Pollen aeroallergens in the Washington, DC, metropolitan area: a 10-year volumetric survey (1998-2007)

Background Local aeroallergen surveys identify and establish patterns of prevalence for tree, grass, and weed species that enable the clinician to more effectively select allergens for skin testing and therapy. Objectives To determine peak pollination periods, atmospheric concentrations, and year-to-year variation for identified tree, weed, and grass aeroallergens and examine the influence of selected meteorological parameters. Methods Atmospheric sampling for pollen aeroallergens was performed using a volumetric rotating-arm impaction sampler. The Spearman correlation coefficient was used to determine the relationship between daily counts and selected meteorological parameters. Results Previous findings for area trees, conducted at a different location, are corroborated. Predominant pollen types include Quercus , Cupressaceae, Pinaceae, Morus , Betulaceae, Acer , Platanus , Fraxinus , Poaceae, and Ambrosia . Early flowering weeds ( Rumex and Typha ) and Poaceae overlap with peak tree season in April. Biphasic seasons are noted for Poaceae and Ulmus . Tree pollen accounts for 91.2%, weeds 3.8%, and grasses 3.2% of total annual pollen yield. Variation in overall pollen production is evident from year to year. High production years for some species are low for others. Cyclic pollinating patterns for Alnus , Betulaceae, and Fagus were observed. Grass and weed pollen correlated positively with maximum temperature and dew point; however, the results for individual tree species were variable. Conclusion The Washington, DC, metropolitan area is host to a variety of tree, weed, and grass species that produce copious amounts of pollen. Further investigation into year-to-year variation with respect to inherent cycling and meteorological influences is warranted.