Climate change and the pollen season: human environmental impacts worsen allergies

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Climate change has already worsened pollen seasons in the United States and Canada, a new study spanning nearly three decades of data has found. The pollen seasons are getting longer and more intense.

According to the authors, the length of time people in North America are exposed to pollen, as well as the amount of pollen, have “increased dramatically” over the past decades.

Researchers looked at different pollen measurements between 1990 and 2018 from 60 monitoring stations across North America. Pollen seasons started up to 20 days earlier and lasted up to eight days longer, the scientists found.

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There was also an increase in the number of pollen or pollen concentration, with a 20.9% increase between 1990 and 2018 – and a 21.5% increase in the spring season alone.

“There is a huge body of research on how climate change is already affecting our health. Our study completes a key element linking climate change to pollen, which is one of the biggest contributors to asthma, allergies and respiratory health problems, “said William Anderegg, assistant professor of biology at the University of Utah and lead author of the study published Monday in the journal PNAS.

“It’s a clear example that climate change is here and now.”

Regional differences

The biggest and most consistent increases were in Texas and the Midwestern United States, the study found, which surprised Anderegg. He had expected to see a larger increase in pollen in the more northern states.

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He said the reason for this was not “entirely clear and that more research will be needed to unravel. One hypothesis could be that the plant species found there are particularly sensitive to warming and produce more pollen.”

The study looked at different factors behind this change, including changes in temperature, precipitation, freezing days, and carbon dioxide concentrations, and found that an increase in mean annual temperatures was the most important factor. important.

Using computer models of Earth’s climate, the researchers also calculated the extent to which human-caused climate change increased pollen concentrations and lengthened pollen seasons.

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“These computer models simulate a world without man-made climate change and a world with man-made climate change (ie the real world),” Anderegg said via email.

“By combining the observed relationship between pollen and temperature with these two different scenarios, we can estimate the extent to which human-caused climate change influences pollen trends.”

Longer pollen seasons

The researchers concluded that it was a “powerful engine” in terms of faster starts to the pollen season and longer seasons. However, this was a more modest factor when it came to higher pollen concentrations.

The contribution of human-induced climate change was more pronounced during the period 2003 to 2018 compared to the longer period from 1990 to 2018, the scientists said, likely reflecting both the cumulative effect of the climate change and a greater number of pollen monitoring stations during the shorter period.

The researchers also noted that the environmental impact of humans was more modest looking at the numbers for an entire year compared to the spring season, with some decreases in summer pollen counts indicating that the life cycles of some plant species had changed.

According to the United States Centers for Disease Control and Prevention, some 19.2 million adults have been diagnosed with hay fever – an allergic reaction to pollen, a fine powder of plants that can come in contact with the eyes, nose, mouth and throat.

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