COVID-19 lockdowns cause global air pollution declines

TLDR

The COVID‑19 lockdowns caused an unprecedented reduction in global economic and transport activity. The study tests whether COVID‑19 lockdowns reduced tropospheric and ground‑level air pollution using satellite data and over 10,000 air‑quality stations. The authors used satellite observations, a network of >10,000 air‑quality stations, and mobility data from Google and Apple to assess the impact of lockdown‑induced transport reductions on air pollution. Lockdowns caused a 60 % drop in population‑weighted NO₂ and a 31 % drop in PM₂.₅, a modest 4 % rise in ozone, and satellite data revealed smaller reductions, underscoring spatial variability; mobility data linked vehicle declines to NO₂ reductions, indicating that reducing routine emissions could lower health risks. Data and visualizations are available at https://nina.earthengine.app/view/lockdown-pollution.

Abstract

The lockdown response to coronavirus disease 2019 (COVID-19) has caused an unprecedented reduction in global economic and transport activity. We test the hypothesis that this has reduced tropospheric and ground-level air pollution concentrations, using satellite data and a network of >10,000 air quality stations. After accounting for the effects of meteorological variability, we find declines in the population-weighted concentration of ground-level nitrogen dioxide (NO 2 : 60% with 95% CI 48 to 72%), and fine particulate matter (PM 2.5 : 31%; 95% CI: 17 to 45%), with marginal increases in ozone (O 3 : 4%; 95% CI: −2 to 10%) in 34 countries during lockdown dates up until 15 May. Except for ozone, satellite measurements of the troposphere indicate much smaller reductions, highlighting the spatial variability of pollutant anomalies attributable to complex NO x chemistry and long-distance transport of fine particulate matter with a diameter less than 2.5 µm (PM 2.5 ). By leveraging Google and Apple mobility data, we find empirical evidence for a link between global vehicle transportation declines and the reduction of ambient NO 2 exposure. While the state of global lockdown is not sustainable, these findings allude to the potential for mitigating public health risk by reducing “business as usual” air pollutant emissions from economic activities. Explore trends here: https://nina.earthengine.app/view/lockdown-pollution .