Occurrence and ecological risks of antibiotics and antiparasitics in surface water in urban lakes in Hanoi city, Vietnam

The presence of antibiotics in the environment is of significant concern due to their adverse effects on aquatic ecosystems. This study provides an assessment of potential ecological risks (RQ) associated with the concentrations of eight antibiotics and antiparasitics (amoxicillin—AMO, azithromycin—AZI, ciprofloxacine—CIP, ofloxacine—OFL, oxfendazole—OXF, lincomycin—LIN, sulfacetamide—SCE and sulfamethoxazole—SME) in the surface water of 13 urban lakes in Hanoi city, Vietnam during the period 2021–2023. The findings revealed considerable variations in the total concentrations of these 8 substances (T_AB), ranging from below the method detection limit (< MDL) to 2240 ng L⁻¹ with an average of 330.4 ng L⁻¹. Among the 8 antibiotics and antiparasitics examined, OXF, AMO, and SCE were undetectable, while the others were present at a range of concentrations (in ng L⁻¹): OFL: 129 (< MDL-1530); CIP: 87.1 (< MDL-608); LIN: 72.7 (< MDL-676); SME: 41.5 (< MDL-504); AZI: 0.03 (< MDL-1). The calculated RQ values for these antibiotics in the Hanoi lakes indicated a high ecological risk for OFL and CIP to bacteria, a medium to high risk for SME for phytoplankton, a high risk for LIN to phytoplankton, while the risk for invertebrates was deemed negligible for all antibiotics across all lakes. The strong, positive correlation between T_AB concentrations and different microbial and environmental variables (Escherichia coli, ammonium, phosphate, and chemical oxygen demand) suggests that untreated domestic wastewater is the primary pollution source in these Hanoi lakes. These results should be used to raise public awareness and to encourage the implementation of strategies targeted at managing antibiotic use. They also underscore the need to reduce inputs of untreated, antibiotic-containing wastewater into urban lakes, such as those in Hanoi and advocate for the establishment of national limits for antibiotic concentrations in surface water.