Mortality and economic burden of PM2.5 and NO2 in Thailand using satellite remote sensing and Random Forest algorithms

Abstract

Air pollution remains a leading environmental health problem in Thailand, where rapid urbanization, biomass burning, and industrial activity contribute to high concentrations of fine particulate matter (PM<inf>2.5</inf>) and nitrogen dioxide (NO<inf>2</inf>). However, most existing studies rely upon data from fixed-site monitoring stations, leaving large areas underrepresented. This study aimed to develop satellite-based Random Forest (RF) models to estimate daily concentrations of PM<inf>2.5</inf> and NO<inf>2</inf> across Thailand from 2018 to 2022 using Aerosol Optical Depth (AOD) data from Terra and Aqua satellites, and NO<inf>2</inf> from TROPOspheric Monitoring Instrument (TROPOMI) aboard the Sentinel-5 Precursor satellite. These estimated concentrations were then linked to health and economic impacts using concentration-response functions and the Value of Statistical Life (VSL). The RF models demonstrated high performance. For PM<inf>2.5</inf>, the model achieved R² of 0.94 and RMSE of 7.40 µg m^-3 in training, and R² of 0.71 with RMSE of 15.09 µg m^-3 in testing. For NO<inf>2</inf>, R² values were 0.94 and 0.73, with RMSE of 2.21 and 4.41 ppb, respectively. Nationwide mean concentrations during the study period were 29.51 ± 2.82 µg m^-3 for PM<inf>2.5</inf> and 4.61 ± 0.81 ppb for NO<inf>2</inf>, with pronounced regional and seasonal contrasts. Specifically, PM<inf>2.5</inf> peaked in northern provinces during the dry season, while NO<inf>2</inf> levels were concentrated in Bangkok and industrial regions. Modeled concentrations were higher than ground-based averages as the model captures unmonitored high-pollution areas, particularly in the north. Long-term exposure to PM<inf>2.5</inf> and NO<inf>2</inf> was associated with 20,487 deaths (95 % CI: 12,833–28,079) and 15,394 deaths (95 % CI: 10,281–20,487), respectively, corresponding to economic losses of 2313 million THB (95 % CI: 1449–3171) and 1738 million THB (95 % CI: 1161–2313) annually, respectively. This study provides a reliable tool for nationwide air quality monitoring and health impact assessment and supports development of sustainable environmental and public health strategies.