Reconnaissance of Pharmaceutical Chemicals in 

Urban Streams of the Tualatin River Basin, Oregon, 2002 

Scientific Investigations Report 2009–5119

Prepared in cooperation with Clean Water Services 

U.S. Department of the Interior

U.S. Geological Survey

carbamazepine

caffeine

s-ibuprofen

cotinine

acetaminophen

O

O

N

N N

N

CH3

CH3

H3C

N

O

NH2

N

N O
Front Cover:

Top left: Tualatin River at Tualatin City Park, Oregon, July 19, 2008.

Top right: Common preparations of over-the-counter and prescription pharmaceutical chemicals.

Bottom right: Treatment basin at Clean Water Service’s Rock Creek Wastewater Treatment Facility, Hillsboro, Oregon, 1998.

Back Cover:

Top left: Photograph of Fanno Creek at 56th Avenue, Portland, Oregon, April 8, 2003.

Bottom left: Photograph of Fanno Creek at Scholls Ferry, near Allen Blvd., Portland, Oregon, April 8, 2003.

Right: Photograph of Fanno Creek downstream of footbridge in Durham City Park, Oregon, April 6, 2003.

All photographs by Stewart Rounds, U.S. Geological Survey.
Reconnaissance of Pharmaceutical 

Chemicals in Urban Streams of the 

Tualatin River Basin, Oregon, 2002

By Stewart A. Rounds and Micelis C. Doyle, U.S. Geological Survey; 

Patrick M. Edwards, Portland State University; and Edward T. Furlong, 

U.S. Geological Survey

Prepared in cooperation with Clean Water Services

Scientific Investigations Report 2009–5119

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2009

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Rounds, S.A., Doyle, M.C., Edwards, P.M., and Furlong, E.T., 2009, Reconnaissance of pharmaceutical chemicals 

in urban streams of the Tualatin River basin, Oregon, 2002: U.S. Geological Survey Scientific Investigations 

Report 2009–5119, 22 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Background............................................................................................................................................1

Study Area..............................................................................................................................................3

Purpose and Scope .......................................................................................................................................4

Methodology...................................................................................................................................................6

Sample Sites..........................................................................................................................................6

Sampling and Processing Methods...................................................................................................8

Laboratory Analysis..............................................................................................................................9

Quality Assurance.................................................................................................................................9

Pharmaceutical Chemical Detections and Concentrations .................................................................10

Reconnaissance Results ...................................................................................................................10

Comparison to Other Data.................................................................................................................14

Effects of Wastewater Treatment....................................................................................................16

Use of Pharmaceutical Chemicals as Tracers of Human-Related Stream Contamination....18

Summary and Conclusions.........................................................................................................................18

Acknowledgments.......................................................................................................................................19

References Cited..........................................................................................................................................19

Tables

Table 1. Pharmaceutical chemicals and metabolites included in this study .................. 5

Table 2. Samples collected for pharmaceutical chemical analysis in the Tualatin

River basin, Oregon, 2002 .................................................................. 6

Table 3. Results of quality control analyses for pharmaceutical chemicals included in

this study .................................................................................... 10

Table 4. Results of pharmaceutical chemical analyses .......................................... 12

Table 5. Detection frequency for pharmaceutical chemicals analyzed in this study ......... 14

Table 6. Apparent removal rates of pharmaceutical compounds from wastewater by

the Durham WWTF ........................................................................ 16

Figures

Figure 1. Map of the Tualatin River basin, Oregon ................................................ 3

Figure 2. Map showing location of sites sampled in this study ................................. 7

Figure 3. Schematic diagram of summertime treatment processes at Clean Water 

Services’ Durham wastewater treatment facility in 2002 .............................. 8

Figure 4. Boxplot showing concentrations of pharmaceuticals and metabolites

detected in stream and river samples in this study and instream

concentrations from a 1999–2000 national study ....................................... 15
iv

Conversion Factors, Datums, and Acronyms

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon (gal) 0.003785 cubic meter (m3) 

mile (mi) 1.609 kilometer (km)

million gallons (Mgal) 3,785 cubic meter (m3)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

ounce, fluid (fl. oz) 0.02957 liter (L) 

SI to Inch/Pound

Multiply By To obtain

centimeter (cm) 0.3937 inch (in)

kilogram (kg) 2.205 pound avoirdupois (lb)

liter (L) 33.82 ounce, fluid (fl. oz)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L). Concentrations of chemical constituents in sediment are given in 

nanograms per gram (ng/g).

Datums

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Acronyms

ESI electrospray ionization

EWI equal-width increment

HPLC high-performance liquid chromatography

LC50 concentration lethal to 50 percent of test organisms

MS mass spectrometer

NWQL National Water Quality Laboratory

SPE solid phase extraction

USGS U.S. Geological Survey

WWTF wastewater treatment facility
Reconnaissance of Pharmaceutical Chemicals in 

Urban Streams of the Tualatin River Basin, 

Oregon, 2002

By Stewart A. Rounds and Micelis C. Doyle, U.S. Geological Survey; Patrick M. Edwards, Portland State 

University; and Edward T. Furlong, U.S. Geological Survey

Abstract

A reconnaissance of pharmaceutical chemicals in 

urban streams of the Tualatin River basin was conducted in 

July 2002 in an effort to better understand the occurrence 

and distribution of such compounds, and to determine 

whether they might be useful indicators of human-related 

stream contamination. Of the 21 pharmaceutical chemicals 

and metabolites tested, only 6 (acetaminophen, caffeine, 

carbamazepine, codeine, cotinine, and sulfamethoxazole) 

were detected in filtered stream samples from 10 sites. The 

concentrations of most of the detected compounds were 

relatively low (less than 0.05 microgram per liter). The most 

frequently detected compounds were cotinine (a nicotine 

metabolite, 8 of 10 samples) and caffeine (a stimulant, 7 

of 10 samples). More compounds were detected in urban 

stream samples than in samples from forested or agricultural 

drainages.

Filtered water samples also were collected from four 

locations within an advanced wastewater treatment facility 

to quantify the relative amounts of these chemicals in a 

municipal waste stream and to determine the degree to which 

those chemicals are removed by treatment processes. Fifteen 

pharmaceutical chemicals or metabolites were detected in 

wastewater treatment facility influent, with concentrations 

far exceeding those measured in streams. Only five of those 

compounds, however, were detected in the treated effluent 

(carbamazepine, cotinine, ibuprofen, metformin, and 

sulfamethoxazole) and most of those were at concentrations 

less than 0.2 microgram per liter.

The target pharmaceutical chemicals and metabolites 

showed limited potential for use as tracers of specific types 

of human-related contamination in Tualatin River basin 

streams because of widespread sources (caffeine, for example) 

or extremely low concentrations. Caffeine and cotinine are 

likely to be good indicators of sources that can occur in 

urban areas, such as sewage spills or leaks or the widespread 

use and careless disposal of tobacco products and caffeinecontaining beverages. Neither compound, however, is likely 

to be a good tracer for a specific source unless that source 

is large. The presence of 1,7-dimethylxanthine (a caffeine 

metabolite) concurrently with caffeine might indicate the 

presence of untreated wastewater; in contrast, the absence of 

the metabolite might help rule out that source. Acetaminophen 

might make a good tracer for untreated wastewater because 

of its common usage, high concentration in raw wastewater, 

and effective removal via treatment. Carbamazepine and 

sulfamethoxazole have the potential to be good indicators of 

treated wastewater because of their incomplete removal in 

treatment facilities. Some of these pharmaceutical chemicals, 

either singly or in combination, might prove useful as tracers 

of contamination after further study.

Introduction

Background

Modern pharmacologic research since the middle of the 

19th century has resulted in the development or discovery 

of numerous drugs for the treatment of disease and the 

relief of ailments. The numbers and types of these drugs, 

or pharmaceutical chemicals, and the amounts used, have 

increased greatly in the last several decades, to the point where 

thousands of drugs are used today. Many are in common 

or daily use in the world’s developed countries (Kaufman 

and others, 2002). Increased use can lead to increased 

concentrations in waste streams and the potential for release 

of ever larger loads of these compounds to the environment. 

Prior to the last 10 years, few studies had been performed to 

determine the sources, transport, and fate of such compounds. 

An array of published studies now are available showing that 

pharmaceutical chemicals and their metabolites are present 

in streams at a wide range of concentrations, particularly 

downstream of human population centers (Halling-Sørensen 

and others, 1998; Daughton and Ternes, 1999). Researchers 

have investigated the occurrence of pharmaceuticals in 

surface waters (Buser and others, 1998; Kolpin and others, 
2 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

2002; Calamari and others, 2003; Löffler and others, 2005) 

and groundwater (Seiler and others, 1999; Hinkle and 

others, 2005; Barnes and others, 2008), the presence of such 

compounds in and their removal from wastewater (Ternes, 

1998; Ternes and others, 2004; Jones and others, 2005), and 

the ecological effects of these compounds (Wilson and others, 

2003; Gagné and others, 2006; Kim and others, 2007).

Despite these research efforts, few data exist to quantify 

the occurrence, concentration, and likely ecological effects 

of pharmaceutical chemicals in surface waters. A national 

reconnaissance was carried out in 1999–2000 by the U.S. 

Geological Survey (USGS) to assess the presence and 

concentrations of a suite of pharmaceuticals and other 

compounds in 139 streams across the United States (Kolpin 

and others, 2002). That study provides a good framework 

and baseline for developing a better understanding of the 

occurrence of pharmaceuticals and their metabolites in the 

Nation’s streams, but was not designed to determine the 

occurrence and effects of these compounds on a local scale; 

for example, only three water samples from Oregon were 

analyzed as part of that study. Given a growing and aging 

population with increased reliance on pharmaceuticals 

for the treatment of medical conditions, increased use of 

pharmaceuticals in agriculture, and greater public interest 

in the quality of drinking water and the health of aquatic 

species, the need to learn more about the occurrence and 

concentrations of pharmaceutical chemicals in Oregon’s 

streams is becoming increasingly important.

Some important source pathways of pharmaceutical 

chemicals, such as wastewater treatment facilities (WWTFs, 

which receive waste from hospitals, households, and 

municipal industries), have been identified in previous studies 

and need to be considered and assessed locally. Ternes 

(1998) was one of the first to document the presence of 

pharmaceuticals in raw and treated wastewater, using samples 

from selected WWTFs in Germany. Most modern WWTFs 

were not designed specifically to remove pharmaceutical 

chemicals from the waste stream. Many such chemicals 

are removed fairly efficiently through standard wastewater 

treatment, but others are not. Even if a large fraction of a 

pharmaceutical is removed through treatment, the remaining 

load still may constitute a large source to the receiving 

water body. Similar conclusions were reached in other 

studies in which higher concentrations of pharmaceuticals 

were measured downstream of WWTFs or population 

centers (Buerge and others, 2003; Kolpin and others, 2004; 

Glassmeyer and others, 2005; Gagné and others, 2006; Han 

and others, 2006; Karthikeyan and Meyer, 2006; Wilkison and 

others, 2006; Guo and Krasner, 2009). Research by Bedner 

and MacCrehan (2006) suggested that the chlorination process 

used in some WWTFs might transform acetaminophen, 

a common analgesic and one of the most widely used 

pharmaceutical chemicals, into a more harmful form. It is not 

just the parent pharmaceuticals, therefore, but their metabolites 

and degradates that must be studied to better understand the 

full effect of pharmaceuticals in the environment.

The potential for ecological effects caused by the 

presence of pharmaceuticals and their metabolites in aquatic 

systems is poorly understood at this time (2009). Because 

these compounds inherently affect physiological processes, it 

is likely that a measurable and potentially harmful ecological 

effect could occur at some concentration, but more research 

is necessary to define the ecological risks. Gagné and others 

(2006), for example, detected a wide range of pharmaceuticals 

in municipal treatment facility effluent and determined 

that such compounds have the potential to produce a toxic 

response in rainbow trout. Kim and others (2007) examined 

the toxicity of four widely used pharmaceuticals and six 

sulfonamide antibiotics and determined that several might 

have acutely toxic effects at concentrations greater than 

1 mg/L and that some potential ecological risk is present at 

lower concentrations. Han and others (2006) assessed the 

ecotoxicological effect of a handful of pharmaceuticals on 

a common plankton species, determined that toxic effects 

can occur at sufficiently high concentrations, and found that 

although typical pharmaceutical concentrations downstream 

of certain WWTFs did not result in a significant risk, the 

potential for significant risk did exist. The ecological effects 

of pharmaceuticals in the environment is a subject with many 

unexplored topics such as synergistic effects, the risks of 

chronic and multiple-year exposure to trace concentrations, 

and the risks resulting from pharmaceutical metabolites and 

degradates.

In addition to WWTF sources, pharmaceuticals and 

other biological and chemical contaminants can enter 

surface waters through accidental or illicit dumping, poorly 

managed or failing on-site or septic systems, storm-sewer/

sanitary-sewer cross connections, and unmanaged pet and 

animal wastes, among other sources. Proactive management 

and protection of aquatic resources would greatly benefit 

from the development of one or more definitive methods of 

identifying and tracking these separate sources. A wide variety 

of techniques and tracers are being developed in response 

to this need. Genetic techniques, for example, are becoming 

increasingly useful in identifying the sources of bacteria 

detected in streams (Stoeckel and others, 2004). Chemicals 

such as caffeine historically have proven useful as markers of 

human-related contaminant sources (Buerge and others, 2003), 

but that use may be diminishing because of the widespread 

consumption and careless disposal of caffeinated beverages. 

Other studies have found that, in addition to caffeine, certain 

anionic surfactants and fluorescent whitening agents (the 

“optical brighteners” in some laundry detergents) are good 

indicators associated with fecal coliform contamination 

(Sankararamakrishnan and Guo, 2005). Standley and others 

(2000) found that certain fragrance compounds, in conjunction 

with caffeine, can be used as tracers of human-related 
Introduction 3

contaminant sources. The identification of a suite of chemical 

markers that is unique to human-related sources of stream 

pollution would prove invaluable to investigations of 

contaminant fate and transport as well as the management of 

water resources. 

Pharmaceutical chemicals represent a compound class 

with great potential for use as tracers of specific sources of 

anthropogenic pollution. For use as a tracer of human-related 

contamination, a candidate compound should have few or 

no natural sources, no normal means of entering the stream 

of interest, a well-defined usage pattern, a sufficiently long 

lifetime to allow detection in the environment, and a reliable 

and accurate means of detecting and quantifying its presence 

in water, sediment, or tissue samples. Many pharmaceutical 

chemicals fit this general profile, although it is unclear which 

candidate pharmaceuticals might make the best tracers for 

sources of human-related stream contamination.

Study Area

The Tualatin River basin in northwest Oregon includes 

the western edge of Portland (Oregon’s largest city) and 

Portland’s western suburbs and outlying communities. 

In 2002, the basin was home to a rapidly growing human 

population of about 500,000 (U.S. Census Bureau, 2006). 

The great majority of those people live within a designated 

urban growth boundary which contains the cities of Portland, 

Beaverton, Tigard, Tualatin, Hillsboro, and Forest Grove, to 

name just a few (fig. 1). The cities are located primarily on the 

valley floor and are gathered mainly toward the middle and 

eastern edge of the basin. From its headwaters in the forested 

Coast Range mountains to the west, the Tualatin River 

meanders east through agricultural areas on the valley bottom 

before skirting the southern edge of the urban area and joining 

the Willamette River south (upstream) of Portland.

Figure 1. Tualatin River basin, Oregon.

WILLAMETTE

TUALATIN

RIVER

RIVER

RIVER

COLUMBIA

Hagg

Lake

Dairy Creek

Gales

Creek

Scoggins

Creek

McKay

Creek

Rock

Creek

Fanno

Creek

Beaverton Creek

Lake

Oswego

Tualatin

Sherwood

Portland

Tigard

Beaverton

Farmington

Cornelius Hillsboro Forest

Grove

TUALATIN MOUNTAINS

CHEHALEM MOUNTAINS

COAST RANGE

WASHINGTON

COLUMBIA

OREGON WASHINGTON

TILLAMOOK

YAMHILL

CLACKAMAS

MULTNOMAH

DURHAM

ROCK

CREEK

0 10

10

20 MILES

0 20 KILOMETERS

EXPLANATION

Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000)

Projection: Oregon Lambert, North American Datum 1983

Designated urban growth boundary (2001)

Basin boundary

OREGON

Study

Area

Wastewater treatment facility

123°30'00 123°15'00 123°00'00 122°45'00 122°30'00

45°

45'

45°

37'

30"

45°

30'

45°

22'

30"

5

5

205

205

84

26

217
4 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

In a basin that is characterized by cool, wet winters 

and warm, dry summers, the Tualatin River typically has its 

highest streamflow of several thousand cubic feet per second 

in the winter during large eastward-moving Pacific storms, 

and its lowest flow of less than 200 ft3/s during late summer. 

Summer streamflow is reduced by irrigation withdrawals, 

but augmented by upstream reservoir releases and treated 

effluent from two large WWTFs. The Rock Creek and Durham 

WWTFs, operated by Clean Water Services, process an annual 

average of 60 Mgal/d of wastewater for more than 480,000 

customers. During the low-flow summer period, the WWTFs 

add about 70 ft3/s (45 Mgal/d), or as much as 35 percent, 

to the flow of the Tualatin River (Bonn, 2008a). The Rock 

Creek and Durham WWTFs are advanced tertiary treatment 

facilities that use activated sludge treatment and chemical 

precipitation to remove nutrients and organic matter, followed 

by chlorination, filtration, and dechlorination for disinfection. 

The Rock Creek WWTF discharges to the Tualatin River just 

south of Hillsboro, and the Durham WWTF discharges to the 

Tualatin River near the mouth of Fanno Creek near Durham 

(fig. 1).

Tualatin River tributaries are readily grouped by 

characteristics that mirror the predominant land use within 

their drainages. Fanno, Rock, and Beaverton Creeks are the 

major streams draining urban areas of the Tualatin River 

basin. Fanno Creek has a well-established and completely 

(100 percent) urbanized drainage. The presence of a large 

human population, with a relatively dense urban development 

structure, sanitary and storm-sewer network, and extensive 

impervious areas, results in a diverse array of potential sources 

of stream pollution that are different from those in agricultural 

or forested drainages. In contrast to Fanno Creek, the Gales 

Creek drainage is predominantly forested (70 percent forest, 

27 percent agricultural) and the Dairy Creek drainage has a 

large percentage of agricultural land use (50 percent) with 

most of the rest being forested (41 percent; data from 2001 

National Land Cover Database, see Homer and others, 2007).

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 
Purpose and Scope 5

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/sanitarysewer 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.

Table 1. Pharmaceutical chemicals and metabolites included in this study.

[The list of common names is far from complete and is included only for utilitarian purposes. Similarly, the list of uses may be incomplete. This information 

was obtained from the Merck Index (1989) and from common on-line information sources. CAS, Chemical Abstracts Service. CAS Registry Numbers® is a 

Registered Trademark of the American Chemical Society. CAS recommends the verification of the CASRNs through CAS Client ServicesSM. 

–, not applicable]

Compound CAS 

registry No. Common name Intended use

Acetaminophen 103-90-2 Tylenol Analgesic

Albuterol (Salbutamol) 18559-94-9 Ventolin, Airomir MDI Bronchodilator (for asthma)

Caffeine 58-08-2 No-Doz Stimulant

Carbamazepine 298-46-4 Epitol, Tegretol Anticonvulsant; antimanic (mood stabilizer)

Cimetidine 51481-61-9 Tagamet Antiulcerative (acid reducer)

Codeine 76-57-3 Robitussin AC Opioid narcotic; cough suppressant

Cotinine 486-56-6 – Metabolite of nicotine

Dehydronifedipine 67035-22-7 – Metabolite and photodegradation product of nifedipine (arterial 

dilator; antihypertensive)

Diltiazem 42399-41-7 Cardizem Antianginal; antiarrhythmic; antihypertensive

1,7-Dimethylxanthine 611-59-6 – Metabolite of caffeine

Diphenhydramine 58-73-1 Benadryl, Allerdryl Antihistamine; sedative

Fluoxetine 54910-89-3 Prozac Antidepressant

Gemfibrozil 25812-30-0 Lopid Antihyperlipidemic (lipid regulating agent)

Ibuprofen 15687-27-1 Advil, Motrin, Nuprin Analgesic; anti-inflammatory

Metformin 657-24-9 Glucophage Antidiabetic (antihyperglycemic)

Miconazole 22916-47-8 Micatin, Monistat Topical antifungal

Ranitidine 66357-35-5 Zantac Antiulcerative (acid reducer)

Sulfamethoxazole 723-46-6 Bactrim, Septra (component) Antibiotic; antibacterial

Thiabendazole 148-79-8 Arbotect, Mertect Systemic antifungal; livestock antiparasitic

Trimethoprim 738-70-5 Bactrim, Septra (component) Antibiotic; antibacterial

Warfarin 81-81-2 Coumadin Anticoagulant
6 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

Methodology

Sample Sites

Samples for pharmaceutical chemical analysis were 

collected from eight stream sites (Tualatin River tributaries), 

two Tualatin River sites upstream and downstream of 

discharge from an advanced WWTF, and four locations within 

that treatment facility (table 2, fig. 2). The stream sites were 

chosen to represent a range of urban, agricultural, and forested 

land uses in the Tualatin River basin, with an emphasis on the 

urban areas. Six of the stream sites (sites 1–6) are located in 

the highly urbanized Fanno Creek drainage, while site 7 on 

Gales Creek represents more of a forested drainage and site 8 

on Dairy Creek has substantial agricultural land use upstream. 

Sites 1 and 2 in the upper reaches of Fanno Creek, site 5 on 

Summer Creek, and site 6 on the unnamed creek represent 

small drainages in largely residential urban areas. The Summer 

Creek drainage may have a larger fraction of residences with 

on-site septic systems rather than service from the sanitary 

sewer system. The remaining two sites farther downstream 

on Fanno Creek (sites 3 and 4) include increasing amounts 

of commercial and industrial land use. In addition to pointsource discharges, few of which are present in the Fanno 

Creek drainage, pharmaceutical chemicals may be present in 

urban streams as a result of accidental discharge, intentional 

dumping of waste (from a recreational vehicle, for example), 

sanitary-sewer/storm-sewer cross connections, leaking sewer 

lines, and failing septic systems, to name a few. Caffeine may 

be present in streams as a result of people discarding coffeecup residue on the street, which then can be washed to a storm 

drain and from there into the nearest creek.

Samples were collected from four locations within Clean 

Water Service’s Durham WWTF to assess the concentrations 

of pharmaceuticals that are delivered to the facility and their 

removal from the waste stream. The Durham WWTF is an 

advanced treatment facility that uses state-of-the-art treatment 

technology and attains a higher level of phosphorus removal, 

for example, than 98 percent of WWTFs in the United States 

(Clean Water Services, 2002). The facility uses screening, 

primary settling, enhanced biological treatment, tertiary 

chemical treatment, chlorination, sand-bed filtration, aeration, 

and dechlorination processes (fig. 3). Although the treatment 

is designed primarily to remove solids, oxygen demand, 

ammonia, and phosphorus, the effluent is near drinking-water 

Table 2. Samples collected for pharmaceutical chemical analysis in the Tualatin River basin, Oregon, 2002.

[Sampling site No.: Location of sampling sites are shown in figure 2. WWTF, wastewater treatment facility; –, not applicable]

Sampling 

site No. Site type Site name

Site 

identification 

No.

Drainage 

area 

(mi2

)

Sample 

type Date Time

1 Urban Fanno Creek at 56th Avenue 14206900 2.4 regular 7-30-2002 9:00

duplicate 7-30-2002 9:00

2 Urban Fanno Creek near Allen Boulevard 14206925 8.9 regular 7-30-2002 9:40

duplicate 7-30-2002 9:40

3 Urban Fanno Creek at Highway 99W 14206942 24.8 regular 7-30-2002 9:15

4 Urban Fanno Creek at Durham City Park 452348122454701 31.7 regular 7-30-2002 10:10

duplicate 7-30-2002 10:20

5 Urban Summer Creek at Fowler Middle School 452559122472401 6.2 regular 7-29-2002 9:40

duplicate 7-29-2002 9:40

6 Urban Unnamed Creek at Walnut Street in Tigard 452547122465900 0.8 regular 7-29-2002 10:10

7 Forested Gales Creek at Old Highway 47 14204530 74.7 regular 7-25-2002 10:20

8 Agricultural Dairy Creek at Highway 8 14206200 229 regular 7-25-2002 11:25

9 Integrator Tualatin River at Cook Park 14206800 655 regular 7-31-2002 10:00

10 Integrator Tualatin River at Boones Ferry Road 14206960 692 regular 7-31-2002 11:00

11 WWTF Durham WWTF – headworks 452359122454501 – regular 7-31-2002 11:00

Durham WWTF – pre-filtration 452359122454502 – regular 7-31-2002 13:35

Durham WWTF – post-filtration 452359122454503 – regular 7-31-2002 10:20

Durham WWTF – effluent 452359122454504 – regular 7-31-2002 10:30

duplicate 7-31-2002 10:40

– Quality assurance Blank (organic blank water) – – blank 7-31-2002 16:00
Methodology 7

tac09-0352_fig02

Dairy Creek

WILLAMETTE

RIVER

TUALATIN

RIVER

TUALATIN

RIVER

Rock

Beaverton

Creek

Creek

Creek

Fanno

Gales

Creek

Summer Creek

5

5

405

26

217

Lake

Oswego

Durham

Tualatin

Portland

King

City

Tigard

Beaverton

Farmington

Hillsboro Cornelius

Forest

Grove

Dilley ROCK

CREEK

OREGON

Study

Area

7

8

2

5

6 3

9

10

4

11

1

123°06' 123°04' 123°02' 123°00' 122°58' 122°56' 122°54' 122°52' 122°50' 122°48' 122°46' 122°44' 122°42' 122°40' 45°

34'

45°

32'

45°

30'

45°

28'

45°

26'

45°

24'

45°

22'

EXPLANATION

Sampling site and No.

 1 Fanno Creek at 56th Avenue

 2 Fanno Creek near Allen Boulevard

 3 Fanno Creek at Highway 99W

 4 Fanno Creek at Durham City Park

 5 Summer Creek at Fowler Middle School

 6 Unnamed Creek at Walnut Street in Tigard

 7 Gales Creek at Old Highway 47

 8 Dairy Creek at Highway 8

 9 Tualatin River at Cook Park

 10 Tualatin River at Boones Ferry Road

 11 Durham wastewater treatment facility

Base modified from U.S. Geological Survey and Metro digital data sets (1:24,000)

Projection: Oregon Lambert, North American Datum 1983

Designated urban growth boundary (2001)

Rock Creek wastewater treatment facility

0 5

5

10 MILES

0 10 KILOMETERS

Figure 2. Location of sites sampled in this study.

quality and typically dilutes many of the regulated chemicals 

in the Tualatin River’s receiving water. The Durham WWTF 

serves a customer base of more than 200,000 people and 

has a dry-weather discharge of about 25 ft3/s (16 Mgal/d). 

On July 31, 2002, the day of sample collection, the mean 

facility discharge was 24 ft3/s, but ranged as high as 40 ft3/s 

and as low as about 12 ft3/s. Samples of influent (at the 

headworks) and effluent were collected. Additional samples 

were collected before and after the filtration step, which is 

downstream of primary, secondary, and tertiary treatment and 

after chlorination, but prior to final aeration and dechlorination 

(fig. 3). Samples were collected without attempting to 

follow a single parcel of influent through the WWTF; the 

6-hour residence time and multiple recirculation pathways 

within the facility make such a sampling strategy difficult 

to perform. Results from these samples, therefore, are only 

strictly comparable if the influent waste stream was somewhat 

invariant in its loading of pharmaceutical chemicals.
8 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

To assess the instream effect of WWTF effluent, samples 

were collected from the Tualatin River 0.6 mi upstream 

(site 9, Cook Park) and 0.6 mi downstream (site 10, Boones 

Ferry Road) of the Durham WWTF outfall on the same day 

and at about the same time that samples were collected from 

the WWTF. On July 31, 2002, streamflow in the Tualatin 

River was about 171 ft3/s upstream of the outfall and 198 ft3/s 

downstream of the outfall. These streamflows were estimated 

based on measured streamflows at several streamflow-gaging 

stations upstream and downstream of the WWTF outfall.

Sampling and Processing Methods

Water samples from stream and river sites were collected 

using standard USGS protocols. Where stream size and 

depth allowed, the depth- and width-integrating equal-width 

increment (EWI) water-sampling technique was used. In the 

EWI method, a sample is collected by lowering and raising a 

sampler through the water column at a constant specified rate, 

repeating the process at the center of a set of equally spaced 

locations in the stream cross-section, and compositing the 

collected waters (Edwards and Glysson, 1999). EWI samples 

were collected using either a DH-81 hand-held sampler 

for wadeable streams or a D-77 sampler for non-wadeable 

streams with a 3-L Teflon® sample bottle and a Teflon® cap/

nozzle assembly. The unnamed creek at Walnut Street (site 6, 

fig. 2) was not deep or large enough to use the EWI method; 

instead, a grab sample was collected using the protocols and 

considerations for nonstandard sampling documented by 

Shelton (1994). Samples were placed on ice for transport back 

to the USGS Oregon Water Science Center laboratory for later 

filtration. 

Samples of water were collected from four different 

locations at the Durham WWTF. Because of safety, access, 

and structural considerations at the facility, nonstandard 

sampling techniques were used, typically resulting in grab 

samples of the source water. Samples were placed on ice 

before transporting them to the laboratory for later filtration.

Special protocols were followed to prevent contamination 

of the water samples. The sampling crew was careful to 

avoid contact with or consumption of any products or 

materials that contain the target analytes in this study. For 

example, the potential introduction of trace amounts of 

caffeine into collected samples was minimized through the 

crew’s abstention from caffeine-containing beverages (such 

as coffee), and protecting the samples from contact with 

human exhalations. These types of sample-handling and 

contamination-avoidance procedures are described by Lewis 

and Zaugg (2003) in the USGS National Field Manual.

Standard USGS procedures for handling and filtering 

samples containing organic compounds were followed prior 

to the shipment of samples to the USGS National Water 

Quality Laboratory (NWQL) in Denver, Colorado. Samples 

were filtered using a stainless steel or aluminum 142-mm or 

293-mm diameter plate-filter assembly with a 0.7-micron pore 

size glass-fiber filter. A valveless-piston variable-speed pump 

with Teflon® tubing was used, and sufficient filtrate from each 

sample was collected to fill two 1-L amber glass bottles that 

had been cleaned and baked at 350°C. Standard protocols 

for sample processing are documented in section 5.2.2 of the 

USGS National Field Manual (Wilde and others, 2004). All 

filtered samples were shipped on ice to the USGS NWQL for 

analysis.

The use of filtered water samples in this study, a 

requirement of the laboratory analysis method, means that 

the results reflect only the dissolved fraction of the target 

compounds’ total mass in the collected water samples. 

Although many of the target compounds are fairly water 

soluble (some even are ionized under neutral pH conditions, 

which makes them extremely water soluble), a fraction of 

their mass in a whole-water sample may be associated with 

suspended particulate material. As a result, the measured 

concentrations from a filtered sample may be lower than 

the concentration that would be measured in a whole-water 

sample.

tac09-0352_fig03

Headworks

Alum Lime

Grit &

Screenings

Polymer

(Optional)

Primary

Sludge

Waste

Activated

Sludge

Primary

Clarifiers

Alum Chlorine

Contact

Air

Air Bisulfite

Dechlorination Filters

Post

Aeration

Polymer

(Optional)

Chemical

Sludge

Chemical

Clarifiers

Cl2

Biological

Nutrient

Removal

1: Headworks

2: Pre-filtration

3: Post-filtration

4: Effluent

Sample collection location

1 2 3 4

1

Figure 3. Summertime treatment processes at Clean Water Services’ Durham wastewater treatment facility in 2002. Water samples 

were collected at the four marked locations. (Diagram reproduced with permission from Clean Water Services.)
Methodology 9

Laboratory Analysis

Filtered water samples were analyzed for a suite of 18 

pharmaceuticals and 3 metabolites by the Methods Research 

and Development group at the USGS NWQL using a 

relatively new analytical method (Cahill and others, 2004; 

Furlong and others, 2008). In that method, the target analytes 

and an added performance surrogate first were removed from 

filtered 1-L water samples by passing the water through a 

solid-phase extraction (SPE) cartridge. The analytes then 

were eluted from the SPE cartridge using small volumes of 

methanol and acidified methanol, concentrated to near dryness, 

reconstituted into formate buffer with an internal standard, 

and filtered. The concentrates were analyzed using highperformance liquid chromatography interfaced with a mass 

spectrometer using electrospray ionization operated in the 

positive-ion mode (HPLC–ESI–MS). Selected-ion monitoring 

MS was used to improve sensitivity and specificity. For more 

details on the specific materials, extraction procedures, and 

instrument conditions, see Cahill and others (2004) or Furlong 

and others (2008).

The analytical method used in this study was still under 

development at the time of sample collection and analysis. For 

that reason, the lists of target analytes in the published method 

papers (Cahill and others, 2004; Furlong and others, 2008) 

are slightly different from the target analytes in this study. In 

the most recent version of the analytical method documented 

by Furlong and others (2008), 11 pharmaceuticals and 

3 metabolites were analyzed, all of which were included in this 

study. Seven additional compounds (cimetidine, fluoxetine, 

gemfibrozil, ibuprofen, metformin, miconazole, and ranitidine) 

were included in this study, six of which also were included 

by Cahill and others (2004). Of the 21 compounds analyzed 

in this study, only miconazole was omitted by both of the 

published method papers. Method detection limits and spike 

recovery information for all of the target analytes are included 

later in this report with the results and the quality assurance 

data. Because this method incorporates a mass spectrometer 

as a detector, the qualitative identification of a compound 

can be verified, if not reliably quantified, at concentrations 

less than the method detection limit (Childress and others, 

1999; Bonn, 2008b); such detections are reported as estimated 

concentrations only.

Quality Assurance

The quality assurance program for this study included 

field duplicate samples and equipment blanks, and laboratory 

blanks and spikes. The field equipment blank was composed 

of certified organic blank water (EM Science, Universal 

Blank Water, lot #42044: purity verification data available 

upon request) that was filtered and handled using the same 

procedures as those used for the stream samples. Duplicate 

water samples were collected at five sites (table 2) to test the 

reproducibility of field and laboratory procedures. In addition, 

as part of the laboratory method, each set of analyzed samples 

included a laboratory blank sample and a spiked blank sample.

Spike recovery results from this study, and from 67 

additional laboratory spike samples analyzed during method 

development in 2002, demonstrated that the analytical method 

produced mixed results for this set of 21 target analytes 

(table 3). For 11 of the analytes, the spike recovery was 

consistently greater than 60 percent, and results were deemed 

reliable enough to report without qualification. Mean spike 

recoveries for eight other analytes were between 20 and 

60 percent; this less reliable recovery requires that quantified 

concentrations for these compounds be reported only as 

estimates. Spike recoveries for the final two compounds on 

the target analyte list, metformin and miconazole, were poor 

(6 percent or less); any detections of these compounds were 

reported without quantification.

Blank samples from the field and the laboratory were, 

with one exception, devoid of the target analytes. A low-level 

concentration of fluoxetine (0.0039 μg/L) was detected in the 

equipment blank sample, reducing the reliability of any lowlevel detections for that compound; fluoxetine results already 

were qualified as estimates based on low spike recovery 

results. No other target compounds were detected in the blank 

samples. Table 3 lists the spike recovery data, blank results, 

and interpreted reporting guidance for each compound (report 

without qualification, report as estimate, etc.).

Duplicate sample results showed good agreement, 

providing assurance that the detection frequency and the 

quantified concentrations were reliable. For the five duplicate 

water samples included in this study, a target analyte was 

detected in 15 instances in which a paired duplicate result 

also was available. In 12 of the 15 instances, the analyte 

was detected in both samples; in only 3 instances was a 

compound detected in only 1 of the paired samples. As 

might be expected, the percent relative difference in the 

quantified concentrations of paired results was higher for the 

lowest concentrations. For concentrations less than 0.1 μg/L, 

the relative percent difference was about 19 percent (10 

comparisons), and that value decreased to about 5 percent 

for concentrations greater than 0.1 μg/L (2 comparisons). 

Concentrations closer to the detection limit, therefore, are 

expected to be more uncertain than those that are well above 

the detection limit.

Matrix interferences can cause quality assurance issues 

that are difficult to quantify. The influent sample from the 

Durham WWTF, although filtered, had a complex organic 

chemical signal that could not completely be cleaned up 

or avoided during the sample extraction and concentration 

process. These interfering chemicals were incompletely 

separated from the target analytes during the chromatographic 

procedure, thus decreasing signal-to-noise ratios, increasing 

detection limits, and decreasing the certainty of compound 

identification and quantitation. Although results from the 

Durham influent sample were double-checked by re-running 

the analysis, all those results have a greater uncertainty due to 

matrix interferences.
10 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

Pharmaceutical Chemical Detections 

and Concentrations

Reconnaissance Results

This reconnaissance of pharmaceutical chemicals in 

streams of the Tualatin River basin was conducted in late 

July 2002. Stream samples were collected between July 25 and 

July 30, and the Tualatin River and the Durham WWTF were 

sampled on July 31 (table 2). Late July in western Oregon 

typically is warm and dry, and streams in the Tualatin River 

basin at that time are composed predominantly of groundwater 

baseflow. In the case of the Tualatin River, additional flow 

comes from upstream reservoir releases and the treated 

effluent from two advanced WWTFs. Prior to sample 

collection, no measurable rain had occurred since July 8, 

although a trace was recorded on July 26 (USGS data: see site 

452359122454500, for example, at http://or.water.usgs.gov/

grapher/).

A wide variety of sources can deliver pharmaceutical 

chemicals to streams. During dry weather, such sources might 

include failing septic or other on-site waste-treatment systems, 

leaking sewer lines, permitted and accidental discharges, 

illicit and unpermitted dumping, sanitary-sewer/storm-sewer 

cross connections, and unmanaged or poorly managed pet and 

livestock wastes. Stormwater sources are not included in this 

reconnaissance, which is important to remember because the 

storm-sewer system in the study area generally discharges 

to the stream network rather than to a treatment facility. The 

dry-weather sampling increased the chances of detecting 

Table 3. Results of quality control analyses for pharmaceutical chemicals included in this study. 

[The 2002 spike recovery data were from laboratory data collected throughout fiscal year 2002 — before, during, and after this study. %, percent; 

Std. Dev., standard deviation of spike recovery results; μg/L, microgram per liter] 

Compound Clean 

blanks?

Range of 

spike recovery 

(this study, %)

Mean (and Std. Dev.) 

of 67 set spikes 

(2002 results, %)

Comment

Acetaminophen yes 69–88 72 (15) Results reported without qualification.

Albuterol (Salbutamol) yes 70–90 74 (10) Results reported without qualification.

Caffeine yes 75–104 85 (16) Results reported without qualification.

Carbamazepine yes 68–84 71 (11) Results reported without qualification.

Cimetidine yes 33–43 30 (9.3) Reduced probability of low-level detection. Reported 

concentrations are estimates.

Codeine yes 66–91 94 (25) Results reported without qualification.

Cotinine yes 68–92 74 (12) Results reported without qualification.

Dehydronifedipine yes 71–100 77 (15) Results reported without qualification.

Diltiazem yes 48–61 47 (11) Reported concentrations are estimates.

1,7-Dimethylxanthine yes 96–127 105 (36) Results reported without qualification.

Diphenhydramine yes 51–62 53 (11) Reported concentrations are estimates.

Fluoxetine no 19–43 27 (14) Blank problems (up to 0.004 μg/L). Reduced probability of 

low-level detection. Reported concentrations are estimates.

Gemfibrozil yes 59–87 30 (21) Reported concentrations are estimates.

Ibuprofen yes 24–121 51 (24) Variable spike recovery. Imprecise quantitation. Reported 

concentrations are estimates.

Metformin yes 0–2 4 (4.8) Very low probability of low-level detection. No concentrations 

reported, only detections.

Miconazole yes 1–22 6 (7.1) Very low probability of low-level detection. No concentrations 

reported, only detections.

Ranitidine yes 45–56 41 (13) Reported concentrations are estimates.

Sulfamethoxazole yes 64–90 51 (18) Reported concentrations are estimates.

Thiabendazole yes 73–94 75 (16) Results reported without qualification.

Trimethoprim yes 67–88 70 (12) Results reported without qualification.

Warfarin yes 59–80 63 (13) Results reported without qualification.
Pharmaceutical Chemical Detections and Concentrations 11

pharmaceuticals from dry-weather sources because dilution 

by rainfall was avoided. The absence of rain also meant that 

the Durham WWTF was handling its normal load of domestic 

and other municipal/industrial sewage; therefore, the effect 

of WWTF effluent on the Tualatin River was representative 

of summer low-flow conditions and the relative proportion of 

treated effluent in the river was somewhat maximized, thus 

making its source load easier to detect.

Of the 21 target analytes included in this study, six were 

not detected in any sample, and only six were detected in 

any of the stream or river samples (tables 4 and 5). Stream 

sample detections included cotinine, caffeine, acetaminophen, 

carbamazepine, codeine, and sulfamethoxazole, in decreasing 

order of detection frequency. Sulfamethoxazole and 

carbamazepine primarily were found in the Tualatin River 

rather than in the smaller drainages, and the main source 

of the two compounds in the river probably was treated 

WWTF effluent; none of the smaller creek sites have WWTF 

discharges upstream of their sampling locations. Fifteen of 

the 21 target analytes were detected in WWTF influent; in 

contrast, only five were detected in treated effluent.

The most commonly detected compound was cotinine, 

which was found in every urban stream sample, both samples 

from the Tualatin River, and all WWTF samples. Cotinine is 

a metabolite of nicotine, which is an ingredient of tobaccocontaining products; therefore, cotinine is delivered to 

municipal WWTFs on a consistent basis through the sanitary 

sewer. Given the widespread outdoor use of nicotinecontaining products, it is not surprising that cotinine was 

detected in all urban stream samples. Similarly, caffeine was 

the second most-detected compound, and it also was found 

in all urban stream samples. Caffeine is present in high 

concentrations in coffee-based beverages, soft drinks, and 

energy drinks, and the propensity of many people to discard 

the remains of those beverages on streets and parking lots 

may account for the prevalence of caffeine in urban stream 

samples. Wash-off from streets and parking lots typically 

is conveyed to the nearest stream through the storm-sewer 

system with minimal opportunity for degradation, and little 

of the storm-sewer network has been retrofitted to deliver 

stormwater to wetlands or other naturalized treatment 

facilities. Note that if wash-off from streets and parking lots 

was instrumental in delivering these compounds to streams, 

then the dry-weather sampling performed in this study 

may have been affected by previous stormwater delivery 

processes. Despite the universal detection of caffeine in urban 

stream samples in this study, none of those samples included 

detections of 1,7-dimethylxanthine, which is the primary 

metabolite of caffeine (Guerreiro and others, 2008) and is 

present in high concentrations in untreated wastewater. The 

absence of this metabolite in urban stream samples reinforces 

the suggestion that the source of caffeine to these urban 

streams does not include processing through the human body, 

and therefore does not come from treatment, septic, or sewerrelated sources.

Most of the target analytes in this study (15 of 21) 

were not detected in stream or river samples. Only three 

compounds (acetaminophen, caffeine, cotinine) were detected 

in urban stream samples, and the great majority of those 

detections were at concentrations less than 0.04 μg/L with 

half of those detections at less than 0.01 μg/L (table 4). For 

perspective, 0.01 μg/L is nearly identical to half a drop of 

the pure compound diluted into a 660,000-gal Olympic-sized 

swimming pool, and 660,000 gal is the total amount of water 

used if you were to flush a modern 1.6-gal water-saving toilet 

25 times a day for the next 45 years. With only a couple of 

exceptions, the detected concentrations were less than about 4 

to 5 times the analytical method detection limit. One sample 

did show a substantially higher concentration of caffeine 

(0.314 μg/L) than any other stream sample, perhaps indicating 

a nearby source. Only two compounds (acetaminophen, 

carbamazepine) were detected in Gales Creek and only one 

(caffeine) was detected in Dairy Creek, and all three were 

estimated at concentrations less than their method detection 

limits. Even the Tualatin River samples, which were affected 

by one or more upstream WWTF sources, showed only four 

compound detections (carbamazepine, codeine, cotinine, 

sulfamethoxazole), and two (codeine and sulfamethoxazole) of 

the four were estimated at concentrations less than the method 

detection limit. In general, this reconnaissance of the target 

pharmaceutical chemicals indicates that these compounds 

either are not present in Tualatin River basin streams or are 

present only at trace concentrations that are many orders 

of magnitude below their usage or pharmacological dosing 

levels. For many of these compounds, it is not yet known 

whether these trace concentrations have ecological effects.

The effects of upstream land use were not clearly defined 

with the limited number of samples collected in this study. 

The samples collected from the Gales (forested) and Dairy 

(agricultural) Creek sites, however, certainly had fewer of 

the target compounds detected and all such detections were 

estimated at concentrations less than their method detection 

limits. The target analyte list, however, did not include the 

most commonly used antibiotics used in veterinary medicine, 

which might partially explain the paucity of detections in the 

agricultural drainage. The biggest difference between these 

two samples and the urban stream samples was the consistent 

presence of caffeine and cotinine in the urban samples. 

Caffeine and cotinine, therefore, may be good indicators for 

sources associated with urban areas. The Gales and Dairy 

Creek sites have little upstream urban land use (2 and 7 

percent, respectively).
12 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002 Table 4. Results of pharmaceutical chemical analyses. 

[Sampling site No.: Location of sampling sites are shown in figure 2. –, not detected; E, concentration is an estimate; WWTF, wastewater treatment facility; N/D, not determined]

Sampling 

site No. Site type Site name Sample type

Concentration (micrograms per liter)

Acetaminophen

Albuterol (Salbutamol)

Caffeine

Carbamazepine

Cimetidine

Codeine

Cotinine

Dehydronifedipine

Diltiazem

1,7-Dimethylxanthine

Diphenhydramine

Method detection limit: 0.0180 0.0115 0.0080 0.0054 0.0061 0.0076 0.0068 0.0077 0.0079 0.0722 0.0074

1 Urban Fanno Creek at 56th Avenue regular E 0.0057 – 0.014 – – – E 0.006 – – – –

duplicate E 0.004 – 0.012 – – – E 0.0040 – – – –

2 Urban Fanno Creek near Allen Boulevard regular E 0.005 – 0.314 – – – 0.012 – – – –

duplicate – – 0.328 – – – 0.0091 – – – –

3 Urban Fanno Creek at Highway 99W regular – – 0.022 – – – 0.011 – – – –

4 Urban Fanno Creek at Durham City Park regular – – 0.022 – – – 0.012 – – – –

duplicate – – 0.028 – – – 0.015 – – – –

5 Urban Summer Creek at Fowler Middle School regular – – 0.0084 – – – 0.008 – – – –

duplicate – – E 0.0079 – – – 0.009 – – – –

6 Urban Unnamed Creek at Walnut Street in Tigard regular – – 0.034 – – – E 0.004 – – – –

7 Forested Gales Creek at Old Highway 47 regular E 0.016 – – E 0.0011 – – – – – – –

8 Agricultural Dairy Creek at Highway 8 regular – – E 0.0031 – – – – – – – –

9 Integrator Tualatin River at Cook Park regular – – – 0.038 – E 0.0024 0.0098 – – – –

10 Integrator Tualatin River at Boones Ferry Road regular – – – 0.046 – E 0.0028 0.014 – – – –

11 WWTF Durham WWTF – headworks regular 29 – 30 0.192 E 0.18 0.41 1.51 – E 0.0974 24 E 0.372

Durham WWTF – pre-filtration regular – – – 0.132 – – 0.031 – – – –Durham WWTF – post-filtration regular – – – 0.163 – – 0.048 – E 0.019 – –

Durham WWTF – effluent regular – – – 0.158 – – 0.050 – – – –

duplicate – – – 0.166 – – 0.042 – – – –

– Quality assurance Blank (organic blank water) blank – – – – – – – – – – –
Pharmaceutical Chemical Detections and Concentrations

13

Sampling 

site No. Site type Site name Sample type

Concentration (micrograms per liter)

Fluoxetine

Gemfibrozil

Ibuprofen

Metformin

Miconazole

Ranitidine

Sulfamethoxazole

Thiabendazole

Trimethoprim

Warfarin

Method detection limit: 0.0072 0.0064 0.0208 N/D 0.0088 0.0064 0.0321 0.0054 0.0063 0.0059

1 Urban Fanno Creek at 56th Avenue regular – – – – – – – – – –

duplicate – – – – – – – – – –

2 Urban Fanno Creek near Allen Boulevard regular – – – – – – – – – –

duplicate – – – – – – – – – –

3 Urban Fanno Creek at Highway 99W regular – – – – – – – – – –

4 Urban Fanno Creek at Durham City Park regular – – – – – – – – – –

duplicate – – – – – – – – – –

5 Urban Summer Creek at Fowler Middle School regular – – – – – – – – – –

duplicate – – – – – – – – – –

6 Urban Unnamed Creek at Walnut Street in Tigard regular – – – – – – – – – –

7 Forested Gales Creek at Old Highway 47 regular – – – – – – – – – –

8 Agricultural Dairy Creek at Highway 8 regular – – – – – – – – – –

9 Integrator Tualatin River at Cook Park regular – – – – – – E 0.015 – – –

10 Integrator Tualatin River at Boones Ferry Road regular – – – – – – E 0.014 – – –

11 WWTF Durham WWTF – headworks regular E 0.0404 – E 7.63 detected – E 0.264 E 0.204 – 0.0983 –

Durham WWTF – pre-filtration regular – – – – – – – – – –

Durham WWTF – post-filtration regular – – – – – – E 0.018 – – –

Durham WWTF – effluent regular – – – – – – E 0.033 – – –

duplicate – – E 1.77 detected – – E 0.033 – – –

– Quality assurance Blank (organic blank water) blank E 0.0039 – – – – – – – – –

Table 4. Results of pharmaceutical chemical analyses.—Continued [Sampling site No.: Location of sampling sites are shown in figure 2. –, not detected; E, concentration is an estimate; WWTF, wastewater treatment facility; N/D, not determined]
14 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

Comparison to Other Data

Samples were collected by the USGS in 1999–2000 from 

139 streams across the United States, including several from 

Oregon streams (Barnes and others, 2002; Kolpin and others, 

2002), in a reconnaissance of pharmaceutical chemicals, 

hormones, and organic wastewater contaminants. Results 

from that investigation provide a useful comparison to this 

study. The list of pharmaceutical compounds included in the 

national reconnaissance was similar to the target analyte list 

in this study, largely because the same analytical method 

was used. Seventeen of the target compounds in this study 

were included in the national reconnaissance, and of the 

six compounds that were detected in stream samples in this 

study, only carbamazepine was not included in the national 

reconnaissance. Results for the five remaining detected 

compounds are compared to results from the national study 

in figure 4. The concentrations detected in this study are 

similar to and consistent with those from the national study. 

Maximum concentrations detected in this study, however, 

were at least an order of magnitude less than the maxima 

from the national study. This could be due to chance, given 

that the national study included about 10 times more samples, 

but it also may indicate that samples from the Tualatin River 

basin have fewer or weaker upstream sources of the target 

pharmaceuticals.

In both the national reconnaissance and this study, a 

sample was collected from the Tualatin River at Boones 

Ferry Road (site 10). The sample in the national study was 

collected on June 3, 2000, was preceded by only 3 days of 

dry weather, and showed detections for caffeine, codeine, 

1,7-dimethylxanthine, sulfamethoxazole, and trimethoprim. 

In this study, only codeine, sulfamethoxazole, and cotinine 

were detected (carbamazepine also was detected but was not 

included in the national study). Concentrations of the detected 

compounds in the two samples were of similar ranges, but 

neither consistently higher nor lower. Because both samples 

were collected during the low-flow summer period, upstream 

sources of these compounds were likely to be similar. 

Although storm-related sources may have been more prevalent 

in the sample from the national study, such sources were 

not specifically assessed in this study and their importance 

remains unknown. In any case, the results indicate that the low 

concentrations and few detections obtained for the Tualatin 

River sample in this study are not an anomaly.

Table 5. Detection frequency for pharmaceutical chemicals analyzed in this study. 

[Grey shading highlights combinations with no detections. WWTF, wastewater treatment facility]

Compound

Detection frequency (detections/number of samples)

All streams Urban streams Forested streams Agricultural streams Tualatin River WWTF

Acetaminophen 3/10 2/6 1/1 0/1 0/2 1/4

Albuterol (Salbutamol) 0/10 0/6 0/1 0/1 0/2 0/4

Caffeine 7/10 6/6 0/1 1/1 0/2 1/4

Carbamazepine 3/10 0/6 1/1 0/1 2/2 4/4

Cimetidine 0/10 0/6 0/1 0/1 0/2 1/4

Codeine 2/10 0/6 0/1 0/1 2/2 1/4

Cotinine 8/10 6/6 0/1 0/1 2/2 4/4

Dehydronifedipine 0/10 0/6 0/1 0/1 0/2 0/4

Diltiazem 0/10 0/6 0/1 0/1 0/2 2/4

1,7-Dimethylxanthine 0/10 0/6 0/1 0/1 0/2 1/4

Diphenhydramine 0/10 0/6 0/1 0/1 0/2 1/4

Fluoxetine 0/10 0/6 0/1 0/1 0/2 1/4

Gemfibrozil 0/10 0/6 0/1 0/1 0/2 0/4

Ibuprofen 0/10 0/6 0/1 0/1 0/2 2/4

Metformin 0/10 0/6 0/1 0/1 0/2 2/4

Miconazole 0/10 0/6 0/1 0/1 0/2 0/4

Ranitidine 0/10 0/6 0/1 0/1 0/2 1/4

Sulfamethoxazole 2/10 0/6 0/1 0/1 2/2 3/4

Thiabendazole 0/10 0/6 0/1 0/1 0/2 0/4

Trimethoprim 0/10 0/6 0/1 0/1 0/2 1/4

Warfarin 0/10 0/6 0/1 0/1 0/2 0/4
Pharmaceutical Chemical Detections and Concentrations 15

Depending on the chemical properties of the target 

pharmaceuticals, these compounds might be more likely to be 

found in stream sediment rather than in the overlying water. 

Nilsen and others (2007) determined that sediment samples 

collected from streams in the lower Columbia River drainage 

network do contain trace concentrations of pharmaceutical 

chemicals. Four of the samples in that study were collected 

from either Fanno Creek near its confluence with the 

Tualatin River, or from the Tualatin River near the outfall 

of the Durham WWTF. Those samples included detections 

of caffeine, diphenhydramine, thiabendazole, diltiazem, 

miconazole, trimethoprim, dehydronifedipine, carbamazepine, 

cotinine, fluoxetine, and codeine, in descending order of 

detected concentration or frequency. Detected concentrations 

ranged from about 1 to about 70 ng/g of sediment. In contrast, 

only four of these compounds (caffeine, carbamazepine, 

cotinine, and codeine) were detected in filtered water samples 

from the same general sampling sites in this study. 

tac09-0352_fig04

This studyThis studyThis studyThis studyThis study

Acetaminophen Caffeine Codeine Cotinine Sulfamethoxazole

0.001

0.01

1

0.1

10

100

CONCENTRATION, IN MICROGRAMS PER LITER

National studyNational studyNational studyNational studyNational study

Median

75th percentile

Maximum

25th percentile

EXPLANATION

Detections from this study

Reporting level, national study

Tualatin River at Boones Ferry, 

national study

Estimated value, national study

Figure 4. Concentrations of pharmaceuticals and metabolites detected in stream and river samples in this study and instream 

concentrations from a 1999–2000 national study (Barnes and others, 2002). One site in the national study was from the Tualatin 

River at Boones Ferry Road, a site that also was sampled in this study. The concentration distributions from the national study

are truncated at their reporting level, though confirmed detections below the reporting level are shown at their estimated 

concentrations. If a box is not shown, then the 25th and 75th percentiles are at the reporting level.

The aqueous concentrations of pharmaceutical 

compounds in this study cannot be compared directly to the 

sediment-associated concentrations detected by Nilsen and 

others (2007) because the samples were not collected at the 

same time or from exactly the same location. Even if collected 

concurrently from the same site, water samples would reflect 

conditions at that time, whereas sediment samples (collected at 

1–2 cm depth by Nilsen) represent time-integrated processes 

of accumulation and degradation. Further research is necessary 

to quantify the concentrations and proportions of these 

compounds in various media (water, sediment, fish tissue), but 

it is instructive to make rough comparisons using available 

data, in the interest of learning more about instream processes. 

For example, caffeine was detected in water and in sediments 

from Fanno Creek near its mouth. Aqueous concentrations 

from this study were roughly 0.02 μg/L (identical to 

0.02 ng/mL or 0.02 ng/g), and the sediment-associated 

concentration measured by Nilsen and others (2007) was about 
16 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

57 ng/g. Given the fact that caffeine is not charged under 

neutral pH conditions, and that its octanol-water partition 

coefficient (Kow) is about 1.0, nearly equal concentrations 

of caffeine in water and in the organic component of 

the sediments would be expected. These data, however, 

indicate that the phases are not in equilibrium—the aqueous 

concentration is lower than expected based on the sedimentassociated concentration. Perhaps the caffeine in the aqueous 

phase is readily degraded or the upstream sources are 

sufficiently variable that the phases are never in equilibrium. 

In contrast to caffeine, many pharmaceutical chemicals (such 

as ibuprofen) have acid-base properties that greatly increase 

their aqueous solubility under environmentally relevant 

pH conditions and decrease the relevance of hydrophobic 

partitioning to sedimentary organic matter (Wells, 2006). 

When considering the fate of pharmaceutical chemicals in 

the environment, it is critical to know how their chemical 

properties affect their aqueous solubility, bioaccumulation, 

bio- and photo-degradation, and partitioning to sediments and 

the atmosphere. More research and sampling is needed to fully 

understand the presence and fate of pharmaceutical chemicals 

in Tualatin River basin streams, sediments, and biota.

Effects of Wastewater Treatment

The highest concentrations of any target analyte in this 

study were found in the influent sample from the Durham 

WWTF. Five compounds were detected at concentrations 

greater than 1 μg/L. Caffeine and acetaminophen had the 

highest concentrations (30 and 29 μg/L, respectively), 

followed closely by 1,7-dimethylxanthine (24 μg/L), 

ibuprofen (7.6 μg/L), and cotinine (1.5 μg/L) (table 4). The 

presence of these particular pharmaceuticals and metabolites 

in high concentrations in wastewater is entirely consistent with 

typical usage rates. Although caffeine is an active ingredient 

in some medications, the adult per capita consumption rate of 

caffeine through beverages has been estimated as 320 mg/d 

in the United States; no other pharmaceutical in this study has 

such a high consumption rate (Wilkison and others, 2006). 

Furthermore, a national usage survey performed in 1998–99 

reported that acetaminophen and ibuprofen were the two 

most commonly used pharmaceuticals, with caffeine in ninth 

place, not including the consumption of caffeine in beverages 

(Kaufman and others, 2002). Despite the high concentrations 

of these compounds in WWTF influent, 3 of these 5, and 

10 of the 15 target compounds detected in WWTF influent, 

were not detected in samples of the treated WWTF effluent. 

Only carbamazepine, cotinine, ibuprofen, metformin, and 

sulfamethoxazole were detected in the effluent (table 4).

The influent and effluent detection data from this study, 

although from a limited number of samples, can be used to 

calculate an apparent removal rate of these compounds due 

to treatment processes occurring in the Durham WWTF, 

assuming that the compound concentrations detected in 

influent and effluent are typical. Because WWTFs are efficient 

at removing particulate material, and because this study 

analyzed only filtered water samples, these calculated removal 

rates may be biased low, depending on the water solubility of 

the target compound. For those compounds that were detected 

in the influent but not in the effluent, a lower limit on the 

apparent removal rate can be estimated based on the analytical 

method detection limit for each compound. For those that 

were detected in influent and effluent, a percent removal 

can be computed directly (table 6). Most of the compounds 

detected in the influent were removed with fairly high 

efficiency (> 90 percent). Ibuprofen and sulfamethoxazole 

were mostly but incompletely removed (> 75 percent), but 

only a small fraction (< 20 percent) of the antiepileptic drug 

carbamazepine was removed. Results for ibuprofen were 

somewhat inconsistent because it was detected in only one of 

two duplicate effluent samples. Results from samples collected 

before and after filtration in the WWTF showed that filtration 

was not responsible for the removal of these compounds from 

the waste stream; most of the removal occurred prior to that 

treatment step.

Table 6. Apparent removal rates of pharmaceutical compounds 

from wastewater by the Durham WWTF. 

[Results are shown only for the 14 target compounds detected and quantified 

in Durham WWTF influent. If a compound was not detected in WWTF 

effluent, the method detection limit was used to compute the apparent removal 

rate; such instances are denoted with an asterisk (*). >, greater than; 

%, percent; WWTF, wastewater treatment facility]

Compound Apparent 

removal Compound Apparent removal

Acetaminophen > 99%* 1,7-Dimethylxanthine > 99%*

Caffeine > 99%* Diphenhydramine > 98%*

Carbamazepine 18% Fluoxetine > 82%*

Cimetidine > 97%* Ibuprofen > 77%

Codeine > 98%* Ranitidine > 98%*

Cotinine 97% Sulfamethoxazole 84%

Diltiazem > 92%* Trimethoprim > 94%*
Pharmaceutical Chemical Detections and Concentrations 17

Many other studies have evaluated the removal rates of 

pharmaceuticals from wastewater. Ternes (1998) investigated 

the occurrence and removal of a suite of pharmaceuticals in 

German WWTFs, and determined that more than 60 percent 

of the pharmaceutical residues were removed. Many were 

not detected in the treated effluent, some such as ibuprofen 

(90 percent removal) were mostly removed through 

treatment, and others such as carbamazepine (7 percent 

removal) were only partially removed. Those results for 

ibuprofen and carbamazepine mirror the results from this 

study. A 2004 survey of pharmaceuticals in South Korean 

WWTFs by Han and others (2006) showed similar results 

for ibuprofen (78 percent removal), but quite different results 

for carbamazepine (91 percent removal) and acetaminophen 

(9 percent removal). The type of treatment (primary versus 

secondary, trickling filter versus activated sludge, with 

or without nitrification and/or denitrification processes, 

chlorination versus UV disinfection) and the details of the 

treatment processes (residence time, etc.) can have an effect 

on the removal of pharmaceuticals from wastewater (Jones 

and others, 2005; Phillips and others, 2005).

Samples from the Tualatin River upstream and 

downstream of the Durham WWTF outfall provide an 

independent means of assessing the effect of WWTF 

effluent on the river. Three of the five target analytes 

detected in WWTF effluent (carbamazepine, cotinine, and 

sulfamethoxazole) also were detected in the Tualatin River 

upstream and downstream of the Durham outfall. For those 

compounds, a mass balance of sorts can be performed. 

Because the approximate flow in the river upstream of the 

outfall (171 ft3/s), the flow rate of the effluent (about 24 ft3/s), 

and the flow in Fanno Creek (< 5 ft3/s) are known, an 

expected downstream concentration can be computed. In the 

case of carbamazepine, the in-river concentration increased 

from 0.038 μg/L upstream to 0.046 μg/L downstream 

(table 4), which is consistent with an expected downstream 

concentration of about 0.052 μg/L based on a mass balance. 

Similarly consistent results were obtained for cotinine, 

with upstream and downstream measured concentrations 

of 0.0098 and 0.014 μg/L, versus an expected downstream 

concentration of 0.016 μg/L based on a mass balance. In-river 

concentrations of sulfamethoxazole were essentially the same 

upstream and downstream of the Durham WWTF outfall 

(0.015 and 0.014 μg/L), whereas the mass balance produced 

an expected downstream concentration of 0.017 μg/L; 

given the uncertainty involved in the analyses, these three 

concentrations are essentially identical. Ibuprofen was not 

detected in the river samples, perhaps providing evidence to 

question the detection of ibuprofen in treated effluent, where 

only one of two duplicate effluent samples showed a detection 

(1.77 μg/L). If ibuprofen had been present in treated effluent 

at a concentration of 1.77 μg/L, then the in-river downstream 

concentration should have been easily detected at an estimated 

concentration of 0.2 μg/L, which is 10 times higher than the 

method detection limit. The laboratory analytical method used 

in this study was not, perhaps, the best method for quantifying 

ibuprofen concentrations; new analytical methods for 

ibuprofen and other acidic pharmaceutical chemicals are under 

development.

In-river concentrations of carbamazepine and cotinine 

upstream of the Durham WWTF outfall (Tualatin River at 

Cook Park, site 9) can be shown to be consistent with the 

presence of a large WWTF source upstream of that location. 

The Rock Creek WWTF discharges treated effluent to the 

Tualatin River about 28 mi upstream of Cook Park, and the 

travel time from the WWTF outfall to Cook Park was about 

6–8 days under the flow conditions that occurred in late 

July 2002. For all of the carbamazepine in the Tualatin River 

at Cook Park to have come from the Rock Creek WWTF, 

the effluent flow rate from that facility would have to be 

about 41 ft3/s, assuming its carbamazepine concentration was 

identical to that in Durham WWTF effluent and assuming no 

instream degradation during the travel time to Cook Park. The 

measured Rock Creek WWTF effluent flow rate for that time 

period was about 39 ft3/s. A similar calculation for cotinine 

only required that the Rock Creek WWTF effluent flow rate 

be at least 34 ft3/s, and sources of cotinine from other urban 

streams such as Rock Creek certainly were present. It is 

likely, therefore, that concentrations of carbamazepine and 

cotinine in the Tualatin River upstream of the Durham WWTF 

outfall primarily are from the Rock Creek WWTF. Similar 

calculations for sulfamethoxazole reveal that the Rock Creek 

WWTF probably is an important source of that compound to 

the river, but it may not be the only source upstream of Cook 

Park unless the concentration of sulfamethoxazole in Rock 

Creek WWTF effluent was higher than the concentration in 

Durham WWTF effluent.

The ecotoxicological risk of carbamazepine to selected 

aquatic species has been studied by several research 

groups. Han and others (2006) studied the effects of several 

pharmaceutical chemicals on daphnia magna, a common 

planktonic crustacean, and determined that the typical 

concentrations of pharmaceuticals downstream of South 

Korean WWTFs were low enough that no appreciable 

risk existed. Indeed, the LC50 (concentration lethal to 

50 percent of test organisms) for carbamazepine cited in 

that research is 111 mg/L, about 2,400 times higher than 

the concentration detected in Tualatin River samples. A 

safety factor of 1,000 typically is applied in their analyses, 

indicating that the concentrations found in this study may 

not pose a significant ecological risk to this particular test 

organism. Related research by Kim and others (2007) 

showed little risk by carbamazepine to daphnia magna or 

to a test fish species. They reported potential concern for 

effects from acetaminophen and sulfamethoxazole, but the 

exposure concentrations they used were more than 60 times 

higher than those found in Tualatin River samples; the lower 

concentrations measured in this study would push the risk 

below their hazard thresholds. Another study by Oetken and 

others (2005) investigated the effect of carbamazepine on 
18 Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002

an oligochaete, a midge, and a freshwater snail species. The 

aquatic testing in that study indicated that the concentrations 

found in the Tualatin River would not pose a threat to these 

species. In general, insufficient data exist to completely 

ascertain the ecological risk of pharmaceutical chemicals to 

species that reside in the Tualatin River and its tributaries, 

but limited data for compounds such as carbamazepine, 

acetaminophen, and sulfamethoxazole suggest that the acute 

ecological risk under normal low-flow conditions is low. 

Although pharmaceutical chemical concentrations normally 

might be low in the Tualatin River, accidental releases or spills 

of sewage could greatly increase their instream concentrations 

and their associated ecological risk. In addition, low-level 

chronic exposure to those pharmaceutical chemicals that can 

act as endocrine disrupters could lead to a harmful ecological 

effect, but such an effect cannot yet be assessed.

Use of Pharmaceutical Chemicals as Tracers of 

Human-Related Stream Contamination

Although the analysis of samples for pharmaceutical 

chemicals is expensive, the cost might be justified if one or 

more of the compounds proved to be a good tracer for specific 

sources of stream contamination. Results from previous 

studies indicate that caffeine and selected pharmaceuticals 

may be useful as confirmatory evidence of contamination, 

if not sufficient as primary evidence (Seiler and others, 

1999; Verstraeten and others, 2005). Caffeine also has been 

proposed as an ideal tracer for certain types of sewage-related 

contamination of streams because of its high concentration 

in human waste and the absence of substantive natural 

sources (Ferreira, 2005; Wu and others, 2008). Unless the 

sewage-related stream contamination is large, however, the 

use of caffeine as a source indicator is limited because trace 

concentrations of caffeine appear to be common in urban 

streams. Indeed, caffeine was universally present in urban 

stream samples in this study at concentrations generally 

greater than 0.01 μg/L. That concentration is fairly easy 

to achieve with only a few spills of coffee, although other 

sources also may be present. For example, if coffee has a 

caffeine concentration of 350 mg/L (Seiler and others, 1999), 

and a stream such as Fanno Creek has a flow of about 4 ft3/s, 

then a caffeine concentration of 0.01 μg/L in the stream 

represents a spill of only 1 ounce of coffee residue that is 

completely mixed into the stream every 2.5 hours. A 1-ounce 

coffee spill need only mix into 5 minutes worth of the stream’s 

flow to achieve the highest concentration measured in this 

study (0.314 μg/L), a dilution level that is certainly possible, 

although perhaps unlikely. To use caffeine as an effective 

tracer for a sewer leak, the leak would have to be large enough 

to produce caffeine concentrations higher than a few tenths of 

a microgram per liter. At that level, a different indicator such 

as coliform bacteria or an optical brightener might prove to be 

less ambiguous, faster to analyze, and more cost-effective.

Although caffeine might be used only as a general tracer 

for mixed sources of human-related stream contamination, 

or as a tracer for large sewer leaks, compounds like 

acetaminophen, carbamazepine, and sulfamethoxazole 

might be useful as tracers under some circumstances. These 

compounds (a common analgesic, an antiepileptic drug, and 

an antibiotic, respectively) are unlikely to be detected in 

streams unless a human-related or veterinary source is present. 

Such a source could be a leaking sewer line, a failing septic 

system, illicit or unpermitted dumping, or a storm-sewer/

sanitary-sewer cross connection. In the presence of one of 

these sources, the instream concentration of acetaminophen 

ought to be easily measurable, given its high concentration 

in municipal wastewater (29 μg/L; table 4). Instream 

concentrations of carbamazepine and sulfamethoxazole might 

be lower than that of acetaminophen, at least in untreated 

sewage, but these compounds are not completely removed 

by wastewater treatment, so they could be used as tracers of 

either raw or treated wastewater sources. Carbamazepine has 

been proposed previously as a marker for human wastewater 

(Clara and others, 2004). In separate research, Glassmeyer and 

others (2005) suggested that pharmaceutical chemicals such 

as carbamazepine, diphenhydramine, and caffeine might be 

good indicators of the presence of human wastewater. Guo and 

Krasner (2009) recently determined that carbamazepine and 

primidone may be used as indicators of upstream wastewater 

sources. The data derived from this Tualatin River basin 

reconnaissance show that several of these pharmaceutical 

compounds might make good tracers for human-related 

contamination of streams under some circumstances, but 

that additional research and sampling are needed to further 

evaluate their potential use as tracers.

Summary and Conclusions

A reconnaissance of pharmaceutical chemicals and 

metabolites in urban streams and an advanced wastewater 

treatment facility was conducted on the west side of the 

Portland, Oregon, metropolitan area during low-flow 

conditions in July of 2002. Filtered water samples were 

analyzed for 21 target analytes using a solid-phaseextraction procedure followed by high-performance liquid 

chromatography and mass spectrometric detection. Only 6 

of the target compounds were detected in the 10 stream or 

river sites that were sampled. Among the urban stream sites, 

the only compounds detected were cotinine (a metabolite 

of nicotine), caffeine, and acetaminophen. The highest 

concentration in any stream or river sample was for caffeine in 

Fanno Creek at 0.314 μg/L, but the next highest concentration 

was almost an order of magnitude lower at 0.046 μg/L 

for carbamazepine in the Tualatin River downstream of 

two wastewater treatment facility outfalls. All compound 

concentrations measured in this study were consistent with 

the range of concentrations reported in a 1999–2000 national 
References Cited 19

survey of pharmaceutical compounds in United States 

streams by USGS, but maximum concentrations in this study 

were about an order of magnitude or more lower. Although 

this study is only a reconnaissance for the occurrence and 

concentrations of selected pharmaceuticals in Tualatin River 

basin streams, it appears that few pharmaceuticals are present 

in these streams, and when present, their concentrations are 

low. Furthermore, limited literature data suggest that the 

dry-weather concentrations of some compounds detected in 

this study are not high enough to be of ecological concern. 

Insufficient information is available, however, to fully assess 

the true ecological risk, including those associated with stormrelated conditions and potential spills or accidental releases.

Fifteen pharmaceuticals and metabolites were detected 

in untreated municipal wastewater, but most were efficiently 

removed through treatment. Only five compounds were 

detected in treated effluent from the Durham treatment 

facility (carbamazepine, cotinine, ibuprofen, metformin, 

and sulfamethoxazole), and two of those (ibuprofen and 

metformin) were detected in only one of two duplicate 

effluent samples. Of these compounds, only carbamazepine 

is somewhat resistant to removal through wastewater 

treatment, with an apparent removal of only 18 percent; all 

other detected compounds had at least a 77 percent estimated 

removal rate. The apparent removal rates determined in 

this study are consistent with some previous studies of 

pharmaceutical chemicals in wastewater treatment facilities, 

although published studies differ widely on the removal rates 

of carbamazepine and acetaminophen. Results indicate that 

wastewater treatment facilities are the primary sources of the 

low concentrations of carbamazepine and cotinine measured in 

Tualatin River samples. Published research indicates that the 

dry-weather concentrations of carbamazepine, acetaminophen, 

and sulfamethoxazole found in Tualatin River basin samples 

are unlikely to be toxic to the several plankton and freshwater 

snail species used as test organisms.

Several of the pharmaceutical chemicals and metabolites 

included in this study, either singly or in combination, 

show some potential to be useful tracers of human-related 

contamination of streams. Although caffeine and cotinine 

appear to be good indicators of a wide variety of sources that 

can occur in urban areas, they are not good indicators of any 

single sewage-related source, for example, unless that source 

is large enough to overcome the smaller background sources. 

If present along with caffeine, 1,7-dimethylxanthine (a 

caffeine metabolite) might indicate the presence of untreated 

wastewater; in contrast, the absence of the metabolite might 

help rule out a wastewater source, treated or untreated, 

because caffeine and 1,7-dimethylxanthine are effectively 

removed via wastewater treatment. Acetaminophen, 

carbamazepine, and sulfamethoxazole show some potential 

as tracers for specific types of contamination, either because 

of high concentrations in raw wastewater (acetaminophen) 

or because of incomplete removal by wastewater treatment 

(carbamazepine, sulfamethoxazole). Ibuprofen also has a high 

concentration in raw wastewater and potentially incomplete 

removal in wastewater treatment, but is not an ideal candidate 

because the analytical test method used in this study gave 

imprecise results for this compound. Additional research 

is needed to fully determine the potential value of these or 

other pharmaceutical chemicals and metabolites as tracers for 

stream contamination. Other potential tracers such as optical 

brighteners, fragrance compounds, and surfactants also merit 

further consideration.

Acknowledgments

This study was performed as part of a long-term 

scientific collaboration between the U.S. Geological Survey 

(USGS) and Clean Water Services. We appreciate the 

assistance and cooperation of Rob Baur and other staff at the 

Durham Wastewater Treatment Facility in providing access, 

information, and water samples. Jan Miller of Clean Water 

Services helped coordinate the study. Helpful comments on 

this report were provided by reviewers from USGS (Elena 

Nilsen, Jennifer Morace, Don Wilkison, Greg Fuhrer) and 

Clean Water Services (Jan Miller, Bob Baumgartner, Rajeev 

Kapur).

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Publishing support provided by the U.S. Geological Survey

Publishing Network, Tacoma Publishing Service Center

For more information concerning the research in this report, contact the

 Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Rounds and others— Reconnaissance of Pharmaceutical Chemicals in Urban Streams of the Tualatin River Basin, Oregon, 2002—Scientific Investigations Report 2009–5119