COVID-19 lockdown only partially alleviates health impacts of air pollution in Northern Italy
The harsh lockdown measures that marked the response to the COVID-19 outbreak in the Italian region of Lombardy provides a unique natural experiment for assessing the sensitivity of local air pollution to emissions. However, evaluating the pollution benefits of the lockdown is complicated by confounding factors such as variations in weather. We use a machine learning algorithm that does not require identifying comparable but unaffected regions while addressing the effect of weather.
We show that the lockdown, albeit virtually halting most human activities, reduced background concentrations of PM2.5 by 3.84 µg/m3 (16%) and NO2 by 10.85 µg/m3 (33%). Improved air quality has saved at least 11% of the years of life lost and 19% of the premature deaths attributable to COVID-19 in the region. Although air pollution has significantly decreased, it has often remained above safety thresholds. The analysis highlights the diversity of air pollution sources and the need for an expansive policy response.