High Spatiotemporal Resolution Assessment of PM2.5 and NO2 Exposure and Respiratory Health Inequality in Thailand

Air pollution remains a critical environmental health challenge in Thailand, yet evidence linking high-resolution exposure to short-term respiratory health and inequality at the national scale remains limited. This study presents the first nationwide, high-resolution, daily assessment of PM 2.5 and NO 2 in Thailand jointly quantifies short-term respiratory impacts and spatial inequality from 2019 to 2023. Daily pollutant concentrations at 0.01° resolution were reconstructed using Light Gradient Boosting Machine model integrating ground observations, satellite products, meteorological reanalysis, atmospheric chemical fields, and socio-environmental indicators, achieving strong predictive performance (R 2 = 0.88 for PM 2.5 and 0.92 for NO 2 ; RMSE = 5.73 and 5.27 μg/m 3 , respectively). Distributed lag non-linear models were used to quantify short-term exposure–response relationships between air pollution and hospital admissions for asthma, chronic obstructive pulmonary disease (COPD), and all respiratory diseases. Pollutant-attributable fractions and inequality metrics were subsequently estimated. Long-term population exposure to PM 2.5 was dominant, with nearly all residents persistently exposed to concentrations exceeding WHO guideline levels, whereas NO 2 exposure was geographically constrained but concentrated in densely populated urban centers. Despite its limited spatial footprint, NO 2 exhibited stronger short-term associations with respiratory admissions and generated disproportionately high, population-amplified attributable burdens. During high-pollution episodes, NO 2 exposure accounted for an additional ~11% of daily asthma and COPD admissions in urban areas, with attributable fractions for all respiratory diseases reaching ~33%. These findings demonstrate that pollutants with contrasting exposure regimes impose distinct acute health and equity impacts, highlighting the need for pollutant-specific and regionally differentiated air quality management strategies in Thailand.