Antibiotic Residues in Incinerator Ash from Medical Facilities in Nakuru Town, Kenya: Implications for Environmental Safety

Abstract

The purpose of this study was to analyse incinerator ashes from two medical facilities in Nakuru Town, Kenya, namely Lakey Hospital and Rifty Hospital, to determine the concentrations of Metronidazole, Benzyl penicillin, and Ceftriaxone before the ash was released into the environment. Pharmaceutical wastes constitute approximately 15 per cent of global medical waste and pose risks to environmental and public health. The study adopted a longitudinal research design, with ash samples collected weekly for three weeks from incinerators at both hospitals and fly ash from the chimney of Rifty Hospital. Composite samples were prepared by collecting ash from different points using a stainless-steel spade. Solid Phase Extraction was employed to pre-treat the samples, which were subsequently analysed by High-Performance Liquid Chromatography using a UV detector. Differences in antibiotic concentrations according to sampling location and antibiotic type were evaluated using two-way Analysis of Variance. Benzyl penicillin concentrations in Lakey and Rifty hospital ashes were 24,111.51 µg/ml and 1,281.08 µg/ml, respectively, while Ceftriaxone concentrations were 192,944.27 µg/ml and 5,049.70 µg/ml, respectively. Metronidazole was absent in Lakey Hospital ash but recorded at 265.33 µg/ml in Rifty Hospital ash. Rifty Hospital fly ash contained Benzyl penicillin (588.9 µg/ml) and Ceftriaxone (273.5 µg/ml). Detected concentrations substantially exceeded the respective CLSI breakpoints, indicating potential environmental contamination and antimicrobial resistance risks. The study recommends regular inspection of incinerators, disposal of final ash in sanitary landfills, and strengthened regulatory monitoring before environmental release.