Air quality monitoring associations, including Air Pays de la Loire, calculate and publish every day an air quality index called the ATMO index.

This indicator evolves in January 2021 to be calculated at the level of each municipality or at the inter-municipal level, over the entire national territory based on the air concentrations of five regulatory pollutants: sulfur dioxide (SO2 ), nitrogen dioxide (NO2 ), ozone (O3 ) and particles less than 10 micrometers in diameter (PM10).

Since 2021, particles with a diameter of less than 2.5 micrometers (PM2.5) are included in this calculation. The index then corresponds to the most degraded of the sub-indexes calculated for each of these 5 pollutants.

Thanks to the ATMO index, it is possible to monitor the status of air quality and its forecast for the next day and adapt activities accordingly.

Below is a video from the Ministry of Ecological Transition on the ATMO Index.

Patients suffering from respiratory diseases, just as their doctors, can subscribe by e-mail to this ATMO index on the Air Pays de la Loire website.

Find information on the new ATMO index on

Indoor Environment Medical Advisor,
CHU de Nantes Pneumology Department