Long-term exposure to NO2 and O3 and all-cause and respiratory mortality: A systematic review and meta-analysis

WHO has published several volumes of Global Air Quality Guidelines to provide guidance on the health risks associated with exposure to outdoor air pollution. As new scientific evidence is generated, air quality guidelines need to be periodically revised and, where necessary, updated. The aims of the study were 1) to summarise the available evidence on the effect of long-term exposure to ozone (O3) and nitrogen dioxide (NO2) on mortality; 2) and to assess concentration response functions (CRF), their shape and the minimum level of exposures measured in studies to support WHO’s update of the global air quality guidelines.