Abstract
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 (<18%). The PM(2.5)-related risk was amplified in high-altitude residents (>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.