Environmentally relevant PFOS exposures reveal low phytotoxicity yet high bioaccumulation in model crops

Perfluorooctane sulfonate (PFOS), a persistent "forever chemical," is increasingly detected in agricultural soils, irrigation water, and edible plant tissues, raising concerns for food safety and ecological health. However, the phytotoxic consequences of PFOS at environmentally relevant concentrations remain poorly defined. In this study, we investigated the uptake, distribution, and biological responses of soybean (Glycine max) and lettuce (Lactuca sativa) under controlled PFOS exposures, using arsenic (As) as a benchmark toxicant. PFOS accumulated efficiently in roots and translocated to shoots, with tissue concentrations exceeding those of As under comparable conditions. Despite this bioaccumulation, PFOS induced only limited acute effects on root growth, chlorophyll content, and antioxidant enzyme activities, contrasting sharply with the pronounced oxidative stress and growth inhibition caused by As. Transcriptomic analysis further revealed that PFOS elicited modest and selective changes in pathways related to secondary metabolism, cell wall modification, and hormone signaling, whereas As broadly disrupted photosynthesis, redox balance, and growth-related gene networks. These findings frame PFOS as a "silent accumulator"-a pollutant embodying a unique stress strategy that sustains high tissue burdens with minimal acute systemic disruption, distinct from As's overt metabolic toxicity. It suggests that at environmentally relevant concentrations, PFOS is unlikely to induce acute systemic phytotoxicity; however, its persistence, bioaccumulation, and subtle molecular effects underscore potential long-term risks to crop quality and food safety. Future research should focus on chronic low-dose exposures and combined pollutant scenarios to better capture PFOS's ecological and agricultural impacts.