Environmental Monitoring and Chemical Risk Assessment of Effluent Discharges from Pharmaceutical Manufacturing Facilities in Ogun State Industrial Clusters

Pharmaceutical manufacturing effluents represent a significant source of biologically active chemical contamination in receiving water bodies. In Ogun State, which hosts the largest concentration of pharmaceutical manufacturers in Nigeria in its Agbara and Sango-Ota industrial estates, systematic chemical monitoring of effluent quality and downstream environmental impact remains limited. This study monitored the chemical composition of effluent discharges from eight pharmaceutical manufacturing facilities in Ogun State and assessed the ecological and human health chemical risk of receiving water bodies. Effluent and downstream surface water samples were collected monthly over six months. Chemical oxygen demand, biochemical oxygen demand, heavy metals, pH, and targeted pharmaceutical compounds were determined using standard methods and HPLC-MS/MS. Ecological risk was assessed using risk quotient methodology, with predicted no-effect concentrations derived from published aquatic toxicity data. All eight facilities exceeded NESREA limits for COD and at least one pharmaceutical compound. Downstream surface water showed detectable concentrations of amoxicillin, ciprofloxacin, and metformin at multiple collection points. Ecological risk quotients above 1.0 were calculated for ciprofloxacin at three monitoring points, indicating unacceptable risk to aquatic organisms. Human health risk from recreational exposure was classified as low but not negligible. These findings demonstrate that pharmaceutical effluent discharges in Ogun State industrial clusters pose a measurable environmental chemical risk requiring regulatory intervention and facility-level treatment improvement. Keywords: pharmaceutical effluent, environmental monitoring, risk assessment, Ogun State, HPLC-MS/MS.