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Many cities under pandemic lockdown recording 40% drops in air pollution


Air pollution levels are dropping at unprecedented rates with multiple studies revealing a drastic drop in PM2.5 pollution for most global locations under pandemic lockdown.

Nine of 10 key global cities experienced PM2.5 reductions over the same period in 2019, according to a new report from researchers at IQAir — a Swiss-based global air quality technology company that selected cities with relatively high numbers of coronavirus cases and strict COVID-19 lockdown measures.

“In many places, the halt of movement and industry has shown a glimpse of a cleaner world, with many reports of exceptional blue skies,” states the report’s introduction. “However, visual perception alone can be deceiving when observing air pollution.”

The report’s findings show that cities with historically higher levels of PM2.5 pollution experienced the most substantial drops in air pollution under lockdown, including Seoul, South Korea (-54%) and Wuhan, China (-44%). The Indian capital New Delhi — which frequently tops the world’s most polluted city lists — saw a 60% reduction in PM2.5 levels from March 23 to April 13 over the same period in 2019.

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IQAir’s findings are being supported by other researchers as well, including the University of Toronto’s Marc Cadotte, a professor in the department of biological sciences at U of T Scarborough. Cadotte has analyzed air quality indexes (AQI) for six COVID-19-affected cities, including Wuhan, Hong Kong, Kyoto, Milan, Seoul and Shanghai.

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

Air quality changes map
Map Source: IQAir.

Notably, some cities experienced larger declines in specific types of pollution compared to others. For nitrogen dioxide, Shanghai experienced the largest decline of the six, whereas Seoul experienced its largest decline in sulfur dioxide.

“When it comes to major air pollutants, it depends on what’s being produced locally,” said Cadotte. “In some places they may already have really high or relatively low levels of a specific pollutant,” he added.

Cadotte also looked at the AQI from 11 cities that didn’t declare a state of emergency in February, finding that those cities didn’t experience the same decline in air pollution concentrations as the six that did.

Toronto recording a 40% drop

For Ontario, Hind Al-Abadleh, a chemistry professor and chair of the environment division at the Chemical Institute of Canada, has been studying the impact of the pandemic on air quality in the province. Her data comes from provincial air quality stations in four Ontario metropolitan areas, starting from January until April 10. Her preliminary results show there’s been:

  • A 40% reduction in nitrogen dioxide in Kitchener
  • Between a 30 and 40% reduction in Toronto (the west end of the city rates better than downtown)
  • A 40% reduction in Ottawa

Studies are also underway to determine if there are links between cities with severe air pollution, where lung health may be generally compromised, and deaths from COVID-19.


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