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Comparison of Predicted and Measured Pharmaceutical Concentrations in Streams

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A PhD fellow from the University of York measuring pharmaceutical concentrations in samples collected from the Rivers Foss and Ouse, United Kingdom, during her work at the U.S. Geological Survey (USGS) National Water Quality Laboratory. Photo Credit: Stephen Werner, USGS.

New study evaluated if predicted environmental concentrations (PECs) of pharmaceuticals (based on pharmaceutical usage data, degree of metabolism in humans, removal in wastewater treatment plants (WWTPs), and environmental dilution), reflect actual measured environmental concentrations (MECs) in two stream systems of different sizes and demographics.

The presence of pharmaceuticals in aquatic systems in the United States and Europe is well documented. Pharmaceuticals are designed to induce a biochemical response at very low concentrations, raising questions regarding the risk for unintended sublethal effects in exposed non-target organisms.

There are approximately 3,500 compounds currently being evaluated for pharmaceutical production in the United States and more than 1,400 pharmaceuticals that had obtained Food and Drug Administration approval as of the end of 2013. Acute ecotoxicity data are available for only a small portion of these compounds, and chronic toxicity data are even scarcer. In addition, little is known about the ultimate environmental fate of most pharmaceuticals.

These knowledge gaps prevent a full understanding of the effects of pharmaceuticals, if any, on non-target organisms in the environment. To fill these gaps experimentally, however, would require substantial economic investment. Prioritization methodologies provide a complementary approach to strategically identify which of the thousands of pharmaceuticals in use have the greatest potential to cause unintended outcomes in nontarget organisms.

Prioritization methods are commonly used but the representativeness of these approaches is currently unclear. Risk-based prioritization methods require an exposure prediction, which is commonly based on a simple algorithm to derive a PEC. The estimation of PECs is typically based on pharmaceutical usage data, degree of metabolism in humans, removal in WWTPs, and environmental dilution. This method was used to calculate the PECs in this study.

As part of an international study investigating urban contaminants, targeted monitoring was done in a single snapshot for 95 pharmaceuticals at 8 sites on the Rivers Foss and Ouse in the City of York, United Kingdom, during medium flow conditions. Twenty-five pharmaceuticals were detected in the water samples collected. The PECs were estimated for the 25 detected pharmaceuticals and compared with MECs in collected river samples.

A comparison of PECs to MECs indicates relative similarity in the smaller River Foss but not in the larger River Ouse. The demographics within the River Foss watershed are well defined, whereas the area within the River Ouse watershed has more complex demographics, such as inputs from tourism or post-secondary institutions, which may influence wastewater loading estimates used in the PEC estimations.

Prioritization of pharmaceuticals based on common modelling approaches representative of environmental data is important to streamline future efforts to understand the actual, as compared to the perceived, health risks of pharmaceutical exposure to humans and other organisms.

This study is part of a larger effort of the U.S. Geological Survey (USGS) Environmental Health Mission Area to provide information that will help resource managers understand how to effectively minimize potential risks to the health of humans and other organisms exposed to pharmaceuticals and other chemicals through recreation, drinking water, and other exposure routes.

This research was funded by the European Union's Seventh Framework Program for research, technological development, and demonstration under grant agreement no. 608014 (CAPACITIE), and by the USGS Toxic Substances Hydrology Program.


Burns, E.E., Thomas-Oates, J., Kolpin, D.W., Furlong, E.T., and Boxall, A.B.A., 2017, Are exposure predictions, used for the prioritisation of pharmaceuticals in the environment, fit for purpose?: Environmental Toxicology and Chemistry, v. 36, no. 10, p. 2823-2832, doi:10.1002/etc.3842.

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