Due to their chemical structure, PFAS are very stable in the environment and are resistant to biodegradation, photo-oxidation, direct photolysis, and hydrolysis. Individual PFAS have been found to negatively affect autotrophic and heterotrophic food webs, but more data is needed to understand the toxicity of PFAS mixtures outside of PFOS and PFOA. Whether these other compounds are toxic, contribute additive or synergistic toxicity, or do not significantly contribute to toxicity remains largely unknown. SERDP and ESTCP efforts to close knowledge gaps in ecotoxicity and ecological risk will aid in the development of appropriate site-specific risk assessments and help in decision-making related to mitigation of exposures, including future environmental cleanup. Current projects are addressing impacts of PFAS to several species, including but not limited to avian, mammalian, and reptilian species.

Additional data is needed to improve the understanding of mixture ecotoxicity to wildlife, particularly given that AFFF-impacted sites have been shown to contain many PFAS, not just PFOA and PFOS.