THE FATE OF ANTIBIOTICS APPLIED TO SOILS

Veterinary antibiotics are widely used to treat disease and protect the health of animals. Following administration, they may be metabolised and then excreted along with any metabolic products in excreta. The antibiotics may then be released to the environment during the application of manure and slurry to land. This study was therefore performed to develop an understanding of the potential releases of antibiotics to soils and the fate of the substances once in soils. Laboratory, field and modelling studies were performed with three major antiobiotic classes. Results demonstrated that antibiotics vary in terms of their sorption behaviour and persistence. Following application to underdrained soils, the substances can be rapidly transported to surface waters, the degree of transport is related to sorption behaviour. Studies into the leaching behaviour of the substances indicate that they have a low potential to move to groundwaters. During the studies, a number of transformation studies were identified and these may be more persistent and mobile than the parent compound, it is important that these are considered in the risk assessment process. The results of the experimental studies have been used to evaluate existing exposure assessment models. The evaluations are encouraging and indicate that the models are appropriate for risk assessment of veterinary medicines.