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Atmospheric Chemistry

Air quality alerts to quadruple by 2100

Researchers say adaptation and mitigation policies are needed to reduce associated health risks

by Krystal Vasquez
January 25, 2024 | A version of this story appeared in Volume 102, Issue 3


Smoggy Los Angeles skyline backlit by the sun.
Credit: Shutterstock
Climate change may lead to a rise in air quality alerts.

The frequency of air quality alerts in the US is on track to quadruple by 2100 as a result of climate change, according to a new study (Proc. Natl. Acad. Sci. U.S.A. 2024, DOI: 10.1073/pnas.2215685121). To avoid the health risks associated with this surge in high pollution events, people will be advised to to stay indoors for 142 more days per year than they would today, researchers estimate.

Air quality alerts for the general public are triggered when the air quality index (AQI) reaches a threshold of 150 or above. “AQI is a measure of how bad the air is, and it’s dependent on the outdoor concentrations of a variety of pollutants,” explains Rebecca Saari, a professor of civil and environmental engineering at the University of Waterloo and one of the study’s authors.

For the study, Saari and her colleagues focused on alerts driven by one pollutant in particular, fine particulate matter, or PM2.5. “That’s the pollutant that contributes most to the human health burden,” she says.

Previous work has shown that climate change can raise PM2.5 concentrations by shifting precipitation patterns, increasing atmospheric stagnation, and changing atmospheric chemistry reactions rates (Earth’s Future 2019, DOI: 10.1029/2019EF001195). Long-term exposure to PM2.5 has been linked to heart attacks, stroke, and premature death.

The researchers acknowledge that it’s unrealistic to ask people to respond to more frequent air quality alerts by staying indoors for nearly 40% of the year. “Currently, only 15 to 20% of Americans are aware of alerts and take some steps,” Saari says.

In addition, not everyone can restrict outdoor activity. Some people must work outdoors. Others, particularly those in lower-income neighborhoods, live in “leakier” homes that let more outdoor pollution inside.

Government policies can potentially encourage more people to stay indoors by providing compensation and boosting awareness of health risks. Improving building quality can also ensure that everyone has access to clean indoor air.

But in addition to adaptive measures, policies that mitigate climate change are necessary, Saari says. “Mitigation is able to protect people regardless of whether they attempt to adapt. We need to do both.”



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