Ecological Risk Assessment of Pharmaceutical Waste in Health Facility Effluents Discharged into the Shomolu Central Canal (Lagos, Nigeria)

Abstract

Hospital wastewater in low- and middle-income countries (LMICs) represents a critical but often overlooked interface between pharmaceuticals, health systems and environmental public health. In this study, we evaluated pharmaceutical residue contamination from healthcare facilities. The effluents from six healthcare facilities were sampled; UNILAG Medical Centre, LADDILAK Hospital, DEJI Clinic, R. Jolad Hospital, Shomolu Health Care, Mainland Hospital, along with a reference canal (Shomolu Central Canal), three times in a month, randomly through continuous collection and storage for each individual facility, pooled as a single entity, and analyzed using UPLC-MS/MS for the quantification of nine pharmaceuticals (six antibiotics and three antimalarial drugs). The antibiotics were trimethoprim, doxycycline, ciprofloxacin, metronidazole, amoxicillin and sulfamethoxazole; and the antimalarial drugs were pyrimethamine, artemether and lumefantrine. The results were subjected to risk assessment, including risk quotient, pharmaceutical risk index, mass discharge estimation and statistical analysis (non-parametric comparisons and Spearman’s rank correlations), in order to identify the systemic drivers of environmental pharmaceutical discharge. The pharmaceutical loads observed at R. Jolad Hospital (5.01 ppm), UNILAG Medical Centre (0.318 ppm) and Mainland Hospital (0.318 ppm) were higher than the others and those measured in the canal (0.00160 ppm). The total quantified concentrations across all seven sites ranged from 0.00190 ppm to 5.01 ppm. The most contaminated sites were R. Jolad Hospital (2.86 ppm) for all analyzed antibiotics and antimalarial drugs (2.15 ppm), and UNILAG and Mainland Hospital (0.0152 ppm) for doxycycline. Doxycycline and trimethoprim were found to be the most pervasive compounds, with detection frequencies of 71.4% (5/7 sites) and 57.1% (4/7 sites), respectively, while localized treatments in the form of artemether (1.12 ppm) and lumefantrine (1.03 ppm) were restricted to a single site. Extreme ecological risks were observed for ciprofloxacin (RQ = 1,440) and pyrimethamine (RQ = 303). The significant differences in contamination loads (p < 0.01) and strong correlations between facility flow rate and discharge (ρ = 0.91) underscore the highly localized nature of daily mass loading, peaking dramatically at 2,505 g/day. These findings indicate the critical management implication of setting up targeted, decentralized on-site wastewater treatment facilities at high-volume healthcare centers, in order to mitigate toxic downstream impacts on receiving aquatic ecosystems.