air pollution remains a Covid-19 threat multiplier, as well a health hazard that will far outlast the pandemic.As governments ordered temporary confinement measures to battle multiple virus waves, several studies have charted a marked increase in air quality in the US, China, and Europe.In Spain, for example, levels of atmospheric nitrous oxide (NO2) -- associated with a host of lung conditions -- plummeted 62% during the spring lockdown period.France and Italy saw falls of 52 and 48%, respectively, according to the European Environment Agency.Since air pollution kills roughly seven million worldwide people each year, such falls are bound to have prevented deaths.Paola Crippa, assistant professor at Notre Dame's Department of Civil and.