Hammer, Melanie S.Donkelaar, Aaron vanMartin, Randall V.McDuffie, Erin E.Lyapustin, AlexeiSayer, AndrewHsu, N. ChristinaLevy, Robert C.Garay, Michael J.Kalashnikova, Olga V.Kahn, Ralph A.2023-11-012023-11-012021-06-23Hammer, Melanie S., Aaron van Donkelaar, Randall V. Martin, Erin E. McDuffie, Alexei Lyapustin, Andrew M. Sayer, N. Christina Hsu, et al. “Effects of COVID-19 Lockdowns on Fine Particulate Matter Concentrations.” Science Advances 7, no. 26 (June 23, 2021): eabg7670. https://doi.org/10.1126/sciadv.abg7670.https://doi.org/10.1126/sciadv.abg7670http://hdl.handle.net/11603/30479Lockdowns during the COVID-19 pandemic provide an unprecedented opportunity to examine the effects of human activity on air quality. The effects on fine particulate matter (PM₂.₅) are of particular interest, as PM₂.₅ is the leading environmental risk factor for mortality globally. We map global PM₂.₅ concentrations for January to April 2020 with a focus on China, Europe, and North America using a combination of satellite data, simulation, and ground-based observations. We examine PM₂.₅ concentrations during lockdown periods in 2020 compared to the same periods in 2018 to 2019. We find changes in population-weighted mean PM₂.₅ concentrations during the lockdowns of −11 to −15 μg/m³ across China, +1 to −2 μg/m³ across Europe, and 0 to −2 μg/m³ across North America. We explain these changes through a combination of meteorology and emission reductions, mostly due to transportation. This work demonstrates regional differences in the sensitivity of PM₂.₅ to emission sources.11 pagesen-USThis work was written as part of one of the author's official duties as an Employee of the United States Government and is therefore a work of the United States Government. In accordance with 17 U.S.C. 105, no copyright protection is available for such works under U.S. Law.Public Domain Mark 1.0http://creativecommons.org/publicdomain/mark/1.0/Text