Occurrence, seasonal variation, and environmental risk of multiclass antibiotics in the urban surface water of the Buriganga River, Bangladesh.

Owing to the extensive use of antibiotics in hospitals, animal husbandry, and various human activities, antibiotic contamination is becoming an increasing global concern, including in Bangladesh. In Bangladesh, the Buriganga River is heavily polluted with multiple antibiotics, which can lead to antibiotic resistance in bacteria. In this study, we performed the first investigation of seasonal variations in the occurrence and spatial distribution of 29 antibiotics in the Buriganga River, Bangladesh, from wet season (August 2019) and dry season (February 2020). We also evaluate the potential environmental and resistance risks related to antibiotic contamination. The concentrations of metronidazole (9.1-970 ng L-1), sulfadiazine (below the limit of detection (<LOD)-790 ng L-1), and levofloxacin (<LOD-710 ng L-1) were the highest, and metronidazole, amoxicillin, and doxycycline were detected in all samples during both seasons. The number of antibiotics detected, and their overall concentrations were higher during the dry season (February) than during the wet season (August). Ecological risk assessment using risk quotients (RQs) indicated that levofloxacin (maximum RQ = 90), amoxicillin (58), and ciprofloxacin (21) could pose a high risk to aquatic organisms, whereas sulfamethazine, trimethoprim, doxycycline, and lincomycin pose a medium risk. The levels of seven antibiotics, trimethoprim, ciprofloxacin, levofloxacin, amoxicillin, ampicillin, cefotaxime, and metronidazole exceeded the antibiotic resistance thresholds. In conclusion, this study highlights the urgent need for further research with improved wastewater management practices and implement stricter regulations on antibiotic use to protect aquatic ecosystems and public health in Bangladesh.