Constructing an AQHI as a health risk communication tool for Bangkok, Thailand

• First to develop the AQHI in Bangkok, Thailand. • Significant association of cardiovascular, respiratory diseases and ambient air pollutants of PM 2.5 , PM 10 , O 3 , SO 2 . • AQHI captured high and very high risk levels more than currently used AQI. • An effective tool for communicating air pollution-related health risks in the urban city. In this study, we established an air quality health index (AQHI) based on the associations between multiple air pollutants and respiratory and cardiovascular outpatient department (OPD) visits to communicate the health risks from air pollution in Bangkok, Thailand. The associations between various air pollutants, namely, suspended particulate matter (PM) with an aerodynamic diameter smaller than 2.5 µm and 10 µm (PM 2.5 and PM 10 , respectively), sulphur dioxide (SO 2 ), and ozone (O 3 ) and the number of OPD visits for respiratory and cardiovascular diseases in Bangkok from 2016 to 2019 were assessed using generalised additive models with a Poisson link function. Significant associations were established between most cases of cardiovascular and respiratory diseases and these pollutants with a lag time of 0–7 days. The total excess risk was calculated to construct the AQHI, which was then adjusted to an arbitrary scale and banded into four groups based on the calculated score, where 1–3, 4–6, 7–10, and 10+ represented low risk, moderate risk, high risk, and very high risk, respectively. We found that the AQHI captured both high and very high risk levels during the day for most stations. The constructed AQHI also recorded a greater number of high and very high risk days than the currently used AQI but fewer than the WHO-based AQI. Our findings suggest that the AQHI can capture the combined effects of multiple air pollutants, which makes it an effective tool for communicating air pollution-related health risks.