Pollution from Traffic Linked to Allergies in Children

Once the little ones come along, you may need to think long and hard about your housing locale, particularly if allergies are in your genetic makeup. A new study is showing that traffic-related pollution could be responsible for increasing the risk of allergy and atopic diseases (chronic skin diseases) by more than 50 percent in children.

The lead author of the research that was conducted, Joachim Heinrich, Ph.D., of the German research Center for Environment and Health at the Institute of Epidemiology said, "[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 a more freshly emitted aerosols which may be more toxic. [The study's] findings provide strong evidence for the adverse effects of traffic-related air pollutants on atopic diseases as well as on allergic sensitization." The results of this study were published in the second issue for June 2008 of the American Thoracic Society's American Journal of Respiratory and Critical Medicine.

This study examined approximately 2,900 children at the age of four and more than 3,000 at the age of six to determine their rates of physician-diagnosed asthma and/or allergies that are related to long-term exposure to pollution caused by traffic. Both age groups of children came from prospective cohort studies and were enrolled at birth in the metropolitan Munich area. The children's exposure to the traffic pollutants was calculated as a function of the distance of their houses from the major roads at birth and at ages two, three, and six. The parents were given questionnaires about their child's respiratory diagnoses and symptoms, and their children were then assessed for asthma, sneezing, wheezing, and eczema. The children were also tested at the age of six for food allergies. The air was tested for particulate matter (e.g. smog, soot, etc) and nitrogen dioxide (NO2) at each of the forty identified points near the high-traffic areas once during each season been the months of March 1999 and July 2000.

After creating a control for individual characteristics such as pet ownership, pet allergies, and the number of siblings, the researchers then found significant positive associations between the distance of the nearest road and the diseases hay fever, asthmatic bronchitis, eczema, and allergic sensitizations. They also found that the people living closest to the major roads had nearly 50 percent greater risk of allergic sensitization in a distant-dependent relationship.

Previous studies that have been conducted found that pollutants and allergic sensitization are linked, but only using distance from major roads as a proxy for pollutant exposure has been confused by the socioeconomic factors that are often too closely linked to such locales. However, in the city of Munich, as well as other European cities that are older, the buildings and roads are structured so that the economic advantages are not necessary correlated with living further from the main thoroughfares. In this particular study, it was possible to determine that the factors of the environment were not a confounding variable in the analysis, but there was a difference that was clear in the children's allergic development with relation to their distance from a road.

Dr. Heinrich concluded that they consistently found strong associations between the distance of the residence to the nearest main road and the allergy outcomes. The children that are living closer than 50 meters to a street that is busy have the highest probability of getting symptoms of allergies, compared to the children that are living further away.