# U.S. Department of the Interior

**U.S. Geological Survey** 

# Scientific Investigations Report 2009–5200 **National Water-Quality Assessment Program**

**Source Water-Quality Assessments**



# Anthropogenic Organic Compounds in Source Water of

**Selected Community Water Systems that Use Groundwater,**

**2002–05**

# Cover. Photographs of a pump house and public supply wells that are typical for wells sampled for this study.

Photographs by Nicholas Smith.

# Anthropogenic Organic Compounds in

**Source Water of Selected Community**

**Water Systems that Use Groundwater,**

**2002–05**

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

National Water-Quality Assessment Program

Source Water-Quality Assessments



# Scientific Investigations Report 2009–5200

**U.S. Department of the Interior**

**U.S. Geological Survey**

# U.S. Department of the Interior

KEN SALAZAR, Secretary

**U.S. Geological Survey**

Marcia K. McNutt, Director

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

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reproduce any copyrighted materials contained within this report.

Suggested citation:

Hopple, J.A., Delzer, G.C., and Kingsbury, J.A., 2009, Anthropogenic organic compounds in source water of

selected community water systems that use groundwater, 2002–05: U.S. Geological Survey Scientific

Investigations Report 2009–5200, 74 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/nawqa). The NAWQA Program is designed to answer:

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

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

ter, and where are those effects most pronounced? By combining information on water chemistry,

physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide

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

NAWQA Program completed interdisciplinary assessments and established a baseline understanding

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

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

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

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

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

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

water and groundwater. 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

Foreword

......................................................................................................................................................... ii

Abstract

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

Introduction

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

Purpose and Scope

.............................................................................................................................. 3

Acknowledgments

................................................................................................................................ 3

Study Design and Methods

.......................................................................................................................... 3

Characteristics of Selected Community Water System Wells

...................................................... 5

Compounds Monitored

........................................................................................................................ 5

Sample Collection and Protocols

....................................................................................................... 9

Analytical Methods

............................................................................................................................... 9

Quality Assurance

.............................................................................................................................. 10

Human-Health Benchmarks Used in a Screening-Level Assessment

...................................... 10

Anthropogenic Organic Compounds in Source Water Used by Community

Water Systems, 2002–05

............................................................................................................... 12

Commonly Detected Compounds

..................................................................................................... 14

Herbicide Degradates at Selected Sites

........................................................................................ 17

Comparison to Human-Health Benchmarks

................................................................................... 19

Mixtures of Compounds

..................................................................................................................... 19

Factors that May Affect Source-Water Quality

............................................................................. 21

Comparisons of Selected Organic Compounds in Source Water and Finished

Water Sampled in 2004 and 2005

................................................................................................. 24

Commonly Detected Compounds

..................................................................................................... 24

Comparison to Human-Health Benchmarks

................................................................................... 26

Comparison of Source- and Finished-Water Quality

.................................................................... 26

Nonblended Finished Water

.................................................................................................... 26

Blended Finished Water

........................................................................................................... 29

Mixtures

................................................................................................................................................ 30

Summary

........................................................................................................................................................ 30

References

.................................................................................................................................................... 33

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

organic compounds analyzed in source-water samples collected during

October 2002–July 2005

............................................................................................................ 38

Appendix 2. Selected characteristics of community water system wells sampled

for Source Water-Quality Assessments, 2002–05

................................................................. 54

Appendix 3. Summary statistics and human-health benchmarks for anthropogenic

organic compounds analyzed in source- and finished-water samples

collected during June 2004–September 2005

....................................................................... 60

# v



# Figures

1. Map showing locations of source water, finished water, and principal

aquifers throughout the United States included as part of the Source

Water-Quality Assessment (SWQA) component of the National WaterQuality Assessment (NAWQA) Program during 2002–05

....................................................... 4

2–14. Graphs showing:

2. The distribution of well depths included in Source Water-Quality

Assessments, 2002–05, varied by lithology and principal aquifer

............................... 7

3. Source-water samples collected from wells east of the Mississippi

River had more anthropogenic organic compounds detected and

greater total concentrations of compounds than did source-water

samples collected from wells west of the Mississippi River during

October 2002–July 2005

.................................................................................................... 13

4. Twelve of 258 anthropogenic organic compounds analyzed at all sites

were detected using no common assessment level in 10 percent or

more of source-water samples collected from 221 community water

system wells during October 2002–July 2005

............................................................... 15

5. Similar compounds were detected but detection frequencies were

greater for compounds detected commonly in source-water samples

collected for Source Water-Quality Assessments during October 2002–

July 2005 than in groundwater sampled for other National Water-Quality

Assessment studies for herbicides and herbicide degradates and

the disinfection by-product chloroform, the gasoline oxygenate

methyl tert -butyl ether, and solvents

.............................................................................. 17

6. Summed concentrations of degradates generally were greater than

concentrations of parent compounds for chloroacetanilide degradates

and generally were similar to or greater than concentrations of parent

compounds for triazine degradates in source-water samples collected

October 2002–July 2005

.................................................................................................... 18

7. Concentrations of commonly detected compounds were generally

less than 1 microgram per liter and generally much less than

one-tenth of human-health benchmarks for samples collected

October 2002–July 2005

.................................................................................................... 20

8. The number of anthropogenic organic compounds detected as

mixtures in source-water samples collected during October 2002–

July 2005 generally was greater in source water from shallow wells

than from deep wells

......................................................................................................... 21

9. The 12 most commonly detected compounds had greater detection

frequencies and greater numbers of compounds detected in sourcewater samples from shallower wells than from deeper wells during

October 2002–July 2005

.................................................................................................... 22

10. Large differences in occurrence of the 12 most commonly detected

compounds were not attributable to aquifer lithology although fewer

compounds generally were detected in source-water samples from

wells completed in sandstone and carbonate rocks than from wells

completed in other lithology groups. Most samples collected during

October 2002–July 2005 contained fewer than three compounds for

each of the four lithology groups

.................................................................................... 23

# vi



# Tables

1. Characteristics of principal aquifers or aquifer systems and median well

depth for sites included in Source Water-Quality Assessments, 2002–05

.......................... 6

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

Assessment studies

..................................................................................................................... 8

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

collected for Source Water-Quality Assessments, 2002–05

............................................... 11

4. Detection frequencies of compounds detected in 10 percent or more of

source-water samples by principal aquifer using no assessment level,

October 2002–July 2005

............................................................................................................. 16

5. Detection frequency of compounds detected in 10 percent or more of

source- and (or) finished-water samples collected during

June 2004–September 2005

...................................................................................................... 25



# Conversion Factors and Datums

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

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi 2 

# ) 2.590 square kilometer (km 2 

# )

Volume

gallon (gal) 3.785 liter (L)

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

# )

cubic foot (ft 3 

# ) 0.02832 cubic meter (m 3 

# )

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) 

# 11. Concentrations of commonly detected anthropogenic organic

compounds were less than human-health benchmarks in finishedwater samples collected during June 2004–September 2005

.................................... 27

12. Concentrations of anthropogenic organic compounds (excluding

disinfection by-products) in source and associated nonblended

finished water generally were similar when detected in both source

and finished water for samples collected during

June 2004–September 2005

............................................................................................. 28

13. Concentrations of anthropogenic organic compounds (excluding

disinfection by-products) in source and associated blended finished

water generally were similar when detected in both source and

finished water for samples collected during June 2004–September 2005

.............. 29

14. Both source- and finished-water samples collected during the

June 2004–September 2005 sampling typically contained mixtures of

two or more compounds

................................................................................................... 31

# vii

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 Symbols

< less than

μg/L micrograms per liter

1,1,1-TCA 1,1,1-trichloroethane

BQ benchmark quotient

BTEX benzene, toluene, ethylbenzene, and xylenes

CCR Consumer Confidence Report

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

CWS community water system

DBP disinfection by-product

DEET N,N,-diethyl- meta -toluamide

E estimated

GC/MS gas chromatography/mass spectrometry

HBSL Health-Based Screening Level

HPLC/MS high-performance liquid chromatography/mass spectrometry

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

PAH polynuclear aromatic hydrocarbon

PCE tetrachloroethene; perchloroethene

PVC polyvinyl chloride

QC quality control

SPE solid-phase extraction

SWQA Source Water-Quality Assessment

TCE trichloroethene

THM trihalomethane

USEPA U.S. Environmental Protection Agency

USGS U.S. Geological Survey

VOC volatile organic compound

# viii



# Definitions

**Term Definition** 

Benchmark quotient (BQ) Ratio of the concentration of a contaminant to its Maximum Contami

nant Level (MCL) value for a regulated compound or to its HealthBased 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.

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

more different groundwater sources. Community water systems that

blend with surface water were not analyzed.

Community water system

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

or more year-round residents and thus 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.

Concentration of potential

human-health concern As used in this report: (1) for a regulated compound with a U.S. En

vironmental Protection Agency (USEPA) drinking-water standard,

a concentration greater than the MCL; and (2) for an unregulated

compound, a concentration greater than the HBSL.

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 of

potential concern for human health, if exceeded. HBSLs are nonenforceable benchmarks that were developed by the U.S. Geological

Survey (USGS) in collaboration with the USEPA and others using

(1) USEPA Office of Water methodologies for establishing drinkingwater guidelines, and (2) the most recent USEPA peer-reviewed,

publicly available human-health toxicity information.

Human-health benchmarks As used in this report, human-health benchmarks 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; as used in this report, 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 by the USEPA.

Source water Source water is the raw (ambient) water collected at the supply well or

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 drinking-water

standard has been established. Note that a compound that is unregu

lated by the USEPA in drinking water under the Safe Drinking Water

Act may be regulated in other contexts and under other statutes.

# Anthropogenic Organic Compounds in Source Water

**of Selected Community Water Systems that Use**

**Groundwater, 2002–05**

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



# Abstract

Source water, defined as groundwater collected from a

community water system well prior to water treatment, was

sampled from 221 wells during October 2002 to July 2005

and analyzed for 258 anthropogenic organic compounds. Most

of these compounds are unregulated in drinking water and

include pesticides and pesticide degradates, gasoline hydrocar

bons, personal-care and domestic-use products, and solvents.

The laboratory analytical methods used in the study have

detection levels that commonly are 100 to 1,000 times lower

than State and Federal standards and guidelines for protecting

water quality. Detections of anthropogenic organic compounds

do not necessarily indicate a concern to human health but

rather help to identify emerging issues and track changes in

occurrence and concentrations over time.

Less than one-half (120) of the 258 compounds were

detected in at least one source-water sample. Chloroform, in

36 percent of samples, was the most commonly detected of

the 12 compounds that were in about 10 percent or more of

source-water samples. The herbicides atrazine, metolachlor,

prometon, and simazine also were among the commonly

detected compounds. The commonly detected degradates of

atrazine—deethylatrazine and deisopropylatrazine—as well as

degradates of acetochlor and alachlor, generally were detected

at concentrations similar to or greater than concentrations

of the parent herbicide. The compounds perchloroethene,

trichloroethene, 1,1,1-trichloroethane, methyl tert -butyl ether,

and cis -1,2-dichloroethene also were detected commonly. The

most commonly detected compounds in source-water samples

generally were among those detected commonly across the

country and reported in previous studies by the U.S. Geologi

cal Survey’s National Water-Quality Assessment Program.

Relatively few compounds were detected at concentra

tions greater than human-health benchmarks, and 84 percent of

the concentrations were two or more orders of magnitude less

than benchmarks. Five compounds (perchloroethene, trichlo

roethene, 1,2-dibromoethane, acrylonitrile, and dieldrin) were

detected at concentrations greater than their human-health

benchmark. The human-health benchmarks used for compari

son were U.S. Environmental Protection Agency Maximum Contaminant Levels (MCLs) for regulated compounds

and Health-Based Screening Levels developed by the U.S.

Geological Survey in collaboration with the U.S. Environ

mental Protection Agency and other agencies for unregulated

compounds. About one-half of all detected compounds do not

have human-health benchmarks or adequate toxicity informa

tion to evaluate results in a human-health context.

Ninety-four source-water and finished-water (water that

has passed through all the treatment processes but prior to

distribution) sites were sampled at selected community water

systems during June 2004 to September 2005. Most of the

samples were analyzed for compounds that were detected

commonly or at relatively high concentrations during the

initial source-water sampling. The majority of the finishedwater samples represented water blended with water from

one or more other wells. Thirty-four samples were from water

systems that did not blend water from sampled wells with

water from other wells prior to distribution.

The comparison of source- and finished-water samples

represents an initial assessment of whether compounds present

in source water also are present in finished water and is not

intended as an evaluation of water-treatment efficacy. The

treatment used at the majority of the community water systems

sampled is disinfection, which, in general, is not designed to

remove the compounds monitored in this study.

Concentrations of all compounds detected in finished

water were less than their human-health benchmarks. Two

detections of perchloroethene and one detection of trichloro

ethene in finished water had concentrations within an order

of magnitude of the MCL. Concentrations of disinfection

by-products were expected to increase in finished water rela

tive to source water because of disinfection. The MCL for

concentrations of disinfection by-products analyzed in this

study is for total trihalomethanes, and concentrations were

within an order of magnitude of the MCL in finished water

from nine sites, but only three detections of chloroform and

one detection of bromoform were within an order of magni

tude of the MCL. Concentrations of all other compounds

were more than an order of magnitude less than human-health

benchmarks.

# 2 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

About one-half (57 percent) of the detections from the

34 community water systems where finished water was not

blended with other source water were in both source and

finished water, and concentrations were similar, with the

exception of disinfection by-products. Most of the detections

were gasoline-related compounds, herbicides and herbicide

degradates, and solvents. Results for blended finished-water

samples generally were similar to nonblended finished-water

samples, and blending did not always reduce concentrations

to less than the laboratory reporting level. Differences in the

occurrence of compounds in source and finished water could

be the result of water treatment, volatilization, blending, or

analytical variability at concentrations near or less than the

laboratory reporting level. Large changes in concentration

from source to finished water of solvents in a few samples

likely are attributable to additional water treatment steps used

by the CWS to treat water known to contain elevated concen

trations of organic compounds.

Mixtures of two or more compounds were detected in

about 70 percent of source-water samples and in 82 percent

of finished-water samples. Mixtures occur more commonly

in finished water than source water because of the formation

of disinfection by-products in finished water. The poten

tial human-health significance of the frequent presence of

mixtures of organic compounds in finished water remains

largely unknown.



# Introduction

Groundwater is an important supply of drinking water in

the United States, and the study of aquifers is a large compo

nent of the U.S. Geological Survey’s (USGS) National WaterQuality Assessment (NAWQA) Program. NAWQA studies

have added to the understanding of the chemical quality of

water in locally and regionally important aquifers. Many

pesticides, volatile organic compounds (VOCs), and other

compounds are monitored as part of these aquifer studies,

which are designed to provide an overall representation of the

water-quality condition of the Nation’s aquifers.

The occurrence of anthropogenic organic compounds

in groundwater has been documented for many years (for

example, Westrick and others, 1984; U.S. Environmental

Protection Agency, 2002) and recently reported by Gilliom and

others (2006) and Zogorski and others (2006). Drinking water

is monitored routinely for regulated compounds. However,

relatively few studies have specifically focused on the quality

of source water used by community water systems (CWSs) as

well as the associated finished water, particularly for organic

compounds that are not regulated under the Safe Drinking

Water Act (U.S. Environmental Protection Agency, 2008).

Collectively, findings from these studies highlight 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. In the current study, source water is

defined as groundwater withdrawn from a CWS well prior to

water treatment, and finished water is defined as water that has

passed through all treatment processes, prior to distribution.

From 1992 to 2001, the NAWQA Program assessed the

quality of ambient surface-water and groundwater 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 Water-Quality

Assessments” (SWQAs) at selected CWSs across the United

States. The long-term goal is to complete about 30 surfacewater and 30 groundwater SWQAs by 2012 (Delzer and

Hamilton, 2007; Kingsbury and others, 2008). 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.

In addition, SWQAs are intended to provide a preliminary,

broad-based assessment of selected compounds found in

source water and the associated finished water. 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 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 SWQA 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,

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

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

Since 1999, the USEPA has required water suppliers to

provide annual drinking-water quality reports called Consumer

Confidence Reports (CCRs) to their customers ( http://www.

epa.gov/safewater/ccr/ ). CCRs are the centerpiece of the

right-to-know provisions of the 1996 Amendments to the Safe

Drinking Water Act. Each CCR provides consumers with

fundamental information about their drinking water, including

(1) the source of the drinking water, (2) a brief summary of

the susceptibility to contamination of the local drinking-water

source, (3) the concentrations (or range of concentrations) of

any contaminants found in local drinking water, as well as

their USEPA Maximum Contaminant Levels (MCLs), which

are legally enforceable drinking-water standards and are the

highest allowed concentrations of contaminants in drinking

# Study Design and Methods **3**

water, and (4) telephone numbers for additional sources of

information.

Information 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. Analytical methods used in SWQAs

include many more compounds and typically have lower

analytical reporting levels than those used in USEPA analyti

cal methods; therefore, compound detection frequencies in

SWQA reports may be higher than those reported in CCRs.



# Purpose and Scope

The primary purpose of this report is to characterize

anthropogenic organic compounds in source water of selected

CWSs that use groundwater. The focus of this report is on the

first 15 groundwater SWQAs. The aquifers monitored (here

after termed principal aquifers) as part of these efforts were

studied because they account for the majority of the estimated

withdrawals of groundwater for drinking-water supply in the

United States (Lapham and others, 2005; Maupin and Barber,

2005). This report also compares findings to previous resource

assessments. The occurrence of 258 anthropogenic organic

compounds (Appendix 1) in source water from 221 wells

sampled from 12 principal aquifers across the United States

by the NAWQA Program during October 2002 to July 2005

is described. Source-water samples were analyzed for

compounds that included pesticides and pesticide degradates,

gasoline hydrocarbons, personal-care and domestic-use prod

ucts, and solvents. An additional 3 herbicides and 16 herbicide

degradates were analyzed in samples from 73 of the 221 wells

located in areas where these compounds likely are used. 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 character

ization of the number of compounds co-occurring in source

water as mixtures. Although this study was not designed to

examine specific sources and (or) factors causing and affect

ing the occurrence and concentrations of compounds in

source water, additional perspective is added by highlighting

general patterns and associations as appropriate, including

those related to geographic location, well depth, and general

lithology.

A secondary purpose of this report is to provide compari

sons of selected compounds in source water with their

occurrence in finished water. Samples of source water, and

associated samples of finished water, were collected during

June 2004 to September 2005 from 94 of the 221 wells.

Sampling during this period generally focused on analyti

cal suites that included compounds found to occur most

commonly or at relatively high concentrations in source water

during the initial sampling (2002–05). The sampling design

and resulting comparisons were not intended to character

ize water-treatment efficacy, but to provide a preliminary indication of the potential importance of compounds found in

source water and the quality of finished water prior to distribu

tion. In general, the types of treatment used by the CWSs that

were sampled were not specifically designed to remove most

of the organic compounds monitored. Distinctions were made

in the analyses for wells that did not blend water (34 of the 94)

and wells that did blend water (60 of the 94) when compar

ing source- and finished-water concentrations. Analytical

results for source-water and finished-water samples, as well

as quality-assurance samples, are summarized in Carter and

others (2007).

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. Measured

concentrations of compounds that are regulated in drinking

water were compared to USEPA MCLs, and concentrations

of unregulated compounds were compared to Health-Based

Screening Levels (HBSLs) developed by the USGS in collabo

ration with USEPA and others (Toccalino and others, 2003).

The screening-level assessment provides an initial perspec

tive on the potential importance of anthropogenic organic

compounds detected and is not a substitute for comprehensive

risk assessment, which includes many more factors, such as

additional avenues of exposure.



# Acknowledgments

The authors thank personnel at each of the CWSs for

their assistance in the collection of samples. The authors also

acknowledge Robert Gilliom, John Zogorski, William Wilber,

Jeffrey Stoner, and Pixie Hamilton of the USGS and Philip

Berger of the USEPA for their constructive review comments.



# Study Design and Methods

CWS wells selected for SWQA monitoring met several

criteria. Specifically, wells are located in NAWQA study

areas where SWQA data can be compared to groundwater

resource-assessment data collected as part of the NAWQA

Program during 1992–2001, and wells are screened in one of

62 principal aquifers (fig. 1). Selected wells generally have

relatively high pumping rates (in comparison to other wells

in the sampling area) and are at least 1,000 meters (0.62 mile)

apart to minimize overlapping contributing areas. In general,

wells sampled in this study are considered relatively suscep

tible to anthropogenic contamination because of the large

pumping rates (generally greater than 500 gallons per minute)

and large contributing areas. The results of this study are,

therefore, not necessarily representative of many CWS wells,

particularly those with relatively small pumping rates, less

than 500 gallons per minute.

# Figure 1. Source water and finished water were assessed in 12 principal aquifers throughout the United

States as part of the Source Water-Quality Assessment (SWQA) component of the National Water-Quality

Assessment (NAWQA) Program during 2002–05. **1** River

M 

# i 

# s 

# s 

# i 

# s 

# s 

# i 

# p 

# p i 

# G

**G G** 

**G** 

# EXPLAN A TION

Coastal Lowlands aquife r system

Edwards- Trinity aquife r system Denve r Basin aquife r system California Coastal Basin aquifers

Central V alley aquife r system

Surficial aquife r system (overlying the Floridan) Floridan aquife r system Biscayne aquifer

Glacial deposits aquife r system Cambrian-Ordovician aquife r system Mississippi Embayment- T exas Coastal Uplands

aquife r system

Northern Atlantic Coastal Plain aquife r system High Plains aquifer

Rio Grande aquife r system New England crystalline- r ock aquifers

V

alley and Ridge aquifers—Carbonate- r ock aquifers

a r e patterned Hawaiian v olcanic- r ock aquifers—locally overlain by

sedimentary deposits Basin-fill aquifers

Carbonate-rock aquifers Basin and Range

Basin-fill aquifers

Basaltic-rock aquifers Columbia Plateau

Early Mesozoic aquifers Carbonate-rock aquifers

Crystalline-rock aquifers Piedmont and Blue Ridge

Basin-fill aquifers Basaltic-rock aquifers Snake Rive r Plain Principal aquifer (from U.S. Geological

Survey, 2003)

App r oximate location of g r oundwate r SWQA study a r ea

W

ells completed in the glacial deposits aquife r system 

# 4 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# Study Design and Methods **5**

The types of water treatment or prior monitoring results,

including those for compliance monitoring, were not consid

ered in the selection process. In addition, several criteria were

used to eliminate wells, including (1) proximity to coastal

or bay areas, which could be affected by saltwater intrusion;

(2) wells with strong connections to streams (under the influ

ence of surface water); and (3) wells used for injection or

withdrawal for artificial recharge.

Typically, about 15 wells were sampled in each of the

SWQA studies. In the Florida and Minnesota/Wisconsin

SWQAs, 30 wells were sampled (table 1). Fifteen wells

in both unconfined and semiconfined parts of the Floridan

aquifer system were sampled for the Florida SWQA. For the

Minnesota/Wisconsin SWQA, 15 of the sampled wells were

completed in the Cambrian-Ordovician aquifer system, and 15

of the sampled wells were completed in the glacial deposits

aquifer system.

The Kruskal-Wallis rank-sum test (Helsel and Hirsch,

1992) was used to identify differences between groups of sites

for analyses presented in this report. A p-value less than 0.05

was used to indicate statistical significance.



# Characteristics of Selected Community Water

**System Wells**

The principal aquifers sampled in this study range in

areal extent from about 6,800 to more than 950,000 square

miles (table 1); however, wells sampled for SWQAs typi

cally were clustered around one or two urban or suburban

areas. For the purpose of this study, the 221 sampled wells

were grouped into four general lithology groups: (1) uncon

solidated glacial deposits (44 wells); (2) unconsolidated and

semiconsolidated sediments, which include sand, gravel, and

to a lesser extent boulders and silt (77 wells); (3) sandstone

and carbonate rocks (72 wells); and (4) igneous and metamor

phic (crystalline) rocks (28 wells) (fig. 2 A ; table 1; Appen

dix 2). Wells completed in the unconsolidated glacial deposits

were separated from wells completed in unconsolidated and

semiconsolidated sediments because of significantly different

well depths (median depths of 124 and 523 feet (ft) below land

surface, respectively) (Kruskal-Wallis rank-sum test p-value

less than 0.0001).

Depth to water, and consequently well depth, varies

considerably among and within study areas (table 1; fig. 2 B ;

Appendix 2). Median well depths within each principal aquifer

range from 124 to 1,394 ft. The shallowest median well depth

is for wells completed in the glacial deposits aquifer system,

and the deepest median well depth is for wells completed in

the Coastal Lowlands aquifer system (table 1; fig. 2 B ; Appen

dix 2). Many of the deepest wells are located in the western

part of the Nation, and the shallowest wells are located east

of the Mississippi River. Although wells in the unconsoli

dated and semiconsolidated group have the second shallow

est median depth, the range in well depth is large (120 to 2,070 ft). Well depth and lithology for each well are presented

in Appendix 2.

CWSs that participated in SWQAs include single-well

systems and systems with multiple wells. In many cases where

systems have multiple wells, the CWSs blend water before or

after water treatment. The water-treatment process predomi

nantly used by the CWSs was disinfection with chlorine.

Additional water-treatment steps, including granular activated

carbon and air-stripping towers, were used by CWSs when

source water was known to be contaminated with organic

compounds.



# 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 contami

nants that were 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, such as arsenic and nitrate, 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 2; Appendix 1). The number of

compounds in each of the 13 categories (hereafter termed

“use groups”) ranges from 3 to 82. About one-half of the

compounds analyzed are pesticides, which include three use

groups—herbicides and herbicide degradates, insecticides

and insecticide degradates, and fungicides. About 90 VOCs

are categorized in six use groups, including disinfection

by-products; fumigant-related compounds; gasoline hydro

carbons, oxygenates, and oxygenate degradates; organic

synthesis compounds; refrigerants and propellants; and

solvents. Pesticides and VOCs have been included routinely

in data collection by the NAWQA Program since its incep

tion (1991); however, most of the compounds in the remain

ing four groups have not been analyzed previously by the

NAWQA Program. These four use groups are personal-care

and domestic-use products, such as triclosan (an anti-bacterial

agent in many hand soaps), detergent metabolites, and

fragrance compounds; manufacturing additives, such as plasti

cizers and fire retardants; pavement- and combustion-derived

compounds, which are predominantly polynuclear aromatic

hydrocarbons; and plant- and animal-derived biochemicals,

such as cholesterol.**Table 1.**Characteristics of principal aquifers or aquifer systems and median well depth for sites included in Source Water-Quality Assessments, 2002–05.[SWQA, Source Water-Quality Assessment; Mgal/d, million gallons per day]**Principal aquifer or system in which SWQA was conducted** **State(s) in which SWQA was located** **General lithologies Number of wells** **sampled Median well** **depth (feet)** **Approximate areal extent of** **aquifer (square miles)** **Withdrawals for public supply in** **2000 1** **(Mgal/d)**Basin and Range basin-fill aquifers2NevadaUnconsolidated and semiconsolidatedsediments15470163,3861,081Cambrian-Ordovician aquifer system3Minnesota, WisconsinSandstone and carbonate rocks15408177,355590Central Valley aquifer systemCaliforniaUnconsolidated and semiconsolidatedsediments1524820,305839Coastal Lowlands aquifer systemTexasUnconsolidated and semiconsolidatedsediments151,394197,211724Columbia Plateau basin-fill andbasaltic-rock aquifersWashingtonIgneous and metamorphic rocksUnconsolidated and semiconsolidatedsediments1327504188; 1,17143,521223Denver Basin aquifer systemColoradoSandstone and carbonate rocks125616,78817Edwards-Trinity aquifer systemTexasSandstone and carbonate rocks1584875,012411Floridan aquifer system5FloridaSandstone and carbonate rocks30563112,6841,555Glacial deposits aquifer system3,6,7Connecticut,Minnesota, Ohio,WisconsinUnconsolidated glacial deposits44124953,1481,950High Plains aquiferNebraskaUnconsolidated and semiconsolidatedsediments15292176,534389Piedmont and Blue Ridge crystallinerock aquifers8Maryland, VirginiaIgneous and metamorphic rocks1530086,48992Rio Grande aquifer systemNew MexicoUnconsolidated and semiconsolidatedsediments151,28729,2492401Maupin and Barber (2005).2Rosen and others (2006).3Tornes and others (2007).4Depths for two wells; median not calculated.5Metz and others (2006).6Trombley and others (2007).7Thomas (2007).8Banks and Reyes (2009). 

# 6 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# Figure 2. The distribution of well depths included in Source Water-Quality Assessments, 2002–05, varied by A , lithology; and

B

, principal aquifer. [Color-coding of principal aquifer corresponds to color-coding of the lithology group.]WELL DEPTH, IN FEET



# U n c o n s o l i d a t e d

g l a c i a l deposits U n c o n s o l i d a t e d a n d

s e m i c o n s o l i dated

sediments Sandstone a n d

carbonate rocks Igneous and

metamorphic rocks 0 4 5 0 9 0 0 1

, 3 5 0 1

, 8 0 0 2

, 2 5 0



# LITHOLOGY

, I N O R D E R O F I N C R E A S I N G M E D I A N W E L L D E P T H (77) (72) (28) (44)



# A

**EXPLANATION**

Number of values

75th percentile

Median

25th percentile Outlier data value more

than 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

Interquartile

range (28)



# B (15) (15) (12) (15) (15) (30) (44) (15) (15) (15) (15) (15)

1 2 3 4 5 6 7 8 9 10 11 12



# P R I N C I P A L A Q U I F E R

, I N O R D E R O F I N C R E A S I N G M E D I A N W E L L D E P T HWELLDEPTH,INFEET



# 0 4 5 0 9 0 0 1

, 3 5 0 1

, 8 0 0 2

, 2 5 0 

# 1

2

3

4

5

6

7

8

*9

10

11

12 Glacial deposits aquifer system

Central V alley aquifer system

High Plains aquifer

Piedmont and Blue Ridge

crystalline-rock aquifers

Cambrian-Ordovician aquifer

system

Basin and Range basin-fill

aquifers

Denver Basin aquifer system

Floridan aquifer system

Columbia Plateau basin-fill

and basaltic-rock aquifers

Edwards- T rinity aquifer system

Rio Grande aquifer system

Coastal Lowlands aquifer

system

* T

wo of the wells were com-

pleted in unconsolidated and

semiconsolidated sediments. 

# Study Design and Methods **7**

# Table 2. Primary-use groups for compounds analyzed for Source Water-Quality Assessment studies (from Carter and others, 2007).

[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 compounds Chemicals that may be present in commercial fumigant products, which produce a

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

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

ents as well as their degradates and their manufacturing by-products. 9

Fungicides Pesticides used to kill unwanted fungi. 7

Gasoline hydrocarbons,

oxygenates, and oxygenate

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

that are highly volatile, contain only carbon and hydrogen atoms, and are common

ingredients in gasoline and other petroleum products. Of these compounds,

BTEX compounds are among those present in the highest proportions in gasoline.

Oxygenates, such as methyl tert -butyl ether (MTBE), are compounds that contain

only carbon, hydrogen, and oxygen atoms and commonly are added to gasoline to

improve the efficiency of combustion. Oxygenate degradates are formed during the

production, storage, release, and (or) use of gasoline oxygenates or following their

release into the environment. 27

Herbicides and herbicide

degradates 1 

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

from the transformation of the parent herbicide following application (degradates). 82

Insecticides and insecticide

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

from the transformation of the parent insecticide following application (degra

dates). 51

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

improve the effectiveness of the product, including plasticizers (to increase the

flexibility of plastics), fire retardants, corrosion inhibitors, and pesticide adjuvants. 7

Organic synthesis compounds Chemicals used as precursors in the manufacture of other organic compounds. Chlo

roethylene (vinyl chloride), for example, is an organic synthesis compound used to

produce polyvinyl chloride (PVC) plastics. 18

Pavement- and combustionderived 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 or ganic

compounds, most commonly gasoline, oil, coal, and other fossil fuels. 5

Personal-care and domesticuse products Compounds that are present in commercial products sold for personal or residential

use, such as fragrances, pharmaceuticals, insect repellants, dyes, deter gents, 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

blowing agents in the manufacture of packaging and other highly porous materi

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

devices. 3

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

trichloroethene (TCE) and perchloroethene (tetrachloroethene, PCE). 33

Total number of compounds 277

1 

# Herbicides and herbicide degradates include 3 herbicides and 16 herbicide degradates monitored in additional samples collected at 73 selected sites. A total

of 258 compounds were monitored at all sites. 

# 8 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# Study Design and Methods **9**



# Sample Collection and Protocols

Source-water samples were collected at the wellhead

before any treatment and processed using standard USGS

sampling protocols (Koterba and others, 1995). The 221 wells

were sampled one time during October 2002 to July 2005 and

were analyzed for 258 compounds (Appendix 1). Samples

from a subset of 73 wells also were analyzed for an additional

3 herbicides and 16 herbicide degradates in study areas where

these herbicides likely are used.

During a second sampling phase from June 2004 to

September 2005, source and finished water were sampled at

94 sites (Carter and others, 2007). Most of these source- and

finished-water sample pairs (79) were from sites at which

source water was sampled a second time. These 79 wells were

selected for resampling source water and collecting a finishedwater sample because several compounds were detected or

compounds were detected at high concentrations in the first

source-water sample. The source- and finished-water samples

from these sites generally were analyzed by using the analyti

cal methods that included the compounds detected in the first

sample. Because relatively few compounds were detected in

source-water samples collected during 2003 from the Denver

Basin aquifer system, these sites were not sampled during

the second phase, and thus, no finished-water samples were

collected for these sites. Since 2005, the SWQA studies are

now conducted in one sampling phase where both source

water and finished water associated with 15 wells are sampled

at the same time. All studies included in this report followed

the two-phase sampling approach with the exception of the

Rio Grande aquifer system.

Finished-water samples were collected following all of

the treatment steps and prior to the water entering the distri

bution system. 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 the

samples prior to analysis (Winslow and others, 2001). As

a result, finished-water samples are considered to be repre

sentative of the quality of water prior to distribution but not

necessarily representative of the quality of water at the tap.

The additional contact time of the water with disinfectants

in the distribution system may allow some compounds to be

transformed or degraded, whereas other compounds, such as

disinfection by-products, may continue to form in the distribu

tion system.



# Analytical Methods

Samples were analyzed using USGS approved analyti

cal methods at the USGS National Water Quality Laboratory

(NWQL) in Denver, Colorado, including gas chromatography/

mass spectrometry (GC/MS) and high-performance liquid chromatography/mass spectrometry (HPLC/MS). Samples

for VOC analyses were chilled upon collection, and samples

for one of the two VOC analytical methods was preserved

with 1:1 hydrochloric acid. Samples for both VOC analytical

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

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

analyses of pesticides and other semivolatile compounds were

filtered in the field through a 0.7-micron baked glass-fiber

filter and chilled. These samples were extracted at the NWQL

on solid-phase extraction (SPE) cartridges to concentrate the

analytes from the filtered samples. SPE cartridges then were

eluted with a solvent, and the extracts were analyzed by either

GC/MS or HPLC/MS methods (Zaugg and others, 1995, 2002;

Lindley and others, 1996; Furlong and others, 2001; Sand

strom 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 0.003 to 6.0 micrograms per

liter (μg/L) (Appendix 1) with a median of 0.06 μg/L. Some

reported concentrations are qualified as estimated (indicated

with an “E”), which means 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 therefore, concentrations are always reported

as estimated.

The sensitivity of the analytical methods differs among

compounds and can affect the detection frequencies of the

compounds analyzed. Compounds with low LRLs likely will

be detected more commonly than those with high reporting

levels, given equal concentration distributions in the environ

ment. In order to compare detection frequencies between

compounds, a common assessment level is needed to account

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

ment level of 0.1 μg/L is used. 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.

Unless otherwise specified, no assessment level was used.

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

qualified as estimated.

# 10 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**



# Quality Assurance

Similar types and numbers of quality-control (QC)

samples were collected in each of the study areas. These QC

samples, including field blanks, replicates, and matrix spikes,

were evaluated together because sampling equipment and

cleaning procedures, as well as sample collection and process

ing, were the same for all sites. Field blanks were processed

in the field in the same manner as environmental samples

and consisted of nitrogen-purged organic-free blank water.

Field-blank results are used to characterize the positive bias

or contamination that may affect sample analytical results.

Source-solution blanks, which also consisted of nitrogenpurged organic-free blank water, were analyzed for a subset

of field blanks and analytical methods to assure the integrity

of the water used for blanks. Replicate samples are used to

characterize the amount of variability associated with sample

collection, processing, and analysis. Matrix spikes provide

information about recoveries of organic compounds.

The majority of the field-blank data did not indicate

potential contamination that could bias the environmental data.

Overall, 254 of the 277 compounds monitored either were not

detected or were detected in less than 5 percent of field blanks.

However, field blanks collected during this study indicated

that some compounds potentially were affected by contamina

tion that could bias the environmental data (table 3). Data for

these compounds were removed from the dataset or results

were censored to account for this potential bias as follows.

Phenol and N,N-diethyl- meta -toluamide (DEET) were

detected in 82 and 39 percent of field blanks, respectively,

and were removed from the dataset because of pervasive

contamination in field blanks. Although the field-blank data

did not identify systematic error that affected sample results

for these compounds, the quality of data for both compounds

was unknown.

Three compounds—benzophenone, isophorone, and

para -nonylphenol—were removed from the dataset because

of systematic contamination from the “quenching” reagents

added to finished-water samples (table 3). 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. These three compounds

were detected at low concentrations in most of the blanks,

indicating that the “quenching” reagents are a source of

contamination for the three compounds. Follow-up analyses

by the NWQL confirmed the presence of these compounds in

the buffer added to samples (Mark Sandstrom, U.S. Geologi

cal Survey, oral commun., 2005).

Nineteen additional compounds were detected in more

than 5 percent of field blanks (table 3). The occurrence of

these compounds in field blanks was evaluated to determine

if potential bias was associated with specific SWQAs. If a

compound was detected in 50 percent or more of field blanks

from a SWQA, all of the data for that constituent from that

SWQA were removed from the dataset. 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 maximum field-blank concentration to

account for the potential bias indicated by field blanks. If a

compound was detected in less than 5 percent of the field

blanks remaining after removal of the field blanks from

SWQAs with greater than 50-percent occurrence, no addi

tional censoring was done.

Twenty-one compounds were detected in less than

5 percent of field blanks and usually at concentrations less

than the LRL (Appendix 1). Data for these compounds are

included in this report because the potential for contamination

in the environmental samples was considered to be low and

did not affect the overall interpretation of the study.

Prior to implementation of the addition of ascorbic acid

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

phase of sampling, the NWQL evaluated the effect of this

quenching agent and buffer on compound recoveries. Results

indicated that recoveries were not affected by the addition

of these reagents (Mark Sandstrom, U.S. Geological Survey,

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

sampling phase, matrix spikes were collected to further char

acterize analytical method performance with the addition of

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

indicate that median spike recoveries generally were within

acceptable limits for most compounds that are not always

reported as estimated concentrations (Valder and others,

2008). Results of paired spiked finished-water samples, one

with quenching reagents and the other without, indicate that

several compounds degrade in the presence of free chlorine

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

additional contact time of finished water in the distribution

system would affect the concentrations of several compounds

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

(2007).



# Human-Health Benchmarks Used in a

**Screening-Level Assessment**

Concentrations of regulated compounds—those with

USEPA MCLs—were compared to MCLs, and concentra

tions of unregulated compounds—those without USEPA

MCLs—were compared to Health-Based Screening Levels

(HBSLs), when available (Toccalino, Norman, and others

2006). Comparisons to human-health benchmarks are used in

this report to identify concentrations of potential human-health

concern and to provide an initial perspective on the potential

importance of the anthropogenic organic compounds detected.

As of June 2008, 38 of the compounds monitored in this study

have an established USEPA MCL (U.S. Environmental Protec

tion Agency, 2006) and 112 have an HBSL (Toccalino and

others, 2008). HBSLs have not been developed for the remain

ing 127 unregulated compounds because of a lack of toxicity

information. Therefore, the potential human-health signifi

cance of these compounds cannot be evaluated at this time

# Table 3. Summary of compounds detected in 5 percent or more of field blanks collected for Source Water-Quality Assessments,

2002–05.

[N, number of field blanks; USGS, U.S. Geological Survey; SWQAs, Source Water-Quality Assessments; μg/L, micrograms per liter; NA, not applicable]



# Compound (N) **USGS**

**parameter**

**code Number of SWQAs** 

**for which compound**

**was removed from all**

**samples in the dataset Number of detections** 

**censored at the**

**maximum field-blank**

**concentration Maximum** 

**field-blank**

**concentration**

**(μg/L)**

Compounds removed from dataset

Benzophenone (38) 62067 15 All data removed 0.15

Isophorone 1 

# 34409 15 All data removed .006

N,N-diethyl- meta -toluamide (DEET) (39) 62082 15 All data removed 1.1

para -Nonylphenol (total) (38) 62085 15 All data removed 2.6

Phenol (27) 34466 15 All data removed 1.9

Compounds removed from SWQA

1,2,4-Trimethylbenzene (41) 77222 2 0 0.036

Alachlor ethane sulfonic acid (6) 50009 1 0 .03

Benzene (41) 34030 2 0 .013

Chlorobenzene (41) 34301 1 0 .028

Chloroform (41) 32106 3 0 .198

Ethylbenzene (41) 34371 2 0 .022

m - and p -Xylene (41) 85795 3 0 .08

Menthol (38) 62080 1 0 .043

Methylene chloride (41) 34423 2 0 .094

o -Xylene (41) 77135 2 0 .021

Tri(2-butoxyethyl)phosphate (38) 62093 1 0 2.8

Triphenyl phosphate (38) 62092 1 0 .088

Compounds removed from SWQA or censored at the maximum field-blank concentration

Acetone (41) 81552 3 4 11.7

Acetophenone (38) 62064 2 1 .3

Caffeine (25) 50305 3 2 .004

Carbon disulfide (41) 77041 2 10 .109

Toluene (41) 34010 6 6 .05

Compounds censored at the maximum field-blank concentration

Bisphenol A (34) 62069 NA 19 0.94

p -Cresol (38) 62084 NA 2 .013

1 

# Detected in less than 5 percent of samples; however, the data were removed because of systematic contamination from reagents added to finished-water

samples. 

# Study Design and Methods **11**

# 12 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

(Toccalino, Rowe, and Norman, 2006). These human-health

benchmarks typically are concentrations in drinking water that

are not anticipated to cause adverse effects from a lifetime of

exposure (Toccalino, 2007; U.S. Environmental Protection

Agency, 2008).

MCLs are legally enforceable USEPA drinking-water

standards that set the maximum permissible level of a

contaminant in water that is delivered by public water systems

(U.S. Environmental Protection Agency, 2008). MCLs are

applicable only to finished-water samples in the regulatory

framework; however, an assessment of source-water concen

trations in relation to 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.

HBSLs are benchmark concentrations of compounds in

water that, if exceeded, may be of concern to human health.

HBSLs are non-enforceable benchmarks that were developed

by the USGS in collaboration with the USEPA and others

using: (1) USEPA Office of Water methodologies for estab

lishing drinking-water guidelines, and (2) the most recent,

USEPA peer-reviewed, publicly available human-health

toxicity information (Toccalino and others, 2003; Toccalino

and others, 2006). As a result, HBSL values are equivalent to

existing USEPA drinking-water guideline values, such as Life

time Health Advisory and Cancer Risk Concentration values

(when they exist), except for unregulated contaminants for

which more recent toxicity information has become available

(Toccalino, 2007).

Concentrations of compounds in single samples of both

source water and finished water were compared to humanhealth benchmarks as a screening-level assessment. This

comparison identifies compounds with concentrations that

approached or were greater than benchmarks to aid in assess

ing their potential relevance to human health. For these

comparisons, benchmark quotient (BQ) values—the ratio of a

concentration of a compound to its benchmark—were calcu

lated. A BQ value greater than 1 represents a concentration

greater than a benchmark. A BQ value greater than 0.1 can

be used to identify compounds that may warrant additional

monitoring (Toccalino, Rowe, and Norman, 2006). A thresh

old BQ of 0.1 is consistent with various State and Federal

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

Agency, 1998). Monitoring for these contaminants would

enable analysis of trends in their occurrence and may provide

an early indication if concentrations approach human-health

benchmarks. 

# Anthropogenic Organic Compounds

**in Source Water Used by Community**

**Water Systems, 2002–05**

Source-water samples were collected from 221 wells

during October 2002 to September 2005. All samples were

analyzed for 258 anthropogenic organic compounds, and

samples from a subset of 73 wells were collected and analyzed

for an additional 3 herbicides and 16 degradates in areas where

these herbicides likely are used. Because these compounds

were not monitored at all of the wells, the following character

ization focuses on compounds that were monitored at all sites,

and the 3 herbicides and 16 herbicide degradates are described

separately.

More than one-half (138) of the 258 compounds moni

tored at all sites were not detected in any source-water samples

(5 compounds were removed from the dataset because of dataquality concerns). Of the 120 compounds that were detected,

52 were detected only once (Appendix 1). Concentrations of

compounds typically were less than 1 μg/L, and only 6 percent

of the concentrations of detected compounds were greater than

1 μg/L. A variety of compounds were detected as indicated

by the fact that at least two compounds from each of the

13 use groups in which the compounds were categorized were

detected (Appendix 1). The laboratory analytical methods

used in this study have detection levels that are commonly

100 to 1,000 times lower than State and Federal standards and

guidelines for protecting water quality. Detections of these

compounds do not necessarily indicate a concern to human

health but rather help to identify emerging issues and track

changes in occurrence and concentrations over time.

Detections of compounds in source water varied region

ally, as shown by comparisons between wells located west of

the Mississippi River (total of 117 wells) and those east of or

near the Mississippi River (total of 104 wells; fig. 3); wells in

Minnesota were included with wells east of the Mississippi

River. Specifically, more compounds generally were detected

per sample from wells in principal aquifers east of the Missis

sippi River than west of the Mississippi River (Kruskal-Wallis

rank-sum test p-value = 0.0001; fig. 3 A ). Seventy-nine percent

of samples from wells east of the Mississippi River had at

least one compound detected and as many as 35 compounds

(median = 3) detected in one sample. In contrast, 65 percent

of samples from wells west of the Mississippi River had at

least one compound detected and as many as 18 compounds

(median = 1) detected in one sample. More herbicides and

herbicide degradates were detected in samples from wells east

# Figure 3. Source-water samples collected from wells east of the Mississippi River had A , more anthropogenic organic compounds

detected; and B , greater total concentrations of compounds than did source-water samples collected from wells west of the Mississippi

River during October 2002–July 2005. Ea s t We s t

LOCATION RELATIVE TO THE MISSISSIPPI RIVERTOTAL CONCENTRATION OF COMPOUNDS IN A SAMPLE, IN MICROGRAMS PER LITER



# 0.001 0.01 0.1



# 1 10 100 1,000 10,000 25

20

15

10

5

0 35

30 40NUMBER OF COMPOUNDS DETECTED PER SAMPLE



# B 104 117 104 117

**EXPLANATION**



# Number of values

75th percentile

Median

25th percentile Outlier data value more

than 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 117

Interquartile

range 

# A **Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 13** 

# 14 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

of the Mississippi River than in samples from wells west of

the Mississippi River. Some of the factors that may account

for a larger number of detected compounds in the east include

generally higher groundwater recharge rates, shallower well

depths, shallower depths to groundwater, greater population

densities, and a greater intensity of herbicide use in agricul

tural areas than in the west (Gilliom and others, 2006). The

total concentrations of compounds detected in samples from

wells east of the Mississippi River were greater (median of

0.172 μg/L) than those in the west (median of 0.036 μg/L;

fig. 3 B ).

Compounds were characterized in this report as

commonly occurring when they were detected in about

10 percent or more of samples using no assessment level. By

this definition, 12 compounds were detected commonly (fig. 4;

Appendix 1). The commonly detected compounds represented

four of the use groups, including disinfection by-products;

gasoline hydrocarbons, oxygenates, and oxygenate degradates;

herbicides and herbicide degradates; and solvents.



# Commonly Detected Compounds

Most of the 258 compounds monitored at each site were

detected infrequently; only 12 compounds were detected in

about 10 percent or more of samples using no assessment

level (fig. 4; Appendix 1). Chloroform, deethylatrazine (a

degradate of atrazine), atrazine, and perchloroethene (PCE)

were detected in about 20 percent or more of samples. Fewer

compounds were detected when a common assessment level

of 0.1 μg/L was used; only two compounds—chloroform and

PCE—were detected in 10 percent or more of source-water

samples (fig. 4). Detection frequencies of most of the other

compounds were less than 5 percent when using a common

assessment level. The smaller detection frequencies that were

based on a common assessment level compared to using no

assessment level illustrate the low concentrations at which

many of these compounds were detected.

Samples from 5 of the 12 principal aquifers accounted for

the majority of the detections of these compounds; the average

detection frequencies for these 5 principal aquifers were

greater than 20 percent and as large as 45 percent (table 4).

Sampled wells in 4 of these 5 principal aquifers—the glacial

deposits aquifer system, Central Valley aquifer system, High

Plains aquifer, and Piedmont and Blue Ridge crystallinerock aquifers—had the shallowest median well depths of

the 12 aquifers (fig. 2 B ). Sampled wells in the fifth principal

aquifer, the Edwards-Trinity aquifer system, were deeper and

ranked 10 of 12 in median well depth.

Chloroform was the most commonly detected compound

in this study and was detected in 36 percent of samples. Chlo

roform was detected in 8 of the 12 principal aquifers; chloro

form was removed from the datasets for three of the SWQAs

because of data-quality concerns (table 3) and was not

detected in any wells in the Rio Grande aquifer system, which

was the principal aquifer with wells with the second deepest median well depth (table 4; fig. 2 B ). In general, chloroform

was detected more commonly in principal aquifers with the

shallowest median well depths and less commonly in princi

pal aquifers with the deepest median well depths. In samples

from several of the principal aquifers, one or more additional

disinfection by-products (DBPs)—bromodichloromethane,

dibromochloromethane, and (or) bromoform—were detected

when chloroform was detected. This co-occurrence indicates

that recharge of chlorinated water to the aquifers is a possible

source of chloroform and is consistent with previous findings

from the NAWQA Program (Ivahnenko and Barbash, 2004;

Ivahnenko and Zogorski, 2006). Potential sources of chloro

form and other DBPs include chlorinated water used to irrigate

lawns, golf courses, parks, gardens, and other areas; septic

systems; regulated discharge of chlorinated waters to recharge

facilities; and leakage of chlorinated water from swimming

pools, spas, and distribution systems used for drinking water

or wastewater sewers (Ivahnenko and Barbash, 2004).

One-half of the most commonly detected compounds

were herbicides or herbicide degradates (table 4; fig. 4). The

common detection of these compounds may be related to their

widespread use, the large number of compounds analyzed in

this use group compared to the other 12 use groups, and lower

LRLs compared to other compounds (Appendix 1). Atrazine,

simazine, prometon, and metolachlor have both agricultural

and nonagricultural uses. Atrazine and metolachlor are two of

the most heavily used agricultural herbicides with much of the

use for corn production, but they also are used in urban areas

(Gilliom and others, 2006). Simazine and prometon are used

in nonagricultural areas for weed control and along rights-ofway, but simazine also is used for agriculture (Gilliom and

other, 2006). Deethylatrazine, a degradate of atrazine, was

detected more commonly than atrazine. Deisopropylatrazine,

a degradate of both atrazine and simazine, was detected less

commonly than either parent compound. Gilliom and others

(2006) found that natural features, such as hydrogeology and

soil characteristics, and agricultural management practices,

such as irrigation and draining, are stronger factors than the

influence of land use and pesticide use on the geographic

distribution of pesticides in groundwater.

The remaining five commonly occurring compounds

are in two use groups: gasoline hydrocarbons, oxygenates,

and oxygenate degradates; and solvents (table 4; fig. 4). The

gasoline oxygenate methyl tert -butyl ether (MTBE) was

used voluntarily by refineries for the Nation’s Reformulated

Gasoline Program, and MTBE production peaked in the

1990s (Zogorski and others, 2006). In a national assessment

of source waters used by CWSs, MTBE was one of the most

commonly detected VOCs (Carter and others, 2006). Detec

tions of MTBE in groundwater, after only being used since the

1990s, indicate how quickly mobile and persistent compounds

can affect groundwater quality (Zogorski and others, 2006).

Also, the occurrence of relatively recently introduced

compounds in source water is a potential indicator of aquifer

susceptibility because the presence of MTBE indicates that a

component of recent recharge is contributing to a well.

# Figure 4. Twelve of 258 anthropogenic organic compounds analyzed at all sites were detected using no

common assessment level in 10 percent or more of source-water samples collected from 221 community

water system wells during October 2002–July 2005. Only two compounds were detected in 10 percent or

more of samples when a common assessment level was used. [DBP, disinfection by-product; gasoline

oxygenate is in the gasoline hydrocarbons, oxygenates, and oxygenate degradates use group.] DETECTION FREQUENCY, IN PERCENT

Assessment level of 0.1 microgram per liter

All detections **EXPLANATION** 50 20 30 40 10 0 

# cis-1,2-Dichloroethene

1,1,1-Trichloroethane Trichloroethene Perchloroethene Metolachlor

Prometon Deisopropylatrazine Simazine Atrazine Deethylatrazine Methyl tert -butyl ether Chloroform DBP

Gasoline oxygenate

Herbicides

and

herbicide

degradates

Solvents 

# Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 **15**

Four solvents—PCE, trichloroethene (TCE), cis -1,2-

dichloroethene ( cis -1,2-DCE), and 1,1,1-trichloroethane

(1,1,1-TCA)—were detected commonly, and generally at

higher concentrations than herbicides and herbicide degra

dates (Appendix 1). PCE was detected in all principal aquifers

with the exception of wells in the Coastal Lowlands aquifer

system (table 4), which had some of the deepest wells sampled

in this study. The common occurrence of these solvents in

groundwater is related to widespread use, relatively high

solubility, and the fact that they are not readily degraded in

groundwater, except under reducing conditions (Pankow and

Cherry, 1996; Beek, 2001). Generally, two or more of these

solvents were detected in the same sample. The co-occurrence

of TCE and cis -1,2-DCE with PCE in some cases could be the

result of degradation of PCE to these compounds. However,

both TCE and cis -1,2-DCE have the potential to be primary contaminants because of their use in industrial and commer

cial settings. Determining whether the occurrence of these

compounds is related to degradation or use is beyond the

scope of this report.

The compounds detected in 10 percent or more of

samples in this study generally correspond to those detected

most commonly in groundwater across the country as part

of the NAWQA Program, although detection frequen

cies generally were higher in this study than in previous

NAWQA studies (fig. 5). Deethylatrazine, atrazine, sima

zine, prometon, and metolachlor were the most commonly

detected pesticides in groundwater sampled by the NAWQA

Program during 1992–2001 (fig. 5 A ; Gilliom and others,

2006). Similarly, chloroform, which was the most commonly

detected compound in this study, also was the most commonly

detected VOC in aquifers sampled by the NAWQA Program**Table 4.**Detection frequencies of compounds detected in 10 percent or more of source-water samples by principal aquifer using no assessment level, October 2002–July 2005.[Principal aquifers are listed in order of shallowest to deepest median well depth. Numbers inboldtype indicate detection in more than 50 percent of samples. DBP, disinfection by-product; MTBE, methyltertbutyl ether; --, data removed from dataset because of data-quality concerns; NA, not applicable]**Principal aquifer Average** **detection frequency of the** **12 commonly** **detected compounds** **(percent) DBP** **Gasoline oxygen** ******ate Herbicides and herbicide degradates** **Solvents Chloro** **form MTBE** **Deethyl- atrazine** **Atrazine Simazine** **Deiso -** **propyl- atrazine** **Prome -** **ton Metol-** **achlor Per-** **chloro- ethene** **Tri- chloro-** **ethene cis-** **1,2-Di- chloro-** **ethene 1,1,1-** **Tri- chloro-** **ethane**Glacial deposits aquifersystem27433236303016251427301436Central Valley aquifersystem338776760605301340707High Plains aquifer21200606013130132727130Piedmont and Blue Ridgecrystalline-rock aquifers145--6710080335427732013720Cambrian-Ordovicianaquifer system1320020200077733407Basin and Range basin-fillaquifers93372020770013070Denver Basin aquifersystem14--88800808000Floridan aquifer system13433332313717013330Columbia Plateau basinfill and basaltic-rockaquifers8270713707777130Edwards-Trinity aquifersystem226005347137137531300Rio Grande aquifer system300000000713130Coastal Lowlands aquifersystem11300000000000Number of principalaquifers in which thecompound was detectedNA9610108777119841Average calculated using 11 compounds. 

# 16 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# Figure 5. Similar compounds were detected but detection frequencies were greater for compounds detected commonly in

source-water samples collected for Source Water-Quality Assessments during October 2002–July 2005 than in groundwater

sampled for other National Water-Quality Assessment studies for A , herbicides and herbicide degradates; and B , the

disinfection by-product chloroform, the gasoline oxygenate methyl tert -butyl ether, and solvents. 

# A

**Source Water-Quality Assessment**

**sites (2002−2005)**

**National groundwater pesticide data**

**(1992−2001) (Gilliom and others, 2006)**

All detections

Detections equal to or greater than

0.1 microgram per liter

All detections

Detections equal to or greater than

0.1 microgram per liter **EXPLANATION**

**National groundwater volatile organic**

**compound data (1985−2001)**

**(Zogorski and others, 2006)**

All detections

Detections equal to or greater than

0.2 microgram per liter Atrazine Deethylatrazine

Metolachlor Simazine

Prometon

0 10 20 30 40



# DETECTION FREQUENCY, IN PERCENT 

# B

cis-1,2-Dichloroethene

1,1,1-Trichloroethane Trichloroethene Perchloroethene Methyl tert -butyl ether Chloroform

Solvents Gasoline oxygenate Disinfection by-product Herbicides and herbicide degradates 

# Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 **17**

during 1985–2001 (Zogorski and others, 2006; fig. 5 B ) and

in a national study of source water from CWSs that included

groundwater and surface-water supplies (Grady, 2003).

The compounds MTBE, PCE, TCE, and 1,1,1-TCA also

were among the most commonly detected VOCs in aquifers

sampled by the NAWQA Program (Zogorski and others, 2006;

fig. 5 B ). Of the 12 commonly detected compounds in this

study, cis -1,2-DCE is the only compound that was not among

the most commonly detected VOCs in the national NAWQA

VOC study during 1985–2001.

The higher detection frequencies for most of the

commonly detected compounds in this study as compared to

the detection frequencies in previous national studies (Gilliom

and others, 2006; Zogorski and others, 2006; fig. 5) may

be related to the type of wells sampled. Many of the wells

sampled for the NAWQA Program were relatively low-capac

ity wells, such as domestic wells. The CWS wells sampled in this study are relatively high capacity and likely have larger

contributing areas than do most domestic wells. Zogorski

and others (2006) also observed larger detection frequencies

in samples from public-supply wells than in samples from

domestic wells.



# Herbicide Degradates at Selected Sites

Additional samples were collected from 73 wells in

the Cambrian-Ordovician aquifer system, glacial deposits

aquifer system, High Plains aquifer, Piedmont and Blue Ridge

crystalline-rock aquifers, and Rio Grande aquifer system and

analyzed for 3 herbicides and 16 degradates. These degradates

were analyzed because parent herbicides had potential use in

these study areas and because of the similar or greater persis

-

# Figure 6. Summed concentrations of degradates generally were greater than concentrations

of parent compounds for chloroacetanilide degradates and generally were similar to or greater

than concentrations of parent compounds for triazine degradates in source-water samples

collected October 2002–July 2005. [Sum of acetochlor degradates: acetochlor ethane sulfonic

acid and acetochlor oxanilic acid; alachlor degradates: alachlor ethane sulfonic acid, alachlor

ethane sulfonic acid 2nd amide, and alachlor oxanilic acid; metolachlor degradates: metolachlor

ethane sulfonic acid and metolachlor oxanilic acid; atrazine degradates: deethylatrazine,

deisopropylatrazine, 2-hydroxyatrazine, and deethyldeisopropylatrazine.] 0.001 0.01 0.1 1 10 0.001 0.01 0.1

1 10SUMMED DEGRADATE CONCENTRATION, IN MICROGRAMS PER LITER



# PARENT CONCENTRATION, IN MICROGRAMS PER LITER 1:1 

# Nondetections set to 0.001

Atrazine (4) Acetochlor (2)

Alachlor (3)

Metolachlor (2)

**Triazine Chloroacetanilides** 

**Number of degradate**

**compounds detected** (2) 

# 18 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

others, 2004). These results highlight the fact that information

on the occurrence and concentrations of degradates may be as

important as information for the parent compound for some

pesticides particularly if the degradate toxicity or mode of

action is similar to that of the parent compound.

Acetochlor, alachlor, and metolachlor degradates do not

have drinking-water standards but are listed on the USEPA

drinking-water Contaminant Candidate List and are included

in the Unregulated Contaminant Monitoring Program (U.S.

Environmental Protection Agency, 2007a). The USEPA

uses occurrence data along with information on health risks,

analytical methods, and treatment technologies to determine tence of some degradates relative to the parent compound

(Thurman and others, 1992; Kalkhoff and others, 1998).

Of the chloroacetanilide herbicides detected, alachlor

and metolachlor degradates generally were detected more

commonly, and summed degradate concentrations generally

were greater than the parent herbicide concentration (fig. 6;

Appendix 1). Acetochlor and its degradates were detected in

a sample from one well. The summed degradate concentra

tions of the triazine herbicide atrazine generally were similar

to or greater than atrazine concentrations (fig. 6). A similar

relation was observed between concentrations of these same

parent herbicides and their degradates in groundwater samples

collected in the Upper Illinois River Basin (Groschen and

# Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 **19**

whether any of the listed pesticide degradates are candidates

for future drinking-water standards.



# Comparison to Human-Health Benchmarks

About one-half of the compounds detected in source

water have a human-health benchmark to which concen

trations in samples can be compared. Concentrations of

compounds in source water were compared to human-health

benchmarks, as part of a screening level assessment; however,

MCLs are not directly applicable to source-water samples.

Five compounds (1,2-dibromoethane, dieldrin, acrylonitrile,

PCE, and TCE) were detected in source water at concentra

tions greater than their applicable human-health benchmark

(BQ values greater than 1; Appendix 1). BQ values for all

other detected compounds were one or more orders of magni

tude less than 1, and 84 percent of the concentrations had BQ

values that were two or more orders of magnitude less than 1.

Seven of the 12 commonly detected compounds have

MCLs and two have HBSLs to which concentrations in

samples were compared. Of these commonly detected

compounds, only PCE and TCE were detected in samples at

concentrations greater than the human-health benchmark (one

sample for PCE and two samples for TCE; fig. 7). Although

PCE and TCE were detected in more than 10 percent of the

samples, few of the measured concentrations were within an

order of magnitude of the MCL (BQ values greater than 0.1;

fig. 7).

Concentrations of those compounds commonly detected

that have human-health benchmarks generally are not high

enough to be of human-health concern as individual contami

nants. All chloroform concentrations and all summed triha

lomethane (THM) concentrations were less than the 80 μg/L

MCL for the sum of chloroform, bromodichloromethane,

dibromochloromethane, and bromoform. All herbicide concen

trations were less than their applicable human-health bench

mark; only one atrazine concentration was within an order of

magnitude of the MCL (fig. 7). The commonly detected herbi

cide degradates deethylatrazine and deisopropylatrazine do not

have human-health benchmarks. The summed concentrations

of atrazine and its chlorinated degradates were less than the

MCL of 3 μg/L in all samples.

The gasoline oxygenate MTBE does not have a humanhealth benchmark; however, the USEPA Office of Water

placed MTBE on the Contaminant Candidate List for further

evaluation to determine whether a drinking-water standard

should be established (U.S. Environmental Protection Agency,

2007b). MTBE is included in the Unregulated Contaminant

Monitoring Program (U.S. Environmental Protection Agency,

2007a), which requires large public water systems and a selec

tion of small and medium public water systems to monitor

for selected compounds in their water supplies. The greatest

measured concentration of MTBE (1.88 μg/L) was consider

ably less than the lower control level of 20 μg/L recommended by USEPA in 1997 to prevent taste and odor effects (U.S.

Environmental Protection Agency, 1997).

Concentrations of compounds that were not detected

commonly also were less than applicable human-health bench

marks in most samples (Appendix 1). Three compounds—

1,2-dibromoethane, dieldrin, and acrylonitrile—were each

detected once at concentrations greater than their humanhealth benchmark (BQ values greater than 1). The MCL for

1,2-dibromoethane is 0.05 μg/L, and the reported concentra

tion was 0.072 μg/L. Dieldrin and acrylonitrile both have

HBSLs with relatively low concentrations of 0.002 μg/L and

0.06 μg/L, respectively, and had reported concentrations of

0.024 μg/L and 0.504 μg/L, respectively (Appendix 1). Five

compounds—benzene, alachlor, vinyl chloride, 1,1-dichloro

ethene, and carbon tetrachloride—were each detected once at

concentrations within an order of magnitude of their humanhealth benchmark (BQ values greater than 0.1).



# Mixtures of Compounds

Mixtures can occur in groundwater because of the persis

tence of compounds, presence of parent compounds and their

degradates, co-occurrence of compounds in the source material

such as gasoline, and widespread use and overlapping sources

of compounds (Squillace and others, 2002). The potential

human-health effects of mixtures of organic compounds are

largely unknown and have not been extensively studied. The

effect of one compound on another’s toxicity may be additive,

antagonistic (one compound may lessen the effect of another),

or synergistic; 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 the USEPA, the Agency for Toxic Substances and

Disease Registry (2004), and other agencies.

Although concentrations at which most compounds

were detected were relatively low (less than 1 μg/L) and

concentrations greater than the human-health benchmark

were uncommon, 55 percent of the source-water samples

contained mixtures of two or more compounds (fig. 8). The

most common mixtures included those compounds detected

most commonly, such as chloroform, MTBE, herbicides and

herbicide degradates, and solvents.

Mixtures occurred more commonly, and with greater

numbers of compounds, in samples from shallow wells than in

# Figure 7. Concentrations of commonly detected compounds were A , generally less than 1 microgram per liter; and

B , generally much less than one-tenth of human-health benchmarks for samples collected October 2002–July 2005. **BQ = 0.1 BQ = 1**  0.001 0.01 0.1 1 10 100 1,000



# CONCENTRATION, IN MICROGRAMS PER LITER **Methyl tert**  **-butyl ether** Chloroform

**Metolachlor**

**Prometon Deisopropylatrazine**  Simazine Atrazine **Deethylatrazine**

cis-1,2-Dichloroethene

1,1,1-Trichloroethane Trichloroethene Perchloroethene 

# A

0.0001 0.001 0.01 0.1 1 10 100



# BENCHMARK QUOTIENT (BQ) VALUE 0.000001 0.00001 

# B

Chloroform

**Metolachlor**

**Prometon** Simazine Atrazine

cis

-1,2-Dichloroethene 1,1,1-Trichloroethane Trichloroethene Perchloroethene D i s i n f e c t i o n b y

- p r o d u c t

G a s o l i n e o x y g e n a t e

H e r b i c i d e s a n d h e r b i c i d e d e g r a d a t e s

S o l v e n t s

D i s i n f e c t i o n

b y

- p r o d u c t

H e r b i c i d e s

S o l v e n t s

**EXPLANATION**

**B old type**  indicates an unregulated compound and underlined type indicates the

unregulated compound does not have a Health-Based Screening Level

Note: Disinfection by-products are compared to the Maximum Contaminant Level of

80 micrograms per liter for the sum of four trihalomethanes. Maximum Contaminant Level (MCL) Health-Based Screening Level (HBSL) **Human-health benchmark** 

# 20 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# NUMBER OF COMPOUNDS DETECTED IN SAMPLE 0 20 40 60 80 100



# 38 to 213 feet (53 wells)

215 to 401 feet (55 wells)

403 to 748 feet (53 wells)

750 to 2,070 feet (55 wells)

0 4 8 12 16 20 24 28 32 36PERCENTAGE OF SAMPLES WITH EQUAL OR GREATER NUMBER OF DETECTED COMPOUNDS



# WELL DEPTH QUARTILE



# Figure 8. The number of anthropogenic organic compounds detected as mixtures in source-water samples collected

during October 2002–July 2005 generally was greater in source water from shallow wells than from deep wells. 

# Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 **21**

samples from deep wells (fig. 8). Wells were divided into four

groups using well depth quartiles. Two or more compounds

were detected in 74 and 73 percent of the samples from the

two shallowest groups of wells (38–213 ft and 215–401 ft,

respectively; fig. 8). Two or more compounds were detected in

47 and 27 percent of the samples from wells in the two deepest

groups (403–748 ft and 750–2,070 ft, respectively). For the

well groups with depths less than about 750 ft, a similar

percentage of wells (4–9 percent) had 11 or more compounds

detected in a sample (fig. 8). The maximum number of

compounds in a sample from the deepest wells (750 ft and

greater) was nine (fig. 8).

The common co-occurrence of organic compounds in

source waters as mixtures indicates a need to better under

stand which specific combinations of compounds occur most

commonly and which mixtures 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

Many different factors may affect the occurrence of the

anthropogenic organic compounds monitored in this study.

Some of the most important factors likely related to sourcewater quality include the use of a compound in the contribut

ing area of the well, pumping capacity of the well, recharge,

average groundwater residence time, and aquifer geochem

istry. A detailed evaluation of these factors was beyond the

scope of this study. A general characterization of the occur

rence of commonly detected compounds with respect to

factors such as well depth and aquifer lithology helps to put

the results into context and explain some of the differences in

the occurrence of compounds among sites.

The occurrence of the 12 most commonly detected

compounds was associated with well depth (Kruskal-Wallis

rank-sum test p-value < 0.0001; fig. 9). One or more of

the 12 most commonly detected compounds were found

in 77 percent of samples from the shallowest well group

(38–213 ft), and the occurrence decreased to 29 percent of

samples from the deepest well group (750–2,070 ft; fig. 9 A ).

Similarly, the number of compounds in a sample generally

decreased as well depth increased (fig. 9 B ). No compoundsNUMBER OF THE MOST COMMONLY DETECTED COMPOUNDSDETECTED PER SAMPLE 

# 5 3 5 5 5 5 5 3 

# B

Interquartile

range 0 2 5 5 0 7 5 1 0 0PERCENTAGE OF SAMPLES IN WHICH ONE OR MORE OF THE MOSTCOMMONLY DETECTED COMPOUNDS WERE DETECTED



# 38

– 213 215

– 401 403

– 748 750

– 2,070



# WELL DEPTH QUARTILE, IN FEET 5 3 5 5 5 5 5 3 

# A

**EXPLANATION**

Number of values

75th percentile

Median

25th percentile Outlier data value more

than 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 55

38

– 213 215

– 401 403

– 748 750

– 2,070



# WELL DEPTH QUARTILE, IN FEET 0 2 4 6 8 10 12 14



# Figure 9. The 12 most commonly detected compounds had A , greater detection frequencies; and B , greater numbers of compounds

detected in source-water samples from shallower wells than from deeper wells during October 2002–July 2005. 

# 22 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

# Unconsolidated

glacial

deposits Unconsolidated

and

semiconsolidated

sediments Sandstone

and

carbonate

rocks Igneous

and

metamorphic

rocks



# LITHOLOG Y , IN ORDER OF INCREASING MEDIAN WELL DEPTH 44 28 72 77NUMBER OF THE MOST COMMONLY DETECTED COMPOUNDS DETECTED PER SAMPLE



# 0 2 4 6 8 10 12 14 

# EXPLANATION

Number of values

75th percentile

Median

25th percentile Outlier data value more

than 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 28

Interquartile

range



# Figure 10. Large differences in occurrence of the 12 most commonly detected compounds were not attributable to aquifer lithology

although fewer compounds generally were detected in source-water samples from wells completed in sandstone and carbonate rocks

than from wells completed in other lithology groups. Most samples collected during October 2002–July 2005 contained fewer t han three

compounds for each of the four lithology groups. 

# Anthropogenic Organic Compounds in Source Water Used by Community Water Systems, 2002–05 **23**

were detected in samples from one-half of the wells in

the deepest well group. The more common occurrence of

compounds in samples from shallow wells than deep wells

likely is a result of shorter average groundwater residence

times in shallow wells.

Large differences in the occurrence of the 12 most

commonly detected compounds generally were not attributable

to aquifer lithology. Wells were divided into four lithology

groups. Most samples from all four lithology groups contained fewer than three of the most commonly detected compounds

(fig. 10). The number of compounds detected was significantly

different between the sandstone and carbonate rocks group

and the other three lithology groups (Kruskal-Wallis rank-sum

test p-value = 0.02), and one-half of the samples from the

sandstone and carbonate rocks group did not have a detection

of any commonly detected compound. Wells in this lithology

group, however, include some of the deepest wells that were

sampled; one-half of the sampled wells are deeper than 548 ft

# 24 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

and the deepest well is 1,800 ft (fig. 2 A ). Samples from wells

completed in unconsolidated glacial deposits generally had

the largest number of detections (fig. 10), but these wells were

among the shallowest sampled (median well depth of 124 ft).



# Comparisons of Selected Organic

**Compounds in Source Water and**

**Finished Water Sampled in 2004**

**and 2005**

In addition to characterizing the occurrence of these

compounds in source water, a 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).

During June 2004–September 2005, samples of source water

and finished water were collected from 94 wells. Sampling

of most (79) of these wells during this timeframe generally

focused on analytical suites that included compounds found

to occur most commonly or at relatively high concentrations

during the initial source-water sampling from October 2002

to July 2005. The remaining 15 sites were those in the Rio

Grande aquifer system, where source-water samples were only

collected one time, and all samples (both source and finished)

were analyzed for all 258 compounds plus the additional

3 herbicides and 16 herbicide degradates. The source-water

results for wells in the Rio Grande aquifer system were

included in the source-water characterization presented previ

ously for 2002–05 and are included in this section along with

the associated finished-water results. In general, the number

of compounds analyzed in most source- and finished-water

samples was less than the 258 compounds that were analyzed

in all source-water samples during 2002–05. As a result of

the more targeted sampling, the detection frequencies of

compounds in source water would be expected to be greater

than during the previous sampling. Finished-water samples

were analyzed for the same compounds that were analyzed for

in the associated source-water samples.

Finished-water samples were collected following all

water-treatment processes and before the water entered the

distribution system at each CWS. Finished-water samples

from 34 CWS wells were not blended with water from other

wells prior to distribution; however, 60 finished-water samples

represented water blended with water from one or more wells

at the CWS. In either case, only one well was sampled for

source-water characterization. Differences in occurrence and

concentrations of compounds between source and finished

water might be expected for blended finished-water samples

because of dilution or addition of compounds from wells not

monitored. Other possible factors, in addition to blending,

that could cause differences in occurrence between sourceand finished-water samples include inadequate time allowed

between collecting source- and finished-water samples, the inadvertent addition of compounds in finished water from

pipes and other plumbing, treatment-plant maintenance, vola

tilization, or potential analytical variability associated with

low concentrations at or near LRLs.

The comparison of source- and finished-water samples in

this report is not intended as an evaluation of water-treatment

efficacy at CWSs, which would require precise timing of

sampling at different stages of water treatment; rather, the

results represent an initial assessment of whether compounds

present in source water also are present in finished water. The

CWSs sampled generally are typical of many systems across

the Nation where chlorine disinfection is the primary watertreatment process used. It is important to note that, in general,

disinfection is not designed to remove the organic compounds

detected in this study. However, when source water is known

to contain regulated compounds at concentrations near or

greater than an MCL, CWSs may blend with cleaner water

sources or use additional water treatment, such as granular

activated carbon or air-stripping towers, to remove organic

compounds.

The formation of disinfection by-products as a result

of the disinfection of drinking water is well documented

(Rook, 1974). Disinfection by-products include, for example,

the THMs chloroform, bromodichloromethane, dibromochloromethane, and bromoform. Other common disinfection

by-products include chlorate, chloral hydrate, haloacetic

acids, and haloacetonitriles; however, these other disinfec

tion by-products were not monitored in this study. Disinfec

tion by-products form when organic matter in source water

reacts with the added disinfectant used to protect the drinking

supply against water-borne pathogens such as Escherichia coli

and Norovirus . Consequently, concentrations of THMs are

expected to be greater in finished water than in source water.

Finished-water samples were “quenched” with ascorbic

acid at the time of sample collection to scavenge the free

chlorine that might react with any compounds present in the

sample. Therefore, finished-water data are not necessarily

representative of drinking-water quality at the tap (or point of

delivery) because additional contact time with free chlorine

in the distribution system may change concentrations of some

of the constituents detected in the finished water at the sample

collection point.



# Commonly Detected Compounds

When all compounds from the 2004–05 sampling of

source water and finished water are considered, 99 compounds

were detected. Of these 99 compounds, 84 compounds were

detected in source water and 75 compounds were detected

in finished water; however, 33 and 24 of those compounds,

respectively, were detected only once. Thirty-one compounds

were detected commonly (defined as detected in 10 percent

or more of samples) in either source- or finished-water

samples (table 5). The majority of these compounds were

in the herbicide and herbicide degradates and solvents use

# Table 5. Detection frequency of compounds detected in 10 percent or more of source- and (or) finished-water samples collected

during June 2004–September 2005.

[ Bold type indicates compounds that were detected commonly in samples collected during October 2002–July 2005. ND, not detected]



# Compound (number of source-water samples/number of

**finished-water samples) Detection frequency (percent)** 

**Source water Finished water** 

Disinfection by-products

Bromodichloromethane (71/71) 13 79

Bromoform (71/71) 7.0 62

Chloroform (56/56) 57 88

Dibromochloromethane (71/71) 7.0 72

Fumigant-related compound

1,4-Dichlorobenzene (71/71) 11 11

Gasoline hydrocarbons, oxygenates, and oxygenate degradates

m - and p -Xylene (64/64) ND 14

Methyl tert -butyl ether (71/71) 16 16

Herbicides and herbicide degradates

2-Hydroxyatrazine (61/59) 28 29

Acetochlor ethane sulfonic acid (32/32) 19 19

Acetochlor oxanilic acid (32/32) 9.4 19

Acetochlor/metolachlor ethane sulfonic acid 2nd amide (32/32) 3.1 13

Alachlor ethane sulfonic acid (17/17) 77 77

Alachlor ethane sulfonic acid 2nd amide (32/32) 13 13

Alachlor oxanilic acid (32/32) 25 28

Atrazine (66/66) 59 55

Bentazon (61/59) 13 6.8

Deethylatrazine (66/66) 56 53

Deisopropylatrazine (61/59) 31 20

Metolachlor (64/65) 13 11

Metolachlor ethane sulfonic acid (32/32) 47 41

Metolachlor oxanilic acid (32/32) 38 34

Metsulfuron methyl (61/59) ND 12

Prometon (61/62) 25 19

Simazine (48/48) 46 46

Manufacturing additive

Triphenyl phosphate (53/55) 1.9 20

Solvents

1,1,1-Trichloroethane (71/71) 20 14

1,1-Dichloroethane (71/71) 13 8.5

1,1-Dichloroethene (71/71) 11 8.5

cis- 1,2-Dichloroethene (71/71) 20 18

Perchloroethene (71/71) 39 37

Trichloroethene (71/71) 27 23 

# Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 **25**

# 26 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

groups. Detection frequencies of all compounds detected in

source or finished water are summarized in Appendix 3. The

characterization of results in this section of the report focuses

on the 31 commonly detected compounds because relatively

little information can be inferred from compounds that were

detected in only a few samples.

In general, the 12 compounds that were detected

commonly in source water during the October 2002–July 2005

sampling also were detected commonly in source water during

the June 2004–September 2005 sampling and at greater detec

tion frequencies (table 5; Appendix 1). Nineteen additional

compounds were detected in more than 10 percent of either

source- or finished-water samples (table 5). This, however, is

to be expected based on the well selection strategy followed

for the 2004–05 source- and finished-water sampling for

this study, which focused on wells that had samples with

compounds detected commonly or at large concentrations

during the initial (2002–05) source-water sampling. Two

compounds, m - and p -xylene and metsulfuron methyl, were

detected only in finished water. However, detection of m - and

p -xylene and metsulfuron methyl was primarily in blended

finished-water samples (6 of 9 samples and 6 of 7 samples,

respectively). The occurrence of these compounds primarily

in blended finished-water samples may be the result of their

presence in water from wells that were not sampled as part of

this study.

With the exception of the disinfection by-products,

detection frequencies of most (17) of the commonly detected

compounds were similar (difference of 5 percent or less)

between source water and finished water (table 5), even

though 60 of the 94 finished-water samples were from CWSs

that blend water. For the eight compounds with detection

frequencies in finished water that differed by 6 percent or

more from detection frequencies in source water, about twothirds of the sites were CWSs with blended finished water.

The detection frequencies for bentazon differed by 6 percent

between source and finished water; however, all of these

finished-water samples were nonblended. The four THMs

were detected in source water, but detection frequencies were

much greater in finished water. Chloroform was the most

commonly detected disinfection by-product in finished water

(88 percent), followed by bromodichloromethane (79 percent),

dibromochloromethane (72 percent), and bromoform

(62 percent; table 5).



# Comparison to Human-Health Benchmarks

Concentrations of all compounds commonly detected

in finished water were less than their human-health bench

marks. More than one-half of the commonly detected

compounds have a human-health benchmark to which

concentrations were compared; 13 compounds have an

MCL and 5 compounds have an HBSL (fig. 11). Eight of the

commonly detected compounds (1,4-dichlorobenzene, m - and

p -xylene, 2-hydroxyatrazine, bentazon, metolachlor, metsul

furon methyl, prometon, and 1,1,1-TCA) had finished-water concentrations that were two to six orders of magnitude

less than the human-heath benchmarks. Concentrations of

compounds detected in fewer than 10 percent of finished-water

samples were more than an order of magnitude less than their

applicable benchmarks (BQ values of 0.1 or less; Appendix 1).

Concentrations of disinfection by-products were expected

to increase in finished water relative to source water because

of disinfection. The MCL for total THMs is 80 μg/L, and

summed concentrations were less than this benchmark in

finished water from all wells sampled (fig. 11; Appendix 1).

The concentrations of total THMs were within an order of

magnitude (BQ values greater than 0.1) of the MCL in finished

water from nine sites, but only three detections of chloro

form and one detection of bromoform were within an order

of magnitude of the MCL (fig. 11; Appendix 3). The solvents

PCE (two detections) and TCE (one detection) were the only

other compounds detected in finished water at concentrations

within an order of magnitude of the MCL.



# Comparison of Source- and Finished-Water

**Quality**

Finished water from 60 of the source-water sites included

in this study consisted of a blend of water from the sampled

source-water well and from one or more additional wells

located in the well field. The blending of water from addi

tional wells complicates the comparison of occurrence of

compounds between source water and the associated finished

water. Source and blended finished water are compared using

no assessment level to generally characterize how occurrence

in samples from CWSs that blend water may differ from

systems that do not blend water. The comparisons of occur

rence between source and finished water are not intended to

be an evaluation of water-treatment efficacy at CWSs. Rather,

the results characterize the extent to which compounds present

in source water also are present in finished water. Disinfection

by-products are not included in the following sections compar

ing source- and finished-water quality; however, they are

included in the discussion of mixtures.



# Nonblended Finished Water

Sixty-six compounds were detected in source- and (or)

finished-water samples from the 34 sites where finished

water was not blended with other source water. Of these

66 compounds, 51 were detected in at least one source-water

sample and 49 were detected in at least one finished-water

sample. Some compounds were detected only one time;

15 compounds were detected one time in source water only

and 12 compounds were detected one time in finished water

only. Relatively little information can be inferred from

compounds that were detected only once in either source or

finished water.

More than one-half (57 percent) of the detections

were in both source and finished water, and the concentra

tions were similar (fig. 12). The difference in concentrations

# Note: Disinfection by-products are compared to the Maximum Contaminant Level (MCL)

of 80 micrograms per liter for the sum of four trihalomethanes, and xylene isomers are

compared to the MCL of 10,000 micrograms per liter for total xylenes. Herbicides and

herbicide degradates

Solvents Disinfection by-products

Fumigant-related compound

Gasoline compound

Trichloroethene Perchloroethene cis-1,2-Dichloroethene 1,1-Dichloroethene 1,1,1-Trichloroethane Simazine **Prometon Metsulfuron methyl**  **Metolachlor**

**Bentazon** Atrazine **2-Hydroxyatrazine**

m - and p -Xylene 1,4-Dichlorobenzene Dibromochloromethane Chloroform Bromoform Bromodichloromethane

0.0001 0.001 0.1 10 100



# BENCHMARK QUOTIENT (BQ) VALUE

**EXPLANATION** 0.00001 0.000001 0.01 1



# Bold type indicates an unregulated compound **BQ = 0.1 BQ = 1** 



# Figure 11. Concentrations of commonly detected anthropogenic organic compounds were less

than human-health benchmarks in finished-water samples collected during June 2004–September

2005. 

# Comparisons of Selected Organic Compounds in Source Water and Finished Water Sampled in 2004 and 2005 **27**

generally was less than 50 percent with a median difference of

13 percent. Most of the detections in both source and finished

water were for gasoline-related compounds (gasoline hydro

carbons, oxygenates, and oxygenate degradates), herbicides

and herbicide degradates, and solvents (fig. 12).

In some cases where compounds were present in both

source and finished water, concentrations were much lower

(percentage difference greater than 100) in finished water

than in source water (fig. 12). For example, three solvents—

1,1,1-TCA, PCE, and TCE, which were detected in source

water at concentrations greater than 3 μg/L—had concentra

tions less than 1 μg/L in finished water (fig. 12). This decrease

in concentration between source and finished water likely is

attributable to additional water-treatment steps, such as granu

lar activated carbon and (or) air-stripping towers, used by a

CWS to treat water known to contain elevated concentrations of organic compounds. Other detections of these compounds

in source water at concentrations less than 1 μg/L typically

had a similar concentration in finished water.

Twenty-seven percent of the detections of compounds

in source water did not have a corresponding detection in

finished water (fig. 12). The majority of compounds were

detected at concentrations less than 1 μg/L, and many were

detected at concentrations near or less than the LRL and were

estimated concentrations. Several possibilities, such as trans

formation or removal during water treatment, particularly if

additional treatment steps are used to treat the water because

of known contamination, volatilization, accidental introduc

tion at the wellhead from plumbing or fixtures, or analytical

variability at concentrations near or less than the LRL, may

account for the detection of a compound in source water only.

Disinfection of source water may reduce concentrations of

# 0.001 0.01 0.1 1 10 100 1,000 10,000



# SOURCE-WATER CONCENTRATION, IN MICROGRAMS PER LITERFINISHED-WATER CONCENTRATION, IN MICROGRAMS PER LITER



# 0.001 0.01 0.1

1 10 100 1,000 10,000



# Fumigant-related compounds

Fungicides and fungicide degradates

Gasoline hydrocarbons, oxygenates,

and oxygenate degradates

Herbicides and herbicide degradates

Insecticides and insecticide degradates

Manufacturing additives

Organic synthesis compounds

Pavement- and combustion-derived

compounds

Personal-care and domestic-use products

Refrigerants and propellants

Solvents **EXPLANATION**

Acetone Tetrahydrofuran Methyl ethyl ketone 

# Nondetections set to 0.001

Perchloroethene 1,1,1-Trichloroethane Trichloroethene Methyl isobutyl ketone

m - and p -Xylene

o -Xylene **Primary use or source group**

1:1



# Figure 12. Concentrations of anthropogenic organic compounds (excluding disinfection by-products) in source and associated

nonblended finished water generally were similar when detected in both source and finished water for samples collected during

June 2004–September 2005. 

# 28 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

some compounds through degradation or transformation. For

example, degradation of organophosphate pesticides as a result

of chlorination has been documented (Aizawa and others,

1994). Although finished-water samples were quenched to

inhibit the effect of free chlorine on the compounds monitored

by SWQAs, some reactions may occur quickly within the

water-treatment system, before the finished-water sample was

collected. For those compounds monitored by SWQAs, Valder

and others (2008) documented the degradation of several

compounds as a result of chlorination of source water. In addi

tion, some compounds, particularly solvents and other VOCs,

may be volatilized at the CWS during the treatment process,

especially if water treatment includes aeration.

Occurrence in source water and not in finished water

may not necessarily reflect a change as a result of water

treatment but may result from maintenance at the wellhead.

For example, acetone, methyl ethyl ketone, and tetrahy

drofuran were detected in source water at concentrations

greater than 50 μg/L but not in the associated finished-water sample (fig. 12; Appendix 3). These three compounds were

not detected in source water from the same well in the initial

sample collected during October 2002–July 2005. In samples

from another well, tetrahydrofuran and methyl ethyl ketone

were detected in the intial source water sample at concen

trations greater than 300 μg/L, but only tetrahydrofurn was

detected in the second sample at a concentration of 1.1 μg/L.

The presence of these compounds at high concentrations in

only one source-water sample may be the result of mainte

nance at the sampling point at the well; however, this possible

source was not confirmed.

Less than one-quarter (16 percent) of the detections in

finished water (excluding disinfection by-products) did not

have a corresponding detection in source water (fig. 12).

Concentrations generally were low (near the LRL); however,

concentrations of methyl isobutyl ketone, m- and p- xylene,

and o -xylene were greater than 1 μg/L in one sample. Deter

mining the possible sources of the compounds that were

detected only in finished water was beyond the scope of this

# Fumigant-related compounds

Fungicides and fungicide degradates

Gasoline hydrocarbons, oxygenates,

and oxygenate degradates

Herbicides and herbicide degradates

Insecticides and insecticide degradates

Manufacturing additives

Organic synthesis compounds

Pavement- and combustion-derived

compounds

Personal-care and domestic-use products

Refrigerants and propellants

Solvents Plant- or animal-derived biochemicals **EXPLANATION**

Trichloroethene

SOURCE-WATER CONCENTRATION, IN MICROGRAMS PER LITERFINISHED-WATER CONCENTRATION, IN MICROGRAMS PER LITER



# 0.001 0.01 0.1

1 10 100 1,000 10,000

0.001 0.01 0.1 1 10 100 1,000 10,000 

# Primary use or source group 

# Nondetections set to 0.001

1:1



# 1,1-Dichloroethene 1,1-Dichloroethane and

1,1,1-Trichloroethane Trichloroethene



# Figure 13. Concentrations of anthropogenic organic compounds (excluding disinfection by-products) in source and associated

blended finished water generally were similar when detected in both source and finished water for samples collected during

June 2004–September 2005. 

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

study. However, possible sources of these compounds include

sealants used at pipe connections or minor components of

chemicals used for water treatment. Several herbicides or

herbicide degradates also were detected only in finished water,

and most were detected at concentrations less than 0.1 μg/L.

Given the low concentrations of these detections and the

unlikely event that herbicides would be introduced to the

finished water, analytical variability of concentrations near the

LRL is a possible explanation for these unmatched detections.



# Blended Finished Water

Water from 60 of the 94 source-water wells was blended

with water from other wells before distribution. Although

the comparison between source and blended finished water

is complicated by the addition of water that has not been

monitored, the occurrence of compounds for CWSs that

blended water (fig. 13) generally was similar to the occurrence

of compounds for CWSs that did not blend water (fig. 12) in that one-half of all detections of compounds were in both

source and finished water. Compounds from the herbicides

and herbicide degradates and the solvents use groups were

detected most commonly when a compound was detected in

both source and finished water (fig. 13).

The variability in concentrations between source water

and the associated finished water (scatter around the 1:1 line)

generally was greater for blended than for nonblended

finished water (figs. 12, 13). For the CWSs that blended water,

deviation from the 1:1 line for detections in both source and

finished water (fig. 13) may largely be due to blending or to

some extent the result of water treatment, particularly where

additional treatment steps are used to reduce concentrations of

known contaminants. Determining the cause for these changes

was beyond the scope of this study.

One-half of the detections of compounds were either

in source or finished water only. Blending could account for

many of these unmatched detections especially at low concen

trations (less than 0.1 μg/L), but other factors, such as main

tenance and chemical use at the CWS, also could account for

# 30 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

unmatched detections. Some solvents (1,1,1-TCA, 1,1-dichlo

roethane, 1,1-dichloroethene, and TCE) detected at concentra

tions greater than 5 μg/L in source water from one well were

not detected in the finished-water sample (fig. 13). The CWS

where this sample was collected treats the drinking water with

granular activated carbon to reduce concentrations of contami

nants known to be present in the source water (Jim Stark,

U.S. Geological Survey, written commun., 2008). These large

decreases in concentration likely are predominantly the result

of the additional water-treatment processes used at this CWS;

however, in some cases blending may contribute to reducing

concentrations.

The frequent occurrence of several compounds in both

source water and the associated blended finished water further

demonstrates the importance of source-water characterization

and wellhead protection. About one-half of the detections of

compounds in source water had corresponding detections in

the associated finished water and generally were similar to

results for nonblended water. Finished water from more than

one-half of the CWSs in the study was blended; however,

blending did not always reduce concentrations to less than the

LRL. These findings indicate that the protection of sourcewater quality may be the most effective mechanism to ensure

high-quality drinking water. That is, preventing or minimizing

the possibility of occurrence of contaminants may be prefer

able to treating the water after source-water contamination has

occurred.



# Mixtures

One objective of the comparison between source and

finished water was to evaluate potential differences in

the frequency of occurrence and complexity of mixtures

of organic compounds. The characterization of mixtures

presented in this section includes disinfection by-products in

both nonblended and blended finished water. About 70 and

82 percent of source- and finished-water samples, respectively,

contained mixtures of two or more compounds (fig. 14). About

one-half of the source-water samples contained mixtures of

five or more compounds (median = 12), and about one-half of

the finished-water samples contained mixtures of six or more

compounds (median = 13). Mixtures occur more commonly

in finished water than in source water partly because of the

formation of disinfection by-products in finished water, which

increases the number of compounds detected in finished

water relative to source water (fig. 14). The percentages

of mixtures of organic compounds were greater in sourcewater samples collected during the second phase of sampling

(June 2004–September 2005) than during the initial phase of

sampling (October 2002–July 2005), because sampling during

the second phase focused on wells where compounds were

detected most commonly or at relatively higher concentra

tions during the initial phase. However, the characterization of

mixtures in source and finished water represents a minimum

number of compounds in a sample because most samples were not analyzed for all of the analytical suites used in the initial

sampling. In particular, not all samples were analyzed for the

suite of compounds that included the disinfection by-products.

As described previously in relation to mixture occurrence

in source water, the potential human-health significance of

the common occurrence of mixtures of organic compounds

remains largely unknown. The common occurrence of

mixtures in both source- and finished-water samples points to

a need for identifying the specific combinations of compounds

that occur most commonly and identifying the compounds that

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.



# Summary

During October 2002 to July 2005, source-water samples

were collected from 221 wells completed in 12 principal

aquifers in the United States as part of the Source WaterQuality Assessment (SWQA) component of the U.S. Geologi

cal Survey’s National Water-Quality Assessment (NAWQA)

Program. Each community water system (CWS) well was

sampled once for analysis of 258 anthropogenic organic

compounds to characterize the quality of the source water.

Most of these compounds are unregulated in drinking water

and include pesticides and pesticide degradates, gasoline

hydrocarbons, personal-care and domestic-use products, and

solvents. Source- and finished-water (after treatment and

before distribution) samples were collected during June 2004

to September 2005 from selected sites to characterize the

extent to which compounds detected in the source water were

present in the finished water.

The CWSs that participated in SWQAs ranged in size

from single-well systems to systems with multiple wells. In

many cases where CWSs have multiple wells, the CWSs blend

water before or after water treatment. The water-treatment

process predominantly used by the CWSs was disinfection

with chlorine. Additional water-treatment steps were used by

CWSs when source water was known to be contaminated with

organic compounds. These additional water-treatment steps

included granular activated carbon and air-stripping towers.

Of the 258 compounds analyzed in samples from all

221 wells, 120 compounds were detected in at least one

source-water sample. However, 52 compounds were detected

only once, and many were detected infrequently and at

concentrations less than 0.1 microgram per liter (μg/L). The

laboratory analytical methods used in this study have detection

levels that are commonly 100 to 1,000 times lower than State

and Federal standards and guidelines for protecting water

quality. Detections of these compounds do not necessarily

indicate a concern to human health but rather help to identify

# 0 4 8 12 16 20 24 28 0 20 40 60 80 100

NUMBER OF COMPOUNDS DETECTED IN SAMPLE F i nished water Source waterPERCENTAGE OF SAMPLES WITH EQUAL OR GREATER NUMBER OF DETECTED COMPOUNDS



# Figure 14. Both source- and finished-water samples collected during the June 2004–September 2005 sampling

typically contained mixtures of two or more compounds. 

# Summary **31**

emerging issues and track changes in occurrence and concen

trations over time.

The occurrence of compounds in source water varied

regionally. More compounds and greater total concentra

tions generally were detected in samples from wells east of

the Mississippi River than in samples from wells west of the

Mississippi River. Factors that may account for these differ

ences in occurrence include generally higher groundwater

recharge rates, shallower well depths, shallower depths to

groundwater, greater population densities, and more intense

use of agricultural herbicides east of the Mississippi River

than west of the Mississippi River.

Twelve compounds were detected in about 10 percent or

more of source-water. Chloroform was the most commonly

detected compound in this study and was detected in

36 percent of samples. One-half of the commonly detected

compounds in this study were herbicides and herbicide

degradates (deethylatrazine, atrazine, simazine, prometon,

metolachlor, and deisopropylatrazine) likely because of their

widespread use, the large number of compounds analyzed

in this group, and the low levels at which these compounds

were analyzed. The compounds perchloroethene (PCE), trichloroethene (TCE), 1,1,1-trichloroethane, methyl tert

butyl ether, and cis -1,2-dichloroethene also were detected

commonly. The most commonly detected compounds in

source-water samples generally were among those detected

commonly across the country and reported in previous studies

by the NAWQA Program.

Samples were collected from a subset of 73 wells and

analyzed for an additional 3 herbicides and 16 degradates

in locations where the parent herbicides had potential use.

Degradates of both alachlor and metolachlor were detected

more commonly and at similar or greater concentrations than

concentrations of the parent herbicide. These results highlight

the fact that information about the occurrence and concentra

tions of degradates may be as important as information about

the parent compound for some pesticides, particularly if the

degradate toxicity or mode of action is similar to that of the

parent compound.

Detections of compounds at concentrations greater than

a human-health benchmark were infrequent, and only five

compounds were detected in source water at a concentration

greater than the human-health benchmark. Concentration of

compounds in source water were compared to human-health

# 32 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

benchmarks as part of a screening level assessment; however,

Maximum Contaminant Levels (MCLs) are not directly

applicable to source-water samples. Measured concentra

tions of compounds that are regulated in drinking water were

compared to U.S. Environmental Protection Agency (USEPA)

MCLs, and concentrations of unregulated compounds were

compared to Health-Based Screening Levels developed by

the U.S. Geological Survey in collaboration with USEPA and

others. Concentrations of TCE were greater than the MCL in

two samples, and 1,2-dibromoethane and PCE were detected

in one sample each at a concentration greater than the MCL.

Acrylonitrile and dieldrin were detected at concentrations

greater than their respective Health-Based Screening Levels

in one sample each. All other compounds were detected at

concentrations less than available human-health benchmarks,

and 84 percent of the concentrations were two or more orders

of magnitude less than the benchmark. About one-half of all

detected compounds do not have human-health benchmarks or

adequate toxicity information to evaluate results in a humanhealth context.

About 55 percent of source-water samples contained

mixtures of two or more compounds. The most common

mixtures included those compounds detected most commonly,

such as chloroform, MTBE, herbicides and herbicide degra

dates, and solvents. Mixtures of compounds occurred more

commonly and with greater numbers of compounds in water

from shallow wells than in water from deep wells. Two or

more compounds were detected in 74 and 73 percent of the

samples from the two shallowest groups of wells (38–213 feet

and 215–401 feet, respectively).

The comparison of source- and finished-water quality

in this report represents an initial assessment of whether

compounds present in source water also are present in finished

water. Source-water samples from 94 wells and associ

ated finished-water samples were collected from June 2004

to September 2005. Most of these samples were analyzed

for fewer compounds than during the initial source-water

sampling. Samples were analyzed for those compounds

detected commonly or at relatively high concentrations during

the initial source-water sampling. Finished-water samples

were collected following all of the treatment steps and before

distribution. The assessment of compounds detected in sourceand finished-water samples is not intended as an evaluation of

water-treatment efficacy at CWS. In general, the types of treat

ment used by the CWSs that were sampled were not specifi

cally designed to remove most of the organic compounds

monitored in this study. Finished-water data are not necessar

ily 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 samplecollection point.

Thirty-one compounds were detected commonly (defined

as detected in 10 percent or more of samples) in either sourceor finished-water samples during June 2004–September 2005

and included the 12 compounds detected commonly during the initial sampling from October 2002 to July 2005. The majority

of the compounds were in the herbicide and herbicide degra

dates and solvents use groups. With the exception of the disin

fection by-products, which are expected to form in finished

water, the detection frequencies of most (17) of the commonly

detected compounds were similar (difference of 5 percent or

less) between source and finished water. For those compounds

with detection frequencies that differed by 6 percent or more

between source and finished water, about two-thirds of the

sites were CWSs with blended finished water.

Concentrations of all compounds commonly detected in

finished water were less than their human-health benchmarks,

which are available for about one-half of the compounds

detected in finished-water samples. Eight of the commonly

detected compounds (1,4-dichlorobenzene, m- and p -xylene,

2-hydroxyatrazine, bentazon, metolachlor, metsulfuron

methyl, prometon, and 1,1,1-trichloroethane) had finishedwater concentrations that were two to six orders of magnitude

less than the human-health benchmarks. The summed concen

trations of the trihalomethanes for all of the finished-water

samples were less than the MCL of 80 μg/L. The concentra

tions of total trihalomethanes were within an order of magni

tude of the MCL in finished water from nine sites, but only

three detections of chloroform and one detection of bromo

form were within an order of magnitude of the MCL. Two

detections of PCE and one detection of TCE in finished water

had concentrations within an order of magnitude of the MCL,

and concentrations of all other compounds were more than an

order of magnitude less than the benchmark.

Differences in the occurrence of compounds in source

or finished water could result from water treatment, blending,

volatilization, or analytical variability at concentrations near or

less than the laboratory reporting level. At the 34 sites where

finished water was not blended, about one-half (57 percent)

of the detections were in both source and finished water, and

concentrations were similar. Large changes in concentra

tions from source to finished water in a few samples likely

are attributable to additional water treatment steps used by

the CWS to treat water known to contain elevated concentra

tions of organic compounds. Finished water from 60 of the

source-water wells sampled in the study was a blend of water

from two or more wells. Although the comparison between

source and blended finished water is complicated by the

addition of water that has not been monitored, the occurrence

of compounds for CWSs that blended water generally was

similar to the occurrence of compounds for CWSs that did not

blend water in that one-half of all detections of compounds

were in both source and finished water.

Compounds occur more commonly as mixtures in

finished water than in source water because of the formation of

disinfection by-products in finished water. Mixtures of two or

more compounds were detected in about 70 percent of sourcewater samples and in 82 percent of finished-water samples.

Although concentrations of compounds detected typically

were considerably less than human-health benchmarks, the

frequent occurrence of mixtures in finished waters indicates a

# References **33**

need for identifying mixtures that are most common and most

likely to have potential human-health effects.



# References

Agency for Toxic Substances & Disease Registry, 2004,

Guidance manual for the assessment of joint toxic action of

chemical mixtures, May 2004: Department of Health and

Human Services, accessed March 12, 2008, at http://www.

atsdr.cdc.gov/interactionprofiles/ipga.html.

Aizawa, T., Magara, Y., Takagi, H., and Souna, F., 1994, Chlo

rination by-products of pesticides in drinking water: Water

Supply, v. 12, no. 1–2, p. SS11-6–SS11-9.

Banks, W.S.L., and Reyes, Betzaida, 2009, Anthropogenic

organic compounds in source and finished groundwater of

community water systems in the Piedmont physiographic

province, Potomac River Basin, Maryland and Virginia,

2003–04: U.S. Geological Survey Scientific Investigations

Report 2009–5064, 33 p.

Beek, Bernd, ed., 2001, Biodegradation and persistence, in

Huntizinger, Otto, ed., The handbook of environmental

chemistry, volume 2, reactions and processes, part K:

Berlin, Germany, Springer-Verlag, 327 p.

Carpenter, D.O., Arcaro, K., and Spink, D.C., 2002, Under

standing the human health effects of chemical mixtures:

Environmental Health Perspectives, v. 110, p. 25–42.

Carter, J.M., Delzer, G.C., Kingsbury, J.A., and Hopple,

J.A., 2007, Concentration data for anthropogenic organic

compounds in ground water, surface water, and finished

water of selected community water systems in the United

States, 2002–05: U.S. Geological Survey Data Series 268,

30 p., accessed March 12, 2008, at http://pubs.usgs.gov/

ds/2007/268/

.

Carter, J.M., Grady, S.J., Delzer, G.C., Koch, Bart, and Zogor

ski, J.S., 2006, Occurrence of MTBE and other gasoline

oxygenates in CWS source waters: Journal of the American

Water Works Association, v. 98, no. 4, p. 91–104.

Connor, B.F., Rose, D.L., Noriega, M.C., Murtagh, L.K.,

and Abney, S.R., 1998, Methods of analysis by the U.S.

Geological Survey National Water Quality Laboratory—

Determination of 86 volatile organic compounds in water by

gas chromatography/mass spectrometry, including detec

tions less than reporting limits: U.S. Geological Survey

Open-File Report 97–829, 78 p. Delzer, G.C., and Hamilton, P.A., 2007, National

Water-Quality Assessment Program—Source WaterQuality Assessments: U.S. Geological Survey Fact

Sheet 2007–3069, 2 p.

Furlong, E.T., Anderson, B.D., Werner, S.L., Soliven, P.P.,

Coffey, L.J., and Burkhardt, M.R., 2001, Methods of analy

sis by the U.S. Geological Survey National Water Quality

Laboratory—Determination of pesticides in water by

graphitized carbon-based solid-phase extraction and highperformance liquid chromatography/mass spectrometry:

U.S. Geological Survey Water-Resources Investigations

Report 01–4134, 73 p.

Gilliom, R.J., Barbash, J.E., Crawford, C.G., Hamilton, P.A.,

Martin, J.D., Nakagaki, N., Nowell, L.H., Scott, J.C., Stack

elberg, P.E., Thelin, G.P., and Wolock, D.M., 2006, The

quality of our Nation’s waters—Pesticides in the Nation’s

streams and ground water, 1992–2001: U.S. Geological

Survey Circular 1291, 172 p.

Grady, S.J., 2003, A national survey of methyl tert -butyl ether

and other volatile organic compounds in drinking-water

sources—Results of the random survey: U.S. Geological

Survey Water-Resources Investigations Report 02–4079,

85 p.

Groschen, G.E., Arnold, T.L., Harris, M.A., Dupré, D.H., Fitz

patrick, F.A., Scudder, B.C., Morrow, W.S., Jr., Terrio, P.J.,

Warner, K.L., and Murphy, E.A., 2004, Water quality in the

upper Illinois River Basin, Illinois, Indiana, and Wisconsin,

1999–2001: U.S. Geological Survey Circular 1230, 32 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in

water resources: New York, Elsevier, 522 p.

Ivahnenko, Tamara, and Barbash, J.E., 2004, Chloroform in

the hydrologic system—Sources, transport, fate, occurrence,

and effects on human health and aquatic organisms: U.S.

Geological Survey Scientific Investigations Report 2004–

5137, 34 p.

Ivahnenko, Tamara, and Zogorski, J.S., 2006, Sources and

occurrence of chloroform and other trihalomethanes in

drinking-water supply wells in the United States, 1986–

2001: U.S. Geological Survey Scientific Investigations

Report 2006–5015, 13 p.

Kalkhoff, S.J., Kolpin, D.W., Thurman, E.M., Ferrer, I.,

and Barcelo, D., 1998, Degradation of chloroacetanilide

herbicides—The prevalence of sulfonic and oxanilic acid

metabolites in Iowa groundwaters and surface waters:

Environmental Science and Technology, v. 32, no. 11,

p. 1738–1740.

# 34 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

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.

Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995,

Ground-water data-collection protocols and procedures for

the National Water-Quality Assessment Program—Collec

tion and documentation of water-quality samples and related

data: U.S. Geological Survey Open-File Report 95–399,

113 p. + errata.

Lapham, W.W., Hamilton, P.A., and Myers, D.N., 2005,

National Water-Quality Assessment Program—Cycle II,

Regional assessments of aquifers: U.S. Geological Survey

Fact Sheet 2005–3013, 4 p.

Lee, E.A., and Strahan, A.P., 2003, Methods of analysis by the

U.S. Geological Survey Organic Geochemistry Research

Group—Determination of acetamide herbicides and their

degradation products in water using online solid-phase

extraction and liquid chromatography/mass spectrometry:

U.S. Geological Survey Open-File Report 03–173, 17 p.

Lindley, C.E., Stewart, J.T., and Sandstrom, M.W., 1996,

Determination of low concentrations of acetochlor in water

by automated solid-phase extraction and gas chromatogra

phy with mass-selective detection: Journal of Association

of Official Analytical Chemists International, v. 79, no. 4,

p. 962–966.

Madsen, J.E., Sandstrom, M.W., and Zaugg, S.D., 2003,

Methods of analysis by the U.S. Geological Survey

National Water Quality Laboratory—A method supplement

for the determination of fipronil and degradates in water by

gas chromatography/mass spectrometry: U.S. Geological

Survey Open-File Report 02–462, 11 p.

Maupin, M.A., and Barber, N.L., 2005, Estimated withdraw

als from principal aquifers in the United States, 2000: U.S.

Geological Survey Circular 1279, 46 p.

Metz, P.A., Delzer, G.C., Berndt, M.P., Crandall, C.A., and

Toccalino, P.L., 2006, Anthropogenic organic compounds

in ground water and finished water of community water

systems in the northern Tampa Bay area, Florida,

2002–04: U.S. Geological Survey Scientific Investigations

Report 2006–5267, 48 p.

Pankow, J.F., and Cherry, J.A., 1996, Dense chlorinated

solvents in groundwater: Portland, Oreg., Waterloo Press,

522 p.

Rook, J.J., 1974, Formation of haloforms during chlorina

tion of natural water: Water Treatment Examiner, v. 23,

p. 234–243. Rose, D.L., and Sandstrom, M.W., 2003, Methods of

analysis by the U.S. Geological Survey National Water

Quality Laboratory—Determination of gasoline oxygen

ates, selected degradates, and BTEX in water by heated

purge and trap/gas chromatography/mass spectrometry:

U.S. Geological Survey Water-Resources Investigations

Report 03–4079, 31 p.

Rosen, M.R., Schaefer, D.H., Toccalino, P.L., and Delzer,

G.C., 2006, Occurrence of anthropogenic organic

compounds in ground water and finished water of commu

nity water systems in Eagle and Spanish Springs Valleys,

Nevada, 2002–2004: U.S. Geological Survey Scientific

Investigations Report 2006–5210, 31 p.

Sandstrom, M.W., Stroppel, M.E., Foreman, W.T., and

Schroeder, M.P., 2001, Methods of analysis by the U.S.

Geological Survey National Water Quality Laboratory—

Determination of moderate-use pesticides and selected

degradates in water by C–18 solid-phase extraction and

gas chromatography/mass spectrometry: U.S. Geological

Survey Water-Resources Investigations Report 01–4098,

70 p.

Squillace, P.J., Scott, J.C., Moran, M.J., Nolan, B.T., and

Kol pin, D.W., 2002, VOCs, pesticides, nitrate, and their

mix tures in groundwater used for drinking water in the

United States: Environmental Science and Technology,

v. 36, no. 9, p. 1923–1930.

Thomas, M.A., 2007, Anthropogenic organic compounds

in ground water and finished water of community water

sys tems near Dayton, Ohio, 2002–04: U.S. Geological

Survey Scientific Investigations Report 2007–5035, 21 p.

Thurman, E.M., Goolsby, D.A., Meyer, M.T., Mills, M.S.,

Pomes, M.L., and Kolpin, D.W., 1992, A reconnaissance

study of herbicides and their metabolites in surface water of

the Midwestern United States using immunoassay and gas

chromatography/mass spectrometry: Environmental Science

and Technology, v. 26, no. 12, p. 2440–2447.

Toccalino, P.L., Nowell, L.H., Wilber, W.G., Zogorski, J.S.,

Donohue, J.M., Eiden, C.A., Krietzman, S.J., and Post,

G.B., 2003, Development of Health-Based Screening Levels

for use in State- or local-scale water-quality assessments:

U.S. Geological Survey Water-Resources Investigations

Report 03–4054, 22 p.

Toccalino, P.L., 2007, Development and application of HealthBased Screening Levels for use in water-quality assess

ments: U.S. Geological Survey Scientific Investigations

Report 2007–5106, 12 p. (Also available at http://pubs.usgs.

gov/sir/2007/5106/. )

# References **35**

Toccalino, P.L., Norman, J.E., Booth, N.L., and Zogorski, J.S.,

2006, Health-Based Screening Levels—A tool for evaluat

ing what water-quality data may mean to human health:

U.S. Geological Survey, National Water-Quality Assessment

Program, accessed July 20, 2007, at http://water.usgs.gov/

nawqa/HBSL/

.

Toccalino, P.L., Rowe, B.L., and Norman, J.E., 2006, Volatile

organic compounds in the Nation’s drinking-water supply

wells—What findings may mean to human health: U.S.

Geological Survey Fact Sheet 2006–3043, 4 p. (Also avail

able at http://pubs.usgs.gov/fs/2006/3043/. )

Toccalino, P.L., Norman, J.E., Booth, N.L., and Zogorski, J.S.,

2008, Health-Based Screening Levels—A tool for evaluat

ing what water-quality data may mean to human health:

U.S. Geological Survey, National Water-Quality Assessment

Program, updated April 10, 2008, accessed January 16,

2009, at http://water.usgs.gov/nawqa/HBSL.

Tornes, L.H., Stark, J.R., Hoard, C.J., and Smith, E.A., 2007,

Anthropogenic organic compounds in ground water and

finished water of community water systems in the Greater

Twin Cities metropolitan area, Minnesota and Wisconsin,

2004–05: U.S. Geological Survey Scientific Investigations

Report 2007–5273, 42 p.

Trombley, T.J., Brown, C.J., and Delzer, G.C., 2007, Anthro

pogenic organic compounds in source and finished water

from community water system wells in western and central

Connecticut, 2002–2004: U.S. Geological Survey Scientific

Investigations Report 2007–5171, 38 p.

U.S. Department of Agriculture, 2008, Agricultural Research

Service (ARS), pesticide properties database: U.S. Depart

ment of Agriculture, accessed June 22, 2009, at http://www.

ars.usda.gov/services/docs.htm?docid=14199.

U.S. Environmental Protection Agency, 1997, Drinking water

advisory—Consumer acceptability advice and health effects

analysis on methyl tertiary-butyl ether: Washington, D.C.,

U.S. Environmental Protection Agency, Office of Water,

EPA–822–F–97–009.

U.S. Environmental Protection Agency, 1998, Code of

Federal Regulations, title 40—Protection of environment,

chapter 1—Environmental protection agency, subchapter

E—Pesticide programs, part 159—Statements of policies

and interpretations, subpart D—Reporting requirements

for risk/benefit information, 40 CFR 159.184: National

Archives and Records Administration, September 19, 1997,

amended June 19, 1998, accessed February 9, 2009, at

http://www.gpoaccess.gov/ecfr/index.html. U.S. Environmental Protection Agency, 2002, Occurrence

summary and use support document for the six-year review

of national primary drinking water regulations: Office of

Water, EPA–815–D–02–006, 453 p., accessed October 9,

2007, at http://www.epa.gov/safewater/standard/review/

pdfs/support_6yr_occursummaryuse_draft.pdf.

U.S. Environmental Protection Agency, 2005, Fact sheet—The

Drinking Water Contaminant Candidate List—The source

of priority pollutants for the Drinking Water Program:

Office of Water, EPA 815–F–05–001, 6 p., accessed

March 6, 2009, at http://www.epa.gov/safewater/ccl/pdfs/

fs_ccl2_final-02-23-05.pdf.

U.S. Environmental Protection Agency, 2006, 2006 Edition of

the drinking water standards and health advisories: Wash

ington, D.C., U.S. Environmental Protection Agency, Office

of Water, EPA 822–R–06–013, accessed August 2006,

12 p., http://www.epa.gov/waterscience/criteria/drinking/

dwstandards.pdf.

U.S. Environmental Protection Agency, 2007a, Unregulated

Contaminant Monitoring Program: U.S. Environmental

Protection Agency, accessed April 9, 2008, at http://www.

epa.gov/safewater/ucmr/index.html.

U.S. Environmental Protection Agency, 2007b, MTBE

(methyl-t-butyl ether) in drinking water: U.S. Environmen

tal Protection Agency, Office of Ground Water and Drinking

Water, accessed December 21, 2007, at http://www.epa.gov/

safewater/contaminants/unregulated/mtbe.html.

U.S. Environmental Protection Agency, 2008, Setting stan

dards for safe drinking water: U.S. Environmental Protec

tion Agency, Office of Ground Water and Drinking Water,

accessed December 15, 2008, at http://www.epa.gov/

safewater/standard/setting.html.

U.S. Geological Survey, 2003, Principal aquifers of the

48 conterminous United States, Hawaii, Puerto Rico,

and the U.S. Virgin Islands: U.S. Geological Survey, The

National Atlas metadata, accessed July 12, 2007, at http://

www-atlas.usgs.gov/metadata/aquifrp025.html.

U.S. Geological Survey, 2007, Facing tomorrow’s chal

lenges—U.S. Geological Survey science in the decade

2007–2017: U.S. Geological Survey Circular 1309, 70 p.

# 36 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

Valder, J.F., Delzer, G.C., Price, C.V., and Sandstrom, M.W.,

2008, Study design and percent recoveries of anthropo

genic organic compounds with and without the addition

of ascorbic acid to preserve water samples containing free

chlorine, 2004–06: U.S. Geological Survey Open-File

Report 2008–1226, 85 p. (Available at http://pubs.usgs.gov/

of/2008/1226/. )

Westrick, J.J., Mello, J.W., and Thomas, R.F., 1984, Ground

water supply survey: Journal of American Water Works

Association, v. 76, no. 5, p. 52–59.

Winslow, S.D., Prakash, Brahm, Domino, M.M., and

Pepich, B.V., 2001, Considerations necessary in gathering

occurrence data for selected unstable compounds in the

USEPA unregulated contaminant candidate list in USEPA

method 526: Environmental Science and Technology, v. 35,

no. 9, p. 1851–1858.

Zaugg, S.D., Sandstrom, M.W., Smith, S.G., and Fehlberg,

K.M., 1995, Methods of analysis by the U.S. Geological

Survey National Water Quality Laboratory—Determina

tion of pesticides in water by C–18 solid-phase extraction

and capillary-column gas chromatography/mass spectrom

etry with selected-ion monitoring: U.S. Geological Survey

Open-File Report 95–181, 49 p.

Zaugg, S.D., Smith, S.G., Schroeder, M.P., Barber, L.B., and

Burkhardt, M.R., 2002, Methods of analysis by the U.S.

Geological Survey National Water Quality Laboratory—

Determination of wastewater compounds by polystyrenedivinylbenzene solid-phase extraction and capillary-column

gas chromatography/mass spectrometry: U.S. Geological

Survey Water-Resources Investigations Report 01–4186,

37 p.

Zogorski, J.S., Carter, J.M., Ivahnenko, Tamara, Lapham,

W.W., Moran, M.J., Rowe, B.L., Squillace, P.J., and

Toccalino, P.L., 2006, The quality of our Nation’s waters—

Volatile organic compounds in the Nation’s ground water

and drinking-water supply wells: U.S. Geological Survey

Circular 1292, 101 p.

# Appendixes

# 38 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Disinfection by-productsChloroform67–66–36518036.112.80.0245.48280MCL--Bromodichloromethane75–27–4172217.72.7.028.788280MCL--Bromoform75–25–2102214.53.6.11.9280MCL--Dibromochloromethane124–48–182213.63.6.11.01280MCL--Fumigant-related compounds1,2-Dichloropropane78–87–532211.4ND0.029E0.0925MCL--1,2-Dibromoethane106–93–41221.5ND.036E.072.05MCL1(1)1,2-Dibromo-3-chloro-propane96–12–80221NDND.51ND.2MCL--1,3-Dichloropropane(CCL)142–28–90221NDND.06ND------1,4-Dichlorobenzene3106–46–70221NDND.034ND75MCL--2,2-Dichloropropane(CCL)594–20–70221NDND.05ND------Bromomethane (CCL)74–83–90221NDND.33ND100HBSL--cis-1,3-Dichloropropene(CCL)10061–01–50221NDND.05ND4,5.3HBSL--trans-1,3-Dichloropro-pene (CCL)10061–02–60221NDND.09ND4,5.3HBSL--Fungicides and fungicide degradatesMetalaxyl57837–19–122210.9ND0.0070.035600HBSL--Myclobutanil88671–89–01221.5ND.033.011200HBSL--Propiconazole60207–90–11215.5ND.01E.00570HBSL--Benomyl17804–35–20215NDND.022ND40HBSL--Chlorothalonil1897–45–60215NDND.035ND5HBSL--

# Appendixes **39 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Fungicides and fungicide degradates—ContinuedIprodione36734–19–70221NDND0.026ND40.8HBSL--Pentachlorophenol87–86–50211NDND2ND1MCL--Gasoline hydrocarbons, oxygenates, and oxygenate degradatesMethyltert-butyl ether(MTBE) (CCL)1634–04–42822112.76.80.11.88------1,2,4-Trimethylbenzene(CCL)95–63–641762.3.6.0562.37------Benzene71–43–241922.11.0.021.6315MCL1tert-Amyl methyl ether(TAME)994–05–832211.4.9.04.281------m-andp-Xylene106–42–3;108–38–321611.2.6.063.28610,000MCL--1,2,3,4-Tetramethylbenzene488–23–32221.9.5.14.921------1-Ethyl-2-methylbenzene (o-Ethyltoluene)611–14–32221.9.9.06.666------Isopropylbenzene398–82–82221.9ND.038E.073700HBSL--Ethylbenzene100–41–41176.6.6.03.517700MCL--o-Xylene95–47–61176.6.6.0382.84610,000MCL--1,2,3,5-Tetramethylbenzene527–53–71221.5.5.181.48------1,2,3-Trimethylbenzene526–73–81221.5.5.091.51------1,3,5-Trimethylbenzene108–67–81221.5.5.044.942------1-Methylnaphthalene390–12–01217.5.5.5E.12------

# 40 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued2,6-Dimethylnaphtha-lene581–42–012170.5ND0.5E0.003------2-Methylnaphthalene391–57–61217.5.5.5E.2330HBSL--Diisopropyl ether(DIPE)108–20–31221.5.5.1.159------Naphthalene (CCL)91–20–31221.5.5.52.956100HBSL--n-Butylbenzene104–51–81221.5ND.14E.069------p-Isopropyltoluene(CCL)99–87–61221.5ND.08E.063------sec-Butylbenzene135–98–81221.5ND.06E.065------tert-Amyl alcohol(2-Methyl-2-butanol)75–85–40119NDND1ND------Ethyltert-butyl ether(ETBE)637–92–30221NDND.03ND------Styrene3100–42–50221NDND.042ND100MCL--tert-Butyl alcohol75–65–00119NDND1ND------tert-Butylbenzene98–06–60221NDND.08ND------Toluene108–88–30117NDND.02ND1,000MCL--Herbicides and herbicide degradatesAlachlor ethanesulfonic acid--205834.522.40.020.64------Deethylatrazine (DEA)(CCL)6190–65–47622134.44.1.014.38------Atrazine1912–24–96622129.93.2.007.3353MCL1Metolachlor ethanesulfonic acid--217328.821.9.022.72------

# Appendixes **41 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Herbicides and herbicide degradates—ContinuedSimazine122–34–93722116.70.50.0050.1144MCL--Metolachlor oxanilicacid--117315.19.6.022.96------Deisopropylatrazine(DIA)1007–28–92821513.0.5.08.12------Prometon (CCL)1610–18–02522111.3ND.01.036400HBSL--Metolachlor (CCL)351218–45–22422110.9.9.0063.58700HBSL--2-Hydroxyatrazine2163–68–0202159.3ND.032E.03570HBSL--Alachlor ethanesulfonic acid 2ndamide--4439.3ND.02.05------Alachlor oxanilic acid--4735.52.7.021.23------Bentazon25057–89–082153.7.5.024E.49200HBSL--Diuron (CCL)330–54–172153.3.5.016E.16642HBSL--Bromacil314–40–972163.2.5.018.33870HBSL--3,4-Dichloroaniline95–76–132211.4ND.0045.009------Acetochlor ethanesulfonic acid--1731.4ND.02.07------Acetochlor oxanilicacid--1731.41.4.02.12------Alachlor15972–60–832211.4.5.005.2492MCL1Metsulfuron methyl374223–64–632141.4ND.067E.0352,000HBSL--Dinoseb88–85–72215.9ND.038E.0057MCL--Hexazinone51235–04–21113.9ND.026E.008400HBSL--Imazaquin81335–37–72215.9ND.036E.012,000HBSL--

# 42 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Herbicides and herbicide degradates—ContinuedImazethapyr381335–77–522150.9ND0.038E0.0072,000HBSL--Norflurazon27314–13–22215.9ND.02E.02610HBSL--Picloram1918–02–12215.9ND.032.085500MCL--Sulfometuron-methyl74222–97–22215.9ND.09E.0042,000HBSL--Tebuthiuron34014–18–12218.9ND.026E.031,000HBSL--2,4–D94–75–71215.5ND.038E.00970MCL--Acetochlor (CCL)34256–82–11221.5ND.006.03741HBSL--Clopyralid1702–17–61215.5ND.067E.013------Deethyldeisopropylatrazine (DDA)3397–62–41213.5ND.04E.069------Fluometuron2164–17–21215.5ND.016E.0044HBSL--Metribuzin (CCL)21087–64–91221.5ND.028.0190HBSL--Siduron1982–49–61215.5ND.02E.0121,000HBSL--Terbacil (CCL)5902–51–21215.5ND.026E.0690HBSL--2,4–D methyl ester1928–38–70215NDND.19ND------2,4–DB94–82–60215NDND.02ND200HBSL--2,6-Diethylaniline579–66–80221NDND.006ND------2-Chloro-2,6-diethylacetanilide6967–29–90221NDND.0065ND------2-Ethyl-6-methylaniline24549–06–20221NDND.01ND------3(4-Chlorophenyl)-1-methyl urea5352–88–50215NDND.036ND------4-Chloro-2-methylphenol1570–64–50221NDND.005ND------

# Appendixes **43 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Herbicides and herbicide degradates—ContinuedAcetochlor sulfynilacetic acid--073NDND0.02ND------Acetochlor/metolachlorethane sulfonic acid2nd amide--043NDND.02ND------Acifluorfen50594–66–60215NDND.028ND90HBSL--Alachlor sulfynilaceticacid140939–16–8073NDND.02ND------Benfluralin1861–40–10221NDND.01ND4HBSL--Bensulfuron-methyl83055–99–60215NDND.018ND1,000HBSL--Bromoxynil1689–84–50215NDND.044ND10HBSL--Chloramben, methylester7286–84–20215NDND.024ND------Chlorimuron-ethyl90982–32–40215NDND.032ND600HBSL--Cycloate1134–23–20215NDND.014ND40HBSL--Dacthal1861–32–10221NDND.003ND70HBSL--Dacthal monoacid(CCL)887–54–70215NDND.028ND------Dicamba1918–00–90213NDND.036ND3,000HBSL--Dichlorprop120–36–50215NDND.028ND300HBSL--Dimethenamid87674–68–8043NDND.02ND------Dimethenamid ethanesulfonic acid--073NDND.02ND------Dimethenamid oxanilicacid--073NDND.02ND------Diphenamid957–51–70215NDND.01ND200HBSL--

# 44 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Herbicides and herbicide degradates—ContinuedFenuron101–42–80215NDND0.1ND------Flufenacet142459–58–3043NDND.02ND------Flufenacet ethanesulfonic acid--073NDND.02ND------Flufenacet oxanilic acid--073NDND.02ND------Flumetsulam98967–40–90215NDND.04ND7,000HBSL--Linuron (CCL)330–55–20215NDND.014ND5HBSL--MCPA94–74–60207NDND.07ND30HBSL--MCPB94–81–50215NDND.1ND100HBSL--Neburon555–37–30215NDND.012ND------Nicosulfuron111991–09–40215NDND.04ND9,000HBSL--Oryzalin19044–88–30215NDND.023ND44HBSL--Pendimethalin40487–42–10221NDND.022ND70HBSL--Prometryn7287–19–60221NDND.0059ND300HBSL--Propachlor1918–16–7017NDND.02ND41HBSL--Propachlor ethanesulfonic acid--073NDND.05ND------Propachlor oxanilic acid--073NDND.02ND------Propham122–42–90215NDND.03ND100HBSL--Propyzamide23950–58–50221NDND.004ND41HBSL--Terbuthylazine5915–41–30221NDND.0083ND2HBSL--Triclopyr55335–06–30215NDND.026ND400HBSL--Trifluralin1582–09–80221NDND.009ND20HBSL--

# Appendixes **45 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Insecticides and insecticide degradatesCarbofuran1563–66–232151.4ND0.0160.00540MCL--Imidacloprid138261–41–332151.4ND.02.023400HBSL--1-Naphthol90–15–31221.5ND.0882E.006------Aldicarb sulfone1646–88–41215.5ND.018E.00777HBSL--Carbaryl63–25–21215.5ND.018E.012440HBSL--Chlorpyrofos, oxygenanalog5598–15–21221.5ND.0562E.017------Dieldrin60–57–11221.5ND.009.0244.002HBSL1(1)Fipronil120068–37–31221.5ND.016E.008------Fipronil sulfide120067–83–61221.5ND.013.007------Fipronil sulfone120068–36–21221.5ND.024.02------Fonofos, oxygen analog944–21–81206.5ND.0029.002------3-Hydroxycarbofuran16655–82–60215NDND.008ND------3-Ketocarbofuran16709–30–10213NDND1.5ND------Aldicarb116–06–30215NDND.15ND79HBSL--Aldicarb sulfoxide1646–87–30215NDND.1ND77HBSL--Azinphos-methyl86–50–00221NDND.05ND10HBSL--Azinphos-methyl-oxon961–22–80221NDND.042ND------Bendiocarb22781–23–30215NDND.08ND9HBSL--Chlorpyrifos2921–88–20221NDND.005ND2HBSL--cis-Permethrin54774–45–70221NDND.006ND4,84HBSL--Cyfluthrin68359–37–50221NDND.053ND200HBSL--Cypermethrin52315–07–80221NDND.046ND40HBSL--Desulfinylfipronil--0221NDND.012ND------

# 46 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Insecticides and insecticide degradates—ContinuedDesulfinylfipronil amide--0221NDND0.029ND------Diazinon (CCL)333–41–50221NDND.005ND1HBSL--Diazinon, oxygenanalog962–58–30221NDND.006ND------Dichlorvos62–73–70221NDND.013ND.4HBSL--Dicrotophos141–66–20221NDND.0843ND.05HBSL--Dimethoate60–51–50221NDND.0061ND2HBSL--Ethion563–12–20221NDND.016ND4HBSL--Ethion monoxon17356–42–20221NDND.021ND------Fenamiphos22224–92–60221NDND.029ND.7HBSL--Fenamiphos sulfone31972–44–80221NDND.053ND------Fenamiphos sulfoxide31972–43–70200NDND.04ND------Fonofos (CCL)944–22–90221NDND.0053ND10HBSL--Isofenphos25311–71–10221NDND.011ND6HBSL--Malaoxon1634–78–20221NDND.039ND------Malathion121–75–50221NDND.027ND50HBSL--Methidathion950–37–80221NDND.0087ND1HBSL--Methiocarb2032–65–70215NDND.034ND40HBSL--Methomyl16752–77–50215NDND.07ND200HBSL--Oxamyl23135–22–00215NDND.05ND200MCL--Paraoxon-methyl950–35–60221NDND.019ND------Parathion-methyl298–00–00221NDND.015ND1HBSL--Phorate298–02–20221NDND.055ND4HBSL--Phorate oxon2600–69–30221NDND.027ND------

# Appendixes **47 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Insecticides and insecticide degradates—ContinuedPhosmet732–11–60211NDND0.0079ND8HBSL--Phosmet oxon3735–33–90201NDND.0511ND------Propoxur114–26–10215NDND.008ND49HBSL--Terbufos (CCL)13071–79–90221NDND.017ND.4HBSL--Terbufos-oxygenanalog sulfone56070–15–60221NDND.045ND------Manufacturing additivesTriphenyl phosphate115–86–662023.0ND0.5E0.095------Tributyl phosphate126–73–852172.30.5.5E.12------Bisphenol A80–05–72212.9.916.4400HBSL--Tri(2-chloroethyl)phosphate3115–96–82217.9ND.5E.049------Tris(dichlorisopropyl)phosphate13674–87–82217.9ND.5E.022------Tri(2-butoxyethyl)phosphate78–51–31203.5.5.5E.14------5-Methyl-1H-benzotriazole136–85–60215NDND2ND------Organic synthesis compoundsCarbon disulfide75–15–031751.71.70.03812.7700HBSL--Vinyl chloride75–01–42221.9.9.08.72MCL1Acrylonitrile107–13–11221.5.5.8E.5044.06HBSL1(1)Anthraquinone84–65–11217.5.5.5E.11------Carbazole86–74–81217.5ND.5E.081------

# 48 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Organic synthesis compounds—Continued1,1-Dichloropropene(CCL)563–58–60221NDND0.026ND------1,2,3-Trichlorobenzene87–61–60221NDND.18ND------1,2,3-Trichloropropane96–18–40221NDND.18ND40HBSL--3-Chloro-1-propene107–05–10221NDND.5ND------Chloromethane74–87–30221NDND.17ND30HBSL--Ethyl methacrylate(Ethyl 2-methyl-2-propanoate)97–63–20221NDND.18ND------Hexachlorobutadiene(CCL)87–68–30221NDND.14ND4.9HBSL--Iodomethane74–88–40221NDND.5ND------Methyl acrylate(Methyl-2-propeno-ate)96–33–30221NDND1ND------Methyl acrylonitrile(2-Methyl-2-propene­nitrile)126–98–70221NDND.4ND.7HBSL--Methyl methacrylate(Methyl 2-methyl-2-propenoate)80–62–60221NDND.2ND10,000HBSL--trans-1,4-Dichloro-2-butene110–57–60221NDND.7ND------Vinyl bromide593–60–20221NDND.1ND------

# Appendixes **49 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Pavement- and combustion-derived compoundsFluoranthene206–44–052172.3ND0.5E0.044300HBSL--Pyrene129–00–052162.3ND.5E.046200HBSL--Phenanthrene385–01–832171.4ND.5E.016------Anthracene120–12–71217.5ND.5E.0242,000HBSL--Benzo[a]pyrene50–32–80217NDND.5ND.2MCL--Personal-care and domestic-use productsCaffeine58–08–2101686.0ND0.0180.0171------Hexahydrohexamethylcyclopentabenzopyran (HHCB)31222–05–572173.2ND.5E.036------Menthol89–78–162033.01.5E.2------Octylphenol diethoxylate (total)3--42171.8.91E.12------4-tert-Octylphenol140–66–932171.4ND1E.087------Methyl salicylate3119–36–832171.4.5.5E.114,000HBSL--Octylphenol monoethoxylate (total)--32171.41.41E.59------4-Cumylphenol599–64–41217.5.51E.18------Acetyl hexamethyltetrahydronaphthalene (AHTN)321145–77–71217.5ND.5E.005------Indole120–72–91217.5ND.5E.08------Triclosan3380–34–51217.5ND1E.065------3-tert-Butyl-4-hydroxyanisole (BHA)25013–16–50217NDND5ND------4-n-Octylphenol1806–26–40217NDND1ND------

# 50 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Personal-care and domestic-use products—ContinuedNonylphenol diethoxyl-ate (total)26027–38–20217NDND5ND------Acetophenone98–86–20187NDND.5ND700HBSL--Benzophenone119–61–9--R----.5ND------Bromochloromethane74–97–50221NDND.12ND90HBSL--Camphor376–22–20217NDND.5ND------Cotinine486–56–60118NDND1ND------d-Limonene5989–27–50217NDND.5ND------Isoborneol124–76–50217NDND.5ND------Isoquinoline119–65–30217NDND.5ND------N,N-diethyl-meta-toluamide (DEET)134–62–3--R----.5ND------para-Nonylphenol(total)84852–15–3--R----5ND------Phenol108–95–2--R----.5ND2,000HBSL--Triethyl citrate (Ethylcitrate)77–93–00217NDND.5ND------Plant- or animal-derived biochemicals3-beta-Coprostanol360–68–922170.90.92E0.34------Cholesterol357–88–52217.9.92E.53------3-Methyl-1(H)-indole(Skatole)83–34–11217.5ND1E.027------beta-Sitosterol83–46–51217.5.52E.39------beta-Stigmastanol19466–47–81217.5.52E.36------

# Appendixes **51 Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,benchmark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con********centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** ******centrations with BQ** **>0.1; (1) number of** **concentrations with BQ** **>1 All data** **Censored at 0.1** **μg/L**Refrigerants and propellantsTrichlorofluoromethane(CFC-11)375–69–452212.30.50.080.2752,000HBSL--1,1,2-Trichloro-1,2,2-trifluoroethane(CFC-113)76–13–142211.8.9.0381.06200,000HBSL--Dichlorodifluoromethane (CFC-12)75–71–832211.4.5.18E.1451,000HBSL--SolventsPerchloroethene (PCE)3127–18–44322119.5100.035.475MCL4(1)Trichloroethene (TCE)79–01–63122114.06.3.03869.55MCL3(2)1,1,1-Trichloroethane71–55–6212219.53.2.03216.7200MCL--cis-1,2-Dichloroethene156–59–2212219.54.1.0241.570MCL--1,1-Dichloroethane(CCL)75–34–3132215.92.7.0354.88------1,1-Dichloroethene75–35–4112215.01.8.0246.537MCL11,2-Dichloroethane107–06–242211.81.4.13.25MCL--p-Cresol106–44–542171.8.91E.19------trans-1,2-Dichloroethene156–60–542211.8.5.032E.11100MCL--Carbon tetrachloride(Tetrachloromethane)56–23–532211.4.5.06.6775MCL11,1,2-Trichloroethane79–00–51220.5ND.04E.085MCL--Methyl isobutyl ketone(4-Methyl-2-pentanone; MIBK)108–10–11221.5.5.37E.766------Dibromomethane74–95–31221.5ND.05E.065------

# 52 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 1.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source-water samples collectedduring October2002–July2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest detection frequency. CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ,bench-mark quotient; >, greater than; MCL, Maximum Contaminant Level; --, none; ND, not detected; E, estimated value; CCL, U.S. Environmental ProtectionAgency’s Contaminant Candidate List 2 (U.S. Envi-ronmental Protection Agency, 2005); HBSL, Health-Based Screening Level; MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compound removed from thedataset]**Compound CASRN** **1 Number of** **detections for** **ground- water** **Number of** **samples Detection frequency** **(percent) Laboratory** **reporting level (μg/L)** **Maximum con -** **centration for groundwater** **(μg/L) Human-health** **benchmark (μg/L)** **Type of human-health** **benchmark Number of con** **- centrations with** **BQ >0.1;** **(1) number of concentrations** **with BQ >1** **All data Censored** **at 0.1 μg/L** Solvents—ContinuedMethyl ethyl ketone(MEK)378–93–312210.50.52330.24,000HBSL--n-Propylbenzene103–65–11221.5.5.042.108------Tetrahydrofuran3109–99–91221.5.51.21,020------1,1,1,2-Tetrachloroethane630–20–60221NDND.03ND70HBSL--1,1,2,2-Tetrachloroethane (CCL)79–34–50221NDND.08ND.3HBSL--Diethyl ether(1,1’-Oxybisethane)60–29–70221NDND.08ND1,000HBSL--1,2,4-Trichlorobenzene120–82–10221NDND.12ND70MCL--1,2-Dichlorobenzene95–50–10221NDND.048ND600MCL--1,3-Dichlorobenzene541–73–10221NDND.03ND600HBSL--2-Chlorotoluene95–49–80221NDND.04ND100HBSL--2-Hexanone591–78–60221NDND.4ND------4-Chlorotoluene106–43–40221NDND.05ND100HBSL--Acetone67–64–10161NDND6ND6,000HBSL--Bromobenzene (CCL)108–86–10221NDND.028ND------Chlorobenzene108–90–70206NDND.028ND100MCL--Chloroethane75–00–30221NDND.12ND------Hexachloroethane67–72–10221NDND.14ND.7HBSL--Isophorone378–59–1--R----.5ND100HBSL--Methyl acetate79–20–90119NDND.43ND------Methylene chloride(Dichloromethane)75–09–20192NDND.06ND5MCL--

# Appendixes **53**1This report contains CASRNs, which is a Registered Trademark of the American Chemical Society. The Chemical Abstracts Service (CAS) recommends the verification of the CASRNs through CAS ClientServicesSM.2The U.S. Environmental Protection Agency’s MCL of 80 μg/L is for the sum of the concentrations of four trihalomethanes.3Compound was detected in only one field blank.4HBSL 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).5The 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 542–75–6.6The concentrations fromm- andp-xylene ando-xylene may be compared to the MCL (10,000 μg/L) for mixed xylenes, CASRN 1330–20–7.7U.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.8Concentrations ofcis-permethrin may be compared to the HBSL range (4–400 μg/L) for permethrin, CASRN 52645–53–1.

# 54 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Basin and Range basin-fill aquifers

Unconsolidated and semiconsolidated sediments NVBR-0001 510

--

Unconsolidated and semiconsolidated sediments NVBR-0002 590

--

Unconsolidated and semiconsolidated sediments NVBR-0003 560

--

Unconsolidated and semiconsolidated sediments NVBR-0004 195

--

Unconsolidated and semiconsolidated sediments NVBR-0005 820

--

Unconsolidated and semiconsolidated sediments NVBR-0006 470

--

Unconsolidated and semiconsolidated sediments NVBR-0007 470 Yes 1



# Unconsolidated and semiconsolidated sediments NVBR-0008 1,250

--

Unconsolidated and semiconsolidated sediments NVBR-0009 400 Yes 1



# Unconsolidated and semiconsolidated sediments NVBR-0010 455

--

Unconsolidated and semiconsolidated sediments NVBR-0011 200

--

Unconsolidated and semiconsolidated sediments NVBR-0012 620

--

Unconsolidated and semiconsolidated sediments NVBR-0013 600

--

Unconsolidated and semiconsolidated sediments NVBR-0014 400

--

Unconsolidated and semiconsolidated sediments NVBR-0015 330

--

Cambrian-Ordovician aquifer system

Sandstone and carbonate rock UMIS-0001 403 Yes 1



# Sandstone and carbonate rock UMIS-0002 493 Yes 1



# Sandstone and carbonate rock UMIS-0003 500

--

Sandstone and carbonate rock UMIS-0004 399 Yes 1



# Sandstone and carbonate rock UMIS-0005 407

--

Sandstone and carbonate rock UMIS-0006 408

--

Sandstone and carbonate rock UMIS-0007 500

--

Sandstone and carbonate rock UMIS-0008 401

--

Sandstone and carbonate rock UMIS-0009 495 Yes 1



# Sandstone and carbonate rock UMIS-0010 548 Yes 1



# Sandstone and carbonate rock UMIS-0011 387 Yes 1



# Sandstone and carbonate rock UMIS-0012 507 No 1



# Sandstone and carbonate rock UMIS-0013 513

--

Sandstone and carbonate rock UMIS-0014 345 Yes 1



# Sandstone and carbonate rock UMIS-0015 317

--

Central Valley aquifer system

Unconsolidated and semiconsolidated sediments SANJ-0001 215 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0002 208

--

Unconsolidated and semiconsolidated sediments SANJ-0003 250 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0004 220

--

Unconsolidated and semiconsolidated sediments SANJ-0005 216 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0006 262 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0007 220 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0008 218

--

# Appendixes **55**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Central Valley aquifer system—Continued

Unconsolidated and semiconsolidated sediments SANJ-0009 302 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0010 245

--

Unconsolidated and semiconsolidated sediments SANJ-0011 391 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0012 220 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0013 307 Yes 1



# Unconsolidated and semiconsolidated sediments SANJ-0014 385

--

Unconsolidated and semiconsolidated sediments SANJ-0015 415 Yes 1



# Coastal Lowlands aquifer system

Unconsolidated and semiconsolidated sediments TRIN-0001 1,012

--

Unconsolidated and semiconsolidated sediments TRIN-0002 1,394

--

Unconsolidated and semiconsolidated sediments TRIN-0003 1,370

--

Unconsolidated and semiconsolidated sediments TRIN-0004 1,665

--

Unconsolidated and semiconsolidated sediments TRIN-0005 1,135

--

Unconsolidated and semiconsolidated sediments TRIN-0006 1,712 Yes 1



# Unconsolidated and semiconsolidated sediments TRIN-0007 1,374 Yes 1



# Unconsolidated and semiconsolidated sediments TRIN-0008 1,200

--

Unconsolidated and semiconsolidated sediments TRIN-0009 1,379

--

Unconsolidated and semiconsolidated sediments TRIN-0010 1,480

--

Unconsolidated and semiconsolidated sediments TRIN-0011 1,438

--

Unconsolidated and semiconsolidated sediments TRIN-0012 1,444

--

Unconsolidated and semiconsolidated sediments TRIN-0013 1,480

--

Unconsolidated and semiconsolidated sediments TRIN-0014 1,050 Yes 1



# Unconsolidated and semiconsolidated sediments TRIN-0015 1,630 Yes 1



# Columbia Plateau basin-fill and basaltic-rock aquifers

Igneous and metamorphic rocks CCYK-0001 954

--

Igneous and metamorphic rocks CCYK-0002 919

--

Unconsolidated and semiconsolidated sediments CCYK-0003 188 No 1



# Unconsolidated and semiconsolidated sediments CCYK-0004 1,171

--

Igneous and metamorphic rocks CCYK-0005 1,624

--

Igneous and metamorphic rocks CCYK-0006 1,011

--

Igneous and metamorphic rocks CCYK-0007 718 No 1



# Igneous and metamorphic rocks CCYK-0008 900

--

Igneous and metamorphic rocks CCYK-0009 1,320

--

Igneous and metamorphic rocks CCYK-0010 368

--

Igneous and metamorphic rocks CCYK-0011 617

--

Igneous and metamorphic rocks CCYK-0012 750 No 1



# Igneous and metamorphic rocks CCYK-0013 380 No 1



# Igneous and metamorphic rocks CCYK-0014 618

--

Igneous and metamorphic rocks CCYK-0015 525

--

# 56 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Denver Basin aquifer system

Sandstone and carbonate rock SPLT-0001 536

--

Sandstone and carbonate rock SPLT-0002 1,115

--

Sandstone and carbonate rock SPLT-0003 390

--

Sandstone and carbonate rock SPLT-0004 850

--

Sandstone and carbonate rock SPLT-0005 575

--

Sandstone and carbonate rock SPLT-0006 740

--

Sandstone and carbonate rock SPLT-0007 NA

--

Sandstone and carbonate rock SPLT-0008 NA

--

Sandstone and carbonate rock SPLT-0009 433

--

Sandstone and carbonate rock SPLT-0010 561

--

Sandstone and carbonate rock SPLT-0011 245

--

Sandstone and carbonate rock SPLT-0012 NA

--

Edwards-Trinity aquifer system

Sandstone and carbonate rock SCTX-0001 525

--

Sandstone and carbonate rock SCTX-0002 1,800

--

Sandstone and carbonate rock SCTX-0003 1,040

--

Sandstone and carbonate rock SCTX-0004 1,114

--

Sandstone and carbonate rock SCTX-0005 1,150 Yes 1



# Sandstone and carbonate rock SCTX-0006 748 No 1



# Sandstone and carbonate rock SCTX-0007 760

--

Sandstone and carbonate rock SCTX-0008 808 Yes 1



# Sandstone and carbonate rock SCTX-0009 1,050 Yes 1



# Sandstone and carbonate rock SCTX-0010 877

--

Sandstone and carbonate rock SCTX-0011 848 Yes 1



# Sandstone and carbonate rock SCTX-0012 870

--

Sandstone and carbonate rock SCTX-0013 811 Yes 1



# Sandstone and carbonate rock SCTX-0014 710 Yes 1



# Sandstone and carbonate rock SCTX-0015 365 No 1



# Floridan aquifer system

Sandstone and carbonate rock GAFL-0001 405

--

Sandstone and carbonate rock GAFL-0002 305 Yes 1



# Sandstone and carbonate rock GAFL-0003 105

--

Sandstone and carbonate rock GAFL-0004 174 Yes 1



# Sandstone and carbonate rock GAFL-0005 700

--

Sandstone and carbonate rock GAFL-0006 350

--

Sandstone and carbonate rock GAFL-0007 590

--

Sandstone and carbonate rock GAFL-0008 601

--

Sandstone and carbonate rock GAFL-0009 610 Yes 1



# Sandstone and carbonate rock GAFL-0010 550

--

Sandstone and carbonate rock GAFL-0011 700

--

# Appendixes **57**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Floridan aquifer system—Continued

Sandstone and carbonate rock GAFL-0012 311

--

Sandstone and carbonate rock GAFL-0013 575 No 1



# Sandstone and carbonate rock GAFL-0014 90 Yes 1



# Sandstone and carbonate rock GAFL-0015 840 No 1



# Sandstone and carbonate rock GAFL-0016 750 Yes 1



# Sandstone and carbonate rock GAFL-0017 300

--

Sandstone and carbonate rock GAFL-0018 705

--

Sandstone and carbonate rock GAFL-0019 121

--

Sandstone and carbonate rock GAFL-0020 702

--

Sandstone and carbonate rock GAFL-0021 150

--

Sandstone and carbonate rock GAFL-0022 710

--

Sandstone and carbonate rock GAFL-0023 710

--

Sandstone and carbonate rock GAFL-0024 430 No 1



# Sandstone and carbonate rock GAFL-0025 350 No 1



# Sandstone and carbonate rock GAFL-0026 625 No 1



# Sandstone and carbonate rock GAFL-0027 484

--

Sandstone and carbonate rock GAFL-0028 400 No 1



# Sandstone and carbonate rock GAFL-0029 600

--

Sandstone and carbonate rock GAFL-0030 602

--

Glacial deposits aquifer system

Unconsolidated glacial deposits WHMI-0001 123 Yes 1



# Unconsolidated glacial deposits WHMI-0002 151

--

Unconsolidated glacial deposits WHMI-0003 125

--

Unconsolidated glacial deposits WHMI-0004 77

--

Unconsolidated glacial deposits WHMI-0005 80

--

Unconsolidated glacial deposits WHMI-0006 83

--

Unconsolidated glacial deposits WHMI-0007 152

--

Unconsolidated glacial deposits WHMI-0008 60 Yes 1



# Unconsolidated glacial deposits WHMI-0009 157

--

Unconsolidated glacial deposits WHMI-0010 137

--

Unconsolidated glacial deposits WHMI-0011 61 Yes 1



# Unconsolidated glacial deposits WHMI-0012 146 Yes 1



# Unconsolidated glacial deposits WHMI-0013 94

--

Unconsolidated glacial deposits WHMI-0014 84 Yes 1



# Unconsolidated glacial deposits CONN-0001 83

--

Unconsolidated glacial deposits CONN-0002 70

--

Unconsolidated glacial deposits CONN-0003 76 Yes 1



# Unconsolidated glacial deposits CONN-0004 64 Yes 1



# Unconsolidated glacial deposits CONN-0005 40 No 1



# Unconsolidated glacial deposits CONN-0006 38

--

# 58 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Glacial deposits aquifer system—Continued

Unconsolidated glacial deposits CONN-0007 54 No 1



# Unconsolidated glacial deposits CONN-0008 102 No 1



# Unconsolidated glacial deposits CONN-0009 126 No 1



# Unconsolidated glacial deposits CONN-0010 90 No 1



# Unconsolidated glacial deposits CONN-0011 40 Yes 1



# Unconsolidated glacial deposits CONN-0012 70 No 1



# Unconsolidated glacial deposits CONN-0013 130

--

Unconsolidated glacial deposits CONN-0014 93 No 1



# Unconsolidated glacial deposits CONN-0015 58

--

Unconsolidated glacial deposits UMIS-0016 292

--

Unconsolidated glacial deposits UMIS-0017 152 Yes 1



# Unconsolidated glacial deposits UMIS-0018 215

--

Unconsolidated glacial deposits UMIS-0019 194

--

Unconsolidated glacial deposits UMIS-0020 100

--

Unconsolidated glacial deposits UMIS-0021 205

--

Unconsolidated glacial deposits UMIS-0022 199 Yes 1



# Unconsolidated glacial deposits UMIS-0023 213

--

Unconsolidated glacial deposits UMIS-0024 270 Yes 1



# Unconsolidated glacial deposits UMIS-0025 197 Yes 1



# Unconsolidated glacial deposits UMIS-0026 157

--

Unconsolidated glacial deposits UMIS-0027 310

--

Unconsolidated glacial deposits UMIS-0028 250

--

Unconsolidated glacial deposits UMIS-0029 217

--

Unconsolidated glacial deposits UMIS-0030 344 No 1



# High Plains aquifer

Unconsolidated and semiconsolidated sediments HPGW-0001 190 Yes 1



# Unconsolidated and semiconsolidated sediments HPGW-0002 381

--

Unconsolidated and semiconsolidated sediments HPGW-0003 195

--

Unconsolidated and semiconsolidated sediments HPGW-0004 253

--

Unconsolidated and semiconsolidated sediments HPGW-0005 292

--

Unconsolidated and semiconsolidated sediments HPGW-0006 356

--

Unconsolidated and semiconsolidated sediments HPGW-0007 340

--

Unconsolidated and semiconsolidated sediments HPGW-0008 369

--

Unconsolidated and semiconsolidated sediments HPGW-0009 218

--

Unconsolidated and semiconsolidated sediments HPGW-0010 380

--

Unconsolidated and semiconsolidated sediments HPGW-0011 228

--

Unconsolidated and semiconsolidated sediments HPGW-0012 394

--

Unconsolidated and semiconsolidated sediments HPGW-0013 120 Yes 1



# Unconsolidated and semiconsolidated sediments HPGW-0014 425

--

Unconsolidated and semiconsolidated sediments HPGW-0015 136

--

# Appendixes **59**

**Appendix 2.** Selected characteristics of community water system wells sampled for Source Water-Quality Assessments,

2002–05. —Continued

[NA, not available; -- not applicable]



# Primary lithology **Site name Well depth** 

**(feet) Blended** 

Piedmont and Blue Ridge crystalline-rock aquifers

Igneous and metamorphic rocks PODL-0001 400

--

Igneous and metamorphic rocks PODL-0002 705

--

Igneous and metamorphic rocks PODL-0003 386

--

Igneous and metamorphic rocks PODL-0004 NA No 1



# Igneous and metamorphic rocks PODL-0005 280 No 1



# Igneous and metamorphic rocks PODL-0006 200

--

Igneous and metamorphic rocks PODL-0007 95 Yes 1



# Igneous and metamorphic rocks PODL-0008 182 No 1



# Igneous and metamorphic rocks PODL-0009 300 Yes 1



# Igneous and metamorphic rocks PODL-0010 NA Yes 1



# Igneous and metamorphic rocks PODL-0011 642 Yes 1



# Igneous and metamorphic rocks PODL-0012 500 No 1



# Igneous and metamorphic rocks PODL-0013 623 No 1



# Igneous and metamorphic rocks PODL-0014 241

--

Igneous and metamorphic rocks PODL-0015 300 No 1



# Rio Grande aquifer system

Unconsolidated and semiconsolidated sediments RIOG-0001 1,400 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0002 1,166 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0003 996 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0004 1,191 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0005 1,670 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0006 1,287 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0007 814 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0008 984 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0009 1,194 Yes 1



# Unconsolidated and semiconsolidated sediments RIOG-0010 1,730 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0011 2,070 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0012 1,957 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0013 1,020 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0014 2,010 No 1



# Unconsolidated and semiconsolidated sediments RIOG-0015 1,487 No 1

1 

# Site re-sampled during the second phase for source water and finished water

.

# 60 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Disinfection by-productsChloroform67–66–356/5657883.2536.3280--3Bromodichloromethane75–27–471/711379.2047.48280----Dibromochloromethane124–48–171/717.072.4337.95280----Bromoform75–25–271/717.062.3968.37280--1Trihalomethanes--71/7157883.2845.380--9Fumigant-related compounds1,4-Dichlorobenzene106–46–771/711111E0.048E0.05675----1,2-Dichloropropane78–87–571/711.4NDE.025ND5----1,2-Dibromo-3-chloro-propane96–12–871/71NDNDNDND.2----1,2-Dibromoethane106–93–471/71NDNDNDND.05----1,3-Dichloropropane(CCL)142–28–971/71NDNDNDND------2,2-Dichloropropane(CCL)594–20–771/71NDNDNDND------Bromomethane (CCL)74–83–971/71NDNDNDND100----cis-1,3-Dichloropropene(CCL)10061–01–571/71NDNDNDND3,4.3----trans-1,3-Dichloropro-pene (CCL)10061–02–671/71NDNDNDND3,4.3----Fungicides and fungicide degradatesBenomyl17804–35–261/593.33.4E0.026E0.02640----Metalaxyl57837–19–148/482.12.1.01.071600----Chlorothalonil1897–45–661/59NDNDNDND5----Iprodione36734–19–748/48NDNDNDND3.8----Myclobutanil88671–89–048/48NDNDNDND200----

# Appendixes **61 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Fungicides and fungicide degradates—ContinuedPentachlorophenol87–86–542/44NDNDNDND1----Propiconazole60207–90–161/59NDNDNDND70----Gasoline hydrocarbons, oxygenates, and oxygenate degradatesMethyltert-butyl ether(MTBE) (CCL)1634–04–471/7116167.846.03------Benzene71–43–266/664.51.5.13.125----tert-Amyl methyl ether(TAME)994–05–871/714.24.2.935.66------Diisopropyl ether(DIPE)108–20–371/712.82.8.165.148------Ethyltert-butyl ether(ETBE)637–92–371/711.41.4.241.15------m-andp-Xylene106–42–3;108–38–364/64ND14ND2.26510,000----Ethylbenzene100–41–464/64ND9.4ND.593700----o-Xylene95–47–666/66ND9.1ND1.03510,000----1-Methylnaphthalene90–12–055/57ND1.8NDE.014------2-Methylnaphthalene91–57–655/57ND1.8NDE.02530----1,2,3,4-Tetramethylbenzene488–23–371/71NDNDNDND------1,2,3,5-Tetramethylbenzene527–53–771/71NDNDNDND------1,2,3-Trimethylbenzene526–73–871/71NDNDNDND------1,2,4-Trimethylbenzene(CCL)95–63–664/64NDNDNDND------1,3,5-Trimethylbenzene108–67–871/71NDNDNDND------

# 62 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Gasoline hydrocarbons, oxygenates, and oxygenate degradates—Continued1-Ethyl-2-methylben-zene (o-Ethyl toluene)611–14–371/71NDNDNDND------2,6-Dimethylnaphtha-lene581–42–055/57NDNDNDND------tert-Amyl alcohol(2-Methyl-2-butanol)75–85–415/15NDNDNDND------Isopropylbenzene98–82–871/71NDNDNDND700----Naphthalene (CCL)91–20–371/71NDNDNDND100----n-Butylbenzene104–51–871/71NDNDNDND------p-Isopropyltoluene(CCL)99–87–671/71NDNDNDND------sec-Butylbenzene135–98–871/71NDNDNDND------Styrene100–42–571/71NDNDNDND100----tert-Butyl alcohol75–65–015/15NDNDNDND------tert-Butylbenzene98–06–671/71NDNDNDND------Toluene108–88–334/34NDNDNDND1,000----Herbicides and herbicide degradatesAlachlor ethane sulfonicacid--17/1777770.680.53------Atrazine1912–24–966/665955.23.2033----Deethylatrazine (DEA)(CCL)6190–65–466/665653.288.151------Metolachlor ethanesulfonic acid--32/3247413.952.89------Simazine122–34–948/484646.047.0444----

# Appendixes **63 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Herbicides and herbicide degradates—ContinuedMetolachlor oxanilicacid--32/3238343.772.99------Deisopropylatrazine(DIA)1007–28–961/593120.138.058------2-Hydroxyatrazine2163–68–061/592829E.029E.02370----Alachlor oxanilic acid--32/322528.84.75------Prometon (CCL)1610–18–061/622519.024.03400----Acetochlor ethanesulfonic acid--32/321919.77.8------Bentazon25057–89–061/59136.8E.748E.37200----Alachlor ethane sulfonicacid 2nd amide--32/321313.1.21------Metolachlor (CCL)51218–45–264/651311.04.021700----Acetochlor oxanilic acid--32/329.419.41.53------Bromacil314–40–979/787.6ND.258ND70----Diuron (CCL)330–54–161/596.61.7.113.09932----Flufenacet142459–58–332/326.23.1.02.04------Flumetsulam98967–40–960/593.35.1E.122E.0987,000----Acetochlor/metolachlorethane sulfonic acid2nd amide--32/323.113.1.12------Dimethenamid ethanesulfonic acid--32/323.1ND.02ND------3,4-Dichloroaniline95–76–148/482.14.2E.002.01------Hexazinone51235–04–248/482.1ND.017ND400----

# 64 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Herbicides and herbicide degradates—ContinuedImazaquin81335–37–761/591.63.4E0.016E0.0172,000----3(4-Chlorophenyl)-1-methyl urea5352–88–561/591.61.7E.004E.004------Chlorimuron-ethyl90982–32–461/591.61.7E.016E.019600----Oryzalin19044–88–361/591.61.7E.01E.07534----Sulfometuron-methyl74222–97–261/591.61.7.036E.0072,000----Triclopyr55335–06–361/591.61.7.032.026400----Deethyldeisopropylatrazine (DDA)3397–62–461/591.6NDE.052ND------Nicosulfuron111991–09–461/591.6NDE.006ND9,000----Terbacil (CCL)5902–51–261/591.6NDE.023ND90----Tebuthiuron34014–18–166/661.53.034.031,000----Metsulfuron methyl74223–64–661/59ND12NDE.1052,000----4-Chloro-2-methylphenol1570–64–548/48ND4.2NDE.006------Metribuzin (CCL)21087–64–948/48ND2.1NDE.00490----Imazethapyr81335–77–561/59ND1.7NDE.0042,000----Picloram1918–02–161/59ND1.7ND.151500----2,4–D94–75–761/59NDNDNDND70----2,4–D methyl ester1928–38–761/59NDNDNDND------2,4–DB94–82–661/59NDNDNDND200----2,6-Diethylaniline579–66–848/48NDNDNDND------2-Chloro-2,6-diethylacetanilide6967–29–948/48NDNDNDND------2-Ethyl-6-methylaniline24549–06–248/48NDNDNDND------

# Appendixes **65 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Herbicides and herbicide degradates—ContinuedAcetochlor (CCL)34256–82–151/51NDNDNDND31----Acetochlor sulfynilacetic acid--32/32NDNDNDND------Acifluorfen50594–66–661/59NDNDNDND90----Alachlor15972–60–851/51NDNDNDND2----Alachlor sulfynilaceticacid140939–16–832/32NDNDNDND------Benfluralin1861–40–148/48NDNDNDND4----Bensulfuron-methyl83055–99–661/59NDNDNDND1,000----Bromoxynil1689–84–561/59NDNDNDND10----Chloramben, methylester7286–84–261/59NDNDNDND------Clopyralid1702–17–661/59NDNDNDND------Cycloate1134–23–261/59NDNDNDND40----Dacthal1861–32–148/48NDNDNDND70----Dacthal monoacid(CCL)887–54–761/59NDNDNDND------Dicamba1918–00–961/59NDNDNDND3,000----Dichlorprop120–36–561/59NDNDNDND300----Dimethenamid87674–68–832/32NDNDNDND------Dimethenamid oxanilicacid--32/32NDNDNDND------Dinoseb88–85–761/59NDNDNDND7----Diphenamid957–51–761/59NDNDNDND200----Fenuron101–42–861/59NDNDNDND------

# 66 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Herbicides and herbicide degradates—ContinuedFlufenacet ethanesulfonic acid--32/32NDNDNDND------Flufenacet oxanilic acid--32/32NDNDNDND------Fluometuron2164–17–261/59NDNDNDND4----Linuron (CCL)330–55–261/59NDNDNDND5----MCPA94–74–658/57NDNDNDND30----MCPB94–81–561/59NDNDNDND100----Neburon555–37–361/59NDNDNDND------Norflurazon27314–13–261/59NDNDNDND10----Pendimethalin40487–42–148/48NDNDNDND70----Prometryn7287–19–648/48NDNDNDND300----Propachlor1918–16–720/20NDNDNDND31----Propachlor ethanesulfonic acid--32/32NDNDNDND------Propachlor oxanilic acid--32/32NDNDNDND------Propham122–42–961/59NDNDNDND100----Propyzamide23950–58–548/48NDNDNDND31----Siduron1982–49–661/59NDNDNDND1,000----Terbuthylazine5915–41–348/48NDNDNDND2----Trifluralin1582–09–848/48NDNDNDND20----Insecticides and insecticide degradatesImidacloprid138261–41–361/596.65.10.0170.016400----Fipronil120068–37–348/484.2NDE.006ND------

# Appendixes **67 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Insecticides and insecticide degradates—ContinuedFipronil sulfide120067–83–648/482.12.1E0.007E0.008------Diazinon (CCL)333–41–561/621.61.6.01.00521----1-Naphthol90–15–348/48NDNDNDND------3-Hydroxycarbofuran16655–82–661/59NDNDNDND------3-Ketocarbofuran16709–30–159/57NDNDNDND------Aldicarb116–06–361/59NDNDNDND69----Aldicarb sulfone1646–88–461/59NDNDNDND67----Aldicarb sulfoxide1646–87–361/59NDNDNDND67----Azinphos-methyl86–50–048/48NDNDNDND210----Azinphos-methyl-oxon961–22–848/48NDNDNDND------Bendiocarb22781–23–361/59NDNDNDND9----Carbaryl63–25–261/59NDNDNDND340----Carbofuran1563–66–261/59NDNDNDND40----Chlorpyrifos2921–88–261/62NDNDNDND2----Chlorpyrofos, oxygenanalog5598–15–248/48NDNDNDND------cis-Permethrin54774–45–748/48NDNDNDND3,74----Cyfluthrin68359–37–548/48NDNDNDND200----Cypermethrin52315–07–848/48NDNDNDND40----Desulfinylfipronil--48/48NDNDNDND------Desulfinylfipronil amide--48/48NDNDNDND------Diazinon, oxygenanalog962–58–338/38NDNDNDND------Dichlorvos62–73–749/49NDNDNDND.4----

# 68 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Insecticides and insecticide degradates—ContinuedDicrotophos141–66–248/48NDNDNDND0.05----Dieldrin60–57–148/48NDNDNDND3.002----Dimethoate60–51–548/48NDNDNDND2----Ethion563–12–248/48NDNDNDND4----Ethion monoxon17356–42–248/48NDNDNDND------Fenamiphos22224–92–648/48NDNDNDND.7----Fenamiphos sulfone31972–44–848/48NDNDNDND------Fenamiphos sulfoxide31972–43–748/48NDNDNDND------Fipronil sulfone120068–36–248/48NDNDNDND------Fonofos (CCL)944–22–948/48NDNDNDND10----Fonofos, oxygen analog944–21–823/23NDNDNDND------Isofenphos25311–71–148/48NDNDNDND6----Malaoxon1634–78–248/48NDNDNDND------Malathion121–75–548/48NDNDNDND50----Methidathion950–37–848/48NDNDNDND1----Methiocarb2032–65–761/59NDNDNDND40----Methomyl16752–77–561/59NDNDNDND200----Oxamyl23135–22–061/59NDNDNDND200----Paraoxon-methyl950–35–648/48NDNDNDND------Parathion-methyl298–00–048/48NDNDNDND1----Phorate298–02–248/48NDNDNDND4----Phorate oxon2600–69–348/48NDNDNDND------Phosmet732–11–634/34NDNDNDND28----Phosmet oxon3735–33–932/33NDNDNDND------

# Appendixes **69 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Insecticides and insecticide degradates—ContinuedPropoxur114–26–161/59NDNDNDND39----Terbufos (CCL)13071–79–948/48NDNDNDND.4----Terbufos-oxygen-analogsulfone56070–15–648/48NDNDNDND------Manufacturing additivesTributyl phosphate126–73–855/579.11.8E0.16E0.009------Tri(2-chloroethyl)phosphate115–96–855/575.51.8E.13E.099------Tris(dichlorisopropyl)phosphate13674–87–855/575.5NDE.081ND------Tri(2-butoxyethyl)phosphate78–51–341/432.44.7E.18E.33------Bisphenol A80–05–743/472.3ND2.5ND400----Triphenyl phosphate115–86–653/551.920E.083E.26------5-Methyl-1H-benzotriazole136–85–653/55NDNDNDND------Organic synthesis compoundsCarbon disulfide75–15–063/641.6ND0.116ND700----Vinyl chloride75–01–471/711.4ND.4ND21--Chloromethane74–87–371/71ND2.8NDE.11630----Carbazole86–74–855/57ND1.8NDE.005------1,1-Dichloropropene(CCL)563–58–671/71NDNDNDND------1,2,3-Trichlorobenzene87–61–671/71NDNDNDND------1,2,3-Trichloropropane96–18–471/71NDNDNDND40----3-Chloro-1-propene107–05–171/71NDNDNDND------

# 70 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Organic synthesis compounds—ContinuedAcrylonitrile107–13–171/71NDNDNDND30.06----Anthraquinone84–65–155/57NDNDNDND------Ethyl methacrylate(Ethyl 2-methyl-2-propanoate)97–63–271/71NDNDNDND------Hexachlorobutadiene(CCL)87–68–371/71NDNDNDND3.9----Iodomethane74–88–471/71NDNDNDND------Methyl acrylate(Methyl-2-propeno-ate)96–33–371/71NDNDNDND------Methyl acrylonitrile(2-Methyl-2-propene­nitrile)126–98–771/71NDNDNDND.7----Methyl methacrylate(Methyl 2-methyl-2-propenoate)80–62–671/71NDNDNDND10,000----trans-1,4-Dichloro-2-butene110–57–671/71NDNDNDND------Vinyl bromide593–60–271/71NDNDNDND------Pavement- and combustion-derived compoundsPhenanthrene85–01–855/573.65.3E0.017E0.02------Anthracene120–12–755/57NDNDNDND2,000----Benzo[a]pyrene50–32–855/57NDNDNDND.2----Fluoranthene206–44–055/57NDNDNDND300----Pyrene129–00–055/57NDNDNDND200----

# Appendixes **71 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Personal-care and domestic-use productsHexahydrohexamethylcyclopentabenzopyran (HHCB)1222–05–555/575.53.5E0.081E0.088------Caffeine58–08–240/385.0NDE.006ND------Acetyl hexamethyltetrahydronaphthalene (AHTN)21145–77–755/573.6NDE.079ND------Nonylphenol diethoxylate (total)26027–38–255/573.6NDE3.2ND------Octylphenol diethoxylate (total)--55/573.6NDE.089ND------Octylphenol monoethoxylate (total)--55/573.6NDE.32ND------Methyl salicylate119–36–855/571.83.5E.014E.064,000----Camphor76–22–255/571.81.8E.004E.013------4-tert-Octylphenol140–66–955/571.8NDE.079ND------Menthol89–78–141/43ND2.3NDE.033----3-tert-Butyl-4-hydroxyanisole (BHA)25013–16–555/57NDNDNDND------4-Cumylphenol599–64–455/57NDNDNDND------4-n-Octylphenol1806–26–455/57NDNDNDND------Acetophenone98–86–249/51NDNDNDND700----Benzophenone119–61–9R--------------Bromochloromethane74–97–571/71NDNDNDND90----Cotinine486–56–654/55NDNDNDND------d-Limonene5989–27–555/57NDNDNDND------

# 72 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Personal-care and domestic-use products—ContinuedIndole120–72–955/57NDNDNDND------Isoborneol124–76–555/57NDNDNDND------Isoquinoline119–65–355/57NDNDNDND------N,N-diethyl-meta-tolu­amide (DEET)134–62–3R--------------para-Nonylphenol(total)84852–15–3R--------------Phenol108–95–2R--------2,000----Triclosan3380–34–555/57NDNDNDND------Triethyl citrate (Ethylcitrate)77–93–055/57NDNDNDND------Plant- or animal-derived biochemicalsbeta-Stigmastanol19466–47–855/571.8NDE0.52ND------3-beta-Coprostanol360–68–955/57NDNDNDND------3-Methyl-1(H)-indole(Skatole)83–34–155/57NDNDNDND------beta-Sitosterol83–46–555/57NDNDNDND------Cholesterol57–88–555/57NDNDNDND------Refrigerants and propellantsTrichlorofluoromethane(CFC-11)75–69–471/712.82.8E0.1340.1522,000----1,1,2-Trichloro-1,2,2-trifluoroethane (CFC113)76–13–171/712.8ND.394ND200,000----Dichlorodifluoromethane (CFC-12)75–71–871/711.42.8E.05E.0831,000----

# Appendixes **73 Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protection Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** SolventsPerchloroethene (PCE)127–18–471/7139378.020.56154(1)2Trichloroethene (TCE)79–01–671/71272364.6353(1)1cis-1,2-Dichloroethene156–59–271/7120182.42.1970----1,1,1-Trichloroethane71–55–671/7120145.071.12200----1,1-Dichloroethane(CCL)75–34–371/71138.55.11.347------1,1-Dichloroethene75–35–471/71118.57.02.12971(1)--trans-1,2-Dichloroethene156–60–571/714.25.6.18.15100----Carbon tetrachloride(Tetrachloromethane)56–23–571/712.88.5.52.551--Tetrahydrofuran109–99–971/712.8ND278.9ND------Acetone67–64–156/561.8ND68.4ND6,000----1,2-Dichloroethane107–06–271/711.4NDE.084ND5----Methyl ethyl ketone(MEK)78–93–371/711.4ND1,142ND4,0001--Chlorobenzene108–90–761/61ND1.6NDE.014100----Methyl isobutyl ketone(4-Methyl-2-pentanone)108–10–171/71ND1.4ND3.3------1,1,1,2-Tetrachloroethane630–20–671/71NDNDNDND70----1,1,2,2-Tetrachloroethane (CCL)79–34–571/71NDNDNDND.3----1,1,2-Trichloroethane79–00–571/71NDNDNDND5----Diethyl ether(1,1’-Oxybisethane)60–29–771/71NDNDNDND1,000----

# 74 **Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater Appendix 3.** Summary statistics and human-health benchmarks for anthropogenic organic compounds analyzed in source- and finished-water samples collected during June2004–September 2005 (use groups obtained from Carter and others, 2007).—Continued[Compounds within each primary-use category are listed in order from highest to lowest source-water detection frequency. Human-health benchmarks inboldtype are Maximum Contaminant Levels (MCLs);CASRN, Chemical Abstracts Service Registry Number®; μg/L, micrograms per liter; BQ, benchmark quotient; >, greater than; --, none; E, estimated value; ND, not detected; CCL, U.S. Environmental Protec-tion Agency’s Contaminant Candidate List 2 (U.S. Environmental Protection Agency, 2005); MCPA, 2-methyl-4-chlorophenoxyacetic acid; MCPB, 4-(2-methyl-4-chlorophenoxy) butyric acid; R, compoundremoved from the dataset; HBSL, Health-Based Screening Level]**Compound CASRN** **1 Number of** **samples Detection frequency** **(percent) Maximum concentration** **(μg/L) Human-health** **benchmark (μg/L)** **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** **Source water** **Finished water** Solvents—Continued1,2,4-Trichlorobenzene120–82–171/71NDNDNDND70----1,2-Dichlorobenzene95–50–171/71NDNDNDND600----1,3-Dichlorobenzene541–73–171/71NDNDNDND600----2-Chlorotoluene95–49–871/71NDNDNDND100----2-Hexanone591–78–671/71NDNDNDND------4-Chlorotoluene106–43–471/71NDNDNDND100----Bromobenzene (CCL)108–86–171/71NDNDNDND------Chloroethane75–00–371/71NDNDNDND------Dibromomethane74–95–371/71NDNDNDND------Hexachloroethane67–72–171/71NDNDNDND.7----Isophorone78–59–1R--------100----Methyl acetate79–20–915/15NDNDNDND------Methylene chloride(Dichloromethane)75–09–256/56NDNDNDND5----n-Propylbenzene103–65–171/71NDNDNDND------p-Cresol106–44–555/57NDNDNDND------1This report contains CASRNs, which is a Registered Trademark of the American Chemical Society. The Chemical Abstracts Service (CAS) recommends the verification of the CASRNs through CAS ClientServicesSM.2The U.S. Environmental Protection Agency’s MCL of 80 μg/L is for the sum of the concentrations of four trihalomethanes.3HBSL 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).4The 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 542–75–6.5The concentrations fromm- andp-xylene ando-xylene may be compared to the MCL (10,000 μg/L) for mixed xylenes, CASRN 1330–20–7.6U.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.7Concentrations ofcis-permethrin may be compared to the HBSL range (4–400 μg/L) for permethrin, Chemical Abstract Service Registry Number 52645–53–1.

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# .Hopple and others**—Anthropogenic Organic Compounds in Source Water of Selected Community Water Systems that Use Groundwater, 2002–05—**SIR 2009–5200



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