Comparative stress response assessment of PFOS and its alternatives, F-53B and OBS, in wheat: An insight of toxic mechanisms and relative magnitudes

Emerging alternatives to perfluorooctane sulfonate (PFOS), including 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) and p-perfluorous nonenoxybenzene sulfonate (OBS), have been widely detected in the real environment as PFOS restriction. However, the toxicity in plants and the underlying mechanism of F-53B and OBS remain scarce, especially compared to PFOS. PFOS and their emerging alternatives pose significant potential risks to food, especially for crops, safety and human health with the great convenience of high chemical stability. Germination toxicity, oxidative stress biomarkers, and metabolomics were used to compare the relative magnitudes of toxicity of PFOS and its alternatives in wheat (Triticum aestivum L.). PFOS, F-53B, and OBS inhibited wheat germination compared to the control group, with germination inhibition rates of 45.6%, 53.5%, and 64.3% at 400 μM PFOS, F-53B, and OBS exposure, respectively. Moreover, oxidative stress biomarker changes were observed in PFOS, F-53B, and OBS, with OBS being more pronounced. The chlorophyll concentrations in wheat shoots increased, and the anthocyanin concentration decreased along with the increased exposure concentration. Superoxide dismutase (SOD) activity increased in wheat root but decreased in the shoot. Peroxidase (POD) activity and malondialdehyde (MDA) concentration increased, whereas catalase (CAT) activity decreased. Regarding metabolomics, PFOS, F-53B, and OBS exposure (10 μM) significantly altered 85, 133, and 134 metabolites, respectively. According to KEGG enrichment analysis, F-53B specifically affects lipid metabolism, whereas OBS causes an imbalance in amino acid and carbohydrate metabolism. These findings suggested that PFOS, F-53B, and OBS have distinct toxic mechanisms. Thus, our results indicated that the relative size of the toxicity in wheat is as follows: OBS > F-53B > PFOS, and this finding provides a new reference basis for the phytotoxicity assessment of F-53B and OBS.