The coronavirus emergency called for the establishment of the red zones, the closure of schools, shops and businesses, the limitations of travel. But, at least, after almost a month of restrictions, in northern Italy there was a significant and also rather rapid drop in smog levels, despite the fact that last February was the hottest ever (with 2.76 ° C more and 80% less rainfall than the average).

This was reported by an analysis by Coldiretti on Isac Cnr data, on the side effects of the epidemic on air pollution levels. The images of the Sentinel 5 satellite of the European Copernicus program, published on Twitter by Santiago Gassò, a researcher at the University of Washington and NASA, show the reduction of nitrogen dioxide levels, a pollution marker.

Comparing images from single days is suggestive at best. For ex, day selection is important there is more activity during weekdays than in weekends. Here are displayed two weekend days one-month apart. The decrease is clear. Yet this needs to be with independent obs networks. https://t.co/LqK2b3Vn9H pic.twitter.com/rwpFjSJDJT

– Santiago Gassó (@SanGasso) March 12, 2020

It happened, on the other hand, also in China, as NASA satellite images and the European Space Agency had confirmed: to prevent the spread of the virus, production in many factories had been stopped and transport had been limited. And from 10 to 25 February, traces of nitrogen dioxide, which is emitted by motor vehicles, power plants and industrial plants and can cause breathing problems such as cough, asthma and breathing difficulties, were only barely visible. So, Fei Liu, a NASA researcher, said it was "first time that I see such a dramatic drop over such a large area for a specific event. " The same thing happened in Northern Italy, when the economy of the whole territory suffered a sudden stop.

The drop in pollution is the only positive aspect that can be traced in this difficult phase: people with respiratory problems run greater risks of falling ill with Covid-19.

But «in the fight against smog, however, we cannot continue to chase emergencies, but we must intervene structurally rethinking the development of cities and favoring the diffusion of public and private green spaces, also experimenting with new innovative solutions such as vertical gardens and vegetable gardens which favor the most effective varieties ", observes Coldiretti. «We need to encourage the spread of parks and gardens in cities capable of capturing dust and reducing the level of pollution. An adult plant is capable of capturing from 100 to 250 grams of fine dust from the air and one hectare of plants eliminates about 20 kilos of dust and smog in a year, but in Italy each inhabitant has only 32.8 square meters in the city of urban greenery. The situation worsens for the metropolises with values ​​ranging from 6.3 in Genoa to 16.5 in Rome to 18.1 in Milan up to 22.6 in Turin ".