Air quality indexes: key considerations and roadmaps for best practices

Air quality indexes (AQIs) are widely used to communicate short-term air pollution concentrations and related health risks to the public. Conventional AQIs are typically formulated based on the concentration of the single air pollutant that most exceeds its regulatory standard (among all pollutants measured). Alternatively, health-based AQIs represent the combined health risks due to multiple air pollutants and are formulated from concentration–response functions derived from epidemiological evidence. This report examines public health approaches to improve AQIs, with a focus on roadmaps for best practices in developing, validating and communicating health-based AQIs. It first reviews the status of and differences between conventional and health-based AQIs. The Canadian Air Quality Health Index is presented as a model health-based approach, and the strengths and weaknesses of several novel indexes are discussed. Next, published studies supporting conventional and health-based AQIs across several tiers of evaluation are reviewed, focusing on evidence of public health benefits. The roles of public communication and global equity are also discussed. From this assessment, key considerations that serve as the basis for framing roadmaps for best practices moving forward are identified. In conclusion, health-based AQIs are noted to offer several advantages compared with conventional AQIs. There is a need to adopt locally-adapted, equity sensitive approaches that reflect diverse air pollution profiles, health susceptibilities and cultural contexts. Strengthening risk communication – through improved indexes and innovative strategies – plays a key role in supporting future efforts to protect public health.