Emission estimation and prioritization of veterinary pharmaceuticals in manure slurries applied to soil.

Veterinary pharmaceuticals (VPs) are emitted into the environment and transfer to groundwater and surface water is diffuse and complex, whereas actual information on the fate is frequently limited. For 17 VPs of potential concern in the Netherlands, we assessed sources and emission due to animal slurry applications to soil. Hence, we examined the use of VPs in four livestock sectors in the Netherlands for 2015-2018, and quantified animal excretion rates and dissipation during slurry storage. For almost all VPs, administrated quantities to the animals during the period 2015-2018 decreased. VP concentrations during a storage period of six months could decrease between 10 and 98% depending on the compound. Predicted concentrations of VPs in slurries after storage compared well with measured concentrations in the literature. Based on the storage model outcomes, we developed a residue indicator, that quantifies the potential for residues in applied slurry. This indicator agrees well with the most frequently detected VPs in the Dutch slurries, and is therefore useful to prioritize measures aiming at reducing VP emissions into the environment.