COVID-19 has spread rapidly from China to the rest of the world. Thousands of lives have been lost and the pandemic has all but crashed the global stock market. China closed its factories, transportation systems and locked down major cities to slow the spread of the virus, and the country’s GDP is expected to drop a few percentage points this year. It may be tough to be optimistic, but an unexpected benefit of COVID-19 is the decrease in greenhouse gas emissions. 

Satellite images from NASA have shown that a drop in industrial and economic activities has resulted in reduced greenhouse gas emissions and improved air quality in Wuhan, the epicentre of the COVID-19 outbreak, over the Chinese New Year. Levels also dropped in Beijing and Hebei province, as well as Shanghai and the Yangtze River Delta region. 

The images show that pollution dropped, and didn’t rebound after the holiday. The level of PM2.5, dangerous small pollution particles, fell by 25%, while nitrogen dioxide, produced mainly by diesel vehicles, dropped by 40%. Nitrogen dioxide produces ozone, which, on the ground, is detrimental to human health, causing asthma, lung cancer and other respiratory and pulmonary illnesses. 

COVID-19 Reveals Unexpected Benefit- Reduced Emissions
Satellite images showing nitrogen dioxide emissions from January 1 2019 to February 25 2020 (Source: NASA).

PM2.5 is responsible for more than one million premature deaths in China annually and for the reduction of crop yields.

In February, during the peak of the outbreak in China, the nation’s carbon emissions dropped by about 100 million tonnes, accounting for more than 25% of carbon dioxide emissions since the outbreak began compared to the same period in 2019, roughly 6% of global carbon dioxide emissions. 

Similar drops in emissions were seen during the 2008 Olympics held in Beijing, when the government implemented measures to decrease air pollution. Measures included replacing high-emitting vehicles with increased public transportation options, shutting down some chemical plants in Beijing, raising the price of gasoline to discourage the use of cars and requiring power and chemical plants to decrease emissions by 30%. These measures caused a sudden and sharp decrease in air pollution levels in Beijing and nearby cities. The particulate matter in the air in the city decreased by an average of 18% during 2008. 


Italy has seen the greatest number of combined cases of COVID-19 of any country outside China. Public spaces have since been closed throughout the country. As people have stayed home, nitrogen emissions in Italy, particularly in the northern regions, have fallen. The European Space Agency’s Copernicus Sentinel-5P satellite tracks air pollution in the atmosphere, and the satellite has seen a sharp decrease in emissions of nitrogen dioxide over Italy since the beginning of the year. 

“Although there could be slight variations in the data due to cloud cover and changing weather, we are very confident that the reduction in emissions that we can see coincides with the lockdown in Italy causing less traffic and industrial activities,” Claus Zehner, the mission’s manager at ESA, said in a statement. 

COVID-19 Reveals Unexpected Benefit- Reduced Emissions
Images showing the decrease in nitrogen dioxide emissions over Italy from January 31 to March 8 2020 (Source: Copernicus Sentinel data processed by the ESA).

There have also been sightings of swans and fish in the port and canals of Venice due to the lack of gondolas, cruise ships and noise pollution in the city. 

The UK

While behind Italy in terms of the spread of the disease, roadside monitors in the UK are already showing significant reductions in levels of pollution. Road traffic accounts for about 80% of nitrogen oxide emissions in the UK and for the average diesel car, each km not driven prevents 52 mg of the substance entering the atmosphere. 

COVID-19 Reveals Unexpected Benefit- Reduced Emissions
Satellite data showing a reduction in the presence of nitrogen oxide over Europe (Source: Copernicus Sentinel data processed by the ESA).

Air Pollution Likely to Increase Coronavirus Death Rate

Experts have said that the health damage inflicted on people by long-standing air pollution from greenhouse gas emissions in cities is likely to increase the death rate from COVID-19 infections. 

Dirty air can cause lung and heart damage, and is responsible for at least 8 million early deaths a year. This means that respiratory infections, such as COVID-19, may have a more serious impact on those in cities and exposed to toxic fumes than others. 

Strict confinement measures in China and Italy have led to falls in air pollution. A preliminary calculation by a US expert suggests that tens of thousands of premature deaths from air pollution may have been avoided by the cleaner air in China. 

“Patients with chronic lung and heart conditions caused or worsened by long-term exposure to air pollution are less able to fight off lung infections and more likely to die. This is likely also the case for Covid-19,” said Sara De Matteis, at Cagliari University, Italy, and a member of the environmental health committee of the European Respiratory Society. “By lowering air pollution levels we can help the most vulnerable in their fight against this and any possible future pandemics.”

Scientists who analysed the SARS coronavirus outbreak in China in 2003 found that infected people who lived in areas with more air pollution were twice as likely to die as those in less polluted places. 

According to the Global Exposure Mortality Model (GEMM) developed by Bernett et al., (2018) scientists are now able to estimate the number of premature deaths from air pollution, as well as the number of premature deaths prevented because of reduced pollution levels.  

COVID-19 Reveals Unexpected Benefit- Reduced Emissions
GEMM describes the magnitude of the association between PM2.5 exposure and the probability of death in a concentration-response relationship known as the Hazard Ratio (Source: Bernett et. al, 2018).

It is estimated that the 3 weeks of reduced emissions in China during the COVID-19 outbreak may have saved 77 000 lives in the nation, mainly in the industrial region where the exposure to PM2.5 would have been highest. The actual number of lives saved may be a lot higher because people are staying at home more, which reduces their exposure to air pollutants significantly. However, it is important to note that this is difficult to quantify as it is purely statistical and associated illnesses from air pollution have long-term effects. The number of traffic accidents have also dropped. Even without the reduced emissions, the policy that made the wearing of masks in public spaces compulsory has also helped reduce exposure to pollutants; the masks also help to prevent the spread of the common cold and flu as shown by research in Hong Kong.

The experts are quick to clarify, however, that these claims are not to say that the pandemic can be seen as good for health. 

The aggressive measures taken by China and Italy to contain the COVID-19 outbreak that have resulted in reduced emissions show that it is possible to reduce emissions on a mass scale. However, the outbreak has also caused a large drop in fossil fuel demand, lowering the oil price, which may hinder the development of renewable energy.