Jun 30, 2020
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After rain, a large amount of allergenic pollen remains in the air

Experts do not recommend allergy sufferers to walk in the rain and immediately after it in the pollen season.

The opinion that rain leaches pollen from plants from the air and helps alleviate the symptoms of pollinosis sufferers is a mistake. New study published in Letters about the environment and technology, showed that heavy rain can increase the amount of particles dangerous to allergy sufferers in the air.

Scientists measured the amount of pollen in the air during and after spring rain. It turned out that its particles can remain in the air up to 11 hours after rain. According to scientists, this is an underestimated danger for allergy sufferers and asthmatics.

The authors of the study found two independent effects of rain on pollen. It turned out that rain, as expected, contributes to the deposition of whole pollen. On the other hand, the number of pollen fragments in the air increased during rain.

“Pollen-sensitive people should avoid walking in the pollen season in the rain, especially during thunderstorms, and for the next few hours,” said Elizabeth Stone, a professor at Iowa University.

It was previously known that large pollen grains at high humidity can break down into smaller “pollen particles”. It is also known that such particles can rise to the clouds and descend with raindrops and downdrafts.

Pollen fragments are significantly lighter than whole pollen grains, so they are more easily held in the air. But before, no one measured how long they could remain there. In a new study, scientists first presented direct evidence of the presence of a large number of these particles in the air after rain.

The study was conducted in April and May 2019. There were 28 rainy days in Iowa for two months, and severe storms and tornadoes were recorded.

Scientists found that the peak in the number of pollen particles occurred during the rain and the first minutes after it. Further, their concentration began to decline rapidly, but a small amount remained in the air for hours.

The largest number of pollen particles, which can cause severe symptoms in sensitive people, was observed in the air after thunderstorms.

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