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Climate change is a major threat to public health.1 It increases both air pollution and pollen counts. Some groups are at a greater risk of feeling the effects of climate change than others, including people with chronic diseases like asthma and allergies.

May 1-5, 2023, is Air Quality Awareness Week. This week, the Environmental Protection Agency (EPA) and several other government agencies raise awareness about the importance of air quality.

During Air Quality Awareness Week, the Asthma and Allergy Foundation of America (AAFA) looks at the major impact climate change and air pollution have on people with asthma and allergies.

Climate Change and Seasonal Allergies

In AAFA’s 2023 Allergy Capitals™ report, we highlighted the dangerous cycle of climate change. As global temperatures rise, extreme weather events become worse. Weather changes – such as heat waves and droughts – can lead to stagnant air (a lack of airflow). When the air doesn’t move, pollutants react together in the heat and sun. This increases ground-level ozone.

Ground-level ozone is a major part of urban smog. More air pollution and smog cause higher levels of carbon dioxide (CO2). This results in warmer temperatures. And the cycle continues.

Warmer temperatures along with higher levels of CO2 make growing seasons longer. This allows plants more time to flower and produce pollen.

This climate change cycle causes longer and more intense allergy seasons. It also increases asthma and allergy triggers. This can make symptoms worse for people with seasonal pollen allergies and allergic asthma.

When looking at the connection between climate change and seasonal allergies, two factors have to be considered: botanical sexism and urban heat islands.

Botanical Sexism

Trees also play a role in climate change and seasonal allergies. Tree pollen is a common allergen. It has increased over the years more than grass or weed pollen.2 “Botanical sexism” is partly to blame. This is when communities choose to plant more wind-pollinating trees than fruiting trees. (Wind-pollinating trees are sometimes called “male” trees, and fruit-bearing trees are sometimes called “female” trees.) More wind-pollinating trees can lead to higher pollen.

Urban Heat Islands

Many of the health impacts of climate change are felt more in urban areas. Warmer temperatures and extreme heat waves are made worse in urban areas due to an effect called an “urban heat island” (UHI). A UHI is a metropolitan area that has higher temperatures than its surrounding areas.

The extreme heat makes air pollution and allergic sensitivity worse. Pollution from vehicles, power plants, and industry in cities can be very high and can impact pollen production. In fact, ragweed pollen has been found to be much higher in certain cities than in surrounding rural areas.3

Reducing the Impact of Climate Change

We need to slow the cycle of climate change to improve health of people with asthma and allergies. If we don’t act, pollen counts will only get higher, temperatures will continue to rise, and urban centers will continue to see the harsh effects of climate change.

To learn more about climate change and how we can reduce its impact, read the 2023 Allergy Capitals report.

The 2023 Allergy Capitals report is an independent research project of AAFA and is made possible by a research support grant from the Consumer Healthcare Products Association.

How Can I Learn More About the Report?

The Allergy Capitals™ ranking is an annual research and education project from AAFA. We release the report to help people recognize, prevent, and safely treat allergy symptoms. Through this ranking, AAFA raises awareness about the impact of seasonal allergies. It provides helpful information that can improve the quality of life for people living with seasonal allergies.

Visit to see the full list and to learn more about allergy diagnosis, prevention, and treatment.

Join our online community where you can get support for asthma and allergies and stay up to date on news and research.

1. Wuebbles, D.J., Fahey, D.W., Hibbard, K.A., et al. (2018). Fourth National Climate Assessment: Climate science special report. U.S. Global Change Research Program.
2. Climate Central. (2023). Seasonal allergies: pollen and mold. ae3024a9c4f2bcdd9b563d09b1bd07c3/ FINALSeasonal_allergies_pollen_and_mold_2023__ EN_.pdf
3. Ziska, L. H., Gebhard, D. E., Frenz, D. A., Faulkner, S., Singer, B. D., & Straka, J. G. (2003). Cities as harbingers of climate change: Common ragweed, urbanization, and public health. Journal of Allergy and Clinical Immunology, 111(2), 290–295.

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