## 3 Endocrine-Disrupting Compounds EDCs
### Perfluorinated Compound Degradation  
Perfluorinated compounds are a relatively recently investigated group of micropollutants responsible for endocrine disruption of living organisms. They were synthesized for the first time in the 1950s and have found numerous applications in industry, including for firefighting agents, personal care products, and herbicides. The many industrial uses of perfluoroalkyl substances (PFAS), combined with their extremely long half-life in the human body and extreme persistence in the environment, have led to widespread and chronic exposure to them. The adverse endocrine effects of perfluorinated compounds still require much research, but it is known that they depend on the concentration, chain length, and type of functional group alongside the age, sex, and species of exposed organisms [64]. The first work on the application of ionizing radiation to perfluorinated surfactants concerned the use of an electron beam from an accelerator with an energy of 6 MeV to determine the rate constants of perfluorooctaoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) reactions with \({}^{\bullet}\)OH radicals and a hydrated electron [65]. The investigations were carried out in a nanosecond pulse radiolysis system with spectrophotometric detection using aqueous solutions of ammonium perfluorooctanoate and tetraethylammonium perfluorooctanesulfonate. The obtained constants had values for \({}^{\bullet}\)OH radicals: \(-\)3.0 \(\times\) 10\({}^{7}\) M\({}^{-1}\)s\({}^{-1}\) for \(\mathrm{e_{ad}}^{-}\), 1.3-5.1 \(\times\) 10\({}^{7}\) M\({}^{-1}\)s\({}^{-1}\) for PFOA, and -3.0 \(\times\) 10\({}^{7}\) M\({}^{-1}\)s\({}^{-1}\) and 7.3 \(\times\) 10\({}^{7}\), respectively, for PFOS. The obtained values indicate that the reactions of PFOA and PFOS with \({}^{\bullet}\)OH or \(\mathrm{e_{aq}}^{-}\) radicals are 2-3 orders of magnitude lower than the reactions of many other organic molecules, which are also micropollutants. On the other hand, similar values of the reaction constants with both \({}^{\bullet}\)OH and \(\mathrm{e_{aq}}^{-}\) indicate that both  
Figure 3: The possible degradation pathway of MDHB during the combined irradiation and biological treatment process. The brackets represent the biodegradation products. The dashed line represents presumable further transformation [62]. PFOS and PFOA can potentially react with all major products of water radiolysis, and the application of the radiation method requires careful optimization. In recent years, several papers have been published on the use of gamma ionizing radiation [6; 66; 67] and the electron beam [6; 68; 69; 70] to degrade PFOA and PFOS in aqueous solutions. When gamma radiation was used to degrade PFOA with an initial concentration of 20 mg dm\({}^{-3}\), the authors showed that both a hydrogen atom and an electron are necessary for the process. On the other hand, as the concentration of hydroxyl radicals decreased, a lower degree of defluorination was observed, which means that the C-F bond cannot be effectively broken in the absence of \({}^{\bullet}\)OH radicals. The first use of the electron beam for the decomposition of PFOA concerned a solution prepared in 0.1 mM phosphate buffer with an initial concentration of 0.5 mg dm\({}^{-3}\)[69]. The addition of 20 mg dm\({}^{-3}\) NO\({}_{3}\)\({}^{-}\) was shown to significantly increase the defluorination efficiency from 34.6% to 93.3% at a dose of 10 kGy. This is attributed to the formation of highly reducing NO\({}_{3}\)\({}^{\bullet-}\) radicals. A high 95% degradation efficiency for PFOA and an 85% efficiency for PFOS was obtained for an EB irradiated solution at pH 13 [70]. The lower degradation efficiency of PFOS as compared to PFOA is due to the more difficult oxidation of sulfonate to sulfate. The decomposition of PFOA occurred with the highest efficiency in strongly alkaline solutions; in addition, the effect of the dose rate on the decomposition efficiency of PFOA was observed for the first time.