Allergens in paved road dust and airborne particles

Paved road dust present on the surface of streets in Southern California consists of a complex mixture of soil dust, deposited motor vehicle exhaust particles, tire dust, brake lining wear dust, plant fragments, and other biological materials. The research presented here shows that allergens from at least 20 different source materials are found in the paved road dust. These include pollens and pollen fragments, animal dander, and molds. When paved road dust is resuspended into the atmosphere by passing vehicle traffic, allergen concentrations in the air are increased above the levels that would prevail without the vehicle traffic. Using immunological assays that measure the proteins extracted from environmental samples that bind to IgE antibodies present in the blood serum of allergenic patients, it is possible to measure the allergen concentrations present in paved road dust and in airborne particle samples. Total protein contributions to monthly average airborne TSP and PM10 concentrations are found to be in the range from 1 to 5.8 mu g m(-3), potentially accounting for a significant fraction of the airborne particulate organic material that has not been identified to date by GC/MS techniques. Results show that up to 5-12% of the allergenicity of atmospheric total suspended particulate matter samples at Long Beach and Rubidoux, CA, is attributable to paved road dust emissions. In an industrial area of urban central Los Angeles where there is less proximity to vegetation and domestic activities, the paved road dust contribution to airborne allergen concentrations is lower, accounting for approximately 0.5% of the total allergenic activity of the atmospheric particle samples. In conclusion, paved road dust when entrained into the atmosphere by passing traffic is a source of allergen exposure for the general population and could be more important in areas with more abundant vegetation or with closer proximity of populations to major highways than is the case for the Southern California air monitoring sites studied here.