Air Pollution Sharply Fell as the COVID-19 Lockdowns Curtailed the Economy in China

Urban air quality still remained four times higher than WHO recommended levels in cities during the first COVID-19 lockdown in China, despite substantial pollution reductions and the high costs of the measure.

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The rapid spread of COVID-19 is an unprecedented global public health and economic challenge, causing millions of people infected and massive layoffs. However, in early March, there was speculation that this crisis may have brought a substantial social benefit: the strict virus containment measures might have reduced air pollution dramatically, as caught by NASA’s satellite images.

Source: NASA earth observatory

Reducing air pollution is one of the primary environmental goals. According to the World Health Organization, seven million deaths worldwide can be attributed to air pollution each year. Therefore, considerable efforts have been devoted by policymakers and researchers to find an efficient way to reduce such an environmental threat. All of a sudden, although COVID-19 and air pollution seem to be totally irrelevant, the goal might have been partially achieved. However, there was much unknown to us. What are the overall impacts of COVID-19 outbreak and strict countermeasures on air pollution? In which channels do these measures affect air quality? And, how can we interpret the findings if we find a significant reduction in air pollution? 

Looking backward, I thought it would be very interesting to examine this issue as our team intensively work on environmental issues. Our team agreed, and soon we kicked off this project. Y. Pan, another Ph.D. student, immediately collected an impressive dataset covering air pollution data from more than 1,600 monitoring stations, and lockdown status on all Chinese provincial cities (324 cities), and conducted initial analyses. I wrote the manuscript, and Prof. G. He raised some insightful discussions and polished the paper. Thankfully, we were able to submit this paper in three weeks from its start.   

In this paper, focusing on China, which locked down one-third of its cities (95 cities), we find that these measures brought about a notable reduction in air pollution. Within weeks, the Air Quality Index (AQI) was brought down by 19.84 points (PM2.5 by 14.07 µg/m3) relative to non-locked-down cities. Even if cities are not locked-down, the government also took some virus containment measures, and AQI in these cities was also brought down by 6.34 points (PM2.5 by 7.05 µg/m3) compared to the previous year. The effects of city lockdowns are larger in colder, richer, and more industrialized cities.

Notes: These graphs show how air pollution changed over time, responding to the virus containment measures. The left figure compares AQI in locked-down cities and non-locked down cities, suggesting AQI dropped (thus, air quality improved) in locked-down cities. The right graph shows that, compared to last year, AQI in non-locked-down cities also declined.

When we reached the conclusions, however, we encountered a great challenge: what general lessons could be learned. Undoubtedly, the improvement in air quality should be beneficial to society. Indeed, in a separate project collaborating with the Chinese CDC and Beijing University, we find that lockdown substantially decreased non-COVID-19 mortality, which is even one magnitude larger than the direct deaths from the COVID-19. However, lockdown also imposed so much pain on our economy, and we were uncertain if such measure was plausible. We, therefore, compared its effects to ones from the past environmental regulations. The comparisons tell that one should never choose city lockdown as an option to improve environmental quality. Many regulations, such as the environmental regulations during the Bijing Olympics and the emission standard, could have achieved comparable improvement in air quality at a much lower economic cost. 

Also, our findings initially seemed to be puzzling because the lockdown effects appeared to be much smaller than expected. In locked-down cities, the PM2.5 concentration had been around 75 µg/m3. After its implementation, the level still remained as high as 40 µg/m3, which is four times higher than WHO recommendations (10 µg/m3). Alarmingly, even when every unessential industrial activity is stopped, people in China still needed to breathe very dirty air. We point out that many cities still rely on inefficient coal central heating, and this may worsen its air quality. In 2014, China declared “War on Pollution,” and progressive efforts have been made in recent years. Our study suggests that, for the nation to win its war, exclusive measures in both the industrial sector and the residential sector should be inevitable. 

Again, the COVID-19 is an unprecedented global public health and economic challenge. Our study only focuses on China in the very short-term (January 1st – March 1st in 2020), To understand the overall welfare consequences of the pandemic and to obtain meaningful lessons for a sustainable society, we believe much further research is warranted.

Article: He, G., Pan, Y. & Tanaka, T. The short-term impacts of COVID-19 lockdown on urban air pollution in China. Nat Sustain (2020). https://doi.org/10.1038/s41893-020-0581-y

Takanao Tanaka

Mphil Student, Hong Kong University of Science and Technology

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