 Our study shows that the reduction in pollution caused by the Covid-19 lockdown in Lombardy, Italy was complicated by weather variations, but using machine learning to build counterfactual scenarios allowed us to determine that the lockdown reduced background concentrations of PM 2.5 and NO2 by 3.84 gm3, 16% and 10.85 gm3, 33%, respectively, resulting in a saving of at least 11% of years of life lost and 19% of premature deaths attributable to Covid-19 in the region during the same period. Our analysis highlights the benefits of improving air quality and the need for an integrated policy response addressing the full diversity of emission sources. This article was authored by Francesco Granella, Lara Alleluia Race, Valentina Bacetti, and others.