The European Space Agency released new video this weekend that shows air pollution vanishing over China as the country goes into COVID-19 coronavirus lockdown, then returning as business resumes:
The animation, based on data from the Copernicus Sentinel-5P satellite, charts nitrogen dioxide, a noxious gas produced primarily by the burning of fossil fuels, over China from Dec. 20 to March 16.
“The drop in concentrations in late January is visible, coinciding with the nationwide quarantine,” the agency reports, “and from the beginning of March, the nitrogen dioxide levels have begun to increase.”
ESA mission manager Claus Zehner estimates NO2 dropped about 40 percent during the lockdown. NO2 reacts with other chemicals in the air to form particulate matter, and ESA also documented a drop in particulate matter over China:
“By combining satellite observations with detailed computer models of the atmosphere, their studies indicated a reduction of around 20-30 percent in surface particulate matter over large parts of China,” the agency reported Friday.
Both NO2 and particulate matter have been linked to heart and lung disease. Both the EPA and the World Health Organization have identified fine particulate matter, PM2.5, as the leading cause of death from air pollution.
Air pollution causes an estimated 1.1 million deaths per year in China and costs the Chinese economy $38 billion. Earlier this month Stanford Earth Sciences Professor Marshall Burke projected that two months of coronavirus lockdown had saved the lives of 77,000 Chinese children and elderly from air pollution alone.
Air pollution may also affect the mortality rate of COVID-19. Early analyses have identified hypertension as the leading simultaneous chronic disease (comorbidity) in patients who have died from COVID-19. Studies have linked air pollution, particularly NO2, to hypertension.
Both pollutants are known to impair lung function.
“Breathing air with a high concentration of NO2 can irritate airways in the human respiratory system,” according to the U.S. Environmental Protection Agency.
“Such exposures over short periods can aggravate respiratory diseases, particularly asthma, leading to respiratory symptoms (such as coughing, wheezing or difficulty breathing), hospital admissions and visits to emergency rooms. Longer exposures to elevated concentrations of NO2 may contribute to the development of asthma and potentially increase susceptibility to respiratory infections.”
NO2 is not a greenhouse gas, but greenhouse gases likely have seen a similar drop as lockdowns across the world shutter factories and reduce automobile traffic.
“As nitrogen dioxide is primarily produced by traffic and factories, it is a first-level indicator of industrial activity worldwide,” said Josef Aschbacher, ESA’s Director of Earth Observation Programmes.
The Copernicus Sentinel-5P satellite monitors air pollution by measuring a multitude of trace gases and aerosols. Last week the ESA released video of a pollution decline over northern Italy as that country entered lockdown:
Forbes Jeff McMahon