PM2.5 and its chemical components interact with hypoxia to increase the risk of hospitalization for peripheral arterial disease

This study investigated the combined effects of fine particulate matter (PM 2.5 ) exposure and ambient oxygen (O 2 ) availability on peripheral artery disease (PAD) hospitalizations in Gansu Province, China, from 2018 to 2022 (N = 38,514). A time-series case-crossover design with conditional logistic regression assessed short-term exposure to daily PM 2.5 and its major chemical components (black carbon [BC], organic carbon [OC], sulfate [SO 4 2− ], nitrate [NO 3 − ], ammonium [NH 4 + ], and chloride [Cl − ]). Atmospheric O 2 levels were estimated based on altitude, temperature, and humidity. Short-term exposure to PM 2.5 was associated with an increased risk of PAD hospitalization, notably at lag 1 (odds ratio [OR] = 1.003; 95% confidence interval [CI]: 1.002–1.004). Carbonaceous pollutants exhibited delayed effects, with peak associations at lag 6 for BC (OR = 1.069; 95% CI: 1.035–1.105) and OC (OR = 1.028; 95% CI: 1.011–1.050), per 1 μg/m 3 increase. Secondary inorganic aerosols showed acute effects at lag 1: Cl − (OR = 1.107; 95% CI: 1.063–1.150), NH 4 + (OR = 1.040; 95% CI: 1.022–1.060), SO 4 2− (OR = 1.025; 95% CI: 1.015–1.036), and NO 3 − (OR = 1.030; 95% CI: 1.018–1.042), per 1 μg/m 3 increase. Nonlinear exposure–response curves revealed a stronger PAD risk under lower O 2 conditions (1500 m), older adults (>60 years), females, emergency admissions, and during the cold season. These findings suggest that ambient PM 2.5 and lower O 2 levels interact synergistically to elevate PAD hospitalization risk, emphasizing the urgent need for region-specific air quality controls and targeted health protection strategies.