Occurrence profiling, risk assessment, and correlations of antimicrobials in surface water and groundwater systems in Southwest Nigeria.

The presence of antimicrobials in water has grown into a major global health concern. This study thus focused on the presence, ecological implications, and potential health risks associated with nine antimicrobials: five antibiotics (ampicillin, chloramphenicol, ciprofloxacin, metronidazole, and tetracycline) and four parabens (methylparaben, ethylparaben, propylparaben, and butylparaben) in surface water and groundwater samples collected from three Southwestern States in Nigeria (Osun, Oyo, and Lagos States). These antimicrobials were widely detected across the three States with ciprofloxacin being the most dominant having maximum average concentrations of 189 μg L and 319 μg L in surface water and groundwater respectively. The range of average concentrations of antibiotics in surface water are 47.3-235 μg L (Osun), 27.9-166 μg L (Oyo) and 52.1-159 μg L (Lagos). For groundwater, it is 35.3-180 μg L (Osun), 26.5-181 μg L (Oyo) and 32.3-319 μg L (Lagos). The average concentrations of all parabens were 32.4-153 μg L, 53.4-80.1 μg L, and 83.2-132 μg L for surface water and 46.7-55.7 μg L, 53-117 μg L, and 62.4-118 μg L for groundwater in Osun, Oyo, and Lagos States respectively. Methylparaben was most frequently detected paraben with average concentrations of 153 μg L and 117 μg L in surface water and groundwater respectively. The measured environmental concentrations of these antimicrobials pose a significant ecological risk while those of ciprofloxacin and ampicillin pose a high health risk to all population groups studied. The average concentrations of antibiotics investigated in this study exceeded their threshold values for Predicted No-Effect Concentrations (PNEC) associated with resistance selection, except for tetracycline.