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Frequently Asked Questions About Pollen Forecasting And Sampling for Allergy Alerts

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What does "mixed trace" mean?

Trace amounts of pollen can be found in air samples in most locations, despite the likelihood that no allergenic plants are actually actively producing pollen locally. This typically occurs during the winter months, after the fall season has ended, and before the spring tree season has started. Pollen may be resuspended into the air from the ground, and other surfaces such as tree branches, blades of grass, buildings, or roadways. Contents of the mix of pollen can be any pollen type that was in the air in higher numbers in the season, pollen from previous years or even pollen which has been transported long distances through the upper atmosphere.

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