As global activity grinds to a halt due to efforts to contain the COVID-19 pandemic, scientists have been tracking significant improvements in air quality worldwide, which one researcher says will translate into a reduction in thousands of premature deaths and illnesses caused by continued exposure to dangerous gases.

“One of the unexpected benefits of doing what we need to do to get the virus under control … (is it) has also led to large improvements in air quality,” said Marshall Burke, an earth system science professor at Stanford University. “These improvements have additional benefits for our health.”

Satellite imagery has shown how air quality has improved drastically in big cities across China as well as urban centres throughout Europe, the United States and Canada. Burke calculates that will translate into 50,000 fewer premature deaths over time in China alone, because of just two months of shutdown in places such as Wuhan, where the coronavirus outbreak originated.

“When you clean up the air, you see a reduction in mortality,” said Burke.

“It highlights the things we may want to change when we don’t have an epidemic.”

Throughout March, New Mexico-based Descartes Labs registered drastically reduced average levels of atmospheric nitrogen dioxide (NO2), a pollutant generated when automobiles burn fossil fuels such as gasoline.

“It’s a pretty good indicator of human economic activity,” said Krishna Karra, a data engineer at Descartes. “The data shows that the differences are quite dramatic (March 2020 compared to March 2019).”

Images captured by the European Space Agency’s Sentinel-5P satellite showed improved conditions last month versus higher levels seen the same time last year.

NO2 is part of a group of highly reactive gases called nitrogen oxides or NOx. Short-term exposure can lead to irritated respiratory systems, while prolonged exposure can aggravate respiratory diseases, particularly asthma, according to the U.S. Environmental Protection Agency.

Starting on March 13, scientists at Columbia University monitored the levels of pollutants in Manhattan.

They recorded a 10-per-cent drop in carbon dioxide, the gas most often linked to climate change, and methane, and an astounding 50 per cent drop in carbon monoxide, according to an article featured on the university’s Earth Institute website.

Scientists cautioned about how data collected through monitoring and satellite imagery is interpreted, because a variety of factors can affect pollutant levels, including weather, wind, humidity and time of day.

The World Health Organization estimates both that air pollution kills seven million people worldwide every year, and nine out of 10 people breath air containing high levels of pollutants.

“What we’ve seen from studies around the world is that if you improve air quality the most vulnerable seem to benefit the most,” Burke said.

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Scientists say improved air quality should not be viewed as a silver lining during a life-threatening global pandemic.

But the incremental improvements do show the kinds of shifts that can happen if we change our habits over time.

Burke said the biggest unknown is whether the changes will have any lasting effect. Historical data says not so much.

He said the crippling after-effects of an economic downturn usually lead to an upsurge in activity.

When government coffers dry up, funding is often cut from environmental initiatives first, he said. Governments may also look to ease environmental regulations to restart GDP growth.

“Most of the evidence suggests that, while recessions reduce emissions in the short run, they are very bad for climate-change in the long run,” he said.

“They slow down progress in getting broader action on climate change.”

Miriam Diamond, a professor in the University of Toronto’s Department of Earth Sciences, calls the slowdown a “very minor break.”

Once things go back to normal, “there’s an increase in deaths from heart attacks,” she said. “There are increased incidents of asthma attacks and a whole host of respiratory effects.”

She’s concerned that, once COVID-19 is under control, the focus will shift to getting the economic gears turning again, which would be a missed opportunity to “reset the dial.”

“We have to reset to a low-carbon economy,” she said. “Now is the time to put the money into investments that are going to help us in the future, rather than kill us.”

The outbreak is teaching us about the repercussions of delayed responses and why experts matter, she said. “The pandemic has taught us to listen to experts. We have the same type of experts with climate change, but they have not been afforded the level of respect.”

“What we can learn from COVID-19 responses is that rapid societal changes, from individual behaviour to governmental interventions, to reduce these detrimental substances, are possible,” said Madhur Anand, a professor of global ecological change and sustainability at the Guelph Institute for Environmental Research.

“I think seeing this change can help us better imagine solutions to the looming, and, perhaps even greater, environmental and human health crises to come.”

Jason Miller is a breaking news reporter based in Toronto. Reach him on email: jasonmiller@thestar.ca or follow him on Twitter: @millermotionpic

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