Perfluorooctanoic acid at environmentally relevant concentrations interfere with nitrogen fixation and amino acid synthesis in soil-soybean system.

Perfluorooctanoic acid (PFOA) contamination in soils is of concern, stemming from its detrimental impact on ecosystem functions and human health at high levels. However, considering its actual pollution levels in cultivated soil, it is necessary to comprehensively evaluate its biological effects under environmental concentrations. Results on the effect of PFOA at levels of 10 and 20 μg/kg on the entire life cycle of soybeans (Glycine max L.) showed increased accumulation in the order of root > leaf > stem > pod > bean, ranging from 0.5 to 155.4 μg/kg. PFOA accumulated in beans (0.5-1.1 μg/kg) posed a potential health risk to the human body with an estimated daily intake (EDI) value at 0.008-0.18 ng/(kg body weight (bw)·day). Moreover, PFOA at such levels disrupted amino acid metabolism, especially decreasing the contents of l-4-hydroxyproline (Hyp), γ-aminobutyric acid (GABA) and l-tryptophan, thereby lowering the nutritional quality of soybeans. It also changed the relative abundance of soil microorganisms, reduced the production of flavonoids, and negatively impacted the biological nitrogen fixation of soybean. The findings unequivocally validate that even at the environmental concentrations, PFOA could reach a level hazardous to food safety and soil quality. This underscores the paramount importance of implementing stringent risk mitigation measures.