A Scoping Study of Livestock Antimicrobials in Agricultural Streams of Alberta

Pharmaceuticals are commonly used in the livestock industry, and studies have demonstrated that some pharmaceuticals can reach receiving water bodies. The main objective of this study was to measure the occurrence and concentration of selected veterinary pharmaceutical compounds commonly used by the livestock industry in Alberta across streams varying in agricultural intensity. A total of 247 water samples were collected from 23 watersheds during the open water season between, May 2005 and May 2006. Samples were analyzed for 27 commonly used veterinary pharmaceuticals from the following compound classes: avermectins, beta lactams, fluoroquinolones, ionophores, lincosamides, macrolides, sulfonamides, and tetracyclines. Subsequently, 10 antimicrobials were detected: narasin, salinomycin, monensin, sulfamethazine, sulfathiazole, sulfadoxine, erythromycin, lincomycin, chlortetracycline, and oxytetracycline. Trace (ng.L-1) concentrations of antimicrobials were detected in 51% of the samples (127 out of 247 samples). Monensin and sulfamethazine were detected most frequently (34% and 8% of samples, respectively). Monensin concentrations ranged from below the detection limit of 2 ng.L-1 to 843 ng.L-1. Monensin detection frequencies in study watersheds were correlated to manure production percentiles and regional cattle densities. Monensin concentrations were found to be significantly correlated to several water quality parameters (e.g., NH3-N). Monensin detection frequencies were found to be significantly higher in the spring than in the fall. Maximum concentrations for the other nine antimicrobials detected ranged between 3 and 250 ng.L-1. The antimicrobials detected and their concentrations were found to be similar to those in some recent European and North American livestock pharmaceutical stream surveys. Findings from this study can inform future monitoring programs and provides ambient concentrations for environmental (fate and transport) and toxicity studies to better evaluate potential risks to humans and the receiving aquatic ecosystems.