Transport of veterinary antibiotics in overland flow following the application of slurry to arable land

An exposure assessment for selected pharmaceuticals within a watershed in Southern Ontario

Recent studies from a number of countries have shown that measurable concentrations of both human and veterinary pharmaceuticals can be found in a variety of environmental matrices such as surface and ground water, soils, and sediments. Few data are available that characterize the sources, exposure and effects of pharmaceuticals in the environment and there is clearly a need to define these parameters within a Canadian context. We present in this paper the first report in southern Ontario, Canada on the geographic and temporal distribution of pharmaceuticals detected within seven tributaries receiving primarily agricultural inputs in a typical watershed. Of the 28 pharmaceuticals surveyed, 14 were detected in the streams sampled (n=125). Temporal trends in concentration for five frequently detected pharmaceuticals show pulses occurring between May and November of 2003 at similar but varying times over the seasons, depending on the pharmaceuticals, flow rate, and precipitation. Fluctuations in concentration of ions indicative of agricultural run off, such as nitrate and phosphate, were not found to be useful predictors of changes in pharmaceutical concentration (P>0.4), however a significant correlation between dissolved organic carbon and monensin and carbamazepine concentrations were observed (P<0.013). Exposure profiles illustrating concentration distributions for three of the more prevalent pharmaceuticals detected, including lincomycin, monensin and carbamazepine, showed a log normal distribution, useful for calculating centiles of environmental concentrations. While distributions of estimated total potency of pharmaceuticals detected in the surface waters suggested small risks of environmental effects of mixtures to daphnia, green algae, Lemna gibba, and fish, the significance of non-target effects and impacts due to chronic low level exposures to chemical mixtures remains unclear.

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.

Determination of antimicrobial residues and metabolites in the aquatic environment by liquid chromatography tandem mass spectrometry

Antimicrobials are used in large quantities in human and veterinary medicine. Their environmental occurrence is of particular concern due to the potential spread and maintenance of bacterial resistance. After intake by the organisms, the unchanged drug and its metabolized forms are excreted and enter wastewater treatment plants where they are mostly incompletely eliminated, and are therefore eventually released into the aquatic environment. The reliable detection of several antimicrobials in different environmental aqueous compartments is the result of great improvements achieved in analytical chemistry. This article provides an overview of the more outstanding analytical methods based on liquid chromatography tandem mass spectrometry, developed and applied to determine antimicrobial residues and metabolites present in surface, waste, and ground waters.