Development of the national Air Quality Health Index based on short-term effects of ambient air pollution on mortality in Thailand

The Air Quality Health Index (AQHI) has long been introduced as an environmental health risk communication tool. Based on an epidemiological approach, it considers the combined effects of many air pollutants. However, comprehensive AQHI development for Thailand remains. This study aimed to develop the national AQHI in Thailand and determine whether sex- and age-specific AQHIs should be developed. The AQHI was constructed by examining the mortality risk associated with short-term exposure to multiple air pollutants using a time-stratified case-crossover design with the conditional Poisson regression model. This analysis utilized data from 31 provinces in Thailand from 2017 to 2020. The mortality risk associated with five criteria air pollutants—particulate matter with either 10 μm (PM₁₀) or 2.5 μm (PM_2.5) in aerodynamic diameter, as well as nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ground-level ozone (O₃), and carbon monoxide (CO)—was calculated to construct the national AQHI and scaled it to a range from 0 to 10. The AQHIs were developed separately for age and sex, and the mortality risk associated with this established AQHI was explored and compared with that associated with the Air Quality Index (AQI). We found that the total AQHI and sex- and age-specific AQHIs were highly correlated with a similar association with mortality. The effects of AQHI on mortality were slightly more potent than AQI's, but their model fit statistics were comparable. In conclusion, developing specific AQHIs is unnecessary because their distributions and effects are similar to total AQHIs. The AQHI seems to be the better tool for communicating health risks related to air pollution, as the mortality risk associated with AQHI was more pronounced than that associated with AQI.