Impact of mixed benzene site exposure on bioaccessibility in simulated lung fluids and health risk assessment

Benzene series (BTEX) are predominant volatile organic compounds (VOCs) in petroleum production and downstream industrial sites, primarily enter human lungs via inhalation, posing significant health risks. To address the critical limitation of existing risk assessments that focus solely on individual components, this study investigated benzene and ethylbenzene based on contamination characteristics of petroleum refineries in Northwest China. An innovative in vitro membrane oxygenator system was developed to simulate single and mixed exposure scenarios at three soil concentrations: low (5 mg/kg), medium (10 mg/kg), and high (20 mg/kg), respectively. Health risk indices including inhalation risk (Inh), hazard quotient (HQ), and lifetime cancer risk (LCR) were calculated using bioaccessibility–adjusted parameters to precisely compare risk variations across exposure modes. Results demonstrated significant synergistic effects in gas-liquid mass transfer kinetics under mixed exposure (P < 0.05), the simulated lung fluid bioaccessibility of benzene and ethylbenzene was also significantly higher (P < 0.05), likely due to their intermolecular cosolvency. Risk assessment results indicated that Inh, HQ, and LCR indices in mixed exposure were significantly higher (P < 0.05) than in single exposure, with a concentration–dependent contribution to health risks. At low concentrations, benzene's health risk indices increased by 185 %–284 %, while ethylbenzene's increased by approximately 63 %–68 %, indicating a synergistic effect in mixed exposure scenarios. This study offers a new methodological basis for health risk assessment of BTEX mixed exposure at petrochemical sites.