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Effect of air pollution reductions on mortality during the COVID-19 lockdown: A natural experiment study
Duration: 06/01/2021 - 05/31/2023

AIR-LOCK, a multi-country study, will evaluate whether changes in ambient nitrogen dioxide (NO2) and fine particulate matter (PM2.5) levels are associated with changes in mortality before, during, and after COVID-19 lockdowns and will disentangle the short-term effects of NO2 versus PM2.5 on mortality. The analysis will be conducted in four countries: China, Germany, Italy, and the United States.

Study Aims

To control the COVID-19 pandemic, unprecedented lockdown measures were implemented around the world, leading to large but temporary air pollution reductions. Both satellite and ground level measurements showed substantial decreases in NO2 concentrations during the lockdowns at the city or county level, whereas changes in PM2.5 concentrations were inconsistent, with reductions comparable to those of NO2, smaller reductions, or even increases. These disproportionate changes in ambient NO2 and PM2.5 pollution provide a rare opportunity for a natural experiment to address critical questions regarding the causal effects of NO2 and PM2.5 exposure on health.

We will first evaluate whether changes in mortality are associated with changes in ambient NO2 and PM2.5 levels, before, during, and after lockdowns (Aim 1). In addition, we will leverage this unprecedented natural experiment of disproportionate reductions in NO2 and PM2.5 pollution during the lockdowns to perform analyses to disentangle the short-term effects of NO2 versus PM2.5 on mortality (Aim 2), a challenge that has proven difficult in prior research due to the high correlation between these two pollutants.

AIR-LOCK will provide scientific evidence on the effects of the unprecedented interventions implemented to control the COVID-19 pandemic on air pollution and human health.