"The Covid-19 pandemic has cleared the city streets. But who foresaw that it would dramatically clean the urban air?
One unexpected consequence of the global response to the coronavirus pandemic has been the extraordinary reduction in urban air pollution in cities where the majority of the population have been required to stay home. This level of clean city air—clean enough to breathe freely without fear of eventually damaging one’s health and that of one’s children, is unprecedented in the modern era. Urban residents have marveled at the clarity of distant mountains rarely seen or imagined. Cities that used to be shrouded in a grey-brown blanket of smog, now seem newly minted against a background of sparkling blue sky."