• According to Atmo, an observatory responsible for monitoring air quality in Auvergne-Rhône-Alpes, ozone pollution has gradually increased for ten years.

  • Amplified by heatwave episodes, it in turn contributes to increasing global warming.

  • “It seems important to act on road traffic and economic activity if we want to reduce it,” say observers.

The figures, recorded during the year 2020, are a bit like the tree that hides the forest.

Faced with a strict episode of confinement for two months, the Auvergne Rhône-Alpes region was able to breathe.

All the indicators used to assess air pollution are down compared to previous years.

Including ozone.

Today, this "sneaky and insidious" pollutant nevertheless worries observers because it has been the only one for ten years to remain on an upward curve, except for the year 2020. The concentrations of fine particles, very present during peaks of pollution, have steadily fallen, but not ozone.

The situation is the same everywhere: in town, in the countryside or in high altitude areas.

And the development prospects concerning it in the coming years "are unfavorable".

"Short-term actions are only effective if you act very strongly"

"The hotter the summers, the more there will be a significant concentration of ozone," predicts Didier Chapuis, territorial director of Atmo, an observatory responsible for measuring air quality in the region.

Ozone is the result of chemical transformations under the action of solar rays.

But it also contributes to increasing global warming by 10%.

A vicious circle.

"If we want to reduce the concentration of ozone in the atmosphere, we must first succeed in reducing the precursor pollutants (nitrogen oxide and volatile organic compounds)", warns Yannick Mathieu, deputy regional director at Dreal. .

What solutions then?

"It seems important to act on road traffic, economic activity, the use of solvents in everyday products or the use of wood heaters," said Didier Chapuis, cautious about short-term actions.

"They are only effective if you act very strongly," he replies.

The limits of alternating traffic

Containment has proven to be beneficial but it is obvious that it cannot be retained as a track for the long term.

Alternate circulation?

She hasn't really proven herself.

"It would take a decrease in nitrogen dioxide of the order of at least 80%, and therefore a drastic reduction in road traffic to be effective," says Didier Chapuis.

Which seems difficult to apply.

"If we only work on alternating circulation, it is not efficient," says Marie-Blanche Personnaz, director of Atmo Aura.

The ideal is to anticipate, to act before the heat waves and on a large scale.

Teleworking is indeed an interesting lever.

"We all dream of widespread teleworking during pollution peaks," concludes Yannick Matthieu.

A regional ozone plan, sponsored by the State, is also in the process of being finalized.

It must propose information and awareness actions but also the establishment of operational levers in the territories.

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