While the air becomes more and more breathable in the Arve Valley & elsewhere, no one can really enjoy it, as France has been under lockdown since 17 March 2020.
It is official now. Since the beginning of the containment, some indicators of air quality have gone green.
In China and Italy, aerial images have already shown this phenomenon over areas that are usually very polluted. The most obvious is the reduction in nitrogen dioxide (NO2).
On the Annecy ring road, the concentration decreased from 30 micrograms per m³ to 5 in only six days. In Passy, the ratio is 22 to 2.
Figures which are not surprising, knowing that in Haute-Savoie, 68% of nitrogen dioxide (Nox) emissions are directly generated by the transport sector.
The Mont-Blanc massif had been severely affected by global warming in the past years, with a glacier being on the brink of collapse in September 2019.
Now that people are confined to their homes and public transport has decreased, a significant drop in the air pollutants was expected.
Traffic on the Mont-Blanc tunnel still strong, show the webcams at the entrance to the tunnel
Individual transport alone accounts for 80% emissions, whereas heavy-goods vehicles account for only 20%.
"The French often find it difficult to accept that it is their own cars that pollute the most," said Antoine Martin, an engineer for the Association for the Respect of the Mont-Blanc Site (ARSMB).
The Mont-Blanc tunnel remains open, but the traffic has dropped by 15% since the start of containment.
On the Route Blanche in Chamonix, an impressive drop in nitrogen dioxide from 15 to 6 was registered.
More pollutants around households
If the drop in nitrogen dioxide was very clear, the other pollutants did not drop that much.
Moreover, the Atmo air quality indices for the past week were far from the "very good" that one would have expected with averages rather around 40/100.
While the pollutants have dropped on the highways, the situation is different at the bottom of the valley, near the houses.
Individual wood heating is the main culprit for this. "People spend more time at home and therefore have to heat up more," assumes Didier Chapuis, territorial director of Atmo Auvergne-Rhône-Alpes.
This is the average drop in nitrogen dioxide emissions in the Auvergne Rhône-Alpes region (similar development in France) since the start of containment on March 17, linked to the drop in individual road traffic.
A decline which should further increase this week.