## 3 Results and Discussion
### Ecotoxicity Data  
The original ribesartan compound was proven to be relatively non-toxic through the \(D\). _magnu_, _A. fischeri_, and _R. subcapiatta_ screening tests, with EC\({}_{50}>\) 100 mg/L. The current research shows that the chlorination of ribesartan involves more complex DBPs. Our previous work found different DBPs derived from ribesartan chlorination, inducing significantly elevated toxicity in specific model organisms [25]. The ecotoxicological tests presented dynamic and variable toxicity of ribesartan and its byproducts (Figure 5). The lowest toxicity level occurred at an around \(-\)32% (indicating stimulation) concentration of DBP7 in the algal test, while the highest toxicity was at 84% of the mixture in the bacteria test.  
Among the tested organisms, _A. fischeri_ was the most sensitive to the DBPs, followed by _R. subcapiatta_ and, finally, \(D\). _magnu_, showing significant species-specific toxicity. According to a previous study, the sensitivity to DBP effects increases with decreasing trophic levels [33]. In contrast to species-specific toxicity differences, only DBP10 showed the same range of toxicity in all the tested organisms, but no unique physicochemical characteristics have been associated with contributing to the observed effects.  
The observed sensitivity and, consequently, toxicity changes can be attributed to the new smaller molecules present following the cleavage of functional groups that renders them more or less reactive against non-target organisms [33; 34]. This also aligns with previous studies that stated the introduction of a chlorine atom into a molecule or the formation of a chlorinated compound led to an increase in acute toxicity [35].  
To further evaluate and interpret the toxicological relationships among the tested DBPs, the obtained results were compared to those reported in the study by [PERSON] et al. [16] on \(D\). _magna_. As mentioned previously, compounds DBP9, DBP15, and DBP16 were found to be very similar to DBP2, DBP1, and DBP5 [16], respectively. Although the toxicity of the new DBPs was lower than that of the DBPs previously reported [16], differences in the structures of the newly identified compounds compared to those previously reported could have led to different toxic effects. Even slight structural differences can significantly alter the physicochemical and biological properties of a compound, including its toxicity. Therefore, a comprehensive analysis of the ecotoxicity of all the identified DBPs, including the newly identified ones, is necessary to fully understand the potential health risks of ribesartan and its byproducts in the aquatic environment.  
Figure 5: Toxicity results after exposure to irbesartan and its oxidation byproducts.  
In addition, this study found that 64% of DBPs exhibited the stimulation (hormesis) of _R. subcapitata_. From an environmental perspective, it is crucial to evaluate the observed hormetic effect of disinfection byproducts (DBPs) on algal populations in water bodies that receive sewage. This evaluation should consider the occurrence of DBPs and algal blooms and assess the true nature of the contribution of DBPs to phytoplankton blooms [36]. It should be noted that the co-existence of many other DBPs in the environment, their high toxicity, and the potential interactions between them [37] suggest that chlorine products could pose high environmental risks.