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 PM2.5 and NO2 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 (R2 = 0.88 for PM2.5 and 0.92 for NO2; RMSE = 5.73 and 5.27 μg/m3, 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 PM2.5 was dominant, with nearly all residents persistently exposed to concentrations exceeding WHO guideline levels, whereas NO2 exposure was geographically constrained but concentrated in densely populated urban centers. Despite its limited spatial footprint, NO2 exhibited stronger short-term associations with respiratory admissions and generated disproportionately high, population-amplified attributable burdens. During high-pollution episodes, NO2 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.