PFAS at a closed fluorochemical manufacturing facility in China: multi-media contamination and human health risks

Per- and polyfluoroalkyl substances (PFAS) production sites remain long-term sources of environmental contamination after closure, yet depth-resolved and multi-media contamination profiles within these legacy sites remain poorly understood. This study investigated a decommissioned PFAS production facility in Hubei Province, China, by analyzing 40 PFAS in surface soil, deep soil, groundwater, and surface-deposited dust using a modified U.S. EPA Method 1633A. Human health risks were assessed in accordance with Chinese standard HJ 25.3 and the latest parameters in U.S. EPA's Regional Screening Level (RSL) database. Results identified the facility interior as the primary source area, with ΣPFAS in on-site surface soil (412-11967 μg/kg) significantly exceeding off-site levels (10.8-110 μg/kg). Although the maximum perfluorooctanesulfonic acid (PFOS) concentration decreased from 66830 μg/kg in 2022 to 3067 μg/kg in 2025, historical PFOS residues continue to exert persistent environmental impacts. In addition, localized accumulation of perfluorobutanesulfonic acid (PFBS) and a high proportion of perfluorohexanesulfonic acid (PFHxS) indicate that the production transition reshaped PFAS profiles. Deep soil and groundwater exhibited pronounced spatial and vertical heterogeneity. PFHxS, PFBS and 6:2 fluorotelomer sulfonate (6:2 FTS) were predominant in groundwater, identifying them as important contributors to current aqueous contamination, which is consistent with their relatively high mobility in the soil-groundwater system. Notably, ΣPFAS in surface-deposited dust reached 0.29-2.50 g/kg, identifying surface-deposited dust and equipment residues as critical long-term contaminant reservoirs. Risk assessments showed that while risks from perfluorobutanoic acid (PFBA) and perfluorohexanoic acid (PFHxA) were negligible and PFBS presented only low-level risks in specific groundwater samples, perfluorooctanoic acid (PFOA), PFHxS, and PFOS posed non-negligible risks in multiple samples. PFOS remained the dominant risk driver with the widest distribution and highest risk levels. These findings underscore that site closure does not equate to risk elimination. Future site management strategies must prioritize targeted remediation and migration control based on health risk assessments, with specific attention to the secondary pollution potential of dust and equipment residues.