Antibiotic body burden of Chinese school children: a multisite biomonitoring-based study

To explore the antibiotic body burden of Chinese school children, total urinary concentrations (free and conjugated) of 18 representative antibiotics (5 macrolides, 2 β-lactams, 3 tetracyclines, 4 quinolones, and 4 sulfonamides) were measured by ultraperformance liquid chromatography coupled to quadrupole time-of-flight mass spectrometry among 1064 school students recruited from 3 economically and geographically distinct areas in east China in 2013. All 18 antibiotics were detected in urine samples with the detection frequencies ranging from 0.4 to 19.6%. The antibiotics were detected in 58.3% of urine samples overall, and this detection frequency reached at 74.4% in one study site. Of them, 47.8% of the urine samples had a sum of mass concentration of all antibiotics between 0.1 (minimum) and 20.0 ng/mL, and 8 antibiotics had their concentrations of above 1000 ng/mL in some urine samples. Three veterinary antibiotics, 4 human antibiotics, and 11 human/veterinary antibiotics were found overall in 6.3, 19.9, and 49.4% of urine samples, respectively. The detection frequencies and concentration levels of antibiotics in urine samples differed by study areas. Concerning mixed exposures, a total of 137 combinations of antibiotics and 20 combinations of antibiotic categories were found overall. Two or more antibiotics or categories were concurrently detected in more than 20% of urine samples. On the basis of a usage analysis, contaminated food or environment might be relevant exposure sources for tetracyclines, quinolones, and sulfonamides.