How Are Pollen Counts Collected?

Pollination is the transference of pollen from plant to plant, ensuring fertilization and reproduction. The pollen grain is the vehicle used in this process by flowers, grasses and trees. Pollen grains are microscopic, about 15 to 100 microns in size. Just a pinch of pollen powder contains thousands of pollen grains. Pollen varies in size, type and allergens. The National Allergy Bureau collects pollen at stations throughout the United States, Canada and Argentina using a Burkard volumetric spore trap, a Kramer-Collins sampler or a Rotorod sampler. Once pollen is collected and counted, this data is provided to the public in the form of allergy reports and alerts used by millions to control seasonal allergies.

Significance

• The National Allergy Bureau is a division of the American Academy of Allergy, Asthma and Immunology's airborne allergen network that is responsible for reporting current pollen levels to the public. AAAAI staff members volunteer their time and expertise to collect airborne pollen samples used for research to aid in the diagnosis, treatment and management of allergic diseases. NAB counting stations use air sampling equipment to collect and examine airborne pollen microscopically.

Time Frame

• Air is sucked into the trap of the sampling equipment at a rate of 10 liters per minute, and pollen and other particles are captured on adhesive tape or microscopic slide. The pollen count measures the number of pollen grains of a particular type per cubic meter of air sampled as an average over 24 hours. NAB pollen sites have continuous sampling that occurs daily and must be collected a minimum of three days per week.

Geography

• The National Allergy Bureau has pollen counting stations in three countries. There are approximately 78 stations throughout the United States, two in Canada and two in Argentina. View current and past pollen levels for your area online (link in Resources).

Benefits

• Pollen counts are interpreted into scales that are relayed as pollen forecasts. The pollen forecast is given as absent or none, low, moderate, high and very high. Low is fewer than 30 pollen grains per cubic meter of air. Moderate is 30 to 49 pollen grains per cubic meter of air. High is 50 to 149 pollen grains per cubic meter of air. Very high is 150 or more pollen grains per cubic meter of air. Most allergy sufferers will begin to experience symptoms when the pollen count reaches the moderate level.

Considerations

• Members of the NAB must be certified through the AAAAI certification program. Certification must be maintained and is administered through the AAAAI Aerobiology Committee. A pollen counter must be able to accurately identify and count pollen on an actual pollen slide. Collection stations must use a Burkard volumetric spore trap, a Kramer-Collins sampler or a Rotorod sampler that is situated on an unobstructed rooftop at least one story above the ground with no local pollen sources.

Warning

• Weather affects how much pollen is carried through the air but has little effect on when pollination occurs. Typically, weeds pollinate in late summer and fall, grasses pollinate in late spring and summer and trees pollinate in late winter and spring. Considerable amounts of pollen are released early in the morning just after dawn. Pollen travels best on warm, dry, windy days. Pollen counts are lowest when the weather is wet and cold.