U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations 

Report 2008–5208

Prepared as part of the 

National Water-Quality Assessment Program 

Source Water-Quality Assessment

Anthropogenic Organic Compounds in Source Water of 

Nine Community Water Systems that Withdraw from 

Streams, 2002–05
Front cover photographs: The Truckee River in Nevada (upper photograph by Gregory Delzer, U.S. Geological Survey) and 

the Washington Aqueduct on the Potomac River near Washington, D.C. (lower photograph by 

Eric Vance, U.S. Environmental Protection Agency).

Back cover photograph: The Washington Aqueduct (photograph courtesy of the Washington Aqueduct).
Anthropogenic Organic Compounds in 

Source Water of Nine Community Water 

Systems that Withdraw from Streams, 

2002–05

By James A. Kingsbury, Gregory C. Delzer, and Jessica A. Hopple

Prepared as part of the 

National Water-Quality Assessment Program

Source Water-Quality Assessment

Scientific Investigations Report 2008–5208

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

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Although this report is in the public domain, permission must be secured from the individual copyright owners to 

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Suggested citation:

Kingsbury, J.A., Delzer, G.C., and Hopple, J.A., 2008, Anthropogenic organic compounds in source water of nine 

community water systems that withdraw from streams, 2002–05: U.S. Geological Survey Scientific Investigations 

Report 2008–5208, 66 p.
iii

FOREWORD

The U.S. Geological Survey (USGS) is committed to providing the Nation with credible scientific 

information that helps to enhance and protect the overall quality of life and that facilitates effective 

management of water, biological, energy, and mineral resources (http://www.usgs.gov/). Information on the Nation’s water resources is critical to ensuring long-term availability of water that is safe 

for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population 

growth and increasing demands for water make the availability of that water, now measured in 

terms of quantity and quality, even more essential to the long-term sustainability of our communities 

and ecosystems.

The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to 

support national, regional, State, and local information needs and decisions related to water-quality 

management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: 

What is the condition of our Nation’s streams and ground water? How are conditions changing 

over time? How do natural features and human activities affect the quality of streams and ground 

water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide 

science-based insights for current and emerging water issues and priorities. From 1991–2001, the 

NAWQA Program completed interdisciplinary assessments and established a baseline understanding 

of water-quality conditions in 51 of the Nation’s river basins and aquifers, referred to as Study Units 

(http://water.usgs.gov/nawqa/studyu.html).

Multiple national and regional assessments are ongoing in the second decade (2001–2012) of 

the NAWQA Program as 42 of the 51 Study Units are reassessed. These assessments extend the 

findings in the Study Units by determining status and trends at sites that have been consistently 

monitored for more than a decade, and filling critical gaps in characterizing the quality of surface 

water and ground water. For example, increased emphasis has been placed on assessing the quality 

of source water and finished water associated with many of the Nation’s largest community water 

systems. During the second decade, NAWQA is addressing five national priority topics that build 

an understanding of how natural features and human activities affect water quality, and establish 

links between sources of contaminants, the transport of those contaminants through the hydrologic 

system, and the potential effects of contaminants on humans and aquatic ecosystems. Included are 

topics on the fate of agricultural chemicals, effects of urbanization on stream ecosystems, bioaccumulation of mercury in stream ecosystems, effects of nutrient enrichment on aquatic ecosystems, 

and transport of contaminants to public-supply wells. These topical studies are conducted in those 

Study Units most affected by these issues; they comprise a set of multi-Study-Unit designs for 

systematic national assessment. In addition, national syntheses of information on pesticides, volatile 

organic compounds (VOCs), nutrients, selected trace elements, and aquatic ecology are continuing.

The USGS aims to disseminate credible, timely, and relevant science information to address practical 

and effective water-resource management and strategies that protect and restore water quality. We 

hope this NAWQA publication will provide you with insights and information to meet your needs, 

and will foster increased citizen awareness and involvement in the protection and restoration of our 

Nation’s waters.

The USGS recognizes that a national assessment by a single program cannot address all waterresource issues of interest. External coordination at all levels is critical for cost-effective management, regulation, and conservation of our Nation’s water resources. The NAWQA Program, therefore, 

depends on advice and information from other agencies—Federal, State, regional, interstate, Tribal, 

and local—as well as nongovernmental organizations, industry, academia, and other stakeholder 

groups. Your assistance and suggestions are greatly appreciated.

 Matthew C. Larsen 

Associate Director for Water
iv

Contents

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

Introduction.....................................................................................................................................................2

Purpose and Scope ..............................................................................................................................2

Acknowledgments................................................................................................................................3

Study Design and Methods..........................................................................................................................3

Characteristics of Stream Sites and Community Water Systems ................................................3

Compounds Monitored ........................................................................................................................7

Sample Collection and Protocols.......................................................................................................7

Analytical Methods...............................................................................................................................7

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

Human-Health Benchmarks used in a Screening-Level Assessment.......................................11

Annual Mean Concentration Calculations .....................................................................................12

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 ............................12

Commonly Detected Compounds.....................................................................................................12

Comparison to Human-Health Benchmarks...................................................................................19

Mixtures of Compounds.....................................................................................................................22

Factors that May Affect Source-Water Quality.............................................................................22

Land Use......................................................................................................................................23

Wastewater Discharge.............................................................................................................25

Streamflow..................................................................................................................................25

Seasonal Variability...................................................................................................................27

Comparisons of Selected Organic Compounds in Source Water and Finished Water 

Sampled in 2004 and 2005 .............................................................................................................29

Commonly Detected Compounds.....................................................................................................30

Compounds Detected More Commonly in Source Water than in Finished Water .........30

Compounds Detected More Commonly in Finished Water than in Source Water .........32

Changes in Concentration.................................................................................................................32

Comparison to Human-Health Benchmarks...................................................................................34

Mixtures of Compounds.....................................................................................................................37

Summary and Conclusions.........................................................................................................................38

References....................................................................................................................................................40

Appendixes ...................................................................................................................................................45

Appendix 1. Summary statistics and human-health benchmarks for anthropogenic

organic compounds analyzed in source-water samples collected during the

first phase of sampling, October 2002–March 2004 ........................................................46

Appendix 2. Summary statistics and human-health benchmarks for anthropogenic 

organic compounds detected in source- and finished-water samples collected 

during the second phase of sampling, June 2004–August 2005....................................59
v

Figures

1. Map showing samples were collected from nine streams and eight 

community water systems throughout the United States during 2002–05..........................4

2–18. Graphs showing:

2. Forty-seven of 258 anthropogenic organic compounds were detected 

using no common assessment level in 10 percent or more of sourcewater samples collected at nine community water systems (CWSs) 

during the first phase of sampling, October 2002 through March 2004....................13

3. The herbicides most commonly detected in source-water samples from 

Source Water-Quality Assessment sites collected during the first phase of 

sampling, October 2002–March 2004, correspond to those detected most 

frequently in 156 streams across the Nation sampled by the National WaterQuality Assessment Program (1992–2001).....................................................................18

4. The distributions of concentrations of herbicide degradates were similar 

to or greater than concentrations of parent compounds in source-water 

samples collected from the Neuse, Potomac, and White Rivers during the 

first phase of sampling, October 2002–March 2004.....................................................19

5. Annual mean and single-sample concentrations of regulated anthropogenic organic compounds commonly detected in source-water samples 

collected during the first phase of sampling, October 2002–March 2004................20

6. Annual mean and single-sample concentrations of unregulated anthropogenic organic compounds commonly detected in source-water samples 

collected during the first phase of sampling, October 2002–March 2004................21

7. Mixtures of two or more anthropogenic organic compounds analyzed 

were present in many source-water samples collected during the first 

phase of sampling, October 2002–March 2004.............................................................23

8. The median number of anthropogenic organic compounds and median 

total concentration of all compounds detected in source-water samples 

collected during the first phase of sampling, October 2002–March 2004, 

for each site generally increased as the sum of agricultural and urban 

land use in the contributing watersheds increased....................................................23

9. Atrazine concentrations in source-water samples collected during the 

first phase of sampling, October 2002–March 2004, generally increased 

as the amount of agricultural land use in the contributing watersheds 

increased ............................................................................................................................24

10. Chloroform and hexahydrohexamethylcyclopentabenzopyran were 

detected more commonly in source-water samples from watersheds 

with major wastewater discharges than in samples from watersheds 

without major discharges during the first phase of sampling, 

October 2002–March 2004................................................................................................26

11. The concentrations of selected commonly detected anthropogenic 

organic compounds in source-water samples collected during the 

first phase of sampling, October 2002–March 2004, were related to 

streamflow at some sites, but not at others..................................................................27

12. Total herbicide concentrations in source-water samples collected 

during the first phase of sampling, October 2002–March 2004, 

varied seasonally at most sites .......................................................................................28

13. Seasonal variation in atrazine and simazine concentrations differed 

for samples collected from the Chattahoochee and White Rivers 

during the first phase of sampling, October 2002–March 2004..................................29
vi

14. Many commonly detected anthropogenic organic compounds generally 

had similar detection frequencies in source- and finished-water samples 

collected during the second phase of sampling, June 2004–August 2005 ..............31

15. Concentrations of selected anthropogenic organic compounds in samples 

collected during the second phase of sampling, June 2004–August 2005 ..............34

16. Changes in atrazine concentrations in source water usually were reflected 

in the finished-water quality in samples collected at six sites during the 

second phase of sampling, June 2004–August 2005 ...................................................35

17. During the second phase of sampling, June 2004–August 2005, A, annual 

mean concentrations of commonly detected anthropogenic organic 

compouonds in finished-water samples were less than human-health 

benchmarks; and B, maximum concentrations in single samples from 

each site generally were lower than human-health benchmarks ............................36

18. About one-half of source- and finished-water samples collected during 

the second phase of sampling, June 2004–August 2005, contained 

mixtures of 14 or more compounds ................................................................................38

Tables

1. Characteristics of community water systems and their watersheds included 

in Source Water-Quality Assessments, 2002–05.....................................................................5

2. Water-treatment steps used by the community water systems included in 

this study ........................................................................................................................................6

3. Primary use groups for compounds analyzed for Source Water-Quality 

Assessment studies .....................................................................................................................8

4. Period of sample collection and number of samples at each site for both 

sampling phases of Source Water-Quality Assessments, 2002–05 .....................................9

5. Summary of compounds detected in 5 percent or more of field blanks 

collected for Source Water-Quality Assessment studies, 2002–05 ...................................10

6. Detection frequency by site for commonly detected compounds in sourcewater samples collected during the first phase of sampling, 

October 2002–March 2004.........................................................................................................14

7. Length of time between collection of source- and finished-water samples 

during the second phase of sampling, June 2004–August 2005 .........................................30
vii

Conversion Factors and Datums

Multiply By To obtain

Length

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

Flow rate

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

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

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).

Abbreviations and Acronyms used in this Report

< less than

μg/L micrograms per liter

μm micron

AHTN acetyl hexamethyl tetrahydronaphthalene

BQ benchmark quotient

BQmax ratio of the maximum measured concentration for a compound compared to its 

human-health benchmark

BTEX benzene, toluene, ethylbenzene, and xylenes

CCR Consumer Confidence Report

cis-1,2-DCE cis-1,2-dichloroethene

CWS community water system

DEA deethylatrazine

DEET N,N-diethyl-meta-toluamide

DIA deisopropylatrazine

DWLOC drinking water levels of comparison

E estimated

ESA ethane sulfonic acid

GC/MS gas chromatography/mass spectrometry

HBSL Health-Based Screening Level

HHCB hexahydrohexamethylcyclopentabenzopyran

HPLC/MS high-performance liquid chromatography/mass spectrometry
viii

LRL laboratory reporting level

MCL Maximum Contaminant Level

MTBE methyl tert-butyl ether

NAWQA National Water-Quality Assessment

NWQL National Water Quality Laboratory

OGRL Organic Geochemistry Research Group Laboratory

PAC powdered activated carbon

PAH polynuclear aromatic hydrocarbon

PCE tetrachloroethene; perchloroethene

PVC polyvinyl chloride

QC quality control

SPE solid-phase extraction

SWQA Source Water-Quality Assessment

TCT total chlorotriazines

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VOC volatile organic compound

Definitions

Term Definition

Annual Mean Concentration As used in this report, the annual mean concentration is the average concentration for all samples collected at a site over about a 

12-month period. 

Benchmark Quotient (BQ) Ratio of the concentration of a contaminant to its Maximum Contaminant Level (MCL) value for a regulated compound or to its 

Health-Based Screening Level (HBSL) value for an unregulated 

compound. Annual mean BQs greater than 1 identify concentrations 

of potential human-health concern. BQs greater than 0.1 identify 

compounds that may warrant inclusion in a low-concentration, 

trends-monitoring program. 

BQmax Ratio of the maximum concentration of a contaminant to its MCL or 

HBSL value.

BQmean Ratio of the annual mean concentration of a contaminant to its MCL 

or HBSLvalue. Annual mean concentrations were calculated using 

all samples from a given site and using a value of one-half of the 

laboratory reporting level for samples in which a compound was not 

detected.

Blended Water As used in this report, finished water that has been blended with one 

or more different ground-water sources prior to treatment. Systems 

that blend finished surface water with other surface-water sources 

were avoided.
ix

Term Definition

Concentration of Potential 

Human-Health Concern

As used in this report: (1) for a regulated compound with a U.S. 

Environmental Protection Agency (USEPA) drinking-water standard, a concentration greater than the Maximum Contaminant Level; 

and (2) for an unregulated compound, a concentration greater than 

the Health-Based Screening Level.

Community Water System 

(CWS)

A public water system with 15 or more connections and serving 25 or 

more year-round residents and thus is subject to USEPA and State 

regulations enforcing the Safe Drinking Water Act. A CWS serves a 

residential population, such as a municipality, mobile home park, or 

nursing home.

Drinking-Water Guideline As used in this report, a threshold concentration that has no regulatory 

status, but is issued in an advisory capacity by the USEPA or State 

agencies.

Drinking-Water Standard As used in this report, a threshold concentration that is legally enforceable (such as MCLs) by the USEPA or State agencies.

Finished Water Water is “finished” when it has passed through all the processes in a 

water-treatment plant and is ready to be delivered to consumers.

Health-Based Screening Level 

(HBSL)

Benchmark concentrations of contaminants in water that may be of 

potential concern for human health, if exceeded. HBSLs are nonenforceable benchmarks that were developed by the USGS in collaboration with USEPA, New Jersey Department of Environmental 

Protection, and Oregon Health & Science University using USEPA 

methodologies for establishing drinking-water guidelines and the 

most current USEPA peer-reviewed publicly available human-health 

toxicity information.

Human-Health Benchmarks As used in this report, these include USEPA MCL values and HBSL 

values. 

Maximum Contaminant Level 

(MCL)

USEPA drinking-water standard that is legally enforceable, and that 

sets the maximum permissible level of a contaminant in water that is 

delivered to any user of a public water system.

Quench Stop a chemical reaction; in this report quench refers to the addition of 

ascorbic acid to scavenge free chlorine in samples.

Regulated Compound As used in this report, a compound for which a Federal drinking-water 

standard has been established.

Source Water Source water is the raw (ambient) water collected at a surface-water 

intake prior to water treatment used to produce finished water.

Unregulated Compound As used in this report, a compound for which no Federal drinkingwater standard has been established. Note that a compound that 

is unregulated by USEPA in drinking water under the Safe Drinking Water Act may be regulated in other contexts and under other 

statutes.

Anthropogenic Organic Compounds in Source Water of 

Nine Community Water Systems that Withdraw Water 

from Streams, 2002–05

By James A. Kingsbury, Gregory C. Delzer, and Jessica A. Hopple

Abstract

Source water, herein defined as stream water collected at 

a water-system intake prior to water treatment, was sampled at 

nine community water systems, ranging in size from a system 

serving about 3,000 people to one that serves about 2 million 

people. As many as 17 source-water samples were collected 

at each site over about a 12-month period between 2002 and 

2004 for analysis of 258 anthropogenic organic compounds. 

Most of these compounds are unregulated in drinking water, 

and the compounds analyzed include pesticides and selected 

pesticide degradates, gasoline hydrocarbons, personal-care 

and domestic-use compounds, and solvents. The laboratory 

analytical methods used in this study have relatively low 

detection levels—commonly 100 to 1,000 times lower than 

State and Federal standards and guidelines for protecting water 

quality. Detections, therefore, do not necessarily indicate a 

concern to human health but rather help to identify emerging 

issues and to track changes in occurrence and concentrations 

over time.

About one-half (134) of the compounds were detected at 

least once in source-water samples. Forty-seven compounds 

were detected commonly (in 10 percent or more of the 

samples), and six compounds (chloroform, atrazine, simazine, 

metolachlor, deethylatrazine, and hexahydrohexamethylcyclopentabenzopyran (HHCB) were detected in more than 

one-half of the samples. Chloroform was the most commonly 

detected compound—in every sample (year round) at five 

sites. Findings for chloroform and the fragrances HHCB and 

acetyl hexamethyl tetrahydronaphthalene (AHTN) indicate 

an association between occurrence and the presence of large 

upstream wastewater discharges in the watersheds. The 

herbicides atrazine, simazine, and metolachlor also were 

among the most commonly detected compounds. Degradates 

of these herbicides, as well as those of a few other commonly 

occurring herbicides, generally were detected at concentrations similar to or greater than concentrations of the parent 

compound. Samples typically contained mixtures of two or 

more compounds. The total number of compounds and their 

total concentration in samples generally increased with the 

amount of urban and agricultural land use in a watershed.

Annual mean concentrations of all compounds were less 

than human-health benchmarks. Single-sample concentrations of anthropogenic organic compounds in source water 

generally were less than 0.1 microgram per liter and less than 

established human-health benchmarks. Human-health benchmarks used for comparison were U.S. Environmental Protection Agency (USEPA) Maximum Contaminant Levels (MCLs) 

for regulated compounds and U.S. Geological Survey HealthBased Screening Levels for unregulated compounds. About 

one-half of all detected compounds do not have human-health 

benchmarks or adequate toxicity information for evaluating 

results in a human-health context.

During a second sampling phase (2004–05), source 

water and finished water (water that has passed through all the 

treatment processes but prior to distribution) were sampled at 

eight of the nine community water systems. Water-treatment 

processes differ among the systems. Specifically, treatment 

at five of the systems is conventional, typically including 

steps of coagulation, flocculation, sedimentation, filtration, 

and disinfection. One water system uses slow sand filtration 

and disinfection, a second system uses ozone as a preliminary 

treatment step to conventional treatment, and a third system is 

a direct filtration treatment plant that uses many of the steps 

employed in conventional treatment. Most of these treatment 

steps are not designed specifically to remove the compounds 

monitored in this study.

About two-thirds of the compounds detected commonly 

in source water were detected at similar frequencies in 

finished water. Although the water-treatment steps differ 

somewhat among the eight water systems, the amount of 

change in concentration of the compounds from source- to 

finished-water samples generally did not differ systematically at one or among the water systems for compounds with 

similar detection frequencies in source and finished water. 

Additionally, changes in concentration over time in source 

water of some compounds, for example seasonal changes in 

atrazine concentrations, usually were reflected in the associated finished water.

Some compounds detected in source water were 

removed or transformed during treatment and, therefore, 

were not detected in finished water. These included aromatic 
2 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

hydrocarbons with one or more methyl groups, 3,4-dichloroaniline (diuron degradate), the organophosphate insecticides (diazinon and malathion), and fipronil. On the basis of 

results for matrix spikes, decreases in concentration of these 

compounds or nondetections in finished water likely were 

due to degradation or transformation as a result of chlorine 

disinfection.

The annual mean concentration of all compounds 

detected in finished water were less than established humanhealth benchmarks, and concentrations of most compounds 

were several orders of magnitude less than human-health 

benchmarks. With the exception of one detection of atrazine at 

one site, maximum measured concentrations of all commonly 

detected compounds in finished water were less than established human-health benchmarks. The annual mean concentration of atrazine at this site was 0.72 microgram per liter, 

which is less than the MCL of 3 micrograms per liter. Most 

source- and finished-water samples contained mixtures of 2 

or more compounds, and more than one-half of both sourceand finished-water samples contained mixtures of 14 or more 

compounds. Degradates of commonly detected herbicides 

often were present at a concentration similar to or greater 

than of that the parent compound in both source and finished 

water and contributed to the number of compounds detected in 

mixtures.

Introduction

The occurrence of anthropogenic organic compounds 

in the surface waters of the Nation has been described in a 

growing number of studies over the past two decades (for 

example, Gilliom and others, 1985, 2006; Westrick, 1990; 

Kolpin and others, 2002). Some of these studies have focused 

on ambient streams in different land-use settings, whereas 

others have focused on streams specifically selected because 

of a high probability for finding specific types of contaminants. Collectively, findings from these studies point to the 

need for continued monitoring and evaluation of organic 

compounds found in sources of drinking water, referred to as 

source waters, using nationally consistent analytical methods 

and assessment techniques.

Recent studies also have found that many organic 

compounds present in source waters are not removed 

during conventional water treatment and are still detectable 

in finished water (Ternes and others, 2002; Coupe and 

Blomquist, 2004; Stackelberg and others, 2004; Westerhoff 

and others, 2005; Jiang and Adams, 2006). Such findings highlight the need to characterize the occurrence of compounds not 

typically monitored in source waters and associated finished 

waters.

During 1992–2001, the U.S. Geological Survey’s (USGS) 

National Water-Quality Assessment (NAWQA) Program 

assessed the quality of ambient surface- and ground-water 

resources in 51 major river basins and aquifer systems across 

the Nation (http://water.usgs.gov/nawqa/studies/study_units.

html). Beginning in 2002, NAWQA initiated “Source WaterQuality Assessments” (SWQAs) at selected community water 

systems (CWSs) across the United States (Delzer and Hamilton, 2007). The long-term goal is to complete SWQAs at about 

30 CWSs that withdraw water from streams by 2012. The 

primary emphasis of SWQAs is to characterize the occurrence 

of a large number of anthropogenic organic compounds that 

are predominantly unregulated by the U.S. Environmental 

Protection Agency (USEPA) in sources of drinking water 

(stream water collected at a surface-water intake prior to water 

treatment). In addition, SWQAs are intended to provide a 

preliminary, broad-based assessment of selected compounds 

found in source water and the associated finished water (water 

that has passed through treatment processes but prior to distribution). These studies contribute to specific science goals and 

priorities of the USGS, which, in part, include assessment of 

environmental risk to public health and the quality of water 

used for drinking water, as important aspects of accounting 

for the freshwater resources of the Nation (U.S. Geological 

Survey, 2007).

The laboratory analytical methods used in SWQA studies 

have relatively low detection levels—commonly 100 to 

1,000 times lower than State and Federal standards and guidelines for protecting water quality. Detections, therefore, do not 

necessarily indicate a concern to human health but rather help 

to identify emerging issues and to track changes in occurrence and concentrations over time. SWQAs complement 

existing drinking-water monitoring required by Federal, State, 

and local programs, which focus primarily on post-treatment 

compliance monitoring of contaminants regulated by USEPA 

in drinking water to meet requirements of the Safe Drinking 

Water Act. Most of the compounds analyzed in these studies 

are not included in other source-water and finished-water 

monitoring programs such as the Unregulated Contaminant 

Monitoring Program (U.S. Environmental Protection Agency, 

2007) and the U.S. Department of Agriculture’s Pesticide Data 

Program (U.S. Department of Agriculture, 2008).

Purpose and Scope

The primary purpose of this report is to characterize 

the occurrence of 258 anthropogenic organic compounds in 

source water of nine CWSs that withdraw water from streams, 

which are the first nine CWSs at which SWQAs studies have 

been conducted. Source-water samples were collected during 

2002–04 and were analyzed for compounds that included 

pesticides and pesticide degradates, gasoline hydrocarbons, 

personal-care and domestic-use compounds, and solvents. 

The report describes (1) the occurrence of compounds in 

source water and highlights those that occur most commonly; 

(2) the comparison of concentrations of detected compounds 

to available human-health benchmarks; and (3) the characterization the number of compounds co-occurring in source 

water as mixtures. Although this study was not designed to 
Study Design and Methods 3

examine specific sources and (or) factors causing and affecting the occurrence and concentrations of compounds in source 

waters, additional perspective is provided by highlighting 

general patterns and associations as appropriate, including 

those related to land use, wastewater discharge, streamflow, 

and seasonality.

A secondary purpose of this report is to provide 

comparisons of selected compounds in source water with 

their occurrence in finished water. Samples of both source 

and finished water were collected during 2004–05 at eight 

of the nine CWSs. Monitoring during this period generally 

used analytical methods that included compounds found to 

occur most commonly in source water during the 2002–04 

monitoring. The sampling design and resulting comparisons 

were not intended to characterize treatment efficacy, but to 

provide a preliminary indication of the potential importance 

of compounds found in source water to the quality of finished 

water prior to distribution. In general, the types of treatment 

used by the CWSs that were sampled were not specifically 

designed to remove most of the organic compounds monitored.

A screening-level assessment of the potential significance 

of detected compounds in source and finished waters to human 

health was made, when possible, by comparing measured 

concentrations to human-health benchmarks. Specifically, 

concentrations of compounds regulated for drinking water 

were compared to USEPA Maximum Contaminant Levels 

(MCLs), and concentrations of unregulated compounds 

for which USEPA has published toxicity information were 

compared to USGS Health-Based Screening Levels (HBSLs) 

developed by the USGS in collaboration with USEPA, New 

Jersey Department of Environmental Protection, and Oregon 

Health & Science University (Toccalino and others, 2003). 

About one-half of the compounds analyzed in this study do not 

have sufficient toxicity information and, therefore, do not have 

human-health benchmarks. The screening-level assessment 

provides an initial perspective on the potential importance of 

anthropogenic organic compounds detected. The screeninglevel assessment is not a substitute for comprehensive risk 

assessment, which includes many more factors, such as additional avenues of exposure.

Acknowledgments

This study could not have been completed without the 

cooperation of the personnel at each of the CWSs sampled, 

and their assistance is gratefully acknowledged. This report 

benefited from technical review and suggestions provided by 

USGS employees John Zogorski, Robert Gilliom, William 

Wilber, Pixie Hamilton, Michael Focazio, Donna Myers, 

Michael Woodside, Gary Rowe, Michael Yurewicz, Charles 

Crawford, and Patricia Toccalino, and USEPA employee 

Susan Glassmeyer. In addition, the authors would like to 

acknowledge Thomas Carpenter, Veronica Blette, Meredith 

Benedict, Thomas Grubbs, Steve Wendelken, Michael Muse, 

Roy Simon, and Shanika Whitehurst (USEPA Office of 

Groundwater and Drinking Water); Marietta Echeverria, Elizabeth Behl, Kevin Costello, Paula Deschamp, Catherine Eiden, 

and Jack Housenger (USEPA Office of Pesticide Programs); 

Heidi Bethel and Hend Galal-Gorchev (USEPA Office of 

Water); Alan Roberson (American Water Works Association); 

Erica Brown (Association of Metropolitan Water Agencies); 

Darrell Osterhoudt (Association of State Drinking Water 

Administrators); and Paul Hendley (Syngenta Crop Protection, 

Inc.) for their constructive external review comments.

Study Design and Methods

CWSs selected for SWQA monitoring fit several criteria. 

Specifically, stream intakes were located in NAWQA Study 

Units where SWQA data can be compared to other NAWQA 

data collected during 1992 through 2001 from streams across 

the country. CWS intakes were located on free-flowing 

reaches of streams, and systems withdrawing from large reservoirs with extensive residence times (on the order of several 

years) were excluded. Selected CWSs ideally were singlesource systems, with little or no blending of other source 

waters, and CWSs that were relatively large were preferred. 

The type of water treatment, prior monitoring results, including those for compliance monitoring, and the type of land 

use in the watershed were not considerations in the selection 

process.

Characteristics of Stream Sites and Community 

Water Systems

Locations of the CWSs included in this study are shown 

in figure 1. Eight of the nine CWSs are categorized as “large” 

or “very large” water systems, defined as providing water 

to more than 10,000 and 100,000 people, respectively (U.S. 

Environmental Protection Agency, 2006a). The contributing 

watersheds for the nine stream sites range from about 1 to 

11,500 square miles (mi2), with most (seven) between about 

480 and 2,500 mi2 (table 1). The smallest CWS is on Running 

Gutter Brook, serving 3,300 people, and the intake is located 

in a small flow-through reservoir that has a residence time of 

less than 2 hours.

Forested land accounts for most of the land use in seven 

of the nine watersheds, ranging from about 55 to 80 percent of 

the land area. Agricultural land, predominantly fields of row 

crops and pasture, makes up the largest portion of land use in 

the remaining two watersheds (White and Elm Fork Trinity 

Rivers). In the White River watershed, most of the agricultural 

land use (85 percent) is row crop, whereas in the Elm Fork 

Trinity watershed, pasture land accounts for about 75 percent 

of the agricultural land use. Urban land makes up less than 

10 percent of the area of most watersheds, with the largest 

amount in the Neuse River watershed (14 percent). Urban land 
Figure 1. Samples were collected from nine streams and eight community water systems throughout the United States during 2002–05.

Base from U.S. Geological Survey digital data, 1996, 

1:2,000,000

Albers Equal-Area Conic projection

Standard parallels 29°30′ N and 45°5′ N, central meridian 96° W

North American Datum of 1983

Clackamas River

Elm Fork Trinity River

Truckee River Cache la Poudre River

White River

Chattahoochee 

River

Clackamas River

Elm Fork Trinity River

Truckee River Cache la Poudre River

Chattahoochee 

River

0 200 400 600 800 MILES

0 200 400 600 800 KILOMETERS

Only source-water samples collected

Source- and finished-water samples collected

EXPLANATION

Running Gutter 

Brook

Potomac

 River

Neuse River

White River

4 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

use represents a small percentage of the land use in the watershed, but several sites are located in urban settings. “Other” 

land use, generally accounting for less than 30 percent of the 

watershed land uses, includes grassland, shrub land, and open 

water (table 1).

For the purposes of this study, dominant land-use categories associated with each watershed (table 1) were characterized using the NAWQA classification scheme (Gilliom and 

others, 2006). For example, the four streams classified as 

“undeveloped” drain less than 25 percent of agricultural land 

and less than 5 percent of urban land (Running Gutter Brook 

and the Cache la Poudre, Truckee, and Clackamas Rivers). 

Three streams classified as “mixed land use” (Chattahoochee, 

Neuse, and Potomac Rivers) drain mixtures, or combinations, 

of two or more land uses and do not meet specific criteria 

for individual agricultural, urban, or undeveloped land use 

described in Gilliom and others (2006). Two streams classified as “agricultural” (Elm Fork Trinity and White Rivers) 

drain more than 50 percent agricultural land and less than 

5 percent of urban land. Although the White River watershed 

includes 8 percent urban land, in this report it was classified as agricultural rather than mixed land use because of 

the predominance of cultivated agricultural land use. For 

comparison, NAWQA land-use classifications for 1,679 public 

water supply intakes that withdraw water from streams in the 

United States indicated that 55 percent of the intakes withdraw 

water from streams that drain watersheds with predominantly 

undeveloped land, 32 percent from streams with mixed land 

use, 12 percent from streams with agricultural land use, and 

1 percent from streams with urban land use (Gilliom and 

others, 2006).

The water-treatment processes used by the CWSs 

included in this study are largely conventional, typically 

consisting of the following steps: coagulation, flocculation, 

sedimentation, filtration, and chlorine or sodium hypochlorite disinfection (table 2). Additional treatment steps, such 

as chemical oxidation and pH adjustment are used at several 

of the CWSs. Powdered activated carbon (PAC) is used 
Table 1. Characteristics of community water systems and their watersheds included in Source Water-Quality Assessments, 2002–05.

[Sites are arranged top to bottom by increasing agricultural land use. CWS, community water system; Mgal/d, million gallons per day; NA, not applicable; <, less than]

Source Water-Quality Assessment site

Population 

served by 

CWS 

(in 2000)1

Daily 

average 

water use 

(Mgal/d)

Drainage 

area upstream 

from intake 

(square miles)

Average daily 

municipal 

wastewater permitted 

discharge for 

major dischargers2

(Mgal/d)

Land use3 (in perc

Agriculture Urban Forest 

Cache la Poudre River, Colorado 132,000 27.5 484 NA <1 <1 77 Truckee River, Nevada 300,000 49 1,050 NA <1 4 56 Clackamas River, Oregon 100,000 9.5 937 NA 7 3 82 Running Gutter Brook, Massachusetts 3,300 0.24 1 NA 10 2 82 Chattahoochee River, Georgia 750,000 65 1,455 52 12 12 71 Neuse River, North Carolina 11,900 2.7 1,207 103 16 14 63 Potomac River, Maryland 1,000,000 183 11,464 150 34 4 60 Elm Fork Trinity River, Texas 2,000,000 154 2,459 57 54 4 13 White River, Indiana 865,000 15.5 1,168 61 86 8 4 

1Population served data provided by community water systems.2Major discharges are permitted to discharge 1 Mgal/d or more (U.S. Environmental Protection Agency, 2006b). Discharge is sum of daily average permitted discharge for all 

plants in watershed upstream from intake.

3Land-use data are based on 1992 National Land Cover Data (Vogelmann and others, 2001).
Table 2. Water-treatment steps used by the community water systems included in this study.

[PAC, powdered activated carbon; NaOCl, sodium hypochlorite]

Source Water-Quality Assessment site Water-treatment steps used

Cache la Poudre River, Colorado (1) pre-sedimentation and screening, (2) rapid mix while coagulant (aluminum sulfate) is 

added, (3) flocculation (polymer is added) and sedimentation, (4) solids drawn off, (5) filtration through anthracite and sand, (6) clear well storage, (7) disinfection/chemical addition 

(chlorine, fluoride, lime, and chlorine dioxide), (8) storage in underground reservoirs, and 

(9) distribution.

Chattahoochee River, Georgia (1) screening, (2) coagulation (aluminum sulfate), (3) predisinfection (NaOCl), (4) flocculation 

and sedimentation, (5) filtration through anthracite coal, sand and coarse gravel using dual 

media filters, (6) post-chemical addition (fluoride, phosphoric acid, lime and more sodium 

hypochlorite), (7) clear well storage, and (8) distribution.

Clackamas River, Oregon (1) screening, (2) disinfection (chlorine), (3) coagulation (aluminum chlorhydrate), (4) flocculation and sedimentation, (5) addition of filter aid (polymer), (6) filtration through anthracite 

and sand, (7) post-disinfection/chemical addition (chlorine), soda ash, pH adjustment, and 

occasionally PAC, (8) clear well and reservoir storage, and (9) distribution.

Elm Fork Trinity River, Texas (1) ozonation, (2) coagulation (ferric sulfate and polymer), (3) flocculation, (4) disinfection/

chemical addition (chlorine, ammonia, fluoride, lime), (5) sedimentation, (6) filtration through 

anthracite carbon, (7) clear well storage, and (8) distribution.

Neuse River, North Carolina (1) screening, (2) pre-oxidation with potassium permanganate, (3) coagulation (aluminum 

sulfate), (4) flocculation and sedimentation, (5) disinfection (chlorine), (6) filtration using 

anthracite and sand, (7) disinfection (chlorine), (8) clear well storage, (9) addition of ammonia 

and fluoride and occasionally PAC, and (10) distribution.

Potomac River, Maryland (1) screening, (2) pre-sedimentation, (3) coagulation (aluminum sulfate), (4) flocculation and 

sedimentation, (5) filtration through anthracite, sand, and coarse gravel using gravity filters, 

(6) disinfection/chemical addition (chlorine, ammonia, fluoride, lime, and occasionally PAC), 

and (7) distribution.

Running Gutter Brook, Massachusetts (1) slow sand filtration-mixed media, and (2) chemical oxidation and disinfection (chlorine), 

(3) occasional blending with ground water, and (4) distribution.

Truckee River, Nevada (1) bar screening, (2) pre-sedimentation, (3) screening, (4) coagulation (polymers) by rapid mixing, (5) flocculation, (6) sedimentation, (7) filtration using anthracite and sand, (8) disinfection (chlorine), (9) addition of soda ash, and (10) distribution.

White River, Indiana (1) bar screening, (2) pretreatment, permanganate and occasionally PAC added, (3) intermittent blending with ground water, (4) coagulation (alum), (5) flocculation and sedimentation, 

(6) disinfection (chlorine), (7) filtration, (8) disinfection/chemical addition (chlorine, ammonia, fluoride), (9) clear well storage, and (10) distribution.

6 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

for seasonal taste- and odor-issues or removal of organic 

compounds at four of the CWSs (table 2). Treatment processes 

at three CWSs are notably different: the CWS on the Clackamas River is a direct filtration plant; the system at Elm Fork 

Trinity River uses ozone as a preliminary treatment step to 

disinfect the water and to oxidize organic compounds; and the 

CWS on Running Gutter Brook uses slow sand filtration and 

disinfection (table 2).
Study Design and Methods 7

Compounds Monitored

Compounds included for monitoring were selected on the 

basis of known or potential human-health concerns, analytical capabilities, and whether the compounds typically are not 

monitored in source and (or) finished water. Some compounds 

without known human-health concerns, such as caffeine, were 

included as potential indicators or surrogates for contaminants 

not monitored. Most of the 258 compounds monitored at all 

sites are not regulated in drinking water and typically are not 

monitored by CWSs; however, 38 compounds do have an 

established USEPA MCL for drinking water and are monitored 

in finished water by CWSs. Several inorganic compounds 

were considered for monitoring but were not included because 

they typically are monitored by CWSs and, thus would not 

have provided new information. Additionally, only compounds 

that could be analyzed using USGS approved analytical 

methods were considered for monitoring.

For the purposes of this report, the compounds were 

grouped into 13 categories on the basis of their primary 

use or source (table 3 and Appendix 1). The number of 

compounds in each of the 13 categories (hereafter termed as 

“use groups”) varies, ranging from 3 to 82. About one-half 

of the compounds analyzed are pesticides, which include 

three use groups— herbicides and degradates, insecticides 

and degradates, and fungicides. About 90 volatile organic 

compounds (VOCs) are categorized in six use groups, including disinfection by-products; fumigant-related compounds; 

gasoline hydrocarbons, oxygenates, and oxygenate degradates; organic synthesis compounds; refrigerants and propellants; and solvents. Pesticides and VOCs have been included 

routinely in data collection by the NAWQA Program since 

its inception (1991); however, most of the compounds in the 

remaining four use groups have not been analyzed previously 

by the NAWQA Program. These use groups include personalcare and domestic-use products, such as triclosan (an antibacterial agent in many hand soaps), detergent metabolites, 

and fragrance compounds; manufacturing additives, such as 

plasticizers and fire retardants; pavement- and combustionderived compounds, which are predominantly polynuclear 

aromatic hydrocarbons (PAHs); and plant- and animal-derived 

biochemicals, such as cholesterol.

Sample Collection and Protocols

Source-water samples were collected at the stream sites 

in two sampling phases, each lasting about a year at each site 

during October 2002 through March 2004 and during June 

2004 through August 2005 (table 4; Carter and others, 2007). 

All source-water samples were collected as close as practical to the drinking-water intake or at an untreated water tap 

and processed following standard USGS sampling protocols 

(Shelton, 1994, 1997). During the first phase, source-water 

samples were collected about monthly (12 to 15 times) at each 

stream site with as many as four additional samples collected 

during high-flow or base-flow conditions when water-quality 

changes might be expected or when higher concentrations 

of some compounds are most likely to occur. As a result, 

a variety of flow conditions were sampled at most sites. 

Monthly samples were analyzed for 258 compounds at all 

sites, but at some sites, samples were analyzed for as many as 

277 organic compounds (table 3). The number of compounds 

analyzed in a given sample varied for samples collected during 

low- and high-flow conditions, or because three additional 

herbicides and 16 additional degradates were analyzed in 

samples from the Neuse, Potomac, and White Rivers during 

the first sampling phase and in samples from the Elm Fork 

Trinity, Neuse, Potomac, and White Rivers during the second 

sampling phase.

During the second phase of sampling, from June 2004 

through August 2005, source- and finished-water samples 

were collected about monthly (6 to 12 times) at eight CWSs 

(table 4; Carter and others, 2007). Because relatively few 

compounds were detected in samples from the Cache la 

Poudre River during the first sampling phase, this site was not 

sampled during the second phase. Relatively few compounds 

were detected in samples from the Truckee River. No samples 

were collected at the Truckee River for pesticide analyses, and 

samples for the analysis of other compounds were collected 

for about 6 months (table 4). The finished-water samples 

were collected following all of the treatment steps, prior to 

the water entering the distribution system. At each CWS, 

time was allowed between collection of source- and finishedwater samples to account for the residence time in the watertreatment plants. Finished-water samples typically contain 

free chlorine, which can degrade organic compounds that may 

be present in the samples. Therefore, a dechlorination reagent 

(ascorbic acid or sodium thiosulfate) and, for certain samples, 

pH buffers were added to finished-water samples during 

sample collection to “quench” free chlorine and stabilize 

samples prior to analyses (Winslow and others, 2001). Thus, 

results of analyses of finished-water samples are considered to 

be representative of the quality of water prior to distribution 

but not necessarily of the quality of water at the tap (delivery 

point). This is because of the water’s additional contact time 

with disinfectants in the distribution system, which may allow 

some compounds to be transformed or degraded, whereas 

others, such as disinfection by-products, may continue to form 

in the distribution system.

Analytical Methods

Samples were analyzed using USGS approved analytical methods at the USGS National Water Quality Laboratory 

(NWQL) in Denver, Colo., including gas chromatography/

mass spectrometry (GC/MS) and high-performance liquid 

chromatography/mass spectrometry (HPLC/MS). Samples 

collected for VOC analyses were chilled upon collection, and 

one sample for the two VOC analytical methods was preserved 

with 1:1 hydrochloric acid. Samples for both VOC analytical 
Table 3. Primary use groups for compounds analyzed for Source Water-Quality Assessment studies.

[BTEX: benzene, toluene, ethylbenzene, and xylenes]

Primary use or source 

group Description Number of compounds analyzed in each group

Disinfection by-products Trihalomethanes, (poly)haloacetic acids and other compounds that are produced 

from the transformation of organic compounds during the disinfection of water 

and wastewater through chlorination, ozonation, or other chemical methods.

4

Fumigant-related compoundsChemicals that may be present in commercial fumigant products, which produce 

a gas, vapor, fumes, or smoke intended to destroy, repel, or control unwanted 

organisms such as insects, bacteria, or rodents. These include fumigant active 

ingredients, as well as their degradates and their manufacturing by-products.

9

Fungicides Pesticides that are used to kill unwanted fungi. 7

Gasoline hydrocarbons, 

oxygenates, and oxygenate degradates

Gasoline hydrocarbons are straight, branched, and (or) cyclic organic compounds 

that are highly volatile, contain only carbon and hydrogen atoms, and are common ingredients in gasoline and other petroleum products. Among these compounds, BTEX compounds are among those present in the highest proportions 

in gasoline. Oxygenates such as methyl tert-butyl ether (MTBE) are compounds 

that contain only carbon, hydrogen, and oxygen atoms and are commonly added 

to gasoline to improve the efficiency of combustion. Oxygenate degradates are 

formed during the production, storage, release, and (or) use of gasoline oxygenates or following their release into the environment.

27

Herbicides and herbicide 

degradates1

Pesticides designed to kill unwanted plants (herbicides) and compounds produced 

from the transformation of the parent herbicide following application (degradates).

82

Insecticides and insecticide 

degradates

Pesticides designed to kill unwanted insects (insecticides) and compounds produced 

from the transformation of the parent insecticide following application (degradates).

51

Manufacturing additives Compounds used in commercial formulations of chemical products in order to improve the effectiveness of the product, including plasticizers (to increase the flexibility of plastics), fire retardants, corrosion inhibitors, and pesticide adjuvants.7

Organic synthesis 

compounds

Chemicals that are used as precursors in the manufacture of other organic compounds. Chloroethylene (vinyl chloride), for example, is an organic synthesis 

compound used to produce polyvinyl chloride (PVC) plastics.

18

Pavement- and 

combustion-derived 

compounds

Organic substances, such as polynuclear aromatic hydrocarbons (PAHs), that are 

derived from either (1) the materials used to construct and seal parking lots and 

other paved surfaces, or (2) the combustion of other non-halogenated organic 

compounds, most commonly gasoline, oil, coal, and other fossil fuels.

5

Personal-care and 

domestic-use products

Compounds that are present in commercial products sold for personal or residential 

use, such as fragrances, pharmaceuticals, insect repellants, dyes, detergents, disinfectants, shampoos, and chemicals used in fire extinguishers.

26

Plant- or animal-derived 

biochemicals

Naturally occurring compounds that are produced by plants or animals, either 

through direct biosynthesis or through the metabolic alteration of compounds 

ingested or taken up from other sources. These compounds are predominantly 

unsaturated solid alcohols of the steroid group naturally occurring in fatty tissues 

of plants and animals and present in animal fecal material.

5

Refrigerants and 

propellants

Volatile compounds that are used for commercial or domestic refrigeration, as blowing agents in the manufacture of packaging and other highly porous materials, 

or for dispensing other substances from spray cans and other aerosol delivery 

devices.

3

Solvents Compounds that are used to dissolve other substances. Two of the more common 

solvents are trichloroethene (TCE) and tetrachloroethene (perchloroethene, PCE).

33

Total number of compounds 277

1

Herbicides and herbicide degradates include 3 herbicides and 16 herbicide degradates monitored at selected sites. A total of 258 compounds were monitored 

at all sites.

8 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Table 4. Period of sample collection and number of samples at each site for both sampling phases of Source Water-Quality 

Assessments, 2002–05.

[NA, not applicable]

Source Water-Quality Assessment site Period of sample collection, 

first phase

Number of 

samples

Period of sample collection, 

second phase

Number of

 samples

Cache la Poudre River, Colorado October 2002 – September 2003 17 NA NA

Chattahoochee River, Georgia October 2002 – December 2003 17 July 2004 – May 2005 13

Clackamas River, Oregon October 2002 – September 2003 18 July 2004 – May 2005 14

Elm Fork Trinity River, Texas December 2002 – November 2003 17 June 2004 – May 2005 15

Neuse River, North Carolina November 2002 – December 2003 17 June 2004 – August 2005 15

Potomac River, Maryland April 2003 – March 2004 12 August 2004 – June 2005 13

Running Gutter Brook, Massachusetts January 2003 – December 2003 17 July 2004 – July 2005 12

Truckee River, Nevada December 2002 – November 2003 17 August 2004 – January 2005 8

White River, Indiana October 2002 – September 2003 17 July 2004 – June 2005 13

Study Design and Methods 9

methods were analyzed by purge and trap GC/MS (Connor 

and others, 1998; Rose and Sandstrom, 2003). Samples for 

analyses of pesticides and other semivolatile compounds were 

filtered in the field through a 0.7-micron (μm) baked glassfiber filter and chilled. These samples were extracted at the 

NWQL on solid-phase extraction (SPE) cartridges to concentrate the analytes from the filtered samples. SPE cartridges 

then were eluted with a solvent, and the extracts were 

analyzed by either GC/MS or HPLC/MS methods (Zaugg and 

others, 1995, 2002; Lindley and others, 1996; Furlong and 

others, 2001; Sandstrom and others, 2001; Madsen and others, 

2003). At a subset of sites, an additional sample was collected 

for the analysis of 3 herbicides and 16 herbicide degradates. 

These samples were analyzed using HPLC/MS by the Organic 

Geochemistry Research Group Laboratory (OGRL), in 

Lawrence, Kansas (Lee and Strahan, 2003).

The analytical methods used at the NWQL and OGRL 

allow for the identification and quantification of compounds 

at low concentrations, in some cases as low as a few parts per 

trillion. Each analytical method has different ranges in sensitivity for its suite of analytes. Thus, the laboratory reporting 

levels (LRLs) for the compounds analyzed for SWQAs span 

four orders of magnitude, from about 0.003 to 6 micrograms 

per liter (μg/L), with a median of 0.06 μg/L. Some reported 

concentrations are qualified with an “E” meaning estimated 

and indicating that the identification of the compound is 

reliable, but the concentration has greater uncertainty than 

unqualified concentrations reported for the same compound. 

These concentrations are estimated for one of several reasons: 

(1) they are less than the lowest calibration standard; (2) the 

sample matrix interfered with measurement of the compound; 

(3) surrogates added to the sample indicated poor performance 

during the analysis; or (4) the compound consistently has poor 

recoveries and concentrations are always reported as estimated.

The sensitivity of the analytical methods differs among 

compounds, which can affect the detection frequencies of 

the compounds analyzed. Those with low reporting levels 

likely will be detected more frequently than those with high 

reporting levels, given equal concentration distributions in 

the environment. To compare detection frequencies between 

compounds, a common assessment level is needed to account 

for the different LRLs. In this report, a common assessment 

level of 0.1 μg/L is used for this purpose. This concentration 

is near the median LRL of 0.06 μg/L for all of the compounds 

analyzed. Analytical results for compounds detected in source 

water are presented both with and without an assessment level. 

When concentrations of individual compounds in source- and 

finished-water samples are compared, no assessment level is 

used, and all concentrations are evaluated, including those 

values reported as estimated.

Quality Assurance

Similar types and numbers of quality-control (QC) 

samples were collected at each of the SWQA stream sites and 

CWSs. These QC samples, including field blanks, replicates, 

and matrix spikes, were evaluated together because sampling 

equipment and cleaning procedures, as well as sample collection and processing, were the same for all sites during both 

phases of sampling. Field blanks consisted of nitrogen-purged 

organic-free water that was processed in the field and laboratory in the same manner as environmental samples and are 

used to characterize the likelihood for positive bias or contamination that may affect sample analytical results. Sourcesolution blanks were analyzed for a subset of field blanks and 

analytical methods to assure the integrity of the water used 

for field blanks. Replicate samples are used to characterize 

the amount of variability associated with sample collection, 
Table 5. Summary of compounds detected in 5 percent or more of field blanks collected for Source Water-Quality 

Assessment studies, 2002–05.

[N, number of field blanks; USGS, U.S. Geological Survey; μg/L, micrograms per liter; DEET, N,N-diethyl-meta-toluamide]

Compound (N)

USGS 

parameter 

code

Number of stream sites 

for which compound was 

removed from all samples 

in data set

Number of detections 

censored at the 

maximum field blank 

concentration

Maximum field 

blank 

concentration, 

(μg/L)

Compounds removed from data set

Benzophenone (45) 62067 9 All data removed 0.09

DEET (45) 62082 9 All data removed .66

Isophorone (45) 34409 9 All data removed .09

para-Nonylphenol (total) (45) 62085 9 All data removed 2.3

Phenol (45) 34466 9 All data removed 2.0

Compounds removed from stream site or censored at highest field blank concentration

Benzene (46) 34030 1 0 0.04

Caffeine (25) 50305 1 28 .01

Toluene (46) 34010 1 148 .05

Tributyl phosphate (45) 62089 2 0 .17

Compounds censored at highest field blank concentration

Acetophenone (45) 62064 0 7 0.49

Acetone (46) 81552 0 39 3.67

Bisphenol A (38) 62069 0 46 1.60

Methyl salicylate (45) 62081 0 34 .07

Phenanthrene (45) 34462 0 26 .04

10 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

processing, and analysis. Matrix spikes provide information 

about recoveries of organic compounds.

Field blanks collected during this study indicated that 14 

of the 258 compounds potentially were affected by contamination that could bias the environmental data (table 5). Data 

for these compounds were removed, or results were censored 

to account for this potential bias as follows. Phenol and 

N,N-diethyl-meta-toluamide (DEET) were detected in about 

50 percent or more of field blanks and were removed from the 

data set due to pervasive contamination in the field blanks. 

Although the field blank data did not identify systematic error 

that affected sample results for these compounds, the quality 

of the data for both compounds was unknown.

Three compounds were removed from the data set 

because of systematic contamination from the “quenching” 

reagents added to finished-water samples (table 5). Most 

field blanks collected during the second phase of sampling 

included the ascorbic acid and buffer that were added to 

finished-water samples to quench the free chlorine. Benzophenone, isophorone, and para-nonylphenol, were detected 

at low concentrations in most of these blanks indicating that 

the “quenching” reagents are a source of contamination for 

the compounds. Follow-up analyses by NWQL confirmed the 

presence of these compounds in the buffer added to samples 

(Mark Sandstrom, U.S. Geological Survey, oral commun., 

2005).

For 9 of the 14 compounds detected in more than 

5 percent of field blanks (table 5), the occurrence of these 

compounds in field blanks was evaluated to determine if 

detections were associated with specific sites. If a compound 

was detected in 50 percent or more of field blanks from a site, 

all of the data for that constituent at that site were removed 

from the data set. If a compound was detected in 5 percent 

or more of field blanks collected at the remaining sites, the 

environmental data for that compound were censored at the 

highest field blank concentration to account for the potential 

bias indicated by field blanks. If a compound was detected in 

less than 5 percent of remaining field blanks after removal of 

field blanks from sites with greater than 50 percent occurrence 

in field blanks, no additional censoring was done.

Twenty other compounds were detected infrequently (less 

than 5 percent) at low concentrations in field blanks (Appendix 1). Most of these compounds were detected at concentrations less than the LRL, and 18 of these compounds were 

detected only once in a field blank. Detection frequencies 

for many of these compounds were higher in environmental 

samples than in field blanks, and the field blank concentrations 

were less than many of the environmental concentrations. Data 
Study Design and Methods 11

for these compounds are included in summary tables because 

the potential for contamination in the environmental samples 

was considered to be low and did not affect the overall interpretation of the study results.

Prior to implementation of the addition of ascorbic acid 

(quenching agent) to finished-water samples during the second 

phase of sampling, NWQL evaluated the effect of this quenching agent and buffer on compound recoveries. Results indicated that recoveries were not affected by the addition of these 

reagents (Mark Sandstrom, U.S. Geological Survey, written 

commun., 2006). Additionally, during the second sampling 

phase, matrix spikes were collected to further characterize 

analytical method performance with the addition of ascorbic 

acid to finished-water samples. Results to date (2008) indicate 

that median spike recoveries generally were within acceptable limits for most compounds that are not always reported 

as estimated concentrations (Valder and others, 2008). Results 

of paired spiked finished-water samples, one with quenching reagents added and the other without, indicate that 

several compounds degrade in the presence of free chlorine 

(Valder and others, 2008). These results highlight the fact that 

additional contact time of finished water in the distribution 

system would affect the concentrations of several compounds 

analyzed in this study. Environmental and selected qualityassurance data for this study are available in Carter and others 

(2007).

concentration or other longer-term concentration statistic; 

HBSLs are benchmark concentrations of compounds in water 

that, if exceeded, may be of potential concern for human 

health. HBSLs are not regulatory standards, are not enforceable, and water systems are not required to monitor for any 

compounds for which HBSLs have been developed. HBSLs 

were developed collaboratively by the USGS, USEPA, New 

Jersey Department of Environmental Protection, and Oregon 

Health & Science University (Toccalino and others, 2003). 

The values were developed using USEPA Office of Water 

methodologies and USEPA toxicity values, so they generally 

are comparable to USEPA drinking-water guideline values 

such as Lifetime Health Advisory levels and Risk-Specific 

Dose Values (Toccalino and others, 2003).

HBSLs, as well as most MCLs, are maximum mean 

contaminant concentrations that are not expected to cause 

adverse health effects over a lifetime (70 years) of exposure 

to finished drinking water (Toccalino, 2007; U.S. Environmental Protection Agency, 2008a). MCLs are applicable 

only to finished-water samples in the regulatory framework; 

however, an assessment of source-water concentrations in 

relation to human-health benchmarks provides an indication 

to water-resource managers and CWSs of potential concerns 

in the absence of the effects of factors such as water treatment 

and distribution. In surface water, contaminant concentrations 

can change substantially over time and have strong seasonal 

patterns. Annual or long-term mean concentrations (determined from multiple samples over a period of time and timeweighted) generally are most appropriate for comparison to 

MCLs or HBSLs because mean concentrations provide a more 

reliable indication of long-term exposure than concentrations 

in individual samples (Toccalino, 2007). In this study, annual 

mean concentrations were compared to human-health benchmarks to assess potential concerns. For these comparisons, 

annual mean benchmark quotient (BQ) values, the ratio of an 

annual mean concentration of a compound to its benchmark, 

were calculated.

Concentrations of compounds in single samples of both 

source water and finished water also were compared to these 

human-health benchmarks as an additional screening-level 

assessment. This comparison identifies compounds with 

concentrations that approached or were greater than benchmarks to aid in assessing their potential significance. A BQ 

value greater than 1.0 represents a concentration greater than 

or equal to a benchmark. A BQ value greater than or equal 

to 0.1 can be used to identify compounds that may warrant 

additional monitoring (Toccalino, Rowe, and Norman, 2006). 

A threshold BQ of 0.1 is consistent with various State and 

Federal practices (for example, see U.S. Environmental 

Protection Agency, 1998a). Monitoring for these contaminants would enable analysis of trends in their occurrence and 

may provide an early indication if concentrations approach 

human-health benchmarks. Also in this report, BQmax is used 

to represent the ratio of the maximum measured concentration 

for a compound compared to its human-health benchmark. All 

BQ values are rounded to two significant figures.

Human-Health Benchmarks used in a 

Screening-Level Assessment

Annual mean concentrations for regulated compounds—

those with USEPA MCLs—were compared to MCLs, and 

annual mean concentrations of unregulated compounds—those 

without USEPA MCLs—were compared to Health-Based 

Screening Levels (HBSLs), when available (Toccalino and 

others, 2003; Toccalino, Norman, and others, 2006). Comparisons to human-health benchmarks are used in this report to 

identify concentrations of potential human-health concern and 

to provide an initial perspective on the potential importance of 

the anthropogenic organic compounds detected.

Thirty-eight of the compounds monitored in this study 

have an established USEPA MCL (U.S. Environmental Protection Agency, 2006c) and 110 have an HBSL (Toccalino, 2007). 

HBSLs have not been developed for the remaining 129 unregulated compounds because of a lack of toxicity information. 

Therefore, the potential human-health significance of these 

compounds cannot be evaluated at this time (Toccalino, Rowe, 

and Norman, 2006).

MCLs are legally enforceable USEPA drinking-water 

standards that set the maximum permissible level of a contaminant in water that is delivered by public water systems (U.S. 

Environmental Protection Agency, 2008a). The permissible 

level, depending on the contaminant, may be defined in terms 

of a single sample concentration or in terms of an annual mean 
12 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

Annual Mean Concentration Calculations

CWSs where surface water is the source of drinking water are required to collect quarterly samples during 

compliance monitoring under the Safe Drinking Water Act 

of 1996. Results of a sample are averaged with the previous three quarterly samples to determine whether running 

average concentrations in finished water are less than MCLs 

(U.S. Environmental Protection Agency, 1998b). In this study, 

annul mean concentrations were calculated for both phases of 

sampling at each site. At most sites, samples were collected 

over about a 12-month period in each phase, but in some 

cases the sampling period was somewhat longer or shorter 

than 12 months (table 4). The minimum number of samples 

collected for calculation of an annual mean concentration was 

eight samples from the CWS on the Truckee River during the 

second sampling phase. Results for all samples were used for 

calculating the annual mean concentration at each site, and a 

value of one-half of the LRL was used for samples in which 

a compound was not detected. This approach represents a 

conservative estimate of the annual mean concentration.

Anthropogenic Organic Compounds in 

Source Water Sampled During 2002–04 

A total of 134 of the 258 anthropogenic organic 

compounds analyzed at all sites were detected in at least 

one source-water sample collected at nine CWSs during the 

first phase of sampling, October 2002 through March 2004. 

A total of 119 compounds were not detected in any sample 

(5 compounds were removed from the data set because of 

data-quality concerns). At least one compound was detected 

from each of the 13 use groups in which the compounds were 

categorized, with the exception of refrigerants and propellants 

(Appendix 1). Results were evaluated with no assessment 

level (all detections) and with an assessment level of 0.1 μg/L 

(fig. 2). Compounds are characterized as commonly occurring 

in this report when they were detected in 10 percent or more of 

samples among all sites combined or in more than 75 percent 

of samples from at least one site using no assessment level. 

By this definition, 47 compounds were detected commonly. 

Of these compounds, chloroform, simazine, atrazine, deethylatrazine, metolachlor, and hexahydrohexamethylcyclopentabenzopyran (HHCB) were detected in more than one-half of 

the source-water samples. The commonly detected compounds 

represented nine of the use groups and did not include the 

fumigant-related, pavement- and combustion-derived, organic 

synthesis, or refrigerants and propellants use groups.

Detection frequencies of most compounds were less 

than 10 percent on the basis of the common assessment level 

of 0.1 μg/L, and only 15 compounds in six of the primary 

use groups had detection frequencies greater than 10 percent 

(fig. 2 and Appendix 1). A few compounds, such as cholesterol, had the same detection frequency with and without the 

application of a common assessment level. These compounds 

have an LRL that is greater than 0.1 μg/L, and all detected 

concentrations were greater than that concentration. At the 

common assessment level, compounds from six of the use 

groups were detected, with herbicides and herbicide degradates being detected most commonly. The smaller detection frequencies that were based on a common assessment 

level compared to using no assessment level illustrate the 

low concentrations at which many of these compounds were 

detected.

Commonly Detected Compounds

 Most of the commonly detected compounds were 

present in samples from several sites, and only three 

compounds—alachlor, acetochlor, and cis-1,2-dichlorothene 

(cis-1,2-DCE)—were not detected at more than two sites 

(table 6). Localized occurrence of these compounds likely 

represents the presence of either a nearby point source, use of 

a compound for a specific purpose (for example, an herbicide that is applied to a specific crop that is grown only in 

one of the watersheds), or ground-water discharge that is 

contaminated from an industrial site or landfill. The fact that 

acetochlor was detected predominantly at one site is related 

to its use as an herbicide for corn cultivation. The occurrence 

of acetochlor was largely limited to samples collected from 

the White River in Indiana, which drains a large amount of 

cultivated land (table 1).

Herbicides and herbicide degradates were among the 

most commonly detected compounds in source-water samples 

collected during the first phase of sampling. Their frequent 

detection is due, in large part, to their widespread use and 

lower reporting levels compared to other compounds (fig. 2 

and Appendix 1). The most commonly detected herbicides—

simazine, atrazine and its degradates (deethylatrazine and 

deisopropylatrazine), metolachlor, prometon, and 2,4–D—

were detected in about 50 percent or more of samples at six 

of the nine sites. Sima-zine, atrazine, deethylatrazine, and 

metolachlor were detected year round in samples from the Elm 

Fork Trinity, Potomac, and White Rivers. The most commonly 

detected herbicides have both agricultural and non-agricultural 

uses. Atrazine and metolachlor are two of the most heavily 

used agricultural herbicides in the country with much of the 

use for corn production; however, both herbicides also are 

used in urban areas (Gilliom and others, 2006). Simazine, 

prometon, and 2,4–D have considerable use for weed control 

in areas not associated with agriculture, such as use on turfgrass, lawns, roadsides, and railroads, and simazine and 2,4–D 

also are used for agriculture (Gilliom and others, 2006). The 

common occurrence of these herbicides in both agricultural 

and non-agricultural settings is, in part, a result of the large 

amounts of agricultural or mixed land use (including some 

urban) that characterizes the contributing watersheds, and 

the relatively large amounts of these herbicides that are used 

(Gilliom and others, 2006).
Figure 2. Forty-seven of 258 anthropogenic organic compounds were detected using no common assessment level in 

10 percent or more of source-water samples collected at nine community water systems (CWSs) during the first phase 

of sampling, October 2002 through March 2004.

cis-1,2-Dichloroethene*

 Perchloroethene*

Carbaryl

Diazinon

Tebuthiuron

Terbuthylazine

Bentazon

Acetochlor

Triclopyr

Alachlor*

MCPA

Diuron

2-Hydroxyatrazine

2,4–D*

Prometon

Metolachlor

Atrazine*

Simazine*

o-Xylene*

m- & p-Xylene*

Benzene*

Toluene*

Benomyl

Bromodichloromethane*

Chloroform*

p-Cresol

3-beta-Coprostanol

beta-Stigmastanol

Cholesterol

Octylphenol monoethoxylate (total)

Triethyl citrate

Nonylphenol diethoxylate (total)

HHCB

Caffeine

AHTN

Triphenyl phosphate

Tri(2-butoxyethyl)phosphate

Tris(dichlorisopropyl)phosphate

Tri(2-chloroethyl)phosphate

Fipronil

3,4-Dichloroaniline

Deisopropylatrazine

Deethylatrazine

tert-Butyl alcohol

1,2,4-Trimethylbenzene

Methyl tert-butyl ether

Tributyl phosphate

Herbicides 

and herbicide 

degradates

Gasoline-related 

compounds

DBPs

Solvents

Insecticides

Fungicide

EXPLANATION

All detections

Detections at concentrations greater than 

 or equal to an assessment level of 

 0.1 microgram per liter

Personal care and

domestic use

Manufacturing 

additves

Plant or animal

biochemicals

DETECTION FREQUENCY, IN PERCENT

0 20 40 60 80 100

Note: If bar is all light green, the compound was 

not detected at a concentration equal to or greater 

than 0.1 microgram per liter. Conversely, if bar is all 

dark green, the compound was not detected at a 

concentration less than 0.1 microgram per liter.

* Regulated compound

Disinfection by-product

2-methyl-4-chlorophenoxyacetic acid

Hexahydrohexamethylcyclopentabenzopyran

Acetyl hexamethyl tetrahydronaphthalene

DBP

MCPA

HHCB

AHTN

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 13
Table 6. Detection frequency by site for commonly detected compounds in source-water samples collected during the first phase of sampling, Octo

2004.—Continued[Commonly detected compounds were in 10 percent or more of samples. Stream sites are arranged from left to right by increasing agricultural land use. Compounds in each primdescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some commethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; ND, not detected; --, no data, data removed]

Anthropogenic 

organic 

compound

Overall 

detection 

frequency, 

in percent

Cache la 

Poudre River, 

Colorado

(N=17)

Truckee 

River, 

Nevada

(N=17)

Clackamas 

River, 

Oregon

(N=17)

Running Gutter 

Brook, Massachusetts

(N=16)

Chattahoochee 

River, 

Georgia

(N=17)

Neuse River, 

North 

Carolina

(N=17)

Potomac River, 

Maryland

(N=12)

T

Disinfection by-products

Chloroform 69 ND 6 39 100 94 100 100 Bromodichloromethane 20 ND ND 6 27 18 6 17 

Fungicides

Benomyl 12 ND ND ND ND 53 25 8 

Gasoline hydrocarbons, oxygenates, and oxygenate degradates

Methyl tert-butyl ether 

(MTBE)

36 ND ND ND 47 41 76 67 

Benzene 31 24 12 67 27 -- 47 17 Toluene 18 ND 12 56 ND 29 18 17 m- and p-Xylene 13 ND 6 56 ND 12 6 17 1,2,4-Trimethylbenzene 12 ND 6 56 ND 12 6 8 tert-Butyl alcohol 11 ND ND ND ND 13 35 ND o-Xylene 11 ND 6 56 ND 6 6 8 

Herbicides and herbicide degradates

Simazine 67 ND ND 53 63 100 100 100 Atrazine 64 ND 6 29 75 100 76 100 Deethylatrazine 52 ND 18 18 31 47 71 100 Metolachlor 51 ND ND 18 13 41 100 100 Deisopropylatrazine 49 ND ND ND 82 53 38 8 Prometon 49 ND ND 6 ND 94 100 92 2,4–D 43 ND ND 6 ND 87 69 58 2-Hydroxyatrazine 40 ND ND ND ND 47 50 92 3,4-Dichloroaniline 40 ND ND ND ND 94 88 17 Diuron 30 ND 6 47 ND 40 38 25 MCPA 21 ND ND ND ND 67 25 33 Alachlor 15 ND ND ND ND ND ND ND 
Table 6. Detection frequency by site for commonly detected compounds in source-water samples collected during the first phase of sampling, Octo

2004.—Continued[Commonly detected compounds were in 10 percent or more of samples. Stream sites are arranged from left to right by increasing agricultural land use. Compounds in each primdescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some commethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; ND, not detected; --, no data, data removed]

Anthropogenic 

organic 

compound

Overall 

detection 

frequency, 

in percent

Cache la 

Poudre River, 

Colorado

(N=17)

Truckee 

River, 

Nevada

(N=17)

Clackamas 

River, 

Oregon

(N=17)

Running Gutter 

Brook, Massachusetts

(N=16)

Chattahoochee 

River, 

Georgia

(N=17)

Neuse River, 

North 

Carolina

(N=17)

Potomac River, 

Maryland

(N=12)

T

Herbicides and herbicide degradates—Continued

Acetochlor 12 ND ND ND ND ND ND 17 

Bentazon 12 ND ND ND ND ND 6 ND Terbuthylazine 12 ND ND ND ND 6 47 ND Triclopyr 12 ND ND ND ND 40 6 17 Tebuthiuron 11 ND ND ND ND 18 12 ND 

Insecticides and insecticide degradates

Diazinon 39 ND ND 12 ND 59 82 33 Fipronil 29 ND ND ND ND 59 88 17 Carbaryl 15 ND ND 18 ND 47 31 33 

Manufacturing additives

Tri(2-chloroethyl)phosphate 34 ND 6 ND 7 56 71 33 Tris(dichlorisopropyl)-

phosphate

26 ND ND ND ND 44 53 25 

Tributyl phosphate 20 ND ND 6 -- 31 35 -- Tri(2-butoxyethyl)phosphate 19 ND ND ND ND 38 29 17 Triphenyl phosphate 16 6 ND 6 ND 38 24 17 

Personal-care and domestic-use products

HHCB 53 6 24 ND 27 81 88 67 AHTN 39 ND ND ND 20 75 82 25 Caffeine 31 6 18 6 12 50 41 -- 4-Nonylphenol diethoxylate (total) 14 6 ND ND 13 25 29 8 Triethyl citrate (ethyl 

citrate)

14 ND ND ND ND 19 24 8 

4-Octylphenol monoethoxylate (total) 11 6 ND ND 13 25 18 17 
Table 6. Detection frequency by site for commonly detected compounds in source-water samples collected during the first phase of sampling, Octo

2004.—Continued[Commonly detected compounds were in 10 percent or more of samples. Stream sites are arranged from left to right by increasing agricultural land use. Compounds in each primdescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some commethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; ND, not detected; --, no data, data removed]

Anthropogenic 

organic 

compound

Overall 

detection 

frequency, 

in percent

Cache la 

Poudre River, 

Colorado

(N=17)

Truckee 

River, 

Nevada

(N=17)

Clackamas 

River, 

Oregon

(N=17)

Running Gutter 

Brook, Massachusetts

(N=16)

Chattahoochee 

River, 

Georgia

(N=17)

Neuse River, 

North 

Carolina

(N=17)

Potomac River, 

Maryland

(N=12)

T

Plant- or animal-derived biochemicals

Cholesterol 17 ND ND 6 ND 31 47 25 beta-Stigmastanol 11 ND ND ND ND 25 35 8 3-beta-Coprostanol 10 ND ND ND ND 13 29 25 

Solvents

p-Cresol 20 12 41 18 13 31 24 8 Perchloroethene (PCE) 17 ND ND ND ND ND 41 ND cis-1,2-Dichloroethene 12 ND ND ND ND ND ND ND 
Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 17

The five herbicides detected most commonly in sourcewater samples also were among those detected most frequently 

in ambient water collected as part of NAWQA studies from 

156 streams across the Nation during 1992–2001, including 83 agricultural, 8 undeveloped, and 65 mixed-land use 

watersheds (fig. 3) (Gilliom and others, 2006). Detection 

frequencies by land use generally are comparable for sourcewater sites sampled in this study on the basis of all detections, 

except in undeveloped streams (fig. 3). These herbicides, 

with the exception of simazine, were detected less commonly 

in source-water samples than in ambient stream samples 

collected in the relatively undeveloped streams (fig. 3A). 

This difference may be because three of the four sourcewater sites are in the western part of the United States, where 

simazine, atrazine, and metolachlor are used less than in 

the Midwest and eastern United States (Gilliom and others, 

2006). Conversely, most herbicides (with the exception of 

deethylatrazine) were detected more commonly in sourcewater samples collected in the mixed and agricultural landuse watersheds in this study than in ambient stream samples 

(figs. 3B and 3C), which may be because the source-water 

samples were from streams in the Midwest and East where 

these herbicides have much greater use than in other parts of 

the United States (Gilliom and others, 2006). Differences in 

occurrence in mixed and agricultural land-use settings were 

somewhat larger using a common assessment level of 0.1 μg/L 

(figs. 3B and 3C). Most notably, simazine was detected more 

frequently in this study in both of these settings, perhaps 

because most of these sites are located in urban or suburban 

areas of the watershed.

Previous studies indicate that herbicide degradates 

typically occur with their parent compounds at concentrations similar to or greater than concentrations of their parent 

compounds (Thurman and others, 1992; Kalkhoff and others, 

1998; Gilliom and others, 2006). For many degradates, little is 

known about their occurrence or their effects on human health. 

With a few exceptions for pesticides and degradates with 

known common modes of action, drinking-water standards or 

human-health benchmarks are not available for most pesticide 

degradates.

Several degradates, principally those of atrazine and 

other triazine herbicides, as well as 3,4-dichloroaniline (a 

degradate of diuron), were analyzed in samples collected at 

all source-water sites and were detected commonly during 

this study (fig. 2). These degradates usually were present 

when the parent herbicide was detected in source-water 

samples, and concentrations typically were less than those of 

the parent herbicide. Degradates generally were as common 

in source water as the parent pesticide. For example, at the 

Potomac, Elm Fork Trinity, and White Rivers, both atrazine 

and its degradate deethylatrazine were detected in all samples 

(table 6).

Degradates of the chloroacetanilide herbicides 

metolachlor, alachlor, and acetochlor were analyzed in 

samples collected from the Neuse, Potomac, and White 

Rivers. These sites included areas where these herbicides had 

potential use for agriculture. Similar to results for degradates 

of atrazine, these degradates usually were detected with the 

parent compounds; however, the summed concentrations of 

degradates of metolachlor and alachlor typically were similar 

to or greater than the parent herbicide concentration (fig. 4). 

Results for degradates of acetochlor were similar to those of 

metolachlor, but acetochlor was detected only at the White 

River site. In samples from the Potomac River, however, 

alachlor was not detected even though its degradate alachlor 

ethane sulfonic acid was detected in about 75 percent of 

samples. This pattern was observed despite the fact that the 

LRL for alachlor is about an order of magnitude lower than the 

LRL for its degradates. This difference in occurrence between 

atrazine and chloroacetanilide degradates is most likely due to 

differences in the chemical properties of the parent herbicides. 

Specifically, atrazine is more mobile and chemically stable 

than metolachlor and alachlor, allowing atrazine to persist 

in the hydrologic system longer. These results highlight the 

fact that for some pesticides information on the occurrence of 

degradates may be as important as information for the parent 

compound particularly if the degradate toxicity or mode of 

action is similar to that of the parent compound.

The insecticides diazinon, fipronil, and carbaryl were 

detected in samples from as many as six of the nine sites 

(table 6). Fipronil and carbaryl were detected in 29 and 

15 percent of samples, respectively. Diazinon had the largest 

detection frequency of the three insecticides and was present 

in 39 percent of samples. It was detected in almost all of the 

samples from the Elm Fork Trinity River and in samples from 

five other sites. Both diazinon and carbaryl were among the 

most commonly detected insecticides in streams sampled by 

the NAWQA Program, and detection frequencies were highest 

in watersheds characterized as urban (Gilliom and others, 

2006). Insecticides were not detected in samples from three 

sites (table 6); the watersheds for two of these sites included 

less than 1 percent urban land use.

Several of the most commonly detected compounds may 

be contributed to surface waters from municipal or industrial wastewater discharge. For example, chloroform may be 

present in treated wastewater because of the household use 

of bleach as well as the disinfection of wastewater during the 

treatment process (Ivahnenko and Barbash, 2004). Chloroform 

was the most commonly detected compound in source water 

(69 percent of samples), and was present in samples from eight 

of the nine sites (table 6). It also was detected year-round (in 

all samples) at five of the nine sites. Other possible sources of 

chloroform include its use as a refrigerant for home air conditioners and large commercial freezers, and it also has been 

used in reagents, extraction solvents, fumigants, insecticides, 

and as a precursor for dyes and pesticides. Caffeine, HHCB, 

and acetyl hexamethyl tetrahydronaphthalene (AHTN) may 

be introduced to surface waters in wastewater discharge. The 

fragrance compounds HHCB and AHTN commonly are used 

in detergents and other personal-care products and have been 

found in both influent and effluent of wastewater-treatment 

plants in the United States and Europe (Bester, 2004; Phillips 
Figure 3. The herbicides most commonly detected in source-water samples from Source Water-Quality Assessment (SWQA) 

sites collected during the first phase of sampling, October 2002–March 2004, correspond to those detected most frequently in 

156 streams across the Nation sampled by the National Water-Quality Assessment (NAWQA) Program (1992–2001) (Gilliom and 

others, 2006) in A, undeveloped; B, mixed; and C, agricultural land-use areas.

Atrazine

Deethylatrazine

Metolachlor

Simazine

Prometon

Atrazine

Deethylatrazine

Metolachlor

Simazine

Prometon

0 20 40 60 80 100

A. Undeveloped land use 

B. Mixed land use 

C. Agricultural land use 

Atrazine

Deethylatrazine

Metolachlor

Simazine

Prometon

DETECTION FREQUENCY, IN PERCENT

Source Water-Quality Assessment sites

National stream data

Detection frequency based on all detections

Detection frequency based on an assessment 

 level of 0.1 microgram per liter

Detection frequency based on all detections

Detection frequency based on an assessment 

 level of 0.1 microgram per liter

EXPLANATION

18 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Figure 4. The distributions of concentrations of herbicide degradates were similar to or greater than concentrations of parent 

compounds in source-water samples collected from the Neuse, Potomac, and White Rivers during the first phase of sampling, 

October 2002–March 2004.

Atrazine

degradates

Atrazine Metolachlor Metolachlor Alachlor

degradates

Alachlor

degradates

0.01

0.1

1

10

CONCENTRATION, IN MICROGRAMS PER LITER

34 37 39 27 12 24

24

75th percentile

Number of detections in 39 samples

Data value less than or equal to 1.5 times the interquartile

 range outside the quartile

Median

25th percentile

Outlier data value more than 1.5 times the interquartile 

 range outside the quartile

EXPLANATION

[Atrazine degradates: sum of deethylatrazine, 2-hydroxyatrazine, deisopropylatrazine, and 

deethyldeisopropylatrazine; metolachlor degradates: sum of metolachlor ethane sulfonic acid 

and metolachlor oxanilic acid; alachlor degradates: sum of alachlor ethane sulfonic acid,

alachlor oxanilic acid, and alachlor sulfynilacetic acid. Note: laboratory reporting levels are 

lower for atrazine, its degradates, metolachlor, and alachlor than for the degradates of 

alachlor and metolachlor.]

Interquartile range

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 19

and others, 2005). Manufacturing additives, such as tri(2-chloroethyl)phosphate and tris(dichlorisopropyl)phosphate, and the 

biochemicals cholesterol and 3-beta-coprostanol were detected 

in a national reconnaissance of emerging contaminants in 

surface waters that receive a substantial amount of municipal, industrial, or agricultural wastewater discharge (Kolpin 

and others, 2002). These biochemicals may be contributed to 

streams with wastewater discharge, but they also occur naturally in the environment.

Seven gasoline hydrocarbons and oxygenates were 

commonly detected (fig. 2 and Appendix 1). Methyl tert-butyl 

ether (MTBE), an oxygenate, was detected in 36 percent of the 

samples, representing six of the nine sites and was in all of the 

samples collected from the Elm Fork Trinity River (table 6). 

The other gasoline hydrocarbons were detected periodically 

at several of the sites, but more than one-half of the samples 

from the Clackamas River had detections of several gasoline 

hydrocarbons (table 6). These compounds may be contributed 

to surface waters from ground-water discharge that is contaminated, runoff from roads and parking lots, and watercraft that 

are used on these streams or upstream reservoirs. The results 

in this study are similar to results from a study of the occurrence of VOCs in drinking-water sources in which gasoline 

compounds were the second most commonly detected group 

of compounds following the disinfection by-products, and 

MTBE was the second most commonly detected VOC (Grady, 

2003).

Three solvents were detected in more than 10 percent 

of samples. The solvent p-cresol was detected at all sites. At 

six of the nine sites it was detected in three or fewer samples, 

and most of these detections were at concentrations 10 to 

100 times less than the LRL for this compound. Perchloroethene (PCE) was detected at three sites, and cis-1,2-DCE was 

detected only in samples from the White River (table 6). The 

frequent occurrence of PCE and cis-1,2-DCE predominantly 

in samples from the White River indicates that the source of 

these solvents may be a nearby point source.

Comparison to Human-Health Benchmarks

More than one-half of the compounds detected in source 

water have a human-health benchmark to which concentrations could be compared. Annual mean concentrations of all 

compounds at each site were less than human-health benchmarks. Most of the compounds detected were present at 

concentrations less than 0.1 μg/L (Appendix 1), and only three 

compounds (atrazine, acetochlor, and dieldrin) had singlesample concentrations greater than their applicable humanhealth benchmark (Appendix 1). BQ values for single samples 

for all other commonly detected compounds were one to five 

orders of magnitude less than 1 (figs. 5 and 6). Dieldrin was 

detected in only one sample, but the measured concentration 

was two times greater than its benchmark concentration of 

0.002 μg/L.

Twelve of the 47 most commonly detected compounds 

have an MCL to which concentrations in samples could 

be compared. Annual mean concentrations for all of these 

compounds were less than MCLs. Only simazine and atrazine 

were detected in samples at concentrations within a factor of 

10 or greater than an MCL concentration (fig. 5). Simazine 

was detected in samples from the Chattahoochee, Elm Fork 

Trinity, Potomac, and White Rivers at concentrations resulting 

in a BQ value greater than 0.1. The maximum annual mean 

concentration among these stream sites was at the Elm Fork 

Trinity River. The mean concentration of 0.44 μg/L was about 

an order of magnitude less than the MCL of 4 μg/L.
Figure 5. Annual mean and single-sample concentrations of regulated anthropogenic organic compounds 

commonly detected in source-water samples collected during the first phase of sampling, October 2002–March 

2004, were A, usually less than 1 microgram per liter; and B, usually less than one-tenth of the Maximum Contaminant Levels (MCLs).

0.00001 0.0001 0.001 0.01 0.1 1 10

BENCHMARK QUOTIENT (BQ) VALUE

BQ BQ

0.001 0.01 0.1 1 10

CONCENTRATION, IN MICROGRAMS PER LITER

A

B

cis-1,2-Dichloroethene

 Perchloroethene

Alachlor

2,4–D

Atrazine

Simazine

o-Xylene

m- & p-Xylene

Benzene

Toluene

Bromodichloromethane

Chloroform

cis-1,2-Dichloroethene

 Perchloroethene

Alachlor

2,4–D

Atrazine

Simazine

o-Xylene

m- & p-Xylene

Benzene

Toluene

Bromodichloromethane

Chloroform

Disinfection

by-products

Herbicides

Gasoline

hydrocarbons

Solvents

Disinfection

by-products

Herbicides

Gasoline

hydrocarbons

Solvents

Neuse River

Running Gutter Brook

Truckee River

Cache la Poudre River Potomac River

Elm Fork Trinity River White River

Clackamas River

Chattahoochee River

EXPLANATION

Note: Isomers of xylene are compared to the 

MCL of 10,000 micrograms per liter for total xylenes, 

and chloroform and bromodichloromethane are 

compared to the MCL of 80 micrograms per liter for 

sum of four trihalomethanes. 

BQ values less than 0.00001 are not shown

Single-sample concentrations are in green and annual 

mean concentrations are in blue

20 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Figure 6. Annual mean and single-sample concentrations of unregulated anthropogenic organic compounds commonly detected in 

source-water samples collected during the first phase of sampling, October 2002–March 2004, were A, usually less than 1 microgram 

per liter; and B, commonly much less than one-tenth of human-health benchmarks.

Neuse River

Running Gutter Brook

Truckee River

Potomac River

Cache la Poudre River

Elm Fork Trinity River White River

Clackamas River

Chattahoochee River

EXPLANATION

Single-sample concentrations are in green and 

annual mean concentrations are in blue. 

BQ values less than 0.00001 are not shown

MCPA 2-methyl-4-chlorophenoxyacetic acid

Carbaryl

Diazinon

Tebuthiuron

Terbuthylazine

Acetochlor

Triclopyr

MCPA

Diuron

2-Hydroxyatrazine

Prometon

Metolachlor

Benomyl

Bentazon

B BQ BQ

0.00001 0.0001 0.001 0.01 0.1 1 10

0.001 0.01 0.1 1 10

Carbaryl

Diazinon

Tebuthiuron

Terbuthylazine

Acetochlor

Triclopyr

MCPA

Diuron

2-Hydroxyatrazine

Prometon

Metolachlor

Benomyl

Bentazon

CONCENTRATION, IN MICROGRAMS PER LITER

BENCHMARK QUOTIENT (BQ) VALUE

Herbicides

and degradates

Insecticides

Fungicide

Herbicides

and degradates

Insecticides

Fungicide

A

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 21
22 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

Generally, concentrations of atrazine were less than onetenth of the MCL (BQ values less than 0.1) except in the Elm 

Fork Trinity, Potomac, and White Rivers, which had at least 

one sample with a BQ value greater than 0.1. Atrazine was 

detected in three samples from the White River at concentrations greater than its MCL of 3 μg/L. These relatively high 

instantaneous concentrations of atrazine were detected in 

samples collected during the spring and summer from the 

White River, where agriculture is the predominant land use in 

the watershed. The highest atrazine concentration (20.1 μg/L) 

was in a source-water sample collected during high streamflow conditions in the spring, when peak concentrations of 

herbicides in streams typically occur and usually for short 

periods (Gilliom and others, 2006). With the exception of two 

other samples, single-sample concentrations at other times 

were less than 3 μg/L (Carter and others, 2007), and the annual 

mean concentration of atrazine in source water from the White 

River (October 2002–September 2003) was 2.2 μg/L.

Thirteen of the 47 commonly detected unregulated 

compounds have an HBSL. Annual mean concentrations of all 

13 of these compounds were less than their HBSL concentration. Very few samples had individual BQ values greater than 

0.1 (fig. 6). Acetochlor was the only compound with a singlesample BQ value greater than 1. The maximum concentration 

of acetochlor was 4.32 μg/L, which was in the same spring 

sample as the maximum atrazine concentration from the White 

River. Other single-sample concentrations were less than the 

HBSL of 1 μg/L (Carter and others, 2007). The annual mean 

concentration of acetochlor at the White River from October 

2002 through September 2003 was 0.38 μg/L, which is about 

one-third the HBSL for acetochlor.

Twenty-two commonly detected compounds did not 

have a human-health benchmark for comparison. Of these 

compounds, HHCB, a fragrance, was the most commonly 

detected and was present in about one-half of the samples 

collected. Degradates of atrazine were the second and third 

most commonly detected compounds without an MCL or 

HBSL. Concentrations of the atrazine degradates were about 

equal to or less than atrazine concentrations in most samples. 

The maximum concentration for a compound without a 

human-health benchmark was 6.6 μg/L for nonylphenol 

diethoxylate (total), a compound found in personal-care products.

Mixtures of Compounds

Contaminants typically co-occur as mixtures, in part, 

because surface water represents a mixture of water from 

multiple sources and because different factors may affect 

each of these sources. Surface water usually is a combination 

of water derived from overland runoff, upstream reservoir 

releases, ground-water inflow, and municipal or industrial 

wastewater discharge. Each of these components in a watershed can be affected by different land uses and activities. 

Thus, the composition of mixtures in surface (source) water 

depends on relative proportion of each of these components of 

flow and the presence of compounds in each of these components.

The potential human-health effects of mixtures of 

co-occurring organic compounds are largely unknown 

and have not been extensively studied. The effect of one 

compound on another’s toxicity may be additive, antagonistic 

(one compound may lessen the effect of another), or synergistic, but much of the growing concern about exposure to 

mixtures of compounds is related to the potential for synergistic effects (Carpenter and others, 2002). Synergism is when 

the effect of exposure to a mixture is greater than, or different 

from, the additive effect of the compounds. Drinking-water 

standards (MCLs) and other human-health benchmarks generally are based on toxicity data for individual compounds, and 

the effects of specific mixtures of compounds at low levels are 

not well understood. With a few exceptions for pesticides with 

common modes of action, human-health benchmarks generally 

are not available for specific mixtures. Continued research is 

needed on potential toxicity of such compound mixtures, and 

evaluation of the potential effects of mixtures is an increasingly important component of the risk assessment methods 

used by USEPA, the Agency for Toxic Substances and Disease 

Registry, and other agencies.

As a first step toward evaluating the potential importance 

of mixtures of organic compounds to source-water quality, this 

study used a basic co-occurrence analysis. Although annual 

mean concentrations and nearly all single-sample concentrations of individual compounds detected were low relative to 

human-health benchmarks, most samples contained mixtures 

of two or more compounds (fig. 7). Considering all detections, 

mixtures of five or more compounds were found in 75 percent 

of all source-water samples, about 50 percent of the sourcewater samples contained 13 compounds, and 25 percent 

contained 25 or more compounds (fig. 7). The most frequent 

contributors to mixtures, not surprisingly, are the compounds 

that were detected most commonly. These include the herbicides simazine, atrazine and its degradates, metolachlor, and 

prometon, as well as chloroform and HHCB.

The frequent co-occurrence of multiple organic 

compounds in source waters as mixtures indicates a need to 

better understand which specific combinations of compounds 

occur most frequently and which may be a potential concern 

for human health. Identification of specific combinations 

of compounds would provide perspective on patterns of 

co-occurrence that may be important as more is learned about 

sources and potential health effects of mixtures. These are 

important research topics for the future, but are beyond the 

scope of this report.

Factors that May Affect Source-Water Quality

Although this study was not designed as a detailed 

assessment of specific sources and factors affecting the occurrence and concentrations of organic compounds in source 
Figure 7. Mixtures of two or more anthropogenic organic 

compounds analyzed were present in many source-water samples 

collected during the first phase of sampling, October 2002–March 

2004.

Figure 8. The median number of anthropogenic organic 

compounds and median total concentration of all compounds 

detected in source-water samples collected during the first phase 

of sampling, October 2002–March 2004, for each site generally 

increased as the sum of agricultural and urban land use in the 

contributing watersheds increased.

0 10 20 30 40 50

NUMBER OF COMPOUNDS IN A SAMPLE

0

20

40

60

80

100

PERCENTAGE OF SAMPLES WITH EQUAL OR 

GREATER NUMBER OF COMPOUNDS

0 10 20 30 40 50 60 70 80 90 100

SUM OF AGRICULTURAL AND URBAN LAND USE, IN PERCENT

0

10

20

30

MEDIAN NUMBER OF COMPOUNDS DETECTED

2.5 to 4

Median total concentration, 

 in micrograms per liter

1 to 1.5

0.2 to 0.5

Less than 0.05

Elm Fork Trinity River White River

Neuse River

Potomac River

Chattahoochee River

Running Gutter Brook

Clackamas River

Truckee River

Cache la Poudre River

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 23

waters, evaluation of the characteristics of individual CWSs 

provides an initial analysis of the general patterns and associations related to land use, wastewater discharge, streamflow, 

and seasonality. These factors have been found to be associated with the occurrence of organic compounds in other 

studies (for example, Kolpin and others, 2002, 2004; Gilliom 

and others, 2006).

Land Use

The occurrence of particular compounds or combinations 

of compounds generally follows patterns in watershed land 

use. Relatively few compounds (10 or fewer) were detected 

and concentrations were low (less than 0.1 μg/L) in most 

samples collected from the Cache la Poudre, Clackamas, and 

Truckee Rivers and Running Gutter Brook that drain relatively undeveloped watersheds, as compared to the other five 

streams that drain watersheds with more agricultural and urban 

areas, where between 9 and 30 compounds were detected 

(table 1). The median total concentration of all compounds 

detected in samples from these four streams was less than 

0.5 μg/L (fig. 8), whereas the median total concentration 

for streams with more agricultural and urban land use in the 

watershed was between 1 and 4 μg/L. At least nine compounds 

were detected in every sample from the Elm Fork Trinity and 

White Rivers (table 6), where agriculture is the predominant 

land use in the contributing watersheds (table 1). Many of the 

compounds commonly detected at these sites were herbicides or herbicide degradates; however, chloroform also was 

detected in all samples at these sites as well as in all samples 

from Running Gutter Brook and the Neuse and Potomac 

Rivers (table 6). The Cache la Poudre River is the only site at 

which no commonly detected pesticides or pesticide degradates were detected (table 6). This site is located in a sparsely 

populated area on the main stem of the Cache la Poudre 

River in Colorado, with much of the upstream drainage area 

included in National Park and National Forest land.

In general, more pesticides were detected at sites with 

larger amounts of agricultural land use in their contributing 

watersheds (table 6). The frequency of detection and concentrations at which some herbicides were detected increased as 

the amount of agricultural land use in the watershed increased, 

whereas others did not. For example, atrazine was detected at 

eight of the nine sites, and its detection frequency and concentrations generally increased as the amount of agricultural land 

use in those watersheds increased (fig. 9). The stream where 

atrazine was not detected, the Cache la Poudre River, essentially has no agricultural land use in its watershed. In contrast, 

no clear relation between agricultural land use and the occurrence or concentration of simazine, is evident (fig. 9), likely 

due, in part, to substantial use of simazine in non-agricultural 

areas. Thus, as would be expected from use patterns, the 

amount of agricultural land use alone is not necessarily a good 

predictor of the potential for detection of a given pesticide.

The relation between the amount of urban land use in the 

watersheds of the nine sites and the occurrence of compounds 

that likely would be contributed from urban areas, such as 

chloroform or MTBE, is not as strong as the relation between 

agricultural land use and its associated compounds. Many 

compounds related to urban land use were not detected at 

enough of the stream sites to evaluate their occurrence with 

respect to the relative amount of urban land in the contributing 

watersheds. This result may be due, in part, to the small-scale 

use of these compounds in urban settings, which tends to 

cause only local contamination. In addition, the differences in 

the amount of urban land use in the contributing watersheds 
Figure 9. Atrazine concentrations in source-water samples collected during the first phase of sampling, October 2002–March 2004, 

generally increased as the amount of agricultural land use in the contributing watersheds increased. The relation between agricultural 

land use and simazine concentrations was not as strong as that of atrazine likely because of substantial non-agricultural use of 

simazine.

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

100

CONCENTRATION, IN MICROGRAMS PER LITER

17 17 17 16 17 17 12 17 16

17 17 17 16 17 17 12 17 16

Atrazine

LRL

Simazine

LRL

Cache la Poudre River

Truckee River

Clackamas River

Running Gutter Brook 

Chattahoochee River

Neuse River

Potomac River

Elm Fork Trinity River

White River

Agricultural land use increases

Less than or equal to 10 percent

(undeveloped)

Greater than 10 percent

(mixed and agricultural and urban 

land use)

16

75th percentile

Number of samples

Data value less than or equal to 1.5 times the 

 interquartile range outside the quartile

Data value less than or equal to 1.5 times the 

 interquartile range outside the quartile

Laboratory reporting level

Median

25th percentile

Outlier data value more than 1.5 times the interquartile range 

 above the 75th percentile or below the 25th percentile

Interquartile range

EXPLANATION

LRL

24 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 25

of these sites are considerably less than the differences in the 

amount of agricultural land use (table 1).

Wastewater Discharge

Compounds in four primary-use groups, including 

disinfection by-products, manufacturing addititives, personalcare and domestic-use products, and plant- or animal-derived 

biochemicals, were detected most commonly in samples from 

the Chattahoochee, Elm Fork Trinity, Neuse, Potomac, and 

White Rivers. These five watersheds have major municipal 

wastewater discharges upstream from the sampling locations. 

For this analysis, the daily mean discharge of major municipal 

wastewater discharges (those greater than 1 million gallons per 

day) upstream from the sampling sites within each watershed 

were summed. This analysis is qualitative because it does not 

account for minor discharges, the distance between wastewater 

inputs and the sampling point, or the amount of wastewater as 

a fraction of total streamflow.

Chloroform and HHCB were the most commonly 

detected compounds in the disinfection by-product and 

personal-care and domestic-use groups. The concentration 

ranges for chloroform and HHCB are shown in figure 10 

by stream site, which are ordered by the mean amount of 

treated wastewater discharged by major municipal wastewater 

discharges located within the watershed upstream from the 

CWS intake (U.S. Environmental Protection Agency, 2006b). 

Sites on Running Gutter Brook, the Cache la Poudre, Clackamas, and Truckee Rivers have no major wastewater (greater 

than 1 million gallons per day) inputs upstream from their 

sampling points.

Three of the four sites without major wastewater inputs 

had relatively few or no detections of chloroform. Detections 

of chloroform in every sample from Running Gutter Brook, 

which does not receive any major wastewater discharge, 

demonstrate that this compound can have multiple sources, 

and an understanding of local hydrology and sources of 

contaminants is needed to fully characterize source-water 

quality. Chloroform has several possible sources that could 

be affecting Running Gutter Brook, including chlorinated 

drinking water (for example, used for lawn or nursery irrigation), septic systems (Ivahnenko and Zogorski, 2006), and 

also natural sources such as from the formation of chloroform 

in soils by microbial processes (Laturnus and others, 2002). 

Detections of the fragrance compound HHCB also were 

infrequent at the four sites compared to the sites with major 

wastewater discharges.

Findings indicate associations between the occurrence of 

some compounds, such as chloroform and HHCB, in source 

water and upstream wastewater discharges. The occurrence 

of these compounds in streams that receive major wastewater 

discharge is consistent with several studies that show that 

organic compounds, such as pharmaceuticals and personalcare and domestic-use compounds, are not removed during the 

wastewater-treatment process and are detected in the receiving 

streams (Halling-Sorensen and others, 1998; Kolpin and 

others, 2002; Stackelberg and others, 2004).

Streamflow

For many of the most commonly occurring compounds, 

a relation between streamflow and concentration is evident 

at some sites, but not at all sites. For example, atrazine 

concentrations generally increased with streamflow at the 

White River site (fig. 11). At several of the other sites where 

atrazine was detected commonly, however, relatively high 

concentrations of atrazine occurred during both high and 

low streamflow conditions. Seasonal use of pesticides such 

as atrazine likely precludes a strong relation between occurrence and streamflow throughout the year. Although a strong 

relation between streamflow and atrazine concentration is not 

indicated at most sites, watershed hydrology can affect the 

occurrence and concentrations of compounds such as atrazine. For example, at the Elm Fork Trinity River site, which is 

downstream from a reservoir, the range in atrazine concentrations was considerably less than at other sites where atrazine 

was detected commonly. Just as a reservoir upstream moderates extremes in streamflow, the range of concentrations of 

compounds in the water also may be moderated. In addition to 

a moderating effect on extremes in concentration, reservoirs 

upstream from these source-water sites also may represent 

a constant source of some compounds throughout the year, 

similar to the way in which some compounds are contributed 

from ground-water or wastewater discharge.

The route by which compounds move through the 

hydrologic system also is an important factor in whether and 

how their concentrations change with streamflow. In general, 

there is an inverse relation between streamflow and concentration for compounds that are contributed to streams principally 

with ground-water or wastewater discharges. As streamflow 

increases from surface runoff that contains low concentrations 

of these compounds, concentrations in source water decrease. 

For example, concentrations of HHCB, which may be contributed to these streams with wastewater discharge or from 

failing septic systems, were inversely correlated to streamflow 

at several of the sites where it was detected (fig. 11).

 Many pesticide degradates are formed in the soil zone 

and subsequently are transported to underlying aquifers and 

eventually discharged to streams with ground water. An 

inverse relation at four sites between streamflow and concentrations of the herbicide degradate 3,4-dichloroaniline (fig. 11) 

indicates that this compound may be contributed to these 

streams with ground-water discharge, and that concentrations 

decrease when the proportion of ground water relative to the 

total streamflow is low in these streams. This type of relation 

does not exist for all of the degradates analyzed, however, 

most notably for the degradates of atrazine; their concentrations did not increase when ground water represented a large 

proportion of streamflow.
Figure 10. Chloroform and hexahydrohexamethylcyclopentabenzopyran (HHCB) were detected more commonly in source-water 

samples from watersheds with major wastewater discharges than in samples from watersheds without major discharges during 

the first phase of sampling, October 2002–March 2004.

0.01

0.1

0.01

0.1

1

1

CONCENTRATION, IN MICROGRAMS PER LITER

15 17 17 17 16 17 17 17 12

17 17 17 16 17 17 12 17 16

LRL

LRL

Running Gutter Brook

Cache la Poudre River

Clackamas River

Truckee River 

Chattahoochee River

Neuse River

Potomac River

Elm Fork Trinity River

White River

No major wastewater discharges

16

Amount of wastewater discharge

upstream from sampling point 

increases

Laboratory reporting level LRL

75th percentile

Number of samples

Data value less than or equal to 1.5 times the interquartile

 range outside the quartile

Data value less than or equal to 1.5 times the interquartile

 range outside the quartile

Median

25th percentile

Outlier data value more than 1.5 times the interquartile 

 range above the 75th percentile

EXPLANATION

Interquartile range

HHCB

Chloroform

26 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
LRL Hexahydrohexamethylcyclopentabenzopyran (HHCB)

3,4-Dichloroaniline

10 100 1,000 10,000 100,000

0.001

0.01

0.1

LRL

0.001

0.01

0.1

1

10

0.01

0.1

1

Chattahoochee River

Neuse River

Running Gutter Brook

Truckee River

Cache la Poudre River Potomac River

Elm Fork Trinity River White River

Clackamas River

Atrazine

LRL

STREAMFLOW, IN CUBIC FEET PER SECOND

EXPLANATION

Laboratory reporting level

CONCENTRATION, IN MICROGRAMS PER LITER

LRL

Figure 11. The concentrations of selected commonly 

detected anthropogenic organic compounds in source-water 

samples collected during the first phase of sampling, October 

2002–March 2004, were related to streamflow at some sites, 

but not at others.

Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 27

Seasonal Variability

Relatively few compounds were detected year-round at 

most sites. The largest number of compounds in all samples 

throughout the year was 10 compounds in the Elm Fork 

Trinity River, and 6 of these (chloroform, simazine, atrazine, deethylatrazine, metolachlor, and 2-hydroxyatrazine) 

were detected year-round at more than one site (table 6). The 

frequency of detection and the concentrations of compounds 

throughout the year in streams may be the result of the source 

of a compound or transport route that it takes to the stream. 

For example, wastewater discharge may be a relatively 

constant source of some compounds such as chloroform 

or HHCB. For some compounds, including the herbicides 

that were detected throughout the year and cis-1,2-DCE, 

ground-water discharge during base-flow conditions may 

contain measurable concentrations of these compounds. Other 

compounds may be detected only for short periods of time 

after they are used.

Herbicides and their degradates had the most pronounced 

seasonal change in occurrence and total concentration 

(fig. 12), and had the largest number of compounds detected 

throughout the year. The amount and timing of change in total 

herbicide concentration varied among the sites. The largest 

changes in total herbicide concentrations occurred in the 

Chattahoochee, Potomac, and White Rivers, where the total 

concentration of herbicides varied by at least tenfold during 

the year. Smaller amounts of change occurred in Running 

Gutter Brook and the Neuse and Elm Fork Trinity Rivers. At 

several of the stream sites, high concentrations were associated with high streamflow, likely the result of runoff following storms after application times. Other studies have shown 

that high runoff following seasonal applications of herbicides 

results in the highest concentrations of the year (for example, 

Gilliom and others, 2006). At two sites, the Potomac and 

White Rivers, total herbicide concentrations increased with 

the addition of the chloroacetanilide herbicide degradates 

that were detected, but the concentration profile generally did 

not change (fig. 12). The other site at which these additional 

compounds were analyzed was the Neuse River, and only one 

of these degradates was detected in one sample.

The timing of changes in total herbicide concentration 

also varied among the sites. At the Neuse, Potomac, and White 

Rivers, higher concentrations occurred during the spring 

and summer compared to other times of the year (fig. 12). In 

contrast, peak concentrations at the Running Gutter Brook and 

the Chattahoochee and Elm Fork Trinity Rivers occurred in 

the fall or winter. However, in the Chattahoochee River, total 

herbicide concentrations also were high during the growing 

season.

Where several herbicides were detected at a site, the 

concentration profiles throughout the year typically were 

similar, but differences in when herbicides are applied and 

whether they are used in urban areas result in some differences 

in occurrence (fig. 13). For example, simazine and atrazine 

generally had similar concentration profiles for both the 
Figure 12. Total herbicide concentrations in source-water samples collected during the first phase of sampling, October 2002–March 

2004, varied seasonally at most sites.

Potomac River Chattahoochee River

White River

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

0.001

0.01

0.1

1

10

10

100

1,000

10,000

100,000

Neuse River

Elm Fork Trinity River Running Gutter Brook

EXPLANATION

Total herbicide concentration

Total herbicide concentration with additional 

 chloroacetanilide degradates

STREAMFLOW, IN CUBIC FEET PER SECOND

2004

Streamflow

2002 2003

O N D J F M A M J J A S O N D J F

2002 2003 2004

O N D J F M A M J J A S O N D J F

TOTAL HERBICIDE CONCENTRATION, IN MICROGRAMS PER LITER

28 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Figure 13. Seasonal variation in atrazine and simazine concentrations differed for samples collected from the Chattahoochee and White Rivers during the first phase of sampling, 

October 2002–March 2004.

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

Atrazine

Simazine

White River

Chattahoochee River

CONCENTRATION, IN MICROGRAMS PER LITER

Atrazine

Simazine

O

2002 2003 2004

N D J F M A M J J A S O N D J F

Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 29

Chattahoochee and White Rivers, but the maximum concentration of simazine at the Chattahoochee River was in November, 

whereas the maximum atrazine concentration occurred in late 

February. This large increase in simazine concentration in the 

fall compared to atrazine likely is a result of urban uses of 

simazine in the Chattahoochee River watershed. An increase 

in simazine concentrations during the fall has been observed 

in other streams with urban and suburban land use and may 

be the result of the use of pre-emergent herbicides on lawns 

during the fall and winter for the control of winter weeds 

(Frick and others, 1998; Gilliom and others, 2006). Concentration profiles of atrazine and simazine also were similar at the 

White River; however, a small increase in simazine concentrations in September and October also occurred at the White 

River. The timing of peak concentrations of both herbicides 

likely differed at the two sites because of when these herbicides are applied.

Comparisons of Selected Organic 

Compounds in Source Water and 

Finished Water Sampled in 2004 and 

2005

The secondary purpose of this report is to provide 

comparisons of selected compounds in source water with their 

occurrence in finished water (water that has passed through 

treatment processes but prior to distribution). Samples of 

source and finished water were collected during 2004–05 at 

eight of the nine CWSs. Because relatively few compounds 

were detected in samples from the Cache la Poudre River 

during the first phase of sampling, this site was not sampled 

during the second phase.

Monitoring during the second phase of the study generally focused on analytical suites that included compounds 

found to occur most commonly in source water during the 

2002–04 monitoring. The number of samples collected at 

each of the sites, therefore, was smaller during the second 

phase of sampling, and not all samples were analyzed for 

the 258 compounds that were analyzed in most source-water 

samples collected during the first phase. As a result of these 

differences and the more targeted sampling in the second 

phase, detection frequencies of compounds in source water 

would be expected to be greater than in the first phase of 

sampling. Additionally, differences in streamflow or changes 

in chemical use in a watershed between sampling phases may 

affect the occurrence of some compounds.

Finished-water samples were collected after treatment 

at each of the CWSs, and time was allowed between collection of the source- and finished-water samples to account for 

the retention time in the treatment plant (table 7). Retention 

time was determined through individual contact with treatment plant operators at each CWS. At some of the sites, the 

amount of time between collection of the two types of samples 

was varied to account for changes in retention time that result 

from changes in water demand. At other sites, finished-water 

samples were collected at fixed intervals after the sourcewater samples were collected, which generally represented 

an average retention time. Two CWSs intermittently blend 

ground water from wells with the surface-water source. The 

CWS on Running Gutter Brook augments the surface-water 

supply with ground water after treatment, and the CWS on 

the White River uses ground water intermittently to meet 

demand during peak use. Some differences between sourceand finished-water quality might be attributable to changes in 

source-water quality that are not represented by the finishedwater sample, particularly for sites where water was blended 

with other sources or where the same amount of time between 

samples was used for all samples. Other factors also may 

affect differences in occurrence between source- and finishedwater samples that may not be attributed entirely to treatment, 

including the inadvertent addition of compounds in finished 

water from pipes and other plumbing, treatment-plant mainte-
Table 7. Length of time between collection of source- and 

finished-water samples during the second phase of sampling, 

June 2004–August 2005.

Stream site

Time between collection 

of surface- and finishedwater samples

Chattahoochee River, Georgia 5 hours

Clackamas River, Oregon 1 hour

Elm Fork Trinity River, Texas 2 hours

Neuse River, North Carolina 2 to 5 days

Potomac River, Maryland 2 days

Running Gutter Brook, Massachusetts 1 to 3 days

Truckee River, Nevada 4 hours

White River, Indiana 8 to 18 hours

30 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

nance, and potential analytical variability associated with low 

concentrations at or near LRLs.

The sampling design and resulting comparisons between 

source- and finished-water samples were not intended to 

characterize treatment efficacy, which would require precise 

timing of sampling at different stages of water treatment. In 

general, the types of treatment used by the CWSs that were 

sampled in this study were not specifically designed to remove 

most of the organic compounds monitored. For example, five 

of the eight CWSs used conventional water treatment, consisting of coagulation, flocculation, sedimentation, filtration, and 

disinfection. The other three CWSs used other types of treatment (table 2). Results for the compounds monitored in this 

study represent an initial assessment of whether compounds 

present in source water also are present in the associated 

finished water.

Finished-water samples were “quenched” with ascorbic 

acid at the time of collection to scavenge the free chlorine 

that might react with any compounds present in the sample. 

Therefore, finished-water data are not necessarily representative of drinking-water quality at the tap because additional 

contact time with disinfectants in the distribution system may 

change concentrations of some of the constituents detected 

in the finished water at the sample collection point. Some 

compounds may be transformed or degraded, whereas others 

such as disinfection by-products may continue to form in the 

distribution system.

Commonly Detected Compounds

In general, compounds that were detected commonly 

in source water during the first sampling phase (defined 

as detected in more than 10 percent of samples) also were 

detected commonly during the second phase of sampling, and 

at relatively similar detection frequencies. One notable exception was diazinon, which was detected in more than 40 percent 

of the samples during the first phase of sampling and in only 

about 20 percent during the second phase. This reduced 

frequency of detection may be the result of the phase out 

of residential uses of diazinon on December 31, 2004 (U.S. 

Environmental Protection Agency, 2008b). Four compounds 

(1,2,4-trimethylbenzene, tert-butyl alcohol, tebuthiruon, 

and beta-stigmastanol) detected commonly in source water 

during the first phase of sampling were detected in less than 

10 percent of source- or finished-water samples or were not 

detected during the second phase of sampling.

About two thirds (27) of the compounds detected 

commonly in source water (not including degradates of 

chloroacetanilide herbicides) during June 2004–August 2005 

also were commonly detected in finished water, and for many 

of these compounds at about the same frequency (fig. 14). Of 

the remaining 15 compounds detected commonly in source 

water, the detection frequency in finished water was one-half 

or less than the detection frequency in source water. Eleven 

compounds were detected commonly in finished water and 

were either not detected in source water or had a detection 

frequency in source water no more than one-half the detection frequency in finished water. Detection frequencies of all 

compounds detected in source or finished water are summarized in Appendix 2; however, the discussion of results in this 

section of the report focuses on the 53 compounds that were 

detected commonly (in 10 percent of source- or finished-water 

samples) in the second phase of sampling (fig. 14) because 

relatively little can be inferred about patterns of occurrence in 

source and finished water from compounds that were detected 

at low concentrations in only a few samples.

Compounds Detected More Commonly in Source 

Water than in Finished Water

Fifteen of the 53 commonly detected compounds had a 

detection frequency in finished water that was about one-half 

or less than the detection frequency in source water (fig. 14). 

Smaller detection frequencies in finished water may indicate 

a decrease in concentration below the LRLs of compounds 

during water treatment as a result of transformation, volatilization, sorption, or sedimentation. 

Four compounds—3,4-dichloroaniline (an herbicide 

degradate), diazinon and fipronil (insecticides), and fipronil 

sulfone (the degradate of fipronil)—were detected commonly 

in source water but were not detected or were detected in 

2 percent or less of the associated finished-water samples 

(fig. 14). The degradation of organophosphate insecticides 

such as diazinon has been observed in studies of the effect of 

chlorination on pesticides (Magara and others, 1994). Diazoxon (diazinon oxygen analog), which is the principal degradate formed as a result of the oxidation of diazinon during 

chlorination (Aizawa and others, 1994), was detected in one 

finished-water sample in this study; however, because most of 

the measured concentrations of diazinon in source water were 

less than the LRL for diazoxon, detection of this degradate 
0 20 40 60 80 100

Herbicides 

and herbicide 

degradates

Gasoline-related

compounds

Solvents

Insecticides

and insecticide

degradates

Fungicide

DBPs

Manufacturing

additives

Personal care and

domestic use

Plant or animal 

biochemicals

Chloroform*

Bromodichloromethane*

Bromoform*

Dibromochloromethane*

Benomyl

Methyl tert-butyl ether

Benzene*

m- and p-Xylene*

Toluene*

Ethylbenzene*

o-Xylene*

Atrazine*

Simazine*

Metolachlor

Deethylatrazine

Deisopropylatrazine

Prometon

2-Hydroxyatrazine

3,4-Dichloroaniline

2,4–D*

Diuron

Bentazon

Acetochlor

Terbuthylazine

MCPA

Alachlor*

Triclopyr

Desulfinylfipronil

Fipronil

Carbaryl

Fipronil sulfide

Diazinon

Fipronil sulfone

Tri(2-chloroethyl)phosphate

Tris(dichlorisopropyl)phosphate

Tributyl phosphate

Tri(2-butoxyethyl)phosphate

Triphenyl phosphate

Chloromethane

HHCB

Caffeine

AHTN

Camphor

Triethyl citrate

Nonylphenol diethoxylate (total)

Cholesterol

3-beta-Coprostanol

cis-1,2-Dichloroethene*

Perchloroethene*

p-Cresol

Methylene chloride*

Acetone

Carbon tetrachloride*

Organic synthesis

EXPLANATION

Source water

Finished water

*

DETECTION FREQUENCY, IN PERCENT

Note: compound names in bold were detected 

commonly in source water and had a 

similar detection frequency in finished water

Regulated compound

Disinfection by-product

Hexahydrohexamethylcyclopentabenzopyran

Acetyl hexamethyl tetrahydronaphthalene

DBP

HHCB

AHTN

MCPA 2-methyl-4-chlorophenoxyacetic acid

Figure 14. Many commonly detected anthropogenic organic 

compounds generally had similar detection frequencies in sourceand finished-water samples collected during the second phase of 

sampling, June 2004–August 2005 (using no common assessment 

level).

Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 31
32 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

would be unlikely even if it was produced. Other organophosphate insecticides, such as chlorpyrifos and malathion, were 

detected infrequently in source water and were not detected 

in corresponding finished-water samples, although malathion 

was detected in one finished-water sample without a corresponding source-water detection. These results are similar to 

results for organophosphate pesticides in source- and finishedwater samples reported by Coupe and Blomquist (2004).

 The compounds 3,4-dichloroaniline, fipronil, and 

fipronil sulfone are not organophosphates, but results for 

these compounds were similar to the those for organophosphate pesticides in that they generally were not detected in 

finished-water samples. The quality-assurance plan for this 

study included paired finished-water spike samples; one was 

quenched (with dechlorination reagents) and the other was 

not quenched. These three compounds were not detected in 

spike samples that did not have ascorbic acid added to quench 

free chlorine but were present in spike samples with ascorbic 

acid added, indicating that transformation of these compounds 

is related to chlorination (Valder and others, 2008). One 

other group of compounds that was not detected commonly 

in source water but appeared to be transformed or removed 

during water treatment were aromatic hydrocarbons with one 

or more methyl groups, such as 1,3,5-trimethylbenzene (a 

gasoline hydrocarbon, Appendix 2).

Eleven compounds had detection frequencies in finished 

water that were about one-half the detection frequency in 

source water (fig. 14). The decreases in detection frequency 

of diuron, desulfinylfipronil, fipronil sulfide, and p-cresol 

may be, in part, a result of the disinfection process. Qualityassurance data for unquenched spike samples compared to 

quenched spike samples indicated generally lower recoveries 

of these compounds in unquenched spikes (Valder and others, 

2008). Benomyl, prometon, carbaryl, tributyl phosphate, 

camphor, cholesterol, and 3-beta-coprostanol also were 

detected more commonly in source water than in finished 

water, but spike data do not indicate that concentrations are 

affected by chlorination; recoveries generally were similar 

for quenched and unquenched spikes. Seasonal use of PAC 

to treat for taste- and odor-compounds at several of the 

water-treatment plants or other differences in water-treatment 

processes also could be factors in smaller detection frequencies in finished water for all of these compounds.

Compounds Detected More Commonly in 

Finished Water than in Source Water

Eleven of the 53 commonly detected compounds had 

a detection frequency in finished water that was about two 

or more times greater than the detection frequency in source 

water or were not detected at all in source water (fig. 14). 

A higher detection frequency in finished water compared to 

source water could result from the formation of a compound 

during water treatment, sample-collection timing issues, 

analytical error at concentrations near the LRL, addition of 

a compound as a result of blending with other source water, 

chemicals used during water treatment, pipes and other plumbing, or use of the compounds in the water-treatment plant 

(sample contamination). Identification of all of the potential 

sources of compounds and determination of their effect on 

finished-water quality were beyond the scope of this study.

The formation of trihalomethanes as a result of the 

chlorination of drinking water is well documented (Rook, 

1974). In this study, chloroform was detected at low concentrations in most source-water samples; however, chloroform 

was detected in all finished-water samples at concentrations 

from 10 to 100 times greater in finished-water samples than 

in source-water samples. All finished-water concentrations of 

chloroform were less than the MCL for the trihalomethanes. 

Bromoform, dibromochloromethane, and bromodichloromethane were not detected or were detected infrequently in 

source-water samples but were detected in 32 to 100 percent 

of the finished-water samples (Appendix 2).

In addition to the disinfection by-products, several 

other compounds were detected in the finished water more 

commonly than in source water. These compounds generally 

were detected in samples from a few of the water-treatment 

plants, and most of these compounds were not detected 

commonly in source water. Acetone and methylene chloride 

were detected in finished-water samples collected at two and 

five of the CWSs, respectively. These solvents commonly are 

used in laboratory settings as cleaning agents (degreasing) and 

for chemical extractions. The occurrence of these compounds 

at low concentrations predominantly in finished water at these 

sites may reflect use of these VOCs at the water-treatment 

plants. Carbon tetrachloride was not detected in any sourcewater samples, but was present in 32 percent of the finishedwater samples (Appendix 2). The source of these low-level 

detections in finished-water samples is not known, but the 

carbon tetrachloride in the finished water may be a contaminant in the chlorine used for disinfection (Christman, 1980), or 

possibly a disinfection by-product (Krasner and others, 2006). 

Another example of the occurrence of compounds in 

finished water that were not present in the source water 

occurred at one treatment plant following routine maintenance 

that included painting of a clear well storage tank (Erik Staub, 

U.S. Geological Survey, written commun., 2007). Several 

hydrocarbons, including benzene, ethylbenzene, and isomers 

of xylene (fig. 14), were detected in finished-water samples 

following the painting, and concentrations of these compounds 

decreased in subsequent samples.

Changes in Concentration

The comparison of concentrations of organic compounds 

in source and finished water provides a preliminary perspective on the potential significance of the occurrence of 

compounds in source water to finished-water quality. 

However, the relatively low concentrations (0.1 μg/L or less) 

at which most compounds were detected limit the comparison 
Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 33

of changes in concentration from source to finished water. 

A small change in absolute concentration of a compound, 

for example a decrease from 0.05 to 0.03 μg/L from source 

to finished water, is relatively large on a percentage basis 

but may be the result of analytical variability, sample timing 

issues, or may reflect a true decrease. Because of these 

uncertainties, changes in concentration of commonly detected 

compounds generally were categorized as small, moderate, or 

large, reflecting finished-water concentrations that were less 

than 25 percent, between 25 and 75 percent, and more than 

75 percent of the source-water concentration. It also is important to note that, in general, conventional water treatment and 

most of the treatment steps used by the CWSs sampled are 

not specifically designed to treat for the organic compounds 

detected in this study. However, CWSs may use additional 

treatment steps if source water is known to contain compounds 

with concentrations near or greater than an MCL.

Although the water-treatment steps differ among the 

eight CWSs, the amount of change in concentration of organic 

compounds from source- to finished-water samples generally 

did not differ systematically at a CWS or among the CWSs for 

the 27 commonly detected compounds in source water where 

the detection frequency was similar to that in finished water. 

For example, when atrazine was detected in source water, 

it typically was detected in the associated finished water at 

all of the CWSs at a concentration within 50 percent of the 

source-water concentration (fig. 15A). Finished-water atrazine 

concentrations were significantly lower (p-value less than 

0.05; Wilcoxon signed rank test; Helsel and Hirsch, 1992) than 

source-water atrazine concentrations at three of the CWSs 

(Elm Fork Trinity, Neuse, and White Rivers), but the average 

amount of change in atrazine concentrations in most sample 

pairs from these three CWSs was less than 25 percent. The 

degradates of metolachlor, alachlor, and acetochlor were not 

analyzed at all sites, but results for these compounds generally were similar to those for atrazine in that finished-water 

concentrations generally were within 75 percent of sourcewater concentrations where these compounds were analyzed 

(Appendix 2).

A total of 15 compounds commonly detected (in more 

than 10 percent of all samples) in source water generally had 

moderate to large changes in concentration from source to 

finished water. Four of these—fipronil (fig. 15B), fipronil 

sulfone, diazinon, and 3,4-dichloroaniline—usually were not 

detected in finished water although they were present in the 

associated source-water sample. A few compounds that were 

detected in less than 10 percent of source-water samples, 

primarily organophosphate insecticides (for example, malathion, and chlorpyrifos) and aromatic hydrocarbons with one 

or more methyl groups (for example, 1,3,5-trimethylbenzene) 

either were not detected in finished-water samples or were 

detected at lower concentrations than in the associated sourcewater sample (Appendix 2).

Diuron was detected in source water from five of the 

eight sites, and in most sample pairs, concentrations were 

lower or diuron was not detected in finished water (fig. 15C); 

however, the amount of change in concentration varied among 

and within the CWSs. For example, diuron was detected in 

source water at five sites, but at the Neuse and White Rivers, 

it was not detected in the associated finished-water sample. 

At other sites, diuron was detected in both source and finished 

water in most samples and concentrations generally were 

somewhat lower in finished water. However, most of the 

concentrations were near the LRL and although it appears that 

diuron concentrations were affected by water treatment, particularly at two sites that use PAC, the results are not conclusive. 

These results for diuron and 10 additional compounds, such 

as benomyl, carbaryl, and cholesterol, indicate that concentrations of these compounds may be reduced as a result of 

treatment at the CWSs, but additional information is needed to 

better understand the factors that are affecting the occurrence 

of these compounds.

For most compounds without large changes in concentration from source to finished water, for example atrazine, 

changes in source-water concentrations during the year 

generally were reflected in the associated finished water. 

Few compounds were detected at most sites, so atrazine is 

used as an example of how concentrations varied over time 

in source and finished water (fig. 16). Atrazine was detected 

infrequently in source-water samples from the Clackamas and 

Truckee Rivers and these sites are not included in figure 16. At 

most sites, changes in atrazine concentrations in source water 

were reflected in the associated finished water.

Concentrations of atrazine in source- and finished-water 

samples did not differ by more than 25 percent for most 

samples from the Chattahoochee and Potomac River, and 

Running Gutter Brook sites (fig. 16); however, some differences between source water and finished water were observed. 

At the Chattahoochee River site, the concentration profile of 

atrazine in finished water appears to lag behind that of source 

water following increasing concentrations. The delay in 

higher finished-water concentrations relative to source-water 

concentrations may be the result of a mismatch in timing of 

source- and finished-water sample collection, or could represent adsorption-desorption of atrazine to and from anthracite 

filters used in the treatment process, similar to observations 

of Richards and others (1975). Concentrations of atrazine 

in source and finished water at the CWS at Running Gutter 

Brook were less than 0.01 μg/L (fig. 14). This CWS uses slow 

sand filtration, and little information is available about the fate 

of pesticides and other organic contaminants during slow sand 

filtration. At Running Gutter Brook, any periodic blending 

of the source waters did not result in appreciable changes in 

atrazine concentrations.

Several of the CWSs use PAC in varying amounts to 

remove taste- and odor-compounds during parts of the year. In 

addition to controlling taste- and odor-compounds, use of PAC 

has been shown to decrease concentrations of several organic 

compounds including atrazine in source water (Miltner 

and others, 1989; Duguet and others, 1994; Westerhoff and 

others, 2005). The seasonal use of PAC may help explain the 

observed pattern at the Neuse River site, where source- and 
Figure 15. Concentrations of selected anthropogenic organic 

compounds in samples collected during the second phase of 

sampling, June 2004–August 2005, showed A, small (atrazine); 

B, large (fipronil); and C, moderate (diuron) amounts of change 

from source to finished water.

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

CONCENTRATION IN FINISHED WATER, IN MICROGRAMS PER LITER

CONCENTRATION IN SOURCE WATER, 

IN MICROGRAMS PER LITER

0.001 0.01 0.1 1 10

Atrazine

Diuron

EXPLANATION

Chattahoochee River

Neuse River

Running Gutter Brook

Potomac River

Elm Fork Trinity River

White River

Clackamas River

Note: Nondetections were set to 0.001 microgram per liter

1:1

1:1

A

B

Fipronil

1:1

C

34 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

finished-water concentrations of atrazine were similar for 

samples from July to December of 2004 (fig. 16). In samples 

collected between February and May 2005, however, concentrations of atrazine in finished water were substantially lower 

than those in source water, which could be the result of the 

seasonal use of PAC. The relative decrease in atrazine concentrations varied at this CWS, and differences in the decrease 

could be related to several factors. The efficacy of PAC can 

be affected by the dose, contact time, and amount and type of 

natural organic matter in the source water (Duguet and others, 

1994; Snyder and others, 2003).

Concentrations of atrazine were lower in finished water 

than in source water in all sample pairs from the Elm Fork 

Trinity River site and in most sample pairs collected from the 

White River site (fig. 16). The Elm Fork Trinity River CWS 

uses ozone as a preliminary water-treatment step (table 2), 

which has been shown to reduce concentrations of atrazine in 

drinking water, with deethylatrazine identified as one of the 

principal by-products (Adams and Randtke, 1992; Verstraeten 

and others, 2002). Deethylatrazine concentrations at this site 

were higher in finished-water than in source-water samples 

(data not shown). Generally, atrazine concentrations in 

finished water were lower than in source water at the White 

River CWS. Some of the difference in concentration may be 

related to the use of PAC during parts of the year as well as 

intermittent blending of surface water with ground water to 

supplement supply.

These results for atrazine highlight the need to monitor 

and characterize the quality of source water used for drinking water. Understanding how compounds move through the 

hydrologic system and the factors that affect their occurrence 

can contribute to the effective management of drinking-water 

quality. In addition, characterizing the occurrence of the 

compounds not typically analyzed in finished water may 

lead to the development of treatment technologies for their 

removal.

Comparison to Human-Health Benchmarks

Annual mean concentrations of all compounds detected 

in finished water were less than their human-health benchmarks. More than one-half of the most commonly detected 

compounds have a human-health benchmark for comparison. Annual mean concentrations for most of the commonly 

detected compounds were two to five orders of magnitude less 

than their human-health benchmarks (fig. 17A). Two disinfection by-products had annual mean concentrations within 

a factor of 10 (BQ greater than 0.1) of the MCL for total 

trihalomethanes (fig. 17A). Chloroform was present in finished 

water at all CWSs with annual mean BQ values between 

0.1 and 0.3. Annual mean concentrations for bromodichloromethane were within a factor of 10 of the MCL at three 

CWSs. Concentrations of bromoform and dibromochloromethane were considerably less than chloroform, and at all 

of the CWSs the annual mean of the sum of these disinfec-
Figure 16. Changes in atrazine concentrations in source water usually were reflected in the finished-water quality in samples 

collected at six sites during the second phase of sampling, June 2004–August 2005.

Running Gutter Brook

Neuse River

Chattahoochee River Elm Fork Trinity River

White River

Potomac River

Source water Finished water

EXPLANATION

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

0.001

0.01

0.1

1

10

CONCENTRATION, IN MICROGRAMS PER LITER

6/1/2004 10/16/2004 3/2/2005 7/17/2005 12/1/2005 6/1/2004 10/16/2004 3/2/2005 7/17/2005 12/1/2005

Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 35
0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10

BQ BQ

Chattahootchee River

Neuse River

Running Gutter Brook

Truckee River

Potomac River

Elm Fork Trinity River

White River

Clackamas River

SINGLE-SAMPLE MAXIMUM BENCHMARK QUOTIENT (BQ) VALUES

Chloroform*

Bromodichloromethane*

Bromoform*

Dibromochloromethane*

Benomyl

Benzene*

m- and p-Xylene*

Toluene*

Ethylbenzene*

o-Xylene*

Atrazine*

Simazine*

Metolachlor

Prometon

2-Hydroxyatrazine

2,4–D*

Diuron

Bentazon

Acetochlor

Terbuthylazine

MCPA

Alachlor*

Triclopyr

Carbaryl

Diazinon

Chloromethane

cis-1,2-Dichloroethene*

Perchloroethene*

Methylene chloride

Acetone

Carbon tetrachloride*

Fungicide

Gasolinerelated

compounds

DBPs

Herbicides

and 

degradates

Insecticides

Organic synthesis

Solvents

Note: Isomers of xylene are compared to the MCL of 10,000 micrograms per liter for total xylenes, 

and disinfection by-products are compared to the MCL of 80 micrograms per liter for the sum 

of the four trihalomethanes

A

B

0.000001 0.00001 0.0001 0.001 0.01 0.1 1 10

Chloroform*

Bromodichloromethane*

Bromoform*

Dibromochloromethane*

Benomyl

Benzene*

m- and p-Xylene*

Toluene*

Ethylbenzene*

o-Xylene*

Atrazine*

Simazine*

Metolachlor

Prometon

2-Hydroxyatrazine

2,4–D*

Diuron

Bentazon

Acetochlor

Terbuthylazine

MCPA

Alachlor*

Triclopyr

Carbaryl

Diazinon

Chloromethane

cis-1,2-Dichloroethene*

Perchloroethene*

Methylene chloride

Acetone

Carbon tetrachloride*

Fungicide

Gasolinerelated

compounds

DBPs

Herbicides

and 

degradates

Insecticides

Organic synthesis

Solvents

BQ BQ

ANNUAL MEAN BENCHMARK QUOTIENT (BQ) VALUES

EXPLANATION

* Regulated compound

DBP Disinfection by-product

MCPA 2-methyl-4-chlorophenoxyacetic acid

Figure 17. During the second phase of sampling, June 2004–August 2005, A, annual mean concentrations 

of commonly detected anthropogenic organic compounds in finished-water samples were less than humanhealth benchmarks; and B, maximum concentrations in single samples from each site generally were lower 

than human-health benchmarks.

36 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams
Consumer Confidence Reports and SourceWater Quality Assessments

Since 1999, the U.S. Environmental Protection Agency (USEPA) has required water suppliers to 

provide annual drinking-water quality reports called 

Consumer Confidence Reports (CCRs) to their customers (http://www.epa.gov/safewater/ccr/ccrfact.html). 

CCRs are the centerpiece of the right-to-know provisions of the 1996 Amendments to the Safe Drinking 

Water Act. Each CCR provides consumers with fundamental information about their drinking water including 

(1) the source of the drinking water, (2) a brief summary of the susceptibility to contamination of the local 

drinking-water source, (3) the concentrations (or range 

of concentrations) of any contaminants found in local 

drinking water, as well as their USEPA Maximum Contaminant Levels (MCLs), which are legally enforceable 

drinking-water standards and are the highest allowed 

concentrations of contaminants in drinking water, and 

(4) telephone numbers for additional sources of information.

I

nformation in CCRs is specific to a particular water 

utility. Water utilities analyze finished-water samples 

primarily for regulated compounds using USEPA 

analytical methods for compliance monitoring. In 

contrast, Source Water-Quality Assessments (SWQAs) 

performed by the U.S. Geological Survey (USGS) are 

not conducted for compliance monitoring but are used 

to characterize the water quality of selected rivers and 

aquifers at the point of withdrawal of a CWS supply. 

As part of SWQAs, both source- and finished-water 

samples are analyzed using USGS analytical methods. 

Analytical methods used in SWQAs include many more 

compounds and typically have lower analytical reporting levels than those used in USEPA analytical methods; 

therefore, compound detection frequencies in SWQA 

reports may be higher than those reported in CCRs.

Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 37

tion by-products was less than the MCL of 80 μg/L for total 

trihalomethanes in all finished-water samples. Atrazine was 

the only other compound for which annual mean concentrations were within a factor of 10 of the MCL. The annual mean 

BQ values were between 0.1 and 0.3 at the CWSs on the Elm 

Fork Trinity and White Rivers (fig. 17A), and the annual mean 

concentrations of atrazine were 0.46 and 0.72 μg/L, respectively.

Even when single-sample maximum concentrations are 

considered, few compounds were detected in finished water 

at concentrations within a factor of 10 of their human-health 

benchmarks (fig. 17B). Of the commonly detected compounds, 

disinfection by-products and herbicides were the only primary 

use groups with BQmax values greater than 0.1. One detection of atrazine at 3.4 μg/L in a finished-water sample from the 

CWS on the White River was greater than its MCL (3 μg/L). 

As observed in source-water samples, some herbicides are 

present in surface water at relatively high concentrations 

seasonally following their use; however, concentrations often 

decrease subsequently. As a result, annual mean concentrations generally were about an order of magnitude less than the 

maximum detected concentration.

Concentrations of compounds detected in fewer than 

10 percent of samples were almost always lower than their 

human-health benchmarks (Appendix 2). Only one infrequently detected compound in finished water was measured in 

a single sample at a concentration greater than a human-health 

benchmark. Benzo[a]pyrene has an MCL of 0.2 μg/L and was 

detected in only one finished-water sample at a concentration of 0.26 μg/L. Benzo[a]pyrene was not detected in any 

other source- or finished-water samples during either phase of 

sampling.

Mixtures of Compounds

One objective of the comparisons of source and finished 

water was to evaluate potential differences in the frequency 

and complexity of mixtures of organic compounds. Both 

source- and finished-water samples usually contained mixtures 

of two or more compounds, and about one-half of samples 

of both source and finished water contained 14 or more 

compounds. Because disinfection by-products were formed 

during water treatment, finished water had a higher percentage of samples with mixtures than did source water when 

fewer than 15 compounds were detected (fig. 18). A smaller 

percentage of finished-water samples, however, contained 

more than 15 compounds compared to source water. Sourcewater samples containing mixtures with large numbers of 

compounds generally were from watersheds that had more 

agricultural and urban land use (fig. 8), and samples from 

these sites included larger numbers of compounds in source 

water rather than in finished water. Changes in concentration 

(transformation) of some compounds as a result of water treatment (for example, fipronil and its degradates) may account, 

in part, for the higher percentage of source-water samples 

having mixtures with more compounds than finished water.

As discussed previously in relation to mixture occurrence 

in source water, the potential human-health significance of the 

frequent presence of mixtures of organic compounds remains 

largely unknown. The frequent occurrence of mixtures in both 

source- and finished-water samples points to a need for identifying which specific combinations of compounds occur most 

commonly and which may be a potential concern for human 

health. Identification of specific combinations of compounds 

would provide initial perspective on co-occurrence that may 

be important as more is learned about sources and potential 

health effects of mixtures. Again, these are important research 

topics, but are beyond the scope of this report.
Figure 18. About one-half of source- and finished-water samples 

collected during the second phase of sampling, June 2004–August 

2005, contained mixtures of 14 or more compounds.

0 10 20 30 40 50

NUMBER OF COMPOUNDS IN A SAMPLE

0

20

40

60

80

100

Source water

Finished water

PERCENTAGE OF SAMPLES WITH EQUAL OR GREATER 

NUMBER OF COMPOUNDS

USEPA Drinking Water Levels of 

Comparison for Atrazine and its Degradates 

in Community Water Systems

As part of the reregistration of atrazine in 2003, the U.S. Environmental Protection Agency developed 

drinking-water levels of comparison (DWLOCs) for 

the sum of atrazine and its three chlorinated degradates 

(deethylatrazine, deisopropylatrazine, and deethyldeisopropyl atrazine), referred to as total chlorotriazines 

(TCT), in source water for a community water system 

(CWS). DWLOCs are the maximum concentrations in 

drinking water that, when considered together with other 

dietary exposure, do not exceed a level of concern.

The DWLOC for TCT is a 90-day moving average 

of 37.5 micrograms per liter (μg/L) if source-water 

samples are collected from CWSs at least weekly during the growing season (biweekly the remainder of the 

year); the DWLOC for TCT is a 90-day moving average 

of 12.5 μg/L if monitoring during the growing season is 

less frequent (U.S. Environmental Protection Agency, 

2003). Concentrations greater than these DWLOCs 

indicate the need for further analysis and monitoring.

Currently (2008), the USEPA is transitioning away from the use of DWLOCs and developing a 

probabilistic approach to assessing exposure and risk 

from TCT in drinking water. This probabilistic approach 

will incorporate the same methodologies used in other 

cumulative risk assessments for organophosphate and 

N-methyl carbamate pesticides (Catherine Eiden, U.S. 

Environmental Protection Agency, oral commun., 2008).

Although the probabilistic approach will change future assessments, concentrations measured in 

this study are compared to the existing DWLOC values 

as a preliminary evaluation. Samples were collected 

less frequently than weekly during the growing season 

and less frequently than biweekly during the remainder of the year at all Source Water-Quality Assessment 

(SWQA) sites, so 90-day moving average concentrations 

of TCT were compared to the 12.5 μg/L benchmark for 

evaluations of all sites. None of the SWQA sites had 

a maximum 90-day average greater than 12.5 μg/L. 

The maximum 90-day average concentration of TCT 

in source water was at the White River, Indiana, which 

had a maximum of 6.4 μg/L during the first phase and 

2.1 μg/L during the second phase of the SWQA sampling.

38 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

Summary and Conclusions

Source Water-Quality Assessments (SWQAs) by the 

U.S. Geological Survey’s National Water-Quality Assessment 

(NAWQA) Program characterize the quality of source and 

finished water of selected community water systems (CWSs) 

that use streams or aquifers for drinking water. SWQA studies 

of CWSs that withdraw water from streams, the subject of this 

report, were conducted in two phases, with sample collection 

lasting about a year during each of the phases. During the first 

phase of sampling (October 2002–March 2004), nine streams 

that are used as a source of drinking water were sampled about 

monthly for analysis of 258 anthropogenic organic compounds 

over about a year’s time to characterize the quality of these 

source waters. Eight of these sites were sampled for a second 

year during the second phase of sampling (June 2004–August 

2005), and corresponding finished-water samples (after treatment and before distribution) were collected monthly to characterize the extent to which compounds detected in the source 

water were present in the finished water. Three additional 

herbicides and 16 degradates were analyzed in samples from a 

subset of sites during both sampling phases.

The contributing watersheds to these streams range in 

size from 1 to about 11,500 square miles, but seven were 

between about 480 and 2,500 square miles. Four of the watersheds can be characterized as undeveloped with relatively little 

urban land use (less than 5 percent) or agricultural land use 

(less than 25 percent); three watersheds have mixed land use; 

and two watersheds have greater than 50 percent agricultural 

land use. The CWSs withdrawing from these streams range in 

size from small to very large, serving from about 3,000 people 

to 2 million people. Water treatment at most of the CWSs is 

conventional, which typically includes the steps of coagulation, flocculation, sedimentation, filtration, and disinfection. 

One of the CWSs uses slow sand filtration, a second uses 

ozone as a preliminary treatment step, and a third uses direct 

filtration. Four of the CWSs use powdered activated carbon 

intermittently for taste- and odor-issues or removal of organic 

compounds.
Summary and Conclusions 39

Of the 258 organic compounds analyzed at all sites, 

134 compounds were detected at least once in source-water 

samples collected during the first phase of sampling, but 

many of these compounds were detected infrequently and at 

low concentrations—less than 0.1 microgram per liter (μg/L). 

A total of 119 compounds were not detected in any sample. 

Annual mean concentrations of all compounds detected in 

source water were less than available human-health benchmarks. Maximum single-samples concentrations also were 

almost always less than benchmarks. Atrazine, one of the 

most heavily used herbicides in the Nation, was the only 

compound detected in source-water samples at a concentration (20.5 μg/L) greater than its Maximum Contaminant Level 

(MCL) of 3 μg/L for drinking water. The annual mean concentration for atrazine in source water at this site was 2.2 μg/L. 

Instantaneous high concentrations in source water do not 

represent a violation of an MCL, which is based on an annual 

mean concentration in finished water. Elevated concentrations 

of atrazine and several other herbicides in source water generally were associated with their application during the spring in 

watersheds with agricultural land use. Acetochlor and dieldrin 

were each detected once in source water at concentrations 

greater than their respective Health-Based Screening Level 

concentration.

Chloroform was the most commonly detected compound, 

in about 70 percent of all samples and at eight of the nine 

sites. It was detected in every sample throughout the year 

at sites on the Elm Fork Trinity, Neuse, Potomac, and 

White Rivers and at Running Gutter Brook. The fragrance 

compounds acetyl hexamethyl tetrahydronaphthalene (AHTN) 

and hexahydrohexamethycyclopentabenzopyran (HHCB) 

also were commonly detected in about 50 percent of samples 

and at as many as eight of the stream sites. Findings for these 

compounds and chloroform indicate an association between 

their occurrence and upstream wastewater discharges. The 

largest number of detections of these compounds was found at 

five sites that included major municipal wastewater discharges 

(greater than 1 million gallons per day) upstream from the 

sampling location. Four sites without major wastewater 

discharges upstream had relatively few or no detections of 

these compounds with the exception of Running Gutter Brook 

where chloroform was detected in every sample. Detections 

of chloroform in every sample from Running Gutter Brook, 

which does not receive any major wastewater discharge, 

demonstrate that these compounds can have multiple sources, 

and an understanding of local hydrology and sources of 

contaminants is needed to fully characterize source-water 

quality.

Herbicides and their degradates were among the most 

commonly detected compounds in source water. The most 

commonly detected herbicides—simazine, atrazine and 

its degradates (deethylatrazine and deisopropylatrazine), 

metolachlor, prometon, and 2,4–D—were detected in about 

50 percent or more of samples at six of the nine sites. 

Degradates of these herbicides, as well as diruon, generally were detected at concentrations similar or greater than 

concentrations of the parent compounds. Some herbicides, for 

example acetochlor and alachlor, were detected commonly 

in one or two watersheds, likely a result of corn cultivation 

in these watersheds. The herbicides detected in these source 

waters in this study also were among the most commonly 

detected herbicides in streams across the Nation sampled by 

the NAWQA Program between 1992 and 2001.

Three insecticides—diazinon, fipronil, and carbaryl—

were detected most commonly in samples from five watersheds with overall detection frequencies of 39, 29, and 

15 percent, respectively. Both diazinon and carbaryl were 

among the most commonly detected insecticides in streams 

sampled by the NAWQA Program between 1992 and 2001, 

and detection frequencies were highest in watersheds characterized as urban. No insecticides were detected in any samples 

from sites in this study with less than 1 percent urban land 

use in their watersheds. Notably, the detection frequency of 

diazinon in source water decreased between samples collected 

during 2002–04 and samples collected during 2004–05, probably because of the phase out of its use in December 2004.

During the first phase of sampling, source-water 

samples typically contained mixtures of two or more 

compounds: about three-quarters of source-water samples 

contained 5 compounds, and about one-half contained at least 

13 compounds. The most commonly detected compounds 

in mixtures were those individual compounds detected 

most commonly, such as chloroform and herbicides and 

their degradates. The number of compounds and the total 

concentration of compounds detected in a sample generally 

increased as the amount of urban and agricultural land use 

in the watershed increased. Samples from sites in undeveloped watersheds (Cache la Poudre, Clackamas, and Truckee 

Rivers and Running Gutter Brook) typically contained 10 

or fewer compounds, with total concentrations of detected 

compounds generally less than 0.5 μg/L. The median number 

of compounds in samples from sites with predominantly agricultural or mixed land use (Chattahoochee, Elm Fork Trinity, 

Neuse, Potomac, and White Rivers) was between 9 and 30, 

with total median concentrations of detected compounds 

between 1 and 4 μg/L.

The comparison between source- and finished-water 

quality in this report is not intended as an evaluation of watertreatment efficacy at these CWSs. Rather, the results from this 

study represent a characterization of how source- and finishedwater quality vary over the course of about a year at eight 

CWSs that use treatment steps typical of many CWSs across 

the county. Finished-water samples were collected at the 

treatment plant following all of the treatment steps and before 

distribution and therefore are not necessarily representative 

of drinking-water quality at the tap (or point of delivery). 

Additional contact time with disinfectants in the distribution 

system may change concentrations of some of the compounds 

detected in the finished water at the sample-collection point. 

It is important to note that conventional water treatment in 

general, and most of the treatment steps used by the CWSs 
40 Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams

sampled, are not specifically designed to remove many of the 

anthropogenic organic compounds monitored in this study.

About two-thirds of the most commonly detected 

compounds in source water had similar detection frequencies in finished water. Concentrations of these compounds 

commonly were lower in finished water than in the corresponding source-water sample, but the amount of change 

for many of these compounds was not large, and typically 

was less than 25 percent. Compounds that were detected at 

similar detection frequencies in both source and finished 

water include the commonly detected herbicides such as 

atrazine, its degradates, and simazine, as well as personalcare and domestic-use compounds such as the fragrances 

HHCB and AHTN. About one-quarter of the most commonly 

detected compounds in source and finished water had detection frequencies in finished water that were about one-half 

or less than the detection frequency in source water. A few 

compounds, including the organophosphate insecticides, 

fipronil, 3,4-dichloroaniline (diuron degradate), and aromatic 

hydrocarbons with one or more methyl groups, typically were 

not present at detectable concentrations in finished water 

although they were detected in source water. The decrease 

in concentration of these compounds likely was the result of 

degradation or transformation as a result of disinfection.

Annual mean concentrations in finished water were less 

than human-health benchmarks. Maximum single-sample 

concentrations also were less than human-health benchmarks 

with two exceptions. Atrazine was detected at a concentration 

of 3.4 μg/L in a finished-water sample from the White River 

CWS. The annual mean concentration of atrazine in finishedwater samples at the CWS on the White River was 0.72 μg/L, 

which is considerably less than the MCL of 3 μg/L. Benzo[a]-

pyrene was detected one time in finished water at a concentration of 0.26 μg/L, which is slightly greater than its MCL 

of 0.2 μg/L. Benzo[a]pyrene was not detected in any sourcewater samples. All other maximum concentrations in finished 

water were less than applicable human-health benchmarks.

Although water-treatment steps used by these eight 

CWSs differ somewhat, large differences (greater than 

75 percent) in the amount of change in concentration between 

source water and finished water generally were not observed 

for those compounds with similar detection frequencies in 

source and finished water. The comparison of changes in 

concentration is limited because of other factors that may have 

affected findings, such as sampling timing and analytical error 

for compounds present at concentrations near the reporting 

level.

Changes in source-water quality during the year usually 

are reflected in finished-water quality. For compounds that 

were present in both source- and finished-water samples, 

varying concentrations in source water typically resulted in 

corresponding concentrations in finished water, although 

concentrations commonly were lower in finished water 

than in source water. At some CWSs, the amount of change 

between source and finished water varied. These differences 

in the amount of change in concentration from source to 

finished water may reflect changes in water treatment at the 

CWSs, including the occasional use of powdered activated 

carbon to remove taste- and odor-compounds or other organic 

compounds.

Source- and finished-water samples typically contained 

mixtures of two or more compounds, and about 50 percent 

of both sample types contained 14 or more compounds. The 

frequent occurrence of a number of compounds typically at 

concentrations less than applicable human-health benchmarks 

in source water and the associated finished water has several 

implications, one of which is the importance of source-water 

characterization. For these eight CWSs, which use treatment 

steps typical of many water systems across the Nation that 

withdraw water from streams, concentrations of many of the 

most commonly occurring compounds in source water did not 

change appreciably following treatment. Understanding gained 

from resource assessments about how organic compounds 

move through the hydrologic system, and factors that affect 

their occurrence, may provide water-resource managers with 

information that can be used to minimize the effect of these 

contaminants on drinking-water quality.

Results from these studies also indicate that although 

concentrations of compounds detected typically were considerably less than human-health benchmarks, the frequent 

occurrence of mixtures in finished waters points to a need for 

indentifying mixtures that are most common and most likely 

to have potential human-health effects. Also, the importance of 

degradates in addressing the potential risk of exposure to the 

parent compounds has begun to be incorporated into humanhealth benchmarks, for example atrazine and its degradates. 

Yet more information is needed to understand the formation, 

fate, and transport of degradates in the environment as well 

as the formation of degradates and transformation products 

during water treatment.

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Appendixes
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Disinfection by-products Chloroform3 67–66–3 147 69.4 0.024 2.86 15.6 MCL 

Bromodichloromethane3 75–27–4 147 20.4 .028 .51 3.4 MCL Dibromochloromethane3 124–48–1 147 4.1 .1 .17 .7 MCL Bromoform3 75–25–2 147 .7 .1 .098 E ND MCL 

Fumigant-related compounds 1,4-Dichlorobenzene4 106–46–7 147 9.5 0.034 0.083 E ND MCL 

1,2-Dichloropropane 78–87–5 147 1.4 .029 .016 E ND MCL 1,2-Dibromoethane 106–93–4 147 ND .036 ND ND MCL 1,2-Dibromo-3-chloropropane 96–12–8 147 ND .51 ND ND MCL 1,3-Dichloropropane5 142–28–9 147 ND .06 ND ND -- 2,2-Dichloropropane5 594–20–7 147 ND .05 ND ND -- Bromomethane5 74–83–9 147 ND .33 ND ND HBSL cis-1,3-Dichloropropene5,6 10061–01–5 147 ND .05 ND ND HBSL trans-1,3-Dichloropropene5,6 10061–02–6 147 ND .09 ND ND HBSL 

Fungicides Benomyl 17804–35–2 145 12.4 0.022 0.12 E 0.7 HBSL 

Metalaxyl 57837–19–1 145 4.8 .007 .015 ND HBSL Pentachlorophenol 87–86–5 145 3.4 2 .32 E 2.1 MCL Myclobutanil 88671–89–0 146 2.7 .033 .021 ND HBSL Propiconazole -- 145 .7 .01 .042 ND HBSL Chlorothalonil 1897–45–6 145 ND .035 ND ND HBSL Iprodione 36734–19–7 145 ND .026 ND ND HBSL 

Gasoline hydrocarbons, oxygenates, and oxygenate degradates Methyl tert-butyl ether (MTBE)4 1634–04–4 147 36.1 0.1 3.44 18.4 -- 

Benzene 71–43–2 130 30.8 .021 .46 4.6 MCL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued

Toluene 108–88–3 130 17.7 0.02 1.98 9.2 MCL m- and p-Xylene 106–42–3; 

108–38–3

147 12.9 .06 1.40 6.8 MCL 

1,2,4-Trimethylbenzene5 95–63–6 147 11.6 .0556 .52 3.4 -- tert-Butyl alcohol 75–65–0 145 11.0 1 1.05 11.0 -- o-Xylene 95–47–6 147 10.9 .038 .55 4.8 MCL Ethylbenzene 100–41–4 147 8.8 .03 .36 .7 MCL 1-Ethyl-2-methylbenzene 

(o-Ethyl toluene)

611–14–3 147 6.8 .038 .12 .7 -- 

1,3,5-Trimethylbenzene 108–67–8 147 5.4 .044 .15 .7 -- 1,2,3-Trimethylbenzene 526–73–8 147 3.4 .09 .11 E .7 -- tert-Amyl methyl ether 

(TAME)

994–05–8 147 2.0 .04 .088 E ND -- 

1,2,3,5-Tetramethylbenzene 527–53–7 147 1.4 .18 .072 E ND -- Styrene4 100–42–5 147 1.4 .042 .050 E ND MCL 1-Methylnaphthalene 90–12–0 145 .7 .5 .022 E ND -- 2-Methylnaphthalene4 91–57–6 145 .7 .5 .035 E ND HBSL Isopropylbenzene 98–82–8 147 .7 .038 .022 E ND HBSL n-Butylbenzene 104–51–8 147 .7 .14 .016 E ND -- 1,2,3,4-Tetramethylbenzene 488–23–3 147 ND .14 ND ND -- 2,6-Dimethylnaphthalene 581–42–0 145 ND .5 ND ND -- Diisopropyl ether (DIPE) 108–20–3 147 ND .1 ND ND -- Naphthalene5 91–20–3 147 ND .5 ND ND -- p-Isopropyltoluene5 99–87–6 147 ND .08 ND ND -- sec-Butylbenzene 135–98–8 147 ND .06 ND ND -- tert-Amyl alcohol 

(2-Methyl-2-butanol)

75–85–4 145 ND 1 ND ND -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued Ethyl tert-butyl ether (ETBE) 637–92–3 147 ND 0.03 ND ND -- 

tert-Butylbenzene 98–06–6 147 ND .08 ND ND -- 

Herbicides and herbicide degradates Simazine 122–34–9 146 67.1 0.005 3.23 28.1 MCL 

Atrazine 1912–24–9 146 63.7 .007 20.1 26.7 MCL Deethylatrazine5 (DEA) 6190–65–4 147 52.4 .014 .54 E 10.9 -- Metolachlor5 51218–45–2 146 51.4 .006 2.93 8.8 HBSL Prometon 1610–18–0 146 49.3 .01 .054 ND HBSL Deisopropylatrazine (DIA) 1007–28–9 145 49.0 .08 .40 4.1 -- 2,4–D 94–75–7 145 42.8 .038 4.78 15.9 MCL 3,4-Dichloroaniline 95–76–1 146 40.4 .0045 .06 ND -- 2-Hydroxyatrazine 2163–68–0 145 40.0 .032 1.65 E 22.1 HBSL Diuron4 330–54–1 145 30.3 .016 .44 4.1 HBSL MCPA 94–74–6 145 21.4 .07 .47 4.8 HBSL Alachlor 15972–60–8 146 15.1 .005 .087 ND MCL Triclopyr 55335–06–3 145 12.4 .026 .21 1.4 HBSL Acetochlor 34256–82–1 146 12.3 .006 4.32 3.4 HBSL Bentazon 25057–89–0 145 11.7 .024 .10 E .7 HBSL Terbuthylazine 5915–41–3 146 11.6 .0083 .017 ND HBSL Tebuthiuron 34014–18–1 147 10.9 .026 .028 ND HBSL Pendimethalin 40487–42–1 146 8.9 .022 .038 ND HBSL Imazaquin 81335–37–7 145 8.3 .036 .15 E .7 HBSL Metribuzin5 21087–64–9 146 8.2 .028 .078 ND HBSL Dicamba 1918–00–9 145 6.9 .036 .67 2.8 HBSL 2,4–D methyl ester 1928–38–7 145 5.5 .19 .65 3.4 -- Imazethapyr 81335–77–5 145 5.5 .038 .13 E 1.4 HBSL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Herbicides and herbicide degradates—Continued

Propyzamide 23950–58–5 146 5.5 0.004 0.010 ND HBSL Hexazinone 51235–04–2 80 8.8 .026 .018 ND HBSL Chlorimuron-ethyl 90982–32–4 145 4.1 .032 .20 E 0.7 HBSL 4-Chloro-2-methylphenol 1570–64–5 146 4.1 .005 .013 E ND -- Flumetsulam 98967–40–9 145 3.4 .04 .052 E ND HBSL Bromacil 314–40–9 145 2.8 .018 .093 E ND HBSL Dichlorprop 120–36–5 145 2.8 .036 .070 ND HBSL Sulfometuron-methyl 74222–97–2 145 2.8 .09 .024 ND -- 2-Ethyl-6-methylaniline 24549–06–2 146 2.1 .01 .002 E ND -- Clopyralid 1702–17–6 145 2.1 .067 .046 ND -- Metsulfuron methyl4 74223–64–6 145 2.1 .067 .09 E ND HBSL Dacthal 1861–32–1 146 2.1 .014 .002 E ND HBSL Trifluralin 1582–09–8 146 2.1 .009 .005 E ND HBSL Siduron 1982–49–6 145 1.4 .02 .013 E ND -- Acifluorfen 50594–66–6 145 .7 .028 .011 ND HBSL Bromoxynil 1689–84–5 145 .7 .044 .004 E ND HBSL Deethyldeisopropyl atrazine 

(DDA)

3397–62–4 144 .7 .04 .16 E .7 -- 

Dinoseb 88–85–7 145 .7 .038 .004 E ND MCL Diphenamid 957–51–7 145 .7 .01 .010 E ND HBSL Nicosulfuron 111991–09–4 145 .7 .04 .087 E ND HBSL Norflurazon 27314–13–2 145 .7 .02 .004 E ND HBSL Oryzalin 19044–88–3 145 .7 .023 .065 E ND HBSL Picloram 1918–02–1 145 .7 .032 .16 .7 MCL Terbacil 5902–51–2 145 .7 .026 .01 E ND HBSL Metolachlor ethane sulfonic 

acid8

-- 39 69.2 .02 2.07 66.7 -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Herbicides and herbicide degradates—Continued Metolachlor oxanilic acid8 -- 39 66.7 0.02 1.47 43.6 -- 

Alachlor ethane sulfonic acid8 -- 39 59.0 .02 .24 33.3 -- Acetochlor ethane sulfonic acid8 -- 39 41.0 .02 1.42 35.9 -- Alachlor oxanilic acid8 -- 39 41.0 .02 .13 7.7 -- Acetochlor oxanilic acid8 -- 39 38.5 .02 1.74 30.8 -- Acetochlor sulfynilacetic acid8 -- 39 25.6 .02 1.22 17.9 -- Dimethenamid ethane sulfonic acid8 -- 39 12.8 .02 .11 2.6 -- Alachlor sulfynilacetic acid8 140939–16–8 39 5.1 .02 .11 2.6 -- Dimethenamid oxanilic acid8 -- 39 2.6 .02 .05 ND -- Propachlor8 1918–16–7 0 -- .02 -- -- HBSL 2-Chloro-2,6-diethylaceta- nilide 6967–29–9 146 ND .0065 ND ND -- Benfluralin 1861–40–1 146 ND .01 ND ND HBSL Cycloate 1134–23–2 145 ND .014 ND ND HBSL Prometryn 7287–19–6 146 ND .0059 ND ND HBSL Linuron5 330–55–2 145 ND .014 ND ND HBSL MCPB 94–81–5 145 ND .1 ND ND HBSL 2,4–DB 94–82–6 145 ND .02 ND ND HBSL Fluometuron 2164–17–2 145 ND .016 ND ND HBSL Propham 122–42–9 145 ND .03 ND ND HBSL Neburon 555–37–3 145 ND .012 ND ND -- Fenuron 101–42–8 145 ND .1 ND ND -- Dacthal monoacid 887–54–7 145 ND .028 ND ND -- Chloramben, methyl ester 7286–84–2 145 ND .024 ND ND -- Dimethenamid 87674–68–8 6 ND .02 ND ND -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Herbicides and herbicide degradates—Continued

3(4-Chlorophenyl)-1-methyl 

urea

5352–88–5 145 ND 0.036 ND ND -- 

Bensulfuron-methyl 83055–99–6 145 ND .018 ND ND HBSL Flufenacet ethane sulfonic 

acid8

-- 39 ND .02 ND ND -- 

Flufenacet8 142459–58–3 6 ND .02 ND ND -- Flufenacet oxanilic acid8 -- 39 ND .02 ND ND -- Propachlor ethane sulfonic 

acid8

-- 39 ND .02 ND ND -- 

Propachlor oxanilic acid8 -- 39 ND .02 ND ND -- Alachlor ethane sulfonic acid 

2nd amide8

-- 11 ND .02 ND ND -- 

Acetochlor/metolachlor ethane 

sulfonic acid 2nd amide8

--

6

ND .02 ND ND -- 

2,6-Diethylaniline 579–66–8 146 ND .006 ND ND -- 

Insecticide and insecticide degradates

Diazinon 333–41–5 146 39.0 0.005 0.086 ND HBSL Fipronil 120068–37–3 146 29.5 .016 .016 ND -- Carbaryl 63–25–2 145 15.2 .018 .065 E ND HBSL Desulfinylfipronil -- 146 7.5 .012 .006 ND -- 1-Naphthol 90–15–3 146 6.2 .0882 .014 E ND -- Chlorpyrifos 2921–88–2 146 6.2 .005 .008 ND HBSL Fipronil sulfide 120067–83–6 146 6.2 .013 .007 ND -- Dichlorvos 62–73–7 146 4.1 .006 .012 ND HBSL Imidacloprid 138261–41–3 145 2.8 .023 .037 ND HBSL Propoxur 114–26–1 145 2.8 .008 .006 E ND HBSL Carbofuran 1563–66–2 145 2.1 .016 .012 ND MCL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Insecticide and insecticide degradates—Continued Malathion 121–75–5 146 2.1 0.027 0.018 E ND HBSL 

Dimethoate 60–51–5 146 1.4 .0061 .009 E ND HBSL Fipronil sulfone 120068–36–2 146 1.4 .024 .008 E ND -- Phosmet 732–11–6 141 .7 .0079 .007 E ND HBSL Azinphos-methyl 86–50–0 146 .7 .05 .016 E ND HBSL Dieldrin 60–57–1 146 .7 .009 .004 E ND HBSL 3-Hydroxycarbofuran 16655–82–6 145 ND .008 ND ND -- 3-Ketocarbofuran 16709–30–1 145 ND 1.5 ND ND -- Aldicarb 116–06–3 145 ND .15 ND ND HBSL Aldicarb sulfoxide 1646–87–3 145 ND .1 ND ND HBSL Aldicarb sulfone 1646–88–4 145 ND .018 ND ND HBSL Azinphos-methyl-oxon 961–22–8 145 ND .042 ND ND -- Bendiocarb 22781–23–3 145 ND .08 ND ND HBSL Chlorpyrifos, oxygen analog 5598–15–2 146 ND .0562 ND ND -- cis-Permethrin 54774–45–7 146 ND .006 ND ND HBSL Cyfluthrin 68359–37–5 146 ND .053 ND ND HBSL Cypermethrin 52315–07–8 146 ND .046 ND ND HBSL Desulfinylfipronil amide -- 146 ND .029 ND ND -- Diazinon, oxygen analog 962–58–3 146 ND .006 ND ND -- Dicrotophos 141–66–2 144 ND .0843 ND ND HBSL Ethion 563–12–2 146 ND .016 ND ND HBSL Ethion monoxon 17356–42–2 146 ND .021 ND ND -- Fenamiphos 22224–92–6 146 ND .029 ND ND HBSL Fenamiphos sulfone 31972–44–8 146 ND .053 ND ND -- Fenamiphos sulfoxide 31972–43–7 143 ND .04 ND ND -- Fonofos 944–22–9 146 ND .0053 ND ND HBSL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Insecticide and insecticide degradates—Continued

Fonofos oxygen analog 944–21–8 146 ND 0.0029 ND ND -- Isofenphos 25311–71–1 146 ND .011 ND ND HBSL Malaoxon 1634–78–2 146 ND .039 ND ND -- Methidathion 950–37–8 146 ND .0087 ND ND HBSL Methiocarb 2032–65–7 145 ND .034 ND ND HBSL Methomyl 16752–77–5 145 ND .07 ND ND HBSL Oxamyl 23135–22–0 145 ND .05 ND ND MCL Paraoxon-methyl 950–35–6 146 ND .019 ND ND -- Parathion-methyl 298–00–0 146 ND .015 ND ND HBSL Phorate 298–02–2 146 ND .055 ND ND HBSL Phorate oxon 2600–69–3 146 ND .027 ND ND -- Phosmet oxon 3735–33–9 138 ND .0511 ND ND -- Terbufos 13071–79–9 146 ND .017 ND ND HBSL Terbufos-oxygen-analogue 

sulfone

56070–15–6 146 ND .045 ND ND -- 

Manufacturing additives

Tri(2-chloroethyl)phosphate4 115–96–8 145 34.5 0.5 0.14 E 8.3 -- Tris(dichlorisopropyl)phosphate 13674–87–8 145 25.5 .5 .12 E 3.4 -- Tributyl phosphate 126–73–8 118 20.3 .5 .22 E 7.6 -- Tri(2-butoxyethyl)phosphate 78–51–3 145 18.6 .5 .93 18.6 -- Triphenyl phosphate 115–86–6 145 15.9 .5 .077 E ND -- Bisphenol A 80–05–7 145 C 1 C C HBSL 5-Methyl-1H-benzotriazole 136–85–6 145 .7 2 .36 E .7 -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Organic synthesis compounds Anthraquinone 84–65–1 146 6.2 0.5 0.11 E 2.0 -- 

Carbazole4 86–74–8 146 2.1 .5 .051 E ND -- Carbon disulfide4 75–15–0 147 2.0 .038 .034 E ND HBSL Chloromethane 74–87–3 147 1.4 .17 .10 E .7 HBSL 1,1-Dichloropropene5 563–58–6 147 ND .026 ND ND -- 1,2,3-Trichlorobenzene 87–61–6 147 ND .18 ND ND -- 1,2,3-Trichloropropane 96–18–4 147 ND .18 ND ND HBSL 3-Chloro-1-propene 107–05–1 147 ND .5 ND ND -- Acrylonitrile 107–13–1 147 ND .8 ND ND HBSL Ethyl methacrylate (ethyl 2-methyl-2-propano- ate) 97–63–2 147 ND .18 ND ND -- Hexachlorobutadiene5 87–68–3 147 ND .14 ND ND HBSL Iodomethane 74–88–4 147 ND .5 ND ND -- Methyl acrylate (methyl-2-propenoate) 96–33–3 147 ND 1 ND ND -- Methyl acrylonitrile (2-methyl-2-propenenitrile) 126–98–7 147 ND .4 ND ND HBSL Methyl methacrylate (methyl 2-methyl-2-propenoate) 80–62–6 147 ND .2 ND ND HBSL trans-1,4-Dichloro-2-butene 110–57–6 147 ND .7 ND ND -- Vinyl bromide 593–60–2 147 ND .1 ND ND -- Vinyl chloride 75–01–4 147 ND .08 ND ND MCL 

Pavement- and combustion-derived compounds Fluoranthene4 206–44–0 145 6.9 0.5 0.053 E ND HBSL 

Pyrene4 129–00–0 145 6.9 .5 .049 E ND HBSL Anthracene 120–12–7 145 ND .5 ND ND HBSL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Pavement- and combustion-derived compounds—Continued

Benzo[a]pyrene 50–32–8 145 ND 0.5 ND ND MCL Phenanthrene 85–01–8 145 ND .5 ND ND -- 

Personal-care and domestic-use products

HHCB4 1222–05–5 145 53.1 0.5 0.26 E 16.6 -- AHTN4 21145–77–7 145 38.6 .5 .15 E .7 -- Caffeine 58–08–2 132 31.1 .018 .15 2.3 -- Nonylphenol diethoxylate 

(total) (NP2EO)

26027–38–2 144 13.8 5 6.6 E 13.8 -- 

Triethyl citrate (ethyl citrate) 77–93–0 144 13.9 .5 .19 E .7 -- Octylphenol monoethoxylate 

(total)4 (OP2EO)

-- 145 11.0 1 .82 E 11.0 -- 

Octylphenol diethoxylate 

(total)4 (OP1EO)

26636–32–8 145 8.3 1 .25 E 6.2 -- 

Indole 120–72–9 145 6.2 .5 .1 E .7 -- Triclosan 3380–34–5 144 5.6 .5 .1 E .7 -- Methyl salicylate 119–36–8 145 4.1 .5 .39 E 2.8 HBSL Menthol 89–78–1 145 2.8 .5 .16 E .7 -- Camphor4 76–22–2 145 2.8 .5 .026 E ND -- Cotinine 486–56–6 145 2.8 1 .25 E 1.4 -- d-Limonene4 5989–27–5 145 1.4 .5 .064 E ND -- 4-tert-Octylphenol4 140–66–9 145 ND 1 ND ND -- 4-Cumylphenol 599–64–4 145 ND 1 ND ND -- 3-tert-Butyl-4-hydroxy anisole 

(BHA)

25013–16–5 145 ND 5 ND ND -- 

4-n-Octylphenol 1806–26–4 145 ND 1 ND ND -- Acetophenone 98–86–2 145 ND .5 ND ND HBSL Benzophenone 119–61–9 145 R .5 -- -- -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Personal-care and domestic-use products—Continued Bromochloromethane 74–97–5 145 ND 0.12 ND ND HBSL 

Isoborneol 124–76–5 145 ND .5 ND ND -- Isoquinoline 119–65–3 145 ND .5 ND ND -- N,N-diethyl-meta-toluamide (DEET) 134–62–3 145 R .5 -- -- -- Phenol 108–95–2 145 R .5 HBSL para-Nonylphenol (total) 84852–15–3 145 R 5 -- -- -- 

Plant- or animal-derived biochemicals Cholesterol 57–88–5 145 16.6 2 2.5 E 16.6 -- 

beta-Stigmastanol 19466–47–8 145 11.0 2 2.3 E 11.0 -- 3-beta-Coprostanol4 360–68–9 145 10.3 2 1 E 10.3 -- beta-Sitosterol 83–46–5 145 7.6 2 2.3 E 7.6 -- 3-Methyl-1(H)-indole (skatole) 83–34–1 145 3.4 1 .064 E ND -- 

Refrigerants and propellants 1,1,2-Trichloro-1,2,2- trifluoroethane (CFC–113) 76–13–1 147 ND 0.038 ND ND HBSL 

Dichlorodifluoromethane (CFC–12) 75–71–8 147 ND .18 ND ND HBSL Trichlorofluoromethane (CFC–11) 75–69–4 147 ND .08 ND ND HBSL 

Solvents p-Cresol 106–44–5 145 20.0 1 0.39 E 2.8 -- 

Perchloroethene (PCE) 127–18–4 147 17.0 .03 .16 2.7 MCL cis-1,2-Dichloroethene 156–59–2 147 11.6 .024 .54 4.8 MCL Trichloroethene (TCE) 79–01–6 147 6.8 .038 .066 E ND MCL Methylene chloride (dichloromethane)4 75–09–2 147 5.4 .06 .083 E ND MCL 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]

Compound 

(other name or abbreviation) CASRN1

Number 

of 

samples

Detection 

frequency 

(percent)

Laboratory 

reporting level 

(μg/L)

Maximum 

detected 

concentration 

(μg/L)

Detection 

frequency at 

0.1 μg/L assessment level

Type of 

human-he

benchma

Refrigerants and propellants—Continued

n-Propylbenzene 103–65–1 147 4.8 0.042 0.08 E ND -- Acetone 67–64–1 147 1 6 3.8 E 1 HBSL 1,3-Dichlorobenzene 541–73–1 147 .7 .03 .053 E ND HBSL Carbon tetrachloride (tetrachloromethane) 56–23–5 147 .7 .06 .043 E ND MCL Tetrahydrofuran 109–99–9 147 .7 1.2 .32 E .7 -- 1,1,1,2-Tetrachloroethane 630–20–6 147 ND .03 ND ND HBSL 1,1,1-Trichloroethane 71–55–6 147 ND .032 ND ND MCL 1,1,2,2-Tetrachloroethane5 79–34–5 147 ND .03 ND ND HBSL 1,1,2-Trichloroethane 79–00–5 147 ND .04 ND ND MCL 1,1-Dichloroethane 75–34–3 147 ND .035 ND ND -- 1,1-Dichloroethene5 75–35–4 147 ND .024 ND ND MCL 1,2,4-Trichlorobenzene 120–82–1 147 ND .12 ND ND MCL 1,2-Dichlorobenzene 95–50–1 147 ND .048 ND ND MCL 1,2-Dichloroethane 107–06–2 147 ND .13 ND ND MCL 2-Chlorotoluene 95–49–8 147 ND .04 ND ND HBSL 2-Hexanone 591–78–6 147 ND .4 ND ND -- 4-Chlorotoluene 106–43–4 147 ND .05 ND ND HBSL Bromobenzene5 108–86–1 147 ND .028 ND ND -- Chlorobenzene 108–90–7 147 ND .028 ND ND MCL Chloroethane 75–00–3 147 ND .12 ND ND -- Dibromomethane 74–95–3 147 ND .05 ND ND -- Diethyl ether 

(1,1’-oxybisethane)

60–29–7 147 ND .08 ND ND HBSL 

Hexachloroethane 67–72–1 147 ND .14 ND ND HBSL Isophorone 78–59–1 145 R .5 -- -- HBSL Methyl acetate 79–20–9 147 ND .43 ND ND -- 
Appendix 1. Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collected sampling, October 2002–March 2004.—Continued [Compounds within each primary-use category are listed in order from highest to lowest detection frequency; CASRN, Chemical Abstracts Service Registry Number; E, estimatetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Healthnot detected; μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored] Compound (other name or abbreviation) CASRN1 Number of samples Detection frequency (percent) Laboratory reporting level (μg/L) Maximum detected concentration (μg/L) Detection frequency at 0.1 μg/L assess- ment level Type of human-he

benchma

Refrigerants and propellants—Continued Methyl ethyl ketone (MEK) 78–93–3 147 ND 2 ND ND HBSL 

Methyl isobutyl ketone (4-methyl-2-pentanone; MIBK) 108–10–1 147 ND .37 ND ND -- trans-1,2-Dichloroethene 156–60–5 147 ND .032 ND ND MCL 

1This report contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. The CAS recommends the verification of the CASRNs th2HBSL values shown for carcinogens represent the low end (10-6) of the HBSL range (10-6 to 10-4 cancer risk level) (Toccalino, Norman, and others, 2006). 3The U.S. Environmental Protection Agency MCL of 80 μg/L is for the sum of the concentrations of four trihalomethanes. 4Compound detected in less than 5 percent of field blanks. 5Compound on U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005). 6The sum of concentrations from cis-1,3- and trans-1,3-dichloropropene may be compared to the HBSL range (0.3–30 μg/L) for the mixed isomer of 1,3-dichloropropene, CA7The concentrations from m-/p- and o-xylene can be compared to the MCL (10,000 μg/L) for mixed xylenes, CASRN 1330207. 8Additional herbicides and herbicide degradates only sampled at the Neuse, Potomac, and White Rivers during the first sampling phase. 9U.S. Environmental Protection Agency Office of Water recommends that the concentration of any combination of two or more of the three aldicarb compounds should not be 

similar mode of action. 10Concentrations of cis-permethrin may be compared to the HBSL range (4–400 μg/L) for permethrin, CASRN 52645531.
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]

Compound CASRN1

Number of 

samples

SW/FW

Detection frequency 

(percent)

Maximum concentration 

(μg/L) Human-health benchmark2

Num

(1) num

Source water Finished water Source water Finished water Sourc

Disinfection by-products

Chloroform3 67–66–3 95/94 72 100 1.5 65.6 80 Bromodichloromethane3 75–27–4 95/94 8.4 100 .16 24.0 80 Bromoform3 75–25–2 95/94 ND 32 ND 1.07 80 Dibromochloromethane3 124–48–1 95/94 ND 98 1.8 10.6 80 Trihalomethanes -- 95/94 72 100 1.8 86 80 

Fumigant-related compounds

1,4-Dichlorobenzene3 106–46–7 95/94 ND 3.2 ND 0.05 E 75 

Fungicides

Benomyl 17804–35–2 90/89 10.0 4.5 0.14 0.008 E 40 Myclobutanil 88671–89–0 90/87 5.6 5.7 .018 .018 200 Metalaxyl 57837–19–1 90/87 4.4 ND .025 ND 600 Iprodione 36734–19–7 90/87 2.2 1.1 .029 E .018 E .8 Pentachlorophenol 87–86–5 77/75 1.0 ND .12 E ND 1 Chlorothalonil 1897–45–6 84/82 ND 1.2 ND .71 5 

Gasoline hydrocarbons, oxygenates, and oxygenate degradates

Methyl tert-butyl ether 

(MTBE)4 1634–04–4

95/94 36 32 0.85 0.56 -- 

Benzene 71–43–2 83/81 14 25 .095 E .028 E 5 m- and p-Xylene5 106–42–3; 

108–38–3

95/94 13 33 .27 8.7 10,000 

Toluene 108–88–3 81/80 12 9.9 .49 .25 1,000 1,2,4-Trimethylbenzene 95–63–6 95/94 9.5 3.2 .13 .055 E -- Ethylbenzene 100–41–4 95/94 6.3 16 .069 E 2.1 700 o-Xylene5 95–47–6 95/94 5.3 15 .11 7.4 10,000 tert-Amyl methyl ether 

(TAME)

994–05–8 95/94 4.2 1.1 .045 E .034 E -- 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued [Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none] Compound CASRN1 Number of samples SW/FW Detection frequency (percent) Maximum concentration (μg/L) Human-health benchmark2 Num

(1) num

Source water Finished water Source water Finished water Sourc

Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued 1,3,5-Trimethylbenzene 108–67–8 95/94 3.2 ND 0.041 E ND -- 

1-Ethyl-2-methylben- zene (o-Ethyl toluene) 611–14–3 95/94 3.2 ND .031 E ND -- 1-Methylnaphthalene 90–12–0 96/96 3.1 2.1 .013 E 0.017 E -- 2-Methylnaphthalene4 91–57–6 96/96 3.1 4.2 .019 E .034 E 30 Styrene 100–42–5 95/94 2.1 3.2 .027 E .023 E 100 Ethyl tert-butyl ether (ETBE) 637–92–3 95/94 1.1 1.1 .020 E .023 E -- p-Isopropyltoluene 99–87–6 95/94 1.1 ND .010 E ND -- 1,2,3,4-Tetramethylben- zene 488–23–3 95/94 ND 2.1 ND .062 E -- 1,2,3,5-Tetramethylben- zene 527–53–7 95/94 ND 7.4 ND .15 -- 1,2,3-Trimethylbenzene 526–73–8 95/94 ND 4.3 ND .06 -- Isopropylbenzene 98–82–8 95/94 ND 6.4 ND .036 E 700 n-Butylbenzene 104–51–8 95/94 ND 1.1 ND .013 E -- Naphthalene 91–20–3 95/94 ND 2.1 ND .36 E 100 

Herbicides and herbicide degradates Atrazine 1912–24–9 90/87 82 87 5.0 3.4 3 

Simazine 122–34–9 90/87 82 89 .74 .73 4 Metolachlor oxanilic acid6 -- 49/48 77 59 .63 .46 -- Metolachlor ethane sulfonic acid6 -- 49/48 68 59 2.0 1.9 -- Alachlor ethane sulfonic 

acid6 --

49/48 61 59 .27 .37 -- 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]

Compound CASRN1

Number of 

samples

SW/FW

Detection frequency 

(percent)

Maximum concentration 

(μg/L) Human-health benchmark2

Num

(1) num

Source water Finished water Source water Finished water Sourc

Herbicides and herbicide degradates—Continued

Metolachlor 51218–45–2 90/87 59 54 0.80 0.47 700 Deethylatrazine (DEA) 6190–65–4 90/87 58 68 .13 .13 -- Deisopropylatrazine 

(DIA)

1007–28–9 90/89 58 63 .090 .12 -- 

Prometon 1610–18–0 90/87 56 25 .19 .20 400 2-Hydroxyatrazine 2163–68–0 89/88 52 51 .38 E .30 E 70 Alachlor oxanilic acid6 -- 49/48 50 50 .26 .12 -- 3,4-Dichloroaniline 95–76–1 85/83 47 2.4 .083 .009 -- 2,4–D 94–75–7 90/89 44 52 .76 .46 70 Diuron 330–54–1 90/89 42 24 .22 .18 2 Acetochlor oxanilic 

acid6

-- 49/48 32 25 .65 .40 -- 

Acetochlor/metolachlor 

ethane sulfonic acid 2nd amide6

-- 49/48 27 27 .10 .08 -- 

Acetochlor ethane sulfonic acid6 -- 49/48 25 27 .40 .31 -- Bentazon 25057–89–0 90/87 18 16 .020 E .020 E 200 Acetochlor 34256–82–1 90/87 16 11 .24 .14 1 Terbuthylazine 5915–41–3 90/87 16 13 .028 .027 2 MCPA 94–74–6 90/87 15 15 .44 .39 30 Alachlor 15972–60–8 90/87 13 10 .022 .017 2 Deethyldeisopropyl 

atrazine

3397–62–4 90/89 7.7 7.8 .11 E .071 E -- 

Triclopyr 55335–06–3 90/89 11 9.0 .45 .35 400 Acetochlor sulfynilacetic acid6 -- 49/48 9.1 11 .28 .17 -- 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued [Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none] Compound CASRN1 Number of samples SW/FW Detection frequency (percent) Maximum concentration (μg/L) Human-health benchmark2 Num

(1) num

Source water Finished water Source water Finished water Sourc

Herbicides and herbicide degradates—Continued Alachlor ethane sulfonic acid 2nd amide6 -- 49/48 9.1 4.5 0.06 0.070 -- 

Pendimethalin 40487–42–1 90/87 7.8 4.6 .056 .025 70 Dimethenamid6 87674–68–8 49/48 6.8 2.3 .89 .120 -- Dimethenamid ethane sulfonic acid6 -- 49/48 6.8 ND .03 ND -- 4-Chloro-2-methylphe- nol 1570–64–5 90/87 6.7 ND .008 E ND -- Imazaquin 81335–37–7 90/89 6.7 5.6 .028 E .025 E 2,000 Tebuthiuron 34014–18–1 90/87 6.7 5.7 .031 .023 E 1,000 Trifluralin 1582–09–8 90/87 6.7 2.3 .009 .006 E 20 Dacthal 1861–32–1 90/87 5.6 6.9 .005 .005 70 Siduron 1982–49–6 5.6 ND .011 E ND -- Alachlor sulfynilacetic acid 140939– 16–8 49/48 4.5 2.3 .06 .050 -- 2,4–D methyl ester 1928–38–7 90/87 4.4 2.3 .078 .063 -- Imazethapyr 81335–77–5 90/89 4.4 1.1 .20 .026 E 2,000 Metsulfuron methyl4 74223–64–6 90/89 4.4 2.2 .077 E .058 E 2,000 Chlorimuron-ethyl 90982–32–4 90/89 3.3 1.1 .015 E .006 E 600 Flumetsulam 98967–40–9 90/88 3.3 1.1 .028 E .049 7,000 Hexazinone 51235–04–2 90/87 3.3 4.6 .022 .021 400 Metribuzin 21087–64–9 90/87 3.3 1.1 .056 .016 90 Sulfometuron-methyl 74222–97–2 90/89 3.3 ND .009 E ND -- Flufenacet ethane sulfo- nic acid6 -- 49/48 2.3 2.3 .10 .090 -- 2,6-Diethylaniline 579–66–8 90/87 1.1 1.1 .002 E .003 E -- 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]

Compound CASRN1

Number of 

samples

SW/FW

Detection frequency 

(percent)

Maximum concentration 

(μg/L) Human-health benchmark2

Num

(1) num

Source water Finished water Source water Finished water Sourc

Herbicides and herbicide degradates—Continued

Bensulfuron-methyl 83055–99–6 90/89 1.1 ND 0.008 E ND 1,000 Bromacil 314–40–9 90/87 1.1 ND .017 E ND 70 Prometryn 101–42–8 90/87 1.1 ND .005 E ND 300 Propyzamide 7287–19–6 90/87 1.1 3.4 .006 E 0.007 E 1 Dicamba 23950–58–5 90/87 ND 1.1 ND .071 E 3,000 Dinoseb 1918–00–9 90/89 ND 1.1 ND .006 E 7 Diphenamid 88–85–7 90/89 ND 1.1 ND .026 200 Fluometuron 957–51–7 90/89 ND 3.4 ND .007 E 4 

Insecticides and insecticide degradates

Desulfinylfipronil -- 90/87 42 24 0.010 E 0.008 E -- Fipronil 120068–

37–3

90/87 39 1.1 .038 .009 E -- 

Carbaryl 63–25–2 90/87 20 8.0 .25 .035 40 Fipronil sulfide 120067–

83–6

90/87 20 12 .010 E .008 E -- 

Diazinon 333–41–5 90/87 17 1.1 .014 .006 1 Fipronil sulfone 120068–

36–2

90/87 13 1.1 .012 E .007 E -- 

Desulfinylfipronil amide -- 90/87 8.9 6.9 .013 E .006 E -- 1-Naphthol 90–15–3 90/87 6.7 1.1 .015 E .013 E -- Chlorpyrifos 2921–88–2 90/87 5.6 ND .006 ND 2 Propoxur 114–26–1 90/87 5.6 ND .005 E ND -- 3-Ketocarbofuran 16709–30–1 90/87 1.1 1.1 .026 E .02 E -- Imidacloprid 138261–

41–3

90/87 4.4 1.1 .042 .021 400 

Malathion 121–75–5 90/87 2.2 1.1 .018 E .009 E 50 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued [Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none] Compound CASRN1 Number of samples SW/FW Detection frequency (percent) Maximum concentration (μg/L) Human-health benchmark2 Num

(1) num

Source water Finished water Source water Finished water Sourc

Insecticides and insecticide degradates—Continued Dieldrin 60–57–1 90/87 1.1 ND 0.004 ND 0.002 

Bendiocarb 22781–23–3 90/87 ND 1.1 ND 0.019 E 9 Diazinon, oxygen analog 962–58–3 90/87 ND 1.1 ND .011 -- Dichlorvos 62–73–7 90/87 ND 1.1 ND .005 E .4 Malaoxon 1634–78–2 90/87 ND 1.1 ND .010 E -- 

Manufacturing additives Tri(2-chloroethyl)phos- phate4 115–96–8 96/96 33 31 0.26 E 0.22 E -- 

Tris(dichlorisopropyl) phosphate 13674–87–8 96/96 29 28 .17 E 5.5 -- Tributyl phosphate 126–73–8 71/72 21 2.8 .12 E .29 E -- Tri(2-butoxyethyl) phosphate 78–51–3 96/96 16 11 .4 E .56 -- Triphenyl phosphate 115–86–6 96/96 15 8.3 .1 E .16 E -- Bisphenol A 80–05–7 87/87 4.7 9.2 .67 E .44 E 400 5-Methyl-1H-benzotri- azole 136–85–6 96/96 2.1 ND .079 E ND -- 

Organic synthesis compounds Anthraquinone 84–65–1 96/96 7.3 5.2 0.14 E 0.10 E -- 

Carbazole4 86–74–8 96/96 4.2 4.2 .021 E .009 E -- Chloromethane 74–87–3 95/94 2.1 11 .029 E .055 E 30 

Pavement- and combustion-derived compounds Fluoranthene4 206–44–0 96/96 9.4 6.3 0.031 E 0.026 E 300 

Pyrene4 129–00–0 96/96 7.3 4.2 .017 E .028 E 200 Phenanthrene 85–01–8 96/96 1.0 3.1 .006 E .063 E -- Anthracene 120–12–7 96/96 1.0 ND .004 E ND 2,000 Benzo[a]pyrene 50–32–8 96/96 ND 1.0 ND .26 E .2 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]

Compound CASRN1

Number of 

samples

SW/FW

Detection frequency 

(percent)

Maximum concentration 

(μg/L) Human-health benchmark2

Num

(1) num

Source water Finished water Source water Finished water Sourc

Personal-care and domestic use products

HHCB4 1222–05–5 96/96 64 54 0.21 E 0.30 E -- Caffeine 58–08–2 77/74 61 58 .58 .22 -- AHTN4 21145–77–7 96/96 27 18 .1 E .30 E -- Camphor4 76–22–2 96/96 25 9.4 .021 E .021 E -- Triethyl citrate (ethyl 

citrate)

77–93–0 96/96 16 17 .072 E .036 E -- 

Nonylphenol diethoxylate (total) 26027–38–2 96/96 9.4 11 4.3 E 5.9 E -- Triclosan 3380–34–5 96/96 5.2 3.1 .098 E .050 E -- Cotinine 486–56–6 96/96 4.2 4.2 .28 E .077 E -- Menthol 89–78–1 96/96 4.2 5.2 .049 E .080 E -- Octylphenol monoethoxylate (total) -- 96/96 4.2 2.1 .75 E .70 E -- Indole 120–72–9 96/96 3.1 1.0 .011 E .003 E -- Octylphenol diethoxylate (total) (OP2EO)4 26636–32–8 96/96 2.1 4.2 .1 E .24 E -- d-Limonene4 5989–27–5 96/96 1.0 2.1 .044 E .075 E -- 4-n-Octylphenol 1806–26–4 96/96 ND 1.0 ND .25 E -- 4-tert-Octylphenol4 140–66–9 96/96 ND 2.1 ND .016 E -- Acetophenone 98–86–2 96/96 ND ND ND ND 700 

Plant- or animal-derived biochemicals

Cholesterol 57–88–5 96/96 24 10 1.6 E 1.3 E -- 3-beta-Coprostanol4 360–68–9 96/96 13 6.3 1.4 E .99 E -- beta-Stigmastanol 19466–47–8 96/96 9.4 5.2 1.6 E 1.6 E -- 3-Methyl-1(H)-indole 

(Skatole) 83–34–1

96/96 4.2 ND .009 E ND -- 

beta-Sitosterol 83–46–5 96/96 2.1 4.2 1.4 E 1.0 E -- 
Appendix 2. Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samsecond phase of sampling, June 2004–August 2005.—Continued [Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks in bold are Maximum CoChemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-macid; μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none] Compound CASRN1 Number of samples SW/FW Detection frequency (percent) Maximum concentration (μg/L) Human-health benchmark2 Num

(1) num

Source water Finished water Source water Finished water Sourc

Refrigerants and propellants Trichlorofluoromethane (CFC–11) 75–69–4 95/94 1.1 ND 0.020 E ND 2,000 

Solvents cis-1,2-Dichloroethene 156–59–2 95/94 15 14 0.59 0.32 70 

Perchloroethene ( PCE) 127–18–4 95/94 15 13 .11 .053 E 5 p-Cresol 106–44–5 96/96 15 6.3 .075 E .10 E -- Trichloroethene (TCE) 79–01–6 95/94 8.4 6.4 .061 E .031 E 5 Methylene chloride (dichloromethane)4 75–09–2 95/94 2.1 17 .33 .38 5 n-Propylbenzene 103–65–1 95/94 2.1 ND .021 E ND -- Acetone 67–64–1 95/94 1.1 14 3.7 E 11.2 6,000 1,2-Dichloroethane 107–06–2 95/94 ND 6.4 ND .31 5 Carbon tetrachloride (tetrachloromethane) 56–23–5 95/94 ND 32 ND .36 5 Hexachloroethane 67–72–1 95/94 ND 1.1 ND .027 E .7 Methyl ethyl ketone (MEK) 78–93–3 95/94 ND 8.5 ND 4.1 4,000 Tetrahydrofuran 109–99–9 95/94 ND 1.1 ND .70 E -- 

1This report contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. The CAS recommends the verification of the CASRNs th2HBSL values shown for carcinogens represent the low end (10-6) of the HBSL range (10-6 to 10-4 cancer risk level) (Toccalino, Norman, and others, 2006). 3The U.S. Environmental Protection Agency MCL of 80 μg/L is for the sum of the concentrations of four trihalomethanes. 4Compound detected in less than 5 percent of field blanks. 5The concentrations from m-/p- and o-xylene are be compared to the MCL (10,000 μg/L) for mixed xylenes, CASRN 1330207. 6Additional herbicides and herbicide degradates only sampled at the Elm Fork Trinity, Neuse, Potomac, and White Rivers during the second sampling phase.

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Kingsbury and others—Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams—SIR 2008–5208