Road dust - something to sneeze about

November 22, 1999

That "Eat My Dust" bumper sticker on the car in front of you may be closer to the truth than you realized. Research by scientists at the California Institute of Technology shows that road dust kicked up by passing traffic can be a source of airborne allergens.

This finding will appear in the Dec. 1 issue of the peer-reviewed journal Environmental Science & Technology, published by the American Chemical Society, the world's largest scientific society. The article was initially published Oct. 26 on the journal's web site.

"Allergens from at least twenty different source materials were found in paved road dust," according to the study's lead authors, Ann Miguel, Ph.D., and Glen Cass, Ph.D., of the Environmental Engineering Science Department at CalTech in Pasadena. The allergens include pollen, animal dander and molds.

The results of the study "clearly demonstrate that paved road dust and airborne ambient particulate matter contain biologic materials known to be capable of causing or exacerbating allergenic disease in humans," according to the article.

As traffic moves along roads, it stirs up dust from the pavement and resuspends it in the air - thus becoming a source of allergen exposure for people. Residential and rural areas with roadside vegetation tend to be more affected than industrial and downtown areas.

"The study shows that resuspended paved road dust contributes 5-12 percent of the airborne allergenic activity in two residential areas of Los Angeles, but only about 0.5 percent in a downtown industrial location with little vegetation," according to Cass.

Although epidemiological studies have shown a relationship between vehicular traffic and respiratory problems, particularly in children, "the role of vehicular traffic in increasing mold and pollen concentrations in the atmosphere has not been studied previously," says Cass.

"Inhalation of particulate air pollution containing paved road dust could explain, in part, some of the health effects seen with ambient particulate matter exposure," the article concludes.
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