PRESENCE OF ILLICIT DRUG METABOLITES IN THE INFLUENT OF A WASTEWATER TREATMENT PLANT IN ELDORET, KENYA

Abstract

The increased occurrence of illicit and medical drug residues in urban wastewater raises new environmental and public health problems. Conventional monitoring methods are frequently expensive, invasive, and have limited population coverage, rendering them unsuitable for routine community surveillance. This study used wastewater-based epidemiology (WBE) to investigate the prevalence and temporal trends of selected drug metabolites in influent wastewater from a treatment facility in Eldoret, Kenya. From February to May 2025, weekly composite influent samples were collected and analysed using solid-phase extraction and liquid chromatography-tandem mass spectrometry (LC-MS/MS). Six metabolites were consistently identified: amphetamines, methylhexanamine, 19-norandrosterone, 3′-hydroxy-stanozolol, erythropoietin (EPO), and cocaine derivatives. Amphetamine concentrations peaked in February (50.0 ± 0.10 ng/L) and gradually fell, while anabolic steroid metabolites exhibited a moderate but consistent fall. Methylhexanamine levels remained rather steady throughout the study period, but cocaine metabolites showed up occasionally, indicating sporadic community usage. The discovery of EPO (0.003 ng/L) revealed WBE's great analytical sensitivity in detecting low-level biomarkers in complicated wastewater mixtures. Overall, the findings emphasise WBE as a viable, non-invasive, and cost-effective method for monitoring community-level drug exposure and producing real-time local information on emergent substance-use trends. This study presents the first baseline dataset of drug-related metabolites in Kenyan wastewater, paving the way for WBE's future integration into national environmental and public health surveillance regimes.