science for a changing world

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM, 

NATIONAL SYNTHESIS ON VOLATILE ORGANIC COMPOUNDS

Occurrence and Distribution of Methyl 

terf-Butyl Ether and Other Volatile 

Organic Compounds in Drinking Water in 

the Northeast and Mid-Atlantic Regions 

of the United States, 1993-98

Water-Resources Investigations Report 00-4228

Prepared in cooperation with the U.S. Environmental Protection Agency, 

Office of Ground Water and Drinking Water

U.S. Department of the Interior 

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

U.S. Geological Survey

Occurrence and Distribution of Methyl 

feit-Butyl Ether and Other Volatile 

Organic Compounds in Drinking Water in 

the Northeast and Mid-Atlantic Regions 

of the United States, 1993-98

By Stephen J. Grady and George D. Casey 

Water-Resources Investigations Report 00-4228

Prepared in cooperation with the U.S. Environmental Protection Agency, 

Office of Ground Water & Drinking Water
U.S. Department of the Interior

GALE A. NORTON, Secretary

U.S. Geological Survey

CHARLES G. GROAT, Director

The use of firm, trade, and brand names in this report is for identification purposes 

only and does not constitute endorsement by the U.S. Government.

East Hartford, Connecticut: 2001

For additional information write to:

District Chief 

U.S. Geological Survey 

101 Pitkin Street 

East Hartford, CT 06108

Copies of this report can be purchased from:

U.S. Geological Survey 

Branch of Information Services 

Building 810

Box 25286, Federal Center 

Denver, CO 80225-0286
FOREWORD

The U.S. Geological Survey (USGS) is 

committed to serve the Nation with accurate and 

timely scientific information that helps enhance and 

protect the overall quality of life, and facilitates effective management of water, biological, energy, and 

mineral resources. Information on the quality of the 

Nation's water resources is of critical interest to the 

USGS because it is so integrally linked to the longterm availability of water that is clean and safe for 

drinking and recreation and that is suitable for 

industry, irrigation, and habitat for fish and wildlife. 

Escalating population growth and increasing demands 

for the multiple water uses make water availability, 

now measured in terms of quantity and quality, even 

more critical to the long-term sustainability of our 

communities and ecosystems.

The USGS implemented the National WaterQuality Assessment (NAWQA) Program to support 

national, regional, and local information needs and 

decisions related to water-quality management and 

policy. Shaped by and coordinated with ongoing 

efforts of other Federal, State, and local agencies, the 

NAWQA Program is designed to answer: What is the 

condition of our Nation's streams and ground water? 

How are the conditions changing over time? How do 

natural features and human activities affect the quality 

of streams and ground water, and where are those 

effects most pronounced? By combining information 

on water chemistry, physical characteristics, stream 

habitat, and aquatic life, the NAWQA Program aims to 

provide science-based insights for current and 

emerging water issues. NAWQA results can 

contribute to informed decisions that result in practical 

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

Since 1991, the NAWQA Program has implemented interdisciplinary assessments in more than 50 

of the Nation's most important river basins and aquifers, referred to as Study Units. Collectively, these 

Study Units account for more than 60 percent of the 

overall water use and population served by public 

water supply, and are representative of the Nation's 

major hydrologic landscapes, priority ecological 

resources, and agricultural, urban, and natural sources 

of contamination.

Each assessment is guided by a nationally 

consistent study design and methods of sampling and 

analysis. The assessments thereby build local knowledge about water-quality issues and trends in a particular stream or aquifer while providing an understanding of how and why water quality varies 

regionally and nationally. The consistent, multi-scale 

approach helps to determine if certain types of waterquality issues are isolated or pervasive, and allows 

direct comparisons of how human activities and 

natural processes affect water quality and ecological 

health in the Nation's diverse geographic and environmental settings. Comprehensive assessments on pesticides, nutrients, volatile organic compounds, trace 

metals, and aquatic ecology are developed at the 

national scale through comparative analysis of tH 

Study-Unit findings.

The USGS places high value on the communication and dissemination of credible, timely, and relevant science so that the most recent and available 

knowledge about water resources can be applied in 

management and policy decisions. We hope this 

NAWQA publication will provide you the needed 

insights and information to meet your needs, anc1 

thereby foster increased awareness and involvement in 

the protection and restoration of our Nation's waters.

The NAWQA Program recognizes that a 

national assessment by a single program cannot 

address all water-resource issues of interest. External 

coordination at all levels is critical for a fully integrated understanding of watersheds and for costeffective management, regulation, and conservation of 

our Nation's water resources. The Program, therefore, 

depends extensively on the advice, cooperation, and 

information from other Federal, State, interstate, 

Tribal, and local agencies, non-government organizations, industry, academia, and other stakeholder 

groups. The assistance and suggestions of all are 

greatly appreciated.

Robert M. Hirsch 

Associate Director for Water

Foreword III

CONTENTS

Abstract ...................................................................................................................................................................^ 1

Introduction ................................. ........ ............. .........._ 2

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

Previous Investigations ............................................................................................................................................... 4

Acknowledgments ...................................................................................................................................................... 1

Approach .....................................................................................................................................................................^ 7

Study Design ............................................................................................................................................................... 1

Data Inventory ............................................................................................................................................................ 11

Data Documentation ................................................................................................................................................... 17

Data Analysis .............................................................................................................................................................. 19

Occurrence and Distribution of VOCs in Drinking Water ................................................................................................... 20

Disinfectant By-Products ............................................................................................................................................ 33

MTBE and Other Gasoline Components .................................................................................................................... 37

Solvents ..............................................................................._ 43

Other VOCs ...........................................................................^^ 47

Potential Human Exposure to VOCs in Drinking Water ...................................................................................................... 49

Actual Population Served by Randomly Selected CWSs ........................................................................................... 49

Estimated Population Served by All CWSs ............................................................................................................... 53

Summary and Conclusions ................................................................................................................................................... 58

References Cited ..............................................................................._ 61

Appendixes..............................................................................._ 65

Appendix 1. Volatile organic compounds included in analyses of drinking water for randomly selected

community water systems in the study area, 1993-98 .................................................................................. 67

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly

selected community water systems in the study area compared by State, 1993-98 ..................................... 70

Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds

included in analyses of drinking water for randomly selected community water systems in the study

area compared by reporting levels, 1993-98 ................................................................................................ 85

Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community

water systems in the study area, 1993-98 ..................................................................................................... 108

Contends
FIGURES

1-2. Maps showing:

1. The 12-State study area, Northeast and Mid-Atlantic regions ...................................................................... 5

2. Drinking-water sources of water for randomly selected community water systems in the study

area showing (A) ground-water sources and (B) surface-water sources ....................................................... 12

3-4. Graphs showing:

3. Cumulative distribution of concentrations of volatile organic compounds detected in drinking-wa*er

samples from randomly selected community water systems in the study area, 1993-98 .............................. 23

4. Frequency of detection of volatile organic compounds at concentrations equal to or exceeding 

1.0 microgram per liter in drinking water from randomly selected community water systems in 

the study area for (A) 20 volatile organic compounds with detection frequencies greater than 

1 percent and (B) 34 volatile organic compounds with detection frequencies less than 1 percent ............... 27

5-6. Maps showing:

5. Drinking-water sources for randomly selected community water systems in the study area, 

showing systems with analytical data and systems with reported detectable concentrations 

of any volatile organic compound, in relation to urban land use ................................................................... 30

6. Drinking-water sources for randomly selected community water systems in the study area, 

showing systems with analytical data and systems with reported detectable concentrations 

of any non-trihalomethane volatile organic compound, in relation to urban land use .................................. 31

7-9. Graphs showing:

7. Frequency of co-occurrence of volatile organic compounds in drinking-water samples from randmly

selected community water systems in the study area .................................................................................... 33

8. Distribution of median total trihalomethane concentrations in drinking water from randomly selected

community water systems in study area compared by source of water ......................................................... 35

9. Frequency of detection of methyl tert-butyl ether at or above 1.0 microgram per liter in drinking water

from randomly selected community water systems in 10 Northeast and Mid-Atlantic States, 1993-98 ...... 37

10. Map showing drinking-water sources for randomly selected community water systems in the study area, 

showing systems with analytical data and those systems with reported detectable concentrations for 

methyl tert-butyl, in relation to areas where oxygenated and (or) reformulated gasoline is currently 

or was formerly used .............................................................................................................................................. 39

11-12. Graphs showing:

11. Comparison of cumulative distributions of median methyl tert-butyl ether concentrations in drinking

water for randomly selected community water systems to selected public water systems in the study area 40

12. Comparison of methyl ter/-butyl ether concentrations to the sum of the concentrations of benzene, 

ethylbenzene, toluene, and xylenes in drinking-water samples from randomly selected community 

water systems in the study area ..................................................................................................................... 41

13. Map showing drinking-water sources for randomly selected community water systems in the study area, 

showing systems with analytical data and systems with reported detectable concentrations of 

any solvents, in relation to urban land use ............................................................................................................. 44

14. Graph showing frequency of detection of solvents at or above 1.0 microgram per liter in drinking wate"

from randomly selected community water systems in the study area, 1993-98 ..................................................... 45

15. Map showing drinking-water sources for randomly selected community water systems in the study are?, 

showing systems with analytical data and systems with reported detectable concentrations of 

any fumigants, in relation to urban land use .......................................................................................................... 48

TABLES

1. Distribution of community water systems in the study area on December 1, 1997 by State,

principal source of water, and population served .................................................................................................. 8

2. Targeted distribution of community water systems inventoried by State, principal source of water,

and population served ............................................................................................................................................ 9

3. Actual distribution of randomly selected community water systems inventoried by State, source of

water, and population served ................................................................................................................................. 10

4. Population served by community water systems in the study area ....................................................................... 11

5. Availability of data on volatile organic compounds in drinking water for the study area, 1978-98 ..................... 14

VI Contents
TABLES Continued

6. Period of record for data compiled on volatile organic compounds and methyl tert-butyl ether in

drinking water from randomly selected community water systems in the study area ........................................... 16

7. Volatile organic compounds detected in drinking water from randomly selected community water

systems in the study area, 1993-98 ........................................................................................................................ 21

8. Volatile organic compounds that equaled or exceeded regulated or recommended concentrations in

drinking water from randomly selected community water systems in the study area, 1993-98 ........................... 22

9. Frequency of detection of volatile organic compounds at any reporting level in drinking water from

randomly selected community water systems in the study area, 1993-98 ............................................................. 25

10. Volatile organic compounds undetected in drinking water from randomly selected community water

systems in the study area, 1993-98 ........................................................................................................................ 26

11. Randomly selected community water systems in the study area reporting concentrations at or above 

1.0 microgram per liter of 54 selected volatile organic compounds in drinking water by State, 

source of water, and population served, 1993-98 .................................................................................................. 28

12. Comparison of the frequency of detection of volatile organic compounds at concentrations at or above 

1.0 microgram per liter in drinking water from randomly selected community systems in the study 

area by source of water and size, 1993-98 ............................................................................................................. 28

13. Comparison between average population density and the frequency of detection of volatile organic 

compounds at concentrations at or above 1.0 microgram per liter in drinking water in the 

study area, 1993-98 ................................................................................................................................................ 29

14. Relations between the occurrence of volatile organic compounds at or above 1.0 microgram per liter 

and at concentrations that equal or exceed a drinking-water regulation or recommendation in drinking 

water from randomly selected community water systems in the study area and source of water, size 

of system, and land use at sources ......................................................................................................................... 32

15. Frequency of detection and median concentrations of trihalomethanes in drinking water from randomly

selected community water systems in the study area compared by source of water ............................................. 36

16. Co-occurrence of trihalomethane compounds in drinking water from randomly selected community water

systems in the study area ....................................................................................................................................... 36

17. Co-occurrence of gasoline components in drinking water from randomly selected community water

systems in the study area ....................................................................................................................................... 41

18. Co-occurrence of selected solvents in drinking water from randomly selected community water

systems in the study area ....................................................................................................................................... 46

19. Population served by randomly selected community water systems in the study area with detections

of 64 volatile organic compounds in drinking water, 1993-98 .............................................................................. 50

20. Population served by randomly selected community water systems reporting detectable concentrations

of volatile organic compounds in drinking water in the study area, 1993-98 ....................................................... 52

21. Estimated number of community water systems and population in the study area that may have had 

detectable concentrations of volatile organic compounds in drinking water during 1993-98 based on 

extrapolation from randomly selected community water systems ........................................................................ 55

22. Estimated number of community water systems that may have had detectable concentrations of volatile 

organic compounds in drinking water during 1993-98 based on extrapolation of frequency of 

detection for each State .......................................................................................................................................... 56

23. Estimated number of people served by community water systems that may have had detectable 

concentrations of volatile organic compounds in drinking water during 1993-98 based on 

extrapolation of population served by random systems with detections for each State ........................................ 57

Contents VII
CONVERSION FACTORS AND ABBREVIATIONS

Multiply By To obtain

Length

inch (in.)

inch (in.)

foot (ft)

mile (mi)

square mile (mi2)

square mile (mi2)

2.54

25.4

0.3048

1.609

Area

259.0

2.590

centimeter

millimeter

meter

kilometer

hectare

square kilometer

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

°F = (1.8x°C) + 32 

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

°C = (°F-32)71.8 

Concentrations of chemical constituents in water are given in micrograms per liter (^ig/L).

VIII Contents
Occurrence and Distribution of Methyl fert-Butyl Ether 

and Other Volatile Organic Compounds in Drinking 

Water in the Northeast and Mid-Atlantic Regions 

of the United States, 1993-98

By Stephen J. Grady and George D. Casey

ABSTRACT

Data on volatile organic compounds 

(VOCs) in drinking water supplied by 2,110 

randomly selected community water systems 

(CWSs) in 12 Northeast and Mid-Atlantic States 

indicate 64 VOC analytes were detected at least 

once during 1993-98. Selection of the 2,110 CWSs 

inventoried for this study targeted 20 percent of 

the 10,479 active CWSs in the region and represented a random subset of the total distribution by 

State, source of water, and size of system. The data 

include 21,635 analyses of drinking water 

collected for compliance monitoring under the 

Safe Drinking Water Act; the data mostly represent finished drinking water collected at the pointof-entry to, or at more distal locations within, each 

CWS's distribution system following any watertreatment processes. VOC detections were more 

common in drinking water supplied by large 

systems (serving more than 3,300 people) that tap 

surface-water sources or both surface- and groundwater sources than in small systems supplied 

exclusively by ground-water sources.

Trihalomethane (THM) compounds, which 

are potentially formed during the process of disinfecting drinking water with chlorine, were 

detected in 45 percent of the randomly selected 

CWSs. Chloroform was the most frequently 

detected THM, reported in 39 percent of the 

CWSs. The gasoline additive methyl tert-butyl 

ether (MTBE) was the most frequently detected 

VOC in drinking water after the THMs. MTBE 

was detected in 8.9 percent of the 1,194 randomly 

selected CWSs that analyzed samples for MTBE

at any reporting level, and it was detected in 7.8 

percent of the 1,074 CWSs that provided MTBE 

data at the 1.0-jig/L (microgram per liter) 

reporting level. As with other VOCs reported in 

drinking water, most MTBE concentrations were 

less than 5.0 jig/L, and less than 1 percent of 

CWSs reported MTBE concentrations at or above 

the 20.0-jig/L lower limit recommended t:y the 

U.S. Environmental Protection Agency's 

Drinking-Water Advisory.

The frequency of MTBE detections in 

drinking water is significantly related to HghMTBE-use patterns. Detections are five times 

more likely in areas where MTBE is or has been 

used in gasoline at greater than 5 percent by 

volume as part of the oxygenated or reformulated 

(OXY/RFG) fuels program. Detection frequencies 

of the individual gasoline compounds (benzene, 

toluene, ethylbenzene, and xylenes (ETEY)) were 

mostly less than 3 percent of the randomly selected 

CWSs, but collectively, BTEX compounds were 

detected in 8.4 percent of CWSs. BTEX concentrations also were low and just three drinkingwater samples contained BTEX at concertrations 

exceeding 20 Jig/L. Co-occurrence of MTBE and 

BTEX was rare, and only 0.8 percent of CWSs 

reported simultaneous detections of MTBE and 

BTEX compounds. Low concentrations and cooccurrence of MTBE and BTEX indicate most 

gasoline contaminants in drinking water probably 

represent nonpoint sources.

Solvents were frequently detected in 

drinking water in the 12-State area. One or more of 

27 individual solvent VOCs were detected at any 

reporting level in 3,080 drinking-water samples

Abstract
from 304 randomly selected CWSs (14 percent) 

and in 206 CWSs (9.8 percent) at concentrations at 

or above 1.0 |Ug/L. High co-occurrence among 

solvents probably reflects common sources and 

the presence of transformation by-products. Other 

VOCs were relatively rarely detected in drinking 

water in the 12-State area. Six percent (127) of the 

2,110 randomly selected CWSs reported concentrations of 16 VOCs at or above drinking-water 

criteria. The 127 CWSs collectively serve 2.6 

million people.

The occurrence of VOCs in drinking water 

was significantly associated (p<0.0001) with highpopulation-density urban areas. New Jersey, 

Massachusetts, and Rhode Island, States with 

substantial urbanization and high population 

density, had the highest frequency of VOC detections among the 12 States. More than two-thirds of 

the randomly selected CWSs in New Jersey 

reported detecting VOC concentrations in 

drinking water at or above 1.0 |Ug/L.

Ninety-two percent of the 9.6 million people 

served by the 2,110 randomly selected CWSs 

inventoried for this study, or 8.8 million people, 

get their drinking water from a CWSs that has 

reported at least one detection of a VOC during 

1993-98. Projections of the total number of 

systems that may have experienced detections of 

VOCs during this time period indicate 4,700 

CWSs may have been similarly affected. Estimates of the number of people potentially exposed 

to VOCs in drinking water in the 12-State area 

during this time period range from 52 to 54 

million. Thirty-four percent of the population 

served by randomly selected CWSs with data for 

MTBE may have been exposed to the gasoline 

additive in their drinking water. Extrapolation of 

the frequency of detection and the percentage of 

population potentially exposed to MTBE from the 

random sample to all CWSs for the 12-State area 

provides estimates of about 900 CWSs and 17 to 

20 million people.

INTRODUCTION

Methyl terf-butyl ether (MTBE) is a chemical 

compound that is added to gasoline in some areas of the

United States to control air pollution and to enhance the 

octane level. With the phaseout of tetraethyl lead from 

gasoline in the 1970s, MTBE was blended in some 

conventional gasoline at low concentrations (about 1 to 

7 percent by volume) to enhance octane ratings and 

improve combustion. The Clean Air Act Amendments 

(CAAA) of 1990 mandated use of oxygenates (oxygencontaining compounds) in areas where atmospheric 

concentrations of ozone in summer and carbon 

monoxide in winter exceed established air-quality standards. Although the CAAA did not stipulate which 

oxygenate must be added to gasoline, MTBE is the 

primary oxygenate used, especially in the Northeast 

and Mid-Atlantic States. When MTBE is usecf in 

oxygenated gasoline (OXY), the concentration of 

MTBE is approximately 15 percent by volume.

Several urban areas presently or formerly 

included in the wintertime OXY fuel program, which 

began in November 1992, are in the Northeast or MidAtlantic States. In 1995, use of MTBE expanded in 

parts of the Nation, including much of the Northeast 

and Mid-Atlantic regions, with the introduction of 

reformulated gasoline (RFG). RFG has about 11 

percent MTBE by volume and is now or was formerly 

used year-round in all or some parts of 11 of the 12 

States in this study. Annual domestic production of 

MTBE has increased substantially, from 1.65 million 

barrels in 1980 to 75 million barrels in 1998 (U.S. 

Department of Energy, 1999), and nearly doubled over 

the 6-year period (1993-98) examined for this study. 

MTBE currently is used as an oxygenate in about onethird of all gasoline sold in the United States.

MTBE is a volatile organic compound (VOC), a 

group of natural and manmade chemicals that are typically characterized by high vapor pressures, high solubilities in water, and low octanol-water partition 

coefficients. A variety of chemicals including some 

hydrocarbons, halocarbons, aldehydes, ketone.s, alcohols, acids, ethers, and methyl-sulfur compounds can 

be classified as VOCs. These chemicals are used and 

(or) produced in the manufacture of paints, adhesives, 

petroleum products, pharmaceuticals, and refrigerants. 

VOCs are the principal or active components of products commonly used in urban settings, such as fuels, 

solvents, hydraulic fluids, paint, and dry cleaning 

agents and the active and (or) inert components of 

products used in agricultural setting, such as pesticides 

(particularly fumigants).

Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Contamination of drinking-water supplies by 

VOCs is a human health concern because many 

compounds are toxic and are known or suspected 

human carcinogens (U.S. Environmental Protection 

Agency, 1996). The U.S. Environmental Protection 

Agency (USEPA) has established maximum contaminant levels (MCLs) for 21 VOCs (plus two fumigants, 

ethylene dibromide (EDB) and dibromochloropropane 

(DBCP), classified by the USEPA as "synthetic organic 

compounds;" see appendix 1) that are currently regulated in public drinking water under the Safe Drinking 

Water Act (SDWA). Most public drinking water also is 

monitored for 21 unregulated VOCs as per SDWA 

requirements. Monitoring for an additional 14 VOCs 

can be required of public water systems (PWSs) at the 

discretion of individual States.

MTBE may be released into the environment 

from point sources, such as leaks or spills, that may 

take place during the refinement, distribution, storage, 

and use of gasoline; some of these leaks or spills have 

resulted in the loss of domestic and public water 

supplies (Office of Science and Technology Policy, 

1997; Hitzig and others, 1998). It has been estimated 

that 9 million barrels of gasoline, or roughly the 

volume of one supertanker, are released into the environment each year in the United States (Alliance for 

Proper Gasoline Handling, 1999). Furthermore, the 

release of MTBE to the atmosphere and the hydrosphere from nonpoint sources, such as automobile 

emissions and evaporative losses, may result in low 

concentrations of MTBE in water in urban areas 

(Pankow and others, 1997; Baehr and others, 1999). 

The physical and chemical properties of MTBE its 

high solubility, low sorption, and limited anaerobic 

biodegradation together with its large-scale production and use have made MTBE one of the most 

frequently detected contaminants in ground water in 

recent National assessments (Squillace and others, 

1996; Zogorski and others, 1998; Moran and others, 

1999).

The presence of MTBE in drinking water is a 

potential human health concern, and at low concentrations, its presence may adversely affect the taste and 

odor of drinking water, causing it to be unpotable 

(Young and others, 1996; Malcome Pirnie, Inc., 1998; 

California Department of Health Services, 1999). 

USEPA has issued a drinking-water advisory that 

recommends a range of 20 to 40 fig/L as a limit to 

address taste and odor concerns (U.S. Environmental 

Protection Agency, 1997). The USEPA advisory

concentration range for MTBE also is intended to 

provide a safety margin for potential carcinogenic 

effects and to provide a large margin of safety for 

noncancerous effects (U.S. Environmental Protection 

Agency, 1997). The USEPA has tentatively classified 

MTBE as a Group C, or possible human carcinogen 

(U.S. Environmental Protection Agency, 1996).

Although analysis of drinking-water samples for 

MTBE is not presently required under the SDWA, 

some States and (or) public drinking-water suppliers 

have included MTBE in chemical analyses of drinkingwater samples in recent years. Despite this, the report 

of the Interagency Assessment of Oxygenated Fuels 

was unable to adequately describe the occurrence of 

MTBE in the Nation's drinking water from the limited 

data available in 1997 (Zogorski and others, 1997) and 

recommended that additional data on MTBE in 

drinking water be collected. The USEPA also h as noted 

that "based on limited monitoring and occurrence data, 

a potential for exposure of......human populations to

oxygenates exists" (U.S. Environmental Protection 

Agency, 1998a, p. 19), and that obtaining date from 

public water suppliers would help determine the "prevalence and level of potential exposures." Monitoring 

for MTBE will be required for some but not all PWSs 

beginning in 2001 (U.S. Environmental Protection 

Agency, 1999a).

Questions and concerns have been raised about 

MTBE and VOCs in drinking water. Some of these 

include:

 The widespread use of the gasoline additive 

MTBE has contaminated public drinking water, but 

does the occurrence of MTBE in drinking water change 

substantially in space and time and does it refect 

different MTBE-use patterns?

 What other VOCs have been detected in 

drinking water? How frequently have regulated VOCs 

been detected at concentrations below MCLs? How 

frequently have unregulated VOCs been detected in 

drinking water at any concentration? How often does 

MTBE co-occur with other VOCs? Also, if MTBE and 

other VOCs occur widely in drinking water, can 

estimates be made of how many people may have been 

exposed to VOCs through consumption of affected 

drinking water?

Introduction
 Does the frequency of VOC detections differ 

among States? Are VOCs detected more frequently in 

drinking water obtained from ground-water sources 

than that obtained from surface-water sources? Does 

the type and frequency of VOCs detected differ 

substantially between source waters and finished 

waters? If so, can the occurrence of VOCs in drinking 

water be related to the size of public water systems and 

level of water treatment they provide?

In an effort to provide answers to these questions, the U.S. Geological Survey (USGS), in cooperation with the USEPA, conducted an assessment of the 

occurrence and distribution of MTBE and other VOCs 

in public drinking water in the Northeast and MidAtlantic regions of the United States during 1993-98. 

This report describes the effort to compile, evaluate, 

and analyze existing information on the quality of 

public drinking water collected by water suppliers and 

State or local health or environmental agencies.

Purpose and Scope

This report describes the occurrence and distribution of MTBE and other VOCs in public drinking 

water supplied by a representative sample of the CWSs 

in a 12-State area of the Northeast and Mid-Atlantic 

regions of the United States (fig. 1) referred to as the 

study area. CWSs are PWSs that provide water year 

round to at least 25 people or have a minimum of 15 

residential service connections. This report provides 

information on the frequency of detection, concentration, and distribution of MTBE and other VOCs in 

drinking water, and evaluates the extent of possible 

human exposure within the study area to these 

compounds in drinking water. Information on the 

occurrence and distribution of MTBE in drinking water 

will be used (1) by the USEPA to make a determination 

whether to proceed with developing a national standard 

for MTBE in support of the new risk-based contaminant selection and regulation process under the SDWA 

Amendments of 1996 (Sakata and Osinski, 1999), and 

(2) by the USGS to better characterize the quality of the 

Nation's water resources in general (Gilliom and 

others, 1995) and specifically with respect to VOCs in 

ground water from major aquifers (Lapham and 

Tadayon, 1996).

The report summarizes information on the 

quality of drinking water from 2,110 randomly selected 

CWSs in the study area. Water-quality data, including 

more than 21,000 chemical analyses for VOCs in 

drinking-water samples collected from 1993 to 1998 in 

compliance with SDWA monitoring requirements,

were compiled and analyzed for this study. The study 

area (fig. 1) includes the six New England States 

(Connecticut, Maine, Massachusetts, New Hampshire, 

Rhode Island, and Vermont), three other northeastern 

States (New Jersey, New York, and Pennsylvania), 

three Mid-Atlantic States (Delaware, Maryland, and 

Virginia), and Washington, D.C.

Previous Investigations

No previous studies specifically have focused on 

the occurrence and distribution of MTBE, or other 

VOCs in general, in public drinking water across the 

study area, but a few national studies of VOC? in 

drinking water or ambient ground water included data 

for at least some of the 12 Northeast and Mid-Atlantic 

States. Also, a few recent studies have focused on 

MTBE or other VOCs in ground water, surface water, 

and (or) drinking water for specific States, parts of 

States, or groups of States in the region. These studies 

are identified and briefly summarized below.

A review of the occurrence and distribution of 

VOCs in drinking water by Westrick and others (1984) 

reported that 23 VOCs were detected in finished 

drinking water supplied by nearly one-fourth (230) of 

945 water systems throughout the United Stages 

sampled during 1981 and 1982. The "ground-water 

supply survey" included 34 VOC analytes but not 

MTBE. Overall, detection frequencies ranged from 

about 17 percent of samples from small, randomly 

selected PWSs, to 37 percent of samples from large 

systems selected for sampling because they had been 

identified as "problem systems." The most frequently 

detected VOCs were four trihalomethanes 

(THMs) chloroform, bromodichloromethane, chlorodibromomethane, and bromoform present in 45, 

43, 39, and 22 percent of the systems sampled, respectively. Trihalomethanes, which are halogenateH organic 

compounds that may form during the process of disinfecting drinking water with chlorine, were detected 

more often from large systems (serving more than 

10,000 people) than from small systems that were less 

likely to chlorinate their source water. After the trihalomethanes, four commonly used solvents tetrachloroethylene, trichloroethylene, 1,1,1-trichloroethane, 

and 1,1-dichloroethane were the next most 

frequently detected compounds, present in 4 to 7 

percent of the systems sampled. Fifty-three percent of 

the samples with VOC detections contained more than 

one VOC. The relatively high detection frequencies, 

the age of the data, and limited analytical coverage 

point to the need for a current and comprehensive 

picture of VOCs in public drinking water.

Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
80° 78° 76° 74° 72° 70° 68° 66° 64°

48C

46C

44°

42°

40°

38°

NEW HAMPSHIRE 

VERMONT

MASSACHUSETTS

RHODE ISLANE 

CONNECTICUT

DELAWARE

MARYLAND

Base from U.S. Department of Commerce, digital data 1:100,000,1993 

Albers projection

100 2CO MILES

0 100 200 KILOMETERS

Figure 1. The 12-State study area, Northeast and Mid-Atlantic regions (from Grady and Casey, 1999, fig. 1).

Introduction 5
In an effort to obtain current information on the 

occurrence of contaminants in public drinking water 

regulated under the SDWA and to refine the basis for 

monitoring these contaminants, the USEPA has 

reviewed a variety of State and national databases on 

drinking-water quality (U.S. Environmental Protection 

Agency, 1999b). SDWA compliance monitoring data, 

including more than 10 million analyses of drinking 

water sampled during 1982-98 for nearly 26,000 PWSs 

from 12 States (including two Massachusetts and 

New Jersey in the present study), were reviewed 

(U.S. Environmental Protection Agency, 1999b, p. 7). 

Data for 64 regulated contaminants, including 21 

VOCs, were compiled and analyzed. Additional data 

from the USEPA's Unregulated Contaminant Monitoring Information System national database on unregulated VOCs, including more than 12,000 analyses for 

MTBE from 4,152 PWSs, also were reviewed (U.S. 

Environmental Protection Agency, 1999b, p. A14-15). 

Generally, VOCs were reported in drinking water by 

about 30 percent of the PWSs inventoried. Seven of the 

VOCs (ethylbenzene, a's-l,2-dichloroethane, 1,1,1- 

trichloroethane, tetrachloroethylene, trichloroethylene, 

vinyl chloride, and xylenes) were reportedly detected 

in drinking water from all States surveyed. Collectively, VOCs were detected twice as frequently in 

surface-water supplied PWSs than in ground-water 

supplied systems, and in proportionally more of the 

larger systems than smaller systems. MTBE was 

reported in drinking water by 8.3 percent of the 

surface-water systems and 5. 4 percent of the groundwater systems (U.S. Environmental Protection Agency, 

1999b, p. A14-15).

A national study of the occurrence of VOCs in 

ambient ground water (Squillace, 1999; Squillace and 

others, 1999) reported that VOCs were most strongly 

associated with urban areas. Squillace and others 

(1999) reported 47 percent of the wells sampled in 

urban areas contained at least one VOC, whereas only 

14 percent of the wells in rural areas contained VOCs. 

Chloroform (also called trichloromethane) was the 

most frequently detected VOC in both urban and rural 

areas, and MTBE was the second most frequently 

detected compound. The use of MTBE in OXY or RFG 

areas was reported to result in a 4- to 6-fold increase in 

MTBE detection frequency even when controlling for 

differences in land use (Squillace, 1999). Although 

VOC concentrations were generally small (56 percent 

were less than 1 |ig/L), it was estimated that 42 million 

people use ground water for drinking water in areas

where at least one VOC may occur (Squillace and 

others, 1999).

Detections of MTBE and other VOCs h ave been 

reported previously in ambient ground water and 

surface water in several eastern States (Hanchar and 

Grady, 1994; Grady, 1997a, b; Lindsey and others, 

1997; Mullaney and Grady, 1997; Stackelber^ and 

others, 1997; Terracciano and O'Brien, 1997; Zogorski 

and others, 1997; Baehr and Zapecza, 1998; Grady and 

Mullaney, 1998; Baehr and others, 1999). In several 

earlier studies, MTBE and other VOCs also have been 

reported in some private or public drinking-water 

supplies (Grady, 1997a, b; Lindsey and others, 1997; 

Zogorski and others, 1997; Lince and others, 1998) in 

northeastern States (Connecticut, Massachusetts, New 

Jersey, New York, Pennsylvania, and Rhode Island). In 

1998, the State of Maine conducted a statewide, statistically based, drinking-water sampling program for 

MTBE and other gasoline compounds in 951 randomly 

selected household wells or other household water 

supplies and 793 nontransient public water supplies 

(State of Maine, 1998). MTBE was detected (at a 

minimum reporting level of 0.1 JJg/L) in about 16 

percent of the private and public supplies. About 1 

percent of the private household supplies cortained 

MTBE at concentrations above 35 |ig/L, which was 

extrapolated to represent about 1,400 to 5,200 household supplies statewide. The frequency of detection of 

MTBE was similarly associated with urban areas of the 

state and with areas that use RFG.

In 1999, the Northeast States for Coordinated Air 

Use Management (NESCAUM, 1999) prepared a 

State-by-State synopsis of available information on the 

occurrence of MTBE in ground water and drnking 

water for its eight member States (Connecticut, Maine, 

Massachusetts, New Hampshire, New Jersey, New 

York, Rhode Island, and Vermont). They reported that 

MTBE was first detected in ground water in some 

northeastern States during the mid-1980s, but it is now 

one of the most frequently detected organic-chemical 

contaminants in ground water in all eight States. 

Reported MTBE concentrations ranged up to 17,000 

|ig/L (NESCAUM, 1999, p. 26) but were generally less 

than 10 |ig/L; most were below the 20- to 40-^g/L 

concentration range recommended by the USEPA 

drinking water advisory (U.S. Environmental Protection Agency, 1997). The report indicated that frequent, 

low-level MTBE contamination (below 10 |ig/L) may 

represent nonpoint sources such as atmospheric deposition, small surface spills, and stormwater runoff,

Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
whereas concentrations greater than 10 Jig/L were 

more likely related to gasoline leaks and spills from 

underground storage tanks and pipelines (NESCAUM, 

1999, p. 38).

Acknowledgments

The authors wish to acknowledge the help and 

cooperation provided by State and local health and 

environmental agencies in the 12 States, without which 

this study could not have been completed. Requests for 

data on drinking-water quality, ancillary information 

on PWSs, documentation of data processing and 

storage procedures, and review of this study's findings 

were promptly and professionally furnished by staff of 

the Connecticut Department of Public Health and 

Department of Environmental Protection; Delaware 

Department of Health and Social Services, Division of 

Public Health, Office of Drinking Water, and Department of Natural Resources and Environmental Control; 

Maine Department of Human Services, Division of 

Health Engineering; Maryland Department of the Environment; Massachusetts Department of Environmental 

Protection, Division of Water Supply; New Hampshire 

Department of Environmental Services, Water Supply 

Engineering Bureau; New Jersey Department of Environmental Protection, Division of Water Resources, 

Bureau of Safe Drinking Water; New York Department 

of Health, Bureau of Public Water Supply Protection; 

Pennsylvania Department of Environmental Protection, Division of Drinking Water Management; Rhode 

Island Department of Health; Vermont Department of 

Environmental Conservation, Water Supply Division; 

and the Virginia Department of Health, Office of Water 

Programs. The authors also are grateful for the assistance and cooperation provided by Michael Osinski, 

Rachel Sakata, and Evelyn Washington of the USEPA's 

Office of Ground Water and Drinking Water. The 

authors also acknowledge and thank Michael Osinski, 

Rachel Sakata, and Diana Wong, USEPA, and Gregory 

C. Delzer, Barbara A. Korzendorfer, Paul E. Stackelberg, William G. Wilber, and John S. Zogorski, USGS, 

for their insightful reviews of this report.

APPROACH

This assessment involved four tasks (1) 

designing the study to include a large, representative 

sample of PWSs, (2) inventorying existing monitoring 

data on MTBE and other VOCs in drinking water

collected by water systems and State and local agencies 

for SDWA compliance, (3) reviewing and documenting 

the quality, completeness, and other characteristics of 

the data, and (4) analyzing and interpreting the waterquality data with available ancillary data to provide 

information on the frequency of detection, corcentration, and geographic distribution of MTBE and other 

VOCs in drinking water in the 12 States. The overall 

design and workplan for this assessment has b^en 

previously documented (Grady and Casey, 199?) and is 

not repeated here, but major elements of the design are 

described below for the reader's convenience. Additional information on the data inventory, documentation, and analysis are provided in subsequent sections.

Study Design

An extensive and representative inventory of 

available water-quality data is required to determine 

the frequency of detection and the range in concentrations of MTBE and other VOCs in public drinking 

water for each of the 12 States. The number, size, 

source, and location (by State) of PWSs selected for 

this assessment needed to reflect the actual distribution 

of PWSs in the study area; however, with more than 

43,000 PWSs in the 12-State area, a comprehensive 

review of drinking-water quality for all PWSs was not 

feasible.

PWSs obtain water from surface-water 

sources streams, rivers, lakes, and reservoirs and 

(or) ground-water sources, treat it (where required) to 

meet drinking-water standards, and deliver the finished 

water to their customers for consumption. Mo^t PWSs 

provide non-residential water supplies to schools, 

factories, and hospitals (nontransient noncommunity 

water systems (NTNCWSs)), or to campgrounds, 

motels, and restaurants (transient noncommunity water 

systems (TNCWSs)). About one-quarter of trn active 

PWSs are community water systems (CWSs) that 

provide water year round to at least 25 people or have 

a minimum of 15 residential service connections. 

Because TNCWSs, which make up the largest number 

of noncommunity systems, generally are not required 

to monitor for VOCs, and NTNCWSs generalb' are not 

the primary source of water consumed daily by their 

customers, only CWSs were included in the study. A 

stratified, random design was chosen to select participating CWSs; this design will allow information on the 

occurrence and distribution of VOCs in drinking water 

to be extrapolated to the overall population of CWSs,

Approach
as well as statistical comparisons by State, source of 

water, and size of utility.

Information on the number of CWSs in the 12- 

State study area was retrieved from the USEPA's Safe 

Drinking Water Information System (SDWIS) database (U.S. Environmental Protection Agency, 1995b) 

on December 1, 1997. This information was compiled 

for each State by principal source of water and population served (table 1). A total of 10,479 CWSs provided 

drinking water to more than 58 million people in the 12 

Northeast and Mid-Atlantic States on December 1, 

1997. Their geographic distribution reflects, to some 

extent, the size and population of each State New 

York and Pennsylvania have nearly 50 percent of the

CWSs, whereas Delaware and Rhode Island have just 

3 percent of the total. Table 1 points out that there are 

relatively few CWSs (less than 2 percent) that fall into 

the very large (>50,000 people served) category, 

whereas 66 percent are small (serve 500 or fewer 

people); about 20 percent of the CWSs are medium size 

(501-3,000 served) and 13 percent are large (7,001 to 

50,000 served). Although 80 percent of the CWSs in 

the study area use ground water as their principal 

source of water, most of these are small systems, and 

ground water provided only 20 percent of the total 

8,729 Mgal/d of water withdrawn for all public supply 

use in the 12 States during 1995 (Solley and others, 

1998).

Table 1 . Distribution of community water systems in the study area on December 1,1997 by State, principal source of 

water, and population served

[Modified from Grady and Casey, 1999. table 5. Community water systems are public and private water systems that furnish water year round for 

domestic use to at least 25 people, or that have a minimum of 15 service connections. Data from U.S. Environmental Protection Agency's Safe 

Drinking Water Information System (SDWIS) database]

Number of community water systems

Principal source 

of water

State

Connecticut

Delaware

Maine

Maryland

Massachusetts

New Hampshire

New Jersey

New York

Pennsylvania

Rhode Island

Vermont

Virginia 1

Total 

(percent)

Ground 

water

541

226

319

450

357

618

517

1,940

1,777

59

361

1,255

8,420 

(80.4)

Surface 

water

59

3

81

57

168

52

94

749

436

22

73

265

2,059 

(19.6)

More 

than 

50,000

10

3

1

7

24

2

22

29

32

5

1

18

154 

(1.5)

Population served

3,301 

to 

50,000

44

9

31

48

218

31

207

294

278

21

28

109

1,318 

(12.6)

501 

to 

3,300

55

44

93

109

80

84

132

602

508

8

84

261

2,060 

(19.6)

25 

to 

500

491

173

275

343

203

553

250

1,764

1,395

47

321

1,132

6,947 

(66.3)

Total

600

229

400

507

525

670

611

2,689

2,213

81

434

1,520

10,479 

(100)

Percentage 

of 

community 

watesystems

5.7

2.2

3.8

4.8

5.0

6.4

5.8

25.7

21.1

0.8

4.1

14.5

100

Includes District of Columbia.

Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Because a relatively large and representative 

sample was needed, 2,110 CWSs or about 20 percent of 

all CWSs in the study area, were included in the 

targeted distribution of water systems inventoried. The 

targeted distribution was based on the geographic 

distribution of systems by State, source of water, and 

population served. The stratified random design (table 

2) distributed the 2,110 CWSs among the 12 States in 

direct proportion to their actual distribution (see table 

1); for example, table 1 shows that 5.7 percent of all 

CWSs in the study area are in Connecticut and consequently 120 (5.7 percent) of the 2,110 targeted CWSs 

were allocated to Connecticut in the study design. The 

number of CWSs needed in Rhode Island (16), 

however, was augmented by 14 to obtain a total of 30 

systems from that State to have sufficient numbers for 

valid statistical analysis of the data; the extra 14 CWSs 

were allocated by source and size in the same proportions as the original 16 systems.

Retrievals were made from the SDWIS database 

for all active CWSs in the 12-State study area as of 

December 1, 1997 and the data were imported into a

Microsoft Access© database. The data retrieved from 

SDWIS identified the CWS's public water system 

identification (PWSID) number, system name, address, 

ownership type, population served, source waters, and 

treatment facilities. Lists of the CWSs were organized 

by State, source of water, and population-served categories, and a random number generator was used to 

assign a selection sequence number to each CV rS. Lists 

of the required number of randomly selected CWSs 

plus an additional number (typically 20 percent) of 

alternative selections were prepared for each Jf'ate. For 

example, a list of 30 CWSs was prepared for Rhode 

Island that identified the first 2 randomly numbered 

CWSs that served more than 50,000 people, the first 8 

that served 3,001 to 50,000 people, the first 3 that 

served 501 to 3,000 people, and the first 17 that served 

25 to 500 people. A few additional CWSs from each 

size category (those next in line in the random-selection sequence) also were added to the list to provide 

alternative selections should any of the primary selections be dropped for lack of data.

Table 2. Targeted distribution of community water systems inventoried by State, principal source of water, 

and population served

[From Grady and Casey, 1999, table 6. Community water systems are public and private water systems that furnish water year round for donestic use to 

at least 25 people, or that have a minimum of 15 service connections. Target number of community water systems is proportional to actual d'stribution, 

except for Rhode Island, where the number of systems was increased from 14 to 30 to obtain valid minimum number for statistical analysis]

Number of community water systems

Principal source of 

water

State

Connecticut

Delaware

Maine

Maryland

Massachusetts

New Hampshire

New Jersey

New York

Pennsylvania

Rhode Island

Vermont

Virginia

Total 

(percent)

Ground 

water

108

45

64

90

71

124

103

388

356

22

72

251

1,694 

(80.3)

Surface 

water

12

1

16

11

34

10

19

150

87

8

15

53

416

(19.7)

More 

than 

50,000

2

1

0

1

5

0

4

6

6

2

0

4

31 

(1.5)

Population served

3,301 

to 

50,000

9

2

6

10

44

6

41

59

56

8

6

22

269

(12.7)

501 

to 

3,300

11

9

19

22

16

17

27

120

102

3

17

52

415 

(19.7)

25 

to 

500

98

34

55

68

40

111

50

353

279

17

64

226

1,395 

(66.1)

Total

120

46

80

101

105

134

122

538

443

30

87

304

2,110 

(100)

Percentage 

of 

comnunity 

wf»*er 

sys*«*ms

5.7

2.2

3.8

4.8

5.0

6.4

5.8

25.5

21.0

1.4

4.1

14.4

100

Approach
State agencies with primacy under the SDWA for 

implementation and oversight of compliance monitoring were contacted and requested to supply any data 

on VOCs collected during 1993-98 for the randomly 

selected CWSs in their State. When the water-quality 

data were received, it was reviewed to determine if the 

data represented surface- or ground-water sources and 

if the desired distribution of systems by source of water 

was obtained. It was noted (table 3) if a CWS used and 

sampled drinking water from both surface- and groundwater sources, but it was counted as a surface-water 

system with respect to fulfilling the study design. 

Alternative selections were used when the desired 

source-water distribution was not obtained or when no 

water-quality data were available for CWSs initially 

selected.

The actual distribution of 2,110 randomly 

selected CWSs used for this assessment is shown in 

table 3. In a few States, the actual distribution by

source and size differs slightly from the targeted distribution. This occurred where the availability of data for 

CWSs that were the primary random selections was 

limited and alternative selections were needed to 

achieve the total number of CWSs targeted for that 

state. The net changes made to the design to accommodate data availability were four additional groundwater systems and eight fewer small systems inventoried than were targeted by the design. These changes 

are considered too small to introduce any systematic 

bias in the study design, and the actual population of 

2,110 CWSs inventoried is representative of the overall 

distribution of CWSs in the study area. The total population served by the 2,110 CWSs, tabulated from the 

information coded for each system in SDWIS, is 

9,637,987 people (table 4) or about 16 percent of the 

total population served by all CWSs in the 12-State 

area.

Table 3. Actual distribution of randomly selected community water systems inventoried by State, source of water, and 

population served

[Both includes community water systems supplied by ground-water and surface-water sources]

Number of community water systems

Principal source of water

State

Connecticut

Delaware

Maine

Maryland

Massachusetts

New Hampshire

New Jersey

New York

Pennsylvania

Rhode Island

Vermont

Virginia

Total 

(percent)

Ground 

water

111

45

64

90

70

117

103

387

355

24

74

250

1,690 

(80.1)

Surface 

water

1

1

15

6

13

9

10

103

60

2

7

43

270 

(12.8)

Both

8

0

1

5

22

8

9

48

28

4

6

11

150 

(7.1)

More 

than 

50,000

2

1

0

1

5

0

4

6

6

2

0

4

31 

(1.5)

Population served

3,301 

to 

50,000

9

2

6

10

44

8

41

59

56

8

6

22

271 

(12.8)

501 

to 

3,300

11

9

19

21

16

24

27

120

102

3

17

52

421 

(19.9)

25 

to 

500

98

34

55

69

40

102

50

353

279

17

64

226

1,387 

(65.7)

Total

120

46

80

101

105

134

122

538

443

30

87

304

2,110

Percentage 

of 

cormunity 

water 

systems

5.7

2.2

3.8

4.8

5.0

6.4

5.8

25.5

21.0

1.4

4.1

14.4

100

10 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 4. Population served by community water systems in the study area

[CWS, community water systems]

State

Connecticut

Delaware

Maine

Maryland

Massachusetts

New Hampshire

New Jersey

New York

Pennsylvania

Rhode Island

Vermont

Virginia1

Total

Population served by 

all CWSs

2,611,549

678,296

590,953

4,548,230

7,815,920

729,939

7,629,001

16,594,651

10,512,736

970,231

470,563

5,297,854

58,449,923

Population served by 

randomly selected CWSs

959,421

186,774

118,370

196,238

1,347,538

106,344

1,810,899

1,847,884

1,568,755

372,523

96,079

1,027,162

9,637,987

Percentage of 

population served by 

randomly selected CW?-»

36.7

27.5

20.0

4.3

17.2

14.6

23.7

11.1

14.9

38.4

20.4

19.4

16.5

Includes District of Columbia.

The distribution of 4,427 ground-water sources 

(wells and springs) and 595 surface-water sources 

(intakes from reservoirs, lakes, and streams) known to 

provide drinking water to the 2,110 randomly selected 

CWSs is shown in figure 2. Identification of the 5,022 

sources and their locations were obtained from the 

SDWIS database, State datasets, USGS water-use data, 

and the CWSs themselves. Sources shown in figure 2 

include only those that are known to provide water to 

the randomly selected CWSs (or are sources to systems 

that sell water to the randomly supplied CWSs) and for 

which locational data (latitude and longitude of the 

surface-water intake or wellhead) are presently available. Consequently, figure 2 does not include all 

possible sources of water for the 2,110 CWSs, and 

there may be water samples in the 12-State database 

that were obtained from sources not shown in this 

figure. An extensive effort was made to collect as much 

information on sources as could be accomplished 

within the resources of this study, and the authors feel 

that the distribution shown in figure 2 includes the 

majority of sources associated with VOC analyses in 

the water-quality data.

Data Inventory

Grady and Casey (1999) inventoried the availability of data on VOCs for public drinking water in 

each of the 12 States in the study area. Information 

based on telephone surveys of State health and watersupply agencies indicated that data for some VOCs in 

drinking water were available in State computer databases for 11 of the 12 States; Connecticut mrmtains its 

drinking-water-quality data in paper files only. Electronic data were requested and received from the 11 

States; data for Connecticut were obtained by 

conducting a review of files for the selected CWSs and 

scanning paper copies of drinking-water analyses into 

an electronic database. Some states elected to provide 

data for all PWSs or more than the requested randomly 

selected CWSs. Five states provided data that preceded 

the requested period of record, with the oldest VOC 

data dating back to 1978 and the oldest MTPE data 

dating back to 1987.

Approach 11
80° 78° 76° 74° 72° 70° 68° 66° 64°

48°

46°

44°

42°

40°

38°

EXPLANATION

 GROUND-WATER SOURCE 

OF DRINKING-WATER SUPPLY

Base from U.S. Department of Commerce digital data 1:100,000,1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 2. Drinking-water sources of water for randomly selected community water systems in the study area showing 

(A) ground-water sources and (B) surface-water sources.

12 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
48°

46°

44°

42°

40°

38° -

80° 78°

B

76° 74° 72° 70° 68° 66° 64°

EXPLANATION 

SURFACE-WATER SOURCE 

OF DRINKING-WATER SUPPLY

Base from U.S. Department of Commerce digital data 1:100,000,1993 

Albers projection

100 200 MILES

0 100 200 KILOMETERS

Figure 2. Drinking-water sources of water for randomly selected community water systems in the study area showing 

(A) ground-water sources and (B) surface-water sources.-Continued

Approach 13
The availability of data on VOCs and, specifically, MTBE in drinking water for the 12 States 

compiled for this study is summarized in table 5. In 

total, more than 56,000 analyses for VOCs in drinking 

water for the period 1978-98 were compiled for nearly 

8,000 PWSs in the study area; these included 16,717 

MTBE analyses for the period 1987-98, representing 

more than 4,000 PWSs in the region. Screening the 

data for the 2,110 randomly selected CWSs and the 

1993-98 time period resulted in more than 21,000 VOC 

analyses available for this assessment. The number of 

analytes tested for in any given analysis ranged from 1 

to as many as 70 VOCs. The analytical coverage also 

differed substantially from state to state; Pennsylvania

and Vermont reported the fewest VOC analyte^ (46) 

whereas New Jersey reported the most (75). Ten States 

provided some MTBE data, but none were available for 

any drinking water systems in Delaware and Pennsylvania. Consequently, only 1,194 of the 2,110randomly 

selected CWSs reported one or more MTBE analysis, 

with a total of 5,510 analyses that included the gasoline 

oxygenate. In total, 84 VOC analytes, including 

isomers (o-, m-, andp-xylene), sums of isome^s (total 

xylenes, total dichlorobenzenes, cis- & trans-1,3- 

dichioropropene) or the sum of other related VOCs 

(total trihalomethanes), were reported in at least one 

analysis of drinking water compiled for this study.

Table 5. Availability of data on volatile organic compounds in drinking water for the study area, 1978-98

[PWSs, public water systems; CWSs, community water systems; VOC, volatile organic compound; MTBE, methyl terf-butyl ether]

State

Connecticut

Delaware

Maine

Maryland

Massachusetts

New Hampshire

New Jersey

New York

Pennsylvania

Rhode Island

Vermont

Virginia

Total

Number of 

active PWSs 

(and CWSs)1

4,460

(600)

564

(229)

1,898

(400)

3,123

(507)

1,629

(525)

2,071

(670)

4,740

(611)

9,129

(2,689)

10,249

(2,213)

451

(81)

1,270

(434)

4,241

(1,520)

43,825

(10,479)

Number of 

PWSs with 

any VOC data 

(number of 

analyses)

122

(694)

48

(225)

346

(2,941)

498

(2,947)

845

(5,197)

146

(453)

1,436

(13,336)

1,583

(15,004)

459

(5,746)

490

(3,571)

597

(2,487)

1,376

(4,206)

7,946

(56,807)

Number of 

randomly 

selected 

CWSs with 

any VOC data 

(number of 

analyses)

120

(682)

46

(195)

80

(665)

101

(555)

105

(1,513)

134

(453)

122

(2,287)

538

(6,909)

443

(5,746)

30

(1,273)

87

(399)

304

(958)

2,110

(21,635)

Number of 

VOC 

analytes 

reported

70

62

58

63

64

69

75

67

46

59

46

61

84

Number of 

PWSs with 

MTBE data 

(number of 

analyses)

122

(514)

0

(0)

216

(396)

494

(2,438)

75

(270)

130

(387)

1,095

(3,783)

351

(2,442)

0

(0)

251

(3,189)

89

(228)

1,354

(3,070)

4,177

(16,717)

Number of 

randorrfy 

selected 

CWSs with 

MTBE d-ta 

(number of 

analyse*)

120

(507)

0

(0)

55

(122)

101

(45<S)

75

(270)

130

(387)

65

(510)

241

(1,83?)

0

(0)

30

(511)

75

(18<l)

302

(724)

1,194

(5,510)

Data from U.S. Environmental Protection Agency's Safe Drinking Water Information System as of December 1,1997.

14 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Although the overall time period examined for 

this study is 1993-98, the actual period of record for 

data on VOCs, and especially MTBE, from each of the 

12 States varied considerably (table 6). Massachusetts 

and Rhode Island, for example, provided VOC and 

MTBE data that spanned the 6-year period, whereas 

electronic data for Virginia were only available for 13 

months in 1997 and 1998. New Jersey and Maine 

provided 6 years of electronic VOC data but their 

MTBE data were limited to a much shorter period in 

1997-98. Just three States Connecticut, Massachusetts, and Rhode Island provided data for MTBE that 

predated the introduction of RFG in 1995. Differences 

in the ending month of the period of record among the 

12 States are largely an artifact of when this study 

requested and obtained the analytical data. SDWA 

compliance monitoring has continued through the 

present in all 12 States.

The 84 VOCs included in at least one analysis of 

drinking water for the randomly selected CWSs are 

identified in appendix 1. Chemical analyses for 21 

regulated and 21 unregulated VOCs (appendix 1) are 

determined routinely for most drinking-water samples 

under provisions of the SDWA. Additionally, analysis 

for 14 other unregulated VOCs (appendix 1) may be 

required at the discretion of individual States. States 

have broad discretion in granting waivers to monitoring requirements; Pennsylvania, for example, only 

requires analysis for the 21 regulated VOCs at most 

CWSs where previous monitoring (largely prior to 

1993) demonstrated the lack of occurrence of unregulated VOCs. Consequently, the suite of VOCs included 

in the drinking-water data is variable and, beyond the 

21 regulated chemicals, is not consistent among the 12 

States (see appendix 2). Appendix 2 also includes data 

for five "total" VOCs dichlorobenzenes, 1,3-dichloropropene, trihalomethanes, m- & p-xylenes, and 

xylenes that were not reported consistently by all 

states. These "total" values were calculated as the sum 

of the isomer or component compounds (for example, 

the sum of the m-, o-, andp-dichlorobenzene analytical 

determinations) when one or more of the components 

were reported for any specific sample. The calculated 

"totals" were determined to afford the largest possible 

sample populations for these VOCs and to facilitate 

comparisons among the states.

Chemical analyses for VOCs sometimes also 

included two additional regulated compounds, the 

fumigants EDB and DBCP, and(or) several nonregulated chemicals (for example tetrahydrofuran; see 

appendix 1) that can be detected and identified by 

USEPA drinking-water methods 502.2 and 524.2. 

These compounds generally are reported in separate 

analyses for pesticides or other synthetic organic chemicals and were not widely reported with the State's 

VOC data. Eight of the nonregulated VOCs included in 

the data received from some States were analyzed for 

by less than 10 CWSs.

MTBE is not presently regulated under the 

SDWA, and compliance monitoring of public drinking 

water for MTBE is not required. Most of the 12 States 

studied, however, have issued drinking-water regulations or guidelines for MTBE that require or encourage 

PWSs in their purview to monitor for it. Some State or 

local agencies or individual water systems also have 

collected MTBE data as part of their general drinkingwater monitoring activities or specifically when 

sampling PWSs in areas where MTBE might be 

expected to occur (for example, near gasoline stations). 

For these reasons, the data inventory contains MTBE 

data for more than half of the designed 2,110 CWSs 

with at least one MTBE analysis available for 1,194 

CWSs in 10 of the 12 States (see table 5); two States 

(Delaware and Pennsylvania) reported no data on 

MTBE in drinking water.

Although most VOCs have numerous uses in 

industry, commerce, and household applications, there 

is no comprehensive National database with information available on the use of VOCs. The authors' interpretation of the primary use or source of each of the 84 

VOCs included in the data compilation also is included 

in appendix 1. They were classified among six predominant use categories that may have the most relevance 

to their occurrence in drinking water (1) disinfectant 

by-products, (2) gasoline components, (3) solvents, (4) 

chemicals used in the synthesis of other organic 

compounds, (5) refrigerants, and (6) fumigants. The 

purpose of identifying a predominate use of VOCs is to 

facilitate comparisons of their occurrence and distribution in drinking water but does not imply that the use is 

the only possible source for the VOCs reported in 

drinking water. Classification of VOCs into principal 

use categories is based on information developed by 

Bender and others (1999).

Approach 15
Table 6. Period of record for data compiled on volatile organic compounds and methyl terf-butyl ether in drinking water from 

randomly selected community water systems in the study area

[VOCs, volatile organic compounds; MTBE, methyl tert-butyl ether]

16 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Data Documentation

Because the data compiled for this study were 

obtained from 12 different States with different data 

reporting and management protocols, considerable 

review, editing, formatting, and documentation was 

needed. Electronic data obtained from the States were 

received in a variety of formats and included different 

data elements, codes, and levels of documentation. The 

data from each State were reformatted into the project's 

Microsoft Access© database so that consistent and 

valid comparisons could be made among the various 

State's data, and the occurrence and distribution of 

VOCs in drinking water could be described on a 

regional level. Each State's data were reviewed to 

ensure that it contained several basic elements considered to be necessary for use in this analysis. These 

included the PWSID, source locations (latitude and 

longitude), source-water type, population served, 

sample identification, analyte identification, and 

analytical results.

Every CWS is identified by a unique, 9-digit, 

alphanumeric SDWIS PWSID (for example, 

CT0040011). This identifier, or at least the numeric 

component of the SDWIS PWSID, was used by each 

State as an identifier with every water-quality analysis. 

The system name also was coded in all State databases. 

State identifiers and system name were cross-referenced to data from SDWIS retrievals to verify system 

identification. Locational information, specifically latitude and longitude coordinates for source waters (wells 

and surface-water intakes), were poorly documented in 

the State data as a whole. Until recently, providing an 

accurate latitude and longitude for all sources was not 

required of States or water systems as they filed the 

information requested for the SDWIS database. Some 

locational information was available in SDWIS, coded 

with the State drinking-water data, or was obtained 

from State environmental agencies. Where no information was available from these sources, efforts were 

made to obtain source locations by using interactive 

mapping software (DeLorme, 1999) to locate the street 

address provided from SDWIS, State data, or by 

contacting the CWSs. Through this effort, latitude and 

longitude coordinates were assembled for more than 

5,000 individual sources supplying the 2,110 randomly 

selected CWSs.

Information on the source of water sampled is 

needed to determine if there are differences in the 

occurrence of VOCs and the vulnerability of water

supplies to VOC contaminants between surface- and 

ground-water systems and between surficial unconfined aquifers and deeper confined aquifers. Fowever, 

the source of the drinking-water sample was not always 

identified in each State's data. Most drinking-water 

analyses (about 85 percent), had information coded 

with the analytical data that could be used to identify 

whether the sample was from a ground-water or a 

surface-water source. For some samples, such as those 

collected from locations within the distributic n system 

of CWSs with both ground- and surface-water sources, 

the source was unidentified and could represent a blend 

of sources. Additionally, some drinking-water analyses 

were for samples composited from several sources or 

even from multiple systems. Consequently, tlis study 

could not interpret the drinking-water data ba^ed on an 

unequivocal understanding of the source of the 

drinking-water associated with each sample.

The analytical data were designated as either 

representing CWSs exclusively supplied by groundwater sources, those exclusively supplied by surfacewater sources, or as data for CWSs with both groundand surface-water sources based on the information 

coded with the analytical data from the State database, 

or on information from SDWIS regarding the water 

sources that supply each of the 2,110 randomly selected 

CWSs. SDWIS classifies a CWS as a surface-water 

system if it has any surface-water sources, or purchases 

water from a system that has surface-water sources. 

Ground-water supplied systems include those supplied 

exclusively by ground-water sources, ground-water 

sources under the influence of surface water (U.S. 

Environmental Protection Agency, 1994), or water 

purchased from CWSs supplied exclusively f *om 

ground water. For this study, the source category of 

"both surface-water and ground-water sources" was 

used for samples from systems with both types of 

source waters even when information coded with the 

analytical data indicated the type of source water 

sampled.

Information on the population served t^ CWSs 

is needed to estimate potential human exposure to 

VOCs from drinking water. Most States provided information on the number of people served by ea-h CWS 

or the information was obtained from the December 

1997 SDWIS retrieval used to design the survey. The 

SDWIS population-served data agreed in mo^t cases 

with the information provided by the States, but it is 

uncertain how often this data field is updated or how 

recently the States make the updates available in the

Approach 17
SDWIS database. No information was available from 

the State data or from SDWIS that documented any 

historical changes in population served that could be 

correlated with specific sample dates.

Other useful sample-specific information was 

included with the analytical data from some States, but 

the consistency of reporting and the content of what 

was reported varied considerably from state to state. 

Several States reported a unique sample or laboratory 

identification number that was used to reference 

specific analytical results to specific sources, sample 

locations, and (or) sample temporal sequences. Lack of 

a unique sample indentifier confounded efforts to 

resolve specific analytical results for some CWSs when 

apparent duplicate samples were collected from the 

same source or location on the same date. A sample 

location (name or number of a specific site where a 

sample was collected, for example, well number 1, 

kitchen tap), sample location type (well head or intake, 

point of entry to the water distribution system, distribution system sample), or sample type (raw, finished, 

routine, special, duplicate, confirmation) was 

frequently, but not always, provided. Information on 

which laboratory performed the analysis, the USEPAapproved analytical methods used, and the date of the 

analysis also was provided by some States.

Differences in the manner in which States identified and reported the suite of VOC analytes that were 

determined for each drinking-water analysis caused the 

greatest difficulties in compiling the 12-State drinkingwater database. A few States provided the analytical 

results in an unambiguous "crosstable" format, with 

each row representing a specific sample and each 

column a specific analyte. With this format, the results 

for every analytical observation were coded as a 

numerical concentration value if detected, or with a 

"less than" symbol and the analytical detection level 

(for example, "<0.05"), a zero, or some other nonnumeric indication that the analyte was not observed 

(that is, not detected "ND", or below detection levels 

"BDL") in the water sample. Most States, however, 

stored and transmitted their data in a format designed to 

minimize the volume of data. In this data format, only 

detectable concentrations were identified. If no 

contaminants were detected in a sample, some abbreviated indication of the multiple analytes included in the 

analysis would be coded (for example, "VOCs"), or the 

analytical method used would be indicated (for 

example, USEPA Drinking Water Method "502.2" or 

"524.2"). When this method was used, documentation

was needed from the States as to what analytes were 

explicitly included in the coded methods for the period 

of record reported, and what method detection level 

(MDL) or minimum reporting level (MRL) was applicable for each analyte. Some States provided r reference table that included such documentation along with 

the transmitted data. For some States, this information 

could only be obtained from contacting laboratory or 

other staff familiar with their State's historical data 

collection, analysis, and management procedures. With 

this level of documentation, it was possible to populate 

crosstables in the project's database that code a less 

than MDL or MRL value, ND, or BDL for every observation of the suite of VOC analytes without a specified 

detectable concentration.

Additional uncertainty was associated with the 

actual quantification levels of VOC analytes and 

reported concentrations for some States. Laboratory 

quantification levels are generally contaminant and 

method specific, and documentation of the MDL or 

MRL was often missing in the State data. If documentation could not be obtained from the State, the quantification levels could sometimes be surmised from the 

analytical data, particularly if some "less than" values 

were coded and there were sufficient numbers of observations at detectable concentrations. For other rnalytes, 

information on the method and the USEPA-specified 

practical quantification level (PQL) for each analyte 

served to estimate the MRL; for most VOCs, this was 

equal to 0.5 jig/L. Not all data were reported in the 

same concentration units, however, even for data from 

the same State. For this study, any data coded as "parts 

per million" or "milligrams per liter" were converted to 

micrograms per liter. Any data values that were 

extreme outliers were reviewed to determine if the 

concentration units were correctly reported. Tris was 

accomplished where possible by obtaining a paper 

copy of the analytical results for those sample? from 

the States and comparing the concentration values 

coded in the electronic data to information in the laboratory report for that sample. Selected analyse^ for 

about 10 percent of all CWSs were confirmed by 

comparison to the original laboratory analytical report, 

and few discrepancies were uncovered.

Although documentation of analytical coverage 

and reporting levels for most VOC analytes, particularly the regulated compounds, was not too difficult, 

documentation of MTBE analyses was more problematic. Several States did not report MTBE when the 

oxygenate was analyzed for but not detected ir a water

18 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
sample. For the States where all or most analyses are 

performed by the State laboratory (Maine, New Hampshire, and Virginia), it was generally possible to determine a date when MTBE was included in the 

laboratory's VOC method. All samples subsequent to 

that date that did not specifically contain detectable 

concentrations of MTBE were assumed to have been 

analyzed for that compound but not reported. It is 

possible that this assumption may be wrong for a small 

number of samples and if so, then MTBE detection 

frequencies determined for those States may be slightly 

underestimated. For other States where numerous 

private laboratories perform the bulk of the drinkingwater analyses (Massachusetts and Vermont), a review 

of the State's paper files on the drinking-water analyses 

was conducted to confirm if MTBE was among the 

VOC analytes. However, paper records for many of the 

samples included in the electronic database could not 

be located. To the extent that some randomly selected 

CWSs in these States may have had drinking-water 

samples analyzed for MTBE without detection, but no 

confirming paper records could be located and consequently these systems were excluded from the MTBE 

analysis, then MTBE detection frequencies determined 

for those States may be slightly overestimated.

Additional ancillary data are needed to extend 

the value of the information on drinking-water quality 

beyond occurrence and distribution of VOCs. Information on the location, capacity, and processes used at 

filtration and treatment plants, the geographic boundaries and characteristics of the water-distribution area, 

actual population served by each source or segment of 

the distribution system, and quantity of water delivered 

by suppliers could be used to more fully explain and 

compare the frequency of detection and concentration 

of VOCs in drinking water. For surface-water sources, 

specific information on the depth, size, and operation 

of intakes, the number, type, and location of any 

discharges to receiving surface-water bodies that are 

source waters for CWSs; land-use patterns in source 

surface-water basins; and locations of upwind releases 

of VOCs to the atmosphere and other potential VOC 

sources would be useful. For ground-water sources, 

specific information on the supply well and the 

producing aquifer (depth, diameter, water level, depth 

to the open interval, other construction characteristics 

of the well, pump type, well yield, and contributing 

area to the well), as well as land use, population 

density, locations of known or potential VOC sources 

(gasoline stations, dry cleaners, other commercial and

industrial users), and other cultural, demographic information for the area adjacent to the well could be 

obtained. Although some of these data were included 

with the analytical data or were obtained from other 

sources during the inventory of CWSs for a few States, 

these data elements were not widely available and were 

inconsistently documented in the State data and the 

SDWIS database. It was possible to obtain some ancillary data elements, particularly the location of wells 

and surface-water intakes with respect to OX^TRFGfuel areas and urban land use, from regional GIS coverages. The lack of consistent, verified ancillary data for 

many CWSs, however, generally limited the data analysis in this study to determination and description of 

VOC detection frequencies and concentrations.

Data Analysis

Statistical summaries of the data, presented in 

tabular and graphical formats in this report, are, used to 

describe the occurrence and distribution of MTBE and 

VOCs in drinking water. Descriptive statistics include 

number of samples, number of detections, the 

frequency of analysis (percentage of analyses that 

include analyte and percentage of CWSs with analyses 

for each specific analyte), the frequency of detection 

(percentage of CWSs with detections), detectable 

concentration range, and medians of detected VOC 

concentrations. Although the percentage of samples 

with detections is summarized in appendix 3 for the 

reader's information, the authors would caution that 

these results are often skewed by the highly variable 

number of samples from each CWS. Also, on~e a 

contaminant has been detected at a CWS, repetitive 

sampling and detections are often reported. Unless 

otherwise indicated, when median concentrations are 

reported, the median concentration for all detections at 

each CWS was determined and used to calculate the 

median concentration reported in text and tables in this 

report. Medians of detected concentrations provide a 

positively biased indication of actual median VOC 

concentrations because samples with concentrations 

below analytical reporting levels are not included, but 

this statistic is useful when comparing concentrations 

among highly censored analytes.

The occurrence of VOCs, as defined by the 

frequency of detection (or drinking-water criteria 

exceedance), was calculated by dividing the number of 

CWSs reporting detections (or number of CWSs with 

exceedances) by the number of CWSs with analyses

Approach 19
and multiplying by 100. A CWS is counted as having 

had a VOC detection if a measurable concentration of 

an analyte was reported in any one or more water 

sample(s) associated with any source or sample location for that CWS. For the statistic "frequency of detection at any reporting level" used in this report, no effort 

was made to censor data with multiple reporting levels. 

When the frequency of detection is censored at a 

specific reporting level (for example, 1.0 |Ug/L) all 

samples reported as non-detections at higher reporting 

levels (for example, < 2.0 |Ug/L, <5.0 |Ug/L, etc.) are 

deleted, all samples with lower reporting levels (for 

example, <0.5 |Ug/L, <0.1 |Lig/L) are converted to < 1.0 

|Ug/L, and all observations with reported concentrations 

that are less than 1.0 jug/L (for example, 0.9 |Lig/L, 0.5 

|Ug/L, etc.) are converted to < 1.0 |Ug/L values. 

Censoring the data at specific reporting levels generally eliminates some CWSs from the analysis; this 

affect is most apparent at the 0.5-|Ug/L reporting level.

Descriptive and nonparametric statistics, histograms, cumulative frequency plots, and boxplots 

(Helsel and Hirsch, 1992) are used in this report to 

describe the frequency of detection and concentration 

of MTBE and other VOCs in drinking water relative to 

the total number of CWSs and the total number of 

drinking-water samples for the 12-State region collectively, and for each individual State. The data also are 

summarized to present the occurrence and distribution 

in relation to the source of drinking water and to each 

population-served category. Estimates of the total 

number of people potentially exposed to individual 

compounds and selected groups of VOCs were made 

on the basis of data on the actual population served by 

those CWSs reporting VOC detections. Maps were 

prepared showing the locations of drinking-water 

sources (wells and surface-water intakes) for CWSs 

that have reported detectable concentrations MTBE 

and other VOCs in relation to oxygenated gasoline use 

and (or) urban land use. Where appropriate, a variety of 

hypothesis tests, including contingency-table tests 

(Pearson's chi-square test with Yates' continuity 

correction), Kruskal-Wallis tests, and the Wilcoxon 

signed rank test (Helsel and Hirsch, 1992), were 

conducted to test for relations between the frequency of 

detection or concentrations of VOCs and anthropogenic factors such as land use, population density, and 

the distribution of high MTBE-use areas.

Contingency-table tests are used in this report 

because the highly censored VOC analytical data 

largely precludes analysis by hypothesis tests that

evaluate continuous variables. Contingency tables 

measure the association between two discrete, categorical variables, for example, the probability of detecting 

a VOC (verses the probability of nondetectior) related 

to a type of land use or the presence or absence of some 

other anthropogenic factor. The data are arranged into 

a matrix of rows and columns with no natural 

ordering and the distribution of data among the 

categories is tested to determine if the row classification is independent of the column using the chi-square 

distribution (Helsel and Hirsch, 1992). As with other 

statistical tests used in this report, the results of the 

contingency tests are expressed by the "p-value" or the 

significance level attained by the data; for this report, 

the null hypothesis is rejected and the two variables are 

determined to be significantly related at p-values less 

than 0.05 (95-percent confidence level). When the variables are found to be dependent or related, however, it 

is not necessarily implied that one variable causes the 

observed response in the second variable.

OCCURRENCE AND DISTRIBUTION OF 

VOCS IN DRINKING WATER

An overview of the occurrence and distribution 

of VOCs in drinking water is presented here as an introduction to more detailed findings presented in subsequent sections of this report. It is intended to 

summarize the overall status of the quality of drinking 

water in the 12-State region with respect to VOC 

contaminants at any reporting level, and to provide a 

reference for additional observations on the occurrence 

and distribution of specific analytes by State, source, 

size, or other characteristics of the CWSs. Detailed 

summaries of the frequency of detection at specific 

reporting levels and the concentrations of all VOC 

analytes reported in the available data are included in 

appendix 3 and in the text, tables, and figures in subsequent sections of this report.

Data compiled for the 2,110 randomly selected 

CWSs in the 12-State study area included 21,635 analyses of drinking-water samples collected from 1993- 

98. Of the 84 VOC analytes tested for in some drinking 

water (see appendixes 1 and 2), 64 compounds (table 7) 

have been reported at a detectable concentrat: on in at 

least 1 sample. A total of 8,955 of the 21,635 analyses 

assembled for this study (41 percent) reported at least 

1 of the 64 VOCs at a detectable concentraticn. VOCs 

have been reported at detectable concentrations 19,625 

times in drinking-water samples.

20 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 7. Volatile organic compounds detected in drinking water from randomly selected community water systems 

in the study area, 1993-98

[(ig/L, micrograms per liter]

Volatile 

organic 

compound

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1,1-Dichloroethene

cis- 1 ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2, 2-Dichloropropane

cis- 1 ,3 -Dichloropropene

Ethylbenzene

Number of 

analyses

632

15,987

12,155

13,980

13,895

12,733

12,020

11,284

233

16,068

13,933

12,691

14,055

12,721

12.504

12,688

7,009

12,729

15,866

15,914

12,147

12,786

16,090

15,357

16,017

16,046

16,015

15,864

12,710

12,689

8,755

15,818

Number of 

detections

12

52

10

2,813

728

10

22

1

1

120

1,846

10

3,802

39

3

5

29

18

16

37

202

440

119

428

672

27

118

83

10

4

1

86

Range of 

detected 

concentrations

(M9/L)

10-49

0.1-26.2

0.17-5.49

0.1-73.3

0.1-32.5

0.39 - 5.0

0.2-5.6

0.9

0.8

0.1-6.3

0.1 - 83.8

0.5 - 84.5

0.06-410

0.5 - 79.3

0.13-1.84

0.59 - 4.4

0.01 - 1.0

0.1-7.47

0.2 - 95

0.22 - 3.2

0.5 - 22

0.13-24

0.22 -9.9

0.33 -54.4

0.18- 148

0.51-46.2

0.4 - 27

0.3 - 22.3

0.17-7.46

0.25 - 3.77

0.54

0.34 - 39

Volatile 

organic 

compound

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl terf-butyl ether

Monochlorobenzene

Naphthalene

«-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1,1, 2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1 , 1 ,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Trihalomethanes, total

1 ,2,4-Trimethylbenzene

1 ,3,5-Trimethylbenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes, total

Number of 

analyses

7,144

11,921

10,584

11,853

11,882

890

646

5,510

15,944

7,224

12,019

15,584

12,727

12,548

16,082

404

15,822

11,918

15,461

16,116

15,843

16,135

12,711

3,549

12,011

12,017

15,054

7,897

10,331

8,311

2,426

9,643

Number of 

detections

33

56

2

1

6

8

2

343

22

9

4

5

2

1

1,613

2

134

2

9

1,097

9

1,661

47

2,448

26

23

62

33

51

15

26

109

Range of 

defected 

concentrations

(M9/L)

0.01 - 1.1

0.2 - 5.0

0.9-1.1

1.07

0.5 - 4.8

0.6 - 340

16-20

0.26 - 210

0.3-2.1

0.3 - 2.4

0.28 - 9.74

0.6-5.6

1.0

3.9

0.13-640

27 - 194

0.05 - 76.9

0.5

0.2-1.14

0.1 - 191

0.5 - 3.6

0.1-930

0.5 - 4.5

0.1 -293

0.19-26.2

0.5-11.6

0.5 - 28.5

0.3 - 6.0

0.2-65.1

0.3 - 4.2

0.5 - 155

0.4^ - 50.2

Occurrence and Distribution of VOCs in Drinking Water 21
VOC concentrations in drinking-water samples 

reported by randomly selected CWSs in the 12-State 

area during 1993-98 ranged from 0.01 fig/L for detections of ethylene dibromide and dibrotnochloropropane 

to 930 fig/L for trichloroethylene (table 7). Most of the 

reported VOC concentrations are low (fig. 3) with 70 

percent of all detections at concentrations less than 10 

|ig/L, but concentrations of 16 VOCs equaled or 

exceeded Federal drinking-water regulations or health 

advisories (table 8). Regulated or recommended levels 

for the 16 VOCs have been equaled or exceeded in 

1,102 (5.1 percent) of the 21,635 drinking-water 

samples.

The 16 VOCs that have exceeded drinking-water 

regulations or recommendations include 8 solvents, 

2 VOCs used mostly in the synthesis of organic 

compounds, 2 fumigants, 2 gasoline components 

(including MTBE), a refrigerant, and the sum of the 

four THM disinfectant by-products. One or more 

drinking-water samples exceeded the MCLs for 13 

VOCs; 2 VOCs chloromethane and hexachlorobutadiene equaled or exceeded Health Advisory (HA) 

levels, and MTBE has been reported at concentrations

equal to or exceeding the Drinking Water Advisory 

(DWA) level recommended based on aesthetic (taste 

and odor) considerations.

Although only a small percentage of all 

drinking-water samples equaled or exceeded MCLs, 

total trihalomethanes, trichloroethylene, and tetrachloroethylene have been reported at concentrations that 

exceed MCLs in almost 200 to more than 500 samples 

collected during!993-98, and some of these samples 

contained concentrations more than 100 time" greater 

than the MCLs. Information coded with specific 

drinking-water samples indicates that some reported 

"MCL violations" by the affected CWSs were for 

unprocessed water samples collected from their 

sources prior to the distribution systems. It is also 

evident, at least for the CWSs with the high solvent 

concentrations, that the use of granular activated 

carbon filtration and other forms of water treatment or 

blending mitigate these concentrations prior to distributing the water, but the data indicate that several 

sources for these systems have been affected and the 

nature of some samples with high concentrations are 

poorly documented.

Table 8. Volatile organic compounds that equaled or exceeded regulated or recommended concentrations 

in drinking water from randomly selected community water systems in the study area, 1993-98

[(ig/L, micrograms per liter; MCL, Maximum Contaminant Level; HA, Health Advisory; DWA, Drinking-Water Advisory; 

CWSs, community water systems]

Volatile organic 

compound

Benzene

Carbon tetrachloride

Dibromochloropropane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

Ethylene dibromide

Tetrachloroethylene

Trichloroethylene

Total trihalomethanes

Vinyl chloride

Chloromethane

Hexachlorobutadiene

Methyl tert-buiyl ether

Drinking-water regulation or 

recommendation

Value, in ng/L

5

5

0.2

5

7

70

5

5

0.05

5

5

100

2

3

1

20-40

Type

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

MCL

HA

HA

DWA

Number of 

samples with 

concentrations 

that equaled or 

exceeded value

4

1

3

3

89

2

11

11

8

515

496

186

12

14

1

27

Number of CWSs 

reporting 

concentrations 

that equaled or 

exceeded value

2

1

3

2

6

2

8

3

5

32

25

46

4

11

1

10

Population 

served traffected CVSs

414

5,000

39,269

1,655

105,592

29,425

84,915

43,669

539,168

840,448

497,750

868,705

148,798

50,029

425

48,827

22 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
LLJ 

CD

LJJ 

O 

DC 

LJJ 

0. 

LJJ

<

=} 

^

ID 

O

100

80

60

40

20

0

0.1 1 10

VOLATILE ORGANIC COMPOUND CONCENTRATIONS, IN MICROGRAMS PER LITER

100

Figure 3. Cumulative distribution of concentrations of volatile organic compounds detected in drinking-water 

samples from randomly selected community water systems in the study area,1993-98 (data for 19,625 detections).

The frequency of detection for the 64 VOCs 

reported in drinking water ranged from 41 percent of 

CWSs with total trihalomethanes, to 0.01 percent of 

CWSs with isopropylbenzene (table 9). The four most 

frequently detected individual VOC analytes were the 

four THM compounds chloroform, bromodichloromethane, chlorodibromomethane, and bromoform chemicals produced as by-products of 

disinfecting drinking water with chlorine. This observation is consistent with the fact that nearly all the 

drinking-water data are purported to represent 

"finished" drinking water, collected at the point-ofentry to the CWS's distribution system (or at more 

distal locations within the distribution system) 

following whatever water-treatment processes, such as 

chlorination, the CWSs may utilize.

MTBE was the next most frequently detected 

VOC, reported in 8.9 percent of the 1,194 CWSs where 

it was tested for, and, after the trihalomethanes, was the 

only VOC other than the solvent 1,1,1-trichloroethane 

to be detected in more than 5 percent of the CWSs. Two 

other common solvents, tetrachloroethylene and 

trichloroethylene, and two gasoline compounds, 

toluene and total xylenes, were detected in drinking

water from more than 4 percent of the CWSs. About 

one-third of the VOCs detected in drinking water were 

reported in 1 to 3 percent of the CWSs, but trore than 

half (33) of the 64 VOCs detected in drinking water 

were found in less than 1 percent of CWSs sampled for 

these compounds. The infrequent detections of many 

VOCs at generally low concentrations, together with 

the lack of any detections for 20 other VOC analytes 

(table 10) underscores the observation that although 

some VOCs, including MTBE, have been reported 

widely in drinking water in the Northeast and MidAtlantic region, the problem is largely confined to 

fewer than a dozen contaminants.

Analytical coverage for VOCs in drinking water 

among the randomly selected CWSs was highly variable (see tables 7, 9, appendix 2) and none of the 84 

VOCs were tested for by all 2,110 CWSs, and 20 VOCs 

were analyzed by less than half of the CWSs. The most 

frequent VOC analytes were 19 of the regulated VOCs 

that were tested for at least once by 97 percent of the 

CWSs. An additional 17 of the VOCs were tested for 

by 75 percent or more of the CWSs, and 24 other VOC 

analytes were analyzed for by more than 50 percent of 

the 2,110 CWSs. Among VOCs that have been

Occurrence and Distribution of VOCs in Drinking Water 23
detected in drinking water, 9 were analyzed for in less 

than half of the 2,110 CWSs (with as few as 103 CWSs 

reporting analyses for carbon disulfide).

The THM data demonstrate how the problem of 

missing data for a substantial number of CWSs 

confounds comparison of the detection frequencies for 

some VOCs. Although THMs were among the most 

frequently analyzed VOCs, almost 27 percent of the 

randomly selected CWSs reported no THM data, 

including 32 percent (174 of 538) of the CWSs in New 

York and 88 percent (388 of 443) of the systems in 

Pennsylvania. Furthermore, the majority of the CWSs 

without THM data are small to medium sized, groundwater supplied systems that are less likely to chlorinate 

their water, may have lower levels of naturally occurring organic compounds, and consequently, would 

have lower THM detection frequencies than larger 

surface-water supplied systems. The incomplete THM 

data and the resulting nonrepresentative distribution of 

systems reporting THM results introduces a bias into 

the calculated THM detection frequency.

Other differences in the data, including different 

reporting levels used by various State and private laboratories and disparate numbers of samples reported for 

each CWS, also may confound a State-by-State (or by 

source, size, or other system characteristics) comparison of VOC-detection frequencies. The lack of a 

consistent analytical coverage and reporting levels 

hampers comparisons of detection frequencies and 

diminishes the representativeness of the findings. Little 

can be done to standardize the data for large numbers 

of missing analyses, but reporting levels can be made 

more uniform by censoring the data at relevant concentrations. This approach has been used when possible in 

the following sections to facilitate comparisons of 

detection frequencies of specific analytes by source, 

size, and State.

By censoring the data at the l.O-fig/L reporting 

level and including only those analytes with data for at 

least half (1,055) of the 2,110 randomly selected 

CWSs, a more meaningful comparison can be made of 

the relative occurrence of 54 VOC contaminants that 

meet these criteria. Among the 64 VOCs reported in 

drinking water (see tables 7 and 9), only 8 acetone, 

sec-butylbenzene, carbon disulfide, c/5-l,3-dichloropropene, methyl ethyl ketone, methyl isobutyl ketone, 

tetrahydrofuran, and 1,2,3-trichlorobenzene are 

dropped from any further analysis of VOC detection 

frequencies because they do not meet one or both these 

criteria. Also, five other VOC analytes included in

tables 7 and 9 that have been reported inconsistently in 

the State databases total trihalomethanes, xylenes 

total, m-xylene, p-xylene, and m- & p-xylenes are 

replaced by the calculated sums for "total trihalomethanes" (sum of the concentrations of the chloroform, 

bromodichloromethane, chlorodibromomethane, 

bromoform or the value of total trihalomethanes coded 

in some analyses), "m- &p-xylenes" (sum of/r-xylene 

and p-xylene or the value of m- & p-xylenes cided in 

some analyses), and "total xylenes" (sum of the calculated m- & p-xylenes plus o-xylene values or the value 

of total xylenes coded in some analyses) in the 

following analysis. Although most VOC analytes were 

reported by the States at the 0.5-|0,g/L reporting level, 

using the 1.0-fig/L reporting level allows comoarison 

of detection frequencies at a conservative quantification level (above the practical quantification limit for 

all analytes) and allows for inclusion of MTBE in the 

comparison. At a reporting level of 0.5 (ig/L, only 985 

CWSs had analytical data for MTBE. The requirement 

of having data for at least half of the 2,110 CWSs 

allows for a minimum of 10 percent of all CWSs in the 

12-State area to be represented in the data.

The frequency of detection at a reporting level of 

1.0 (ig/L for the 54 VOC analytes (or sums of 2 nalytes) 

that were sampled for in drinking water from at least 

half of the 2,110 randomly selected CWSs in the study 

area are listed in appendix 3 and are shown in figure 4. 

This figure demonstrates the pervasiveness of the trihalomethane disinfectant by-products in drinking water 

compared to all other types of VOCs. Trihalomethane 

detection frequencies at 1.0 (ig/L range from 8 percent 

(bromoform) to almost 34 percent (chloroform) of the 

randomly selected CWSs, and were generally f-om 2 to 

more than 300 times other VOCs. MTBE, reported in 

7.8 percent of the CWSs, was the only other VOC 

detected in more than 5 percent of the CWSs at a 

reporting level of 1.0 (ig/L. MTBE plus five additional 

gasoline components were among the most common 

VOCs reported in drinking water, however coUectively, solvent compounds were the most numerous 

VOCs detected in drinking water. Nearly half (23) of 

the 54 VOCs detected in drinking water at a reporting 

level of 1.0 (ig/L were solvents, including the widely 

used compounds tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethane. VOCs with more 

limited uses organic synthesis compounds, refrigerants, and fumigants were generally detected in less 

than 1 percent of the CWSs at concentrations at or 

above 1.0 (ig/L.

24 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 9. Frequency of detection of volatile organic compounds at any reporting level in drinking water from randomly selected 

community water systems in the study area, 1993-98

[CWSs, community water systems]

Volatile 

organic 

compound

Number of Number of 

CWSs with CWSs with 

analyses detections

Percentage 

of CWSs 

with 

detections

Disinfectant by-products

Trihalomethanes, total

Chloroform

Bromodichloromethane

Chlorodibromomethane

Bromoform

Methyl /erf-butyl ether

Xylenes, total

Toluene

w-Xylene

Ethylbenzene

o-Xylene

m- & p-Xylenes

p-Xylene

Benzene

Naphthalene

n-Butylbenzene

1,3,5-Trimethylbenzene

seoButylbenzene

1,1,1 -Trichloroe thane

Trichloroethylene

Tetrachloroethylene

Dichloromethane

Acetone

cis- 1 ,2-Dichloroethene

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

Methyl ethyl ketone

Carbon tetrachloride

Tetrahydrofuran

Dibromomethane

1 ,2-Dichloropropane

304 125

1,504 589

1,503 486

1,507 389

1,504 193

Gasoline components

1,194 106

1,339 57

2,095 88

600 17

2,095 51

1,423 32

876 16

683 11

2,095 30

1,379 8

1,569 6

1,568 7

1,471 1

Solvents

2,086 106

2,090 94

2,090 93

2,088 60

309 9

2,089 43

1,666 31

2,088 39

1,785 34

334 6

2,086 32

136 2

1,667 14

2,087 15

41

39

32

26

13

8.9

4.3

4.2

2.8

2.4

2.2

1.8

1.6

1.4

0.6

0.4

0.4

0.07

5.1

4.5

4.4

2.9

2.9

2.1

1.9

1.9

1.9

1.8

1.5

1.5

0.8

0.7

Volatile 

organic 

compound

trans- 1,2-Dichloroethene

Chloroethane

o-Dichlorobenzene

Methyl isobutyl ketone

1 ,2,4-Trichlorobenzene

1 , 1 ,2-Trichloroethane

Monochlorobenzene

n-Propylbenzene

p-Chlorotoluene

1 ,2,3-Trichloropropane

o-Chlorotoluene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroe thane

Dibromochloropropane

Ethylene dibromide

p-Dichlorobenzene

Bromomethane

cis- 1,3-Dichloropropene

Chloromethane

Dichlorodifluoromethane

Fluorotrichlorome thane

Number of Number of 

CWSs with CWSs with 

analyses detections

2,090 13

1,665 7

2,096 8

331 2

2,092 7

2,088 6

2,096 5

1,569 4

1,672 4

1,665 4

1,584 2

1,667 2

1,581 1

Fumigants

1,440 25

1,517 26

2,096 19

1,667 9

1,078 1

Refrigerants

1,667 29

1,628 20

1,543 9

Percentage 

of CWSs 

with 

ejections

0.6

0.4

0.4

0.3

0.3

0.3

0.2

0.2

0.2

0.2

0.1

0.1

0.06

1.7

1.7

0.9

0.5

0.09

1.7

1.2

0.6

Organic synthesis compounds

Carbon disulfide

Bromochloromethane

1 ,2,4-Trimethylbenzene

Vinyl chloride

1 ,3 -Die hloropropane

2 ,2-Dic hloropropane

Hexachlorobutadiene

Styrene

p-Isopropyltoluene

1 ,2,3-Trichlorobenzene

Isopropylbenzene

103 1

1,628 10

1,567 9

2,062 9

1,665 5

1,666 3

1,167 2

2,078 5

1,548 2

1,550 1

1,546 1

1.0

0.6

0.6

0.4

0.3

0.2

0.2

0.2

0.1

0.06

0.01

Occurrence and Distribution of VOCs in Drinking Water 25
Table 10. Volatile organic compounds undetected in drinking water from randomly selected community water 

systems in the study area, 1993-98

[CWSs, community water systems]

Volatile organic compound

Acrolein

Acrylonitrile

Bromobenzene

teft-Butylbenzene

1-Chlorobutane

2-Chloroethyl vinyl ether

m-Dichlorobenzene

Dichlorobenzenes, mixed isomers

1 , 1 -Dichloropropene

trans- 1 ,3-Dichloropropene

Number of 

analyses

32

32

11,966

11,283

24

59

12,736

124

12,713

8,757

Number of 

CWSs with 

analyses

8

8

1,368

1,470

4

8

1,674

27

1,665

1,078

Volatile organic compound

cis- & frans-l^-Dichloropropene

Diethyl ether

Hexachloroethane

H-Hexane

Methyl butyl ketone

Methyl methacrylate

Nitrobenzene

Pentachloroethane

1 , 1 ,2-Trichloro- 1 ,2,2-trifluoroethane

1 ,2,3-Trimethylbenzene

Number of 

analyses

3,498

411

24

83

233

24

24

24

172

389

N imberof 

CWSs with 

analyses

463

134

4

13

103

4

4

4

80

101

Overall, VOCs were detected at or above 

1.0 |ng/L in drinking-water samples from 38 percent 

(795) of the 2,110 randomly selected CWSs (table 11), 

however, detections were reported nearly three times 

more frequently in drinking water from systems 

supplied by surface-water sources (75 percent of 270 

CWSs) or both surface- and ground-water sources (74 

percent of 150 CWSs) than in systems supplied exclusively by ground-water sources (28 percent of 1,690 

CWSs). The occurrence of VOCs also was clearly 

related to the size of CWSs very large and large 

systems reported more frequent detections at or above 

1.0 |ng/L (100 percent and 79 percent, respectively) 

than medium and small systems (50 percent and 24 

percent, respectively). The observation that, in general, 

VOCs are detected more frequently in large to very 

large CWSs supplied at least in part by surface-water 

sources, than in smaller systems supplied exclusively 

by ground-water sources clearly reflects the elevated 

occurrence of THMs in those systems (table 12), but

other VOCs also were detected most often in drinking 

water from the larger CWSs.

The frequency of VOC detections at or above 

1.0 |ng/L in drinking water ranged considerably from 

State to State (table 11), with the highest frequencies 

(68,60, and 59 percent of CWSs for New Jersey, Rhode 

Island, and Massachusetts, respectively) reported by 

States with high population density (table 13) and 

extensive urban development. Still, more than 30 

percent of the CWSs in 10 States have reported concentrations of the 54 selected VOCs at or above 1.0 JLig/L 

in drinking water, and more than 20 percent of the 

systems in all 12 States have had these VOCs in their 

drinking water at comparable concentrations (table 11). 

The lowest VOC-detection frequencies were in large 

States with substantial rural regions (Maine and Pennsylvania). This may reflect a relative paucity of sources 

of VOC contaminants in rural areas, but it also may be 

an artifact of the somewhat more limited suite of VOC 

analytes tested for in many drinking-water samples 

from these States (see table 5 and appendix 2).

26 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
4b

i 

Ul 

O

Uj 35 

D.

Z

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o

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o "

Ul In 20

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u_

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> 15

0

Z ui 10

o

Ul

E 5

r\

'

,

1 I 1 I 1 1 1 I 1 1 1 1 1 1 1 i i i i

A 1 i

I

B Disinfectant by-product

 Gasoline component 

D Solvent

E3 Refrigerant

1

 1

Fl

I

~

ilJiMillililiniriiH i i n i n i m i m

u.y

z 0.8 - 

Ul 

0

S 0.7

D.

Z

^ r\ o

Z

g

S 0.5 -

Ul

H 

"J 04 - Q v/.*+ 

U_

O

O

Z 

Ul

3 0.2

O 

Ul

tt m - u_ u.i

B

c

 

 

m

Solvent 

Gasoline component 

Organic synthesis co 

Fumigant 

Refrigerant

npound

_

-

1 " I

--------J---I-- 1 li

0.0 - Hit \ II

 6e oe oe oe oe -6e oe oe oe oe oe oe oe oe <P oe oe oe <^ oe oe oe -6e oe oe oe oe oe <? <?<?<& oe oe

"* N^ N^

Figure 4. Frequency of detection of volatile organic compounds at concentrations equal to or exceeding 1.0 microgram per liter in drinking water from randomly selected community water systems in the study area for (A) 20 

volatile organic compounds with detection frequencies greater than 1 percent, and (B) 34 volatile organic 

compounds with detection frequencies less than 1 percent. (Number of community water systems with analyses 

varies by compound; see appendix 3.)

Occurrence and Distribution of VOCs in Drinking Water 27
Table 11 . Randomly selected community water systems in the study area reporting concentrations at or above 

1.0 microgram per liter for 54 selected volatile organic compounds in drinking water by State, source of water, and 

population served, 1993-98

[Both includes community water systems (CWS) supplied by ground-water and surface-water sources; , no CWSs in this category]

Number of randomly selected CWSs reporting concentrations of selected 

volatile organic compounds at or above 1.0 microgram per liter

Principal source of water

State

Conn.

Del.

Maine

Md.

Mass.

N.H.

N.J.

N.Y.

Pa.

R.I.

Vt.

Va.

Total

(percent)

Ground 

water

33

13

17

28

33

34

66

123

52

12

20

50

481

(28)

Surface 

water

1

1

3

6

9

9

10

83

31

2

7

41

203

(75)

Both

8

0

5

20

6

7

31

15

4

6

9

111

(74)

More 

than 

50,000

2

1

1

5

4

6

6

2

4

31

(100)

Population served

3,301 

to 

50,000

8

0

2

6

38

6

36

53

38

6

3

19

215

(79)

501 

to 

3,300

7

3

4

10

6

15

18

80

24

2

10

30

209

(50)

25 

to 

500

25

10

14

22

13

28

25

98

30

8

20

47

340

(24)

Total

42

14

20

39

62

49

83

237

98

18

33

100

795

(38)

Percentage of 

CWSs

35

30

25

39

59

37

68

44

22

60

38

33

38

Table 12. Comparison of the frequency of detection of volatile organic compounds at concentrations at or above 

1.0 microgram per liter in drinking water from randomly selected community water systems in the study area by 

source of water and size, 1993-98

[|ig/L, micrograms per liter; MTBE, methyl tert-buty\ ether. Both includes water systems that have ground-water and surface-water sources;

very large= more than 50,000 people served; large = 3,301 to 50,000 people served; medium = 501 to 3,300 people served: small = 25 to 500 people

served]

Frequency of detection at or above 1 .0 |ag/L

Source - size category

Ground water - very large

Ground water - large

Ground water - medium

Ground water - small

Surface water - very large

Surface water - large

Surface water - medium

Surface water - small

Both - very large

Both - large

Both - medium

Both - small

Any volatile 

organic 

compound

100

73

40

22

100

84

68

67

100

83

64

57

Trihalomethanes1

100

57

36

20

100

90

88

86

100

90

85

73

Non-trihalomethanes

100

56

23

12

31

18

10

10

82

29

27

19

MTBE

50

13

6.3

7.3

0

2.2

5.7

0

75

16

0

8.3

^ot adjusted for missing data.

28 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 13. Comparison between average population density and the frequency of detection of volatile 

organic compounds at concentrations at or above 1.0 microgram per liter in drinking water in the 

study area, 1993-98

[Population density is statewide average for 1995 from Grady and Casey, 1999. table 2]

State

New Jersey

Rhode Island

Connecticut

Massachusetts

Maryland

New York

Delaware

Pennsylvania

Virginia 1

New Hampshire

Vermont

Maine

Population 

density 

(people per 

square mile)

911

641

591

575

406

333

288

262

167

123

61

35

Rank of detection 

frequency 

for any volatile 

organic compound

1

2

8

3

5

4

10

12

9

7

6

11

Rank of detection 

frequency for 

non-trihalomethane 

volatile organic 

compounds

2.5

1

4

2.5

7

10

8

9

12

5

11

6

Includes District of Columbia

A statistical analysis was performed to determine if the frequency of detection of VOCs in drinking 

water at concentrations equal to or exceeding 1.0 |J.g/L 

was related to urban land use. For this analysis, those 

areas with population density equal to or greater than

o

1,000 people per mi were considered urban. Locations 

of drinking-water sources were compared to digital 

data on 1990 population density with a l-km2-resolution (Price and Clawges, 1999) for the 12-State area. 

CWSs were classified as urban if one or more of their 

sources were in areas with population density of 1,000 

people per mi2 (386 people per km2) or more. A total 

of 263 of the 2,110 randomly selected CWSs were 

determined to have one or more source in an urban 

area. The remaining 1,847 CWSs had no known 

sources in areas with population density equal to or 

greater than 1,000 people per mi2 and were classified as 

rural. It is also important to note that no information 

was available to allow any systematic interpretation of 

which aquifer system was tapped by the ground-water 

sources, what the direction of ground-water flow may 

have been, or the extent of the area contributing flow to 

the well. It is very likely that some ground-water 

sources tapped confined aquifers that are isolated from 

the overlying land use, that the direction of groundwater flow may not be from urban areas adjacent to 

wells, or that the contributing areas for wells tapping

rj

surficial aquifers may be much smaller than the 1-km - 

resolution land-use categories.

The frequency of detecting any VOCs at any 

reporting level was more likely in urban areas than in 

rural areas (fig. 5); 67 percent of the urban CWSs 

verses 42 percent of the rural CWSs had detections. At 

a reporting level of 1.0 |ag/L, the VOC detection 

frequency was 1.8 times greater in CWSs with sources 

in high-population density, urban areas than in CWSs 

with sources only in rural areas (table 14). A 2-by-2 

contingency-table test rejected the null hypothesis that 

detection frequency was independent of population 

density at a very high level of significance (p<0.0001). 

A similar analysis was performed using the frequency 

of detection of non-trihalomethane (non-THM) VOCs 

(fig. 6) to evaluate the effects of population density on 

VOC occurrence without masking the relation with the 

widespread presence of disinfectant by-products. The 

frequency of detecting non-THM VOCs at concentrations equal to or exceeding 1.0 |J.g/L in drinking water 

from CWSs with urban sources was 2.5 times that of 

CWSs with only rural sources, and the attained significance level was similarly high (p<0.0001). The relation 

of urban land use to non-THM VOC occurrence also 

was largely independent of reporting level.

Occurrence and Distribution of VOCs in Drinking Water 29
80° 78° 76° 74° 72° 70° 68° 66° 64°

48°

46°

44°

42°

40C

38C

'.lVO«'-.'\£>''£i

.;. vv " *: * V;4&2

EXPLANATION

AREA WHERE POPULATION EQUALS 

OR EXCEEDS 1,000 PEOPLE 

PER SQUARE MILE

SOURCES FOR CWSs WITH VOC

DETECTIONS 

Ground-water source 

Surface-water source

SOURCES FOR CWSs WITHOUT

VOC DETECTIONS 

Ground-water source 

Surface-water source

Base from U.S. Department of Commerce digital data 1:100,000, 1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 5. Drinking-water sources for randomly selected community water systems in the study area, showing 

systems with analytical data and systems with reported detectable concentrations of any volatile organic compound, 

in relation to urban land use.

30 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
80° 78° 76° 74° 72° 70° 68° 66° 64°

48C

46°

44C

42°

40°

38°

Kfe-A. %* A*T*: u^4T.ie " ? * \ "1*^ JkW%^§ ^4vx v^v^p^|a t-^^^iSifi®1

?S£? -&

EXPLANATION

AREA WHERE POPULATION EQUALS 

OR EXCEEDS 1,000 PEOPLE 

PER SQUARE MILE

SOURCES FOR CWSs WITH NON-THM

VOC DETECTIONS 

Ground-water source 

Surface-water source

SOURCES FOR CWSs WITHOUT NONTHM VOC DETECTIONS 

Ground-water source 

Surface-water source

Base from U.S. Department of Commerce digital data 1:100,000, 1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 6. Drinking-water sources for randomly selected community water systems in the study area, showing 

systems with analytical data and systems with reported detectable concentrations of any non-trihalomethane volatile 

organic compound, in relation to land use.

Occurrence and Distribution of VOCs in Drinking Water 31
Table 14. Relations between the occurrence of volatile organic compounds at or above 1.0 microgram per liter 

and at concentrations that equal or exceed a drinking-water regulation or recommendation in drinking water 

from randomly selected community water systems in the study area and source of water, size of system, and 

land use at sources

[CWSs, community water systems; THM, trihalomethane; VOC, volatile organic compound; MTBE, methyl tert-butyl ether; factors with 

statistical populations that share the same letter symbol are not significantly different at a = 0.05 based on contingency-table tests; >, greater than]

Frequency of detection at or above 1 .0 microgram per liter

Factor

Source of water

Size of system 

(population 

served)

Land use at 

sources

Ground water 

Surface water 

Both

25 to 500 

501 to 3,300 

3,301 to 50,000 

> 50,000

Rural only 

Urban or mixed

Percentage of 

CWSs with 

any VOC 

(statistical 

population)

28 (A) 

75 (B) 

74 (B)

24 (A) 

50 (B) 

79 (C) 

100 (D)

34 (A) 

63 (B)

Percentage of 

CWSs with 

THMs1 

(statistical 

population)

26 (A) 

87 (B) 

89 (B)

30 (A) 

55 (B) 

76 (C) 

100 (D)

36 (A) 

62 (B)

Percentage of 

CWSs with 

non-THM VOCs 

(statistical 

population)

17 (A) 

14 (A) 

31 (B)

12 (A) 

20 (B) 

37 (C) 

58 (D)

15 (A) 

37 (B)

Percentage of 

CWSs with 

MTBE 

(statistical 

population)

7.8 (A) 

2.6 (A) 

16 (B)

7.0 (A) 

5.5 (A) 

10 (A) 

36 (B)

5.9 (A) 

20 (B)

Percentage of CWSs 

with any VOC equal to 

or exceeding a 

drinking-water 

regulation or 

recommendation

3.8 (A) 

15 (B) 

15 (B)

2.3 (A) 

7.4 (B) 

20 (C) 

36 (D)

4.7 (A) 

16 (B)

Not adjusted for missing data.

As with the occurrence of most of these 

compounds, the distribution of CWSs that have 

reported VOCs at or above drinking-water regulations 

or recommendations is significantly related to urban 

areas with high population density. A contingencytable test for the hypothesis that exceedance of 

drinking-water regulations or recommendations is 

independent of population density was rejected at 

p<0.0001. Fifteen percent of the CWSs that reported 

concentrations of one or more VOC that equaled or 

exceeded a drinking-water regulation or recommendation had sources in urban areas compared to about 5 

percent of the CWSs that only have sources in rural 

areas. Also, the propensity for the exceedances to occur 

for systems that serve large populations from multiple 

ground- and surface-water sources, which are more 

prevalent in urban areas, was observed (table 14).

An additional element of concern about the 

occurrence of VOCs in drinking water is the extent to 

which VOCs co-occur in water samples. Recent 

evidence indicates that exposure to even low levels of 

some contaminants may be linked to adverse biological 

effects including chemical sensitivity, endocrine 

disruption, and cancer (Ashford and Miller, 1998). 

Concern has been raised about the possible synergistic

effects of co-occurring multiple contaminants in 

drinking water. The review of data on VOCs in drinking 

water in the 12-State area indicates that two or more 

compounds co-occur in more than half of the samples 

with VOC detections. Although most of the time the 

number of VOCs reported in any sample is three or 

fewer compounds, 12 percent of the samples with VOC 

detections contained four or five compounds, and about 

3 percent contained five or more VOCs (fig. 7).

A tabulation of the percent co-occurrence for the 

64 VOCs detected at any concentration in drinking 

water in the study area is shown in appendix 4. The 

appendix lists 184 pairs of VOCs with co-occurrence of 

20 percent or more; 82 paired VOCs exhibit co-occurrence of 50 percent or more. Co-occurrence may occur 

when several VOCs have a common source, for 

example, the presence of the several trihalomethanes in 

a drinking-water sample may likely be related to disinfection. By contrast, the co-occurrence of multiple 

VOCs, often including MTBE, chloroform and (or) 

other trihalomethanes, and several common solvents, 

does not necessarily imply a common source for these 

contaminants, but rather may be an artifact of their 

overlapping, widespread occurrence.

32 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
100

CO

z

CO O

UJ C2

< UJ

CO O

DC 

UJ

90

80

9 70

6

Q- 60

PS 50

Q <

40

LJJ O 

CD LU 30

< =!

DC > 

UJ

20

10

1 2 or 3 4 or 5 5 or more 

NUMBER OF VOLATILE ORGANIC COMPOUNDS 

DETECTED PER SAMPLE

Figure 7. Frequency of co-occurrence of volatile organic 

compounds in drinking-water samples from randomly 

selected community water systems in the study area.

A more detailed discussion of the occurrence, 

co-occurrence, and distribution of the various types of 

VOCs in drinking water in the 12-State area follows. 

VOCs that may be related with regard to their principal 

use and (or) potential sources have been grouped for 

this discussion. Relations between VOC occurrence 

and distribution and some anthropogenic factors are 

evaluated and estimates of the number of people 

exposed to VOCs in their drinking water are presented.

Disinfectant By-Products

Disinfection of drinking water is necessary to 

prevent disease caused by waterborne pathogens in 

public drinking water; however, the disinfectants can 

react with naturally occurring materials (humic acids) 

in source water and distribution systems to form unintended by-products (Pomes and others, 1999). Four

THM compounds chloroform, bromodichloromethane, chlorodibromomethane, bromoform are 

among the by-products often generated by the most 

commonly used process (chlorination) to disinfect 

drinking water. One or more of these four compounds 

were detected in drinking-water samples frorr nearly 

half of the randomly selected CWSs in the 12-State 

region during 1993-98 (see fig. 4A and table 9).

It is a general requirement under the SDWA that 

all surface-water supplied CWSs, and those CWSs 

supplied by ground water under the direct infhience of 

surface water1 , must disinfect their water. CWSs exclusively supplied by ground water do not need to disinfect their water unless it is a State requirement that they 

do so. Even where disinfection of ground water is 

required or practiced, the levels of humic substances 

that react with chlorine are generally much lower in 

ground water than in surface water. Consequently, 

there is a large difference in the occurrence of THMs in 

drinking water when the source of water is considered 

(table 14). Nearly 90 percent of the CWSs supplied by 

surface water (either exclusively or in combination 

with ground-water sources) reported THM concentrations at or above 1.0 (ig/L, whereas only 26 percent of 

systems exclusively supplied by ground-water reported 

similar THM concentrations.

THM occurrence was similarly skewed to larger 

systems (table 14), as 100 percent of the 31 randomly 

selected CWSs that serve more than 50,000 people 

reported THM concentrations at or above 1.0 (ig/L. 

The large CWSs are more often supplied by surfacewater sources 87 percent of systems serving more 

than 50,000 people and 59 percent of systems serving 

3,301 to 50,000 people have surface-water 

sources whereas only 37 percent of the systems 

serving 501 to 3,300 people and 6 percent of those 

serving 25 to 500 people have surface-water sources. 

The frequency of THM detections for the 12-State area 

is likely to be positively biased by the lack of data for 

most (88 percent) of the CWSs in Pennsylvania and for 

about one-third of the systems in New York. In particular, 86 percent of the 562 CWSs in these two States

L'Any water beneath the surface of the ground with (1) significant occurrence of insects or other macroorganisms, alfae, or 

large-diameter pathogens such as Giardia lamblia or, (2) significant and relatively rapid shifts in water characteristics such as turbidity, temperature, conductivity, or pH which closely correlate to 

climatological or surface-water conditions." (U.S. Environmental 

Protection Agency, 1994)

Occurrence and Distribution of VOCs in Drinking W-*ter 33
that are missing THM data are ground-water supplied, 

and 76 percent of the systems missing data serve 25 to 

500 people. The bulk of the CWSs without THM data, 

therefore, are among the source and size categories that 

have comparatively low THM detection frequencies.

Chloroform was the most frequently detected 

VOC in drinking water in the study area at the 1.0 Jig/L 

reporting level, regardless of source-water type. Chloroform has been consistently one of the most frequently 

detected VOCs in ambient waters in the 

Nation reported in 64 percent of surface-water 

samples from about 12,000 locations (Staples and 

others, 1985) as well as detected in about 8 percent of 

2,943 wells (Squillace and others, 1999). Chloroform 

detections in surface waters are generally attributed to 

upstream discharges of industrial wastewater and 

sewage-treatment plant effluents (Stangroom and 

others, 1998), but ground-water detections are partly 

attributed to infiltration of chlorinated drinking water 

from lawn and garden irrigation and leaky water mains 

or sanitary sewers in urban areas (Squillace and others, 

1999). Consequently, some of the low level chloroform 

(or other THM) detections in drinking water in the 12- 

State region may be attributed to the occurrence of 

THMs in source waters rather than within-system chlorination by CWSs.

Total THM concentrations (the calculated sum of 

chloroform, chlorodibromomethane, bromodichloromethane, and bromoform concentrations) in 5,850 

drinking-water samples with THM detections ranged 

from 0.1 to 425 jiig/L. Concentrations in 186 drinkingwater samples (3 percent of samples with THM detections at any reporting level) from 46 CWSs equaled or 

exceeded the 100-jiig/L MCL (U.S. Environmental 

Protection Agency, 1996). The THM MCL requires 

that the average annual THM concentration in drinking 

water provided by a water system to be less than 100 

jiig/L, and thus, it does not strictly apply to individual 

water samples. The number of samples and systems 

reporting THM concentrations that equal or exceed the 

lOO-jiig/L MCL is small, considering the more than 

15,000 drinking-water samples from 1,543 CWSs 

analyzed for THMs. The collective population served 

by these 46 CWSs, however, totals 877,021 or about 9 

percent of the population served by the set of randomly 

selected CWSs in the 12 States. Because of concerns 

that some THMs are probable human carcinogens 

(Morris and others, 1992; King and Marrett, 1996) and 

may have other deleterious effects on human health 

(Waller and others, 1998; Klotz and Pyrch, 1999), the

USEPA, under the 1996 Amendments to the SDWA, 

will reduce the total THM MCL to 80 \ig/L in 2001 and 

will reduce it further to 40 jiig/L in 2005 (U.S. Environmental Protection Agency, 1998e). Reductions in THM 

concentrations in drinking water are planned by 

decreasing the amount of residual chlorine reouired to 

remain in drinking water as it moves from the treatment 

plant through the distribution system to water 

consumers. Comparing the THM concentrations 

observed during this study to the planned MCLs indicates that about 8 percent of the samples would exceed 

the 80-jiig/L MCL, and about 30 percent of the samples 

would exceed the 40-jiig/L MCL. Lower THM concentrations are anticipated, however, if residual chlorine 

levels are decreased in the future.

Median detected total THM concentrations for 

702 randomly selected CWSs that reported detectable 

THMs are compared in figure 8 by source of water. The 

detected THM concentrations differed significantly 

(Kruskal-Wallis test p <0.0001) for CWSs supplied by 

ground water, surface water, or both ground- and 

surface-water sources. The median THM concentration 

for the 390 CWSs exclusively supplied by ground 

water (2.5 jiig/L) was significantly less than median 

concentrations for the CWSs exclusively supplied by 

surface water (30.3 jiig/L) and for CWSs supplied by 

both sources (19.9 jiig/L). A statistically significant 

difference was also evident for the median THM 

concentrations between the CWSs exclusively supplied 

by surface water and those CWSs supplied b)r both 

sources. Median total THM concentrations for seven 

CWSs (six of these were exclusively surface-water 

supplied) exceeded the current (2000) 100-jiig/L MCL.

Among the four THM compounds, the relative 

frequency of detection (table 15) was chloroform>bromodichloromethane>chlorodibromomethanobromoform, which conforms with the 

ratio of chlorine-to-bromine atoms in each compound. 

Although bromine is used in some disinfection 

processes, the occurrence of the brominated 

compounds in some drinking water probably results 

from bromine impurities in the chlorine used in the 

most common disinfection process (Bellar an-i others, 

1974). For the 702 CWSs with detectable THM 

concentrations in the study area, chloroform (CHC^) 

was reported in 84 percent, bromodichlorometfiane 

(CHBrCl2) in 69 percent, chlorodibromometl ane 

(CHBr2Cl) in 55 percent, and bromoform (CFBr3 ) in 

28 percent.

34 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
1 ,UUU

700

500

400

300

QC

LLJ 200

t

QC -mo

UJ IUU

°- 70

CO

 5 50

< 40

o QC on30

O 20

QC ^U

O

5 10

z

 7

C0~ c

HI 5

Z 4

< 3

UJ 2

^

O

^ 1

^ 0.7

^ i_ 0.5 OR

_l 0.4

j< 0.3

o

I- 0.2

0.1

0.07

0.05

0.04

0.03

0.02

0.01 

;_ (390) (111) (201) ;

§

-

^F

B

: A

* H

3fc w

~~ M ^ v ^ s - y |

(

|

 

^

if1^-

\/ sV

_ ~ *

I I * *

JR ^ "^F"

r W * -^k"

 ^

1

1 t

p<0.0001 (attained significance level)

Populations that share the same letter symb

are not significantly different at the 95-perce

confidence level

-

-

-

-

_

-

:

-

_

-

-

-

.

-

-

-

.~

-

-

-

-

-

-_

-

-

-

~

-

-_

-

-

_

ol

nt

:

i

Ground Both ground water Surface

water and surface water water

(390) 

A

SOURCE OF WATER

EXPLANATION

NUMBER OF OBSERVATIONS 

POPULATION

DATA VALUES OUTSIDE THE 

10TH AND 90TH PERCENTILES

90TH PERCENTILE 

75TH PERCENTILE 

MEDIAN

25TH PERCENTILE 

10TH PERCENTILE 

 MAXIMUM CONTAMINANT LEVEL

Figure 8. Distribution of median total trihalomethane concentrations in drinking water from randomly selected 

community water systems in study area compared by source of water.

Occurrence and Distribution of VOCs in Drinking W^ter 35
Table 15. Frequency of detection and median concentrations of trihalomethanes in drinking water f-om 

randomly selected community water systems in the study area compared by source of water

Frequency of detection

(percentage of community

water systems)

Median concentration 

(micrograms per liter)

Trihalomethane

Total trihalomethanes

Chloroform

Bromodichloromethane

Chlorodibromomethane

Bromoform

Ground 

water

32

26

20

19

12

Surface 

water

91

89

81

47

13

Both

91

87

77

57

21

Ground 

water

2.5

1.6

1.2

1.0

1.1

Surface 

water

30

24

4.0

1.5

0.8

Both

20

17

3.7

1.4

1.2

The THM compounds have high co-occurrence 

among themselves (table 16) as well as broad, lowlevel co-occurrence with other VOCs (appendix 

4) only 8 rarely detected VOCs among the 64 VOCs 

reported in drinking water in the study area have not cooccurred at least once with a THM compound. For this 

report, co-occurrence is calculated as the ratio of the 

number of times a less frequently detected compound 

occurred to the number of times the more frequently 

detected compound occurred (when both compounds 

were measured in the same sample), multiplied by 100 

to express the value in percent. For example, bromodichloromethane was detected 2,656 times with 3,758 

chloroform detections, and consequently bromodichloromethane co-occurs with 71 percent of the chloroform

detections. Generally, if the percentage co-occurrence 

among VOCs exceeds 20 percent, the compounds are 

thought to be related in the water sample, possibly 

because they may come from the same source. Cooccurrence was greater than 20 percent for 10 of the 12 

possible THM pairs and was greater than 50 percent for 

8 THM pairings. The high degree of co-occurrence 

among THM compounds is a reflection of the fact that 

they are commonly generated through the act of chlorinating unprocessed drinking-water. The broad lowlevel (less than 10 percent) co-occurrence of most 

VOCs with THMs is not related to a commor source 

but rather reflects the nearly ubiquitous distribution of 

THMs in drinking water.

Table 16. Co-occurrence of trihalomethane compounds in drinking water from randomly selected community 

water systems in the study area

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of 

compound specified by row; co-occurrence values equal to or greater than 20 percent are shown in bold; NA, not applicable]

Co-occurrence, in percent

Trihalomethane

Chloroform

Bromodichloromethane

Chlorodibromomethane

Bromoform

Chloroform

NA

71

42

12

Bromodichloromethane

95

NA

61

18

Chlorodibromomethane

84

89

NA

33

Bromoform

58

68

83

NA

36 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
MTBE and Other Gasoline Components

The gasoline additive MTBE was the sixth most 

frequently detected VOC contaminant in drinking 

water from randomly selected CWSs in the Northeast 

and Mid-Atlantic regions during 1993-98. MTBE was 

detected in 343 drinking-water samples from 106 

CWSs in the region at concentrations ranging from 

0.26 to 210 jilg/L. The lack of any MTBE data for Delaware and Pennsylvania meant that a total of 1,194 

CWSs, or just more than half of the 2,110 randomly 

selected CWSs, have analyzed for MTBE; the MTBE 

data included 5,510 analyses of drinking-water 

samples at reporting levels that ranged from 0.1 to 

10 jag/L. After the trihalomethane compounds, MTBE 

was the most frequently detected VOC, detected in 

8.9 percent of 1,194 randomly selected CWSs that 

sampled for MTBE at any reporting level and in 

7.8 percent of 1,074 CWSs that sampled for MTBE at 

the 1.0 |ig/L level during 1993-98. MTBE was more 

frequently detected than all other non-THM VOCs at 

all reporting levels (see appendix 3), and at reporting 

levels of 10 and 20 jag/L, the frequency of MTBE 

detections exceeded that of bromoform, the least 

commonly detected trihalomethane.

Although MTBE was detected in drinking water 

from all 10 States in the region that have analytical 

data, the frequency of detection at 1.0 |ilg/L differed 

significantly (contingency-table test p < 0.0001)

(fig. 9). With detections reported by 21.5 percent of 

randomly selected CWSs with data for MTBE, New 

Jersey reported the greatest frequency of MTBE in 

drinking water at concentrations at or above 1.0 jilg/L, 

and Virginia (1.3 percent) reported MTBE least 

frequently. The frequency of detecting MTBE in 

drinking water at or above 1.0 jilg/L was significantly 

greater in New Jersey than in Maryland, New York, 

Vermont, and Virginia. The States with the highest 

MTBE detection frequencies New Jersey, Fhode 

Island, and Connecticut are the three States with the 

highest average population density (see table 13). As 

previously shown for any VOC and non-THM VOCs, 

the occurrence of MTBE also can be statistically 

related to population density. Twenty percent of the 

CWSs that have one or more sources in urban areas 

(population density equal to or greater than 1,000 

people per mi2) reported detecting MTBE at the 1.0 

jag/L reporting level, whereas less than 6 percent of 

CWSs with no sources in urban areas contained the 

gasoline additive (table 14). A contingency-table test 

for this 3-to-l distribution rejects the null hypothesis 

that MTBE detections are independent of population 

density at p <0.0001. This association of MTBE detections in ambient ground waters with urban areas also 

was observed by Squillace and others (1999) from data 

largely collected from shallow monitoring wells, as 

well as by the State of Maine (1998) with data from 

domestic and public supply wells.

p<0.0001 (attained significance level) 

Populations that share the same letter symbol 

are not significantly different at the 95-percent 

confidence level

111

Conn. Mass. Md. Maine N.H. N.J. N.Y. R.I. Vt.

Figure 9. Frequency of detection of methyl tert-butyl ether at or above 1.0 microgram per liter in drinking water 

from randomly selected community water systems in 10 Northeast and Mid-Atlantic States, 1993-98. (Populations 

that share the same letter symbol are not significantly different at the 95-percent confidence level; p = the attained 

significance level.)

Occurrence and Distribution of VOCs in Drinking W*ter 37
New Jersey, Rhode Island, and Connecticut 

share another characteristic that has greater bearing on 

the occurrence of MTBE in drinking water than does 

population density. These three States, as well as 

Massachusetts (and Delaware), use substantial 

amounts of MTBE (greater than 5 percent by volume) 

in OXY/RFG program areas that extend throughout the 

entire State. The extent of the OXY/RFG-use areas also 

includes (or did include for some part of the 1993-98 

period) parts of Maine, New Hampshire, New York, 

Pennsylvania, Maryland, and Virginia (fig. 10). The 

distribution of sources for CWSs that have been 

sampled for MTBE and those that have reported MTBE 

detections also is shown in figure 10. The frequency of 

detection of MTBE in drinking water is more than five 

times greater in the OXY/RFG-use areas for any 

reporting level, and is seven times greater for concentrations at or above 1.0 |ig/L, than in the remaining no 

or low MTBE-use areas. The elevated frequency of 

MTBE detections in the OXY/RFG areas are statistically greater (contingency-table test p<0.0001) than 

detections in low MTBE-use areas. MTBE concentrations, however, were not significantly different for 

systems in or out of OXY/RFG-use areas (Wilcoxon 

rank-sum test p = 0.3177). The median detected MTBE 

concentration for the 89 CWSs inside OXY/RFG areas 

with MTBE detections was 1.3 |Llg/L, whereas the 

median detected MTBE concentration for the 17 CWSs 

with detections that are outside of OXY/RFG areas was 

2.0 |ig/L.

MTBE was detected at or above 1.0 |ig/L in 7.8 

percent of CWSs supplied exclusively by ground-water 

sources and in 2.6 percent of those supplied exclusively 

by surface-water sources, but the CWSs that use both 

sources had the most frequent MTBE detections (16 

percent). Presumably, this may reflect the propensity 

for larger systems in urban areas to have both surfaceand ground-water sources, combined with the association of MTBE with urban sources. MTBE detections in 

drinking water from smaller CWSs that serve predominantly small rural populations were less frequent (but 

still notably about 6 to 7 percent) than the 36 percent of 

CWSs that serve more than 50,000 people in urban 

areas (table 14). The frequent and widespread detection 

of MTBE in drinking water within a short time (6 

years) following its introduction into much of the 

region in substantial amounts (greater than 5 percent by 

volume) as a gasoline oxygenate reflects its chemical 

characteristics (high solubility, low soil adsorption, and

low biodegradability) together with its large r umbers 

and variety of potential sources.

Fortunately, although MTBE detections may be 

relatively numerous, as with most other VOCs detected 

in drinking water, concentrations have been generally 

low. Only 8 percent of the 343 reported MTBE detections andO.8 percent of 1,194randomly selected CWSs 

with data for MTBE have equaled or exceeded the 20- 

|ig/L lower limit recommended by USEPA, and just 2 

percent of the CWSs reported concentrations at or 

above the California 5-|ig/L taste and odor threshold. 

Median detected MTBE concentrations in drinking 

water for the 106 CWSs reporting MTBE detections 

were less than 1.0 |ig/L about 40 percent of tH time 

and less than 10 |ig/L 90 percent of the time.

Information on the concentration of MTBE in 

drinking water was obtained for additional PWSs other 

than the 1,194 randomly selected CWSs during data 

compilation efforts for this study. Because of the keen 

interest in all available information on the occurrence 

and distribution of MTBE in drinking water, these data 

were reviewed and are described here. They are not 

used, however, in any data analysis or projections made 

for this report because they are largely limited to those 

States (Maine, Maryland, New Jersey, Rhode Island, 

and Virginia) that provided more data than reiuested. 

Overall, 374 PWSs, including 106 of the randomly 

selected CWSs plus 268 other PWSs, have reported 

detectable concentrations of MTBE in 1,217 drinkingwater samples that range from 0.26 to 3,260 |Ug/L. 

Median concentrations for the additional 268 PWSs 

reporting MTBE detections were calculated c id 

compared to the subset of 106 randomly selected 

CWSs (fig. 11). MTBE concentrations in the ret of 268 

PWSs with MTBE data are slightly but significantly 

(Wilcoxon rank-sum test p = 0.0281) greater than in the 

randomly selected CWSs. This is likely an artifact of a 

biased distribution for the set of 268 PWSs with respect 

to why they were sampled for MTBE. It is known that 

samples for MTBE were intentionally collected at 

some PWSs where gasoline sources (gasoline stations, 

underground fuel storage tanks) were near water 

sources and gasoline contamination was known to 

occur nearby. Although a few of these systems may 

have been included in the randomly selected CWSs by 

chance, the random set of CWSs is representative of the 

population of CWSs in the 12-State area and less likely 

overstates the occurrence or concentrations of MTBE 

due to any potential sampling bias.

38 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
80° 78° 76° 74° 72° 70° 68° 66° 64°

48C

46°

44°

42°

40C

38°

^^. Jf\v /

"^-It;:

/*$« -

w .// 

 J i .. I'. <j-& ; *.-. . ..t«v . %, > y "»^_ # * . «^% .-* 

A ^11.< A * A - ^J%^ 

Al^^^'

EXPLANATION

AREA WHERE OXYGENATED AND (OR) 

REFORMULATED GASOLINE 

CURRENTLY OR FORMERLY 

USED

SOURCES FOR CWSs WITH MTBE

DETECTIONS 

Ground-water source 

Surface-water source

SOURCES FOR CWSs WITHOUT MTBE

DETECTIONS 

Ground-water source 

Surface-water source

Base from U.S. Department of Commerce digital data 1:100,000,1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 10. Drinking-water sources for randomly selected community water systems in the study area, showing 

systems with analytical data and those systems with reported detectable concentrations for methyl tert-butyl ether, 

in relation to areas where oxygenated and (or) reformulated gasoline is currently or was formerly used (U.S. 

Environmental Protection Agency. 1998c, 1998d).

Occurrence and Distribution of VOCs in Drinking Water 39
UJ

o 

cc

UJ 

D_

UJ

O

100

90

80

70

60

50

40

30

20

10

 Data for 106 randomly selected community 

water systems

----- Data for 268 public water systems

0.1 1 10 100

MEDIAN MTBE CONCENTRATION, IN MICROGRAMS PER LITER

1000

Figure 11. Comparison of cumulative distributions of median methyl tert-butyl ether concentrations detected in 

drinking water for randomly selected community water systems to selected public water systems in the study 

area.

In addition to MTBE, 12 other VOCs that have 

been commonly associated with gasoline sources also 

were detected in drinking water in the 12-State area 

(see table 9 and appendix 3). Among the gasoline 

components and other hydrocarbons associated with 

gasoline sources (see appendix 1) are benzene, toluene, 

ethylbenzene, and various xylene isomers (o-, m-, and 

/7-xylene summed in this report as "total xylenes") that 

are collectively referred to as BTEX compounds. Total 

xylenes and toluene were the most frequently detected 

gasoline compounds after MTBE, reported in 3.2 and 

2.5 percent of CWSs, respectively, at or above 1.0 jig/L 

(fig. 5); ethylbenzene (detected in 2.4 percent of CWSs) 

and benzene (detected in 0.8 percent of CWSs at or 

above 1.0 jig/L) followed. When compared with 

MTBE, each individual BTEX compound occurs less 

than half as frequently in drinking water, but collectively (that is, the frequency of detection of any BTEX 

compound) is comparable to MTBE 8.4 percent of 

the randomly selected CWSs detected BTEX at any 

reporting level and 5.8 percent of CWSs reported 

BTEX concentrations at or above 1.0 jig/L. The 

frequency of detecting any BTEX compound was 

greater in the OXY/RFG-fuel areas (11 percent of 

CWSs at any reporting level) than non-OXY/RFG 

areas (8 percent of CWSs), but the difference is much 

smaller than for MTBE. This observation is considered

to be an artifact of the fact that, as with other VOCs, 

BTEX is associated with urban areas with high population density (p<0.0001) and, in general, there is an 

autocorrelation between the OXY/RFG-fuel areas and 

urban areas in the 12-State area.

Although BTEX has been relatively widely 

detected in drinking water, and a few additional gasoline components (naphthalene, n-butylbenzene, and 

1,3,5-trimethylbenzene) have been detected more 

rarely, these compounds generally do not co-occur in 

drinking water with MTBE. Co-occurrence of BTEX 

and other specific gasoline components with MTBE 

ranged from 0 to 2.7 percent (table 17), and only 9 of 

1,191 of CWSs (0.8 percent) reported such co-occurring detections. Co-occurring detections of any BTEX 

compound with MTBE were reported in only 12 of the 

5,406 drinking-water samples (0.2 percent) that were 

analyzed for both VOCs (fig. 12). Also, co-occurring 

detections at concentrations greater than 20 jig/L, 

which might indicate contamination from a nearby 

gasoline point source (Moran and others, 1999), were 

rare. Only 3 samples among the 464 drinking-water 

samples plotted in figure 13 that contained MTBE, one 

or more BTEX compounds, or both VOCs, had concentrations of MTBE and BTEX greater than 20 jig/L, and 

all 3 samples were collected from a single CWS.

40 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 17. Co-occurrence of gasoline components in drinking water from randomly selected community water systems in the 

study area

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound specified by 

row; co-occurrence values equal to or greater than 20 percent are shown in bold; NA, not applicable; ND, not determined because less than 10 detections of 

compound specified by column]

Co-occurrence, in percent

Gasoline 135 

component MTBE Ben2ene Ethyl- To,uene Total ,>Butyl- ^J

benzene xylenes benzene . benzene

MTBE NA 26 5.7 2.7 11 ND ND

Benzene 2.4 NA 3.7 7.1 7.6 0 0

Ethylbenzene 0.6 5.8 NA 23 47 4.5 8.7

Toluene 0.6 17 37 NA 27 4.5 4.3

Xylenes, total 2.7 25 73 33 NA ND ND

Naphthalene 0.7 2.5 1.9 1.1 1.5 ND ND

n-Butylbenzene 0 0 1.8 0.9 0 NA 70

1,3,5-Trimethylbenzene 0 0 3.5 0.9 6.3 73 NA

1,000

100 

DC 

- UJ

BTEX CONCENTRATIO IN MICROGRAMS PERLI

o 

b P-L

P 10 -^ -L - 

<-»

Data for 464 samples 

MTBE minimum repo 

BTEX minimum repo 

All nondetects coded

with MTBE or BTEX detections 

rting levels = 0.26 micrograms per liter 

ling levels = 0.15 micrograms per liter 

as 0.09 micrograms per liter for plotting purposes

/^

* *

^^

J^

/^

>+ +

1 0.1 1 10 100 1,000

MTBE CONCENTRATION, IN MICROGRAMS PER LITER

Figure 12. Comparison of methyl te/t-butyl ether (MTBE) concentrations to the sum of the concentrations of 

benzene, ethylbenzene, toluene, and xylenes (BTEX) in drinking-water samples from randomly selected comrr unity 

water systems in the study area. (Data for 464 samples with MTBE or BTEX detections; minimum reporting levels 

= 0.26 micrograms per liter (ug/L) for MTBE and 0.15 ug/L for BTEX; all nondetects coded as 0.09 ug/L for plotting 

purposes.)

Occurrence and Distribution of VOCs in Drinking Water 41
Co-occurrence among the other gasoline components detected in drinking water (table 17, appendix 4) 

was generally more extensive. Associations between 

two pairs of gasoline components total xylenes with 

ethylbenzene, and 1,3,5-trimethylbenzene with nbutylbenzene were observed more than 70 percent of 

the time. Associations of other gasoline contaminants 

also were observed in drinking-water samples, with cooccurrence exceeding 20 percent for ethylbenzene with 

toluene and total xylenes, toluene with total xylenes, 

and total xylenes with benzene.

The question can be raised as to why MTBE, 

which is widely detected in drinking water, does not 

generally co-occur with other gasoline contaminants, 

which have also been reported at comparable detection 

frequencies, particularly because they have often been 

found together in ground water at gasoline spills. It is 

possible that, because of the conservative transport 

properties of MTBE, some MTBE detections may 

represent the distal portions of gasoline contaminant 

plumes that may ultimately affect drinking-water 

sources, given sufficient time and stress on the aquifer 

(Johnson and others, 2000). A general consensus is that 

MTBE occurs without other gasoline contaminants 

because it is essentially recalcitrant relative to the 

highly biodegradable BTEX compounds. However, it 

is also possible that some BTEX or other gasoline 

contaminants may have been removed by water filtration or treatment processes where they may have been 

applied (although it is unlikely that such treatment 

processes would remove only BTEX and not remove 

MTBE). The lack of a substantial co-occurrence of 

MTBE with other gasoline components in drinking 

water, together with the generally low concentrations 

reported, indicates that most detections may not be 

caused by nearby gasoline point sources.

It is likely, given the variety of possible sources 

of MTBE other than leaking underground storage tanks 

(Delzer and others, 1996; Pankow and others, 1997; 

Baehr and others, 1999; Hunter, 1999; Moran and 

others, 1999; Robbins and others, 1999), that the bulk 

of the detections may have been derived from mobile, 

atmospheric, or other diffuse nonpoint sources that 

could produce low-level contamination of drinkingwater with MTBE without introducing other gasoline 

components in substantial amounts. The combination 

of multiple sources of MTBE together with its rather 

unique transport properties leads to the conclusion that 

the extent of contamination of drinking water from 

gasoline is substantially greater with the use cf MTBE 

than would have occurred had this oxygenate never 

been added to gasoline. It is also possible, given the 

widespread use of xylenes and toluene, particularly in 

numerous household and commercial products, that 

some BTEX detections in drinking water that occur 

without MTBE may represent sources for these chemicals other than fuels. In addition, toluene and xylenes 

have been noted in some drinking water systems 

following installation of water tank lining materials.

Although the co-occurrence of gasoline components is not extensive in drinking water, 44 percent of 

the 343 samples with MTBE detections contained at 

least one other VOC. Among the VOCs detected with 

MTBE, solvents were most prominent (accounting for 

58 percent of the co-occurring compounds), followed 

by trihalomethanes (about 33 percent of co-occurring 

compounds). BTEX compounds were a distant third, 

accounting for about 5 percent of all VOCs tl at cooccurred with MTBE, and about 4 percent were refrigerants, fumigants or other VOCs used mainly in the 

manufacture of organic chemicals (see appendix 4).

As a footnote to the occurrence of gascline 

components in drinking water in the 12-State area, the 

authors note that only one State had any data for any 

other gasoline oxygenate compound. The compound 

tert-amy\ methyl ether (TAME) was reportedly 

detected in eight drinking-water samples from three 

PWSs in Virginia in 1997 and 1998. TAME concentrations ranged from 0.6 to 19.1 |lg/L. MTBE also was 

reported in all eight of the drinking-water samples that 

contained TAME, and the MTBE concentrations were 

elevated at 6.2 to 387 (ig/L. The three PWSs were not 

among the randomly selected CWSs inventoried for 

this study, and no TAME data were available for the 

randomly selected CWSs. TAME also has been associated with MTBE in water samples collected from four 

lakes in New Jersey where the use of gasoline-powered 

watercraft is prevalent (Baehr and Zapecza, 1998).

42 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Solvents

Solvents were the third most frequently detected 

group of VOCs in drinking water in the 12-State area. 

Included among the VOCs classified as solvents for 

this report are several chemicals that are widely used in 

industrial, commercial, and residential applications and 

are frequent contaminants in ambient ground water 

(Squillace and others, 1999) and drinking water 

(Westrick and others, 1984; Mackay and Smith, 1993). 

Among the group of VOCs classified as solvents are 

toxic chemicals with potentially severe, well documented human health impacts, and drinking-water 

regulations have been promulgated for these contaminants (U.S Environmental Protection Agency, 1996).

Twenty-seven of 34 solvents sampled for in 

drinking water in the 12-State area have been detected 

at least once (see table 9), and 23 of these were detected 

at concentrations equal to or exceeding 1.0 [ig/L (see 

fig. 4). VOCs are classified as solvents (for this report) 

on the basis of their predominant use or most likely 

source as drinking-water contaminants. Three 

compounds widely used in industrial and commercial 

applications 1,1,1 -trichloroethane, trichloroethylene, 

and tetrachloroethylene were the most frequently 

detected solvents in drinking water, each reported in 

about 5 percent of the CWSs (table 9 and appendix 3). 

Collectively, solvents were detected in 3,080 drinkingwater samples, or about 17 percent of the nearly 18,000 

samples analyzed for one or more of these compounds, 

and in 34 percent of the 8,955 drinking-water samples 

with any VOC detection. Overall, the frequency of 

detecting a solvent VOC in drinking water was 14 

percent 304 of the 2,097 randomly selected CWSs 

that analyzed for solvents reported one or more of the 

27 solvents at any detectable concentrations in drinking 

water and 9.8 percent (206 of 2,097 CWSs) at the 1.0 

|ig/L reporting level.

The distribution of randomly selected CWSs that 

have reported detectable solvent concentrations is 

strongly associated with high population-density, urban 

areas (fig. 13). One-third of the CWSs that have one or 

more sources in an urban area reported solvent detections, compared to about 12 percent of CWSs that have 

no sources in urban areas. A contingency-table test for 

the hypothesis that solvent detections are independent 

of population density was rejected at p<0.0001. The 

frequency of solvent detections at or above 1.0 Jlg/L 

ranged from just 1.2 percent of CWSs in Vermont to

more than 20 percent of CWSs in Massachusetts, New 

Jersey, and Rhode Island (fig. 14). Detections of 

solvents at concentrations equal to or greater than 1.0 

|lg/L in 28 percent of CWSs in Massachusetts was 

significantly greater than in all eleven other States.

Most solvent concentrations were less than 5.0 

|ig/L, but eight of the solvents detected in drinking 

water were reported at concentrations that equaled or 

exceeded an MCL. About 3 percent of all trichloroethylene and tetrachloroethylene analyses indicated 

concentrations that were above MCLs in drinking 

water, and some concentrations have been more than 

100 times greater than the 5.0-|J,g/L MCLs. Concentrations as great as 930 Jlg/L of trichloroethylene and 640 

|lg/L of tetrachloroethylene have been reported, but 

nearly all of these high concentrations were reported by 

six CWSs. Concentrations of the other six 

VOCs carbon tetrachloride, 1,2-dichloroethane, 1,1- 

dichoroethene, c/s-l,2-dichloroethene, dichloromethane, and 1,2-dichloropropane have exceeded 

their MCLs in only a very small fraction of drinkingwater samples.

The extent of co-occurrence among solvents is 

greater than other groups of VOCs with the exception 

of the disinfectant by-products. Half (1,537) of the 

3,080 drinking-water samples with solvent detections 

contained more than 1 solvent VOC. Frequently, three 

to six solvents may co-occur in a drinking-water 

sample, with as many as eight compounds reported in a 

few samples. Among 10 of the most frequently 

detected solvents (table 18), 9 compounds co-occur 

with at least 1 other solvent 20 percent of the time or 

more, and the percentage of co-occurrence reaches as 

high as 87 percent of 1,1-dichloroethane detections 

with 1,1,1-trichloroethane. One reason for their 

frequent co-occurrence is that multiple solvents are 

often combined in the formulation of cleaning and 

degreasing agents, dry cleaning fluids, and other products containing solvents that have widespread industrial, commercial, or residential use. Another reason for 

their co-occurrence is that a number of the solvents, 

particularly cis- and fra«s-l,2-dichloroethene, 1,1- 

dichloroethene, and dichloromethane, are transformation products and degradates of parent solvent 

compounds, such as tetrachloroethylene, trichloroethylene, and 1,1,1-trichloroethane.

Occurrence and Distribution of VOCs in Drinking Water 43
80° 78° 76° 74° 72° 70° 68° 66° 64°

48°

46°

44°

42°

40°

38°

EXPLANATION

AREA WHERE POPULATION EQUALS 

OR EXCEEDS 1,000 PEOPLE 

PER SQUARE MILE

SOURCES FOR CWSs WITH SOLVENT

VOC DETECTIONS 

Ground-water source 

Surface-water source

SOURCES FOR CWSs WITHOUT

SOLVENT VOC DETECTIONS 

Ground-water source 

Surface-water source

Base from U.S. Department of Commerce digital data 1:100,000,1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 13. Drinking-water sources for randomly selected community water systems in the study area, showing 

systems with analytical data and systems with reported detectable concentrations of any solvents, in relation to 

urban land use.

44 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
p<0.0001 (attained significance level) 

Populations that share the same letter symbol 

are not significantly different at the 95-percent 

confidence level

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. Vt. Va.

Figure 14. Frequency of detection of solvents at or above 1.0 microgram per liter in drinking water from randomly 

selected community water systems in the study area, 1993-98.

Occurrence and Distribution of VOCs in Drinking Water 45
* =5

z <5o 5 a 8

<B 0) Q) 3 (0 Q.» 2

(D CO

ssn> =f <D 5'

co j«r 5'

to

m(D

Table 18. Co-occurrence of selected solvents in drinking water from randomly selected community water systems in the study area

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound specified by row;

co-occurrence values equal to or greater than 20 percent are shown in bold; NA, not applicable; ND, not determined because less than 10 detections of compound specified by column]

Co-occurrence, in percent

Solvent

Trichloroethylene

Tetrachloroethylene

1,1,1 -Trichlorethane

cis- 1 ,2-Dichloroethenetrans- 1 ,2-Dichloroethene

1 , 1 -Dichloroethane1,1-Dichloroethene

Carbon tetrachloride

Dichloromethane

1 ,2-Dichloroethane

Trichoroethylene

NA

593734

1.0

19

22

5.4

1.4

3.0

Tetrachloroethylene

61

NA

2929

1.1

18

20

5.5

0.9

2.6

1,1,1,- 

Trichloroethane

57

44

NA

27

0.9

3734

7.2

1.6

3.5

c/s-1 ,2- 

Dichloroethene

85

68

44

NA

1. 8

26

30

7.2

1.5

5.0

frans-1 ,2- 

Dichloroethene

6363

3744

NA

ND

15

7.4

3.7

3.7

1,1- 

Dichloroethane

67

618036

0

NA

55

5.4

0.93.0

1,1- 

Dichloroethene

82

738745

1.0

60

NA

14

2.45.1

Carbon 

tetrachloride

75

726539

1.7

2452

NA

4.2

5.8

Dichloromethane

19

1214

8.6

0.8

4.6

8.6

4.3

NA

6.0

1,2- 

Dichloroethane

42

34

32

29

0.8

12

20

6.06.0

NA
Other VOCs

In addition to disinfectant by-products, gasoline 

components, and solvents, other VOCs reported in 

drinking water in the 12-State area included 

compounds used mostly as fumigants, refrigerants, or 

in the manufacture of other chemicals. Collectively, 

these compounds were detected less frequently than the 

former groups of VOCs. but several were detected in 

more than 1 percent of the randomly selected CWSs at 

any reporting level (table 9), and the refrigerant dichlorodifluoromethane was detected in more than 1 percent 

of CWSs at concentrations equal to or above 1.0 |ig/L 

(see fig. 4).

Seven of the 84 VOCs represented in the 

drinking-water data (appendix 1) have been used as 

pesticide fumigants to destroy insects, bacteria, or 

rodents in agricultural fields and storage facilities and 

in some commercial, industrial or even residential 

settings. Five of the fumigant VOCs were detected in 

drinking water in the 12-State area and two of 

these dibromochloropropane (DBCP) and ethylene 

dibromide (EDB) were reported in almost 2 percent 

of the randomly selected CWSs (table 9). There is a 

strong degree of co-occurrence of DBCP and EDB in 

drinking water and both are present in more than 76 

percent of the 33 samples with detects of either. 

Concentrations of DBCP and EDB have exceeded the 

MCLs of 0.2 and 0.05 |lg/L, respectively, in a few 

randomly selected CWSs (see table 8). Although the 

frequency of fumigant detections is almost twice as 

great (4.2 percent) for CWSs with sources in urban 

areas than for CWSs with sources only in rural areas 

(2.5 percent), the difference is not statistically significant (contingency-table test p = 0.1594). Many fumigant detections were reported by CWSs in rural parts of 

Delaware, New York, Pennsylvania, and Vermont 

(fig. 15) where the chemicals may have had agricultural applications. EDB previously was used widely as 

a scavenger for lead in gasoline but the drinking-water

data indicated no co-occurrence of EDB with any gasoline components.

Three VOCs detected in drinking water chloromethane, dichlorodifluoromethane, and fluorotrichloromethane are generally associated with their 

use as refrigerants. Dichlorodifluoromethane, also 

known commonly as Freonl2 or CFC 12, was the most 

frequently detected of the three refrigerants, reported in 

1.2 percent of the randomly selected CWSs at any 

reporting level (table 9). It also co-occurred in 61 

percent of the samples that contained fluorotrichloromethane. Overall, the three refrigerants were 

detected in just 3 percent (55 of 1,673) of randomly 

selected CWSs, but they were reported in 10 percent of 

CWSs with sources in urban areas. When compared to 

the low detection frequency (2 percent) in those CWSs 

with rural sources only, the refrigerants also were 

related significantly (contingency-table testp<0.0001) 

to high population-density urban areas. Refrigerant 

detection frequencies were somewhat lower at the 

1.0-(ig/L reporting level (2 percent of CWSs overall; 

7 percent in urban areas, and 1.4 percent in rural areas) 

yet the relation to urban land use persists (p <0.0001).

Eleven of the 18 compounds used primarily in 

the synthesis of other organic chemicals were reported 

in drinking-water samples from the randomly selected 

CWSs during 1993-98, but most of these were reported 

by less than 10 systems (see table 9). Collectively, 

organic synthesis compounds were detected in 2 

percent (42 of 2,098) of randomly selected CWSs at 

any reporting level, and in 1.1 percent (24 of 2,098) of 

CWSs at the 1.0 |J.g/L reporting level. The occurrence 

of organic synthesis VOCs also is significantly related 

to urban areas 7 percent of the CWSs with sources in 

urban areas reported their detection compared to 1.3 

percent of systems in rural areas. A contingency-table 

test for the independence of detections of organic 

synthesis compounds in relation to population density 

rejected the null hypothesis at p<0.0001.

Occurrence and Distribution of VOCs in Drinking Water 47
80° 78° 76° 74° 72° 70° 68° 66° 64°

48°

46°

44°

42°

40°

38°

EXPLANATION

AREA WHERE POPULATION EQUALS 

OR EXCEEDS 1,000 PEOPLE 

PER SQUARE MILE

SOURCES FOR CWSs WITH FUMIGANT

VOC DETECTIONS 

Ground-water source 

Surface-water source

SOURCES FOR CWSs WITHOUT 

FUMIGANT VOC DETECTIONS 

Ground-water source 

Surface-water source

Base from U.S. Department of Commerce digital data 1:100,000, 1993 

Albers projection

100 200 MILES

100 200 KILOMETERS

Figure 15. Drinking-water sources for randomly selected community water systems in the study area, showing 

systems with analytical data and systems with reported detectable concentrations of any fumigants, in relation to 

urban land use.

48 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
POTENTIAL HUMAN EXPOSURE TO 

VOCS IN DRINKING WATER

Actual Population Served by Randomly 

Selected CWSs

Information on the actual number of people 

served by the randomly selected CWSs in the 12-State 

area who may have been exposed to VOCs in their 

drinking water during 1993-98 can be determined from 

the drinking-water data and information coded in the 

SDWIS database. Furthermore, because the selection 

of CWSs for this study was random and designed to 

represent the overall population of people served by all 

CWSs in the 12 States, the frequency of detection of 

VOCs in drinking water determined for the random 

sample can be used to project the overall number of 

systems and people likely to have been similarly 

affected during the same time period. The tabulation, 

on the basis of the random data, of the number of 

people potentially exposed to VOCs in drinking water, 

and to an even greater extent the projection of that 

information to the larger population, should be considered as only approximations of the actual numbers. 

Several factors can affect the veracity these estimates, 

including the accuracy and completeness of the random 

data, areal and temporal variations of source-water 

quality and use, residence time and routing of finished 

water in CWSs' distribution systems, and the application and effectiveness of water-treatment processes.

Exposure, as used in this report, simply refers to 

the occurrence of a VOC at least once in drinking water 

supplied to a known population. Tabulations of known 

populations served, and projections of potential populations served, by CWSs with VOCs present in their 

drinking water are measures of acute exposure. It is 

beyond the scope of this study, and perhaps beyond the 

capacity of the available data, to provide an estimate of 

chronic exposure of all or part of the population served 

by CWSs in the 12-State area for any extended period 

of time. Well-documented data on the levels and variability of VOCs in drinking water over time would be 

needed to calculate chronic exposure of the population 

served and to interpret the risk to human health associated with that exposure. The information provided in 

this report on the known and estimated number of 

people in the study area potentially exposed to VOCs in 

their drinking water is intended to identify the scope 

and magnitude of that potential exposure so that 

Federal, State, and local water-resource managers and 

public drinking-water consumers can make informed 

decisions to protect the resource and human health.

The actual number of people served by randomly 

selected CWSs that have reported detections of VOCs 

and, therefore, who may have been exposed zt some 

time during 1993-98, can be tabulated from the random 

data. The number of people served by CWSs that have 

reported any detectable concentrations of each of the 

64 VOCs found in drinking water is presented in table 

19. The tabulation shows, for example, that 589 of the 

randomly selected CWSs, which collectively serve 

more than 7 million people, have reported chloroform 

at some detectable concentration in drinking-water 

samples during 1993-98. In addition to chloroform, a 

dozen other VOCs were detected in drinking water 

supplied by CWSs that collectively served more than 1 

million people. The four individual THMs plus total 

THMs were the top five VOCs in drinking water with 

respect to the greatest numbers of people potentially 

exposed; each of the disinfectant by-products and the 

sum of the four THMs were detected in drinking water 

supplied to more than 2.5 million people. The 

commonly detected solvents trichloroethylene, 

1,1,1-tricloroemane, tetrachloroethylene, and c/s-1,2- 

dichloroethene plus MTBE and three of the BTEX 

compounds total xylenes, ethylbenzene, and 

toluene round out the remaining eight VOCs detected 

in drinking water supplied to more than 1 million 

people by randomly selected CWSs. Conversely, five 

VOCs carbon disulfide, c/s-l,3-dichloroprcr>ene, 

hexachlorobutadiene, isopropylbenzene, and tetrahydrofuran have been detected only in drinking water 

supplied by CWSs that serve 1,000 or fewer people. It 

is important to remember, however, that differences in 

the extent and consistency of the analytical coverage of 

the VOCs in drinking water may result in substantial 

underreporting of population served by randomly 

selected CWSs with detections of some VOCs. Clearly, 

exposure numbers for compounds like carbon disulfide 

and tetrahydrofuran that have been analyzed l^y less 

than 10 percent of the 2,110 randomly selected CWSs 

must be reviewed with considerable caution.

Potential Human Exposure to VOCs in Drinking Water 49
Table 19. Population served by randomly selected community water systems in the study area with detections 

of 64 volatile organic compounds in drinking water, 1993-98

[CWSs, community water systems]

Volatile 

organic 

compound

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

H-Butylbenzene

 s^c-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chloro toluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1,1-Dichloroe thane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

trans-1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 , 3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Percentage of 

CWSs with 

analyses

14.6

99.3

77.2

71.2

71.3

79.0

74.4

69.7

4.9

98.9

71.4

78.9

71.3

79.0

75.1

79.2

68.2

79.0

99.3

99.3

77.2

79.0

99.0

84.6

99.0

99.0

99.0

98.9

78.9

79.0

51.1

99.3

Number of 

CWSs with 

detections

9

30

10

486

193

9

6

1

1

32

389

7

589

29

2

4

25

14

8

19

20

31

39

34

43

13

60

15

5

3

1

51

Population 

served by 

CWSs 

with 

detections

29,847

350,649

572,166

6,650,588

3,139,151

96,826

644,484

140,000

725

867,828

5,405,314

5,125

7,060,717

262,158

13,560

318,388

258,111

802,462

46,402

60,743

632,295

770,657

355,898

832,339

1,113,298

150,140

950,823

503,129

88,186

30,826

78

1,066,712

Volatile 

organic 

compound

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-b\ity\ ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1, 1-Trichloroethane

1,1, 2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Trihalomethanes, total

1 ,2,4-Trimethylbenzene

1 ,3 ,5-Trimethylbenzene

Vinyl chloride

/w-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes, total

Percentage of 

CWSs with 

analyses

71.9

73.1

55.3

73.3

73.4

15.8

15.7

56.6

99.3

65.4

74.4

98.5

79.0

74.9

99.0

6.4

99.3

73.5

99.2

98.9

99.0

99.0

78.9

14.4

74.3

74.3

97.7

28.4

67.4

32.4

41.5

63.5

Number of 

CWSs with 

detections

26

9

2

1

2

6

2

106

5

8

4

5

2

1

93

2

88

1

7

106

6

94

4

125

9

7

9

17

32

11

16

57

Population 

served by 

CWSs 

with 

detections

780,141

793,498

900

650

58,310

305,710

30,875

2,265,596

162,430

550,044

64,099

51,665

12,656

9,875

1,742,162

250

1,003,471

535,335

108,652

2,051,995

177,050

2,378,759

438,732

2,516,364

151,342

143,810

353,042

821,649

908,193

719,570

97,601

1,606,252

50 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
The number of people served by randomly 

selected CWSs that have reported detections of VOCs, 

THMs, non-THM VOCs, and MTBE in drinking-water 

samples at any concentration and at the 1.0-|ig/L 

reporting level during 1993-98 is summarized in table 

20 for each of the 12 States in the study area. The tabulation shows that about 92 percent of the 9.6 million 

people served by the 2,110 randomly selected CWSs 

may have been exposed to one or more VOCs (in 

particular THMs) in their drinking water during this 

period. Most of the affected population was included 

when censoring the data at the 1.0-|ig/L reporting level; 

8.7 million people, or 90 percent of population served 

by the randomly selected CWSs may have been 

exposed to one or more of the 54 selected VOCs at 

concentrations at or above 1.0 |ig/L. Although less than 

half the CWSs contained a VOC at detectable concentrations, the high percentage of people served by 

randomly selected CWSs who may have been exposed 

to VOCs reflects (1) the large percentage of the population that is served by the large and very large CWSs 

in urban areas that are supplied by surface-water 

sources (or both ground- and surface-water sources), 

and (2) the occurrence of at least one VOC (generally 

trihalomethane disinfectant by-products) in nearly all 

of these larger, surface-water-supplied systems (see 

table 14).

Approximately 5.3 million people, or about half 

of the population served by the randomly selected 

CWSs in this study, may have been exposed to VOCs 

other than THMs; 4.5 million of these people may have 

been exposed to non-THM VOCs at concentrations at 

or above 1.0 |ig/L (table 20). The large number of 

people served by CWSs with non-THM VOCs in their 

drinking water also reflects the propensity for nonTHM VOC detections among larger systems with 

surface-water sources (see table 14). Non-THM detections also were more common in States with more 

extensive urban areas (see table 13). Variability among 

the States in the percentage of population that may 

have been exposed to non-THM VOCs in their 

drinking water reflects differences in urbanization and

population density in the 12-State region as well as 

differences in reporting levels, analytical coverage, and 

period of record.

The population served by CWSs with a reported 

detection of MTBE in their drinking water also is tabulated in table 20. Approximately 2.3 million people, or 

about one-third of the population served by CWSs 

(with available data on MTBE) may have been exposed 

to MTBE at least once in their drinking water during 

1993-98, and most of those people (2 million) may 

have been exposed to concentrations of 1.0 |ig/L or 

greater. The 2.3 million people are about one-ciuarter of 

the entire population served by the randomly selected 

CWSs in the 12-State area. No data, however, are available on the occurrence of MTBE in the drinking water 

supplied to almost 3 million people served by 916 

CWSs or about 30 percent of the population served by 

the 2,110 CWSs. Consequently, if the 34 percent of the 

population served by CWSs with MTBE data that were 

potentially exposed to MTBE is projected for the 

overall population served by the 2,110 CWSs, then the 

number of people potentially exposed to MTPE in the 

random sample is approximately 3.3 million people. 

Differences in the number of people potentially 

exposed to MTBE from state-to-state reflect the same 

factors described above for other VOCs, but also 

reflect differences in each State's participation and the 

geographic extent of their participation, in the 

OXY/RFG-fuel programs.

The population served by the 6 percent of 

randomly selected CWSs in the 12-State area reporting 

concentrations of VOCs that equaled or exceeded 

drinking-water regulations or recommendations was 

2,622,646 people (see table 8). Four of the 13 VOCs 

that exceeded MCLs including total trihalomethanes, the solvents tetrachloroethylene and trichloroethylene, and the fumigant pesticide ethylene 

dibromide were reported by randomly selected 

CWSs that collectively serve about one-half million 

people or more.

Potential Human Exposure to VOCs in Drinking W>ter 51
Table 20. Population served by randomly selected community water systems reporting detectable concentrations 

of volatile organic compounds in drinking water in the study area, 1993-98

[Percentage of population served by CWSs with any VOC, THMs, non-THMs, or MTBE detected is number of people served by CWSs with detections 

divided by number of people served by CWSs with available data for the specified VOC category and reporting level. Percentage values are rounded. 

CWSs, community water systems; VOC, volatile organic compound; THM, trihalomethane; non-THM, volatile organic compounds exclusive of 

trihalomethanes; MTBE, methyl tert-butyl ether; , not determined]

Number of people (percentage of population served)

VOC detections

State

Conn.

Del.

Maine

Md.

Mass.

N.H.

N.J.

N.Y.

Pa.

R.I.

Vt.

Va.

Total

Served by 

CWSs with 

any VOC 

detections

939,034 

(98)

148,941 

(80)

46,086 

(39)

126,956 

(65)

1,275,894 

(95)

83,597 

(79)

1,733,794 

(96)

1.744,068 

(94)

1,355,278 

(86)

350.206 

(94)

74,430 

(78)

963,310 

(94)

8,841,594 

(92)

Served by 

CWSs with 

VOC 

detections 

at or above 

1.0ng/L

938.374 

(98)

145,382 

(78)

45,461 

(38)

121,513 

(62)

1,264,954 

(94)

74,757 

(70)

1,706,154 

(94)

1,718,305 

(93)

1,327,794 

(85)

346,906 

(93)

64,309 

(67)

958,589 

(93)

8,712,498 

(90)

THM detections

Served by 

CWSs with 

THM 

detections

933,786 

(97)

148,842 

(80)

36,849 

(31)

115,016 

(59)

1,231,636 

(91)

58.611 

(55)

1,719,035 

(95)

1,720,121 

(96)

1,262,409 

(991 )

308,079 

(83)

65,523 

(68)

957,052 

(93)

8,556,959 

(92)

Served by 

CWSs with 

THM 

detections 

at or above 

LO^g/L

933,126 

(97)

145,382 

(78)

36,849 

(31)

111,259 

(57)

1,197,236 

(89)

54,804 

(52)

1,659,519 

(92)

1,644,266 

(92)

1,257,809 

(991 )

308,079 

(83)

56,409 

(59)

952,127 

(93)

8,356,865 

(90)

Non-THM detections

Served by 

CWSs with 

non-THM 

detections

488,928 

(51)

144,026 

(77)

9.237 

(7.8)

96,928 

(49)

781,876 

(58)

60,522 

(57)

1,476,752 

(82)

1,163,372 

(63)

635,130 

(41)

330,297 

(89)

53,236 

(55)

30,865 

(3.0)

5,271,169

(55)

Served by 

CWSs with 

non-THM 

detections 

at or above 

1.0(ag/L

488,268 

(51)

143,591 

(77)

8,612 

(7.3)

91.767 

(47)

690,471 

(51)

55,439 

(52)

1.353,682 

(75)

1,040,613 

(56)

306,580 

(20)

276,997 

(74)

23,974 

(25)

26,130 

(2.5)

4,506,124 

(47)

MTBE detect' ~»ns

Served by 

CWSs with 

MTBE 

detections

373,439 

(39)

6,664

(8.8)

3,604 

(1.8)

193,563 

(17)

19.337 

(18)

954.736 

(75)

515,943 

(35)

191,970

(52)

2,242 

(2.6)

4,098 

(0-4)

2,265,596 

(34)

Srrved by 

CWSs with 

MTBE 

deletions 

at or above 

1.0(ig/L

363,564 

(38)

6,664

(8.8)

3,554 

(1.8)

116,863 

(13)

15,931 

(15)

860,152 

(68)

479,743 

(34)

191,970

(52)

2,242 

(2.7)

4,038 

(0.4)

2,014,721 

(32)

]Not representative because value is based on data for only 12 percent (55 of 443) of randomly selected CWSs and biased to large and very large 

systems (38 of 55 CWSs with THM data).

52 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Estimated Population Served by All CWSs

The statistical design and representativeness of 

the random sample of CWSs inventoried for this study 

allows projections to be made of the total number of 

CWSs and the total number of people served by all 

CWSs in the 12-State area that may have been similarly 

exposed to VOCs. Two methods of projecting the findings from the random sample have been evaluated to 

provide a range of estimates on the total number of 

people who may have been exposed to VOCs in their 

drinking water. The first method extrapolates the 

overall detection frequencies for any compound or 

group of compounds to the total number of CWSs and 

the population served by them in the 12-State area. The 

second method extrapolates detection frequencies on a 

State-by-State basis, aggregating these projections for a 

regional estimate.

Estimates of the total number of CWSs and the 

number of people served in the study area that may 

have been exposed on the basis of simple extrapolation 

of the detection frequencies for any VOC, THMs, nonTHM VOCs, and MTBE from the random data are 

shown in table 21. This method estimates that about 

4,700 CWSs serving nearly 54 million people in the 

region may have had VOCs (or specifically a THM) in 

their drinking water, and about 930 CWSs and almost 

20 million people may have had MTBE in their 

drinking water. Even at the higher 1.0-(ig/L threshold, 

estimates of the number of CWSs and people that may 

have had VOCs in their drinking water are substantially 

similar 4,000 CWSs and 52.8 million people with 

VOCs, and 820 CWSs and 18.7 million people with 

MTBE.

In a second method used to estimate the total 

number of CWSs and the number of people served by 

these systems in the 12-State area that may have had 

detections of VOCs during 1993-98, detection frequencies were extrapolated on a State-by-State basis. A 

State-by-State projection is less likely to overestimate 

or underestimate the number of systems and population 

potentially exposed to VOCs in any given State 

because it does not rely on an average detection 

frequency for all 12 States. Data on the frequency of 

detection for the randomly selected CWSs in each State 

are used to make projections to the total population of 

CWSs for that State. The individual State projections 

were then summed to provide regional projections and 

these are compared with the values obtained by the 

simple extrapolation described above. The results of

the State-by-state projection of the frequency of detection of any VOC, THMs, non-THM VOCs, an-i MTBE 

are shown in table 22.

The total number of CWSs potentially exposed 

to any VOC in drinking water obtained from the Stateby-State projection (table 22) generally agrees with 

the estimate provided by an extrapolation of the overall 

frequency of VOC detections (table 21). Both methods 

indicate that about 4,700 CWSs in the region may have 

experienced at least 1 detection of a VOC during 1993- 

98 and that about 4,000 CWSs may have had VOCs at 

concentrations of 1.0 (ig/L or greater. The range in the 

estimates given in tables 21 and 22 provides a measure 

of the statistical uncertainty, at the 95-percent confidence level, in the estimated number of CWSs that may 

have had VOC detections. The wide range in the estimates provided by the State-by-state projection, 4,020 

to 5,340 CWSs that may have had any VOC defections, 

probably overstates the uncertainty surrounding the 

projection. The actual number of systems exposed to a 

VOC would equal 4,020 only if the lower limit of the 

95-percent confidence level for each State's projection 

were the true value all of the time. The probability of 

that event is very small.

The projected number of CWSs in the 12-State 

area that may have had a THM detection is 4,300 to 

4,700 at any reporting level and 3,700 to 4,000 at the 

1.0-(ig/L reporting level. Differences in the number of 

CWSs projected to have had THM detections vary 

somewhat between tables 21 and 22 as two different 

approaches were used to adjust the projection^ to 

correct for the effects of the limited population of 

randomly selected CWSs with THM data. Data on 

THMs in drinking water were missing for 32 percent 

(174 of 538) of the randomly selected CWSs in New 

York and 88 percent (388 of 443) of the systems in 

Pennsylvania. The random sample was under represented, in particular, for small, ground-water supplied 

systems that characteristically have lower THM detection frequencies. Without adjustments, the projected 

number of CWSs in the study area that may have had 

THM detections would exceed the total number of 

CWSs with VOC detections. Table 21 estimated the 

number of CWSs that may have had THMs as equal to 

the number of CWSs with VOC detections, whereas 

table 22 applied the average frequency of detection of 

THMs for the 10 States with complete THM data to the 

States of New York and Pennsylvania. However, to the 

extent that the frequency of THM detections may be 

under reported by the missing data, the frequency of 

VOC detections also may reflect the same.

Potential Human Exposure to VOCs in Drinking Water 53
When detections of THMs are removed from 

consideration, the projected number of CWSs in the 

study area that may have had other VOC detections is 

cut in half, to about 2,500 CWSs that may have 

detected non-THM VOCs at any reporting level during 

the 6-year period studied. At the 1.0-(lg/L reporting 

level, non-THM VOCs may have occurred in drinking 

water from about 1,800 to 1,900 CWSs (tables 21 and 

22).

The estimated number of CWSs in the 12-State 

area that may have had detections of MTBE at any 

reporting level during 1993-98 is approximately 930 to 

970 systems and 820 to 890 CWSs at thel.O-^lg/L level 

when the estimates are extended to Delaware and Pennsylvania, the two States without MTBE data. In table 

22, MTBE estimates for Delaware and Pennsylvania 

were made by applying the average frequency of 

MTBE detections in the 10 other States, without 

consideration of the distribution of randomly selected 

CWSs in respect to OXY/RFG-fuel use and urban areas 

in each State. To address the uncertainty regarding the 

accuracy of the estimates for Delaware and Pennsylvania, confidence intervals of 100 percent of the estimated total number of CWSs for these States were 

incorporated into the projection. The number of CWSs 

with MTBE concentrations of 5.0 and 20.0 (ig/L can be 

similarly projected as approximately 180 and 80, 

respectively.

Because it is impossible to project exactly which 

systems may have been exposed, projections of population potentially exposed can only be based on the 

percentage of population served by the randomly 

selected CWSs in each State that had reported detections of VOCs. The total number of people served by 

CWSs that were potentially exposed to VOCs 

(including THMs) at any concentration during this 

period were about 52.5 to 53.6 million people 

(tables 21 and 23). Nearly as many people 51.7 to 

52.8 million may have been exposed to VOCs at

concentrations at or above 1.0 |ig/L. About 31.1 or 32 

million people in the region may have been exposed to 

one or more non-THM VOC in their drinking water 

during 1993-98, and from 18.6 to 19.8 million people 

may have been provided drinking water at some time 

during the 6-year period with detectable concentrations 

of MTBE. At the 1.0-^lg/L reporting level, the estimates total 26.5 to 27.4 million people who may have 

been exposed to non-THM VOCs and 17.1 to 18.7 

million who may have had MTBE at comparat:1 ?, levels 

in their drinking water.

Certain characteristics of the data assembled for 

the randomly selected CWSs, however, may confound 

a simple regional projection of the overall frequency of 

detection of VOCs. First, the random data are not 

comprehensive of all VOC analyses for all 2,110 

randomly selected CWSs for the 6-year period, and it is 

likely that other VOC detections have occurred in analyses of drinking-water samples that were not included 

in these data. To the extent that some analytical data 

may be missing from this analysis and that data may 

contain uncounted VOC detections, the detection 

frequencies, and consequently projections of human 

exposure, made in this report are negatively biased and 

conservative. Conversely, if data exist for CWSs that 

currently have no data for specific VOCs in tl \s analysis, for example the 916 CWSs that are missing any 

MTBE data, and no additional detections were 

observed in those data, then the detection frecuencies 

and exposure projections made in this report are positively biased. Also, with regard to the estimates that 

were made for VOC detections at any reporting level, 

it is important to recognize that the reporting levels 

vary from State-to-State or even within some J^ates for 

selected compounds. The frequency of detection determined for the randomly selected CWSs by counting 

detections at any reporting level is not statistically 

robust in that the data were not censored to a common 

reporting level.

54 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 21 . Estimated number of community water systems and population in the study area that may have had detectable 

concentrations of volatile organic compounds in drinking water during 1993-98 based on extrapolation from randomly 

selected community water systems

[Estimate values are based on 10,479 active systems serving 58,449,923 people in the 12-State area reported in U.S. Environmental Protection Agency Safe 

Drinking Water Information System database as of December 1, 1997; estimated values are rounded. CWSs, community water systems]

Estimated number Percentage of freouencv for 

.,,.., . . i .* and range in population Volatile organic compound randomly selected . .«,.,,, . .

category and reporting level CWSs + 95-percent ber °f CWhS * T rw* confidence limits that may have had random CWSs 

, rt detections with detections (percent)

Any volatile organic compound at 

any reporting level

Any volatile organic compound at 

or above 1.0(ig/L

Trihalomethanes at any reporting 

level

Trihalomethanes at or above 

l.O^ig/L

Non-trihalomethane volatile organic 

compounds at any reporting level

Non-trihalomethane volatile organic 

compounds at or above 1 .0 (J.g/L

Methyl terf-butyl ether at any 

reporting level

Methyl tert-bntyl ether at or above 

l.O^tg/L

45 

±2.1

38 

±2.0

'45 

±2.5

±2.0

24 

±1.8

18 

±1.9

8.9 

±1.6

7.8 

±1.5

4,700 92 

4,500 - 4,900

4,000 90 

3,800 - 4,200

4,700 92 

4,500 - 5,000

4,000 90 

3,800 - 4,200

2,500 55 

2,300 - 2,700

1,900 47 

1,700-2,100

2930 34 

760- 1,100

2820 32 

660 - 970

Estimated 

population served by 

CWSs that may have 

had detections

53,600,000

52,800,000

53,600,COO

52,600,000

32,000,000

27,400,000

2 19,800,000

2 18,700,000

1 Value used equals percentage of systems reporting detections of any volatile organic compound due to incomplete data for trihalometh-uies from

New York and Pennsylvania. 

"Includes Delaware and Pennsylvania.

Potential Human Exposure to VOCs in Drinking Water 55
Table 22. Estimated number of community water systems in the study area that may have had detectable concentrations 

of volatile organic compounds in drinking water during 1993-98 based on extrapolation of frequency of detection for 

each State

[All values are rounded. CWSs, community water systems; VOC, volatile organic compound; THMs, trihalomethanes; MTBE, methyl tert-butyl ether]

Estimated number and range in number of CWSs that may have had detectable concentrations

State

Conn.

Del.

Maine

Md.

Mass.

N.H.

N.J.

N.Y.

Pa.

R.I.

Vt.

Va. 3

Total

Any VOC

At any 

reporting 

level

220

170 - 270

100

70-130

110

70 - 150

230

180-280

340

300 - 380

340

290 - 390

460

410-510

1,370

1,260- 1,480

610

520 - 700

50

40-60

250

200 - 300

590

510-670

4,670

4,020 - 5,320

At or 

above

1.0ng/L

210

160 - 260

70

40 - 100

100

60- 140

200

150 - 250

310

260 - 360

240

190 - 290

420

360 - 480

1,180

1,070- 1,290

490

400 - 580

50

30-70

160

120 - 200

500

420 - 580

3,930

3,260 - 4,600

THMs

At any 

reporting 

level

140

90 - 190

100

60 - 140

30

10-50

210

160 - 260

280

220 - 340

170

120-220

410

360 - 460

2 1,220

1,090-1,350

2 1,010

720-1,300

40

20-60

190

140 - 240

500

420 - 580

4,300

3,410-5,190

At or 

above 

LO^g/L

120

80 - 160

70

40 - 100

30

10-50

180

130 - 230

240

180 - 300

140

100 - 180

370

310-430

2 1,060

930- 1,190

2880

590- 1,170

40

20-60

150

110- 190

420

340 - 500

3,700

2,840 - 4,560

Non-THM VOCs

At any 

reporting 

level

160

110-210

50

20-80

90

50-130

100

60 - 140

220

170-270

240

190 - 290

260

210-310

560

470 - 650

460

380 - 540

40

20-60

140

100-180

210

150 - 270

2,530

1,930-3,130

At or 

above 

1.0ng/L

160

110-210

40

10-70

70

40 - 100

80

40 - 120

180

140 - 220

160

110-210

220

170 - 270

360

280 - 440

320

240 - 400

30

20-40

60

30-90

150

100-200

1,830

1,290-2,370

MTBH

At any 

reporting 

level

70

40 - 100

! 20

0-40

40

10-70

20

0-40

60

20 - 100

120

80 - 160

190

120 - 260

200

110-290

! 200

0-400

10

0-20

20

0-40

20

0-40

970

380-1,560

At or 

above 

LO^ig/L

90

60 - 120

T 20

0-40

40

10-70

10

0-20

50

20-80

80

40 - 120

130

70 - 190

240

140 - 340

hso

0-360

10

0-20

20

0-40

20

0-40

890

340- 1,440

Estimates for Delaware and Pennsylvania used average frequency of detection for methyl tert-butyl ether for 10 other States. 

"Estimates for New York and Pennsylvania used average frequency of detection of trihalomethanes for 10 other States. 

Includes District of Columbia.

56 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Table 23. Estimated number of people served by community water systems in the study area that may have had 

detectable concentrations of volatile organic compounds in drinking water during 1993-98 based on extrapolation of 

population served by random systems with detections for each State

[All values are rounded. Estimated number of people served by CWSs that may have had detections extrapolated from percentage of population served by 

randomly selected CWSs that have reported detections of the specified type of VOCs shown in table 20 and the total number of people served by C^vSs in the 

study area shown in table 4. CWSs, community water systems; VOC. volatile organic compound; THMs, trihalomethanes; MTBE, methyl tert-bufyl ether]

Estimated number of people served by community water systems that may have had detections

State

Conn.

Del.

Maine

Md.

Mass.

N.H.

N.J.

N.Y.

Pa.

R.I.

Vt.

Va. 1

Total

Any VOC

At any 

reporting 

level

2,556,000

541,000

230,000

2,942,000

7,400,000

574,000

7,304,000

15,662,000

9,082,000

912,000

355,000

4,969,000

52,500,000

At or 

above 

1-Ong/L

2,554,000

528,000

227,000

2,816,000

7,337,000

513,000

7,188,000

15,431,000

8,898,000

904,000

315,000

4,944,000

51,700,000

THMs

At any 

reporting 

level

2,542,000

541,000

184,000

2,669,000

7,144,000

403,000

7,242,000

16,019,000

10,418,000

802,000

320,000

4,936,000

53,200,000

At or 

above 

1.0ug/L

2,540,000

528,000

184.000

2,582,000

6,944,000

377,000

6,991,000

15,312,000

10,380,000

802,000

276,000

4,911,000

51,800,000

Non-THM VOCs

At any 

reporting 

level

1,331,000

523,000

52,000

2,247,000

4,535,000

415,000

5,954,000

10,480,000

4,297,000

860,000

261,000

159,000

31,100,000

At or 

above 

1-Ou.g/L

1,329,000

521,000

43,000

2,127,000

4,005,000

381,000

5,703,000

9,374,000

2,074,000

721,000

117,000

135,000

26,500,000

MTBE

At any 

reporting 

level

1,017,000

230,000

52,000

84,000

1,352,000

133,000

5,717,000

5,868,000

3,568,000

500,000

12,000

21,000

18,600,000

At or 

above 

1.0ng/L

1,006,000

217,000

52,000

82,000

1,022,000

110,000

5,151,000

5,586,000

?, 360,000

500,000

13,000

21,000

17,100,000

Includes District of Columbia.

Potential Human Exposure to VOCs in Drinking Water 57
SUMMARY AND CONCLUSIONS

This study determined the occurrence and distribution of methyl tert-butyl ether (MTBE) and other 

volatile organic compounds (VOCs) in public drinking 

water of the Northeast and Mid-Atlantic regions of the 

United States for 1993-98. The Northeast and MidAtlantic regions were selected because they have large 

populations, extensive urban and industrial development, and widespread use and release of many VOCs. 

These regions comprise the largest contiguous area, 

outside of California, where the gasoline additive 

MTBE is used to meet requirements of the Clean Air 

Act Amendments of 1990. The study area included the 

six New England States plus New York, New Jersey, 

Pennsylvania, Maryland, Delaware, and Virginia.

This assessment was designed to provide information based on a statistically representative sample of 

20 percent of the community water systems (CWSs) in 

the 12 States. A random selection of 2,110 CWSs was 

made to represent the actual distribution of the 10,479 

active CWSs in the region as of December 1, 1997 by 

State, source of water, and size of system. The resulting 

distribution of randomly selected CWSs included 

1,690 systems supplied exclusively by ground water, 

270 supplied exclusively by surface water, and 150 

systems that draw on both ground- and surface-water 

sources. About two-thirds of the randomly selected 

CWSs are small, serving fewer than 500 people, 20 

percent serve 501 to 3,300 people, 13 percent serve 

3,301 to 50,000 people, and 1.5 percent (31 CWSs) 

serve more than 50,000 people. The number of systems 

selected from within each State reflect the size and 

population of the 12 States and range from 30 systems 

in Rhode Island to 538 systems in New York.

Information on chemical analyses, as well as 

supporting documentation, was requested from each 

State for the randomly selected CWSs. The data were 

assembled into a project database, reviewed, documented, and analyzed for information on the frequency 

of detection and reported concentrations of 84 VOC 

analytes. The data obtained from the States varied 

considerably in format, analytical coverage, reporting 

levels, and period of record. A total of 21,635 chemical 

analyses for one or more VOC in drinking-water 

samples collected from January 4, 1993 through 

December 15, 1998 were compiled for the 2,110 

randomly selected CWSs.

Sixty-four of the 84 VOC analytes were detected 

in at least one drinking-water sample at any reporting

level. Forty-one percent of all drinking-water samples 

(8,955), and 45 percent of the randomly selected CWSs 

(943), contained detectable concentrations of one or 

more VOC(s); however, more than half of the 64 VOCs 

detected in drinking water were found in less than 1 

percent of the CWSs. When VOCs were detected in 

drinking water, the co-occurrence of two or more 

VOCs was more common than the presence of a single 

compound.

Thirty-eight percent (795) of CWSs reported 

detection of one or more of 54 VOCs at or above 

concentrations of 1.0 |ig/L; the 54 selected VC^s were 

those that have been analyzed for in drinking water 

from more than half (1,055) of the randomly selected 

CWSs. Most concentrations of VOCs measured in 

drinking water were low (70 percent of all defections 

were at or below 10 (ig/L), but 16 VOCs were 

measured at levels that equaled or exceeded regulated 

(Maximum Contaminant Levels (MCLs) or Health 

Advisories (HAs)) or recommended (Drinking Water 

Advisory (DWA)) concentrations.

VOC detections in drinking water were significantly related (p<0.0001) to urban areas with population density at or above 1,000 people per mi". The 

probability of detecting VOCs at or above l.C |ig/L in 

drinking water was 1.8 times greater for CW5N that 

have a water source in an urban area compared to those 

CWSs with no sources in urban areas. Conseouently, 

the most urbanized States with high population 

density New Jersey, Massachusetts, and Rhode 

Island have the highest VOC detection freq\iencies. 

More than two-thirds (83 of 122) of the randomly 

selected CWSs in New Jersey reported detecting VOCs 

at or above 1.0 (ig/L in their drinking water. VOCs 

were more frequently detected in drinking wrter from 

CWSs supplied by surface water or both ground- and 

surface-water sources than from CWSs supplied exclusively by ground water, and were more frequently 

reported by systems that serve large populations than 

by the smaller systems. These factors are autocorrelated with urban source-water locations.

Four trihalomethane (THM) compound chloroform, bromodichloromethane, chlorodibromomethane, and bromoform chemicals produced as 

by-products of disinfecting drinking water with chlorine, were the most frequently detected VOCs. One or 

more of the four THM compounds (as measured by 

total THMs) was detected in 41 percent of the CWSs. 

Chloroform was the most frequently detected trihalom58 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
ethane in drinking water, measured in 39 percent of the 

CWSs at any reporting levels and in 33 percent of 

CWSs at the 1.0-jag/L reporting level. More than 90 

percent of CWSs supplied by any surface-water source 

reported detectable concentrations of one or more 

THM. The median total THM concentration for 

surface-water supplied CWSs was 30.3 jag/L. Comparatively, only 32 percent of CWSs supplied exclusively 

by ground-water sources contained THMs and the 

median total THM concentration for those systems was 

just 2.5 jag/L. Three percent of the CWSs with THM 

data reported concentrations that equaled or exceeded 

the 100-jLig/L MCL in some drinking-water samples.

The gasoline additive MTBE was the most 

frequently detected VOC after the THM compounds. 

MTBE was reported in 343 drinking-water samples 

from 106 CWSs at concentrations ranging from 0.2 to 

210 jag/L. No MTBE data were available for Delaware 

and Pennsylvania. The overall frequency of detecting 

MTBE was 8.9 percent (or 1,194 CWSs with data) at 

any reporting level and 7.8 percent of 1,074 CWSs 

when the data are censored at the 1.0-jag/L reporting 

level. Only 0.8 percent of the randomly selected CWSs 

with MTBE data reported concentrations that equaled 

or exceeded the 20-jag/L lower limit of the USEPA's 

DWA for MTBE; 2 percent of the CWSs reported 

MTBE concentrations at or above the California 5- 

jag/L taste and odor threshold. The probability of 

MTBE detections at or above 1.0 jag/L in drinking 

water was five times more likely (p<0.0001) to occur in 

those areas of the Northeast and Mid-Atlantic regions 

where it is used in substantial amounts under the 

oxygenated and reformulated fuels program.

Twelve other VOCs associated with gasoline 

contamination also were reported in drinking water in 

the 12-State region. Total xylenes and toluene, detected 

in 3.2 and 2.5 percent of CWSs respectively, were the 

most frequently detected gasoline components after 

MTBE. Detection frequencies of the individual gasoline compounds (benzene, toluene, ethylbenzene, 

and xylenes (BTEX)) do not approach that of MTBE, 

but collectively these compounds were detected in 8.4 

percent of randomly selected CWSs at any reporting 

level. Although as widely distributed in drinking water 

in the 12-State area, MTBE and BTEX compounds 

rarely co-occur. Only 12 drinking-water samples from 

9 CWSs contained simultaneous detections of MTBE 

and a BTEX compound, and in only 3 of the samples 

were MTBE and BTEX concentrations above 20 iig/L. 

The low MTBE and BTEX concentrations and the lack

of significant co-occurrence indicates that most gasoline contaminants in drinking water probably represent 

a combination of distant point sources (leakirg underground storage tanks), small leaks and spills, or other 

diffuse nonpoint source rather than nearby pcrnt 

sources. The widespread occurrence of MTBE and the 

lack of a substantial co-occurrence between MTBE and 

BTEX leads to the conclusion that the extent of 

contamination of drinking water from gasolire is 

substantially greater with the use of MTBE than would 

have occurred had this oxygenate never been added to 

gasoline.

The use of VOCs as solvents is widespread in 

industrial, commercial, and residential settings, and 

consequently, solvents were collectively among the 

most frequently detected VOCs in drinking water in the 

12-State area. One or more of 27 individual solvent 

VOCs were detected at any reporting level in 3,080 

drinking-water samples from 304 randomly selected 

CWSs (14 percent) and in 206 CWSs at or atove 

concentrations of 1.0 jag/L. Three commonly used 

solvents l,l,l-trichloroethane,trichloroethylene, and 

tetrachloroethylene were each detected in about 5 

percent of CWSs. Half of the 3,080 drinking-water 

samples with solvents contained more than 1 solvent 

compound. The high degree of co-occurrence among 

solvents probably reflects common sources (combinations of solvents frequently occur in cleaning chemical 

formulations) and the widely documented presence of 

transformation by-products and degradates. The occurrence of solvents in drinking water was significantly 

associated (p<0.0001) with high-population-density 

urban areas. Although most solvent concentrations in 

drinking water were less than 5.0 jag/L, concentrations 

of eight solvents exceeded MCLs.

Other VOCs were relatively rarely detected in 

drinking water in the 12-State area. The refrigerant 

dichlorodifluoromethane was reported in drir king 

water by 1.2 percent of the randomly selected CWSs 

and often co-occurred with another refrigerant, fluorotrichloromethane. Two VOCs primarily used as fumigant pesticides dibromochloropropane and ethylene 

dibromide were reported in drinking water by almost 

2 percent of the CWSs and have exceeded their MCLs 

of 0.2 and 0.05 jag/L in a few samples.

Information on the population served by the 

randomly selected CWSs that have reported detectable 

concentrations of VOCs during 1993-98 was tabulated 

to provide estimates of the total number of systems and

Summary and Conclus'ons 59
people potentially exposed to VOCs in drinking water 

in the 12-State area during this time period. The 2,110 

randomly selected CWSs inventoried for this study 

collectively serve 9.6 million people and about 92 

percent of them, or 8.8 million people, get their 

drinking water from a CWS that has reported at least 

one detection of a VOC during the 6-year period. 

Commonly, the potential exposure was to one or more 

THMs, but more than half of the population served, 5.3 

million people, also may have been exposed to a nonTHM VOC in their drinking water during this period. 

Tabulation of the number of people potentially exposed 

to MTBE in drinking water from the randomly selected 

CWSs provides a figure of about 2.3 million people; 

however, only 1,194 CWSs serving 6.7 million people 

reported data for MTBE. Projecting the 34 percent of 

people served by CWSs with MTBE data that were 

potentially exposed to MTBE for the total 9.6 million 

served by all randomly selected CWSs indicates that 

the number of people potentially exposed for the 

random sample may be as high as 3.3 million people.

Information on the number of people served by 

randomly selected CWSs that have reported VOC 

concentrations in drinking water that equaled or 

exceeded USEPA drinking-water regulations or recommendations also was tabulated. Six percent (127) of the 

2,110 randomly selected CWSs reported concentrations of 16 VOCs at or above drinking-water criteria. 

The 127 CWSs collectively serve 2.6 million people. 

Thirteen VOCs exceeded MCLs, 2 VOCs exceeded 

HAs, and MTBE concentrations exceeded the DWA. 

Most of the MCL exceedances were for total THMs 

and the solvents trichloroethylene and tetrachloroethylene. Trichloroethylene and tetrachloroethylene 

concentrations that were more than 100 times greater 

than the 5.0-(ig/L MCLs were reported for multiple 

samples from a few CWSs.

On the basis of the representative design of this 

study, the frequencies of detecting any VOC, THMs, 

non-THM VOCs, and MTBE in drinking water from

the randomly selected CWSs were projected to the total 

population of CWSs in the 12-State area to estimate the 

total number of CWSs in the region that may have had 

VOC detections during 1993-98. Estimates made by 

projecting the overall detection frequency for the 12 

States, as well as for each State individually, were made 

and compared. These methods project that about 4,700 

CWSs (4,000 CWSs at the 1.0-jig/L reporting level) in 

the region may have experienced a VOC contaminant 

in their drinking water and that most often it was a 

THM. About 2,500 CWSs (1,800 to 1,900 CWSs at the 

1.0-(ig/L reporting level) may have detected a nonTHM VOC at least once during the 6-year period, and 

approximately 930 to 970 CWSs (820 to 890 CWSs at 

the 1.0-jig/L reporting level) may have had MTBE 

present in their drinking water.

Projecting the total number of people served by 

CWSs in the 12-State area that may have been exposed 

to VOCs during 1993-98 has even greater uncertainty 

than projecting the number of systems because it is 

impossible to predict which specific systems rray have 

had detections. Estimates of the population potentially 

exposed were made by extrapolating the percentage of 

people served by the randomly selected CWSs with 

VOC detections. This method provides estimates of 

approximately 52.5 to 53.6 million people (51.7 to 52.8 

million people at the 1.0-jig/L reporting level) in the 

12-State area, or that nearly the entire population of the 

region served by CWSs potentially may have Hen 

exposed at least once to a VOC in their drinking water 

during 1993-98. It is most likely that the exporure 

would have been to a THM disinfectant by-prcHuct. In 

addition, 31.1 to 32 million people (26.5 to 27.4 million 

people at the 1.0-jig/L reporting level) may have been 

exposed to a non-THM VOC, and from 18.6 to 19.8 

million people (17.1 to 18.7 million people at the 1.0- 

jig/L reporting level) may have been exposed to MTBE 

at least once in their drinking water during 195 3-98.

60 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
REFERENCES CITED

Alliance for Proper Gasoline Handling, 1999, New alliance 

launches consumer gas care campaign to prevent small 

gasoline spills: Washington, B.C., The Alliance for 

Proper Gasoline Handling, 2 p. (press release, July 27, 

1999, accessed December 3, 1999 at URL http:// 

www.gas-care.org/Press_release.htm)

Ashford, N.A., and Miller, C.S., 1998, Chemical exposures Low levels and high stakes (2nd ed.): New 

York, Wiley & Sons, 464 p.

Baehr, A.L., Stackelberg, P.E., and Baker, R.J., 1999, Evaluation of the atmosphere as a source of volatile organic 

compounds in shallow groundwater: Water Resources 

Research, v. 35, no. 1, p. 127-136.

Baehr, A.L., and Zapecza, O.S., 1998, Methyl terf-butyl 

ether (MTBE) and other volatile organic compounds in 

lakes in Byram Township, Sussex County, New Jersey: 

U.S. Geological Survey Water-Resources Investigations Report 98-4264, 8 p.

Bellar, T.A., Lichtenberg, J.J., and Kroner, R.C., 1974, The 

occurrence of organohalides in chlorinated drinking 

waters: Journal of the American Water Works Association, v. 66, no. 12, p. 703-706.

Bender, D.A., Zogorski, J.S., Halde, M.J., and Rowe, B.L., 

1999, Selection procedure and salient information for 

volatile organic compounds emphasized in the National 

Water-Quality Assessment Program: U.S. Geological 

Survey Open-File Report 99-182, 32 p.

California Department of Health Services, 1999, Final statement of reasons, secondary maximum contaminant 

level for methyl te/t-butyl ether and revisions to the 

unregulated chemical monitoring list, Title 22, California Code of Regulations: California Department of 

Health Services, accessed May 15, 2000 at URL 

http://www.dhs.cahwnet.gov./ps/ddwem/chemicals/ 

MTBE/mtbeindex.htm.

DeLorme, 1999, Street Atlas USA: http://www. 

delorme.com.

Delzer, G.C., Zogorski, J.S., Lopes, T.J., and Bosshart, R.L., 

1996, Occurrence of the gasoline oxygenate MTBE and 

BTEX compounds in urban stormwater in the United 

States, 1991-95: U.S. Geological Survey WaterResources Investigations Report 96-4145, 6 p.

Gilliom, R. J., Alley, W.M., and Gurtz, M.E., 1995, Design of 

the National Water-Quality Assessment Program Occurrence and distribution of water-quality 

conditions: U.S. Geological Survey Circular 1112, 

33 p.

Grady, S.J., 1997a, Distribution of MTBE in ground water in 

New England by aquifer type and land use [abs.], in 

American Chemical Society Division of Environmental 

Chemistry Preprints of Extended Abstracts, 213th 

National meeting, San Francisco, Calif., April 13-17: 

American Chemical Society, v. 37, no. 1, p. 392-394.

 1997b, Volatile organic compounds in ground water 

in the Connecticut, Housatonic, and Thames River 

Basins, 1993-95: U.S. Geological Survey Fret Sheet 

FS-029-97, 6 p.

Grady, S.J., and Casey, G.D., 1999, A plan for assessing the 

occurrence and distribution of methyl tert-butyl ether 

and other volatile organic compounds in drinl ing water 

and ambient ground water in the Northeast and MidAtlantic regions of the United States: U.S. Geological 

Survey Open-File Report 99-207, 36 p.

Grady, S.J., and Mullaney, J.R., 1998, Natural and human 

factors affecting shallow water quality in surficial aquifers in the Connecticut, Housatonic, and Thames River 

Basins: U.S. Geological Survey Water-Resources 

Investigations Report 98-4042, 81 p.

Hanchar, D.W, and Grady, S.J., 1994, Effects of urban land 

use on shallow ground-water quality in stratified-drift 

aquifers Comparison of data from the Hudson River 

basin, New York and the Connecticut River basin, Connecticut and Massachusetts [abs.], in EOS Transactions, 

1994 Spring meeting, Baltimore, Md., May 23-27, 

1994: Washington D.C., American Geophysical Union, 

v. 75, no. 16, p. 150.

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

water resources: New York, Elsevier Science, 522 p.

Hitzig, R., Kostecki, P., and Leonard, D., 1998, Study reports 

LUST programs are feeling effects of MTBE releases: 

Soil & Groundwater Cleanup, Aug/Sept. 1998, 

p. 15-19.

Hunter, Bruce, 1999, Impacts of small gasoline splls on 

groundwater [abs.], in MTBE & other toxics in Maine's 

environment, 1999 Maine Water Conference, presentation, April 15, 1999: Augusta, Maine, Maine Department of Environmental Protection.

Johnson, R.L., Pankow, J.F, Bender, D.A., Price, C.V., and 

Zogorski, J.S., 2000, MTBE To what exten* will past 

releases contaminate community water supply wells: 

Environmental Science & Technology, v. 34, no. 9, p. 

2A-9A.

King, W.D., and Marrett, L.D., 1996, Case contro1 study of 

water source and bladder cancer: Cancer Causes and 

Control, v. 7, p. 596-604.

Klotz, J.B., and Pyrch, L.A., 1999, Neural tube defects and 

drinking water disinfection by-products: Epidemiology, 

v. 10, p. 383-390.

Lapham, W.W., and Tadayon, Saeid, 1996, Plan for assessment of the occurrence, status, and distribution of volatile organic compounds in aquifers of the United States: 

U.S. Geological Survey Open-File Report 96-199,44 p.

Lince, D.P, Wilson, L.R., and Carlson, GA., 1998, Methyl 

tert-butyl ether (MTBE) contamination in private wells 

near gasoline stations in upstate New York: Pulletin of 

Environmental Contaminant Toxicology, v. 61, 

p. 484-488.

References Cited 61
Lindsey, B.D., Breen, K.J., and Daly, M.H., 1997, MTBE in 

water from fractured-bedrock aquifers, south-central 

Pennsylvania [abs.], in American Chemical Society 

Division of Environmental Chemistry Preprints of 

Extended Abstracts, 213th National meeting, San 

Francisco, Calif., April 13-17: American Chemical 

Society, v. 37, no. 1, p. 399-400.

Mackay, D.M., and Smith, L.A., 1993, Organic contaminants, in Alley, W. M., ed., Regional ground-water 

quality: New York, Van Nostrand Reinhold, p. 323-343.

Malcolm Pirnie, Inc., 1998, Taste and odor properties of 

methyl tertiary-butyl ether and implications for setting 

a secondary maximum contaminant level: Oakland, 

Calif., Malcolm Pirnie, Inc., Technical Memorandum, 

June 26, 1998, prepared for the Oxygenated Fuels 

Association, Inc., variously paginated.

Moran, M.J., Zogorski, J.S., and Squillace, P.J., 1999,

MTBE in ground water of the United States Occurrence, potential sources, and long-range transport, in 

Water Resources Conference, American Water Works 

Association, Norfolk, Va., September 26-29, 1999 

[Proceedings]: Denver, Colo., American Water Works 

Association [CD-Rom disk].

Morris, R.D., Audet, A.M., and Angelillo, IF., 1992, Chlorination, chlorination by-products, and cancer A 

meta-analysis: American Journal of Public Health, 

v. 82, no. 7, p. 955-963.

Mullaney, J.R., and Grady, S.J., 1997, Hydrogeology and 

water quality of a surficial aquifer underlying an urban 

area, Manchester, Connecticut: U.S. Geological Survey 

Water-Resources Investigations Report 97-4195, 40 p.

NESCAUM, 1999, RFG/MTBE findings & recommendations, August 1999: Boston, Mass., Northeast States for 

Coordinated Air Use Management, accessed December 

1, 1999 at URL http://www.nescaum.org/RFG/ 

RFGPh2.shtml.

Office of Science and Technology Policy, 1997, Interagency 

assessment of oxygenated fuels: Washington, D.C., 

Office of Science and Technology Policy, National 

Science and Technology Council, Executive Office of 

the President of the United States, 239 p.

Pankow, J.F., Thomson, N.R., Johnson, R.L., Baehr, A.L., 

and Zogorski, J.S., 1997, The urban atmosphere as a 

non-point source for the transport of MTBE and other 

volatile organic compounds (VOCs) to shallow ground 

water: Environmental Science & Technology, v. 31, 

no. 10, p. 2821-2828.

Pomes, M.L., Green, W.R., Thurman, E.M., Orem, W.H., 

and Lerch, H.E., 1999, DBP formation potential of 

aquatic humic substances: Journal of the American 

Water Works Association, v. 91, no. 3, p. 103-115.

Price, C.V., and Clawges, R.M., 1999, Digital data sets 

describing water use, toxic chemical releases, metropolitan areas, and population density of the conterminous United States: U.S. Geological Survey Open-File 

Report 99-78, scale 1:2,000,000 [CD-ROM disk].

Robbins, G.A., Henebry, B.J., Schmitt, B.M., Bartolomeo, 

F.B., Green, A., and Zack, P., 1999, Evidence for 

MTBE in heating oil: Ground Water Monitoring 

Review, v. 19, no. 2, p. 65-69.

Sakata, R.Y., and Osinski, M.T., 1999, MTBE and the Safe 

Drinking Water Act Regulatory and policy considerations [abs.], in EOS Transactions, 1999 Fall meeting, 

San Francisco, Calif., December 13-17, 1999: Washington, D.C., American Geophysical Union, v.80, 

no. 46, November 16, 1999 Supplement, p. F422.

Solley, W.B., Pierce, R.R., and Perlman, H.A., 1998, Estimated use of water in the United States in 1995: U.S. 

Geological Survey Circular 1200, 71 p.

Squillace, P.J., 1999, Occurrence of MTBE in ground water 

of the United States, 1993-98, and logistic regression 

analysis of explanatory factors [abs.], in EOS Transactions, 1999 Fall meeting, San Francisco, Calif., 

December 13-17, 1999: Washington, D.C., /merican 

Geophysical Union, v. 80, no. 46, November 16, 1999 

Supplement, p. F420.

Squillace, P.J., Moran, M.J., Lapham, W W, Price, C.V., 

Clawges, R. M., and Zogorski, J.S., 1999, Volatile 

organic compounds in untreated ambient groundwater 

of the United States, 1985-1995: Environmental 

Science & Technology, v. 33, p. 4176-4187.

Squillace, P.J., Zogorski, J.S., Wilber, WG, and Price, C.V.,

1996. Preliminary assessment of the occurrence and 

possible sources of MTBE in groundwater in the United 

States, 1993-1994: Environmental Science & 

Technology, v. 30, no. 5, p. 1712-1730. 

Stackelberg, P.E., O'Brien, A.K., and Terracciano, S.A.,

1997. Occurrence of MTBE in surface and ground 

water, Long Island, N.Y., and N.J.: American Chemical 

Society Division of Environmental Chemistry Preprints 

of Extended Abstracts, 213th National meeting, San 

Francisco, Calif., April 13-17: American Chemical 

Society, v. 37, no. 1, p. 394-397.

Stangroom, S.J., Collins, C.D., and Lester, J.N., 1998, 

Sources of organic micropollutants to lowland rivers: 

Environmental Technology, v. 19, p. 643-666.

Staples, C.A., Werner, A.F., and Hoogheem, T.J., 1985, 

Assessment of priority pollutant concentrations in the 

United States using STORET database: Environmental 

Toxicology and Chemistry, v. 4, p. 131-142.

State of Maine, 1998, The presence of MTBE and other 

gasoline compounds in Maine's drinking water A preliminary report, October 13, 1998: Augusta, Maine, 

Maine Dept. of Human Services, Bureau of Health, 

Maine Dept. of Environmental Protection, Bureau of 

Waste Management & Remediation, and Maine Department of Conservation, Geological Survey, 15 p.

62 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Terracciano, S.A., and O'Brien, A.K., 1997, Occurrence of 

volatile organic compounds in streams on Long Island, 

New York, and in New Jersey Overview of available 

data and reconnaissance sampling: U.S. Geological 

Survey Fact Sheet FS-063-97, 4 p.

U.S. Department of Commerce, 1993, TIGER/line precensus 

files, 1990, edition 1.1: U.S. Department of Commerce, 

Bureau of Census, 1:100,000 digital data, accessed 

January 25, 1999 at URL http://water.usgs.gov/GIS/ 

metadata/usgswrd/countylOO.html.

U.S. Department of Energy, 1999, Petroleum supply

monthly, table D4. Monthly methyl tertiary butyl ether 

(MTBE) production by merchant and captive plants: 

U.S. Department of Energy, Energy Information 

Administration, accessed April 3, 2000 at URL 

http://www.eia.doe.gov/oil_gas/petroleum/ 

data_publications/monthly_oxygenate_report/ 

current/pdf/tabled4.pdf.

U.S. Environmental Protection Agency, 1994, Drinking 

water glossary A dictionary of technical and legal 

terms related to drinking water: Washington, D.C., 

Office of Water, USEPA 810-B-94-006, 108 p.

 1995, Consolidated summary of State reporting 

requirements for the Safe Drinking Water Information 

System (SDWIS): Washington, D.C., Office of Water, 

USEPA 812-B-95-001, variously paginated.

 1996, Drinking water regulations and health advisories: Washington, D.C., Office of Water, USEPA 822- 

R-96-001, 16 p.

 1997, Drinking water advisory Consumer acceptability advice and health effects analysis on methyl 

tertiary-butyl ether (MTBE): Washington, D.C., Office 

of Water, USEPA 822-F-97-009, 34 p.

 1998a, Oxygenates in water Critical information 

and research needs: Washington, D.C., Office of 

Research and Development, USEPA 600R-98-048, 

65 p.

 1998b, Announcement of the drinking water contaminant candidate list: Federal Register, March 12, 1998, 

v. 63, no. 40, p. 10273-10287.

 1998c, List of reformulated gasoline program areas, 

July 2, 1998: U.S. Environmental Protection Agency, 

Office of Mobile Sources, accessed January 11,1999, at 

URL http://www.epa.gov/oms/rfgarea.htm.

 1998d, Table of winter oxygenated fuels program by 

state, September 28,1998: U.S. Environmental Protection Agency, Office of Mobile Sources, accessed 

January 11, 1999 at URL http://www.epa.goW 

oms/fuels.htm.

 1998e, National primary drinking water regulations Disinfectants and disinfection byproducts, final 

rule: Federal Register, Wednesday, December 16, 

1998, v. 63, no. 241, p. 69390-69476.

 1999a, Revisions to the unregulated contaminant 

monitoring regulation for public water systems; proposed rule: Federal Register, April 30, 1998 v. 64, 

no. 83, p. 23298-23458.

 1999b, A review of contaminant occurrence in public

water systems: Washington, D.C., Office of Water, 

USEPA 816-R-99-006, 78 p.

Waller, K., Swan, S.H., DeLorenze, G, and Hopkins, B., 

1998, Trihalomethanes in drinking water and 

spontaneous abortion: Epidemiology, v. 9, no. 2, 

134-140.

Westrick, J. J., Mello, J.W, and Thomas, R.F., 1994, The 

groundwater supply survey: Journal of the / merican 

Water Works Association, v. 76, no. 5, p. 52-59.

Young, WF, Horth, H., Crance, R., Ogden, T., and Arnott, 

M., 1996, Taste and odour threshold concentrations of 

potential potable water contaminants: Water Research, 

v. 30, p. 331-340.

Zogorski, J.S., Delzer, GC, Bender, D.A., Squillace, P.J., 

Lopes, T.J., Baehr, A.L., Stackelberg, P.A., Landmeyer, 

J.E., Boughton, C.J., Lico, M.S., Pankow, J.F., Johnson, 

R.L., and Thomson, N.R., 1998, MTBE Summary of 

findings and research by the U.S. Geological Survey, in 

Annual Conference of the American Water Vorks 

Association Water quality, Dallas, Tex., June 21-25, 

1998 [Proceedings]: Denver, Colo., American Water 

Works Association, p. 287-309.

Zogorski, J.S., Morduchowitz, Abraham, Baehr, A.L.,

Bauman, B.J., Conrad, D.L., Drew, R.T., Korte, N.E., 

Lapham, W.W., Pankow, J.F., and Washingtcn, E.R., 

1997, Chapter 2, Fuel oxygenates and water quality, in 

Interagency assessment of oxygenated fuels: Washington, D.C, Office of Science and Technology Policy, 

80 p. (8 app.).

References Cited 63

APPENDIXES

Appendix 1. Volatile organic compounds included in analyses of drinking water for randomly selected community water 

systems in the study area, 1993-98

[IUPAC, International Union of Pure and Applied Chemistry; USEPA, U.S. Environmental Protection Agency; CAS, Chemical Abstract Services; 

r, regulated compound required by Safe Drinking Water Act (SDWA); ur, unregulated compound required by SDWA; sd, unregulated compound required at the 

discretion of the State; n, not required by SDWA; c. included on USEPA's Drinking Water Contaminant Candidate List (U.S. Environmental Protection 

Agency, 1998b)]

Volatile organic USEPA 

compound IUPAC name contaminant 

(common or trade name) code num er

Acetone

Acrolein

Acrylonitrile

Benzene

Bromobenzene 

(Phenyl bromide)

Bromochloromethane 

(Methylene chlorobromide)

Bromodichloromethane 

(Dichlorobromomethane)

Bromoform

Bromomethane 

(Methyl bromide)

72-Butylbenzene 

(1-Phenylbutane)

wc-Butylbenzene

te/t-B utylbenzene

Carbon disulfide

Carbon tetrachloride

1-Chlorobutane 

(»-Butyl chloride)

Chlorodibromomethane

Chloroethane 

(Ethyl chloride)

2-Chloroethyl vinyl ether

Chloroform

Chloromethane 

(Methyl chloride)

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane 

(DBCP, Nemagon)

Dibromomethane 

(Methylene dibromide)

m-Dichlorobenzene

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorobenzenes, total

Dichlorodifluoromethane 

(CFC 12;Freonl2)

1,1-Dichloroethane 

(Ethylidene chloride)

1 ,2-Dichloroethane 

(Ethylene dichloride)

1,1 -Dichloroethene 

(Vinylidene chloride)

cis- 1 ,2-Dichloroethene

2-Propanone

2-Propenal

2-Propenenitrile

Benzene

Bromobenzene

Bromochloromethane

Bromodichloromethane

Tribromomethane

Bromomethane

H-Butylbenzene

( 1-Methylpropyl (benzene

(l,l-Dimethylethyl)benzene

Carbon disulfide

Tetrachloromethane

1-Chlorobutane

Dibromochloromethane

Chloroethane

2-Chloroethoxyethene

Trichloromethane

Chloromethane

l-Chloro-2-methylbenzene

1 -Chloro-4-methylbenzene

l,2-Dibromo-3-chloropropane

Dibromomethane

1 ,3-Dichlorobenzene

1 ,2-Dichlorobenzene

1 ,4-Dichlorobenzene

Dichlorobenzenes, (mixed isomers)

Dichlorodifluoromethane

1, 1-Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

2243

2238

2240

2990

2993

2430

2943

2942

2214

2422

2428

2426

2982

2086

2944

2216

2234

2941

2210

2965

2966

2931

2408

2967

2968

2969

2401

2212

2978

2980

2977

2380

67-64-1

107-02-8

107-13-1

71-43-2

108-86-1

74-97-5

75-27-4

75-25-2

74-83-9

104-51-8

135-98-8

98-06-6

75-15-0

56-23-5

109-69-3

124-48-1

75-00-3

110-75-8

67-66-3

74-87-3

95-49-8

106-43-4

96-12-8

74-95-3

541-73-1

95-50-1

106-46-7

25321-22-6

75-71-8

75-34-3

107-06-2

75-35-4

156-59-2

Compound class

Ketone

Oxy alkene

Nitro alkene

Aromatic hydrocarbon

Halogenated aromatic

Halogenated alkane

Halogenated alkane

Halogenated alkane

Halogenated alkane

Alkyl benzene

Alkyl benzene

Alkyl benzene

Sulfur alkane

Halogenated alkane

Halogenated alkane

Halogenated alkane

Halogenated alkane

Ether

Halogenated alkane

Halogenated alkane

Halogenated aromatic

Halogenated aromatic

Halogenated alkane

Halogenated alkane

Halogenated aromatic

Halogenated aromatic

Halogenated aromatic

Halogenated aromatic

Halogenated alkane

Halogenated alkane

Halogenated alkane

Halogenated alkene

Halogenated alkene

Primary use 

or source

Solvent

Organic synthesis

Organic synthesis

Gasoline

Solvent

Organic synthesis

Disinfectant by-product

Disinfectant by-prodrct

Fumigant

Hydrocarbon

Hydrocarbon

Hydrocarbon

Organic synthesis

Solvent

Organic synthesis

Disinfectant by-prodrct

Solvent

Organic synthesis

Disinfectant by-prodrct

Refrigerant

Solvent

Solvent

Fumigant

Solvent

Solvent

Solvent

Fumigant

Solvents

Refrigerant

Solvent

Solvent

Solvent

SDWA

c

n

n

r

ur, c

sd

ur

ur

ur, c

sd

sd

sd

n

r

n

ur

ur

n

ur

ur

ur

ur

r

ur

ur

r

r

n

sd

ur, c

r

r

Solvent r 

Appendix 1 67
Appendix 1 . Volatile organic compounds included in analyses of drinking water for randomly selected community water 

systems in the study area,1993-98-Continued

[IUPAC, International Union of Pure and Applied Chemistry; USEPA, U.S. Environmental Protection Agency; CAS, Chemical Abstract Services; 

r, regulated compound required by Safe Drinking Water Act (SDWA); ur, unregulated compound required by SDWA; sd, unregulated compound required at the 

discretion of the State; n, not required by SDWA; c, included on USEPA's Drinking Water Contaminant Candidate List (U.S. Environmental Projection 

Agency, 1998b)]

Volatile organic 

compound 

(common or trade name)

trans- 1,2-Dichloroethene

Dichloromethane 

(Methylene chloride)

1 ,2-Dichloropropane 

(Propylene dichloride )

1 ,3-Dichloropropane 

(Trimethylene dichloride)

2,2-Dichloropropane

1 , 1 -Dichloroprope ne

cis- 1 ,3-Dichloropropene

trans-l ,3-Dichloropropene

cis- & fra«i-l,3-Dichloropropene

Diethyl ether 

(Ethyl ether)

Ethylbenzene 

(Phenylethane)

Ethylene dibromide 

(EDB)

Fluorotrichloromethane 

(CFC ll;Freonll)

Hexachlorobutadiene

Hexachloroethane

f7-Hexane

Isopropylbenzene

p-Isopropyltoluene 

(p-Cymene)

Methyl butyl ketone 

(Butyl methyl ketone; MBK)

Methyl ethyl ketone 

(Ethyl methyl ketone; MEK)

Methyl isobutyl ketone 

(Isobutyl methyl ketone; 

MIBK)

Methyl methacrylate

Methyl terf-butyl ether 

(MTBE)

Monochlorobenzene

Naphthalene

Nitrobenzene

Pentachloroethane

n-Propylbenzene 

(Isocumene)

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

IUPAC name c

trans- 1 ,2-Dichloroethene

D ichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

1 , 1 -Dichloropropene

cis- 1 ,3-Dichloropropene

trans- 1 ,3-Dichloropropene

1,3-Dichloropropene, (mixed 

isomers)

1,1-Oxybisethane

Ethylbenzene

1 ,2-Dibrotnoethane

Trichlorofluoromethane

l,l,2,3,4,4-Hexachloro-l,3-

butadiene

1,1,1 ,2,2,2-Hexachloroethane

«-Hexane

( 1 -MethylethyDbenzene

1 -Isopropyl-4-methylbenzene

2-Hexanone

2-Butanone

4-Methyl-2-pentanone

Methyl 2-methyl-2-propenoate

2-Methoxy-2-methylpropane

Chlorobenzene

Naphthalene

Nitrobenzene

1,1,1 ,2,2,2-Pentachloro-ethane

n -Propylbenzene

Ethenylbenzene

1,1, 1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

USEPA 

:ontaminan 

code

2979

2964

2983

2412

2416

2410

2228

2224

2413

2090

2992

2946

2218

2246

2225

2376

2994

2030

2247

2249

2295

2251

2989

2248

2254

2327

2998

2996

2988

2986

CAS 

number

156-60-5

75-09-2

78-87-5

142-28-9

594-20-7

563-58-6

10061-01-5

10061-02-6

542-75-6

60-29-7

100-41-4

106-93-4

75-69-4

87-68-3

67-72-1

110-54-3

98-82-8

99-87-6

591-78-6

78-93-3

108-10-1

80-62-8

1634-04-4

108-90-7

91-20-3

98-95-3

76-01-7

103-65-1

100-42-5

79-34-5

630-20-6

Compound class

Halogenated alkene

Halogenated alkane

Halogenated alkane

Halogenated alkane

Halogenated alkane

Halogenated alkene

Halogenated alkene

Halogenated alkene

Halogenated alkene

Ether

Alkyl benzene

Halogenated alkane

Halogenated alkane

Halogenated alkene

Halogenated alkane

Alkane

Alkyl benzene

Alkyl benzene

Ketone

Ketone

Ketone

Oxy alkene

Cyclic ether

Halogenated aromatic

Aromatic hydrocarbon

Nitro aromatic

Halogenated alkane

Alkyl benzene

Aromatic hydrocarbon

Halogenated alkane

Halogenated alkane

Primary use 

or source

Solvent

Solvent

Solvent

Organic synthesis

Organic synthesis

Organic synthesis

Fumigant

Fumigant

Fumigant

Solvent

Gasoline

Fumigant

Refrigerant

Organic synthesis

Solvent

Solvent

Organic synthesis

Organic synthesis

Solvent

Solvent

Solvent

Organic synthesis

Gasoline

Solvent

Hydrocarbon

Organic synthesis

Solvent

Solvent

Organic synthesis

Solvent

Solvent

SDWA

r

r

r

ur, c

ur, c

ur, c

ur, c

ur, c

n

n

r

r

sd

sd, c

n

n

sd

sd, c

n

n

n

n

c

r

sd, c

n

sd

r

ur

ur, c

68 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 1. Volatile organic compounds included in analyses of drinking water for randomly selected community water 

systems in the study area,1993-98-Continued

[IUPAC, International Union of Pure and Applied Chemistry; USEPA, U.S. Environmental Protection Agency; CAS, Chemical Abstract Services; 

r, regulated compound required by Safe Drinking Water Act (SDWA); ur, unregulated compound required by SDWA; sd, unregulated compound required at the 

discretion of the State; n, not required by SDWA; c, included on USEPA's Drinking Water Contaminant Candidate List (U.S. Environmental Protection 

Agency, 1998b)]

Volatile organic 

compound 

(common or trade name)

Tetrachloroethylene 

(Perchloroethene; PCE)

Tetrahydrofuran

Toluene

1 , 1 ,2-Trichloro- 1 ,2,2-trifluoroethane 

(CFC 113;Freonll3)

1,2,3-Trichlorobenzene

1,2,4-Trichlorobenzene

1 , 1 , 1 -Trie hloroethane 

(Methyl chloroform)

1 , 1 ,2-Trichloroethane 

(Vinyl trichloride)

Trichloroethylene 

(TCE)

1 ,2,3-Trichloropropane 

(Allyl trichloride)

Trihalomethanes, total 

(THMs)

1 ,2,3-Trimethylbenzene 

(Hemimellitene)

1 ,2,4-Trimethylbenzene 

(Pseudocumene)

1 ,3,5-Trimethylbenzene 

(Mesitylene)

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylene

Xylenes, total

IUPAC name

Tetrachloroethene

1,4-Epoxybutane

Methylbenzene

1 , 1 ,2-Trichloro- 1 ,2,2-trifluoroethane

1 ,2,3-Trichlorobenzene

1,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1,1, 2-Trichloroethane

Trichloroethene

1 ,2,3-Trichloropropane

1 ,2,3-Trimethylbenzene

1 ,2,4-Trimethylbenzene

1 ,3,5-Trimethylbenzene

Chloroethene

1 ,3-Dimethylbenzene

1 ,2-Dimethylbenzene

1 ,4-Dimethylbenzene

1,3- & 1,4-Dimethylbenzene

Dimethylbenzene, mixed isomers

USEPA 

contaminant 

code

2987

2263

2991

2904

2420

2378

2981

2985

2984

2414

2950

2418

2424

2976

2995

2997

2962

2963

2955

CAS 

number

127-18-4

109-99-9

108-88-3

76-13-1

87-61-6

120-82-1

71-55-6

79-00-5

79-01-6

96-18-4

526-73-8

95-63-6

108-67-8

75-01-4

108-38-3

95-47-6

106-42-3

106-42-3 

108-38-3

1330-20-7

Compound class

Halogenated alkene

Cyclic alkane

Alkyl benzene

Halogenated alkane

Halogenated aromatic

Halogenated aromatic

Halogenated alkane

Halogenated alkane

Halogenated alkene

Halogenated alkane

Alkyl benzene

Alkyl benzene

Alkyl benzene

Halogenated alkene

Alkyl benzene

Alkyl benzene

Alkyl benzene

Alkyl benzene

Alkyl benzene

Primary use 

or source

Solvent

Solvent

Gasoline

Refrigerant

Organic synthesis

Solvent

Solvent

Solvent

Solvent

Solvent

Disinfectant by-products

Gasoline

Organic synthesis

Gasoline

Organic synthesis

Gasoline

Gasoline

Gasoline

Gasoline

Gasoline

SDWA

r

n

r

n

sd

r

r

r

r

ur

r

n

sd, c

sd

r

n

n

n

n

r

Appendix 1 69
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected comm

area compared by State, 1993-98

[CWSs, community water systems]

 3

z »

o 2 

ag

(D 0>

0) 3

(0 Q.

oi. &

fel 

2 o

3D m

«g m

3

I 

il

ff 3 

(0 £

(Q

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Acetone

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

391

86.3

130

97

24

1.0

4

3.3

217

3.1

175

32.5

0

0

0

0

Acrolein

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

32

4.7

8

6.7

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Acrylonitrile

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

32

4.7

8

6.7

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Benzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

554

81.2

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,203

96.3

122

100

5,401

78.2

534

99.3

3,181

55

438

98

Bromobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,076

90.8

122

100

5,420

78.4

533

99.1

35

0

15

3

Bromochloromethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

420

51.5

100

83.3

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97

2,061

90.1

122

100

5,441

-JO O

526

97.8

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

 D

1 

Q. 5" 

ro

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Bromodichloromethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

195

100

46

100

657

98.8

80

100

450

81.1

100

99.0

1,501

99.1

105

100

348

76.8

126

94.0

2,073

90.6

122

100

5,793

83.8

364

67.7

45

0.7

19

4.2

Bromoform

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

195

100

46

100

648

97.4

80

100

450

81.1

100

99.0

1,501

99.2

105

100

410

90.5

130

97.0

2,075

90.7

122

100

5,681

82.2

363

67.5

46

0.8

19

4.2

Bromomethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,076

90.8

122

100

5,458

79.0

527

98.0

38

0.6

17

3.8

n-Butylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,066

90.3

122

100

5,392

78.0

534

99.3

0

0

0

0

sec-Butylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

61.7

101

84.2

195

100

46

100

0

0

0

0

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,066

90.3

122

100

5,391

78.0

534

99.3

0

0

0

0

fcrf-Butylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

51.7

101

84.2

195

100

46

100

0

0

0

0

516

93.0

101

100

1,070

70.7

103

98.1

387

35.4

130

97.0

2,066

90.3

122

100

5,391

73.0

534

99.3

0

0

0

0
w a 

 2

a*5 5=

E £

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected comm

area compared by State, 1993-98-Continued

[CWSs, community water systems]

IS

18

(D W

is

81 2-

(0 3

0) |

(Q

0) 

ff

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Carbon disulfide

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

233

51.4

103

76.9

0

0

0

0

0

0

0

0

0

0

0

0

Carbon tetrachloride

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

348

76.8

126

94.0

2,203

96.3

122

100

5,457

79.0

528

98.1

3,195

55

439

99.

1-Chlorobutane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

Chlorodibromomethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

195

100

46

100

649

97.6

80

100

450

81.1

100

99.0

1,501

99.2

105

100

414

91.4

130

97.0

2,075

90.7

122

100

5,703

82.5

364

67.7

46

0

19

4

Chloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,076

90.8

122

100

5,417

78.4

525

97.6

37

0

17

3

2-Chloroethyl vinyl ether

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

59

3.55

8

6.67

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commun

area compared by State, 1993-98-Continued

[CWSs, community water systems]

1

 I 

A 

PO

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Chloroform

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

195

100

46

100

663

99.7

80

100

450

81.1

100

99.0

1,501

99.2

105

100

410

90.5

130

97.0

2,073

90.6

122

100

5,798

83.9

364

67.7

46

0.80

19

4.29

Chloromethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

535

78.4

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,077

90.8

122

100

5,458

79.0

527

98.0

37

0.64

17

3.84

o-Chlorotoluene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

535

78.4

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,069

90.5

120

98.4

5,421

78.5

534

99.3

35

0.61

15

3.39

p-Chlorotoluene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

549

80.5

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,069

90.5

120

98.4

5,421

78.5

534

99.3

37

0.64

17

3.84

Dibromochloropropane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

434

63.6

97

80.8

195

100

46

100

607

91.3

80

100

506

91.2

101

100

10

0.66

9

8.57

133

29.4

91

67.9

1,940

84.8

116

95.1

1,012

14.6

395

73.4

649

11.3

132

29.8

Dibromomethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

30.6

120

100

195

100

46

100

607

91.3

80

100

515

92.9

101

100

1,501

99.2

105

100

387

35.4

130

97.0

2,076

90.3

122

100

5,456

79.0

528

98.1

36

0.63

16

3.61
SS<D 3

Z 9

o 5

to O.

Z

> o

S± =

1 =

"o

2.2

18Jo co

15

S 2.

<0 3

» 5

(O

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

m -Dichlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

549

80.5

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,115

92.5

122

100

5,426

78.5

534

99.3

34

0.5

17

3.8

o-Dichlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,110

92.3

122

100

5,427

78.6

534

99.3

3,131

54.5

439

99.1

^-Dichlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,088

91.3

122

100

5,427

78.6

534

99.3

3,201

55.7

439

99.1

Dichlorobenzenes, total

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

124

5.42

27

22.1

0

0

0

0

0

0

0

0

Dichlorobenzenes, calculated

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,242

98.0

122

100

5,427

78.6

534

99.3

3,223

56.1

439

99.1

Dichlorodifluoromethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

427

52.5

104

86.7

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

348

75.3

126

94.0

2,067

90.4

122

100

5,458

79.0

528

98.1

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

 o 

1

2. x"

IO

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

1,1 -Dichloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

608

89.2

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,088

91.3

122

100

5,441

78.7

525

97.6

38

0.6

18

4.0

1 ,2-Dichloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,203

96.3

122

100

5,441

78.8

526

97.8

3,192

55.6

439

99.1

1,1-Dichloroethene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,198

96.1

122

100

5,443

78.8

526

97.8

3,191

55.5

439

99.1

cis-l,2-Dich!oroethene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,212

96.7

122

100

5,457

79.0

528

98.1

3,137

54.6

438

98.9

frans-l,2-Dichloroethene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,212

96.7

122

100

5,459

79.0

528

98.1

3,124

54.4

439

99.1

Dichloromethane

Number of samples

. srcsHtii^s OA mi3.iys£s -nil*, include umiiytS

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,177

95.2

121

99.2

5,465

79.1

527

98.0

3,121

54.3

439

99.1
<D 0)

0) 3

(0 O.

« 2

3 CO

a > o"

=t 3

8 o

m < o' §

s

185> <o

113* 

(O

I

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

1,2-DichIoropropane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,098

91.7

122

100

5,440

78.7

525

97.6

3,128

54.4

439

99.1

1,3-Dichloropropane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

515

92.8

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,074

90.7

122

100

5,440

78.7

526

97.8

36

0.6

16

3.6

2,2-DichIoropropane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,050

89.6

122

100

5,441

78.8

526

97.8

37

0.6

17

3.8

1 ,1 -Dichloropropene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,076

90.8

122

100

5,440

78.7

526

97.8

36

0.6

16

3.6

m-l,3-E)idiloropropene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

413

60.6

99

82.5

195

100

46

100

0

0

0

0

0

0

0

0

3

0.20

3

2.86

387

85.4

130

97.0

2,010

87.9

122

100

5,456

79.0

528

98.1

0

0

0

0

<ra/ts-l,3-Dichloropropene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

413

60.6

99

82.5

195

100

46

100

0

0

0

0

0

0

0

0

3

0.20

3

2.86

387

85.4

130

97.0

2,012

88.0

122

100

5,456

7Q.Q

528

98.1

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

a. x' 

10

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

1,3-Dichloropropene, cis- & transNumber of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

121

17.7

32

26.7

0

0

0

0

607

91.3

80

100

516

93.0

101

100

1,499

99.1

105

100

0

0

0

0

39

1.71

12

9.84

0

0

0

0

37

0.64

17

3.84

1,3-Dichloropropene, calculated

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

534

78.3

119

99.2

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,053

89.8

122

100

5,456

79.0

528

98.1

37

0.64

17

3.84

Diethyl ether

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

387

85.4

130

97.0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

Ethylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,100

91.8

122

100

5,402

78.2

534

99.3

3,116

54.2

438

98.9

Ethylene dibromide

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

446

65.4

97

80.8

195

100

46

100

607

91.3

80

100

506

91.2

101

100

11

0.73

10

9.52

386

85.2

130

97.0

1,974

86.3

116

95.1

1,012

14.6

395

73.4

664

11.6

135

30.5

Fluorotrichloromethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

418

61.3

100

83.3

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,065

90.3

122

100

5,426

78.5

528

98.1

0

0

0

0
3 O

3 % (D 3

z 3 

0

sa 3

0) Q.

» 9

5?9- §. 

> o

=1 3

0) o

3 S.

31 00

«§ m 

o §

3 Q. 

ID

» w

II

9 3 

W PC5'

(Q 

0)

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1 993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Hexachlorobutadiene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

61.7

101

84.2

195

100

46

100

0

0

0

0

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,064

90.2

122

100

5,420

78.4

534

99.3

0

0

0

0

Hexachloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

n-Hexane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

83

3.63

13

10.7

0

0

0

0

0

0

0

0

Isopropylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

61.7

101

84.2

195

100

46

100

607

91.3

80

100

515

92.8

101

100

1,070

70.7

103

98.1

349

77.0

126

94.0

2,066

90.3

122

100

5,393

78.1

534

99.3

0

0

0

0

p-Isopropyltoluene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

61.7

101

84.2

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.0

103

98.1

387

85.4

130

97.0

2,058

90.0

120

98.4

5,391

78.0

534

99.3

0

0

0

0

Methyl butyl ketone

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

233

51.4

103

76.9

0

0

0

0

0

n

0

0

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

 a 

I

Q. S'

10

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Methyl ethyl ketone

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

386

85.2

130

97.0

203

8.88

22

18.0

300

4.34

181

33.6

0

0

0

0

Methyl isobutyl ketone

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

386

85.2

130

97.0

0

0

0

0

260

3.76

201

37.4

0

0

0

0

Methyl methacrylate

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

Methyl tert-butyl ether

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

507

74.3

120

100

0

0

0

0

122

18.4

55

68.8

456

82.2

101

100

270

17.8

75

71.4

387

85.4

130

97.0

510

22.3

65

53.3

1,839

26.6

241

44.8

0

0

0

0

Monochlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,214

96.8

122

100

5,427

78.6

534

99.3

3,104

54.0

438

98.9

Naphthalene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

549

80.5

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

35.4

130

97.0

2,074

90.7

122

100

368

5.33

259

48.1

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

(D D)

D) 3

a °-

D> 2

" ^

5 7

SE

« H

3) 3

<§ m

2.2 H 3"

a- 3 

c<

18

<D

(0 X

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Nitrobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

Pentachloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

24

1.05

4

3.28

0

0

0

0

0

0

0

0

n-Propylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,065

90.3

122

100

5,392

78.0

534

99.3

0

0

0

0

Styrene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

271

59.8

113

84.3

2,098

91.7

122

100

5,392

78.0

534

99.3

3,013

52.4

438

98.9

l,l*l<2-Tetrachloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,087

91.2

122

100

5,439

78.7

525

97.6

38

0.6

18

4.0

1,1,2,2-Tetrachloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

Q1.3

80

100

516

Q3.0

101

100

1,501

9Q.2

105

100

387

814

130

97.0

2,077

90.8

122

100

5,441

78.8

526

97.8

36

O.

18

4.0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

Tetrachloroethylene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

608

89.2

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,513

100

105

100

387

85.4

130

97.0

2,209

96.6

122

100

5,458

79.0

528

98.1

3,143

54.7

438

98.9

Tetrahydrofuran

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

378

83.4

130

97.0

26

1.14

6

4.92

0

0

0

0

0

0

0

0

Toluene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

554

81.2

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,099

91.8

1^2

100

5,401

78.2

534

99.3

3,114

54.2

438

98.9

l,l,2-Trichloro-l,2,2-trifluoroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

69

10.1

11

9.17

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

103

22 7

69

51.5

0

0

0

0

0

0

0

0

0

0

0

0

1,2,3-Trichlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

422

61.9

101

84.2

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,064

90.2

122

100

5,419

78.4

534

99.3

0

0

0

0

1 ,2,4-Trichlorobenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

514

75.4

119

99.2

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,198

96.1

122

100

5,418

78.4

534

99.3

3,114

54.2

438

98.9
3-S?

§8 

8 5

0) O.

 9.

3 0)

3 a - z 

0

go

ll

« 5:

CO

I

Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected comm

area compared by State, 1993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

1,1,1-Trichloroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,202

96.3

122

100

5,441

78.8

525

97.6

3,222

56.

439

99.

1,1,2-TrichIoroethane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,092

91.5

122

100

5,440

78.7

526

97.8

3,112

54.

438

98.

Trichloroethylene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

604

88.6

120

100

195

100

46

100

607

91.3

80

100

555

100

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,204

96.4

122

100

5,460

79.0

528

98.1

3,212

55.

439

99.

1,2,3-Trichloropropane

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

547

80.2

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,077

90.8

122

100

5,440

78.7

526

97.8

36

0.

16

3.

Trihalomethanes, total

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

0

0

0

0

665

100

80

100

0

0

0

 0

0

0

0

0

0

0

0

0

0

0

0

0

430

6.22

37

6.88

1,725

30.

55

12.

Trihalomethanes, calculated

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

639

93.7

120

100

195

100

46

100

665

100

80

100

450

81.1

100

99.0

1,501

QQ 2

105

100

414

Q1.4

130

97.0

2,076

Q0.8

122

100

5,800

84.0

364

67.7

1,725

30.

55

12.
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected commu

area compared by State, 1993-98-Continued

[CWSs, community water systems]

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

1,2,3-Trimethylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

389

57.0

101

84.2

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1,2,4- Trimethylbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

549

80.5

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,058

90.0

120

98.4

5,392

78.0

534

99.3

0

0

0

0

1,3,5-TrimethyIbenzene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

549

80.5

120

100

195

100

46

100

607

91.3

80

100

516

93.0

101

100

1,070

70.7

103

98.1

387

85.4

130

97.0

2,066

90.3

122

100

5,390

78.0

533

99.1

0

0

0

0

Vinyl chloride

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,202

96.3

122

100

5,417

78.4

525

97.6

2,238

39.0

414

93.4

m-Xylene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

185

27.1

50

41.7

195

100

46

100

0

0

0

0

514

92.6

101

100

7

0.46

6

5.71

0

0

0

0

2,041

89.2

118

96.7

4,915

71.1

260

48.3

40

0.7

19

4.2

o-Xylene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

422

61.9

106

88.3

195

100

46

100

607

91.3

80

100

512

()"> 7

101

100

7

0.16

6

5.71

387

85.4

130

97.0

2,094

91.6

122

100

5,381

1C) O

529

98.3

0

0

0

0
Appendix 2. Availability of data on volatile organic compounds in analyses of drinking water for randomly selected comm

area compared by State, 1993-98-Continued

[CWSs, community water systems]

n

z 5 

o 5 T_ O 

= (D

<D »

D> 3

(0 Q.

» q 

-I

25=

I 3-

* H 

£00

<§ m

18<D »

II

(£2

I

Volatile organic compound 

and statistic

State

Conn. Del. Maine Md. Mass. N.H. N.J. N.Y. Pa. 

/7-XyIene

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

185

27.1

50

41.7

195

100

46

100

0

0

0

0

512

92.2

101

100

439

29.0

85

81.0

0

0

0

0

2,042

89.3

122

100

4,898

70.9

260

48.3

40

0.

19

4.

m- &/?-Xylenes

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

237

34.8

69

57.5

0

0

0

0

607

91.3

80

100

0

0

0

0

0

0

0

0

387

85.4

130

97.0

0

0

0

0

468

6.77

294

54.6

0

0

0

0

m- & p-Xylenes, calculated

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

421

61.7

106

88.3

195

100

46

100

607

91.3

80

100

514

92.6

101

100

7

0.46

6

5.71

387

85.4

130

97.0

2,091

91.4

122

100

5,365

77.6

529

98.3

42

0.

20

4.

Xylenes, total

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

129

18.9

28

23.3

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,499

99.1

105

100

0

0

0

0

2,167

94.8

122

100

17

0.25

9

1.67

3,087

53.

438

98.

Xylenes, calculated

Number of samples

Percentage of analyses that include analyte

Number of CWSs with analyses

Percentage of CWSs with analyses

550

80.6

120

100

195

100

46

100

607

91.3

80

100

552

99.5

101

100

1,501

99.2

105

100

387

85.4

130

97.0

2,211

96.7

122

100

5,402

78.2

534

99.3

3,126

54

438

98.
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specifiei censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; ng'L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20^ig/L 10ng/L 5.0 ng/L 2.0 ng/L LOng/L 0.5|ag/L

Acetone

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

632

2.9

12

1.9

309

14.6

9

2.9

632

2.9

6

1.0

309

14.6

4

1.3

632

2.9

12

1.9

309

14.6

9

2.9

421

1.9

12

2.8

139

6.6

9

6.5

421

1.9

12

2.8

139

6.6

9

6.5

420

1.9

12

2.9

138

6.5

9

6.5

420

1.9

12

2.9

138

6.5

9

6.5

Acrolein

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

30

0.1

0

0

7

0.3

0

0

24

0.1

0

0

7

0.3

0

0

Acrylonitrile

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

32

0.2

0

0

8

0.4

0

0

26

0.1

0

0

8

0.4

0

0

Benzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,987

73.9

52

0.3

2,095

99.3

30

1.4

15,987

73.9

3

0.02

2,095

99.3

1

0.05

15,987

73.9

3

0.02

2,095

99.3

1

0.05

15,987

73.9

4

0.03

2,095

99.3

2

0.1

15,986

73.9

15

0.09

2,095

99.3

8

0.4

15,986

73.9

30

0.2

2,095

99.3

16

0.8

15,969

73.8

46

0.3

2,095

99.3

28

1.3

Appendix 3 85
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; Hg/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20{xg/L 10jig/L 5.0 Jig/I- 2.0 tig/L 1.0tig/L 0.5 ng/L

Bromobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,966

55.3

0

0

1,368

64.8

0

0

11,966

55.3

0

0

1,368

64.8

0

0

11,966

55.3

0

0

1,368

64.8

0

0

ll, 966

55.3

0

0

1,368

64.8

0

0

11,966

55.3

0

0

1,368

64.8

0

0

11,966

55.3

0

0

1,368

64.8

0

0

11,415

52.8

0

0

1,341

63.6

0

0

Bromochloromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,155

56.2

10

0.08

1,626

77.1

10

0.6

12,155

56.2

0

0

1,626

77.1

0

0

12,155

56.2

0

0

1,626

77.1

0

0

12,155

56.2

1

0.01

1,626

77.1

1

0.06

12,155

56.2

2

0.02

1,626

77.1

2

0.1

12,155

56.2

3

0.02

1,626

77.1

3

0.2

11,602

53.6

9

0.08

1,599

75.8

9

0.6

Bromodichloromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

13,980

64.6

2,813

20.1

1,503

71.2

486

32.3

13,980

64.6

76

0.5

1,503

71.2

16

1.1

13,980

64.6

430

3.1

1,503

71.2

70

4.7

13,979

64.6

1,213

8.7

1,503

71.2

177

11.8

13,975

64.6

2,084

14.9

1,503

71.2

299

19.9

13,877

64.1

2,482

17.9

1,500

71.1

401

26.7

13,206

61.0

2,751

20.8

1,479

70.1

483

32.7

Bromoform

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

13,895

64.2

728

5.2

1,504

71.3

193

12.8

13,895

64.2

9

0.06

1,504

71.3

6

0.4

13,895

64.2

27

0.2

1,504

71.3

14

0.9

13,887

64.2

92

0.7

1,504

71.3

32

2.1

13,871

64.1

226

1.6

1,504

71.3

72

4.8

13,569

62.7

416

3.1

1,478

70.0

119

8.0

12,323

57.0

716

5.8

1,451

68.8

193

13.3

86 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Con*! nued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; |iig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 2Q[ig/L 10^g/L 5.0 ng/L 2.0 [ig/L 1.0^g/L 0.5 ng/L

Bromomethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,733

58.8

10

0.08

1,667

79.0

9

0.5

12,733

58.8

0

0

1,667

79.0

0

0

12,733

58.8

0

0

1,667

79.0

0

0

12,730

58.8

1

0.01

1,667

79.0

1

0.06

12,729

58.8

4

0.03

1,667

79.0

4

0.2

12,729

58.8

6

0.05

1,667

79.0

6

0.4

12,179

56.3

9

0.07

1,639

77.7

9

0.6

n-Butylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,020

55.6

22

0.2

1,569

74.4

6

0.4

12,020

55.6

0

0

1,569

74.4

0

0

12,020

55.6

0

0

1,569

74.4

0

0

12,020

55.6

2

0.02

1,569

74.4

2

0.1

12,020

55.6

3

0.02

1,569

74.4

2

0.1

12,020

55.6

12

0.1

1,569

74.4

2

0.1

11,502

53.2

20

0.2

1,543

73.1

4

0.3

sec-Butylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,284

52.2

1

0.01

1,471

69.7

1

0.07

11,284

52.2

0

0

1,471

69.7

0

0

11,284

52.2

0

0

1,471

69.7

0

0

11,284

52.2

0

0

1,471

69.7

0

0

11,284

52.2

0

0

1,471

69.7

0

0

11,284

52.2

0

0

1,471

69.7

0

0

10,766

49.8

1

0.01

1,445

68.5

1

0.07

terf-Butylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,283

52.2

0

0

1,470

69.7

0

0

11,283

52.2

0

0

1,470

69.7

0

0

11,283

52.2

0

0

1,470

69.7

0

0

11,283

52.2

0

0

1,470

69.7

0

0

11,283

52.2

0

0

1,470

69.7

0

0

11,283

52.2

0

0

1,470

69.7

0

0

10,748

49.7

0

0

1,444

68.4

0

0

Appendix 3 87
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; jag/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20|ig/L 10|ig/L 5.0 ug/L 2.0 |o.g/L 1.0|ig/L 0.5 |ig/L

Carbon disulfide

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

233

1.1

1

0.4

103

4.9

1

1.0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

1

0.4

103

4.9

1

1.0

Carbon tetrachloride

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,068

74.3

120

0.8

2,086

98.9

32

1.5

16,068

74.3

0

0

2,086

98.9

0

0

16,068

74.3

0

0

2,086

98.9

0

0

16,068

74.3

1

0.01

2,086

98.9

1

0.05

16,067

74.3

15

0.09

2,086

98.9

9

0.4

16,067

74.3

63

0.4

2,086

98.9

17

0.8

16,054

74.2

115

0.7

2,086

98.9

29

1.4

1-Chlorobutane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

Chlorodibromomethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

13,933

64.4

1,846

13.2

1,507

71.4

389

25.8

13,933

64.4

13

0.09

1,507

71.4

4

0.3

13,933

64.4

46

0.3

1,507

71.4

20

1.3

13,933

64.4

208

1.5

1,507

71.4

52

3.4

13,917

64.3

804

5.8

1,507

71.4

162

10.8

13,629

63.0

1,312

9.6

1,483

70.3

258

17.4

12.762

59.0

1,794

14.1

1,462

69.3

387

26.5

88 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Con*fnued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels o" method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; JJ.g/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20|K|/L 10|K|/L 5.0 ng/L 2.0ng/L 1.0ng/L 0.5 (jg/L

Chloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,691

58.7

10

0.08

1,665

78.9

7

0.4

12,691

58.7

1

0.01

1,665

78.9

1

0.06

12,691

58.7

1

0.01

1,665

78.9

1

0.06

12,691

58.7

1

0.01

1,665

78.9

1

0.06

12,687

58.6

2

0.02

1,665

78.9

2

0.1

12,687

58.6

4

0.03

1,665

78.9

3

0.2

12,160

56.2

10

0.08

1,638

77.6

7

0.4

2-Chloroethyl vinyl ether

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

59

0.3

0

0

8

0.4

0

0

Chloroform

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

14,055

65.0

3,802

27.0

1,504

71.3

589

39.2

14,053

65.0

1,605

11.4

1,504

71.3

195

13.0

14,053

65.0

2,130

15.2

1,504

71.3

266

17.7

14,053

65.0

2,443

17.4

1,504

71.3

323

21.5

14,047

64.9

2,880

20.5

1,501

71.1

420

28.0

14,046

64.9

3,261

23.2

1,501

71.1

497

33.1

13,511

62.4

3,726

27.6

1,484

70.3

582

39.2

Chloromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,721

58.8

39

0.3

1,667

79.0

29

1.7

12,721

58.8

4

0.03

1,667

79.0

4

0.2

12,721

58.8

5

0.04

1,667

79.0

5

0.3

12,721

58.8

8

0.06

1,667

79.0

7

0.4

12,717

58.8

16

0.1

1,667

79.0

12

0.7

12,717

58.8

25

0.2

1,667

79.0

18

1.1

12,149

56.2

39

0.3

1,640

77.7

29

1.8

Appenc"x 3 89
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Coitinued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; |lg/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20|ig/L 10|ig/L 5.0 ng/L 2.0 ng/L I.O^ig/L 0.5 ng/L

o-Chlorotoluene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,504

57.8

3

0.02

1,584

75.1

2

0.1

12,504

57.8

0

0

1.584

75.1

0

0

12,504

57.8

0

0

1,584

75.1

0

0

12,504

57.8

0

0

1,584

75.1

0

0

12,504

57.8

0

0

1,584

75.1

0

0

12,504

57.8

2

0.02

1,584

75.1

2

0.1

11,998

55.5

2

0.02

1,558

73.8

9

0.1

/?-Chlorotoluene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,688

58.6

5

0.04

1,672

79.2

4

0.2

12,688

58.6

0

0

1,672

79.2

0

0

12,688

58.6

0

0

1,672

79.2

0

0

12,688

58.6

0

0

1,672

79.2

0

0

12,688

58.6

2

0.02

1.672

79.2

2

0.1

12,688

58.6

3

0.02

1,672

79.2

2

0.1

12,136

56.1

5

0.04

1,645

78.0

4

0.2

Dibromochloropropane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

7,009

32.4

29

0.4

1,440

68.2

25

1.7

7,009

32.4

0

0

1,440

68.2

0

0

7,009

32.4

0

0

1,440

68.2

0

0

6,593

30.5

0

0

1,439

68.2

0

0

6,580

30.4

0

0

1,439

68.2

0

0

6,580

30.4

1

0.01

1,439

68.2

1

0.07

6,542

30.2

2

0.03

1,434

68.0

2

0.1

Dibromomethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,729

58.8

18

0.1

1,667

79.0

14

0.8

12,729

58.8

0

0

1,667

79.0

0

0

12,729

58.8

0

0

1,667

79.0

0

0

12,729

58.8

1

0.01

1,667

79.0

1

0.06

12,729

58.8

1

0.01

1,667

79.0

1

0.06

12,702

58.7

6

0.05

1,667

79.0

5

0.3

12,144

56.1

17

0.1

1,639

77.7

14

0.8

90 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses cf drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; ^.g/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10^g/L 5.0ng/L 2.0 ng/L LOng/L 0.5 ng/L

/M-Dichlorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,736

58.9

0

0

1,674

79.3

0

0

12,736

58.9

0

0

1,674

79.3

0

0

12,736

58.9

0

0

1,674

79.3

0

0

12,735

58.9

0

0

1,674

79.3

0

0

12,735

58.9

0

0

1,674

79.3

0

0

12,735

58.9

0

0

1,674

79.3

0

0

12,212

56.4

0

0

1,648

78.1

0

0

o -Dichlorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,866

73.3

16

0.1

2,096

99.3

8

0.4

15,866

73.3

7

0.04

2,096

99.3

1

0.05

15,866

73.3

7

0.04

2,096

99.3

1

0.05

15,865

73.3

7

0.04

2,096

99.3

1

0.05

15,865

73.3

8

0.05

2,096

99.3

2

0.1

15,865

73.3

11

0.07

2,096

99.3

5

0.2

15,624

72.2

15

0.1

2,096

99.3

7

0.3

p-Dichlorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,914

73.6

37

0.2

2,096

99.3

19

0.9

15,914

73.6

0

0

2,096

99.3

0

0

15,914

73.6

0

0

2,096

99.3

0

0

15,913

73.6

0

0

2,096

99.3

0

0

15,913

73.6

5

0.03

2,096

99.3

3

0.1

15.913

73.6

17

0.1

2,096

99.3

9

0.4

15,895

73.5

33

0.2

2,096

99.3

17

0.8

Dichlorobenzenes, total

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

124

0.6

0

0

27

1.3

0

0

Appenc^x 3 91
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, IQQS-QS-Coitinued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; (ig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20|ng/L 10|ng/L 5.0ug/L 2.0 ug/L 1.0ug/L 0.5 ng/L

Dichlorobenzenes, calculated

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,091

74.4

51

0.3

2,096

99.3

25

1.2

16,091

74.4

7

0.04

2,096

99.3

1

0.05

16,091

74.4

7

0.04

2,096

99.3

1

0.05

16,090

74.4

7

0.04

2,096

99.3

1

0.05

16,090

74.4

13

0.08

2,096

99.3

5

0.2

16,090

74.4

28

0.2

2,096

99.3

14

0.7

15,565

71.9

48

0.3

2,070

98.1

24

1.2

Dichlorodifluoromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,147

56.2

202

1.7

1,628

77.2

20

1.2

12,147

56.2

1

0.01

1,628

77.2

I

0.06

12,147

56.2

23

0.2

1,628

77.2

3

0.2

12,147

56.2

38

0.3

1,628

77.2

4

0.2

12,147

56.2

72

0.6

1,628

77.2

8

0.5

12,124

56.0

144

1.2

1,628

77.2

16

1.0

11,569

53.5

202

1.8

1,601

75.9

20

1.2

1, 1-Dichloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,786

59.1

440

3.4

1,666

79.0

31

1.9

12,786

59.1

1

0.01

1,666

79.0

1

0.06

12,786

59.1

6

0.05

1,666

79.0

4

0.2

12,786

59.1

34

0.3

1,666

79.0

5

0.3

12,785

59.1

178

1.4

1,666

79.0

15

0.9

12,785

59.1

308

2.4

1,666

79.0

22

1.3

12,273

56.7

420

3.4

1,641

77.8

30

1.8

1 ,2-Dichloroet hane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,090

74.4

119

0.7

2,088

99.0

39

1.9

16,090

74.4

0

0

2,088

99.0

0

0

16,090

74.4

0

0

2,088

99.0

0

0

16,090

74.4

3

0.02

2,088

99.0

2

0.1

16,089

74.4

12

0.07

2,088

99.0

6

0.3

16,089

74.4

28

0.2

2,088

99.0

15

0.7

16,076

74.3

112

0.7

2,088

99.0

37

1.8

92 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels cr method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; (J-gl^, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10ng/L 5.0 ng/L 2.0 ng/L 1.0fig/L 0.5 iig/L

1 ,1 -Dichloroethene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,357

71.0

428

2.8

1,785

84.6

34

1.9

15,357

71.0

46

0.3

1,785

84.6

4

0.2

15,357

71.0

73

0.5

1,785

84.6

5

0.3

15,357

71.0

110

0.7

1,785

84.6

9

0.5

15,356

71.0

192

1.2

1,785

84.6

15

0.8

15,356

71.0

281

1.8

1,785

84.6

23

1.3

15,343

70.9

422

2.8

1,785

84.6

34

1.9

cis-l,2-Dichloroethene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,017

74.0

672

4.2

2,089

99.0

43

2.1

16,017

74.0

45

0.3

2,089

99.0

5

0.2

16,017

74.0

70

0.4

2,089

99.0

11

0.5

16,017

74.0

180

1.1

2,089

99.0

15

0.7

16,017

74.0

350

2.2

2,089

99.0

25

1.2

16,017

74.0

474

3.0

2,089

99.0

36

1.7

15,783

73.0

655

4.2

2,089

99.0

42

2.0

trans- 1,2-Dichloroethene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,046

74.2

27

0.2

2,090

99.0

13

0.6

16,046

74.2

1

0.01

2,090

99.0

1

0.05

16,046

74.2

2

0.01

2,090

99.0

1

0.05

16,046

74.2

4

0.02

2,090

99.0

2

0.1

16,045

74.2

10

0.06

2,090

99.0

4

0.2

16,045

74.2

17

0.1

2,090

99.0

7

0.3

15,810

73.1

27

0.2

2,090

99.0

13

0.6

Dichloromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,015

74.0

118

0.7

2,088

99.0

60

2.9

16,015

74.0

1

0.01

2,088

99.0

1

0.05

16,015

74.0

2

0.01

2,088

99.0

2

0.1

16,015

74.0

11

0.07

2,088

99.0

8

0.4

16,014

74.0

25

0.2

2,088

99.0

17

0.8

16,014

74.0

62

0.4

2,088

99.0

35

1.7

15,768

72.9

115

0.7

2,088

99.0

58

2.8

Appendix 3 93
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; |J.£/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ug/L 10ug/L 5.0 ng/L 2.0 ^ig/L 1.0ug/L 0.5 ng/L

1,2-Dichloropropane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,864

73.3

83

0.5

2,087

98.9

15

0.7

15,864

73.3

1

0.01

2,087

98.9

1

0.05

15,864

73.3

1

0.01

2,087

98.9

1

0.05

15,864

73.3

11

0.07

2,087

98.9

3

0.1

15,863

73.3

22

0.1

2,087

98.9

6

0.3

15,863

73.3

48

0.3

2,087

98.9

11

0.5

15,629

72.2

81

0.5

2,087

98.9

15

0.7

1,3-Dichloropropane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,710

58.8

10

0.08

1,665

78.9

5

0.3

12,710

58.8

0

0

1,665

78.9

0

0

12,710

58.8

0

0

1,665

78.9

0

0

12,710

58.8

2

0.02

1,665

78.9

1

0.06

12,710

58.8

3

0.02

1,665

78.9

1

0.06

12,710

58.8

6

0.05

1,665

78.9

3

0.2

12,172

56.3

9

0.07

1,640

11.1

5

0.3

2,2-Dichloropropane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,689

58.6

4

0.03

1,666

79.0

3

0.2

12,689

58.6

0

0

1,666

79.0

0

0

12,689

58.6

0

0

1,666

79.0

0

0

12,689

58.6

0

0

1,666

79.0

0

0

12,677

58.6

2

0.02

1,666

79.0

2

0.1

12,677

58.6

2

0.02

1,666

79.0

2

0.1

12,122

56.0

3

0.02

1,638

77.6

3

0.2

1 , 1 -Dichloropropene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,713

58.8

0

0

1,665

78.9

0

0

12,713

58.8

0

0

1,665

78.9

0

0

12,713

58.8

0

0

1,665

78.9

0

0

12,713

58.8

0

0

1,665

78.9

0

0

12,713

58.8

0

0

1,665

78.9

0

0

12,701

58.7

0

0

1,665

78.9

0

0

12,173

56.3

0

0

1,639

77.7

0

0

94 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Con+inued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; |4.g/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20|ag/L 10|ag/L 5.0 (ig/L 2.0 |ag/L 1.0|ag/L 0.5 \iglL

cis - 1 ,3-Dichloropropene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

8,755

40.5

1

0.01

1,078

51.1

1

0.01

8,755

40.5

0

0

1,078

51.1

0

0

8,755

40.5

0

0

1,078

51.1

0

0

8,755

40.5

0

0

1,078

51.1

0

0

8,755

40.5

0

0

1,078

51.1

0

0

8,754

40.5

0

0

1,078

51.1

0

0

8,732

40.4

1

0.01

1,078

51.1

1

0.01

frans- 1,3-Dichloropropene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

8,757

40.5

0

0

1,078

51.1

0

0

8,757

40.5

0

0

1,078

51.1

0

0

8,757

40.5

0

0

1,078

51.1

0

0

8,757

40.5

0

0

1,078

51.1

0

0

8,757

40.5

0

0

1,078

51.1

0

0

8,756

40.5

0

0

1,078

51.1

0

0

8,731

40.4

0

0

1,078

51.1

0

0

1,3-Dichloropropene, cis- & transNumber of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

3,498

16.2

0

0

463

21.9

0

0

3,498

16.2

0

0

463

21.9

0

0

3,498

16.2

0

0

463

21.9

0

0

3,498

16.2

0

0

463

21.9

0

0

3,498

16.2

0

0

463

21.9

0

0

3,498

16.2

0

0

463

21.9

0

0

2,993

13.8

0

0

437

20.7

0

0

1,3-Dichloropropene, calculated

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,256

56.6

1

0.01

1,514

71.8

1

0.07

12,256

56.6

0

0

1,514

71.8

0

0

12,256

56.6

0

0

1,514

71.8

0

0

12,256

56.6

0

0

1,514

71.8

0

0

12,256

56.6

0

0

1,514

71.8

0

0

12,255

56.6

0

0

1,514

71.8

0

0

11,725

54.2

1

0.01

1,488

70.5

1

0.07

Appenr^x 3 95
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; (ig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20 tig/L 10 tig/L 5.0 [.ig/L 2.0 ng/L 1.0ng/L 0.5 ug/L

Diethyl ether

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

411

1.9

0

0

134

6.4

0

0

Ethylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,818

73.1

86

0.5

2,095

99.3

51

2.4

15,818

73.1

2

0.01

2,095

99.3

2

0.1

15,818

73.1

4

0.03

2,095

99.3

4

0.2

15,818

73.1

14

0.09

2,095

99.3

8

0.4

15,817

73.1

30

0.2

2,095

99.3

20

1.0

15,817

73.1

47

0.3

2,095

99.3

33

1.6

15,582

72.0

82

0.5

2,095

99.3

51

2.4

Ethylene dibromide

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

7,144

33.0

33

0.5

1,517

71.9

26

1.7

7,144

33.0

0

0

1,517

71.9

0

0

7,144

33.0

0

0

1,517

71.9

0

0

7,144

33.0

0

0

1,517

71.9

0

0

6,893

31.9

0

0

1,517

71.9

0

0

6,865

31.7

2

0.03

1,517

71.9

2

0.1

6,564

30.3

5

0.08

1,490

70.6

2

0.1

Fluorotrichloromethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,921

55.1

56

0.5

1,543

73.1

9

0.6

11,921

55.1

0

0

1,543

73.1

0

0

11,921

55.1

0

0

1,543

73.1

0

0

11,921

55.1

1

0.01

1,543

73.1

1

0.06

11,909

55.0

23

0.2

1,543

73.1

2

0.1

11,905

55.0

32

0.3

1,543

73.1

4

0.3

11,381

52.6

55

0.5

1,517

71.9

9

0.6

96 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels cr method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; jig'L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10ng/L 5.0 ng/L 2.0 ng/L 1.0 ng/L 0.5 ng/L

Hexachlorobutadiene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

10,584

48.9

2

0.02

1,167

55.3

2

0.2

10,584

48.9

0

0

1,167

55.3

0

0

10,584

48.9

0

0

1,167

55.3

0

0

10,583

48.9

0

0

1,167

55.3

0

0

10,583

48.9

0

0

1,167

55.3

0

0

10,583

48.9

1

0.01

1,167

55.3

1

0.09

10,062

46.5

2

0.02

1,141

54.1

2

0.2

Hexachloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

n-Hexane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

83

0.4

0

0

13

0.6

0

0

83

0.4

0

0

13

0.6

0

0

83

0.4

0

0

13

0.6

0

0

83

0.4

0

0

13

0.6

0

0

83

0.4

0

0

13

0.6

0

0

83

0.4

0

0

13

0.6

0

0

70

0.3

0

0

11

0.5

0

0

Isopropylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,853

54.8

1

0.01

1,546

73.3

1

0.06

11,853

54.8

0

0

1,546

73.3

0

0

11,853

54.8

0

0

1,546

73.3

0

0

11,853

54.8

0

0

1,546

73.3

0

0

11,853

54.8

0

0

1,546

73.3

0

0

11,853

54.8

1

0.01

1,546

73.3

1

0.06

11,335

52.4

1

0.01

1,520

72.0

1

0.07

Appendix 3 97
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; |J.g/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20 ng/L 10ng/L 5.0 M9/L 2.0 ng/L LO^g/L 0.5 M9/L

/j-Isopropyltoluene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,882

54.9

6

0.05

1,548

73.4

2

0.1

11,882

54.9

0

0

1,548

73.4

0

0

11,882

54.9

0

0

1,548

73.4

0

0

11,882

54.9

0

0

1,548

73.4

0

0

11,882

54.9

2

0.02

1,548

73.4

2

0.1

11,882

54.9

4

0.03

1,548

73.4

2

0.1

11,364

52.5

6

0.05

1,522

72.1

2

0.1

Methyl butyl ketone

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

233

1.1

0

0

103

4.9

0

0

Methyl ethyl ketone

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

890

4.1

8

0.9

334

15.8

6

1.8

890

4.1

2

0.2

334

15.8

2

0.6

890

4.1

3

0.3

334

15.8

3

0.9

591

2.7

4

0.7

154

7.3

4

2.6

591

2.7

5

0.8

154

7.3

5

3.2

590

2.7

7

1.2

153

7.2

6

3.9

577

2.7

8

1.4

151

7.2

6

4.0

Methyl isobutyl ketone

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

646

3.0

2

0.3

331

15.7

2

0.6

646

3.0

1

0.2

331

15.7

1

0.3

646

3.0

2

0.3

331

15.7

2

0.6

419

1.9

2

0.5

152

7.2

2

1.3

419

1.9

2

0.5

152

7.2

2

1.3

419

1.9

2

0.5

152

7.2

2

1.3

388

1.8

2

0.5

132

6.3

2

1.5

98 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Con+!nued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; [ig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ug/L 10ug/L 5.0 ng/L 2.0 ng/L 1.0ng/L 0.5 |ug/L

Methyl methacrylate

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

Methyl terf -butyl ether

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

5,510

25.5

343

6.2

1,194

56.6

106

8.9

5,510

25.5

27

0.5

1,194

56.6

10

0.8

5,510

25.5

44

0.8

1,194

56.6

17

1.4

5,391

24.9

82

1.5

1,122

53.2

23

2.0

5,374

24.8

174

3.2

1,118

53.0

52

4.6

5,211

24.1

248

4.8

1,074

50.9

84

7.8

4,427

20.5

337

7.6

865

41

106

12.2

Monochlorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,944

73.7

22

0.1

2,096

99.3

5

0.2

15,944

73.7

0

0

2,096

99.3

0

0

15,944

73.7

0

0

2.096

99.3

0

0

15,944

73.7

0

0

2,096

99.3

0

0

15,943

73.7

1

0.01

2,096

99.3

1

0.05

15,943

73.7

13

0.08

2,096

99.3

2

0.1

15,704

72.6

20

0.1

2,096

99.3

5

0.2

Naphthalene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

7,224

33.4

9

0.1

1,379

65.4

8

0.6

7,224

33.4

0

0

1,379

65.4

0

0

7,224

33.4

0

0

1,379

65.4

0

0

7,223

33.4

0

0

1,378

65.3

0

0

7,223

33.4

T

0.03

1,378

65.3

T

0.2

7,220

33.4

4

0.06

1,378

65.3

4

0.3

6,692

30.9

8

0.1

1,351

64.0

7

0.5

Appendix 3 99
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; (ag/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ug/L 10ng/L 5.0 ng/L 2.0 ng/L 1.0ng/L 0.5 ug/L

Nitrobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

23

0.1

0

0

3

0.1

0

0

23

0.1

0

0

3

0.1

0

0

Pentachloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

24

0.1

0

0

4

0.2

0

0

« -Propylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,019

55.6

4

0.03

1,569

74.4

4

0.2

12,019

55.6

0

0

1,569

74.4

0

0

12,019

55.6

0

0

1,569

74.4

0

0

12,019

55.6

1

0.01

1,569

74.4

1

0.06

12,019

55.6

2

0.02

1,569

74.4

2

0.1

12,019

55.6

2

0.02

1,569

74.4

2

0.1

11,479

53.1

3

0.03

1,543

73.1

3

0.2

Styrene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,584

72.0

5

0.03

2,078

98.5

5

0.2

15,584

72.0

0

0

2,078

98.5

0

0

15,584

72.0

0

0

2,078

98.5

0

0

15,584

72.0

1

0.01

2,078

98.5

1

0.05

15,584

72.0

1

0.01

2,078

98.5

1

0.05

15,584

72.0

3

0.02

2,078

98.5

3

0.1

15,350

71.0

5

0.03

2,078

98.5

5

0.2

100 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Cortinued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specifiel censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; [ig'L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10ng/L 5.0 M9/L 2.0 ng/L 1.0ng/L 0.5 M9/L

1,1,1,2-Tetrachloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,727

58.8

2

0.02

1,667

79.0

2

0.1

12,727

58.8

0

0

1,667

79.0

0

0

12,727

58.8

0

0

1,667

79.0

0

0

12,727

58.8

0

0

1,667

79.0

0

0

12,727

58.8

0

0

1,667

79.0

0

0

12,727

58.8

2

0.02

1,667

79.0

2

0.1

12,150

56.2

2

0.02

1,641

77.8

2

0.1

1,1,2,2-Tetrachloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,548

58.0

1

0.01

1,581

74.9

1

0.06

12,548

58.0

0

0

1.581

74.9

0

0

12,548

58.0

0

0

1,581

74.9

0

0

12,548

58.0

0

0

1,581

74.9

0

0

12,547

58.0

1

0.01

1,581

74.9

1

0.06

12,547

58.0

1

0.01

1,581

74.9

1

0.06

12,029

55.6

1

0.01

1,555

73.7

1

0.06

Tetrachloroethylene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16.082

74.3

1,613

10.0

2,090

99.0

93

4.4

16,082

74.3

243

1.5

2,090

99.0

16

0.8

16,082

74.3

359

2.2

2,090

99.0

25

1.2

16,082

74.3

514

3.2

2,090

99.0

32

1.5

16,080

74.3

923

5.7

2,090

99.0

56

2.7

16,080

74.3

1,265

7.9

2,090

99.0

71

3.4

15,849

73.3

1,551

9.8

2,090

99.0

90

4.3

Tetrahydrofuran

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

404

1.9

2

0.5

136

6.4

2

1.5

Append'xS 101
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; Jig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10|xg/L 5.0 |ag/L 2.0|xg/L LO^ig/L 0.5 ^g/L

Toluene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,822

73.1

134

0.8

2,095

99.3

88

4.2

15,822

73.1

15

0.09

2,095

99.3

9

0.4

15,822

73.1

17

0.1

2,095

99.3

10

0.5

15,822

73.1

21

0.1

2,095

99.3

14

0.7

15,821

73.1

40

0.2

2,095

99.3

28

1.3

15,821

73.1

79

0.5

2,095

99.3

53

2.5

15,583

72.0

131

0.8

2,095

99.3

86

4.1

l,l,2-TrichIoro-l,2^-trifluoroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

172

0.8

0

0

80

3.8

0

0

1 ,2,3-TrichIorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

11,918

55.1

2

0.02

1,550

73.5

1

0.06

11,918

55.1

0

0

1,550

73.5

0

0

11,918

55.1

0

0

1,550

73.5

0

0

11,918

55.1

0

0

1,550

73.5

0

0

11,918

55.1

0

0

1,550

73.5

0

0

11,915

55.1

0

0

1,550

73.5

0

0

11,377

52.6

2

0.02

1,523

72.2

1

0.07

1 ,2,4-TrichIorobenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,461

71.5

9

0.06

2,092

99.2

7

0.3

15,461

71.5

0

0

2,092

99.2

0

0

15,461

71.5

0

0

2,092

99.2

0

0

15,460

71.5

0

0

2,092

99.2

0

0

15,460

71.5

0

0

2,092

99.2

0

0

15,460

71.5

4

0.03

2,092

99.2

4

0.2

15,223

70.4

8

0.05

2,092

99.2

6

0.3

102 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Cortinued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; Jigl,, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20iig/L 10iig/L S.OMS/L 2.0ng/L LOng/L 0.5 ng/L

1 ,1 ,1 -Trichloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,116

74.5

1,097

6.8

2,086

98.9

106

5.1

16,116

74.5

87

0.5

2,086

98.9

8

0.4

16,116

74.5

145

0.9

2,086

98.9

15

0.7

16,116

74.5

218

1.4

2,086

98.9

27

1.3

16,114

74.5

433

2.7

2,086

98.9

53

2.5

16,113

74.5

714

4.4

2,086

98.9

77

3.7

16,099

74.4

1,060

6.6

2,086

98.9

101

4.8

1,1,2-Trichloroethane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,843

73.2

9

0.06

2,088

99.0

6

0.3

15,843

73.2

0

0

2,088

99.0

0

0

15,843

73.2

0

0

2,088

99.0

0

0

15,843

73.2

0

0

2,088

99.0

0

0

15,842

73.2

1

0.01

2,088

99.0

1

0.05

15,842

73.2

2

0.01

2,088

99.0

2

0.1

15,606

72.1

9

0.06

2,088

99.0

6

0.3

Trichloroethylene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

16,135

74.6

1,661

10.3

2,090

99.0

94

4.5

16,135

74.6

271

1.7

2,090

99.0

10

0.5

16,135

74.6

391

2.2

2,090

99.0

16

0.8

16,135

74.6

496

3.1

2,090

99.0

25

1.2

16,134

74.6

893

5.5

2,090

99.0

53

2.5

16,134

74.6

1,265

7.8

2,090

99.0

77

3.7

16,120

74.5

1,621

10.1

2,090

99.0

92

4.4

1,2,3-lVichloropropane

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,711

58.8

47

0.4

1,665

78.9

4

0.2

12,711

58.8

0

0

1,665

78.9

0

0

12,711

58.8

0

0

1,665

78.9

0

0

12,711

58.8

0

0

1,665

78.9

0

0

12,711

58.8

15

0.1

1,665

78.9

2

0.1

12,711

58.8

29

0.2

1,665

78.9

3

0.2

12,152

56.2

47

0.4

1,639

77.7

4

0.2

Append"^ 3 103
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Continued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; (ie/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20 ng/L 10ng/L S.OMXJ/L 2.0 [ig/L 1.0 ug/L 0.5 [ig/L

Trihalomethanes, total

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

3,549

16.4

2,448

69.0

304

14.4

125

41.1

3,549

16.4

1,712

48.2

304

14.4

87

28.6

3,549

16.4

2,045

57.6

304

14.4

99

32.6

3,549

16.4

2,191

61.7

304

14.4

108

35.5

3,544

16.4

2,325

65.6

302

14.3

113

37.4

3,543

16.4

2,378

67.1

302

14.3

120

39.7

3,543

16.4

2,447

69.1

302

14.3

125

41 A

Trihalomethanes, calculated

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,756

72.8

5,850

37.1

1,543

73.1

702

45.5

15,754

72.8

3,017

19.2

1,543

73.1

279

18.1

15,754

72.8

3,766

23.9

1,543

73.1

358

23.2

15,754

72.8

4,327

26.9

1,543

73.1

440

28.5

15,747

72.8

4,865

30.9

1,540

73.0

570

37.0

15,732

72.7

5,315

33.8

1,537

72.8

644

41.9

15,182

70.2

5,802

38.2

1,520

72.0

699

46.0

1 ,2,3-Trimethylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

389

1.8

0

0

101

4.8

0

0

389

1.8

0

0

101

4.8

0

0

389

1.8

0

0

101

4.8

0

0

389

1.8

0

0

101

4.8

0

0

389

1.8

0

0

101

4.8

0

0

389

1.8

0

0

101

4.8

0

0

376

1.7

0

0

101

4.8

0

0

1,2,4-Trimethylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,011

55.5

26

0.2

1,567

74.3

9

0.6

12,011

55.5

1

0.01

1,567

74.3

1

0.06

12,011

55.5

2

0.02

1,567

74.3

2

0.1

12,011

55.5

2

0.02

1,567

74.3

2

0.1

12,011

55.5

12

0.1

1,567

74.3

3

0.2

12,011

55.5

21

0.2

1,567

74.3

5

0.3

11,472

53.0

25

0.2

1,541

73.0

8

0.5

104 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Con*! nued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; M-g/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20ng/L 10ng/L 5.0 ng/L 2.0 |ig/L 1.0ng/L 0.5 |ag/L

l,3?5-Trimethylbenzene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

12,017

55.5

23

0.2

1,568

74.3

7

0.4

12,017

55.5

0

0

1,568

74.3

0

0

12,017

55.5

1

0.01

1,568

74.3

1

0.06

12,017

55.5

2

0.02

1,568

74.3

2

0.1

12,017

55.5

5

0.04

1,568

74.3

3

0.2

12,017

55.5

12

0.1

1,568

74.3

5

0.3

11,462

53.0

23

0.2

1,542

73.1

7

0.4

Vinyl chloride

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

15,054

69.6

62

0.4

2,062

97.7

9

0.4

15,054

69.6

1

0.01

2,062

97.7

1

0.05

15,054

69.6

1

0.01

2,062

97.7

1

0.05

15,054

69.6

3

0.02

2,062

97.7

2

0.1

15,054

69.6

12

0.08

2,062

97.7

4

0.2

15,053

69.6

39

0.3

2,062

97.7

8

0.4

15,034

69.5

62

0.4

2,062

97.7

9

0.4

m-Xylene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

7,897

36.5

33

0.4

600

28.4

17

2.8

7,897

36.5

0

0

600

28.4

0

0

7,897

36.5

0

0

600

28.4

0

0

7,897

36.5

2

0.03

600

28.4

0

0.3

7,897

36.5

8

0.1

600

28.4

7

1.2

7,897

36.5

17

0.2

600

28.4

13

2.2

7,892

36.5

30

0.4

600

28.4

15

2.5

o-Xylene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

10,331

47.8

51

0.5

1,423

67.4

32

2.2

10,331

47.8

o

0.02

1.423

67.4

2

0.1

10,331

47.8

2

0.02

1.423

67.4

2

0.1

10,331

47.8

3

0.03

1,423

67.4

3

0.2

10,331

47.8

13

0.1

1,423

67.4

11

0.8

10,330

47.8

27

0.3

1,423

67.4

19

1.3

10,315

47.7

49

0.5

1,423

67.4

31

2.2

Appendix 3 105
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Ccntinued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; fig/L, micrograms per liter; CWSs, community water systems]

Volatile organic compound and statistic

Reporting or censoring level

Any 20U9/L 10ug/L 5.0 ug/L 2.0 \iglL LO^ig/L 0.5 iiglL

p-Xylene

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

8,311

38.4

15

0.2

683

32.4

11

1.6

8,311

38.4

0

0

683

32.4

0

0

8,311

38.4

0

0

683

32.4

0

0

8,311

38.4

0

0

683

32.4

0

0

8,311

38.4

4

0.05

683

32.4

3

0.4

8,311

38.4

6

0.07

683

32.4

4

0.6

8,306

38.4

12

0.1

683

32.4

9

1.3

m- & p-Xylenes

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

2,426

11.2

26

1.1

876

41.5

16

1.8

2,426

11.2

3

0.1

876

41.5

3

0.3

2,426

11.2

7

0.3

876

41.5

5

0.6

2,426

11.2

7

0.3

876

41.5

5

0.6

2,426

11.2

12

0.5

876

41.5

9

1.0

2,426

11.2

19

0.8

876

41.5

13

1.5

2,406

11.1

26

1.1

876

41.5

16

1.8

m- & p-Xylenes, calculated

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

10,356

47.9

49

0.5

1,443

68.4

29

2.0

10,356

47.9

3

0.03

1,443

68.4

3

0.2

10,356

47.9

7

0.07

1,443

68.4

5

0.4

10,356

47.9

8

0.08

1,443

68.4

6

0.4

10,356

47.9

21

0.2

1,443

68.4

16

1.1

10,356

47.9

36

0.4

1,443

68.4

23

1.6

10,331

47.8

49

0.5

1,443

68.4

29

2.0

Xylenes, total

Number of analyses

Percentage of all analyses that include analyte

Number of detections

Percentage of analyses with detections

Number of CWSs with analyses

Percentage of all CWSs with analyses

Number of CWSs with detections

Percentage of CWSs with detections

9,643

44.6

109

1.1

1,339

63.5

57

4.3

9,643

44.6

12

0.1

1,339

63.5

6

0.4

9,643

44.6

26

0.3

1,339

63.5

13

1.0

9,643

44.6

43

0.4

1,339

63.5

24

1.8

9,642

44.6

64

0.7

1,339

63.5

35

2.6

9,531

44.0

87

0.9

1,339

63.5

43

3.2

9,297

43.0

108

1.2

1,339

63.5

56

4.2

106 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 3. Frequency of reporting and frequency of detection of volatile organic compounds included in analyses of drinking 

water for randomly selected community water systems in the study area compared by reporting levels, 1993-98-Conthued

[Data for any reporting level include all data reported by States for specified analyte without regard to differences in minimum reporting levels or method 

detection limits, whereas data for specific censoring levels have been censored to remove samples with a reporting level higher than the specified censoring 

level, and all reported detectable concentrations of the specified analyte below the censoring level have been converted to "less than" values; Hg/L, micrograms per liter; CWSs, community water systems]

Reporting or censoring level Volatile organic compound and statistic 

__________ ___ Any 2Q \iglL 10(ig/L 5.0|ag/L 2.0 |ig/L 1.0 |gg/L 0.5 |jg/L

Xylenes, calculated

Number of analyses_________________15,939 ___ 15,939 15.939____15,939 15,939 15,937____15,692

Percentage of all analyses that include analyte 73.7 73.7 73.7 73.7 73.7 73.7 72.5

Number of detections 162 16 33 53 90 127______165

Percentage of analyses with detections 1.0 0.1 0.2 0.3 0.6 0.8 1.0

Number of CWSs with analyses 2,096 2,096 2,096 2,096 2,096 2,096 2,096

Percentage of all CWSs with analyses 99.3 99.3 99.3 99.3 99.3 99.3 99.3

Number of CWSs with detections 87 10 18 31 53 67 86

Percentage of CWSs with detections 4.2 0.5 0.9 1.5 2.5 3.2 4.1

Appendix 3 107
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community wat^r systems 

in the study area, 1993-98

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

H-Butylbenzene

rec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

trans-l ,2 -Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

Acetone

NA

0

0

41.7

0

0

0

0

0

0

16.7

0

83.3

0

0

0

0

0

0

0

0

0

0

0

0

0

12.5

0

0

0

0

0

0

0

0

0

Benzene

0

NA

2.2

6.5

0

0

0

0

0

11.5

6.5

0

21.7

0

0

0

0

0

0

0

8.9

6.4

5.8

8.7

13.5

0

1.9

1.9

0

0

0

5.8

0

8.9

0

2.2

Bromochloromethane

ND

0

NA

22.2

33.3

0

0

0

ND

0

22.2

0

22.2

0

0

0

0

10

0

0

0

0

0

0

10

0

0

0

0

0

0

0

0

0

0

0

Bromodichloromethane

3.8

0.3

0.2

NA

18.3

0.1

0.2

0.1

0

0.5

61.0

0.2

94.6

1.0

0.3

0.2

0.5

0.2

0.5

0.7

0.2

0.6

2.2

0.5

3.3

0.1

1.7

0.6

0.4

0

0

2.8

0.1

0.2

0

0

Bromoform

0

0

0.6

68.5

NA

0.4

0.2

0

0

0.2

83.2

0

58.4

1.0

0

0.4

0.3

1.4

0.6

1.0

0.2

0.9

1.7

0.6

5.1

0.2

2.3

0.6

0.2

0

0

1.6

0.3

0.2

0

0

Bromomethane

0

0

0

16.7

33.3

NA

0

0

ND

0

33.3

0

16.7

20

0

0

0

0

0

0

0

0

0

0

10

0

0

0

0

0

0

0

0

0

0

0

n-Butylbenzene

ND

0

0

9.1

4.5

0

NA

0

ND

0

9.1

0

9.1

0

4.5

4.5

20

0

9.1

4.5

9.1

0

0

0

0

0

0

0

0

0

0

4.5

0

0

0

0

sooButyltnnzene

ND

0

0

100

0

0

0

NA

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

108 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-butyl ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1 , 1 ,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 , 3 ,5 -Trimethylbenzene

Vinyl chloride

w-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

Acetone

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ND

0

0

0

ND

12.5

ND

25.0

ND

Benzene

0

0

0

25.8

7.7

2.5

0

0

0

0

23.1

0

17.3

0

0

13.5

0

21.2

0

40

0

0

0

0

0

0

0

25.0

Bromochloromethane

0

0

ND

0

0

0

0

0

0

0

20

ND

0

0

0

0

0

20

0

ND

11.1

11.1

0

0

0

0

0

0

Bromodichloromethane

0

2.3

1.4

5.7

0

0.1

0.1

0

0

0

2.8

0

2.1

0

0.1

2.2

0.3

3.5

0

NA

0.1

0.1

1.4

1.2

2.1

1.3

5.0

3.7

Bromoform

0

1.3

1.9

8.2

0

0

0

0

0

0

10.1

0

1.2

0

0.2

3.2

0

6.5

0

NA

0

0

2.9

2.3

2.0

1.4

3.8

2.2

Bromomethane

0

0

0

0

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

n-Butylbenzene

13.6

ND

ND

0

0

20

9.1

0

0

0

0

ND

4.5

0

4.5

0

0

4.5

0

0

77.3

72.7

0

0

0

0

0

0

seoButylbrnzene

0

ND

ND

ND

0

0

0

0

0

0

0

ND

0

0

0

100

0

0

0

ND

0

0

0

0

0

0

ND

0

Append ^4 109
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of coimound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

B romodichloromethane

Bromoform

B romomethane

/7-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroe thane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroe thane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

Carbon 

disulfide

0

0

0

0

0

0

0

0

NA

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

100

0

0

0

0

0

0

0

0

0

Carbon 

tetrachloride

0

5.5

0

6.2

1.0

0

0

0

ND

NA

6.2

0

24.7

0

0

0

0

0

0

0

31.3

24.2

5.8

51.7

39.2

1.7

4.2

0.8

0

0

0

1.9

0

27.3

0

0

Chlorodibromomethane

2.0

0.3

0.2

89.3

33.3

0.2

0.2

0

0

0.6

NA

0.2

84.4

1.1

0.2

0.1

0.3

0.8

0.7

0.7

0.1

0.9

2.2

0.6

4.1

O.I

1.7

0.7

0.1

0.1

0

3.3

0

0.2

0

0

Chloroethane

0

0

0

30

0

0

0

0

0

0

20

NA

30

10

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

10

0

0

0

0

Chloroform

6.5

0.5

0.1

70.7

11.6

0.1

0.1

0

0

1.3

42.3

0.2

NA

0.8

0.2

0.2

0.3

0.4

0.5

0.5

0.8

2.2

1.7

2.7

4.3

0.2

1.3

0.4

0.2

0

0.1

2.1

0.1

0.3

0

0

Chloromethane

0

0

0

31.6

14.3

5.6

0

0

0

0

27.0

2.8

43.2

NA

0

0

0

0

0

0

0

0

11.1

0

0

0

13.9

0

0

0

0

2.8

0

0

0

0

o-Chlorotoluene

ND

0

0

100

0

0

0

0

ND

0

66.7

0

100

0

NA

66.7

0

0

33.3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

p-Chlorot-^uene

0

0

0

60

60

0

20

0

ND

0

25.0

0

60

0

40

NA

0

0

20

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

110 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-buty\ ether

Monochlorobenzene

Naphthalene

H-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1,1,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 , 3 ,5-Trimethy Ibenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

Carbon 

disulfide

0

0

0

0

0

0

0

0

0

0

0

0

100

0

0

0

0

0

0

ND

0

0

0

ND

0

ND

0

ND

Carbon 

tetrachloride

0

0

0

0

0

0

0

1.9

0

0

72.5

ND

0.9

0

0

65.0

0.8

75.4

0

ND

0

0

1.7

0

0

0

0

3.4

Chlorodibromomethane

0

1.3

1.0

5.9

0

0.1

0.1

0

0

0

6.3

0

2.0

0

0.1

2.2

0.1

4.6

0

NA

0.1

0.1

1.8

1.6

2.4

1.7

6.4

3.6

Chloroethane

0

0

0

37.5

0

0

0

0

0

0

0

0

20

0

0

0

0

0

0

0

0

0

0

ND

12.5

ND

12.5

0

Chloroform

0

2.2

1.2

5.3

0.2

0

0.1

0

0.1

0

7.4

0

1.9

0

0.1

7.3

0.2

6.3

0.1

NA

0.2

0.2

0.9

1.2

1.7

1.1

4.1

3.0

Chloromethane

0

0

0

7.7

0

0

0

0

0

0

0

0

2.8

0

0

0

2.8

0

0

27.3

0

0

0

0

3.2

0

4.8

0

o-Chlorotoluene

0

ND

ND

0

0

0

33.3

0

0

0

0

ND

33.3

0

0

0

0

0

0

ND

0

0

0

0

0

0

ND

0

p-Chlorotc'uene

0

50

ND

33.3

0

0

0

0

0

0

0

0

20

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

Appendix 4 111
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

«r-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroe thane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

tram- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2 ,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

Dibromochloropropane

ND

0

0

66.7

25.0

0

50

0

ND

0

50

0

66.7

0

0

0

NA

0

12.5

12.5

0

0

0

0

0

0

0

0

0

0

0

0

89.3

0

0

0

Dibromomethane

0

0

5.6

27.3

63.6

0

0

0

ND

0

63.6

0

72.7

0

0

0

0

NA

0

0

0

0

5.6

0

5.6

0

0

0

0

0

0

0

0

0

0

0

0-

Dichlorobenzene

ND

0

0

37.5

18.8

0

12.5

0

ND

0

37.5

0

56.3

0

6.3

6.3

7.1

0

NA

6.3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

PDichlorobenzene

0

0

0

50

27.8

0

4.5

0

ND

0

35.3

0

52.9

0

0

0

6.7

0

2.8

NA

4.8

0

0

12.1

5.7

2.9

5.9

2.9

0

0

0

2.8

0

0

0

0

Dichlorodifluoromethane

ND

2.1

0

1.0

0.5

0

1.1

0

ND

15.6

0.5

0

7.0

0

0

0

0

0

0

0.5

NA

12.1

1.5

28.6

55.8

0.5

2.0

0

0

1.0

0

0

0

17.2

0

0

1,1- 

Dichloroethane

0

0.7

0

1.6

1.2

0

0

0

0

5.5

1.9

0

10

0

0

0

0

0

0

0

5.6

NA

3.0

55.1

36.1

0

0.9

0.9

0.7

0.2

0

0

0

5.1

0

0

1,2- 

Dichloroethane

0

2.7

0

25.0

8.3

0

0

0

0

6.0

18.3

0

30.6

3.8

0

0

0

1.0

0

0

2.9

12.0

NA

20.2

28.9

0.9

6.0

8.8

2.9

0

0

0.9

4.6

2.0

0

0

V -Dichloroethene

0

1.0

0

1.3

0.8

0

0

0

0

14.3

1.3

0

12.4

0

0

0

0

0

0

1.0

15.0

60.4

5.1

NA

44.7

1.0

2.4

1.2

1.0

0.5

0

0.2

0

11.5

0

0

112 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-butyl ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1 , 1 ,2-Trichloroethane

Trichloroethylene

1,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 ,3,5-Trimethylbenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & /7-Xylenes

Xylenes (total)

Dibromochloropropane

0

0

ND

0

0

0

0

0

0

0

0

ND

0

0

12.5

0

0

12.5

0

100

0

0

0

0

0

0

ND

0

Dibromomethane

0

0

0

0

0

0

0

0

0

0

5.6

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

o- pDichloro- Dichlorobenzene benzene

0

ND

ND

0

0

0

0

0

0

0

0

ND

0

0

12.5

0

0

6.3

0

ND

0

6.3

6.3

0

0

0

0

12.5

0

0

0

0

0

0

0

0

0

0

2.9

0

0

0

2.8

31.4

0

20.6

0

0

0

0

0

0

9.5

0

0

3.3

Dichloro- 1,1- 1,2- 

difluoro- Dichloro- Dichloromethane ethane ethane

0

0

ND

0

1.1

0

0

0

0

0

84.4

ND

0

0

0

29.1

0.5

82.9

0

ND

1.1

0.5

3.5

0

0

0

ND

0

0

0

0

10.4

3.0

0

0

0

0

0

61.1

0

0.2

0

0

79.5

0.2

66.8

4.3

0

0

0

6.1

0

0

0

0

0

1.0

0

0

4.0

0

1.4

0

0

0

0

35.9

0

7.1

0

0

32.5

0.9

41.9

2.9

28.6

0

0

0

1.3

1.1

1.3

0

5.8

1,1 -Dichloro Athene

0.3

0

0

6.7

3.2

0

0

0

0

0

73.3

0

0

0

0

86.9

0.5

81.5

3.8

0

0

0

7.1

0

0

0

2.7

0

Appendv 4 113
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of coimound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

B romodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

/>Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

c/s-1 ,2- 

Dichloroethene

0

1.1

0.2

7.1

4.6

0.2

0

0

ND

7.2

6.6

0

14.6

0

0

0

0

0.2

0

0.3

18.9

26.2

5.0

30.3

NA

1.8

1.5

0.2

0.8

0.5

0

0.3

0

7.8

0

0

frans-1 ,2- 

Dichloroethene

ND

0

0

9.1

9.1

0

0

0

ND

7.4

9.1

0

36.4

0

0

0

0

0

0

3.7

10

0

3.7

14.8

44.4

NA

3.7

0

0

0

0

0

0

0

0

0

Dichloromethane

10

0.9

0

24.1

14.5

0

0

0

11.1

4.3

19.3

0

30.1

5.7

0

0

0

0

0

1.8

4.9

4.5

6.0

8.5

8.5

0.9

NA

0

0

0

0

1.8

8.3

2.4

0

0

1,2- 

Dichloropropane

0

1.2

0

8.8

3.7

0

0

0

ND

1.2

7.4

0

8.6

0

0

0

0

0

0

1.2

0

4.9

12.0

6.0

1.2

0

0

NA

2.5

0

0

1.2

0

0

0

0

1 ,3- 

Dichloropropane

ND

0

0

50

10

0

0

0

ND

0

10

0

40

0

0

0

0

0

0

0

0

30

30

40

50

0

0

22.2

NA

14.3

0

0

0

0

0

0

2,2- 

Dichloropropane

ND

0

0

0

0

0

0

0

ND

0

25.0

0

0

0

0

0

0

0

0

0

50

25.0

0

50

75.0

0

0

0

25.0

NA

0

0

0

0

0

0

c/s-1 ,3- 

Dichloropropene

ND

0

0

0

0

0

0

0

ND

0

0

0

100

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NA

0

0

0

0

0

Ethyb^nzene

0

3.7

0

57.6

14.0

0

1.8

0

ND

2.5

51.7

1.8

67.8

1.9

0

0

0

0

0

1.3

0

0

1.3

1.5

2.5

0

2.5

1.3

0

0

0

NA

0

0

0

0

114 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections wh?n both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-butyl ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1 , 1 ,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1,3,5 -Trimethylbenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

C/S-1,2- 

Dichloroethene

0

0

0

22.4

2.0

0

0

0.2

0

0

68.3

0

0.5

0

0

44.3

0.2

85.3

0.5

0

0

0

9.2

0

0

0

0

0

frans-1,2- _. . , 1,2- 

_. . . Dich oro- _. ' Dichloro- Dichloro- 

.. methane ethene propane

0

ND

ND

0

0

0

0

0

0

0

63.0

ND

3.7

0

0

37.0

0

63.0

0

ND

0

0

8.0

0

0

0

ND

0

0

0

0

7.7

0

1.4

0

0.9

0

0

12.0

0

5.3

0

0

14.5

0.9

19.1

0

40.9

0

0

0

8.8

5.8

0

0

1.3

0

0

0

0

0

0

0

0

0

0

20.5

0

2.4

0

0

6.0

0

20.5

24.7

0

0

0

0

0

0

0

33.3

0

1,3- 

Dichloropropane

0

ND

ND

0

0

0

0

0

0

0

50

ND

10

0

0

40

0

40

0

ND

0

0

0

0

0

0

ND

0

2,2- 

Dichloropropane

0

ND

ND

ND

0

0

0

0

0

0

100

ND

0

0

0

50

0

100

0

ND

0

0

0

0

0

0

ND

0

c/s-1 ,3- 

Dichloropropene

0

ND

ND

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

ND

0

0

0

ND

0

0

ND

0

Ethylbenzene

0

0

50

5.7

0

1.9

1.8

2.5

0

0

3.8

0

36.6

0

0

5.0

1.3

3.8

0

88.9

3.5

3.5

0

38.9

47.6

26.7

45.8

73.1

Append'v 4 115
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1,2-Dichloroethene

t rans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

Ethylene 

dibromide

ND

0

0

12.5

14.3

0

0

0

ND

0

0

0

12.5

0

0

0

75.8

0

0

0

0

0

27.3

0

0

0

33.3

0

0

0

0

0

NA

0

0

0

Fluoro- Hexachlor 

trichloro- o-butadimethane ene

ND

9.1

0

3.6

1.8

0

0

0

ND

48.2

3.6

0

10.7

0

0

0

0

0

0

0

60.7

39.3

3.6

80

78.6

0

3.6

0

0

0

0

0

0

NA

0

0

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

ND

0

NA

0

Isopropylbenzene

ND

100

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

NA

p-lsopropyltoluene

ND

0

0

0

0

0

66.7

0

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

16.7

16.7

0

0

0

0

0

0

0

0

ND

0

0

0

Methyl 

ethyl 

ketone

0

0

0

57.1

12.5

0

0

0

0

0

25.0

0

62.5

0

0

14.3

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Me*hy' Mrmylte/t-

'ffbutyl butylether 

ketone

0

0

0

100

50

0

0

0

ND

0

50

0

100

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

100

0

0

0

0

0

2.4

0

11.5

5.1

0

0

0

0

0

8.1

0.9

14.1

0.6

0

0

0

0

0

0

0

5.1

0.6

2.4

11.8

0

0.9

0

0

0

0

0.6

0

0.6

0

0.3

116 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-butyl ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1,1,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 ,3.5-Trimethylbenzene

Vinyl chloride

w-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

Ethylene 

dibromide

0

ND

ND

0

0

0

0

0

0

0

0

ND

0

0

0

0

0

33.3

0

0

0

0

0

0

0

0

ND

0

Fluoro- Hexachlor 

trichloro- o-butadimethane ene

0

ND

ND

22.2

9.1

0

0

0

0

0

76.8

ND

0

0

0

76.8

0

87.5

0

0

0

0

14.3

0

0

0

0

0

0

ND

ND

ND

0

0

0

0

0

0

0

ND

0

0

50

0

0

0

0

ND

0

0

0

ND

0

ND

0

0

Isopropylbenzene

0

ND

ND

100

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

ND

0

p-lsopropyltoluene

NA

ND

ND

ND

0

ND

0

0

0

0

16.7

ND

0

0

0

16.7

0

16.7

0

ND

66.7

83.3

0

0

0

0

ND

ND

Methyl 

ethyl 

ketone

0

NA

0

0

0

0

0

0

0

0

12.5

40

0

0

0

0

0

0

0

ND

0

0

0

0

12.5

25.0

0

20

Methyl 

isobutyl 

ketone

0

0

NA

0

0

0

0

0

0

0

50

ND

50

0

0

0

0

0

0

ND

0

0

0

ND

100

ND

100

ND

Mef-yl tertbut M ether

0

0

0

NA

1.2

0.7

0

0

0

0

16.3

0

0.6

0

0

10.6

0

21.4

0

10.3

0.3

0

0.9

0.8

0.4

0.8

0

2.7

Appendfx4 117
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community watsr systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

«-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis-1 ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

Monochlorobenzene

ND

18.2

0

0

0

0

0

0

ND

0

0

0

22.2

0

0

0

0

0

0

0

11.1

72.2

0

59.1

59.1

0

0

0

0

0

0

0

0

22.2

0

0

Naphthalene

0

12.5

0

11.1

0

0

12.5

0

ND

0

11.1

0

0

0

0

0

0

0

0

0

0

0

11.1

0

0

0

12.5

0

0

0

0

12.5

0

0

0

0

n-Propylbenzene

ND

0

0

25.0

0

0

50

0

ND

0

25.0

0

25.0

0

25.0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

25.0

0

0

0

0

Styrene

ND

0

0

0

0

0

0

0

ND

60

0

0

0

0

0

0

0

0

0

0

0

0

0

0

20

0

20

0

0

0

ND

40

0

0

0

0

1,1,1,2- 

Tetrachloroethane

ND

0

0

0

0

0

0

0

ND

0

0

0

50

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1,1,2,2- 

Tetrachloroethane

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

Tetrachloroethylene

0

0.8

0.1

2.3

3.7

0

0

0

0

5.5

4.1

0

9.9

0

0

0

0

0.1

0

0.1

12.0

18.2

2.6

19.7

28.8

1.1

0.9

1.1

0.3

0.3

0

0.2

0

3.1

0.1

0

Tetrahydrofuran

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

118 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections wh^n both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more dete?tions of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-butyl ether

Monochlorobenzene

Naphthalene

rt-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1,1,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 ,3,5-Trimethylbenzene

Vinyl chloride

w-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

Monochlorobenzene

0

ND

ND

80

NA

0

0

0

0

0

63.6

ND

4.5

0

0

59.1

0

68.2

0

ND

0

0

40.9

0

0

0

ND

0

Naphthalene

0

0

0

40

0

NA

12.5

0

0

0

12.5

ND

12.5

28.6

0

12.5

0

0

0

25.0

25.0

12.5

0

0

0

0

0

20

n-Propylbenzene

0

ND

ND

0

0

33.3

NA

0

0

0

0

ND

25.0

0

0

0

0

0

0

0

50

50

0

0

0

0

0

0

Styrene

0

ND

ND

0

0

0

0

NA

0

0

20

ND

0

0

0

20

0

0

0

ND

0

0

0

0

0

0

ND

40

1,1,1,2- 

Tetrachloroethane

0

ND

ND

0

0

0

0

0

NA

0

0

ND

0

0

0

0

ND

0

0

ND

0

0

0

ND

ND

ND

ND

0

1,1,2,2- 

Tetrachloroethane

0

ND

ND

0

0

0

0

0

0

NA

0

ND

0

0

0

100

0

100

0

0

0

0

0

0

0

0

ND

ND

Tetrachloroethylene

0.1

2.4

14.3

17.9

0.9

0.2

0

0.1

0

0

NA

25.0

0.6

0

0.1

29.5

0.1

60.9

0.8

23.1

0.1

0.1

2.1

0

0.1

0

1.0

0.5

Tetrahydrof'iran

0

100

0

0

0

0

0

0

0

0

50

NA

0

0

0

0

0

0

0

ND

0

0

0

ND

0

ND

0

ND

Appendix 4 119
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of cormound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more defections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

/7-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis-l ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

1,2,3- 

Toluene Trichlorobenzene

0

7.1

0

24.5

5.9

0

0.9

0

16.7

0.8

17.8

1.8

35.9

0.9

0.9

0.9

0

0

0

0

0

0.9

6.3

0

2.3

0.8

4.7

1.6

0.9

0

0

23.4

0

0

0

0

ND

0

0

0

0

0

0

0

ND

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1,2,4- 1,1,1- 1,1,2- _.., 1,2,3- 

_ . ' ' . . ' ' _ . ' ' Trichloro- _ . ' Trichloro- Trichloro- Trichloro- Trichlorobenzene ethane ethane y propane

ND

0

0

16.7

16.7

0

16.7

0

ND

0

16.7

0

33.3

0

0

0

50

0

22.2

11.1

0

0

0

0

0

0

0

0

0

0

0

0

0

0

16.7

0

0

0.6

0

2.8

1.8

0

0

0.1

0

7.2

2.2

0

15.1

0

0

0

0

0

0

1.0

6.4

36.8

3.5

34.3

27.2

0.9

1.6

0.5

0.4

0.2

0

0.4

0

4.8

0

0

ND

0

0

57.1

0

0

0

0

ND

12.5

14.3

0

57.1

14.3

0

0

0

0

0

0

14.3

12.5

11.1

22.2

11.1

0

11.1

0

0

0

0

11.1

0

0

0

0

0

0.7

0.1

2.9

2.3

0

0.1

0

ND

5.4

2.9

0

8.4

0

0

0

0.3

0

0.1

0.4

11.2

19.4

3.0

21.5

34.5

1.1

1.4

1.1

0.3

0.3

0

0.2

1.0

3.3

0

0

0

0

0

0

0

0

0

0

ND

0

0

0

4.3

0

0

0

0

0

0

0

0

40.4

6.4

31.9

6.4

0

0

42.6

0

0

0

0

0

0

0

0

Trihalomethanes, 

total

ND

1.1

0

90

21.5

0

0

0

ND

0

56.0

0

94.3

1.7

0

0

0.7

0

0

0

0

0

1.9

0

0

0

4.3

0

0

0

0

8.5

0

0

0

0

120 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community wate- systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-buiyl ether

Monochlorobenzene

Naphthalene

n-Propylbenzene

Styrene

1,1, 1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethy le ne

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1,1,2-Trichloroethane

Trichloroethylene

1,2,3 -Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1,3,5-Trimethylbenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

1,2,3- 

Toluene Trichlorobenzene

0

0

7.1

2.7

0.8

1.1

0.9

0

0

0

6.9

0

NA

0

0

2.4

0

3.1

0.9

64.7

1.9

0.9

0

26.2

14.9

12.8

6.7

32.9

0

ND

ND

ND

0

100

0

0

0

0

0

ND

0

NA

0

0

0

0

0

ND

0

0

0

0

0

0

ND

0

1,2,4- 1,1,1- 1,1,2- Trich|oro. 1 '2'3' 

Trichloro- Trichloro- Trichloro- . . Trichlorobenzene ethane ethane e yene propane

0

ND

ND

0

0

0

0

0

0

0

11.1

ND

0

0

NA

0

0

22.2

0

ND

0

16.7

0

0

0

0

ND

11.1

0.1

0

0

8.5

1.2

0.3

0

0.1

0

0.1

43.5

0

0.3

0

0

NA

0.2

56.6

2.2

8.6

0.1

0

2.8

0

0

0

0

0.4

0

ND

ND

0

0

0

0

0

0

0

25.0

ND

0

0

0

25.0

NA

22.2

0

0

0

0

0

0

0

0

0

0

0.1

0

0

17.3

0.9

0

0.1

0

0

0.1

59.4

0

0.3

0

0.1

37.3

0.1

NA

1.8

0

0

0

2.0

0.1

0

0

0

0.5

0

0

ND

0

0

0

0

0

0

0

25.5

0

2.1

0

0

44.7

0

57.4

NA

ND

0

0

0

0

0

0

ND

0

Trfhalomethanes, 

ntal

0

ND

ND

4.1

0

0.6

0

0

0

0

11.4

ND

5.9

0

0

1.4

0

0

0

NA

0

0

0

1.6

4.6

1.6

9.9

17.2

Append!" 4 121
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

Acetone

Benzene

Bromochloromethane

Bromodichloromethane

Bromoform

Bromomethane

n-Butylbenzene

sec-Butylbenzene

Carbon disulfide

Carbon tetrachloride

Chlorodibromomethane

Chloroethane

Chloroform

Chloromethane

o-Chlorotoluene

p-Chlorotoluene

Dibromochloropropane

Dibromomethane

o-Dichlorobenzene

p-Dichlorobenzene

Dichlorodifluoromethane

1 , 1 -Dichloroethane

1 ,2-Dichloroethane

1 , 1 -Dichloroethene

cis- 1 ,2-Dichloroethene

trans- 1 ,2-Dichloroethene

Dichloromethane

1 ,2-Dichloropropane

1 ,3-Dichloropropane

2,2-Dichloropropane

cis- 1 ,3-Dichloropropene

Ethylbenzene

Ethylene dibromide

Fluorotrichloromethane

Hexachlorobutadiene

Isopropylbenzene

1,2,4- 1,3,5- 

Trimethyl- Trimethylbenzene benzene

0

0

3.8

4.0

0

0

65.4

0

ND

0

4.0

0

12.0

0

0

0

0

0

0

0

7.7

0

0

0

0

0

0

0

0

0

0

7.7

0

0

0

0

ND

0

4.3

4.3

0

0

69.6

0

ND

0

4.3

0

13.0

0

0

0

0

0

4.3

0

4.3

0

0

0

0

0

0

0

0

0

0

8.7

0

0

0

0

Vinyl 

chloride

ND

0

0

28.8

25.4

0

0

0

ND

3.2

27.1

0

30.5

0

0

0

0

0

1.6

0

12.1

45.0

0

81.1

93.5

3.2

0

0

0

0

0

0

0

20.7

0

0

m-Xylene

ND

0

0

30.4

34.8

0

0

0

ND

0

34.8

0

47.8

0

0

0

0

0

0

0

0

0

0

0

0

0

9.7

0

0

0

0

23.3

0

0

0

0

o-Xylene

14.3

0

0

51.3

23.7

0

0

0

ND

0

46.2

2.3

56.4

2.4

0

0

0

0

0

4.3

0

0

2.1

0

0

0

6.4

0

0

0

0

43.5

0

0

0

0

p-Xylene

ND

0

0

57.1

35.7

0

0

0

ND

0

64.3

0

78.6

0

0

0

0

0

0

0

0

0

6.7

0

0

0

0

0

0

0

0

28.6

0

0

0

0

m-&pXylenes

14.3

0

0

75.0

17.4

0

0

0

ND

0

62.5

4.2

70.8

5.3

0

0

0

0

0

0

0

0

0

4.2

0

0

0

4.2

0

0

0

42.3

0

0

0

0

Xylenes, 

total

ND

7.6

0

50.8

12.5

0

0

0

ND

0.9

39.1

0

67.7

0

0

0

0

0

1.0

1.0

0

0

3.8

0

0

0

1.0

0

0

0

0

46.7

0

0

0

0

122 Occurrence and Distribution of MTBE and Other VOCs in Drinking Water 

in the Northeast and Mid-Atlantic Regions of the United States
Appendix 4. Co-occurrence of volatile organic compounds in drinking water for randomly selected community water systems 

in the study area, 1993-98-Continued

[Co-occurrence is calculated as the percentage of samples with detections of compound specified by column that also had detections of compound 

specified by row, for example, 2.2 percent of the drinking-water samples with benzene detections also had bromochlormethane detections when both 

compounds were analyzed for in the same sample; values shown in bold when co-occurrence equals or exceeds 20 percent of 10 or more detections of 

compound specified by column; NA, not applicable; ND, no detections of compound specified by column]

Co-occurrence, in percent

VOC

p-Isopropyltoluene

Methyl ethyl ketone

Methyl isobutyl ketone

Methyl tert-buiy\ ether

Monochlorobenzene

Naphthalene

/i-Propylbenzene

Styrene

1,1,1 ,2-Tetrachloroethane

1 , 1 ,2,2-Tetrachloroethane

Tetrachloroethylene

Tetrahydrofuran

Toluene

1 ,2,3-Trichlorobenzene

1 ,2,4-Trichlorobenzene

1,1,1 -Trichloroethane

1 , 1 ,2-Trichloroethane

Trichloroethylene

1 ,2,3-Trichloropropane

Total Trihalomethanes

1 ,2,4-Trimethylbenzene

1 ,3 ,5-Trimethylbenzene

Vinyl chloride

m-Xylene

o-Xylene

p-Xylene

m- & p-Xylenes

Xylenes (total)

1,2,4- 1,3,5- 

Trimethyl- Trimethylbenzene benzene

15.4

0

0

25.0

0

28.6

7.7

0

0

0

3.8

ND

7.7

0

0

3.8

0

0

0

0

NA

73.1

0

5.0

0

0

0

33.3

21.7

ND

ND

0

0

14.3

8.7

0

0

0

4.3

ND

4.3

0

4.3

0

0

0

0

0

82.6

NA

0

0

0

0

0

57.1

Vinyl 

chloride

0

ND

ND

10.3

14.5

0

0

0

0

0

51.6

ND

0

0

0

48.4

0

51.6

0

ND

0

0

NA

0

0

0

0

0

m-Xylene

0

0

ND

20

0

0

0

0

0

0

0

ND

37.9

0

0

0

0

3.2

0

100

3.4

0

0

NA

69.7

57.1

NA

NA

o-Xylene

0

10

25.0

8.3

0

0

0

0

0

0

2.1

0

29.5

0

0

0

0

0

0

85.7

0

0

0

63.9

NA

47.8

100

NA

p-Xylene

0

25.0

ND

33.3

0

0

0

0

0

0

0

ND

35.7

0

0

0

0

0

0

100

0

0

0

57.1

78.6

NA

NA

NA

m- &pXylenes

0

0

12.5

0

0

0

0

0

0

0

4.2

0

12.0

0

0

0

0

0

0

87.5

0

0

0

ND

57.7

ND

NA

NA

Xy'enes, 

total

0

25.0

ND

10.6

0

1.5

0

1.9

0

0

2.8

ND

26.7

0

0.9

1.9

0

2.8

0

100

3.2

6.3

0

40.9

35.7

42.9

0

NA

Appendi^4 123

* U.S. GOVERNMENT PRINTING OFFICE: 2001 673-482 / 60016 Region No. 8