What Is Pollen Count And How Is It Determined?
NEW YORK (CBSNewYork) — Most have heard something, at least in passing, about pollen levels within the context of discussions of seasonal allergies. Few, however, understand what pollen levels are or how they are determined. A fine powder produced by certain reproducing plants, pollen is released into the air during certain seasons by certain plants. Determination of pollen levels and understanding the distribution of the powder is important because it can cause highly uncomfortable allergic reactions, resulting in itchy eyes, sneezing and runny noses, caused by proteins within the pollen.
While many different plants carry pollen, it is specifically those plants whose pollen is carried by the wind (as opposed to those whose pollen is carried by bees) which put susceptible individuals at risk of developing bothersome allergic reactions. Allergy-aggravating pollen production is most commonly associated with trees, weeds and grasses.Which plants produce bothersome pollen?
Pollen levels are determined according to the amount of pollen in any given area of air (it is typically measured per cubic meter). Hay fever is usually produced by ragweed, which produces an estimated 1 billion pollen grains per plant. Pigweed, tumbleweed, sagebush, lamb's quarters and cockleburs are also common culprits.
Different pollen-producing plants fare best during certain seasons. For example, beech, birch, cedar, cottonwood, elder, elm, hickory, box and ash trees pollinate during late winter and spring. Grasses pollinate during summer and late spring, and include timothy, Johnson, Bermuda, redtop, rye, sweet vernal grasses and Kentucky bluegrass among the most common offenders.How are pollen levels measured?
The air's pollen richness is measured according to the National Allergy Bureau. Meteorologists gauge pollen levels by putting a sticky substance called silicone grease on a rotating rod, called a "rotorod," and attaching the rod to the roof. After 24 hours, the scientists examine the amount of pollen is attached to it, giving them a decent estimate of the air's pollen concentration. They do this by staining the sample, allowing meteorologists to microscopically count the number of grains covering the rod.
Low concentrations of pollen are less than the 50th percentile. In other words, when concentrations are less than the 50th percentile, half of the counts are below the median. Moderate levels of pollen are between the 50th and 75th percentile. High levels are between the 75th to 99th percentile, and very high levels exceed the 99th percentile. The air is most pollinated early in the morning, especially when the air is warm and dry, and the air breezy.Unfortunately, pollen levels are quite difficult to forecast with precision due to the number of variables at play, such as rain, sun and wind activity. Those interested in pollen levels are encouraged to check with certified pollen counting stations. Watching the weather forecast may also be a helpful means for those susceptible to allergies to determine pollen levels and activity.
