FAQ

The American Academy of Allergy, Asthma and Immunology has a network of pollen counters across the United States. Each counter works under the direction of an AAAAI member and must first pass a certification course provided through the AAAAI. Counters use air sampling equipment to capture air-borne pollens. The number of pollen grains collected are then counted and logged.

Pollen counting stations usually begin reporting in March and April, when pollen levels increase to measurable amounts. The opening date of each station differs slightly from year to year based on local weather conditions. Counting stations in warmer climates generally stay open year round.

There are numerous reasons why pollen counting stations don't count, including technical difficulties with the pollen counting equipment; illness; temporary lack of staff; time away from the office or the station has closed for the season because pollens have diminished to virtually nonexistent levels.

There are a number of reasons that could explain the difference, including the time of day that the sample was taken; a change in temperature, wind conditions, humidity or precipitation; or differences in surrounding geography.

• The time of day that aeroallergens are sampled can account for variances in the amount of pollen measured. Pollen concentrations are usually highest (between 5 a.m. and 10 a.m) after the dew dries after sunrise to late morning. If one station samples at 8 a.m. and the other station samples at 2 p.m., there could be a significant difference in pollen concentration.
• Weather conditions also affect pollen levels. The most variant factors influencing different pollen counts from approximately the same region are wind, humidity, and the proximity of the sampling equipment to pollen producing vegetation.
• Because pollens are small, light and dry, they can be easily spread by wind, which keeps pollen airborne and carries it over long distances. If one station samples when the wind is strong and the other station samples when the wind is calm, there's bound to be a difference in the pollen levels.
• When the air is humid, such as during or after it rains, pollen becomes damp and heavy with moisture, keeping it still and on the ground. If one station samples right before a rain storm, and the other station samples just after it rains, there will probably be a significant difference in the concentration of pollen.
• Proximity of the sampling equipment to pollen producing vegetation. Samples taken from an urban area, where there is little vegetation, will most likely differ from samples taken from a rural area, where there is more vegetation.

The beginning and ending times of tree, grass and weed pollen seasons are very similar from year to year in the same location. Intensity differs every year based on the previous year's weather, current weather and other environmental factors.

The NAB is always working to add more counting stations. The NAB will continue its efforts to enlist additional volunteers to its network of certified counting stations so that most areas of the country are represented.

It's difficult to provide accurate pollen and spore levels for areas not near a pollen counting station. If the climate and geography are similar, chances are the figures reported by the station are a good indicator of conditions nearby.