Determination of ranges for reporting pollen aeroallergen levels in the Washington, DC, metropolitan area.

BACKGROUND: Local aeroallergen monitoring provides useful information for the atopic patient and medical community. Currently, National Allergy Bureau (NAB) ranges are used for reporting pollen count levels in the Washington, DC, area. OBJECTIVE: To determine standard range criteria (low, moderate, high, and very high) for the reporting of specific tree, grass, and weed aeroallergens representative of the Washington, DC, metropolitan region. METHODS: Atmospheric sampling for pollen aeroallergens was performed using a volumetric rotating-arm impaction sampler (model 40 Rotorod, SDI Company, Plymouth Meeting, PA). The cumulative pollen count, over a 12-year period (1998-2009), was determined for specific pollen aeroallergens. Local ranges were developed using methodology previously employed to determine NAB ranges. A comparison was made between NAB and Washington, DC, area ranges. RESULTS: The local median count, and low and moderate range criteria, are markedly lower than NAB range counts for tree, grass, and weed pollen. The NAB 99th percentile (high) count is significantly higher for grass and weed pollen but lower for tree pollen. Using new local range criteria, an increase was seen in the number of high days recorded for weed pollen (1,300%), grass pollen (258.6%), and tree pollen (11.8%). Previously, using NAB range criteria, no very high days were reported for grass and weed pollen over the 12-year period. CONCLUSION: Washington, DC, ranges establish more relevant reporting standards for our local patient population and will allow for comparison with reporting levels developed for sampling locations nationwide as well as with other regional sites.

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.