Occurrence and ecotoxicological risk assessment of pharmaceutical residues in water resources of Obuasi metropolis, Ghana

Abstract

Pharmaceutical pollution in water is a global-scale environmental and public health concern owing to its persistent, biologically active, and poorly regulated status. In this study, the occurrence and ecotoxicological risk of tramadol, ibuprofen, acetaminophen, diazepam diclofenac, aspirin and caffeine in wastewater samples from hospitals, waste stabilisation ponds, and a river in the Obuasi metropolis of Ghana were evaluated. Samples were collected monthly over three consecutive months. Following solid phase extraction (SPE), high-performance liquid chromatography (HPLC) with UV detection was used to separate, identify, and quantify these seven essential pharmaceuticals. The removal efficiency by waste stabilisation ponds was also assessed. All the targeted pharmaceuticals were detected in all hospital effluents, waste stabilisation ponds, and surface water samples, indicating their occurrence in the aquatic systems. Acetaminophen was the most prevalent compound (maximum 23.0 µg/L), while diazepam showed the lowest maximum concentration (2.0 µg/L). The removal efficiency of the waste stabilisation pond relating to total pharmaceutical load ranged between 61.5 and 82.2%. Risk Quotients (RQ) ranged from 0.0 to 0.191 (surface water), 0.0002–0.209 (waste stabilisation pond water), and 0.0–0.295 (hospital wastewater), indicating predominantly low to medium potential risk to aquatic organisms. The highest RQ values were observed for ibuprofen (0.191–0.295 across compartments for Daphnia exposure). These results highlight the need for continued monitoring and improved wastewater management practices to reduce pharmaceutical inputs into receiving waters in the region.