This is a rare event that occurred last week in Brittany. Something that doesn’t happen often but that no one really noticed. Except us, maybe. Because this rare thing is invisible, imperceptible. Symbolized by two small blue dots on a map of Brittany, this event occurred on November 21. That day, the map distributed to its 5,900 subscribers by Air Breizh showed air quality described as “good” in Vannes and Central Brittany.
Normal, you might think. Well no. In the region, the “standard” is rather the green sticker. And unlike its ancestor which was stuck on the least polluting cars, this one designates “average” air quality, according to the French barometer. Since January 1, 2021 and the alignment of the French scale with the European system, this color has become the standard in Brittany. Explanations.
In 2022, the Rennes metropolis breathed “average” air for 261 days, “degraded” air for 66 days and “bad” air for 37 days. And the good one, then? According to Air Breizh’s report, only the day of October 18 was classified in this category. The reason ? “No doubt it had rained quite a bit that day. The rain tends to leach the atmosphere and clean it,” explains Gaël Lefeuvre, president of the Air Breizh association, which carries out the daily readings. Lorient does barely better with two days of “good” air quality. Wind is also a good element in the fight to disperse pollutants. But despite its rainy and windy reputation, Brittany remains confronted with the “ambient noise” of its pollutants.
Fine particles when it’s cold
In the region, the overwhelming majority of pollution is generated by road traffic, wood heating and agriculture, but their temporality depends on weather conditions. To put it simply, we will say that when it is cold, it is the fine particles that lodge in our bronchi, especially when the climate is dry. And when it’s hot, it’s more ozone that poisons us.
The trend is rather downward for fine particles PM10 and PM2.5, due to the modernization of vehicles and the abandonment of open fireplaces. “Ozone concentrations tend to increase, in particular due to global warming,” specifies the director of Air Breizh. A trend which is therefore unlikely to improve in the coming years.