The coronavirus (COVID-19) epidemic is first and foremost an issue of human health and safety. But as people have changed their everyday behaviors and patterns to contain or avoid the virus, there have been some subtle effects on the environment. There also has been misinformation. Below are four ways the virus is—and is not—affecting the environment in China.

1. Satellites found decreases in one air pollutant, but that doesn’t mean the air is free of all pollution.

On February 28, we reported how decreases in industrial, transportation, and business activity since the coronavirus outbreak had reduced levels of atmospheric nitrogen dioxide (NO 2 ) over China. But researchers note that a measurable change in one pollutant does not necessarily mean air quality is suddenly healthy across the country.

In February, news outlets reported unhealthy air pollution in Beijing, which was largely affected by airborne particulate pollution known as PM 2.5. As reported in the South China Morning Post, “weak winds, high humidity and a strong thermal inversion had trapped bad air in the city.” NASA satellites also showed a high load of airborne aerosols. Measurements of aerosol optical depth depict how the abundance of natural or manmade particles in the air prevents light from traveling through the atmosphere to the ground.

Beyond aerosol emissions, weather also plays an important role in determining air quality. NASA/USRA researcher Fei Liu notes that wind patterns and the height of the planetary boundary layer — the lowest layer of the troposphere near Earth’s surface — are important meteorological factors. Planetary boundary layer height influences how air pollution mixes vertically in the atmosphere. If the height of the boundary layer is high, then air pollutants can move higher into the atmosphere and concentrations will be lower near the ground (and vice versa). Liu and her colleagues are currently studying how changes in such meteorological factors may have influenced the decrease in NO 2 before and during the quarantine.

For more information on NASA’s long-term measurements of nitrogen dioxide, please see this page.

2. During the quarantine, roads and transportation hubs are emptier.

Street traffic cleared out near the Wuhan train station during the quarantine. Image credit: Planet Labs Inc.

It is no surprise that road traffic in China’s major cities has been lighter, as many people have been forced to stay home and public transportation has been shut down. Satellite imagery from Planet Labs captured scenes of reduced traffic and empty parking lots near the Wuhan train station and airport. Trains stopped running around January 22, when the first quarantines began. And compared to late January 2019, domestic flights within mainland China this year dropped by 60 to 70 percent.

Bridge traffic disappeared during the quarantine. Image credit: Planet Labs Inc.

3. Coal and oil industrial activities have dropped, so carbon dioxide emissions have also decreased.

A report in Carbon Brief stated that key industries in China were operating at much lower-than-normal levels during the quarantine. Oil refinery operations in Shandong province, for instance, were at their lowest since 2015. Average coal consumption at power plants also reached a four-year low. As a result, carbon dioxide (CO 2 ) emissions were at least 25 percent lower in the two weeks following the Lunar New Year compared to 2019. However, that decrease in CO 2 emissions for two weeks would only reduce annual totals by approximately 1 percent.

Image credit: Carbon Brief

4. There is no evidence that cremation ashes are increasing the levels of sulfur dioxide in the atmosphere.

In February 2020, a map floating around on social media showed increased sulfur dioxide (SO 2 ) concentrations near Wuhan. Some news outlets prematurely speculated that the elevated levels of SO 2 were due to an increase in human cremation.

The data for the map came from NASA’s GEOS earth system model and were not based on real-time observations of SO 2 . NASA’s Arlindo da Silva explained that while the GEOS model assimilates many ground-based and satellite observations to constrain meteorological conditions such as winds, humidity, and temperature, it currently does not ingest any real-time observations of sulfur dioxide. In the model, the concentrations of SO 2 are estimated from historical emissions sources that are transported around the globe by atmospheric circulation. Therefore, da Silva said, GEOS model simulations cannot account for variations in SO 2 concentrations arising from a sudden change in human activity (like a quarantine). Essentially, the model output of enhanced SO 2 was not completely reflecting reality in this case.

Secondly, as the writers at Snopes pointed out, sulfur dioxide is commonly associated with burning coal — not burning human corpses.