Short-term change in air pollution following the COVID-19 state of emergency: A national analysis for the United States

Abstract Lockdown measures taken in response to the COVID-19 pandemic produced sudden social and economic changes. We examined the extent of air pollution reduction that was attained under these extreme circumstances, whether these reductions occurred everywhere in the US, and the local factors that drove them. Employing counterfactual time series analysis based on seasonal autoregressive integrated moving average models, we found that these extreme lockdown measures led to a reduction in the weekly PM2.5 average by up to 3.4 µg m-3 and the weekly NO2 average by up to 11 ppb. These values represent a substantial fraction of the annual mean NAAQS values of 12 µg m-3 and 53 ppb, respectively. We found evidence of a statistically significant decline in NO2 concentrations following the state-level emergency declaration in almost all states. However, statistically significant declines in PM2.5 occurred mostly in the West Coast and the Northeast. Certain states experienced a decline in NO2 but an increase in PM2.5 concentrations, indicating that these two pollutants arise from dissimilar sources in these states. Finally, we found evidence that states with a higher percentage of mobile source emissions prior to the emergency measures experienced a greater decline in NO2 levels during the pandemic. Although the current social and economic restrictions are not sustainable, our results provide a benchmark to estimate the extent to which air pollution reductions can be achieved. We also identify factors that contributed to the magnitude of pollutant reductions, which can help guide future state-level policies to sustainably reduce air pollution.Significance statement We quantified the reduction in air pollution levels achieved under the extreme social and economic measures that were put into place as part of COVID-19 state-level emergency declarations. We found a reduction in the weekly average PM2.5 of up to 3.4 µg m-3 and the weekly average of NO2 of up to 11 ppb. These values represent a substantial fraction of the annual mean NAAQS values of 12 µg m-3 and 53 ppb, respectively. States with a larger fraction of mobile source emissions (e.g., air and road traffic) prior to the pandemic experienced larger declines in NO2 emissions, whereas PM2.5 decline was seen in areas with a higher pre-pandemic proportion of emissions from mobile, stationary (e.g., industrial) and fire sources..

Medienart:	Preprint

Erscheinungsjahr:	2021
Erschienen:	2021

Enthalten in:	bioRxiv.org - (2021) vom: 01. Feb. Zur Gesamtaufnahme - year:2021

Sprache:	Englisch

Beteiligte Personen:	Tyagi, Pooja [VerfasserIn] Braun, Danielle [VerfasserIn] Sabath, Benjamin [VerfasserIn] Henneman, Lucas [VerfasserIn] Dominici, Francesca [VerfasserIn]

Links:	Volltext [kostenfrei]

doi:	10.1101/2020.08.04.20168237

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PPN (Katalog-ID):	XBI018503667