Human pharmaceuticals in surface waters

Human pharmaceuticals are widely used and can reach surface waters, where they have the potential to exert biological effects on aquatic non-target organisms. Due to the high number of pharmaceutical drugs used in human medicine throughout the world, it is necessary to select the pharmaceuticals to search for, prior to implementing any environmental measurements and any extensive environmental risk assessment (ERA). This paper describes a methodology developed in order to define this selection. The prioritization scheme consists in three tiers. First, a preliminary classification based on the assessment of exposure is implemented. This exposure assessment is determined by calculating predicted environmental concentrations (PECs) for each pharmaceutical according to the European Medicine Evaluation Agency's (EMEA's) environmental risk assessment guidelines [EMEA, 2006. European Medicine Agency Guideline on the Environmental Risk Assessment of Medicinal Products for Human Use. EMEA/CHMP/SWP/4447/00.]. In the second step, the preliminary classification is reviewed on a case-by-case hypothesis basis using all the biological data available: ecotoxicological, pharmacological (mechanism of action (MoA), enzyme modulation, adverse effects) and physicochemical data (log K(ow)). Finally, an additional step is used to select priority compounds among molecules showing the same chemical structure and the same mechanism of action. We applied this methodology to the French situation and prioritized 120 parent molecules and 30 metabolites. The final prioritization list gathers 40 parent compounds and 14 metabolites. Among the 40 parent molecules, 21 have already been found in the aquatic environment, indicating a good agreement between the theoretical approach and the environmental measurements. Parameters used to construct the effect criteria are discussed for their relevance.