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. 2021 May 21;7(21):eabe1178.
doi: 10.1126/sciadv.abe1178. Print 2021 May.

Air pollution impacts of COVID-19-related containment measures

Guillaume P Chossière  1 , Haofeng Xu  1 , Yash Dixit  1 , Stewart Isaacs  1 , Sebastian D Eastham  1   2 , Florian Allroggen  1   2 , Raymond L Speth  1   2 , Steven R H Barrett  3   2   4
Affiliations

Air pollution impacts of COVID-19-related containment measures

Guillaume P Chossière et al. Sci Adv. .

Abstract

Responses to the COVID-19 outbreak resulted in one of the largest short-term decreases in anthropogenic emissions in modern history. To date, there has been no comprehensive assessment of the impact of lockdowns on air quality and human health. Using global satellite observations and ground measurements from 36 countries in Europe, North America, and East Asia, we find that lockdowns led to reductions in NO2 concentrations globally, resulting in ~32,000 avoided premature mortalities, including ~21,000 in China. However, we do not find corresponding reductions in PM2.5 and ozone globally. Using satellite measurements, we show that the disconnect between NO2 and ozone changes stems from local chemical regimes. The COVID-related lockdowns demonstrate the need for targeted air quality policies to reduce the global burden of air pollution, especially related to secondary pollutants.

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Figures

Fig. 1
Fig. 1. Changes in population-weighted, regionally averaged NO2 concentration per unit lockdown policy stringency index based on ground monitor data.
Countries in dark gray are not included in the analysis due to the unavailability of monitor data. Hatched regions lack data on more than 10% of the days from 1 January 2016 to 6 July 2020 and are excluded from the results. In dotted regions, changes in population exposure to NO2 with stringency are not statistically significant at the 5% level.
Fig. 2
Fig. 2. Changes in ozone as a function of the HCHO-to-NO2 ratio.
(A) Changes in ozone by region as a function of the HCHO-to-NO2 ratio. Circles, squares, and triangles represent European regions, Chinese provinces, and U.S. states, respectively, where NO2 decreases are found to be statistically significant. (B) Cumulative share of the regions in the “extended transition regime” (1 < HCHO/NO2 < 4) with a decrease in ozone as a function of the HCHO-to-NO2 ratio based on pre-lockdown conditions. We find a gradual transition regime between a HCHO-to-NO2 ratio of 1 and 4. The blue line can be interpreted as the probability that a region at a given HCHO-to-NO2 ratio will experience a decrease in ozone given a decrease in NO2. Not all regions with reduced NO2 due to the lockdown have reduced ozone, as HCHO levels also vary (figs. S5 and S6).
Fig. 3
Fig. 3. Mortality rate per million people due to COVID-19 (gray) and air quality improvements due to COVID-19–related lockdown measures (blue).
All pollutants (PM2.5, NO2, and ozone) are included.
See this image and copyright information in PMC

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