nearest road and asthmatic bronchitis, hay fever, eczema and allergic sensitizations.

"[Children] living very close to a major road are likely to be exposed not only to a higher amount of traffic-derived particles and gases but also to more freshly emitted aerosols which may be more toxic," wrote lead author Joachim Heinrich, of the German Research Center for Environment and Health at the Institute of Epidemiology in Munich.

The researchers examined the level of exposure to traffic pollutants for almost 6,000 children, ages 4 and 6, based in part on how far their homes were from major roads at different times during their lives. The children were tested for asthma, wheezing, sneezing, eczema and food allergies, while their parents answered questionnaires about their child's respiratory diagnoses and symptoms. Testing for particulate matter (commonly called soot) and nitrogen dioxide was also conducted near 40 high-traffic areas during each season between March 1999 and July 2000.

Pollution and allergies have been linked in previous studies, but the association was often attributed to socioeconomic factors, not the distance from major roads.

"We consistently found strong associations between the distance to the nearest main road and the allergic disease outcomes," Heinrich wrote. "Children living closer than 50 meters to a busy street had the highest probability of getting allergic symptoms, compared to children living further away."

SOURCE: American Thoracic Society, news release, June 13, 2008