Summary

Air pollution is a major hazard to human health and a leading cause of illness and death. In 2021, the World Health Organisation (WHO) published revised global air quality guidelines to offer quantitative, health-based recommendations for air quality management (WHO 2021). To support this update, WHO published a series of review papers evaluating the best available evidence on the effects of air pollutants on human health (Chen and Hoek 2020; Huangfu and Atkinson 2020; Lee et al. 2020; Orellano et al. 2020, Orellano et al. 2021; Zheng et al. 2021). This factsheet provides additional technical detail on how the systematic reviews informed the development of WHO’s revised global air quality guidelines.