Introduction

Potential risks associated with releases of medicines into the environment have become an increasingly important issue for environmental regulators (Jørgensen and Halling-Sørensen 2000; Stuer-Lauridsen et al. 2000; Kümmerer 2004). This concern has been driven by widespread detection of human and veterinary medicines in environmental samples as a result of improved analytical capabilities and the commissioning of focused field surveys (Daughton 2001; Focazio et al. 2004; Webb 2004). Surface water-sampling programs in Europe (e.g., Buser et al. 1998; Ternes 1998; Calamari et al. 2003; Thomas and Hilton 2003; Alder et al. 2004; Ashton et al. 2004; Zuccato et al. 2004), North America (e.g., Kolpin et al. 2002; Metcalfe et al. 2003, 2004; Anderson et al. 2004; Focazio et al. 2004), and elsewhere (Heberer 2002) have shown the presence of many different classes of medicines, some of which are known to be environmentally persistent (Zuccato et al. 2004). Although some of these medicines are unlikely to be a risk to the environment because of low concentrations combined with low toxicity, others may pose considerable risks.