Research Press Release

Environment: COVID-19 lockdowns improve air quality in China

Nature Sustainability

July 7, 2020

The Air Quality Index (a measurement of air pollution) and fine particulate matter decreased by 19.84 points and 17%, respectively, in Chinese cities locked down to prevent the spread of COVID-19, suggests a modelling paper in Nature Sustainability. The air quality also improved in cities without formal lockdowns — although not as notably — as a result of other types of counter-virus measures, such as enforcing quarantines, prohibiting private and public gatherings and restricting transportation.

To prevent the spread of COVID-19, China locked down 95 of the 324 cities included in the study, strictly restricting personal mobility and economic activities. These preventative measures may incur significant costs; however, they could also significantly improve the quality of the environment in the short term.

Guojun He, Yuhang Pan, and Takanao Tanaka, analysed day-by-city data from 1 January to 1 March 2020. They collected air quality data from 1,600 monitoring stations covering all the prefectural cities in China and combined the station-level data with the city-level data. They then collected the local government’s lockdown policies city by city from news media and government announcements. The authors used econometric models to quantify the effect of lockdown measures on air pollution. They found that the Air Quality Index dropped by 19.84 points and particulate matter with a diameter less than 2.5 micrometers (PM2.5) by 17% in locked-down cities within a matter of weeks, compared to cities not under lockdown. The Air Quality Index also improved in cities not under lockdown by 6.34 points, while PM2.5 improved by 7% compared to the previous year. The authors also found that the effects of lockdown were larger in colder, richer and more industrialized cities.

Despite these improvements, the PM2.5 concentration during lockdown periods remained four times higher than the World Health Organization recommendations. The authors argue that environmental policies could obtain similar improvements in air quality at a much lower economic cost than city-wide lockdowns, suggesting that city lockdowns are an unsustainable option in addressing environmental issues.


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