Pharmaceutical Contaminants in Lagos Water Bodies as Cross-Species Toxicological Hazards

Introduction: Pharmaceutical contamination of urban water bodies poses cross-species toxicological risks to humans, aquatic fauna, and terrestrial animals — a concern central to the One Health framework. In Lagos, Nigeria, inadequate wastewater infrastructure, self-medication, and improper drug disposal drive the accumulation of pharmaceuticals in surface and groundwater systems.

Methods: Water samples were collected from 11 sites across Lagos Mainland, spanning residential and industrial locations. Ten pharmaceutical compounds were quantified by HPLC-MS/MS. Ecological risk was assessed using risk quotients (RQs) based on measured concentrations and predicted no-effect concentrations. Human exposure was evaluated across three routes, oral ingestion, fish consumption, and dermal contact during flooding, using established bioconcentration factors and an acceptable daily intake set at 1% of the lowest therapeutic dose.

Results: Pharmaceuticals were detected at all sampling sites, with artesunate, diclofenac, and amoxicillin showing the highest mean concentrations. All ten compounds exceeded PNEC thresholds for aquatic organisms, with diclofenac posing the greatest ecological risk (RQ > 29,000). Oral ingestion produced hazard quotients above 1 for seven compounds, while fish consumption emerged as the most critical human exposure pathway, particularly for chloroquine, diclofenac, and artesunate. Cumulative Hazard Indices exceeded 1 for eight of ten compounds, with diclofenac and chloroquine recording the highest overall risk.

Conclusion: These findings indicate that pharmaceutical contamination of Lagos water bodies poses a measurable cross-species toxicological hazard, with clear relevance to One Health. Findings underscore the urgent need for pharmaceutical surveillance, disposal stewardship, and strengthened ecotoxicological monitoring capacity across West African urban settings.