# 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

This and other USGS information products are available at http://store.usgs.gov/ U.S. Geological Survey Box 25286, Denver Federal Center Denver, CO 80225

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Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted materials contained within this report.

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 / ). Informa

tion 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/nawq a ). 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 chemis

try, 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.htm l ).

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, bioac

cumulation 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 manage

ment, 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

....................................... 1 1

Annual Mean Concentration Calculations

..................................................................................... 1 2 Anthropogenic Organic Compounds in Source Water Sampled During 2002–04

............................ 1 2 Commonly Detected Compounds

..................................................................................................... 1 2 Comparison to Human-Health Benchmarks

................................................................................... 1 9 Mixtures of Compounds

..................................................................................................................... 2 2 Factors that May Affect Source-Water Quality

............................................................................. 2 2

Land Use

...................................................................................................................................... 2 3
Wastewater Discharge

............................................................................................................. 2 5

Streamflow

.................................................................................................................................. 2 5 Seasonal Variability

................................................................................................................... 2 7 Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005

............................................................................................................. 2 9 Commonly Detected Compounds

..................................................................................................... 3 0 Compounds Detected More Commonly in Source Water than in Finished Water

......... 3 0 Compounds Detected More Commonly in Finished Water than in Source Water

......... 3 2 Changes in Concentration

................................................................................................................. 3 2 Comparison to Human-Health Benchmarks

................................................................................... 3 4 Mixtures of Compounds

..................................................................................................................... 3 7 Summary and Conclusions

......................................................................................................................... 3 8

References

.................................................................................................................................................... 4 0
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 detectedusing 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 mostfrequently 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

................................... 1 0

6. Detection frequency by site for commonly detected compounds in sourcewater samples collected during the first phase of sampling,
October 2002–March 2004

......................................................................................................... 1 4

7. Length of time between collection of source- and finished-water samples during the second phase of sampling, June 2004–August 2005

......................................... 3 0

# vii



# Conversion Factors and Datums

**Multiply By**  **To obtain**

Length

mile (mi) 1.609 kilometer (km)

Area

square mile (mi 2 

# ) 2.590 square kilometer (km 2 

# )

Flow rate

cubic foot per second (ft 3 

# /s) 0.02832 cubic meter per second (m 3 

# /s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m 3 

# /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 aver

age 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 Con

taminant 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 stan

dard, 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 enforce

able (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 ofpotential concern for human health, if exceeded. HBSLs are nonenforceable benchmarks that were developed by the USGS in col

laboration 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 Drink

ing 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 hexahydrohexamethylcy

clopentabenzopyran (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 concentra

tions 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 concentra

tions 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 bench

marks used for comparison were U.S. Environmental Protec

tion 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 systemati

cally 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 associ

ated 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-dichlo

roaniline (diuron degradate), the organophosphate insecti

cides (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 estab

lished human-health benchmarks. The annual mean concen

tration 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 2or 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 contami

nants. 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 high

light 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 Hamil

ton, 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 distri

bution). 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 guide

lines 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 occur

rence 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 charac

terization 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 affect

ing 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 moni

tored. 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 ofanthropogenic organic compounds detected. The screeninglevel assessment is not a substitute for comprehensive risk assessment, which includes many more factors, such as addi

tional 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, Eliza

beth 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 reser

voirs with extensive residence times (on the order of severalyears) 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, includ

ing 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 (mi 2 

# ), with most (seven) between about 480 and 2,500 mi 2 

# (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 Cache la Poudre River**  **Truckee River White River** 

**Chattahoochee**

**River Clackamas River** 

**Elm Fork Trinity River Cache la Poudre River**  **Truckee River**

**Chattahoochee**

**River**

0 200 600 400 800 MILES

0 200 600 400 800 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 water

shed, 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 catego

ries associated with each watershed (table 1) were character

ized 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 classi

fied 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 classi

fied 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 hypochlo

rite 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 dischargers 2** **(Mgal/d) Land use** **3 (in percent)** **Agriculture Urban** **Forest Other land** **uses Classification** **(Gilliom and others, 2006)** Cache la Poudre River, Colorado132,00027.5484NA<1<17722Undeveloped.Truckee River, Nevada300,000491,050NA<145640Undeveloped.Clackamas River, Oregon100,0009.5937NA73828Undeveloped.Running Gutter Brook, Massachusetts3,3000.241NA102826Undeveloped.Chattahoochee River, Georgia750,000651,455521212715Mixed.Neuse River, North Carolina11,9002.71,2071031614637Mixed.Potomac River, Maryland1,000,00018311,464150344602Mixed.Elm Fork Trinity River, Texas2,000,0001542,459575441329Agricultural.White River, Indiana865,00015.51,1686186842Agricultural.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 major wastewater-treatmentplants in watershed upstream from intake.3Land-use data are based on 1992 National Land Cover Data (Vogelmann and others, 2001). 

# Study Design and Methods **5**

# 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) filtra

tion 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) floccula

tion 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 mix

ing, (5) flocculation, (6) sedimentation, (7) filtration using anthracite and sand, (8) disinfec

tion (chlorine), (9) addition of soda ash, and (10) distribution.

White River, Indiana (1) bar screening, (2) pretreatment, permanganate and occasionally PAC added, (3) intermit

tent blending with ground water, (4) coagulation (alum), (5) flocculation and sedimentation, (6) disinfection (chlorine), (7) filtration, (8) disinfection/chemical addition (chlorine, ammo

nia, 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 Clacka

mas 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, analyti

cal 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, includ

ing disinfection by-products; fumigant-related compounds; gasoline hydrocarbons, oxygenates, and oxygenate degra

dates; organic synthesis compounds; refrigerants and propel

lants; 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 previouslyby 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 asplasticizers 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 practi

cal 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 analyti

cal 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 com

pounds Chemicals 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 oxygen

ate degradates Gasoline hydrocarbons are straight, branched, and (or) cyclic organic compounds that are highly volatile, contain only carbon and hydrogen atoms, and are com

mon ingredients in gasoline and other petroleum products. Among these com

pounds, 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 oxygen

ates or following their release into the environment. 27

Herbicides and herbicide

degradates 1 

# Pesticides designed to kill unwanted plants (herbicides) and compounds produced from the transformation of the parent herbicide following application (degra

dates). 82

Insecticides and insecticide

degradates Pesticides designed to kill unwanted insects (insecticides) and compounds produced from the transformation of the parent insecticide following application (degra

dates). 51

Manufacturing additives Compounds used in commercial formulations of chemical products in order to im

prove the effectiveness of the product, including plasticizers (to increase the flex

ibility 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 com

pounds. 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, disin

fectants, 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 blow

ing 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 werefiltered 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 concen

trate 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 sensi

tivity 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 esti

mated. 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 collec

tion 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 labora

tory in the same manner as environmental samples and are used to characterize the likelihood for positive bias or contam

ination 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; μ g/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 contami

nation 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. Benzo

phenone, 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 (Appen

dix 1). Most of these compounds were detected at concentra

tions 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 inter

pretation 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 quench

ing agent and buffer on compound recoveries. Results indi

cated 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 accept

able 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 quench

ing 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 compoundsanalyzed 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 enforce

able, 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. Environ

mental 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 (deter

mined 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 bench

marks 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 bench

marks 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 contami

nants 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). Compari

sons 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 Protec

tion Agency, 2006c) and 110 have an HBSL (Toccalino, 2007). HBSLs have not been developed for the remaining 129 unreg

ulated 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 contam

inant 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 drink

ing 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 previ

ous 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, deethy

latrazine, metolachlor, and hexahydrohexamethylcyclopent

abenzopyran (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 choles

terol, 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 degra

dates being detected most commonly. The smaller detec

tion 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 herbi

cide 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 controlin 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, October 2002–March2004.—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 primary-use group are arranged indescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some compounds; AHTN, acetyl hexamethyl 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, Massa chusetts** **(N=16) Chatta** **hoochee River,** **Georgia (N=17)** **Neuse River, North** **Carolina (N=17)** **Potomac River, Maryland** **(N=12) Elm Fork** **Trinity River, Texas** **(N=17) White River,** **Indiana (N=17)** Disinfection by-productsChloroform69ND63910094100100100100Bromodichloromethane20NDND627186177141FungicidesBenomyl12NDNDNDND532581218Gasoline hydrocarbons, oxygenates, and oxygenate degradatesMethyltert-butyl ether(MTBE)36NDNDND474176671006Benzene3124126727--47172424Toluene18ND1256ND291817--6m- andp-Xylene13ND656ND126176121,2,4-Trimethylbenzene12ND656ND126866tert-Butyl alcohol11NDNDNDND1335ND47NDo-Xylene11ND656ND66866Herbicides and herbicide degradatesSimazine67NDND5363100100100100100Atrazine64ND6297510076100100100Deethylatrazine52ND1818314771100100100Metolachlor51NDND181341100100100100Deisopropylatrazine49NDNDND825338810088Prometon49NDND6ND9410092651002,4–D43NDND6ND87695882942-Hydroxyatrazine40NDNDNDND4750921001003,4-Dichloroaniline40NDNDNDND9488179463Diuron30ND647ND40382510018MCPA21NDNDNDND6725335324Alachlor15NDNDNDNDNDNDND6569 

# 14 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Table 6.** Detection frequency by site for commonly detected compounds in source-water samples collected during the first phase of sampling, October 2002–March2004.—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 primary-use group are arranged indescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some compounds; AHTN, acetyl hexamethyl 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, Massa chusetts** **(N=16) Chatta** **hoochee River,** **Georgia (N=17)** **Neuse River, North** **Carolina (N=17)** **Potomac River, Maryland** **(N=12) Elm Fork** **Trinity River, Texas** **(N=17) White River,** **Indiana (N=17)** Herbicides and herbicide degradates—ContinuedAcetochlor12NDNDNDNDNDND17ND100Bentazon12NDNDNDNDND6ND688Terbuthylazine12NDNDNDND647NDND50Triclopyr12NDNDNDND406171241Tebuthiuron11NDNDNDND1812ND4718Insecticides and insecticide degradatesDiazinon39NDND12ND5982339465Fipronil29NDNDNDND5988174156Carbaryl15NDND18ND473133296Manufacturing additivesTri(2-chloroethyl)phosphate34ND6ND75671338847Tris(dichlorisopropyl)-phosphate26NDNDNDND4453257135Tributyl phosphate20NDND6--3135--5318Tri(2-butoxyethyl)phosphate19NDNDNDND3829175329Triphenyl phosphate166ND6ND3824173518Personal-care and domestic-use productsHHCB53624ND2781886710094AHTN39NDNDND207582257176Caffeine316186125041--29654-Nonylphenol diethoxylate (total)146NDND13252981824Triethyl citrate (ethylcitrate)14NDNDNDND1924829414-Octylphenol monoethoxylate (total)116NDND132518171212 

# Anthropogenic Organic Compounds in Source Water Sampled During 2002–04 **15 Table 6.** Detection frequency by site for commonly detected compounds in source-water samples collected during the first phase of sampling, October 2002–March2004.—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 primary-use group are arranged indescending detection frequency. No assessment level was used to determine detection frequency. N, typical number of samples—the number of analyses may vary for some compounds; AHTN, acetyl hexamethyl 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, Massa chusetts** **(N=16) Chatta** **hoochee River,** **Georgia (N=17)** **Neuse River, North** **Carolina (N=17)** **Potomac River, Maryland** **(N=12) Elm Fork** **Trinity River, Texas** **(N=17) White River,** **Indiana (N=17)** Plant- or animal-derived biochemicalsCholesterol17NDND6ND3147251824beta-Stigmastanol11NDNDNDND2535812183-beta-Coprostanol10NDNDNDND1329251218Solventsp-Cresol2012411813312481812Perchloroethene (PCE)17NDNDNDNDND41ND1888cis-1,2-Dichloroethene12NDNDNDNDNDNDNDND100 

# 16 **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 **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, includ

ing 83 agricultural, 8 undeveloped, and 65 mixed-land use watersheds (fig. 3) (Gilliom and others, 2006). Detectionfrequencies 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. 3 A ).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 ofdeethylatrazine) were detected more commonly in sourcewater samples collected in the mixed and agricultural landuse watersheds in this study than in ambient stream samples (figs. 3 B and 3 C ), 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. 3 B and 3 C ). 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 concentra

tions 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 indus

trial 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 condi

tioners 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 Metolachlor Alachlor Atrazine Metolachlor degradates Alachlor degradates 0

. 0 1 0

. 1

1 1 0CONCENTRATION, 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-chlo

roethyl)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 munici

pal, industrial, or agricultural wastewater discharge (Kolpin and others, 2002). These biochemicals may be contributed to streams with wastewater discharge, but they also occur natu

rally 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 contami

nated, 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 occur

rence 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 concentra

tions could be compared. Annual mean concentrations of all compounds at each site were less than human-health bench

marks. Most of the compounds detected were present at concentrations less than 0.1 μg/L (Appendix 1), and only threecompounds (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 Contami

nant Levels (MCLs). 0.00001 0

. 0 0 0 1 0

. 0 0 1 0

. 0 1 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** c i

s

- 1

, 2 -Dichloroethene

Per c h l o r o e t h e n e A l a c h l o r

2

, 4

– 

# D A t r a z i n e S i m a z i n e

o

- X y l e n e m

- & p

- X y l e n e B e n z e n e T o l u e n e B r o m o d i c h l o r o m e t h a n e C h l o r o f o r m

c i

s

- 1

, 2 -Dichloroethene

Per c h l o r o e t h e n e A l a c h l o r

2

, 4

– 

# D A t r a z i n e S i m a z i n e

o

- X y l e n e m

- & p

- X y l e n e B e n z e n e T o l u e n e B r o m o d i c h l o r o m e t h a n e C h l o r o f o r m Disinfection by-products

Herbicides

Gasoline hydrocarbons

Solvents

Disinfection by-products

Herbicides

Gasoline hydrocarbons

Solvents



# Neuse River **Running Gutter Brook**
**Truckee River Potomac River**  **Cache la Poudre 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 2-methyl-4-chlorophenoxyacetic acid MCPA C a r b a r y l

D i a z i n o n T e b u t h i u r o n

T e r b u t h y l a z i n e A c e t o c h l o r

T r i c l o p y r

M C P A D i u r o n 2

- H y d r o x y a t r a z i n e

P r o m e t o n M e t o l a c h l o r

B e n o m y l Bentazon 

# BQ BQ 

# B

0.00001 0

. 0 0 0 1 0

. 0 0 1 0

. 0 1 0

. 1 1 10 0

. 0 0 1 0

. 0 1 0

. 1 1 1 0 

# C a r b a r y l

D i a z i n o n T e b u t h i u r o n

T e r b u t h y l a z i n e A c e t o c h l o r

T r i c l o p y r

M C P A D i u r o n 2

- H y d r o x y a t r a z i n e

P r o m e t o n M e t o l a c h l o r

B e n o m y l 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 concentra

tions 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 stream

flow 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 concentra

tion. Very few samples had individual BQ values greater than0.1 (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 prod

ucts.



# 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 water

shed 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 compo

nents. 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 syner

gistic, but much of the growing concern about exposure to mixtures of compounds is related to the potential for synergis

tic 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 gener

ally 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 increas

ingly 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 concentra

tions 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 percentof 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 herbi

cides 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 occur

rence 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 1 0 2 0 3 0 4 0 5 0



# N UMBER OF COMPOUNDS IN A SAMPLE 0 2 0 4 0 6 0 8 0 1 0 0PERCENTAGE OF SAMPLES WITH EQUAL ORGREATER NUMBER OF COMPOUNDS



# 0 2 0 30 50 10 4 0 100 6 0 70 80 90

SUM OF AGRICULTURAL AND URBAN LAND USE, IN PERCENT 0 10 20 30MEDIAN 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 White River Elm Fork Trinity 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 associa

tions related to land use, wastewater discharge, streamflow, and seasonality. These factors have been found to be asso

ciated 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 rela

tively 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 herbi

cides 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 degra

dates 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 concen

trations 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 concen

trations 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, essen

tially has no agricultural land use in its watershed. In contrast, no clear relation between agricultural land use and the occur

rence 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 agri cultural 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 100CONCENTRATION, 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, includingdisinfection 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, Clacka

mas, 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 irriga

tion), 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 thatorganic 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 occur

rence 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 atra

zine. For example, at the Elm Fork Trinity River site, which is downstream from a reservoir, the range in atrazine concentra

tions was considerably less than at other sites where atrazine was detected commonly. Just as a reservoir upstream moder

ates 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 concentra

tion 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 contrib

uted 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 concen

trations 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 concentra

tions 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

1CONCENTRATION, 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

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0 0

. 0 0 1 0

. 0 1 0

. 1

LRL 0

. 0 0 1 0

. 0 1 0

. 1

1 1 0

0

. 0 1 0

. 1

1



# Chattahoochee River

**Neuse River Running Gutter Brook** 

**Truckee River P**  **otomac River Cache la Poudre 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, atra

zine, 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 associ

ated with high streamflow, likely the result of runoff follow

ing 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. Chattahoochee River Potomac River

White River

0

. 0 0 1 0

. 0 1 0

. 1

1 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0 0

. 0 0 1 0

. 0 1 0

. 1

1 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0 0

. 0 0 1 0

. 0 1 0

. 1

1 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0

0

. 0 0 1 0

. 0 1 0

. 1

1 

# 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0

0

. 0 0 1 0

. 0 1 0

. 1

1 

# 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0

0

. 0 0 1 0

. 0 1 0

. 1

1 

# 1 0

1 0 1 0 0 1

, 0 0 0 1 0

, 0 0 0 1 0 0

, 0 0 0 

# Neuse River

Running Gutter Brook Elm Fork Trinity River

**EXPLANATION**

Total herbicide concentration

Total herbicide concentration with additional chloroacetanilide degradatesSTREAMFLOW, 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


# 2004 2002 2003 O N D J F M A M J J A S O N D J FTOTAL 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

. 0 0 1 0

. 0 1 0

. 1

1 1 0

0

. 0 0 1 0

. 0 1 0

. 1

1 1 0 Atrazine
Simazine



# White River Chattahoochee RiverCONCENTRATION, IN MICROGRAMS PER LITER



# Atrazine
Simazine

O


# 2004

2002 2003

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 concentra

tion 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). Concentra

tion profiles of atrazine and simazine also were similar at the White River; however, a small increase in simazine concen

trations 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 herbi

cides 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 gener

ally 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 collec

tion 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 treat

ment 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-watersamples 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 meetdemand during peak use. Some differences between sourceand finished-water quality might be attributable to changes insource-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 finished water 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, consist

ing of coagulation, flocculation, sedimentation, filtration, and disinfection. The other three CWSs used other types of treat

ment (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 representa

tive 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 excep

tion 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 detec

tion frequency in finished water. Detection frequencies of all compounds detected in source or finished water are summa

rized 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, volatiliza

tion, 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). Diaz

oxon (diazinon oxygen analog), which is the principal degra

date 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 2 0 4 0 6 0 8 0 1 0 0 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 2-methyl-4-chlorophenoxyacetic acid MCPA 

# Figure 14. Many commonly detected anthropogenic organiccompounds 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 organophos

phate 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 corre

sponding source-water detection. These results are similar toresults 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 organophos

phate 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 -cresolmay 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 frequen

cies 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 plumb

ing, 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 concen

trations 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-treatmentplants. 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 contami

nant 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 perspec

tive 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 impor

tant 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. 15 A ). 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 gener

ally were similar to those for atrazine in that finished-waterconcentrations 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. 15 B ), 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, mala

thion, 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. 15 C ); 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, partic

ularly 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 concen

trations 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 concen

tration 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 differ

ences 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 repre

sent 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 10CONCENTRATION 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, concen

trations 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 concen

trations 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 drink

ing 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 bench

marks. More than one-half of the most commonly detected compounds have a human-health benchmark for compari

son. Annual mean concentrations for most of the commonly detected compounds were two to five orders of magnitude less than their human-health benchmarks (fig. 17 A ). Two disin

fection by-products had annual mean concentrations within a factor of 10 (BQ greater than 0.1) of the MCL for total trihalomethanes (fig. 17 A ). Chloroform was present in finished water at all CWSs with annual mean BQ values between

0.1 and 0.3. Annual mean concentrations for bromodichlo

romethane were within a factor of 10 of the MCL at three

CWSs. Concentrations of bromoform and dibromochlo

romethane 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 Elm Fork Trinity River Chattahoochee 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 10CONCENTRATION, 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

Disinfection by-product DBP

2-methyl-4-chlorophenoxyacetic acid MCPA



# Figure 17. During the second phase of sampling, June 2004–August 2005, A , annual mean concentrationsof 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 Source**Water Quality Assessments**


# S ince 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 custom

ers ( http://www.epa.gov/safewater/ccr/ccrfact.htm l ). CCRs are the centerpiece of the right-to-know provi

sions of the 1996 Amendments to the Safe Drinking Water Act. Each CCR provides consumers with funda

mental information about their drinking water including (1) the source of the drinking water, (2) a brief sum

mary 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 Con

taminant 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 informa

tion. 

# 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 report

ing 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 concentra

tions 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. 17 A ), and the annual mean concentrations of atrazine were 0.46 and 0.72 μg/L, respec

tively. 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. 17 B ). Of the commonly detected compounds, disinfection by-products and herbicides were the only primary use groups with BQmax values greater than 0.1. One detec

tion 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 concentra

tions 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 infre

quently 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 concentra

tion 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 percent

age 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, containedmore 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 treat

ment (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 identi

fying 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 waterPERCENTAGE OF SAMPLES WITH EQUAL OR GREATERNUMBER OF COMPOUNDS 

# USEPA Drinking Water Levels of **Comparison for Atrazine and its Degradates in Community Water Systems** 


# A s 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 deethylde

isopropyl 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. 

# T he 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 dur

ing 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. 

# C urrently (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). 

# A lthough 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 remain

der 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 sam

pling. **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 treat

ment and before distribution) were collected monthly to char

acterize 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 water

sheds 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 coagula

tion, 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 bench

marks. 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 concentra

tion (20.5 μg/L) greater than its Maximum Contaminant Level (MCL) of 3 μg/L for drinking water. The annual mean concen

tration 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 gener

ally 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, gener

ally 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 water

sheds 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 charac

terized 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, prob

ably 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 undevel

oped 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 agri

cultural 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-waterquality in this report is not intended as an evaluation of watertreatment efficacy at these CWSs. Rather, the results from thisstudy 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 frequen

cies in finished water. Concentrations of these compounds commonly were lower in finished water than in the corre

sponding 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 asatrazine, 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 detec

tion 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 concen

tration 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 consid

erably 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 theparent 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

# 46 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Disinfection by-productsChloroform367–66–314769.40.0242.8615.6MCL80Bromodichloromethane375–27–414720.4.028.513.4MCL80Dibromochloromethane3124–48–11474.1.1.17.7MCL80Bromoform375–25–2147.7.1.098 ENDMCL80Fumigant-related compounds1,4-Dichlorobenzene4106–46–71479.50.0340.083 ENDMCL751,2-Dichloropropane78–87–51471.4.029.016 ENDMCL51,2-Dibromoethane106–93–4147ND.036NDNDMCL.051,2-Dibromo-3-chloropropane96–12–8147ND.51NDNDMCL.21,3-Dichloropropane5142–28–9147ND.06NDND----2,2-Dichloropropane5594–20–7147ND.05NDND----Bromomethane574–83–9147ND.33NDNDHBSL100cis-1,3-Dichloropropene5,610061–01–5147ND.05NDNDHBSL2.3trans-1,3-Dichloropropene5,610061–02–6147ND.09NDNDHBSL2.3FungicidesBenomyl17804–35–214512.40.0220.12 E0.7HBSL40Metalaxyl57837–19–11454.8.007.015NDHBSL600Pentachlorophenol87–86–51453.42.32 E2.1MCL1Myclobutanil88671–89–01462.7.033.021NDHBSL200Propiconazole--145.7.01.042NDHBSL70Chlorothalonil1897–45–6145ND.035NDNDHBSL5Iprodione36734–19–7145ND.026NDNDHBSL.8Gasoline hydrocarbons, oxygenates, and oxygenate degradatesMethyltert-butyl ether(MTBE)41634–04–414736.10.13.4418.4----Benzene71–43–213030.8.021.464.6MCL5

# Appendix 1 **47 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Gasoline hydrocarbons, oxygenates, and oxygenate degradates—ContinuedToluene108–88–313017.70.021.989.2MCL1,000m-andp-Xylene106–42–3;108–38–314712.9.061.406.8MCL710,0001,2,4-Trimethylbenzene595–63–614711.6.0556.523.4----tert-Butyl alcohol75–65–014511.011.0511.0----o-Xylene95–47–614710.9.038.554.8MCL710,000Ethylbenzene100–41–41478.8.03.36.7MCL7001-Ethyl-2-methylbenzene(o-Ethyl toluene)611–14–31476.8.038.12.7----1,3,5-Trimethylbenzene108–67–81475.4.044.15.7----1,2,3-Trimethylbenzene526–73–81473.4.09.11 E.7----tert-Amyl methyl ether(TAME)994–05–81472.0.04.088 END----1,2,3,5-Tetramethylbenzene527–53–71471.4.18.072 END----Styrene4100–42–51471.4.042.050 ENDMCL1001-Methylnaphthalene90–12–0145.7.5.022 END----2-Methylnaphthalene491–57–6145.7.5.035 ENDHBSL30Isopropylbenzene98–82–8147.7.038.022 ENDHBSL700n-Butylbenzene104–51–8147.7.14.016 END----1,2,3,4-Tetramethylbenzene488–23–3147ND.14NDND----2,6-Dimethylnaphthalene581–42–0145ND.5NDND----Diisopropyl ether (DIPE)108–20–3147ND.1NDND----Naphthalene591–20–3147ND.5NDND----p-Isopropyltoluene599–87–6147ND.08NDND----sec-Butylbenzene135–98–8147ND.06NDND----tert-Amyl alcohol(2-Methyl-2-butanol)75–85–4145ND1NDND----

# 48 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Gasoline hydrocarbons, oxygenates, and oxygenate degradates—ContinuedEthyltert-butyl ether (ETBE)637–92–3147ND0.03NDND----tert-Butylbenzene98–06–6147ND.08NDND----Herbicides and herbicide degradatesSimazine122–34–914667.10.0053.2328.1MCL4Atrazine1912–24–914663.7.00720.126.7MCL3Deethylatrazine5(DEA)6190–65–414752.4.014.54 E10.9----Metolachlor551218–45–214651.4.0062.938.8HBSL700Prometon1610–18–014649.3.01.054NDHBSL400Deisopropylatrazine (DIA)1007–28–914549.0.08.404.1----2,4–D94–75–714542.8.0384.7815.9MCL703,4-Dichloroaniline95–76–114640.4.0045.06ND----2-Hydroxyatrazine2163–68–014540.0.0321.65 E22.1HBSL70Diuron4330–54–114530.3.016.444.1HBSL22MCPA94–74–614521.4.07.474.8HBSL30Alachlor15972–60–814615.1.005.087NDMCL2Triclopyr55335–06–314512.4.026.211.4HBSL400Acetochlor34256–82–114612.3.0064.323.4HBSL21Bentazon25057–89–014511.7.024.10 E.7HBSL200Terbuthylazine5915–41–314611.6.0083.017NDHBSL2Tebuthiuron34014–18–114710.9.026.028NDHBSL1,000Pendimethalin40487–42–11468.9.022.038NDHBSL70Imazaquin81335–37–71458.3.036.15 E.7HBSL2,000Metribuzin521087–64–91468.2.028.078NDHBSL90Dicamba1918–00–91456.9.036.672.8HBSL3,0002,4–D methyl ester1928–38–71455.5.19.653.4----Imazethapyr81335–77–51455.5.038.13 E1.4HBSL2,000

# Appendix 1 **49 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Herbicides and herbicide degradates—ContinuedPropyzamide23950–58–51465.50.0040.010NDHBSL21Hexazinone51235–04–2808.8.026.018NDHBSL400Chlorimuron-ethyl90982–32–41454.1.032.20 E0.7HBSL6004-Chloro-2-methylphenol1570–64–51464.1.005.013 END----Flumetsulam98967–40–91453.4.04.052 ENDHBSL7,000Bromacil314–40–91452.8.018.093 ENDHBSL70Dichlorprop120–36–51452.8.036.070NDHBSL300Sulfometuron-methyl74222–97–21452.8.09.024ND----2-Ethyl-6-methylaniline24549–06–21462.1.01.002 END----Clopyralid1702–17–61452.1.067.046ND----Metsulfuron methyl474223–64–61452.1.067.09 ENDHBSL2,000Dacthal1861–32–11462.1.014.002 ENDHBSL70Trifluralin1582–09–81462.1.009.005 ENDHBSL20Siduron1982–49–61451.4.02.013 END----Acifluorfen50594–66–6145.7.028.011NDHBSL90Bromoxynil1689–84–5145.7.044.004 ENDHBSL10Deethyldeisopropyl atrazine(DDA)3397–62–4144.7.04.16 E.7----Dinoseb88–85–7145.7.038.004 ENDMCL7Diphenamid957–51–7145.7.01.010 ENDHBSL200Nicosulfuron111991–09–4145.7.04.087 ENDHBSL9,000Norflurazon27314–13–2145.7.02.004 ENDHBSL10Oryzalin19044–88–3145.7.023.065 ENDHBSL24Picloram1918–02–1145.7.032.16.7MCL500Terbacil5902–51–2145.7.026.01 ENDHBSL90Metolachlor ethane sulfonicacid8--3969.2.022.0766.7----

# 50 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Herbicides and herbicide degradates—ContinuedMetolachlor oxanilic acid8--3966.70.021.4743.6----Alachlor ethane sulfonic acid8--3959.0.02.2433.3----Acetochlor ethane sulfonicacid8--3941.0.021.4235.9----Alachlor oxanilic acid8--3941.0.02.137.7----Acetochlor oxanilic acid8--3938.5.021.7430.8----Acetochlor sulfynilacetic acid8--3925.6.021.2217.9----Dimethenamid ethane sulfonicacid8--3912.8.02.112.6----Alachlor sulfynilacetic acid8140939–16–8395.1.02.112.6----Dimethenamid oxanilic acid8--392.6.02.05ND----Propachlor81918–16–70--.02----HBSL212-Chloro-2,6-diethylaceta-nilide6967–29–9146ND.0065NDND----Benfluralin1861–40–1146ND.01NDNDHBSL4Cycloate1134–23–2145ND.014NDNDHBSL40Prometryn7287–19–6146ND.0059NDNDHBSL300Linuron5330–55–2145ND.014NDNDHBSL5MCPB94–81–5145ND.1NDNDHBSL1002,4–DB94–82–6145ND.02NDNDHBSL200Fluometuron2164–17–2145ND.016NDNDHBSL4Propham122–42–9145ND.03NDNDHBSL100Neburon555–37–3145ND.012NDND----Fenuron101–42–8145ND.1NDND----Dacthal monoacid887–54–7145ND.028NDND----Chloramben, methyl ester7286–84–2145ND.024NDND----Dimethenamid87674–68–86ND.02NDND----

# Appendix 1 **51 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Herbicides and herbicide degradates—Continued3(4-Chlorophenyl)-1-methylurea5352–88–5145ND0.036NDND----Bensulfuron-methyl83055–99–6145ND.018NDNDHBSL1,000Flufenacet ethane sulfonicacid8--39ND.02NDND----Flufenacet8142459–58–36ND.02NDND----Flufenacet oxanilic acid8--39ND.02NDND----Propachlor ethane sulfonicacid8--39ND.02NDND----Propachlor oxanilic acid8--39ND.02NDND----Alachlor ethane sulfonic acid2nd amide8--11ND.02NDND----Acetochlor/metolachlor ethanesulfonic acid 2nd amide8--6ND.02NDND----2,6-Diethylaniline579–66–8146ND.006NDND----Insecticide and insecticide degradatesDiazinon333–41–514639.00.0050.086NDHBSL1Fipronil120068–37–314629.5.016.016ND----Carbaryl63–25–214515.2.018.065 ENDHBSL240Desulfinylfipronil--1467.5.012.006ND----1-Naphthol90–15–31466.2.0882.014 END----Chlorpyrifos2921–88–21466.2.005.008NDHBSL2Fipronil sulfide120067–83–61466.2.013.007ND----Dichlorvos62–73–71464.1.006.012NDHBSL.4Imidacloprid138261–41–31452.8.023.037NDHBSL400Propoxur114–26–11452.8.008.006 ENDHBSL29Carbofuran1563–66–21452.1.016.012NDMCL40

# 52 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Insecticide and insecticide degradates—ContinuedMalathion121–75–51462.10.0270.018 ENDHBSL50Dimethoate60–51–51461.4.0061.009 ENDHBSL2Fipronil sulfone120068–36–21461.4.024.008 END----Phosmet732–11–6141.7.0079.007 ENDHBSL8Azinphos-methyl86–50–0146.7.05.016 ENDHBSL10Dieldrin60–57–1146.7.009.004 ENDHBSL2.0023-Hydroxycarbofuran16655–82–6145ND.008NDND----3-Ketocarbofuran16709–30–1145ND1.5NDND----Aldicarb116–06–3145ND.15NDNDHBSL99Aldicarb sulfoxide1646–87–3145ND.1NDNDHBSL97Aldicarb sulfone1646–88–4145ND.018NDNDHBSL97Azinphos-methyl-oxon961–22–8145ND.042NDND----Bendiocarb22781–23–3145ND.08NDNDHBSL9Chlorpyrifos, oxygen analog5598–15–2146ND.0562NDND----cis-Permethrin54774–45–7146ND.006NDNDHBSL2,104Cyfluthrin68359–37–5146ND.053NDNDHBSL200Cypermethrin52315–07–8146ND.046NDNDHBSL40Desulfinylfipronil amide--146ND.029NDND----Diazinon, oxygen analog962–58–3146ND.006NDND----Dicrotophos141–66–2144ND.0843NDNDHBSL.05Ethion563–12–2146ND.016NDNDHBSL4Ethion monoxon17356–42–2146ND.021NDND----Fenamiphos22224–92–6146ND.029NDNDHBSL.7Fenamiphos sulfone31972–44–8146ND.053NDND----Fenamiphos sulfoxide31972–43–7143ND.04NDND----Fonofos944–22–9146ND.0053NDNDHBSL10

# Appendix 1 **53 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Insecticide and insecticide degradates—ContinuedFonofos oxygen analog944–21–8146ND0.0029NDND----Isofenphos25311–71–1146ND.011NDNDHBSL6Malaoxon1634–78–2146ND.039NDND----Methidathion950–37–8146ND.0087NDNDHBSL1Methiocarb2032–65–7145ND.034NDNDHBSL40Methomyl16752–77–5145ND.07NDNDHBSL200Oxamyl23135–22–0145ND.05NDNDMCL200Paraoxon-methyl950–35–6146ND.019NDND----Parathion-methyl298–00–0146ND.015NDNDHBSL1Phorate298–02–2146ND.055NDNDHBSL4Phorate oxon2600–69–3146ND.027NDND----Phosmet oxon3735–33–9138ND.0511NDND----Terbufos13071–79–9146ND.017NDNDHBSL.4Terbufos-oxygen-analoguesulfone56070–15–6146ND.045NDND----Manufacturing additivesTri(2-chloroethyl)phosphate4115–96–814534.50.50.14 E8.3----Tris(dichlorisopropyl)phosphate13674–87–814525.5.5.12 E3.4----Tributyl phosphate126–73–811820.3.5.22 E7.6----Tri(2-butoxyethyl)phosphate78–51–314518.6.5.9318.6----Triphenyl phosphate115–86–614515.9.5.077 END----Bisphenol A80–05–7145C1CCHBSL4005-Methyl-1H-benzotriazole136–85–6145.72.36 E.7----

# 54 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Organic synthesis compoundsAnthraquinone84–65–11466.20.50.11 E2.0----Carbazole486–74–81462.1.5.051 END----Carbon disulfide475–15–01472.0.038.034 ENDHBSL700Chloromethane74–87–31471.4.17.10 E.7HBSL301,1-Dichloropropene5563–58–6147ND.026NDND----1,2,3-Trichlorobenzene87–61–6147ND.18NDND----1,2,3-Trichloropropane96–18–4147ND.18NDNDHBSL403-Chloro-1-propene107–05–1147ND.5NDND----Acrylonitrile107–13–1147ND.8NDNDHBSL.06Ethyl methacrylate(ethyl 2-methyl-2-propano-ate)97–63–2147ND.18NDND----Hexachlorobutadiene587–68–3147ND.14NDNDHBSL2.9Iodomethane74–88–4147ND.5NDND----Methyl acrylate(methyl-2-propenoate)96–33–3147ND1NDND----Methyl acrylonitrile(2-methyl-2-propenenitrile)126–98–7147ND.4NDNDHBSL.7Methyl methacrylate (methyl2-methyl-2-propenoate)80–62–6147ND.2NDNDHBSL10,000trans-1,4-Dichloro-2-butene110–57–6147ND.7NDND----Vinyl bromide593–60–2147ND.1NDND----Vinyl chloride75–01–4147ND.08NDNDMCL2Pavement- and combustion-derived compoundsFluoranthene4206–44–01456.90.50.053 ENDHBSL300Pyrene4129–00–01456.9.5.049 ENDHBSL200Anthracene120–12–7145ND.5NDNDHBSL2,000

# Appendix 1 **55 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Pavement- and combustion-derived compounds—ContinuedBenzo[a]pyrene50–32–8145ND0.5NDNDMCL.2Phenanthrene85–01–8145ND.5NDND----Personal-care and domestic-use productsHHCB41222–05–514553.10.50.26 E16.6----AHTN421145–77–714538.6.5.15 E.7----Caffeine58–08–213231.1.018.152.3----Nonylphenol diethoxylate(total) (NP2EO)26027–38–214413.856.6 E13.8----Triethyl citrate (ethyl citrate)77–93–014413.9.5.19 E.7----Octylphenol monoethoxylate(total)4(OP2EO)--14511.01.82 E11.0----Octylphenol diethoxylate(total)4(OP1EO)26636–32–81458.31.25 E6.2----Indole120–72–91456.2.5.1 E.7----Triclosan3380–34–51445.6.5.1 E.7----Methyl salicylate119–36–81454.1.5.39 E2.8HBSL4,000Menthol89–78–11452.8.5.16 E.7----Camphor476–22–21452.8.5.026 END----Cotinine486–56–61452.81.25 E1.4----d-Limonene45989–27–51451.4.5.064 END----4-tert-Octylphenol4140–66–9145ND1NDND----4-Cumylphenol599–64–4145ND1NDND----3-tert-Butyl-4-hydroxy anisole(BHA)25013–16–5145ND5NDND----4-n-Octylphenol1806–26–4145ND1NDND----Acetophenone98–86–2145ND.5NDNDHBSL700Benzophenone119–61–9145R.5--------

# 56 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Personal-care and domestic-use products—ContinuedBromochloromethane74–97–5145ND0.12NDNDHBSL90Isoborneol124–76–5145ND.5NDND----Isoquinoline119–65–3145ND.5NDND----N,N-diethyl-meta-toluamide(DEET)134–62–3145R.5--------Phenol108–95–2145R.5HBSL2,000para-Nonylphenol (total)84852–15–3145R5--------Plant- or animal-derived biochemicalsCholesterol57–88–514516.622.5 E16.6----beta-Stigmastanol19466–47–814511.022.3 E11.0----3-beta-Coprostanol4360–68–914510.321 E10.3----beta-Sitosterol83–46–51457.622.3 E7.6----3-Methyl-1(H)-indole (skatole)83–34–11453.41.064 END----Refrigerants and propellants1,1,2-Trichloro-1,2,2-trifluoroethane(CFC–113)76–13–1147ND0.038NDNDHBSL200,000Dichlorodifluoromethane(CFC–12)75–71–8147ND.18NDNDHBSL1,000Trichlorofluoromethane(CFC–11)75–69–4147ND.08NDNDHBSL2,000Solventsp-Cresol106–44–514520.010.39 E2.8----Perchloroethene (PCE)127–18–414717.0.03.162.7MCL5cis-1,2-Dichloroethene156–59–214711.6.024.544.8MCL70Trichloroethene (TCE)79–01–61476.8.038.066 ENDMCL5Methylene chloride (dichloromethane)475–09–21475.4.06.083 ENDMCL5

# Appendix 1 **57 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health benchmark** **2 Human-health** **benchmark (μg/L)** Refrigerants and propellants—Continuedn-Propylbenzene103–65–11474.80.0420.08 END----Acetone67–64–1147163.8 E1HBSL6,0001,3-Dichlorobenzene541–73–1147.7.03.053 ENDHBSL600Carbon tetrachloride (tetrachloromethane)56–23–5147.7.06.043 ENDMCL5Tetrahydrofuran109–99–9147.71.2.32 E.7----1,1,1,2-Tetrachloroethane630–20–6147ND.03NDNDHBSL701,1,1-Trichloroethane71–55–6147ND.032NDNDMCL2001,1,2,2-Tetrachloroethane579–34–5147ND.03NDNDHBSL.31,1,2-Trichloroethane79–00–5147ND.04NDNDMCL51,1-Dichloroethane75–34–3147ND.035NDND----1,1-Dichloroethene575–35–4147ND.024NDNDMCL71,2,4-Trichlorobenzene120–82–1147ND.12NDNDMCL701,2-Dichlorobenzene95–50–1147ND.048NDNDMCL6001,2-Dichloroethane107–06–2147ND.13NDNDMCL52-Chlorotoluene95–49–8147ND.04NDNDHBSL1002-Hexanone591–78–6147ND.4NDND----4-Chlorotoluene106–43–4147ND.05NDNDHBSL100Bromobenzene5108–86–1147ND.028NDND----Chlorobenzene108–90–7147ND.028NDNDMCL100Chloroethane75–00–3147ND.12NDND----Dibromomethane74–95–3147ND.05NDND----Diethyl ether(1,1’-oxybisethane)60–29–7147ND.08NDNDHBSL1,000Hexachloroethane67–72–1147ND.14NDNDHBSL.7Isophorone78–59–1145R.5----HBSL100Methyl acetate79–20–9147ND.43NDND----

# 58 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring the first phase ofsampling, 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, estimated; AHTN, acetyl hexamethyltetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCL, Maximum Contaminant Level; HBSL, Health-Based Screening Level; ND,not detected;μg/L, micrograms per liter; --, no data; R, removed from data set; C, censored]**Compound (other name or abbreviation)** **CASRN 1** **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-health** **benchmark 2** **Human-health benchmark** **(μg/L)**Refrigerants and propellants—ContinuedMethyl ethyl ketone (MEK)78–93–3147ND2NDNDHBSL4,000Methyl isobutyl ketone(4-methyl-2-pentanone;MIBK)108–10–1147ND.37NDND----trans-1,2-Dichloroethene156–60–5147ND.032NDNDMCL1001This report contains CAS Registry Numbers®, which is a Registered Trademark of the American Chemical Society. The CAS recommends the verification of the CASRNs through CAS Client ServicesSM.2HBSL values shown for carcinogens represent the low end (10-6) of the HBSL range (10-6to 10-4cancer 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 fromcis-1,3- andtrans-1,3-dichloropropene may be compared to the HBSL range (0.3–30 μg/L) for the mixed isomer of 1,3-dichloropropene, CASRN 542756.7The concentrations fromm-/p- ando-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 greater than 7 μg/L because ofsimilar mode of action.10Concentrations ofcis-permethrin may be compared to the HBSL range (4–400 μg/L) for permethrin, CASRN 52645531.

# Apprendix 2 **59 Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Disinfection by-productsChloroform367–66–395/94721001.565.680--78Bromodichloromethane375–27–495/948.4100.1624.080--35Bromoform375–25–295/94ND32ND1.0780----Dibromochloromethane3124–48–195/94ND981.810.680--2Trihalomethanes--95/94721001.88680--90 (1)Fumigant-related compounds1,4-Dichlorobenzene3106–46–795/94ND3.2ND0.05 E75----FungicidesBenomyl17804–35–290/8910.04.50.140.008 E40----Myclobutanil88671–89–090/875.65.7.018.018200----Metalaxyl57837–19–190/874.4ND.025ND600----Iprodione36734–19–790/872.21.1.029 E.018 E.8----Pentachlorophenol87–86–577/751.0ND.12 END11--Chlorothalonil1897–45–684/82ND1.2ND.715--1Gasoline hydrocarbons, oxygenates, and oxygenate degradatesMethyltert-butyl ether(MTBE)41634–04–495/9436320.850.56------Benzene71–43–283/811425.095 E.028 E5----m- andp-Xylene5106–42–3;108–38–395/941333.278.710,000----Toluene108–88–381/80129.9.49.251,000----1,2,4-Trimethylbenzene95–63–695/949.53.2.13.055 E------Ethylbenzene100–41–495/946.316.069 E2.1700----o-Xylene595–47–695/945.315.117.410,000----tert-Amyl methyl ether(TAME)994–05–895/944.21.1.045 E.034 E------

# 60 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued1,3,5-Trimethylbenzene108–67–895/943.2ND0.041 END------1-Ethyl-2-methylben-zene(o-Ethyl toluene)611–14–395/943.2ND.031 END------1-Methylnaphthalene90–12–096/963.12.1.013 E0.017 E------2-Methylnaphthalene491–57–696/963.14.2.019 E.034 E30----Styrene100–42–595/942.13.2.027 E.023 E100----Ethyltert-butyl ether(ETBE)637–92–395/941.11.1.020 E.023 E------p-Isopropyltoluene99–87–695/941.1ND.010 END------1,2,3,4-Tetramethylben-zene488–23–395/94ND2.1ND.062 E------1,2,3,5-Tetramethylben-zene527–53–795/94ND7.4ND.15------1,2,3-Trimethylbenzene526–73–895/94ND4.3ND.06------Isopropylbenzene98–82–895/94ND6.4ND.036 E700----n-Butylbenzene104–51–895/94ND1.1ND.013 E------Naphthalene91–20–395/94ND2.1ND.36 E100----Herbicides and herbicide degradatesAtrazine1912–24–990/8782875.03.4322 (2)21 (1)Simazine122–34–990/878289.74.73446Metolachlor oxanilicacid6--49/487759.63.46------Metolachlor ethanesulfonic acid6--49/4868592.01.9------Alachlor ethane sulfonicacid6--49/486159.27.37------

# Apprendix 2 **61 Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Herbicides and herbicide degradates—ContinuedMetolachlor51218–45–290/8759540.800.47700----Deethylatrazine (DEA)6190–65–490/875868.13.13------Deisopropylatrazine(DIA)1007–28–990/895863.090.12------Prometon1610–18–090/875625.19.20400----2-Hydroxyatrazine2163–68–089/885251.38 E.30 E70----Alachlor oxanilic acid6--49/485050.26.12------3,4-Dichloroaniline95–76–185/83472.4.083.009------2,4–D94–75–790/894452.76.4670----Diuron330–54–190/894224.22.1821--Acetochlor oxanilicacid6--49/483225.65.40------Acetochlor/metolachlorethane sulfonic acid2nd amide6--49/482727.10.08------Acetochlor ethane sulfonic acid6--49/482527.40.31------Bentazon25057–89–090/871816.020 E.020 E200----Acetochlor34256–82–190/871611.24.14111Terbuthylazine5915–41–390/871613.028.0272----MCPA94–74–690/871515.44.3930----Alachlor15972–60–890/871310.022.0172----Deethyldeisopropylatrazine3397–62–490/897.77.8.11 E.071 E------Triclopyr55335–06–390/89119.0.45.35400----Acetochlor sulfynilacetic acid6--49/489.111.28.17------

# 62 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Herbicides and herbicide degradates—ContinuedAlachlor ethane sulfonicacid 2nd amide6--49/489.14.50.060.070------Pendimethalin40487–42–190/877.84.6.056.02570----Dimethenamid687674–68–849/486.82.3.89.120------Dimethenamid ethanesulfonic acid6--49/486.8ND.03ND------4-Chloro-2-methylphe-nol1570–64–590/876.7ND.008 END------Imazaquin81335–37–790/896.75.6.028 E.025 E2,000----Tebuthiuron34014–18–190/876.75.7.031.023 E1,000----Trifluralin1582–09–890/876.72.3.009.006 E20----Dacthal1861–32–190/875.66.9.005.00570----Siduron1982–49–65.6ND.011 END------Alachlor sulfynilaceticacid140939–16–849/484.52.3.06.050------2,4–D methyl ester1928–38–790/874.42.3.078.063------Imazethapyr81335–77–590/894.41.1.20.026 E2,000----Metsulfuron methyl474223–64–690/894.42.2.077 E.058 E2,000----Chlorimuron-ethyl90982–32–490/893.31.1.015 E.006 E600----Flumetsulam98967–40–990/883.31.1.028 E.0497,000----Hexazinone51235–04–290/873.34.6.022.021400----Metribuzin21087–64–990/873.31.1.056.01690----Sulfometuron-methyl74222–97–290/893.3ND.009 END------Flufenacet ethane sulfo-nic acid6--49/482.32.3.10.090------2,6-Diethylaniline579–66–890/871.11.1.002 E.003 E------

# Apprendix 2 **63 Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Herbicides and herbicide degradates—ContinuedBensulfuron-methyl83055–99–690/891.1ND0.008 END1,000----Bromacil314–40–990/871.1ND.017 END70----Prometryn101–42–890/871.1ND.005 END300----Propyzamide7287–19–690/871.13.4.006 E0.007 E1----Dicamba23950–58–590/87ND1.1ND.071 E3,000----Dinoseb1918–00–990/89ND1.1ND.006 E7----Diphenamid88–85–790/89ND1.1ND.026200----Fluometuron957–51–790/89ND3.4ND.007 E4----Insecticides and insecticide degradatesDesulfinylfipronil--90/8742240.010 E0.008 E------Fipronil120068–37–390/87391.1.038.009 E------Carbaryl63–25–290/87208.0.25.03540----Fipronil sulfide120067–83–690/872012.010 E.008 E------Diazinon333–41–590/87171.1.014.0061----Fipronil sulfone120068–36–290/87131.1.012 E.007 E------Desulfinylfipronil amide--90/878.96.9.013 E.006 E------1-Naphthol90–15–390/876.71.1.015 E.013 E------Chlorpyrifos2921–88–290/875.6ND.006ND2----Propoxur114–26–190/875.6ND.005 END------3-Ketocarbofuran16709–30–190/871.11.1.026 E.02 E------Imidacloprid138261–41–390/874.41.1.042.021400----Malathion121–75–590/872.21.1.018 E.009 E50----

# 64 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Insecticides and insecticide degradates—ContinuedDieldrin60–57–190/871.1ND0.004ND0.0021 (1)--Bendiocarb22781–23–390/87ND1.1ND0.019 E9----Diazinon, oxygen analog962–58–390/87ND1.1ND.011------Dichlorvos62–73–790/87ND1.1ND.005 E.4----Malaoxon1634–78–290/87ND1.1ND.010 E------Manufacturing additivesTri(2-chloroethyl)phos-phate4115–96–896/9633310.26 E0.22 E------Tris(dichlorisopropyl)phosphate13674–87–896/962928.17 E5.5------Tributyl phosphate126–73–871/72212.8.12 E.29 E------Tri(2-butoxyethyl)phosphate78–51–396/961611.4 E.56------Triphenyl phosphate115–86–696/96158.3.1 E.16 E------Bisphenol A80–05–787/874.79.2.67 E.44 E400----5-Methyl-1H-benzotri-azole136–85–696/962.1ND.079 END------Organic synthesis compoundsAnthraquinone84–65–196/967.35.20.14 E0.10 E------Carbazole486–74–896/964.24.2.021 E.009 E------Chloromethane74–87–395/942.111.029 E.055 E30----Pavement- and combustion-derived compoundsFluoranthene4206–44–096/969.46.30.031 E0.026 E300----Pyrene4129–00–096/967.34.2.017 E.028 E200----Phenanthrene85–01–896/961.03.1.006 E.063 E------Anthracene120–12–796/961.0ND.004 END2,000----Benzo[a]pyrene50–32–896/96ND1.0ND.26 E.2--1 (1)

# Apprendix 2 **65 Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Personal-care and domestic use productsHHCB41222–05–596/9664540.21 E0.30 E------Caffeine58–08–277/746158.58.22------AHTN421145–77–796/962718.1 E.30 E------Camphor476–22–296/96259.4.021 E.021 E------Triethyl citrate (ethylcitrate)77–93–096/961617.072 E.036 E------Nonylphenol diethoxylate (total)26027–38–296/969.4114.3 E5.9 E------Triclosan3380–34–596/965.23.1.098 E.050 E------Cotinine486–56–696/964.24.2.28 E.077 E------Menthol89–78–196/964.25.2.049 E.080 E------Octylphenol monoethoxylate (total)--96/964.22.1.75 E.70 E------Indole120–72–996/963.11.0.011 E.003 E------Octylphenol diethoxylate (total) (OP2EO)426636–32–896/962.14.2.1 E.24 E------d-Limonene45989–27–596/961.02.1.044 E.075 E------4-n-Octylphenol1806–26–496/96ND1.0ND.25 E------4-tert-Octylphenol4140–66–996/96ND2.1ND.016 E------Acetophenone98–86–296/96NDNDNDND700----Plant- or animal-derived biochemicalsCholesterol57–88–596/9624101.6 E1.3 E------3-beta-Coprostanol4360–68–996/96136.31.4 E.99 E------beta-Stigmastanol19466–47–896/969.45.21.6 E1.6 E------3-Methyl-1(H)-indole(Skatole)83–34–196/964.2ND.009 END------beta-Sitosterol83–46–596/962.14.21.4 E1.0 E------

# 66 **Anthropogenic Organic Compounds in Source Water of Nine Community Water Systems that Withdraw from Streams Appendix 2.** Summary statistics and human-health benchmarks for anthropogenic organic compounds detected in source- and finished-water samples collected during thesecond 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 inboldare Maximum Contaminant Levels. CASRM,Chemical Abstracts Service Registry Number; E, estimated; AHTN, acetyl hexamethyl tetrahydronaphthalene; HHCB, hexahydrohexamethylcyclopentabenzopyran;MCPA, 2-methyl-4-chlorophenoxyaceticacid;μg/L, micrograms per liter; SW, source water; FW, finished water; BQ, benchmark quotient; <, less than; >, greater than; ND, not detected; --, none]**Compound CASRN** **1 Number of** **samples SW/FW** **Detection frequency (percent)** **Maximum concentration (μg/L)** **Human-health benchmark** **2 Number of concentrations with** **BQ > 0.1; (1) number of concentrations with** **BQ > 1 Source water** **Finished water Source water** **Finished water Source water** **Finished water**Refrigerants and propellantsTrichlorofluoromethane(CFC–11)75–69–495/941.1ND0.020 END2,000----Solventscis-1,2-Dichloroethene156–59–295/9415140.590.3270----Perchloroethene ( PCE)127–18–495/941513.11.053 E5----p-Cresol106–44–596/96156.3.075 E.10 E------Trichloroethene (TCE)79–01–695/948.46.4.061 E.031 E5----Methylene chloride(dichloromethane)475–09–295/942.117.33.385----n-Propylbenzene103–65–195/942.1ND.021 END------Acetone67–64–195/941.1143.7 E11.26,000----1,2-Dichloroethane107–06–295/94ND6.4ND.315----Carbon tetrachloride(tetrachloromethane)56–23–595/94ND32ND.365----Hexachloroethane67–72–195/94ND1.1ND.027 E.7----Methyl ethyl ketone(MEK)78–93–395/94ND8.5ND4.14,000----Tetrahydrofuran109–99–995/94ND1.1ND.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 through CAS Client ServicesSM.2HBSL values shown for carcinogens represent the low end (10-6) of the HBSL range (10-6to 10-4cancer 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 fromm-/p- ando-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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