Effects of COVID-19 lockdowns on fine particulate matter concentrations

Lockdowns 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 (PM_2.5) are of particular interest, as PM_2.5 is the leading environmental risk factor for mortality globally. We map global PM_2.5 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 PM_2.5 concentrations during lockdown periods in 2020 compared to the same periods in 2018 to 2019. We find changes in population-weighted mean PM_2.5 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 PM_2.5 to emission sources.