Pollen count: The number of pollen grains landing on a given area during a specified time. The count is taken by a spinning rod that moves through the air at certain intervals. The pollen grains that stick to the rod are specially stained and examined through the microscope.
Technically, pollen grains are the small male reproductive bodies of plants; they fertilize the female parts. The microscopic grains are carried from plant to plant by insects, water, wind, and gravity.
This means that if someone is particularly sensitive to pollen, even a small count of 15 to 20 grams per cubic meter could make them miserable. However, pollen counts of 50 or less are usually considered low. When the pollen count reaches 1,000 or more, it is considered very high.
A biomedical engineer Walter Jinotti (1931-2001) devised a system for determining an exact pollen count in 20 minutes (far more quickly than earlier methods). His data provided early warning to hay fever sufferers.