Toxic layering and compound extremes: Per- and polyfluoroalkyl substances (PFAS) exposure in rural, environmental justice copper mining communities

Per- and polyfluoroalkyl substances (PFAS) are pervasive environmental pollutants with significant impacts on ecosystems and public health. This study aimed to characterize PFAS concentrations in an environmental justice community impacted by active/legacy copper mining, compounded by wildfires and flash floods. Additionally, the study explored the (re)mobilization of PFAS and co-occurrence with metal(loid)s following these events. Twenty-eight PFAS compounds in 35 residential and 8 control surface soil samples were analyzed via liquid chromatography-tandem mass spectrometry (LCMS/MS). The maximum total PFAS concentration observed in the residential samples was 96.40 μg kg⁻¹, compared to 1.69 μgkg⁻¹ in the control samples. Perfluorobutanoic acid (PFBA) had a maximum concentration of 61 μg kg⁻¹ in residential samples, while Perfluorohexane sulfonic acid (PFHxS) had the highest concentration in the control samples at 0.92 μg kg⁻¹. Long-chain PFAS were most dominant in this study. Perfluorooctane sulfonic acid (PFOS) (58 % of the samples), Perfluorooctanoic acid (PFOA) (35 %), and Perfluorohexane sulfonic acid (PFHxS) (72 %) exceeded the U.S. EPA Soil-to-Groundwater Risk-Based Screening Levels, highlighting the potential risk of contaminants migrating from soil to groundwater, which could ultimately impact groundwater quality. Co-occurrence analysis showed that increases in PFAS concentrations were positively associated with Zn (β = 1.25, p = 0.0034) and Ba (β = 1.23, p = 0.0284) but negatively associated with Pb (β = −0.83, p = 0.0115) and Co (β = −1.38, p = 0.04671). In general, a spatial distribution map indicated that greater PFAS concentrations were observed near potential sources i.e., active mines. This evidence combined with select metal co-occurrence highlights the potential role of mining activities on PFAS concentration.