PHARMACEUTICAL WASTE IN FRESHWATER SYSTEMS: RE-ENTRY CYCLES, ECOTOXICOLOGICAL TIPPING POINTS, AND PUBLIC HEALTH RISKS

The widespread use of pharmaceuticals has introduced a persistent and largely unregulated source of contamination in freshwater systems, raising critical concerns about ecological integrity and public health. The central problem lies in the re-entry cycle, in which antidepressants and hormones are inadequately removed during wastewater treatment and subsequently reintroduced into aquatic environments, where they accumulate and potentially return to humans through water and food consumption. This study aimed to analyze how the inefficiency of wastewater treatment systems contributes to bioaccumulation processes and to identify critical thresholds at which pharmaceutical residues pose ecological and public health risks. An integrative literature review was conducted based on a structured search strategy in major scientific databases, followed by systematic screening and evidence synthesis. The analysis revealed that pharmaceutical residues are globally distributed in freshwater systems at concentrations ranging from ng/L to µg/L, with documented effects including endocrine disruption, behavioral alterations, and population-level impacts in aquatic organisms. The findings also highlighted the occurrence of mixture effects and the inability of conventional treatment systems to effectively remove complex bioactive compounds. The discussion emphasized the existence of non-linear toxicity patterns and the emergence of ecotoxicological tipping points, beyond which ecosystem stability may be compromised. The results further indicated significant gaps in long-term monitoring and regulatory frameworks. In conclusion, pharmaceutical contamination represents a systemic challenge requiring the integration of advanced treatment technologies, environmental pharmacovigilance, and a One Health approach to mitigate long-term ecological and public health risks.