Purpose and Scope

The occurrence of pharmaceuticals and their metabolites in natural waters can cause adverse effects on ecosystem health. Pharmaceuticals are designed to have physiological effects, and some disrupt the endocrine system or are toxic to aquatic species (Halling-Sørensen and others, 1998; Daughton and Ternes, 1999). Prior to this study, few data existed to quantify the occurrence or concentration of pharmaceutical chemicals in streams of the Tualatin River basin. The primary purpose of this study is to eliminate this data gap as a step toward determining whether this class of compounds affects ecosystem health in the Tualatin River basin. Until a range of contaminant concentrations is measured, the magnitude of the ecological effect cannot be assessed and the appropriate resource management actions cannot be designed.

Of the thousands of pharmaceutical chemicals being manufactured and used, only a small subset was included in this study. The 21 candidate compounds were selected based upon (a) their estimated national use, an important factor in determining which compounds are likely to be detected in stream water, and (b) laboratory recovery performance and compound-specific detection levels achievable in newly developed analytical detection methods. The target analyte list includes a wide range of chemical classes and pharmaceutical uses, from analgesics and antibiotics to anticonvulsants, antihistamines, and stimulants (table 1). The target analytes include several pharmaceutical metabolites; in some cases, the metabolite is likely to be measured in higher concentrations than the parent compound. Though the metabolites are important, the terminology in this report has been simplified such that the 18 pharmaceutical chemicals and 3 metabolites on the target analyte list are commonly grouped together and called “pharmaceuticals.”

For many reasons, including the lack of previous data and the high cost of analyzing water samples for pharmaceutical chemicals, this study was by necessity a reconnaissance. The sampling strategy paralleled the objectives of the study, which were to:

• Measure the occurrence and concentration of a target set of pharmaceutical chemicals in streams of the Tualatin River basin, with a focus on highly urbanized drainages;
• Estimate the removal rates of pharmaceutical chemicals within an advanced WWTF; and
• Assess the utility of pharmaceutical chemicals as tracers of human-related contamination of streams.

Most stream samples were collected from six sites in the highly urbanized Fanno Creek subbasin of the Tualatin River basin; two other samples were collected from nearby agricultural and forested drainages for comparison. These sites could be affected by many types of source pathways, but none have treated wastewater sources (other than septic) upstream. Additional samples were collected within, upstream, and downstream of a large advanced WWTF that discharges to the Tualatin River. The emphasis on an urban stream and the WWTF reflects the information needs of a growing population and those of Clean Water Services, which is the primary stormwater- and wastewater-management utility for the urban areas of Washington County in the Tualatin River basin.

This study was exploratory in nature and limited in its scope. Stream samples were collected just once from each location in late July 2002 during a period of low streamflow preceded by at least 2 weeks of dry weather. Results, therefore, are not indicative of stormwater runoff sources but should capture dry-weather sources such as permitted discharges, leaking sewer lines, illicit dumping, and storm-sewer/sanitary-sewer cross-connection problems, if present. The presence or relative importance of stormwater-related sources was not assessed. Sampling during low streamflow is advantageous because the sources are not diluted by rainfall runoff. Similarly, the dry-weather sampling strategy minimized the amount of stormwater delivered to the WWTF and maximized the volumetric fraction of treated effluent in the Tualatin River downstream of the facility’s outfall, thus making an assessment of the facility’s downstream effects more apparent and straightforward to quantify. These results, however, may not be representative of the presence of pharmaceuticals in the Tualatin River because the sampling design was biased towards sample collection conditions that increased the likelihood of detectable pharmaceutical concentrations.

The purpose of this report is to document the results of this study, draw conclusions related to the study’s objectives, and postulate future directions for similar research activities.