The in situ interaction between pollen and airborne particulate matter (APM) as well as the effect of extracts of APM on grass pollen (Dactylis glomerata) was studied. The samples were processed for structural analysis using scanning and transmission electron microscopy as well as for determination of protein content and release using immunoblot techniques. The results indicate a direct in situ interaction between pollen surfaces and APM. This effect is prominent in industrialized regions with high emission of organic pollutants. It is also found to occur near roads with heavy traffic. There is morphological evidence for preactivation of pollen by organic extracts of APM. Aqueous extracts, however, directly induce the release of allergens with altered antigenicity. It is concluded that the generation and release of allergenic aerosols in a humidified air is initiated and mediated by substances adsorbed to APM.

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Air pollution is supposed to enhance the risk of allergy. Investigations of the influence of environmental pollutants on allergic inflammatory reactions are therefore of increasing importance. Pollen grains which are the major source or outdoor aeroallergens are said to probably express an altered allergenicity when emitted into a polluted air. We investigated the behavior of pollen grains which had been collected from four differently polluted regions in North Rhine-Westphalia, FRG. Samples were taken with Burkhard traps and/or high volume samplers. In addition, native grass pollen have been exposed to extracts of airborne particulate matter in vitro in a dose-and time-dependent manner. The samples were further processed for scanning and transmission electron microscopy as well as for determination of protein content and release using IEF and SDS-PAGE immunoblot techniques.The results obtained show that (1) there is an overall higher concentration of pollen grains in polluted urban areas than in rural regions, independent of weather conditions; (2) emission peaks of S02, N0 2 /NO x or atmospheric fine dust, but not of 0 3 , usually precede peaks of high pollen concentrations; (3) pollen grains collected from highly polluted regions are significantly more contaminated with agglomerations of airborne particulates, and the intensity of pollen/particle binding depends on amount and composition of organic compounds adsorbed to the particle; and (4) incubation of purified grass pollen with extracts of atmospheric fine dust results in dose-and time-dependent alterations of structural pollen integrity and of protein release, probably leading to altered allergenicity.The results indicate that there is a complex interaction between pollen grains and air pollutants, not only with respect to daily emission peaks but also through direct binding of particulate matter to the pollen surface. Therefore, dust-laden pollen grains from heavily polluted areas can induce cytotoxic and mutagenic reactions in addition to sensitization. This fact has to be taken into account when assessing influences of air pollution on allergic inflammatory response.

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