Occurrence of antibiotic residues in drinking water from a city of Guangdong Province and their exposure risk assessment

ObjectiveTo understandthe baseline level of antibiotic residues in drinking water in a city in Guangdong Province and the reduction effect of water treatment technology on antibiotic residues， and to clarify the health risks of exposure to the antibiotic residues.MethodsA total of 200 samples， including raw water， flocculation effluent， precipitation effluent， filtered water and finished water， were collected from 10 drinking water enterprises in a city of Guangdong Province. The occurrence of 92 antibiotics in water samples were detected using online solid phase extraction-ultra high-performance liquid chromatography-tandem mass spectrometry.ResultsThe detection rates of antibiotic residues in 5 groups of samples ranged from 0% to 60%， and the sulfonamides were the major detected antibiotics. Therein， a total of 20 antibiotic residues were observed in raw water， including sulfonamides， macrolides， quinolones and chloramphenicol antibiotics， with the concentrations ranging from （0.057±0.003） to （181.419±4.245）ng/L. The occurrence of antibiotic residues and their concentrations observed in the samples of raw water from river were higher than those from reservoir. The water treatment process effectively removed the antibiotic residues from raw water， the removal rate ranged from 39.89% to 78.85%. Consequently， the antibiotic residues were nearly undetectable in finished water samples. However， the antibiotic residues still be detectable in finished water when river water was used as raw water. For the exposure assessment， the results showed that the population posed a higher risk of being exposed to antibiotics through this drinking water.ConclusionAttention should be concerned to the potential risk associated with this finished water.