Pollen Information

A stained rod shows various pollen types and mold spores.
This representative Fall sample was made in early August 2004.
Note the numerous dust particles and other debris in this
air sample. The air sampled in this one view, represents
the amount of air an adult, at rest, respires in about 15 minutes.

How Are Pollen Counts Made? A Rotorod Sampler is used to make pollen counts. Two small (1.52mm X 1.52mm X 32mm) polystyrene rods rapidly spin throughout the sampling period (normally 24 hrs). One surface of each rod is coated with silicon grease to capture and retain impacted particles. Pollen and mold spores represent a small fraction of the “stuff” in air, but are biologically important as they can cause severe allergic diseases. The Rotorod Sampler gives accurate results with pollen, but smaller mold spores are not accurately captured. Once removed from the sampler, the rods are stained and viewed under a microscope where each pollen grain is identified and counted. The number of grains on the collector rod is related to the volume of air sampled, then this is reported as pollen grains per cubic meter of air (grains/m3). The count reflects pollen collected over the previous 24 hr sampling period. Pollen counts are useful for allergy sufferers and their physicians to correlate symptoms and causing agents.		pollen sampler atop Olin Science Building	pollen sampler
		The Rotorod sampler running during a sampling period. The two rotating polystyrene rods are blurred, but visible.
Stained Pollen Grains		A stained rod shows various pollen types and mold spores. This representative Fall sample was made in early August 2004. Note the numerous dust particles and other debris in this air sample. The air sampled in this one view, represents the amount of air an adult, at rest, respires in about 15 minutes.
chenopod	grass
hemp	ragweed
Seasonality of Pollen Different plants shed their pollen at different times of the year. The three graphs to the right were made by Greg Timblin using the 2002 pollen data and clearly illustrate this trend. In early spring, tree pollen dominates. In the Midwest, these species include elm, oak, maple, poplar, juniper, willow, walnut, sycamore, hackberry, ash, cottonwood, birch, mulberry, and pine. Grasses (all grass pollen is similar and species cannot be distinguished) predominate in late spring and early summer. Weeds are the predominant pollen in late summer into fall. The Midwest weed species include nettle, chenopod (members of the pigweed and amaranth families), hemp, sage, and ragweed. Ragweed is a prolific fall pollen producer and is most responsible for allergy symptoms.
		Allergic Diseases Airborne allergens (pollen and mold spores) stimulate Immunoglobulin E (IgE) antibody production in susceptible persons when the allergens impact mucous membranes and cause respiratory tissue to become sensitized. Repeated exposure to a specific allergen can lead to clinical allergic diseases which include allergic rhinitis (“hay fever”), asthma, atopic dermatitis, conjunctivitis, earaches, and sinusitis. Some 50 million Americans suffer from allergic disease.