The various information and alert thresholds for triggering action during pollution peaks
To limit the health effects of pollution peaks, French regulations have set action thresholds based on measurements of air concentrations of various pollutants such as particulate matter, nitrogen dioxide, ozone and sulphur dioxide. These benchmarks are updated over periods of time ranging from a few hours to a day, depending on the pollutant.
There are two threshold levels: an information and recommendation threshold, and an alert threshold. Depending on the threshold reached, appropriate measures are taken at the local level, which may include informing vulnerable populations, reducing vehicle speeds or requiring industrial companies to reduce their emissions.
At the same time, the French ATMO index provides the population with daily updates on the air quality situation. This is based on the European Air Quality Index recently amended by the European Environment Agency.
ANSES was asked for its opinion on amending the thresholds for triggering prefectural procedures in the event of ambient air pollution episodes, and on how they tie in with the ATMO index levels.
Develop thresholds in line with WHO's recently updated ambient air quality guidelines
After analysing the most recent scientific literature, ANSES found health risks at pollutant concentration levels below the thresholds currently in force. The Agency therefore recommends lowering the information and alert thresholds to ensure better protection of population health. These thresholds should be close to the new short-term action guideline values recently published by WHO, which reflect the latest epidemiological knowledge available.
Consistency between regulatory thresholds and the ATMO index
The European Air Quality Index and the French ATMO index should also be revised in line with the new values published by WHO, to ensure that these indicators used to inform populations reflect the state of knowledge in terms of health risks.
Lastly, ANSES reiterates that the greatest share of the burden on population health is due to the average level of ambient air pollution rather than to pollution peaks. It therefore highlights the essential role of public policies in combating the harmful consequences of air pollution over the long term.