Since the COVID-19 pandemic began, space- and ground-based observations have shown that Earth’s atmosphere has seen significant reductions in some air pollutants. Nitrogen dioxide is an air pollutant that is primarily produced by the combustion of fossil fuels used by industry and transportation—both of which were significantly reduced during the height of the pandemic to prevent the novel coronavirus from spreading, NASA researchers have found.
Data from at least 46 countries were used, including a total of 5,756 observation sites. In at least 50 of the 61 cities that were used for emission analysis, a significant reduction in nitrogen dioxide’s release, between 20-50 percent, was noted.
“In some ways, I was surprised by how much it dropped,” said Keller. The NO2 emission was dropped to 60 percent lower than simulated values, a 60 percent decline was found in Milan, and a 45 percent decrease in New York.
“We all knew the lockdowns were going to have an impact on air quality,” Christoph Keller, the lead author of the study, said in a statement.
“It was also soon clear that it was going to be difficult to quantify how much of that change is related to the lockdown measures, versus general seasonality or variability in pollution,” he added.
The report suggests that Wuhan, the first epicentre of the coronavirus outbreak, was also the first to show reduced nitrogen dioxide emissions. The study showed 60 per cent lower emissions than simulated values expected. As the restrictions were imposed in Milan and New York, the cities recorded a 60 per cent and a 45 per cent decrease respectively.
Emma Knowland, a co-author, stated that at times, a decrease in air pollutants was recorded even before the official policies went into place. ”people were probably reducing their transit because the talk of the Covid-19 threat was already happening before they were actually told to shut down”, Knowland stated.