Environmental occurrence and hazard of selected antibiotics in soils from two Nigerian urban landfills

This study investigated the occurrence and potential ecotoxicological risks of five antibiotics (sulfamethazine, trimethoprim, ciprofloxacin, ofloxacin and sulfadoxine) in soils from two urban landfills (Ajakanga and Olusosun) in Nigeria. These landfills were selected based on their substantial waste volumes, diverse waste composition and significant population pressure. Solid–liquid extraction was followed by extract clean-up and instrumental analysis using solid phase extraction and high performance liquid chromatography, respectively. Overall recoveries ranged from 73% to 121% with %RSD values of ≤ 17% at two different fortification levels. Method limits of quantification ranged from 0.21 ng/g (sulfamethazine) to 2.48 ng/g (ciprofloxacin). Only trimethoprim was detected, with significantly higher concentrations in Ajakanga soils (up to 359.9 ± 11.1 ng/g) than in Olusosun soils (up to 59.3 ± 0.9 ng/g) across two sampling campaigns. Trimethoprim in soils from Ajakanga and Olusosun landfills posed medium and low ecotoxicological risks, respectively, to aquatic organisms, Eisenia fetida (earthworm), seedling height and root elongation of cucumber and rice. To the best of our knowledge, this study provides the first report on the occurrence and ecotoxicological risk of antibiotics in Nigerian landfill soils, emphasising the critical need for robust pharmaceutical waste management protocols to mitigate environmental and public health hazards.