Prioritising veterinary medicines according to their potential indirect human exposure and toxicity profile

Veterinary medicines are used widely in the United Kingdom (UK) to protect animal health, prevent economic loss, and to help ensure a safe food supply. Veterinary medicine active ingredients (AIs) have been detected in various environmental media, including surface and groundwater, suggesting the potential for indirect human exposure from such residues. To fully assess the potential level of such exposures and the resultant potential risks to humans from all veterinary medicine AIs would be resource intensive. This paper proposes a method for prioritising veterinary medicine AIs according to estimates of their potential for indirect human exposure via the environment and their toxicity profile, and demonstrates its feasibility using an initial set of 83 veterinary medicine AIs approved for use in the UK. Overall, 13 AIs were classified as 'High' priority for detailed risk assessment, 19 as 'Medium' priority, 5 as 'Low' priority, and 46 as 'Very low' priority. The veterinary medicine AIs classified as 'High' or 'Medium' priority for detailed risk assessment included 15 different chemical groups and 10 different therapeutic indications. Overall, the proposed prioritisation scheme was demonstrated to provide a scientifically robust and pragmatic means of assessing the relative priority of veterinary medicine AIs for further detailed risk assessment regarding human exposure. However, there remain a number of data gaps that, if filled, would improve the accuracy of the resultant prioritisation.