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How Do You Measure Pollen Count?

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Come spring or fall, there's one figure in particular that's on the minds of many people: pollen count. In fact, according to the Asthma and Allergy Foundation of America, this number affects some 35 million people in this country who are allergic to pollen.

This allergy causes hay fever, which comes with unpleasant symptoms such as sneezing, watery eyes, and itching of the nose, mouth, eyes or throat - so it makes sense that pollen count would be a core concern during the transitional seasons. Luckily, meteorologists can measure and predict it.

Here's everything you need to know about this useful figure.

What is Pollen Count?
Simply put, trees, weeds and grasses release pollen, an extremely fine powder, and it is carried to other plants of the same kind for fertilization. The pollen count tells us the number of grains floating around in a set amount of air - typically one cubic meter - at a given time. The higher the pollen count, the more likely allergy sufferers will experience an attack. That's why it's helpful to check pollen counts on a daily basis, especially during allergy seasons. Also keep in mind that pollen doesn't always stay outdoors, it can creep into your home as well. As such, using an air purifier during allergy season is a key step in reducing symptoms. 

How is it Measured?
One ragweed plant can produce up to 1 billion pollen grains, according to the AAFA, and wind can carry these particles hundreds of miles away - so measuring pollen isn't easy. Allergists use a tool called a Vurkard volumetric spore trap, which vacuums up air through a slit and captures floating grains. Meteorologists also measure the pollen count by attaching a rotating rod with a sticky substance to the roof of a building. After 24 hours, they analyze the amount of pollen that has adhered to the rod.

When is it Usually High?
Pollen levels can vary depending on the location, weather and time of day.

Areas with warm climates that experience little to no rain will have higher pollen counts. Everwell explained that levels are typically highest in the morning, just after dawn. Additionally, the AAFA noted that pollen floats more easily on dry, breezy days.

On the other hand, counts tend to be lower later in the day. Since rain and cool weather can hinder pollen travel, levels will likely be lower during cold, wet periods. In fact, Slate magazine reported that even a light drizzle can eliminate a substantial amount of pollen from the air, or prevent plants from releasing it. This is because when flowers become damp, they are unable to open up. However, it's worth noting that a sudden thunderstorm can also boost the pollen count due to the rush of wind that comes before it.


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