Variations in bioconcentration of human pharmaceuticals from sewage effluents into fish blood plasma

The "Fish Plasma Model" has been proposed for prioritizing pharmaceuticals for in-depth environmental risk assessment efforts. The model compares estimated drug concentrations in fish plasma with human therapeutic plasma concentrations in order to assess the risk for a pharmacological interaction in the fish. In this study the equation used to estimate bioconcentration from water to fish blood plasma was field-tested by exposing rainbow trout in situ to sewage effluents from three treatment plants. Measured plasma levels of diclofenac, naproxen, ketoprofen and gemfibrozil were similar or lower than those modelled, which is acceptable for an early tier. However, measured levels of ibuprofen were >200 times higher than modelled for the largest plant (Gryaab Göteborg). Comparing measured fish plasma concentrations to the human therapeutic concentrations ranked the relative risks from the pharmaceuticals. Diclofenac and gemfibrozil, followed by ibuprofen, presented the highest risk for target interactions, whereas naproxen and ketoprofen presented little risk. Remarkably, measured bioconcentration factors varied considerably between sites. This variation could not be attributed to differences in water concentrations, temperatures, pH or exposure times, thereby suggesting that chemical characteristics of effluents and/or recipient waters strongly affected the uptake/bioconcentration of the pharmaceuticals.