Comparison of the combined toxicity of PFOA and emerging alternatives: A comprehensive evaluation of oxidative damage, apoptosis and immunotoxicity in embryonic and adult zebrafish.

Perfluorohexanoic acid (PFHxA) and perfluorobutanoic acid (PFBA) are widely used substitutes to perfluorooctanoic acid (PFOA). Whether these substitutes are less toxic than PFOA remains unclear owing to differences in the experimental methods, test organisms, and other experimental conditions in previous studies. The present study selected 0.5 and 5 μg L as the test concentrations and simultaneously compared the combined toxicity of the substitutes and PFOA in terms of oxidative damage, neurotoxicity, apoptosis, and immunotoxicity in two developmental stages of zebrafish (adult and embryos) under the same test conditions. The results indicated that in both adult and embryonic zebrafish, PFHxA, PFBA, and PFOA disrupt redox homeostasis, stimulate cell proliferation, and lead to carcinogenesis. The mechanisms by which PFHxA and PFOA induce neurotoxicity and immunotoxicity were similar. Molecular docking analysis showed that the substitutes and PFOA stably attached to proteins and changed their structure and function. The obtained integrated biomarker response index values indicated that the toxicity of PFHxA, PFBA, and PFOA in zebrafish increased with increasing concentrations; PFHxA was more toxic than PFOA. The present study clarified the ecotoxicity of PFHxA and PFBA in zebrafish and simultaneously compared the differences in toxicity between the substitutes and PFOA to zebrafish, providing a robust scientific basis for the clarification and selection of safe substitutes to PFOA.