Pharmaceuticals and other contaminants of emerging concern (CECs) have been detected ubiquitously in aquatic environments and in organisms inhabiting those environments worldwide. The uptake, internal distribution, metabolism and excretion of these compounds and their putative metabolites have been less well studied. The purpose of this research was to develop a more detailed understanding of how pharmaceuticals of varying physicochemical properties are taken up by a model fish species, distributed to different organs and tissues, metabolized, and excreted under conditions of constant exposure. Bluegill (Lepomis macrochirus) were exposed to single pharmaceuticals at a target constant exposure concentration of 1,540 ng/L in flow-through aquaria for up to 30 days. Five pharmaceuticals commonly detected in water were studied: diclofenac, methocarbamol, rosuvastatin, sulfamethoxazole, and temazepam. Fish and water samples were collected at 1, 10, 20 and 30 days. Gonad, gut, liver, muscle, brain, and spleen samples were taken for histological and toxicological assessment, with subsamples collected and frozen for subsequent chemical analysis. Pharmaceuticals were extracted and isolated from fish tissue samples using a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) method commonly used in food safety testing, with analysis of the concentrated extract by high-performance liquid chromatography/tandem mass spectrometry (HPLC/MS/MS). Water samples are analyzed by direct aqueous injection HPLC/MS/MS. Quantitation was by isotope dilution using stable isotope analogues of the five target pharmaceuticals. Initial results from three tissue types suggest that differential pharmaceutical uptake into different fish tissues occurred. Consistent uptake of temazepam, in bluegill muscle, brain, and liver occurred over 20 days of exposure, at concentrations as high as 32 ng/g in liver. Sulfamethoxazole uptake occurred although less consistently in all three tissue types. Methocarbamol did not accumulate in muscle, although it consistently accumulated in brain and liver at less than 1 ng/g. Diclofenac and rosuvastatin inconsistently accumulated in muscle, brain, and liver. Aqueous exposure concentrations were typically 56 percent of the calculated aqueous concentration, reflecting other losses within the experimental system.

Adsorption and disposition of pharmaceuticals by bluegill exposed at constant concentrations in a flow-through aquatic exposure system

249th National Meeting (2015)

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