The International Global Atmospheric Chemistry project comments on the revised WHO air quality guidelines

Abstract In 2021, the World Health Organization (WHO) air quality guidelines were revised for six key air pollutants. The new guideline levels for PM 2.5 and O 3 may be unattainable for many countries due to natural sources and background levels. Reductions in NO 2 may increase O 3 due to atmospheric chemistry. Regional-specific scientific expertise is necessary to guide local air quality management towards more appropriate WHO interim targets and controls on modifiable factors especially considering atmospheric chemistry. The IGAC project aims to build such scientific leadership and foster collaboration in air quality and atmospheric chemistry research through regional working groups, topical activities, and regular meetings including the biennial IGAC science conference.