Factors Influencing PFAS Accumulation in Root and Leafy Vegetables under Subsistence Farming in Shanghai, China

Diet, particularly the consumption of vegetables, has been suggested as one of the major human exposure pathways to per- and polyfluoroalkyl acid substances (PFAS). However, the extent of PFAS exposure among ordinary residents who consume vegetables grown under subsistence agriculture practices remains unclear, and PFAS sources in these vegetables remain unknown. In this study, 31 ionizable PFAS were analyzed in agricultural samples collected from open fields used for subsistence agriculture practices in Shanghai, China. Significant differences were observed in PFAS compositions and concentrations in leafy and root vegetables (p < 0.01) with higher total PFAS concentrations generally found in leafy vegetables (32-64 ng/g dw) than in root vegetables (23-29 ng/g dw). Comprehensive source verification analysis suggested that atmospheric deposition could be an important factor contributing to these differences. Uptake efficiency assessment further confirmed that foliar uptake was more effective for PFAS accumulation than root uptake, given a constant total exposure mass. PFAS surface uptake on vegetable leaves through epidermal permeation, as well as their translocation to the mesophyll through the apoplastic pathway, was revealed using mass spectrometry imaging. These findings enhance our understanding of PFAS contamination in vegetables and offer valuable guidance regarding the dietary safety of vegetables grown using subsistence agriculture practices.