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Pollen and Mold Center
Frequently Asked Questions (FAQ's)


What is pollen?
Who can count pollen and mold?
How are pollen and mold collected?
How does the Burkard sampling device work?
How are pollen and mold counted?
Why is there not always a count available?
Why do pollen and mold counts vary so much from day to day?
Are pollen seasons the same every year?
How do the pollen counts apply to my area if I live x miles from a counting station?
What is an allergy?
Will moving help my allergies?
How can I lessen my exposure to pollen and mold?


What is pollen?

Pollen is the male "seed" of a plant that appears as a dust. It can be transferred by insects or the wind for plant reproduction.

Who can count pollen and mold?

Only certified counters can read pollen and mold. Each counter must pass a year long certification course provided through the Harvard School of Public Health and must be accredited by the American Academy of Allergy, Asthma and Immunology (AAAAI). The Environmental Health Laboratories has certified counters on staff. Meteorologists, allergy specialists, physicians, and individuals have relied on the Saint Louis County Department of Health for this data since 1960. We report our data to news and weather casters and to health organizations such as the American Lung Association.

How are pollen and mold collected?

Counters use air sampling equipment to capture airborne pollen and mold. Recently, the Environmental Health Laboratories switched from using a rotorod impaction device to using a Burkard slit-type volumetric spore trap. The rotorod sampled only at specific time intervals while the Burkard is able to continuously sample over a 24 hour period.

How does the Burkard sampling device work?

The device is mounted on the roof of a centrally located County building away from any obstructions. It uses suction to pull air through a slit-type opening. Inside the slit is a greased, flat surface (a collection tape) that advances in increments over time. This greased surface collects any particles that are sucked in with the air.

How are pollen and mold counted?

The collection tape is removed from the sampling device and brought to the laboratory. Here it is stained and prepared for analysis. The sample can then be magnified 400 times to count the pollen grains. For some mold spores, the sample must be magnified 1000 times to be seen and counted. Using the exposure time, the volume of air sampled, and the number of pollen grains or mold spores counted, calculations can be made to determine the number of particles per cubic meter of air sampled. This is the number reported by the laboratory.

Why is there not always a count available?

There are many reasons why no count is available at various times. Some possible reasons include technical difficulty with the sampling device, inclement weather, the sample being unreadable, illness or absence of the laboratory's certified counter(s), or the laboratory is closed for the holidays.

Why do pollen and mold counts vary so much from day to day?

Changes in temperature, wind conditions, humidity, or precipitation can affect the counts greatly.

  • Temperature: A sudden temperature drop lowers the pollen count significantly. Certain pollens are seasonal. Trees are dominant in the spring, grasses occur in late spring and early summer, and weeds grow from late summer until the first hard frost.
  • Wind: Pollens are small, light, and dry so they are easily spread by wind. The distance the pollen travel can depend on whether the wind is strong or calm that day.
  • Humidity: When the air is humid, pollen becomes damp and heavy with moisture keeping it still and on the ground.
  • Precipitation: Rains tend to "cleanse" the air of pollen. When the pollen is wet, it becomes heavy with moisture keeping it on the ground.
Are pollen seasons the same every year?

Generally tree, grass, and weed seasons are similar every year in the same location. However, the intensity can differ depending on the current weather, the previous year's weather, and other environmental factors. Typically, trees pollinate earliest from February to May, grasses follow in May to mid-July, and weeds peak from late summer to early fall.

How do the pollen counts apply to my area if I live x miles from a counting station?

If the climate and geography are similar, the counts should be a good indicator for your area. Keep in mind that samples taken from an urban area, where there is little vegetation, can differ from samples taken from a rural area, where there is more pollen producing vegetation.

What is an allergy?

An allergy is an abnormal reaction to an ordinarily harmless substance called an allergen. Common allergens include pollens, molds, dust mites, animal dander, foods, medications, cockroach droppings, and insect stings/bites. You may be allergic to one or more allergens. When an allergen is absorbed into the body of an allergic person, their body fights to rid itself of the allergen. The immune system initiates a defense which causes symptoms such as runny nose, watery eyes, congestion, itching, and sneezing.

Will moving help my allergies?

When a person with allergies moves to another location, they will likely be exposed to a new set of allergy triggers. In some cases, the new symptoms may be more tolerable or less intense. Keep in mind that it can take months or years to become allergic to a new allergen. Seasonal allergy sufferers may be able to find temporary relief by vacationing during the peak of pollen season to a different climate or a more pollen-free area such as near large bodies of water.

How can I lessen my exposure to pollen and mold?

During the peak of the pollen or mold season that affects you, try following these guidelines:

  • Keep windows closed at night.D
  • Minimize early morning outdoor activity when most pollen is released (between 5-10 AM).
  • Keep your car windows closed when traveling.
  • Stay indoors when the pollen count is high and on windy days when dust and pollen are easily scattered.
  • Vacation during the peak of pollen season to an area where there is less pollen, like the beach.
  • Take any medications your allergist recommends as prescribed.
  • Do not rake leaves, mow lawns, or be around freshly cut grass. This stirs up pollen and mold.
  • Do not hang laundry outside to dry. Pollen and mold will collect in them.
  • Keep indoor plants to a minimum and never overwater if allergic to mold. Wet soil encourages mold growth.