Illustration of a peak in air pollution.

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V. Wartner / 20 Minutes

  • The new air index, introduced in each region, now takes PM 2.5 into account, these very fine particles that are particularly harmful to health.

  • This change of scale is likely to be noticed in Hauts-de-France, very concerned by pollution with very fine particles.

  • However, the regulations on pollution peaks remain the same.

It was pollution that went unnoticed.

From this Monday, the new air index, introduced in each region, now takes into account PM 2.5, these particles invisible to the naked eye (less than 2.5 micrometers), which are particularly harmful to the environment. health.

This change of scale is likely to be noticed in Hauts-de-France, but paradoxically, it will not change anything concerning pollution alert measures.

Particles less reported so far

Until then, the Atmo site, which measures regional pollution levels on a daily basis, was based on four pollutants: sulfur dioxide, nitrogen dioxide, ozone and fine particles PM 10, the diameter of which is less than 10 micrometers (µm).

From now on, PM 2.5 (less than 2.5 µm) will also be taken into account in the daily calculations.

These very fine particles are more harmful because they can slip further into the body.

Hence the recommendations of the World Health Organization (WHO) not to exceed three days per year, above the threshold of 25 µg in the atmosphere.

However, in the Lille metropolitan area, the threshold is exceeded about fifty days per year without this data being taken into account.

This will now be the case, automatically causing the indices to plunge downwards.

Hauts-de-France particularly concerned

"It should therefore come as no surprise to see the air quality indices deteriorate while the level of pollution will be the same", specifies Atmo.

Indeed, the Hauts-de-France region, and especially the metropolis of Lille, are particularly affected by the presence of PM 2.5.

In a 2015 study, Atmo found that these particles were more related to heating (41%) than PM10 (27%).

"However, the weather is that homes are heated more than in other regions," notes Atmo.

Added to this is the fact that many buildings continue to suffer from insulation problems.

Reducing these particles is therefore a puzzle.

Still no regulatory threshold

But measuring pollution does not mean "taking action".

Thus, unlike PM 10, there is still no regulatory threshold for these PM2.5.

This contradiction means that, despite poor air quality due to PM 2.5, there will not be more pollution peaks triggered by the prefecture.

Our file on air pollution

The air index has adapted to European standards, not French legislation.

For individuals, this new air index will therefore not be synonymous with more traffic restrictions.

Until further notice.

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