Distribution, Sources and Health Risk Assessment of Polybrominated Diphenyl Ethers in Surface Soils of Xi’an, a Rapidly Urbanizing City in Northwest China

Polybrominated diphenyl ethers (PBDEs), extensively used as brominated flame retardants, have become major environmental contaminants in developed regions due to their persistence, bioaccumulation and potential toxicity. With the rapid urbanization of Xi’an City in Northwest China, concerns regarding PBDEs accumulation in surface soils have increased. This study systematically investigated the distribution, sources and health risks of PBDEs based on 41 surface soil samples collected from four land-use types in Xi’an. The total concentration of eight PBDE congeners (∑8PBDE) ranged from 0.26 to 29.2 ng/g dw, with industrial soils exhibiting the highest median concentration (2.52 ng/g dw), followed by residential (2.13 ng/g dw), agricultural (1.19 ng/g dw) and water source protection areas (0.38 ng/g dw). BDE-209 was the predominant congener, accounting for 66.9% of the total, followed by BDE-183 (12.7%), BDE-153 (8.5%), BDE-47 (7.4%) and BDE-99 (3.8%). Principal component analysis indicated that PBDE contamination primarily originated from historical deca-BDE use and degradation of highly brominated congeners. Health risk assessments revealed children were more vulnerable than adults; however, all hazard indices and lifetime carcinogenic risks were substantially below the acceptable thresholds, suggesting minimal risk to the local population despite rapid urban expansion.