Addressing the High-Altitude Blind Spot in Environmental Health Risk Assessment:A "Hidden Burden" Framework for the Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is perceived as having pristine air quality due to low ambient PM2.5, yet this obscures a critical blind spot: high-altitude populations rely on indoor solid fuel combustion, generating disproportionate black carbon exposure. We hypothesized that household solid fuel burden increases with elevation, producing a hidden total air pollution burden exceeding national averages in Tibet and Qinghai. Using GBD 2017 provincial estimates, elevation data, and Third Pole black carbon measurements across 31 Chinese provinces, we applied covariate-adjusted robust regression, chain mediation, spatial autocorrelation, and Monte Carlo uncertainty propagation. Ambient PM2.5 PAF decreased with elevation (Spearman r = −0.404, *p* = 0.024), while household PAF increased strongly (r = 0.745, *p* < 0.001). Elevation remained an independent predictor after confounder control (standardized beta = 0.438, *p* < 0.001). Total PAF in Tibet (7.97%) and Qinghai (7.98%) exceeded the national average (6.80%). Chain mediation using COPD DALY rate confirmed the pathway (indirect effect = +0.226, Bootstrap 95% CI: 0.015−0.546), with 49.5% mediated through household solid fuel. Two distinct underestimation pathways operate: exposure underestimation (current ambient-PM2.5-centric policies ignore indoor solid fuel contributions that dominate at high altitude) and susceptibility underestimation (GBD exposure-response functions, calibrated on lowland populations, may underestimate per-unit-exposure risk for hypoxic high-altitude populations).