Antimicrobial Residues and Heavy Metals in Aquaculture Farms Within Nairobi County, Kenya

Inappropriate use of antibiotics in aquaculture, livestock, and agriculture contributes significantly in the development of antimicrobial resistance. This study assessed antimicrobial residues and heavy metals in fish, water, and sediments within Nairobi County, Kenya. Eighteen (18) fish farms were visited and water (17), fish (11), and sediment (9) samples were collected. The samples were analyzed using liquid chromatography coupled with tandem double mass spectrometry (LC‐MS/MS) and ICP‐MS for antimicrobial residues and heavy metals, respectively. Thirteen (13) antimicrobial residues: trimethoprim, sulfadiazine, sulfamethoxazole, sulfamethazine, tetracycline, doxycycline, oxytetracycline, erythromycin, azithromycin, ampicillin, penicillin G, amoxicillin, and cloxacillin tested were detected in all three sample types at concentrations below the recommended maximum residue levels. The overall percentage of tetracylines, sulfonamides, trimethoprim, beta‐lactams, and macrolides antibiotic residues classes positive in water, fish, and sediment samples were (94.12%, 100%, 100%), (94.12%, 100%, 100%), (100%, 100%, 100%), (35.29%, 9.09%, 33.33%), and (94.12%, 0%, 11.11%), respectively. The mean tetracylines, sulfonamides, trimethoprim, beta‐lactams, and macrolides antibiotic residues classes concentrations in water, fish, and sediment samples were (2.38 ± 5.687, 5.04 ± 2.116, 17.81 ± 21.782 ppb), (0.19 ± 0.124, 1.83 ± 3.641, 3.26 ± 1.434 ppb), (0.68 ± 0.503, 1.80 ± 1.679, 14.46 ± 10.638 ppb), (0.25 ± 0.263, 1.80 ± 1.679, 2.26 ± 2.25 ppb), and (0.76 ± 0.719 ppb, <LOD, 0.05 ± 0 ppb), respectively. Heavy metals mean concentrations for chromium (Cr), lead (Pb), arsenic (As), and cadmium (Cd) in water, fish, and sediment samples (0.05 ± 0.08, 0.73 ± 0.60, 2.69 ± 1.06 mg/kg), (0.003 ± 0.002, 0.14 ± 0.11 , 3.51 ± 2.61 mg/kg), (<LOD, 0.001 ± 0, 0.45 ± 0.17 mg/kg), and (<LOD, <LOD, 0.02 ± 0.02 mg/kg). Mercury (Hg) tested negative for all the samples analyzed. All fish samples tested had Cr concentrations exceeding the set maximum residue limit (MRL) of 0.05 mg/kg in fish muscle according to European Commission regulation 2016. Sediments recorded the highest concentrations, followed by fish and water, for both heavy metals and antimicrobial residues. Levels of heavy metals detected in fish were not associated with noncarcinogenic risks. However, Pb and Cr levels detected in the fish tissues were noted to pose carcinogenic health risks and, therefore, threatens the public health safety of fish consumption in this area of study.