Antibiotics in groundwater under locations with high livestock density in Germany

Antibiotics are deployed in large quantities both in human and in veterinary medicine. Studies show that antibiotic residues occur in the environment (e.g. soil and surface waters). In some cases they were also detected in ground and drinking water. However, the degree of groundwater pollution by antibiotic residues from livestock farming is unknown. Therefore, the federal environment agency (UBA) supported a project that aimed to investigate near-surface groundwater samples in regions of high livestock density and high risk of groundwater exposure to antibiotics. By applying worst case criteria on existing sampling sites of our groundwater monitoring grid (high amounts of manure on site, high precipitation, low adsorption capacity of soils, high nitrate concentrations in ground water, etc.) adequate sampling sites were identified as well as relevant antibiotics (amount of application, water solubility, biological stability, etc.) by a literature review and contacts to local veterinary authorities. In total, groundwater at 48 sampling sites was selected for analyses of 23 antibiotic substances. Out of the 23 antibiotics, only three sulfonamides could be detected and quantified. With regard to the 48 sampling sites, at 39 locations no veterinary antibiotics were detected. At seven locations sulfadimidine and/or sulfadiazine was detected at low concentrations (<0.012 μg/L). Only sulfamethoxazole was repeatedly detected above 0.1 μg/L at two sites. Results show that translocation of veterinary antibiotics into near-surface groundwater in most parts of Germany does not occur above detection limits. Under unfavourable conditions leaching does occur but well below the limit values for pesticides (0.1 μg/L/0.5 μg/L). However, under some extreme conditions (to be identified by further research work) one antibiotic was present in groundwater above the pesticides limit values.