Heavy traffic on the Quai de la Fosse in Nantes (illustration).

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F. Brenon / 20Minutes

  • Nitrogen dioxide pollution in the Nantes metropolitan area fell by more than 50% during confinement.

  • Fine particle emissions have also declined, but to a much lesser extent.

  • The highest concentrations of pollutants are found around major roads.

Road traffic is indeed the main enemy of air quality in the Nantes urban area.

This is what emerges from the latest data communicated by the Air Pays-de-la-Loire organization on the occasion of National Air Quality Day, this Wednesday.

A conclusion that comes at a time when the reduction in the number of car lanes in Nantes is causing debates as intense as the traffic jams in the morning.

Association responsible for regional pollution monitoring, Air Pays-de-la-Loire has carefully studied the consequences of containment (March 18-May 11) then deconfinement (May 11-June 22).

Automobile traffic in the metropolis then collapsed, up to -70% compared to the previous year.

Result: the concentrations of nitrogen dioxide, a pollutant emitted mainly by vehicles, dropped dramatically: -54% on average and even up to -65% in certain areas that are usually very busy, such as the western tip of the island of Nantes.

The drop in emissions is still significant (-20%) during the deconfinement phase, marked by a gradual resumption of activities.

Less spectacular for fine particles

"We can see that the impact of road traffic is significant," comments David Bréhon, director of Air Pays de la Loire.

"This clearly shows that urban mobility is a major subject for air pollution," adds Laurent Gérault, president of Air Pays-de-la-Loire and vice-president (centrist) of the regional council.

The decrease in concentrations is much smaller (approximately -10%) for fine particles (PM10), except in the vicinity of the busiest roads.

“The sources of particles are multiple, explains David Bréhon.

The circulation tap was cut off during the deconfinement, but other emitting activities continued, such as agriculture, industry or open burning.

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Pollution around major roads

Beyond this confinement period, the map of the average annual emissions of nitrogen dioxide, fine particles (PM10 and PM2.5) and ozone also shows that the highest concentrations are precisely around the large traffic axes of the agglomeration.

The first rows of which are the Quai de la Fosse, the Porte de Rennes, the Porte de Bouguenais, the Porte des Sorinières, the Bignon toll and the Atlantis sector.

“It's simple: less road traffic means less pollution.

And there are already alternative solutions ”, indicates the director of Air Pays de la Loire.

Nitrogen dioxide causes irritation and impaired respiratory function.

Fine particles increase the risk of respiratory and cardiovascular diseases.

The smallest of them (PM2.5) would be responsible for 48,000 premature deaths in France each year, including 2,530 in Pays-de-la-Loire, according to Public Health France.

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On a positive trend

Contrary to popular belief, the frequency of pollution peaks in Pays-de-la-Loire (ozone, nitrogen dioxide, sulfur dioxide and PM10) has been decreasing for nearly ten years.

The air quality is also considered "rather good" compared to other regions, indicates Air Pays-de-la-Loire.

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