Regional differences in health exposure risk of indoor benzene series and safety threshold determination for the Chinese population

Indoor benzene series (BTEX) pollution from building and decoration materials poses growing health risks during China's urbanization. Nationwide multi-scenario exposure assessments remain limited, and the risk-based thresholds for benzene and ethylbenzene are still undefined. This multi-region study collected 1396 indoor air samples to assess BTEX pollution and exposure risks in Chinese dwellings. Combining health probabilistic risk and DALY (disability-adjusted life year) calculations with Monte Carlo simulations, we determined safety concentration thresholds of 0.023 mg/m³ (benzene) and 0.162 mg/m³ (ethylbenzene) based on acceptable carcinogenic risk thresholds (1 ×10⁻⁶). BTEX concentrations across followed the order: high exposure places > indoor residential > office areas > public places, with spatial analysis revealing a distinct north-high-south-low geographical gradient. Health effect assessment indicated that total non-carcinogenic risks of BTEX exceeded thresholds by 3.5-fold, indoor residential carcinogenic risks for children were 2.3 times higher than for adults, and risks in indoor residential and high-exposure places significantly exceeded acceptable levels. Disease burden analysis showed that indoor benzene exposure contributed to a leukemia burden rate of 55.9 per 100,000 population, equivalent to an annual lifespan loss of 238.65 s per capita (4.816 h over a lifetime). The disease burden for children, the elderly, and adult women is relatively significant. This study offered critical scientific support for revising indoor air quality standards and formulating prioritized intervention strategies for high-risk zones and vulnerable populations.