Bioaccumulation and Elimination, and Risk Assessment of Diazepam in Carp (Cyprinus Carpio)

This study investigated the bioaccumulation and elimination dynamics of diazepam in various tissues of carp (Cyprinus carpio) exposed to environmentally relevant concentrations, along with assessing the potential human exposure risks associated with carp consumption. The residues of diazepam in carp skin muscle exceeded regulatory thresholds when the water concentration surpassed 100 ng/L. The tissue-specific accumulation levels followed the order: liver > kidney > gill > plasma > skin muscle. Steady-state bioconcentration factors (BCFss) were found to be 7.18 L/kg and 8.26 L/kg at exposure concentrations of 200 ng/L and 500 ng/L, respectively. The uptake constants (K₁) for the skin muscle were measured at 0.70 L/(kg·d) and 0.75 L/(kg·d), while the elimination constants (K₂) were 0.10 h⁻¹ and 0.085 h⁻¹, corresponding to half-lives of 6.37 h and 10.57 h, respectively. During the depuration phase, diazepam was predominantly detected compared to other main metabolites including nordazepam, oxazepam and temazepam. Risk assessments revealed that the counsumption of skin muscle posed acceptable risks, whereas the consumption of liver and kidney raised significant concerns. These findings provide a theoretical basis for pollution control, risk assessment, and the scientific management of diazepam in aquaculture.