Immunotoxicity of F 53B, an alternative to PFOS, on zebrafish (Danio rerio) at different early life stages

As an alternative to perfluorooctane sulfonate (PFOS), 6:2 chlorinated polyfluorinated ether sulfonate (F53B) has emerged in the Chinese market in recent years and has been frequently detected in the aquatic environment, but its ecological risk assessment is limited. In this study, zebrafish embryos and larvae were separately exposed to F53B, and their 96-h LC50 values were estimated to be 15.1 mg/L and 2.4 mg/L, respectively, suggesting that embryos were more resistant to F53B than larvae. The bioconcentration factor in larvae was basically higher than that of embryos, and the body growth of larvae was significantly affected by F53B rather than embryos, indicating that F53B may cause more severe toxicity to larvae. In addition to the excessive production of ROS and NO, the expression of many immune-related genes was increased in both embryos and larvae, but the number of dysregulated genes in larvae was more than that in embryos. Finally, the results of Point of Departure (PoD) indicated that the immunotoxicity of F53B was more sensitive to larvae than embryos at the molecular level. Our findings revealed the ecological risk of F53B by exploring the adverse effects of immunoregulation at different early life stages of zebrafish and indicated that the zebrafish larvae were more sensitive than embryos.