Histopathological Assessment of Rattus norvegicus Exposed to Treated and Untreated Wastewater: Implications for Environmental Health

Abstract

Despite increasing discharge of inadequately treated wastewater into aquatic environments, there remains limited experimental evidence linking real-world effluent exposure to multi-organ histopathological outcomes and the effectiveness of biological mitigation strategies. This is particularly concerning given the widespread presence of endocrine disrupting chemicals such as phthalate esters, which pose significant risks to environmental and public health. This study evaluated the histopathological effects of treated and untreated wastewater on multiple organs in Rattus norvegicus and assessed the potential protective role of seaweed extracts. Forty adult rats (male and female; n = 5 per group per sex) were randomly assigned to four treatment groups: untreated wastewater, treated wastewater, and seaweed extract at 1.0 g/L and 3.0 g/L. Exposure was administered orally for 30 days. Histological examination of the liver, kidney, heart, and lungs was performed using hematoxylin and eosin staining, and lesions were assessed using a semi-quantitative scoring system. Data were analyzed using one-way ANOVA with post hoc tests (p<0.05). Rat exposed to untreated wastewater exhibited significant histopathological alterations, including hepatocellular degeneration, renal tubular distortion, myocardial inflammation, pulmonary congestion, and neuronal disruption. In contrast, treated wastewater significantly reduced lesion severity across all organs (p < 0.05). Seaweed extract at 1.0 g/L demonstrated protective effects comparable to treated wastewater, whereas 3.0 g/L induced mild vascular and inflammatory changes in some tissues. Notably, sex-dependent differences were observed, particularly in renal and pulmonary responses. These findings demonstrate that wastewater treatment effectively mitigates organ toxicity associated with environmental contaminants, while seaweed extracts exhibit dose-dependent protective effects. This study provides important experimental evidence supporting improved wastewater management and highlights the potential of phytotherapeutic strategies in mitigating pollutant-induced toxicity.