Air quality: the World Health Organization (WHO) has established new guidelines 22nd September 2021 The WHO has recently published new guidelines on air quality, based on the latest scientific data available on the effect of atmospheric pollutants on health. They have set reference thresholds for the six main atmospheric pollutants which should not be exceeded so as to limit exposure for the population worldwide and to protect the health of all. Ineris has performed some preliminary analyses of the impact of these new guidelines on the exposure of the French population to atmospheric pollution. The guidelines recommend guide values for air quality in order to protect the health of populations by reducing the levels of the main atmospheric pollutants. These new guidelines constitute an update of the values previously established in 2005. In particular, revised guide values have been announced for three of the atmospheric pollutants that are still causing the most problems in France - particles, ozone and nitrogen dioxide. Each guide value is chosen in reference to a synthesis of the information from studies looking at the health effects of the different pollutants concerned, all over the world. There is a wide consensus as to these guide values since they were produced by a team of internationally reputed experts and take into account the prevailing conditions in the different regions of the world. They provide reliable recommendations aimed at the political leaders responsible for decision-making about air quality management. Thus these values will help to progress the target exposure criteria (percentages of the population and territory concerned by threshold overrun) for atmospheric pollution. Our initial estimations show that the new values proposed by the WHO significantly increase the proportion of the French and European population exposed to overruns of the new thresholds. Key points In general, the new guidelines are more ambitious than the 2005 values in that they either lower the reference thresholds or introduce new metrics (see the table below, an extract from the WHO press release). Of the most remarkable points, we can note: The lowering of the threshold for annual mean concentrations of fine particles PM2.5 to 5 µg/m3 (the threshold was at 10 µg/m3 in the 2005 document); The introduction of the notion of seasonal peaks for ozone, based on 6-month averages of the maximum daily concentrations; The lowering of the threshold for annual mean concentrations of nitrogen dioxide (NO2) to 10 µg/m3 (instead of 40 µg/m3 in 2005); The introduction of a new statistic for NO2, with a threshold value relative to the daily mean. What are the impacts for the exposure of the French population? Following the WHO announcements, Ineris carried out preliminary analyses of the impact of these new guidelines on the exposure of the French population to atmospheric pollution. This assessment was based on the “air quality” map library that illustrates the changes in the concentrations of the main atmospheric pollutants over the last 20 years. With estimated pollution levels for the year 2019: The whole of the national territory was exposed to overrun of the new threshold values for the annual mean concentrations of fine particles (PM2.5); More than ¾ of the French population were exposed to overrun of the new threshold for the annual mean concentrations of nitrogen dioxide. All these new data must be analysed and integrated into the work seeking to set future strategies for managing air quality in France and across the world. These new threshold values were highly anticipated by the international community active within the United Nations Convention on Long-range Transboundary Air Pollution (CLRTAP). This body is currently working on revising the Gothenburg Protocol, with the aim of setting emission reduction strategies and national emissions ceilings for atmospheric pollutants for 2030 in order to limit the levels of pollutants in ambient air. Ineris is also heavily involved in the scientific work and negotiations for this convention, as part of its mission to support the French Ministry for Ecological Transition. Ineris, a key player in the field of air quality The Institute is well-known in France and internationally for its activities in the field of air quality. It is one of the three members of the Laboratoire central de surveillance de la qualité de l’air (LCSQA, Central Laboratory for Air Quality Monitoring), alongside the Institut Mines-Télécom Douai and the Laboratoire national d’essai (LNE, national testing laboratory). As such, it participates in the technical coordination of the national air quality monitoring scheme. Ineris’s research into the sources of particles and its work on modelling and forecasting air quality also contribute to a better understanding of the phenomena of pollution and to assessing the efficacy of management policies. In particular, the Institute developed the CHIMERE chemistry-transport model in partnership with the CNRS. The model is used in the national air quality forecasting system, Prev’air, developed in partnership with Météo France and the CNRS, for short-term forecasts and monitoring of pollution episodes in France. CHIMERE has also made it possible to conduct simulations that help to define the objectives and actions of the National Emissions Reduction Plan for Atmospheric Pollutants (PREPA).