Many urban dwellers have gazed in awe at their newly clean cities over the last few months. But three – Copenhagen, Oakland and Mexico City – are leading the way in making such transformations permanent. How?

https://www.theguardian.com/environment/2020/jun/07/blue-sky-thinking-how-cities-can-keep-air-clean-after-coronavirus?fbclid=IwAR1u7ZR_RUGuhMw-x-vT_wbyW74stGFAWaOmXdYxJXIt-FoYamJb72mtGoY