Predominant tree aeroallergens of the Washington, DC area: a six year survey (1989-1994).

OBJECTIVE: A 6-year (1989 to 1994) aerobiologic survey of the Washington DC area was performed to identify predominant area tree pollens, atmospheric concentrations, and peak flowering periods.
METHODS: Aeroallergen sampling was conducted using a volumetric rotating-arm impaction Rotorod sampler (Sampling Technologies, Inc, Los Altos Hills, California).
RESULTS: The Washington DC pollen calendar may begin as early as January when pollen of the Cupresseacea, Aceracea, Pinaceae, and Betulaceae are observed in small amounts. February through June encompasses the major part of our tree season with considerable overlapping of pollination periods for various trees. The Ulmaceae have two distinct pollinating times with later flowering species of elm pollinating August through October coinciding with ragweed season. April is usually the month with the highest weekly average concentrations. Each year oaks contribute more than 50% of the total tree pollen count followed by pollen of the Pinacea, Cupresseacea, Moracea, and Betuleacea. Times for onset of pollination as well as peak atmospheric concentrations varied from year to year. High production years for some tree aeroallergens are low years for others.
CONCLUSION: The Washington DC area is exposed to significant atmospheric concentrations of tree pollen from February through June. Establishing what area tree aeroallergens predominate with respect to their atmospheric concentrations and peak pollinating times is essential for the effective diagnosis and treatment of the tree-allergic patient.