It was predictable… The combination of very high temperatures and the absence of wind will lead to an episode of ozone pollution in Ile-de-France this weekend.
Airparif, the regional body responsible for monitoring air quality, predicts that the information threshold for this pollutant (i.e. an average concentration greater than 180 micrograms per m3 for more than an hour) will be exceeded for the day. of Friday.
Ozone is not directly emitted by polluting activities.
It is formed by the degradation of other pollutants (in particular nitrogen oxides, in particular emitted by combustion engines) under the effect of the sun's rays.
This "secondary" pollutant, which has the sad particularity of being the only one whose concentrations are increasing in Ile-de-France, can have health consequences and lead to respiratory or cardiac discomfort.
Motorists urged to lower their speed by 20 km/h
In the wake of Airparif's overrun forecasts, the regional health agency has therefore issued health recommendations, in particular for fragile or vulnerable people.
They are invited to favor short outings, outside the hours of maximum sunshine, and to avoid intense physical activity outdoors.
For its part, the Paris police headquarters reiterated, from the middle of the day on Thursday, the instructions to be followed during overtaking to reduce emissions linked to car traffic and (indirectly) ozone concentrations.
Motorists - invited to postpone unnecessary trips - will thus have to reduce their speed on the main roads by 20 km / h compared to the usual speeds.
The situation could deteriorate further
The use of teleworking or the use of public transport is also recommended.
Heavy goods vehicles of more than 3.5 tonnes, in transit, in Ile-de-France will have to bypass the heart of the agglomeration by taking the Francilienne.
No differentiated traffic on the program for the moment… But the police headquarters specifies that “additional measures” could be taken if the situation deteriorates.
Which should be the case.
Given the weather forecast and the continued very high temperatures, Airparif estimates that the air quality should continue to deteriorate after the first day of overshoot.
Even if the average levels of ozone pollution measured in the Paris region are almost systematically higher than those recommended by the WHO (World Health Organization), the information threshold had only been exceeded once in 2021. This Friday's pollution episode will be the second since the start of 2022.
