Air quality improves by up to 40% in cities that took action on COVID-19, researcher finds


Cities that declared a state of emergency in February due to outbreaks of COVID-19 saw air pollution decrease by up to 40% as businesses close their doors and residents stayed home, a University of Toronto researcher has found.

Marc Cadotte, a professor in the department of biological sciences at U of T Scarborough, looked at the air quality index (AQI) for six COVID-19-affected cities (Wuhan, Hong Kong, Kyoto, Milan, Seoul and Shanghai) that implemented emergency measures in February. He then compared the AQI for those cities to the same month in 2019, finding that all six showed a significant reduction in air pollution concentrations this year.

Cadotte’s study, which has not yet been peer-reviewed, is available on the Environmental Sciences preprint website.

“You’re looking at anywhere from a 20 to 40% decline in air pollution levels,” says Cadotte, an expert on urban ecology and biology.

“There’s been a significant increase in the number of days that can be categorized as good air quality versus polluted in the air quality index.”​HELP US SPREAD GOOD NEWS!

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