Comparison of outdoor allergenic particles and allergen levels

Introduction: Spore and pollen counts have been used traditionally to determine aeroallergen exposure. Using a liquid based collector and enzyme immunoassays, we have developed methods for measuring airborne allergen concentrations. In this work we test the hypothesis that airborne allergen concentrations are directly related to spore and pollen counts. Methods: Test samplers used included a high-volume cyclonic liquid impinger (SpinCon) and a standard spore trap (Burkard), Samples were collected on a weekly basis from May to October and were analyzed microscopically for spores and pollen grains. The liquid samples were analyzed by enzyme-linked immunoassay for the presence of allergens from Alternaria, Cladosporium, Aspergillus, oak, fescue, ragweed, and plantain. Specific Alternaria allergens Alt al and GP70 also were measured. Results: Pollen counts for the SpinCon and Burkard collectors were similar, though spore counts were lower with the SpinCon. Detectable amounts of three of the seven allergenic species including fescue, ragweed, and Alternaria were present in air samples. Concentrations of pollens were seen in their respective seasons while fungal allergen levels varied throughout the period. Allergen levels generally agreed with particle counts, however peak allergen levels and peak particle counts for individual species did not correlate well. Conclusions: At flow rates of 236 L/min, the SpinCon is comparable to the Burkard for counting airborne pollen and spores. Samples collected by the SpinCon permit quantitative determination of allergen levels in outdoor air. The poor correlation between measured airborne allergen and related particles indicates the potential for significant allergen exposure in the absence of identifiable particles in air.