Medicated livestock carcasses and landfill sites: Sources of highly toxic veterinary pharmaceuticals and caffeine for avian scavengers

Veterinary drugs are of concern in terms of potential environmental pollution and their negative impacts on avian scavengers. These pharmaceuticals reach vultures through the consumption of carcasses of previously treated livestock. Here, we analysed samples from livestock carcasses (n = 159), avian scavenger tissues (n = 116) and plasma (n = 312) for 49 compounds commonly used in veterinary medicine in Aragon (NE Spain) and nearby regions. Samples were analysed using liquid chromatography with electrospray ionization mass spectrometry (LC-ESI-MS/MS). We detected pharmaceuticals in 54.1% of livestock carcasses analysed (50.3% with antibiotics, 10.8% with NSAIDs). For veterinary pharmaceuticals in tissues and plasma from avian scavengers, we detected pharmaceuticals in 51.7% and 28.5% of samples, respectively. Antibiotics were detected in 50.9% and 25.3% while NSAIDs were determined in 6.0% and 5.5% of tissues and plasma from avian scavengers, respectively. Moreover, caffeine was detected in plasma in 73.7% of vultures sampled at landfill sites, indicating its usefulness as a biomarker of urban garbage ingestion. We found an association between livestock carcasses, especially pigs and chickens, and the presence of veterinary pharmaceuticals in avian scavengers. We highlight that carcass disposal for feeding avian scavengers must address the potential risks posed by veterinary pharmaceutical residues.