March 22, 2022

2 min read

Source / Disclosures

Disclosures: The authors report no relevant financial disclosures. Rothenberg reports consultant roles with Adare / Ellodi Pharma, Allakos, AstraZeneca, Celgene, ClostraBio, GlaxoSmithKline, Guidepoint, PulmOne, Serpin Pharma and Spoon Guru; holding equity interest in Allakos, ClostraBio, PulmOne, Serpin Pharma and Spoon Guru; royalties from reslizumab (Cinqair, Teva Pharmaceuticals), Pediatric Eosinophilic Esophagitis Symptom Severity Module version 2.0 (Mapi Research Trust) and UpToDate (Wolters Kluwer); and inventing patents owned by Cincinnati Children’s Hospital Medical Center.

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Increasing temperatures as part of climate change will lead to earlier and longer pollen seasons by the end of the century, impacting allergy and asthma outcomes, according to a study published in Nature Communications.

“Pollen-induced respiratory allergies affect up to 30% of the world population, and the increasing pollen emissions with climate change may worsen these allergies,” Yingxiao Zhang, a graduate student research assistant in climate and space sciences and engineering at University of Michigan, told Healio.

Allison Steiner, PhD, and Yingxiao Zhang discuss their work. Credit: Marcin Szczepanski

“Our work was designed to understand how we can better simulate pollen emissions and how it may change in the future,” Zhang said.

Working with Allison L. Steiner, PhD, professor of climate and space sciences and engineering, Zhang developed a model predicting how changes in temperature and precipitation will impact the production of 13 of the most common types of pollen between 2081 and 2100.

According to the model, which was based on United States data from 1995 to 2014, the pollen season will start up to 40 days earlier and last up to 19 days longer due to expected temperature changes of 4 ° K to 6 ° K.

These changes in temperature, as well as expected increases of up to 30% in daily spring and winter precipitation, will alter daily pollen emission maxima by -35% to 40%, while changes in phenology and temperature-driven pollen production will increase yearly total pollen emission by 16% is 40%.

Specifically, the researchers project warmer temperatures in the south and decreased precipitation intensity in the southwest. They also expect 30% greater maximum emissions for grass pollen and 10% greater maximum emissions for ragweed pollen in the south than in the north.

Surprisingly, Zhang said, the researchers also “found out that in the regions rich with pollen-emitting trees, individual types of trees may overlap and emit at the same time, leading to an increase in the total pollen concentration.”

When the researchers factored an expected carbon dioxide increase of 700 ppm by the end of the century into the model, though, they predicted maximum daily pollen production to increase by up to 200% and annual total pollen emission to increase by 250%.

“In the future, with the high carbon-dioxide emission scenario, carbon dioxide may become a more important factor than temperature that increases pollen production,” Zhang said.

The researchers cautioned, however, that predictions about the effects of carbon dioxide on pollen production are largely uncertain, noting that there has only been an increase of 50 ppm in carbon dioxide over the past 50 years compared with their expectation of 700 ppm.

Changes in land cover will impact how pollen emitters will be distributed, the model also determined, but these effects will be relatively small (<10%) compared with the impact of climate or carbon dioxide on pollen production, the researchers wrote.

Additional climate changes and anthropogenic impacts will shift the distribution of plant communities, further influencing pollen emissions, the researchers continued.

For example, the model predicts more tree coverage in the central US and Mississippi River Valley at the expense of crop coverage, with decreased tree coverage in the high altitudes of the Rockies and Pacific Northwest.

“With a longer and more intense pollen season and higher pollen load, more people may become sensitive to pollen, and people already allergic to pollen may have worse symptoms,” Zhang said.

The researchers are now collaborating with a lab in Boulder, Colorado, to incorporate their pollen model in the lab’s air quality forecasting system to be able to forecast daily pollen counts in different regions.

“We hope to further develop the model to better account for interannual variability, or the year-to-year changes in pollen amount, to improve its climate sensitivity,” Zhang said.


For more information:

Yingxiao Zhang can be reached at

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