## 3 Endocrine-Disrupting Compounds EDCs
### Antibiotic Degradation  
Among the numerous categories of antibiotics, sulfonamides are the most commonly used substances worldwide in both developed and developing countries. Some researchers do not classify sulfonamides as antibiotics. They consider that, as fully synthetic pharmaceuticals, they are not antibiotics in the strict sense of the word, despite their antibacterial activity. Sulfonamides such as sulfathiazole (STZ), sulfamethazine (SMZ), and sulfamethoxazole (SMX) are commonly detected in surface waters [110; 111] up to \(\upmu\)g dm\({}^{-3}\) levels [112; 113] because they are polar and highly soluble in water [114; 115]. It has been shown that gamma radiation can be effective in removing sulfamethoxazole (SMX) residues from aqueous solutions [29]. The degradation process was mainly caused by the reaction with the \({}^{\bullet}\)OH radical. The COD and TOC values obtained indicated complete mineralization. The observed initial increase in phytotoxicity was predominately due to H\({}_{2}\)O\({}_{2}\) formed during irradiation. An increase in the BOD\({}_{5}\) value after irradiation was also observed, which indicated the conversion of the non-biodegradable compound to biologically degraded substances [30]. This is in agreement with results previously obtained [22] where the application of pre-irradiation with a dose of 2 kGy for aqueous solutions containing SMX, limomycin (LMC),  
Figure 8: Proposed DCF degradation pathway by EB [103]. and tetracycline (TCN) with an initial concentration of 17 mg dm\({}^{-3}\) improved the biological degradation of these compounds. As expected, the initial concentration of SMX has a significant effect on its removal efficiency [31]. The efficiency of the process depends on the initial concentration; as the concentration increases, the efficiency decreases. The anions present in natural waters also affect the efficiency of the process, with a greater effect observed for NO\({}_{3}\)\({}^{-}\) than NO\({}_{2}\)\({}^{-}\). Furthermore, it was observed that after a dose of 400 Gy, the removal efficiency of 5 mg dm\({}^{-3}\) SMX is independent of the presence of inorganic anions. The effect of the presence of Cr (VI) in the form of K\({}_{2}\)Cr\({}_{2}\)O\({}_{7}\) with an initial concentration of 0.01 mmol dm\({}^{-3}\) on the removal efficiency of 5 mg L\({}^{-1}\) SMX from aqueous solutions was also determined. The observed effect was in opposition to that of anion addition; the radiolytic removal efficiency of both SMX and Cr (VI) in the mixture was higher than that of single impurities. Other authors [116] showed that the presence of 0.1 g dm\({}^{-3}\) Fe\({}_{3}\)O\({}_{4}\) increased SMX degradation for different initial concentrations ranging from 5 to 30 mg dm\({}^{-3}\) compared to the control group that did not contain Fe\({}_{3}\)O\({}_{4}\). Furthermore, it was shown that SMX could be degraded over a wide range of pH values (3.01-10.96), and the degradation efficiency was over 98%. SMX mineralization in the presence of Fe\({}_{3}\)O\({}_{4}\) increased by about 200%. Similar results were obtained for the degradation of aqueous sulfadiazine SD solution under gamma irradiation [117]. Although the addition of Fe ions can significantly increase SD degradation, the TOC removal in this case increased slightly, which may suggest that SD mineralization does not occur as easily as SMX mineralization. It was also found that pre-irradiation can improve biodegradability; a 14.5% increase in biodegradability was observed after a dose of 1 kGy [33]. The effect of the matrix on the EB beam decomposition efficiency was also observed, which decreased to 75% in surface water for STZ compared to 90% efficiency in distilled water after a dose of 0.5 kGy was delivered to the system [118]. Degradation mechanism for SMX using EB is presented in Figure 9.  
Initially, the S-C bond of SMX was attacked by free radicals, leading to products 1 and 2.