Air quality improved 40% in cities that adopted social distancing

Hyperaxion Apr 16, 2020

Regions that declared a state of emergency in February on behalf of Covid-19 had a significant reduction in air pollution levels.

The level of air pollution decreased by 40% in cities that declared a state of emergency in February due to the Covid-19 pandemic. That was the conclusion of a research conducted by Marc Cadotte, a professor at the University of Toronto, Canada, which focused on six cities: Wuhan, Hong Kong, Kyoto, Milan, Seoul and Shanghai.

Air quality improved 40% in cities that adopted social distancing
Seoul, capital of South Korea. (Credit: Pexels).

The researcher compared the air quality index (AQI) of the six cities in February 2019 with the measurements made in February this year, when actions in response to the pandemic had already been implemented. “You’re looking at anywhere from a 20 to 40% decline in air pollution levels,” said Cadotte in a statement. “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.”

AQI is used to measure air quality on a scale from zero (least dangerous) to 500 (most dangerous). The index tracks the concentrations of the five main air pollutants: carbon monoxide, sulfur dioxide, nitrogen dioxide, airborne particles, ground-level ozone, and particulates.

According to Cadotte, the benefit of this system is that it is directly linked to human health. For example, if the AQI is greater than 101, people with heart or respiratory diseases are advised to stay at home.

In the study, the researcher also analyzed the AQI of 11 cities that did not declare a state of emergency in February because of the new coronavirus pandemic. Cadotte found that these cities, unlike those that implemented social distancing, did not experience the same decline in air pollution concentrations.

Cadotte believes that the decline in AQI in these regions is the result of reduced human and economic activities. In addition, in each city analyzed, the reduction in pollutant levels varied from place to place.

While in Shanghai, nitrogen dioxide was the most reduced, in Seoul the biggest decline was in the level of sulfur dioxide. “When it comes to major air pollutants, it depends on what’s being produced locally,” explained Cadotte.

The professional also stressed that the drop in AQI rates should not interfere much in global warming, but it can contribute to raising awareness among governments around the world about measures that can be taken to prevent climate change.

“We are making these very difficult, but very responsible, decisions about limiting human and economic activity in order to save lives. At the same time, we’re subsidizing industries that produce air pollution or use vehicles that pollute, which we know contribute to millions of premature deaths a year,” said Cadotte. “This may be overly optimistic, but maybe what the pandemic will show us is that governments can take more direct action to combat other factors that we know cause high mortality rates.”


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