Oxygenates in Water:

Critical Information

and Research Needs

EPA

United States Office of Research EPA/600/R-98/048

Environmental Protection and Development December 1998

Agency Washington, DC 20460
EPA/600/R-98/048

December 1998

Oxygenates in Water:

Critical Information

and Research Needs

Office of Research and Development

U.S. Environmental Protection Agency

Washington, DC 20460
ii

Disclaimer

This document has been reviewed in accordance with U.S. Environmental Protection

Agency policy and approved for publication. Mention of trade names or commercial products

does not constitute endorsement or recommendation for use.
iii

Table of Contents

Page

U.S. Environmental Protection Agency Task Group ......................... v

External Reviewers .................................................. ix

Preface ........................................................... xi

1. INTRODUCTION ............................................... 1

2. SOURCE CHARACTERIZATION .................................. 5

2.1 Background ................................................ 5

2.2 Needs ..................................................... 8

3. TRANSPORT .................................................. 9

3.1 Background ................................................ 9

3.2 Needs ..................................................... 10

4. TRANSFORMATION ............................................ 11

4.1 Background ................................................ 11

4.2 Needs ..................................................... 12

5. OCCURRENCE ................................................. 13

5.1 Background ................................................ 13

5.2 Needs ..................................................... 18

6. EXPOSURE .................................................... 19

6.1 Background ................................................ 19

6.2 Needs ..................................................... 22

7. AQUATIC TOXICITY ........................................... 23

7.1 Background ................................................ 23

7.2 Needs ..................................................... 23

8. HEALTH EFFECTS ............................................. 24

8.1 Background ................................................ 24

8.2 Needs ..................................................... 25

9. RELEASE PREVENTION ......................................... 26

9.1 Background ................................................ 26

9.2 Needs ..................................................... 29
iv

Table of Contents

(cont’d)

Page

10. CONTAMINANT REMOVAL .................................... 29

10.1 Background .............................................. 29

10.2 Needs ................................................ 33

10.2.1 Remediation Needs .................................. 34

10.2.2 Drinking-Water Treatment Needs ....................... 35

11. CONCLUSIONS ............................................... 37

REFERENCES ..................................................... 39

APPENDIX 1: Chemical Properties of Selected Oxygenates ................... 49

APPENDIX 2: Current Projects Related to Oxygenates in Water ............... 51
v

U.S. Environmental Protection Agency Task Group

Principal Authors

J. Michael Davis (Chair)

Office of Research and Development

National Center for Environmental 

Assessment

Research Triangle Park, NC 27711

John Brophy

Office of Air and Radiation

Office of Mobile Sources

Washington, DC 20001

Robert Hitzig

Office of Solid Waste and Emergency 

Response

Office of Underground Storage Tanks

Washington, DC 20460

Fran Kremer

Office of Research and Development

National Risk Management Research 

Laboratory

Cincinnati, OH 45268

Michael Osinski

Office of Water

Office of Groundwater and Drinking Water

Washington, DC 20460

James D. Prah

Office of Research and Development

National Health and Environmental 

Effects Research Laboratory

Research Triangle Park, NC 27711

Stephen Schmelling

Office of Research and Development

National Risk Management Research 

Laboratory

Ada, OK 74821-1198

Thomas F. Speth

Office of Research and Development

National Risk Management Research 

Laboratory

Cincinnati, OH 45268

Robert Swank

Office of Research and Development

National Exposure Research Laboratory

Athens, GA 30605-2720

Anthony N. Tafuri

Office of Research and Development

National Risk Management Research 

Laboratory

Edison, NJ 08837

Candida West

Office of Research and Development

National Risk Management Research 

Laboratory

Ada, OK 74821-1198

Contributors

Dorothy Canter

Office of Solid Waste and Emergency 

Response

Office of the Assistant Administrator

Washington, DC 20460

Stanley Durkee

Office of Research and Development

Office of Science Policy

Washington, DC 20460
vi

U.S. Environmental Protection Agency Task Group

(cont’d)

Contributors (cont’d)

Jackson Ellington

Office of Research and Development

National Exposure Research Laboratory 

Athens, GA 30605-2720

Charles Freed

Office of Air and Radiation

Office of Mobile Sources

Washington, DC 20001

Frank Gostomski

Office of Water

Office of Science and Technology

Washington, DC 20460

Judith A. Graham

Office of Research and Development

National Exposure Research Laboratory

Research Triangle Park, NC 27711

Matthew Hagemann

Region 9

San Francisco, CA 94105

John Helvig

Region 7

Kansas City, KS 66101

Roland Hemmet

Region 2

New York, NY 10007-1866

Robert W. Hillger

Region 1

Boston, MA 02203

Kenneth T. Knapp

Office of Research and Development

National Exposure Research Laboratory

Research Triangle Park, NC 27711

Amal Mahfouz

Office of Water

Office of Science and Technology

Washington, DC 20460

Michael Moltzen

Region 2

New York, NY 10007-1866

Richard Muza

Region 8 

Denver, CO 80202

Charles Ris

Office of Research and Development

National Center for Environmental 

Assessment

Washington, DC 20460

Bill Robberson

Region 9

San Francisco, CA 94105

Gary Timm

Office of Prevention, Pesticides, and

Toxic Substances

Washington, DC 20460

Jim Weaver

Office of Research and Development

National Exposure Research Laboratory

Athens, GA 30605-2720

Lester Wyborny II

Office of Air and Radiation

Office of Mobile Sources

Ann Arbor, MI 48105-2498
vii

U.S. Environmental Protection Agency Task Group

(cont’d)

Members

Charles Auer

Office of Prevention, Pesticides, and 

Toxic Substances

Washington, DC 20460

Ben Blaney

Office of Research and Development

National Risk Management Research 

Laboratory

Cincinnati, OH 45268

Dave Brown

Office of Research and Development

National Exposure Research Laboratory

Athens, GA 30605-2720

Rebecca L. Calderon

Office of Research and Development

National Health and Environmental Effects 

Research Laboratory

Research Triangle Park, NC 27711

Tudor Davies

Office of Water

Office of Science and Technology

Washington, DC 20460

Joe A. Elder

Office of Research and Development

National Health and Environmental Effects 

Research Laboratory

Research Triangle Park, NC 27711

William H. Farland

Office of Research and Development

National Center for Environmental 

Assessment

Washington, DC 20460

Rene Fuentes

Region 10

Seattle, WA 98101

Lester D. Grant

Office of Research and Development

National Center for Environmental 

Assessment

Research Triangle Park, NC 27711

Fred Hauchman

Office of Research and Development

National Health and Environmental Effects 

Research Laboratory

Research Triangle Park, NC 27711

Steven F. Hedtke

Office of Research and Development

National Health and Environmental Effects 

Research Laboratory

Duluth, MN 

John Heffelfinger

Office of Solid Waste and Emergency

Response

Office of Underground Storage Tanks

Washington, DC 20460

Ronald Landy

Region 3

Philadelphia, PA 19107

Maureen Lewison

Office of Solid Waste and Emergency

Response

Office of Underground Storage Tanks 

Washington, DC 20460
viii

U.S. Environmental Protection Agency Task Group

(cont’d)

Members (cont’d)

Dennis McChesney

Region 2

New York, NY 10007-1866

John Mooney

Region 5

Chicago, IL 60604-3507

Margo Oge

Office of Air and Radiation

Office of Mobile Sources

Washington, DC 20460

Charles Sands

Office of Solid Waste and Emergency

Response

Washington, DC 20460

Paul Scoggins

Region 6

Dallas, TX 75202-2733 

Winona Victery

Region 9

San Francisco, CA 94105

Michael Watson

Region 10

Seattle, WA 98101

Jeanette Wiltse

Office of Water

Office of Science and Technology

Washington, DC 20460

Lynn Wood

Office of Research and Development

National Risk Management Research 

Laboratory

Ada, OK 74821-1198

Donn Zuroski

Region 9

San Francisco, CA 94105
ix

External Reviewers*

David Ashley

National Center for Environmental Health

U.S. Centers for Disease Control and 

Prevention

Atlanta, GA 30341-3724

Bruce Bauman

American Petroleum Institute

Washington, DC 20005-4070

Steven Book

California Department of Health Services,

Drinking Water

Sacramento, CA 94234-7320

Robert Borden

North Carolina State University

Raleigh, NC 27695

Susan Borghoff

Chemical Industry Institute of Toxicology

Research Triangle Park, NC 27709-2137

Herb Buxton

Toxic Substances Hydrology Program

U.S. Geological Survey

West Trenton, NJ 08628

Maria Costantini

Health Effects Institute

Cambridge, MA 02139-3180

James S. Crowley

Santa Clara Valley Water District

San Jose, CA 95118-3686

Joan Denton

California Air Resources Board

Sacramento, CA 95814

Gary Ginsberg

Connecticut Department of Public Health

Hartford, CT 06134-0308

Bernard Goldstein (Workshop Chair)

Department of Environmental Community

Medicine

Environmental and Occupational Health

Sciences Institute

Piscataway, NJ 0885-1179

Anne Happel

Environmental Restoration Division

Lawrence Livermore National Laboratory

Livermore, CA 94551

Carol Henry

American Petroleum Institute

Washington, DC 20005-4070

Michael Kavanaugh

Malcolm Pirnie, Inc

Oakland, CA 94612

John Kneiss

Oxygenated Fuels Association

Arlington, VA 22209 

Jerold Last

UC Toxic Substances Research and

Teaching Program

University of California-Davis

Davis, CA 95616-8723

Ronald Melnick

National Institute of Environmental Health

Sciences

Research Triangle Park, NC 27709

James Pankow

Oregon Graduate Institute

Portland, OR 97291-1000

Hari Rao

Edison, NJ 08820
x

External Reviewers

(cont’d)

Thomas Skower

Underwriters Laboratories, Inc.

Northbrook, IL 60062

Arthur Stewart

Oak Ridge National Laboratory

Oak Ridge, TN 37831-6036

John H. Sullivan

Government Affairs Office

American Water Works Association

Washington, DC 20005

Robert Tardiff

Sapphire Group, Inc.

Bethesda, MD 20814

Barbara Walton / Rosina M. Bierbaum

Office of Science and Technology 

Policy - Environment Division

Executive Office of the President

Washington, DC 20502

Clifford Weisel

Exposure Measurement and Assessment

Division

Environmental and Occupational Health

Sciences Institute

Piscataway, NJ 08855-1179

John Zogorski

U.S. Geological Survey

Water Resources Division

Rapid City, SD 57702

*These individuals provided technical review comments by invited participation in a review workshop

held on October 7, 1997 and/or by written submissions.
xi

Preface

The purpose of this document is to identify key issues related to assessing and managing the

potential health and environmental risks of oxygenate contamination of water. Oxygenates are

chemicals added to fuels (“oxyfuels”) to increase the oxygen content and thereby reduce

emissions from use of the fuel. This document builds on and extends an earlier report, Oxyfuels

Information Needs (U.S. Environmental Protection Agency, 1996), which included water issues

but tended to focus more on inhalation health risk issues. The present document focuses on those

gaps and limitations in current information that constitute the most critical and immediate needs to

be addressed in support of risk assessment and risk management efforts related to oxygenates in

water. This document is primarily intended to serve as a starting point and general guide to

planning future research. It is not a comprehensive review of issues pertaining to oxygenates in

water, nor does it describe in detail specific studies or projects that are needed.

Efforts to address many of the needs identified in this document have already begun or are

under consideration by various organizations. A current listing of such projects may be found in

Appendix 2.
1

1 μg/L = 1 part per billion (ppb).

1

1. INTRODUCTION

Contamination of ground and surface waters by motor vehicle fuels and fuel additives is not

a new problem, given the history and pervasive use of fuels in the 20th century. Well over a

million underground fuel storage tanks exist in the United States, and leaks from these tanks have

been the focus of major programs to prevent or clean up such releases. Transport of fuels via

pipelines and in bulk containers also presents the potential for accidental releases and consequent

environmental contamination. Experience suggests that contamination from these and other

sources of fuel releases can affect water quality and the biota that depend upon the water,

including human populations. 

Against this background of experience with fuel-related contamination of ground and

surface waters, recent events have focused attention on what appear to be somewhat different

characteristics associated with fuels containing chemicals known as oxygenates. Oxygenates are

added to fuel to increase its oxygen content and thereby reduce certain emissions from use of the

fuel. Of the several ethers and alcohols that may serve as oxygenates, methyl tertiary butyl ether

(MTBE) is the most frequently used. Monitoring of groundwater quality by the U.S. Geological

Survey (USGS) indicates that MTBE has become detectable in shallow groundwater samples in

certain urban areas in recent years, with concentrations ranging from below the reporting level of

0.2 μg/L1 to over 20,000 μg/L (Squillace et al., 1996). Reports of point-source MTBE

contamination of drinking water sources at well over 100 μg/L, including aquifers serving as the

primary source of drinking water for the city of Santa Monica, CA (California Department of

Health Services, 1998), raise several important questions about potential environmental and public

health impacts of oxygenated fuels.

A key question is whether oxygenates in water pose a significant threat to human health or

the environment. To assess the risks of MTBE or any other oxygenate, the potential for exposure

to, and effects of, the contaminant(s) must be characterized. However, only limited information

exists for characterizing the possible risks of oxygenates in water. For example, the extent of

population exposures to MTBE in drinking water is unknown. Even in cases where MTBE is

clearly present in public or private water supplies, limited guidance exists for determining levels
2

that would be acceptable or unacceptable from the standpoint of public health or consumer

acceptability. The U.S. Environmental Protection Agency (EPA) Office of Water has released a

Drinking Water Advisory for MTBE (U.S. Environmental Protection Agency, 1997). As the full

title of the document indicates, it provides “Consumer Acceptability Advice and Health Effects

Analysis on [MTBE].” The Advisory “recommends that keeping levels of contamination in the

range of 20 to 40 μg/L or below to protect consumer acceptance of the water resource also

would provide a large margin of exposure (safety) from toxic effects.” However, the document

discusses “many uncertainties and limitations associated with the toxicity data base for this

chemical” and notes the consequent difficulty in estimating a health protection level for MTBE in

drinking water. The uncertainties in assessing the health risks of MTBE are reflected somewhat

in the various guidance values (e.g., advisories, action levels, standards) that have been issued by

individual states, ranging at one time from 35 μg/L in California to 230 μg/L in Illinois

(Interagency Oxygenated Fuels Assessment Steering Committee, 1997). As efforts to assess

health risks and derive guidance values continue at the local, state, and federal levels, the need for

an adequate scientific foundation for these efforts intensifies. Without more definitive scientific

information, uncertainties will continue to dominate risk assessments of oxygenates.

If it is concluded that a risk or problem exists, other questions face risk managers in

formulating actions to address oxygenate contamination of water. For example, What are the

sources of contamination? How long is it likely to persist? How widespread is the

contamination? What cost-effective methods exist to remove the contaminant(s) from water?

and, How can further contamination be avoided? A recent review of fuel oxygenates and water

quality (Interagency Oxygenated Fuels Assessment Steering Committee, 1997) notes that for

various reasons, including the potentially greater persistence of MTBE in ground water than other

components of gasoline, remediation of MTBE-contaminated ground water may pose unique

problems. The Interagency Assessment also notes the possibility that ground water could be

contaminated by deposition of oxygenates from the ambient atmosphere. A quantitative answer

to whether non-point sources or point sources, such as leaking underground storage tanks

(USTs), pose a greater potential risk of environmental contamination is not available.

Risk assessment and risk management require information that is generally obtained through

research, data collection, or analysis of data that already exist. The purpose of this document is to

identify the key information needed to assess and manage the potential health and environmental
3

risks related to oxygenates in water. This document builds on an earlier report, Oxyfuels

Information Needs (U.S. Environmental Protection Agency, 1996), which encompassed water

issues but tended to emphasize inhalation health risk issues. As noted in Oxyfuels Information

Needs, the benefits and risks of any given oxyfuel must be assessed in relation to an alternative,

such as conventional gasoline. A comparative assessment of the potential risks or benefits of any

given fuel in relation to any other fuel is obviously a complex, multifaceted endeavor (see U.S.

Environmental Protection Agency, 1992). The present document is much more limited in scope. 

It focuses on key information required to support the most pressing risk assessment and risk

management needs pertaining to oxygenates in water, with the aim of achieving progress more

readily than would be possible by attempting to cover every possible issue in a comprehensive

manner. However, one should not lose sight of the broader and perhaps ultimate issue of the need

to examine quantitatively the trade-offs between sought improvements in air quality through the

use of oxygenates and possible reductions in water quality through oxygenate contamination.

This document is primarily intended to serve as a starting point and general guide to

planning research related to oxygenates in water. It does not attempt to describe in detail specific

studies and projects that are needed. Nor is this document a formal assessment of environmental

or health risks associated with oxygenates or an in-depth analysis of candidate risk management

options for addressing this problem. Other reports are available for more detailed reviews of the

health and environmental effects of oxygenates (e.g., U.S. Environmental Protection Agency,

1993, 1994; Health Effects Institute, 1996; Interagency Oxygenated Fuels Assessment Steering

Committee, 1996, 1997; National Research Council, 1996), particularly the “Water Quality”

chapter from the Interagency Assessment of Oxygenated Fuels (Interagency Oxygenated Fuels

Assessment Steering Committee, 1997). Note that all of these reports have pointed out the lack

of adequate information to assess fully and definitively the risks and benefits associated with

oxyfuels in comparison to conventional fuels.

Some brief background information on why fuel oxygenates are used may be helpful. 

The 1990 Clean Air Act Amendments (CAAA) created two fuel programs to be administered by

EPA requiring use of oxygenates (U.S. Code, 1990). The first program began in the fall of 1992

with the objective of reducing carbon monoxide (CO) emissions in several areas of the country

where the National Ambient Air Quality Standard (NAAQS) for CO was exceeded. Under this

program, the CAAA required the sale of gasoline with an oxygen content of 2.7% by weight
4

during the cold weather season in designated areas that failed to attain the NAAQS for CO. 

The second program required the year-round use of reformulated gasoline (RFG) containing

2.0% oxygen by weight, beginning in 1995, in selected areas having the highest levels of

tropospheric ozone. In addition to reducing emissions of ozone precursors, the RFG program

also was intended to help reduce the emissions of certain toxic organic air pollutants. 

Collectively, cold-weather oxygenated gasoline and year-round RFG with oxygenate may be

referred to as “oxyfuels.”

Although MTBE and, to a lesser extent, ethanol currently dominate the marketplace, no

specific oxygenate is required or designated by the 1990 CAAA. Several other ethers and

alcohols also may serve as oxygenates and could become more prevalent, depending on various

factors such as cost, ease of production and transfer, and blending characteristics. These

oxygenates include ethyl tertiary butyl ether (ETBE), tertiary amyl methyl ether (TAME), tertiary

amyl ethyl ether (TAEE), diisopropyl ether (DIPE), dimethyl ether (DME), and tertiary butanol

(TBA). The chemical properties of several oxygenates are listed in Appendix 1. To achieve the

specified oxygen content requirements, approximately 15%-vol MTBE or 7.5%-vol ethanol can

be used to yield the 2.7%-wt oxygen for the winter fuel program and approximately 11%-vol

MTBE or 5.5%-vol ethanol for the 2.0%-wt oxygen required by the RFG fuel program.

According to EPA’s Office of Mobile Sources, about 30% of U.S. gasoline currently

contains some form of oxygenate for air quality improvement purposes. Beginning in the late

1970s, MTBE and ethanol were used to increase the octane value of gasoline in the United States

as lead was phased out. Approximately 25% or more of U.S. fuel may have contained MTBE or

ethanol as an octane-enhancer in a given year, but the current usage of MTBE for octane is

considerably lower, constituting perhaps 3 to 5% of the fuel supply. These levels of usage are

subject to alteration as economic variables (e.g., the price of crude oil) and other factors change. 

The concentration of MTBE used for octane purposes in conventional gasoline may vary widely

up to an allowable limit of 15%-vol MTBE, depending on other constituents and properties of the

fuel, but likely is more on the order of 1 to 8%-vol MTBE. Gasoline containing 10% ethanol,

often referred to as “gasohol,” represents about 10% of all gasoline sold in the United States, but

may be much more prevalent in certain locales, particularly in the Midwest. More than

10 billion kg MTBE was used in U.S. gasoline in 1996, and fuel ethanol use was about 3 billion

kg (DeWitt & Company, Incorporated, 1997).
5

This document applies to all ether and alcohol oxygenates unless otherwise stated. It refers

more to MTBE because of its predominant use and because more information is available for

MTBE than for other ethers and alcohols (except perhaps for ethanol). Nevertheless, it should

not be inferred that the only oxygenate warranting attention is MTBE or, for that matter, that the

issues identified here are necessarily unique to oxyfuels.

This document is organized around the following headings:

C Source Characterization

C Transport

C Transformation

C Occurrence

C Exposure

C Aquatic Toxicity

C Health Effects

C Release Prevention

C Contaminant Removal

Within each of these areas, a brief background section highlights available information on key

issues, followed by a section that identifies research or other information gaps that emerge as

needs. Note that the grouping of topics is somewhat arbitrary. The overlap in various areas

should be seen as a potential benefit in terms of combining objectives and resources for projects

that can be feasibly and appropriately linked. Such leveraging of resources could extend across

organizational boundaries as well.

2. SOURCE CHARACTERIZATION

2.1 Background

Releases of fuel oxygenates occur during manufacture, distribution, storage, and use,

particularly from point sources such as USTs, pipelines, and refueling facilities. According to the

Toxics Release Inventory (TRI), releases of MTBE from production sources in the United States

amounted to approximately 1.7 million kg in 1996 (U.S. Environmental Protection Agency,

1998a). Of this total, about 97% was released to the air and less than 3% was discharged to
6

surface water. For mobile sources, assuming 10 billion kg MTBE used in gasoline (DeWitt &

Company, Incorporated, 1997) and an average U.S. corporate fleet emission rate of

approximately 3.6 mg MTBE per gram MTBE in fuels (Wyborny, 1997, 1998), total motor

vehicle emissions of MTBE in 1996 would have been on the order of 40 million kg in the United

States.

Impacts to water resources can be loosely grouped into two categories: (1) widespread

impacts occurring at low concentrations and (2) local impacts occurring at high concentrations. 

The first group is often the result of indirect sources, such as vehicular emissions of oxygenates

that dissolve in rainfall and subsequently infiltrate to ground water, and may be spread over large

areas. Also, leakage from motorized recreational water craft can be considered a diffuse source

of contamination of surface water bodies such as reservoirs. The second category results from

direct releases to surface and ground water from such sources as leaking USTs, pipelines, or tank

cars.

Oxygenates in the atmosphere degrade with a half-life as short as 3 days (Smith et al., 1991;

Wallington et al., 1988). However, MTBE is soluble in water and, because of its relatively low

Henry’s Law constant, partitions readily from air to rainfall and snowfall. The concentration in

precipitation is determined primarily by the concentration in the atmosphere, the Henry’s Law

constant at a given air temperature, the time that the precipitation is exposed to MTBE, and other

characteristics of the precipitation that determine contact efficiency, e.g., rain droplet size and

snowflake surface area (Hoff et al., 1998). This process could result in deposition to land surface

and subsequent contamination of surface and ground water. Also, MTBE could accumulate in

snow at sites such as service stations, parking lots, and city streets and be released as a pulse

source to soil or ground water as the snow melts. The detection of MTBE in 41 (7%) of

592 stormwater samples collected in 16 cities and metropolitan areas from 1991 to 1995, with the

highest percentage of detections found in samples collected during high MTBE usage winter

months (Delzer et al., 1996), is consistent with atmospheric washout of MTBE in rain or snow to

the ground surface. Measured concentrations of MTBE in the stormwater samples ranged from

0.2 to 8.7 μg/L, with a median of 1.5 μg/L. Modeling calculations have predicted MTBE

concentrations in rainwater ranging from <1 μg/L to 3 μg/L, within the range of concentrations

actually found in groundwater samples (Interagency Oxygenated Fuels Assessment Steering

Committee, 1997). Also, modeling of the transport of MTBE from land surface to water table by
7

the infiltration of rain water, for a variety of infiltration and evapotranspiration scenarios, suggests

that the concentration of MTBE in groundwater two meters below the water table can range from

zero to almost 200 percent of the concentration in the rain water (Pankow et al., 1997). The use

of shallow ground water for public and private water supplies makes such nonpoint contamination

a potential public health issue as well as an environmental quality issue.

Direct releases of MTBE and other fuel oxygenates to surface and groundwater sources of

drinking water also occur. The majority of direct releases of MTBE to surface water reported to

TRI were attributable to only a few petroleum product facilities. However, refueling and

operation of boats and other recreational water craft also are suspected as significant sources of

releases of MTBE to surface waters in heavily used recreational areas. Detections of MTBE in

some drinking water reservoirs in California have prompted studies on the input of MTBE to

surface waters via recreational watercraft, precipitation, and snowmelt runoff (e.g., Reuter et al.,

1998; Dale et al., 1997). Other possible sources of MTBE releases to surface water could include

wastewater treatment operations at petroleum operations and publicly owned treatment works.

Leaking USTs are believed to be the primary source of localized releases of MTBE in high

concentrations. According to EPA’s Office of Underground Storage Tanks (OUST), nearly

1 million federally regulated USTs are currently in use at approximately 360,000 facilities in the

United States. Not all of these USTs contain oxyfuels or gasoline with MTBE or ethanol as

octane enhancers, but it can be roughly estimated that about 50% of the gasoline sold in the

United States in recent years has contained MTBE or ethanol (U.S. Department of Energy, 1995). 

Some of the earliest documented UST releases involving MTBE occurred in Maine in the

mid-1980s (Garrett, 1987). More recently, drinking water wells in Santa Monica, CA, were shut

down because of MTBE contamination from one or more leaking USTs (Geraghty & Miller,

Incorporated, 1996). Since 1988, 330,000 confirmed releases from regulated USTs have been

reported to EPA/OUST. Based on historical trends, OUST estimates that 100,000 additional

releases will be reported during the next few years as existing USTs are upgraded, closed, or

replaced. This estimate does not include an even greater number of federally unregulated storage

tanks. Although EPA regulations (§280.21, Code of Federal Regulations, 1990) require that all

USTs be upgraded, closed, or replaced by December 1998, current estimates indicate that 25 to

35% of USTs will not be in compliance by that date.
8

Despite recent and ongoing studies, it is not clear whether the greater impact from MTBE

or other fuel oxygenates to ground water is from diffuse or point sources (i.e., what fraction of

the MTBE or other oxygenate load and exposure is diffuse [e.g., from precipitation] or is related

specifically to spills or leaks from fuel containers). Although relatively high groundwater

concentrations may be readily associated with point source releases, concentrations on the order

of 10 μg/L or lower could be associated with nonpoint sources as well as point sources

(Interagency Oxygenated Fuels Assessment Steering Committee, 1997).

2.2 Needs

A model linking air to land to surface water and ground water fate for oxygenates needs to

be developed and tested. Such an airshed-watershed model could be used to conduct ecosystem

exposure assessments, serve as a key input to human exposure assessments, design management

and remediation strategies, and assist in source identification and apportionment. In particular,

the model could be used to predict upper limit values of surface and ground water concentrations

from ambient sources that could be compared to measured values, such as those expected from

the ongoing USGS study at Glassboro, NJ (Baehr and Ayers, 1997). A recent review of the

environmental behavior and fate of MTBE by Squillace et al. (1997) summarizes important

transport and transformation processes that must be included in such a model. The model could

build on recent work by Pankow et al. (1997) and Malcolm Pirnie, Incorporated (1998a) on

modeling the ground water impacts from atmospheric washout and surface water impacts from

the use of two-stroke engines. The model also could be used to estimate snow blanket buildup of

oxygenates and subsequent release at first thaw, with the results then compared to data from field

studies as a test of this potential pulse loading mechanism in a watershed. Once this modeling

tool is developed and tested, it could be used to provide a national estimate of ambient

contributions to surface and shallow ground water. It also could be used to provide point and

non-point source aggregate concentrations within specific watersheds as a function of time

(season) for total exposure assessment purposes.

The relative loads or fluxes of the oxygenates to surface and ground waters from point

sources versus diffuse (nonpoint) sources must be more accurately determined. A possible

approach to addressing this need might be the identification of a “source signature” for

oxygenates that would permit reliable source identification, and perhaps even source
9

apportionment, when used in conjunction with fate models. Although the identification of a

source signature would be very useful, the feasibility of doing so is unclear, and attempts to

provide similar signatures for other environmental contaminates do not provide much cause for

optimism. Consequently, this has to be rated as a lower priority than the development of the

multimedia model described above.

3. TRANSPORT

3.1 Background

Oxygenates may enter both surface and ground water from diffuse and point sources (see

Section 2, Source Characterization). In the case of scavenging from the atmosphere to

precipitation, numerical modeling by Pankow et al. (1997) indicates that MTBE would transfer

from the unsaturated zone into the saturated zone. However, no field observations of MTBE

concentrations in ground water during and after precipitation or snow melt events are known to

have been conducted.

The transport of oxygenates, particularly MTBE, through aquifers would be expected to

occur at nearly the same velocity as the ground water. In a mixed-composition contaminant

source, such as is found in oxygenated fuels, each individual component will travel at a rate

dependent on its water solubility and sorption tendency for soil. Oxygenates generally are more

soluble in water and less sorbed to soils than the other major organic compounds in gasoline,

namely, benzene, toluene, ethylbenzene, and xylenes (BTEX). Given sufficient time and distance,

each component of the mixture will separate within the plume according to basic chromatographic

principles. Consequently, MTBE and other oxygenates would be expected to be at the leading

edge of the plume or, in the extreme case over a long period of time, could become completely

separated from the rest of the plume if the original source of oxygenate were eliminated. 

If biodegradation of the oxygenate occurs (see Section 4, Transformation), it will interact with the

transport process such that the front may appear to recede or be stabilized.

Generally, aquifer vulnerability to oxygenate contamination can be predicted using current

wellhead protection models on a case-by-case basis. The required parameters for these models

are hydrologic, geologic, and contaminant-specific. The required chemical data for modeling
10

oxygenate transport are generally known, but transformation rates for the subsurface soil, vadose

zone, and aquifers are required to run these models. The vulnerability of deep aquifers to

oxygenate contamination is not well documented. In particular, the threat to deep aquifers due to

abandoned wells and/or karst topography has not been assessed. Similarly, the threat to surface

streams and lakes has not been assessed, even though suitable fate models for both exist. Again,

adequate oxygenate loading models and fate parameters are needed to apply these models,

particularly biodegradation rates, photolysis rates, and net air-water exchange rates.

3.2 Needs

Given the progress made in the last several years on modeling the fate (transport and

transformation) of organic compounds, particularly BTEX compounds, in soils, ground water,

and surface water, reasonable estimates of transport between and through environmental media

can be made for oxygenates. For example, MTBE is expected to move through soil and ground

water at a higher rate than BTEX compounds because it is more water soluble and less retarded

by the solid matrix. However, the impact that biodegradation will have on MTBE plume

movement is less well understood. The greatest need, therefore, is to determine biodegradation

rates for MTBE, other oxygenates, and their by-products under typical soil-groundwater transport

conditions (as outlined in Section 4, Transformation). Field studies are needed to validate

modeled rates of MTBE infiltration during precipitation events to determine the extent that

diffuse sources contribute to groundwater contamination, particularly shallow aquifers used for

private wells. Three dimensional delineation of MTBE plume morphology in a variety of

hydrological settings can be accomplished using push sampling techniques at multiple levels. 

Deep aquifer vulnerability should be examined by applying state-of-the-art fate models for

scenarios that include karst-fractured flow effects and abandoned wells in areas that have high

oxygenate use.

Field studies of the type the USGS Toxics Program (Baehr et al., 1997) is conducting are

needed to quantify the combined impact of precipitation, land use, and storm water management

practices on oxygenate loadings to surface and ground waters, and to develop and test multimedia

exposure models. Stream and lake threat assessments also should be conducted to bound the

potential threats from both diffuse and point sources of oxygenates and their degradation

products.
11

4. TRANSFORMATION

4.1 Background

Contaminants may be transformed through a variety of chemical, physical, or biological

processes. As a result, the mass, toxicity, mobility, volume, or concentration of parent

contaminants in soil and water may be altered. The resulting products of these transformation

processes may in turn pose either a greater or lesser risk. For surface water, potential

transformation processes are biodegradation, photolysis, and hydrolysis. In ground water, the

potential transformation processes include biodegradation and hydrolysis. In surface water,

photolysis is the most important transformation process for ether oxygenates, and biodegradation

is the most important process for alcohols. Basic photolytic and hydrolytic processes are

adequately understood.

Studies on the rates and pathways of environmental MTBE biodegradation are inconclusive,

in part because they have been conducted under different conditions. For example, Suflita and

Mormile (1993) reported no biodegradation of MTBE in lab microcosms under a variety of

aerobic and anaerobic conditions, using sediments from a petroleum-contaminated site. Salanitro

et al. (1994), however, reported complete mineralization of MTBE to CO2 in a mixed culture that

was continuously sparged with oxygen. In another study (Petroleum Environmental Research

Forum, 1993), MTBE was biodegraded when inoculated with a specific bacterial enrichment but

not when inoculated with activated sludge. Limited biodegradation was observed in sediments

under methanogenic conditions (Mormile et al., 1994) and in aerobic microcosms constructed

with aquifer material obtained from the vicinity of the source area of a plume of dissolved BTEX

and MTBE (Borden et al., 1997). Steffan et al. (1997) found that a number of propane-oxidizing

bacteria were able to degrade high concentrations of MTBE, ETBE, and TAME. A series of

degradation products were formed but did not prove to be effective growth substrates. Marked

reduction in the concentrations of MTBE and benzene following termination of active remediation

of fuel contamination was observed at a site in North Carolina (Cho et al., 1997). Products of

MTBE biodegradation have been reported to include TBA (Mormile et al., 1994), but

comprehensive identification of biodegradation products and reaction pathways has not been

undertaken.
12

Results from field studies of the natural biodegradation of MTBE in ground water show that

the processes involved generally take place at very slow rates or with long lag times, and depend

on site-specific geochemical conditions. Schirmer and Barker (1998) found that during the first

16 months following a controlled injection of oxygenated gasoline in a sandy aquifer in Ontario,

there was little evidence for the biodegradation of MTBE. However, when the aquifer was

sampled seven years later, the mass of MTBE had declined by more than an order of magnitude. 

Although the authors hypothesized that natural biodegradation may have been responsible for this

disappearance, they noted the need for confirmatory lines of evidence to support this hypothesis. 

In contrast, Landmeyer et al. (1998) studied an accidental spill in South Carolina over a five year

period and concluded that dispersion and dilution were primarily responsible for decreases in the

concentration of MTBE, with biodegradation playing a very minor role.

Ethanol may pose a different issue with respect to oxyfuel biodegradation. Recent reports

have noted that the presence of ethanol in gasoline may inhibit the biodegradation of BTEX

compounds in groundwater, perhaps because microbes preferentially metabolize the ethanol

(Corseuil and Alvarez, 1996; Corseuil et al., 1996, 1998; Hunt et al., 1997). As a result, these

BTEX plumes may persist longer and become larger.

The above discussion is not a comprehensive summary of studies on the biodegradation of

MTBE and other oxygenates, but it does illustrate the variety of results observed. Most of the

studies were conducted in laboratories, and the results are not necessarily representative of what

might occur in the field. In addition, the observed rates of degradation vary widely, and this

variability will impact the applicability of biodegradation as a remedial option (see Section 10,

Contaminant Removal).

4.2 Needs

Biodegradation rates and pathways for MTBE and other oxygenates need to be measured

experimentally to understand and predict the fate of these compounds in the environment, and to

design cost-effective removal and remediation technologies. The rates of biodegradation will be

key in understanding the fate of oxygenates in the subsurface, in developing in situ and ex situ

contaminant treatments, in implementing natural attenuation protocols, and in conducting aquifer

vulnerability modeling. Identification of by-products and characterization of their environmental

fate are needed to develop a complete picture of the effects of oxygenates on the environment and
13

consequently the risks they may pose. Natural or intrinsic bioremediation is being widely

accepted as either a primary or “polishing” process for groundwater remediation. Rapid

transport, coupled with a slow rate of biodegradation, if confirmed, could limit the application of

this remediation strategy as it relates to MTBE and possibly other oxygenates.

Additional field-scale and complementary laboratory microcosm studies are needed for sites

with a variety of geochemical conditions and contamination scenarios. The geochemical

conditions should reflect those commonly found in contaminated groundwater systems, including

a range of redox and pH conditions, to determine the relative importance of aerobic and anaerobic

processes in MTBE degradation. The contamination scenarios should include regions not only

near the source where concentrations will be the highest but downgradient from the source where

concentrations are likely to be much lower, as well as during vadose zone infiltration by

contaminated storm water. The laboratory studies also should investigate the rates of

biodegradation for high, moderate, and low concentrations of oxygenates, particularly as the

concentration approaches a cleanup standard. Transformation products need to be identified and

quantified so that specific biochemical pathways and degradation product yields under different

conditions can be determined. Along this line, more attention should be given to other

oxygenates that are not yet being used on as wide a scale as MTBE and ethanol but that could

come into more widespread use. The possibility that ethanol or other oxygenates may inhibit the

biodegradation of BTEX should be evaluated.

5. OCCURRENCE

5.1 Background

Although scattered incidents of localized water contamination by MTBE have been reported

since the early 1980s, the first report to suggest that oxygenate contamination of water might be

occurring on a widespread basis came as a result of the USGS National Water Quality

Assessment (NAWQA) program. Designed to assess the status and trends in the quality of

ground and surface water resources of the nation, the NAWQA program began sampling ground

waters for MTBE in 1993 (and added TAME, ETBE, and DIPE in 1996). In an initial analysis of

the NAWQA program’s first 20 study areas or units, MTBE was the second most frequently
14

detected volatile organic compound (VOC) in shallow ground water from selected urban areas

monitored during 1993 and 1994 (Squillace et al., 1996). Of 210 sampled wells and springs,

56 (27%) contained MTBE at a minimum reporting level of 0.2 μg/L. (For comparison, 28%

contained chloroform and 5% contained benzene.) Sixty wells and one spring contained MTBE

and/or BTEX; of these 61 sites, 79% had MTBE alone, and 13% had both MTBE and BTEX. 

Of all the urban wells and springs sampled, 3% had MTBE concentrations exceeding 20 μg/L.

Since the USGS findings, other studies have provided data that supplement the picture of

MTBE occurrence in ground, surface, and drinking water. However, it is difficult to characterize

the overall occurrence of oxygenate contamination because reports vary in their focus, methods,

geographic coverage, and time frames. Also, some monitoring programs are ongoing, with

reports updated continually via the internet. Therefore, this discussion can offer only an

impressionistic treatment of the subject. Although the relative contributions of point and

non-point sources are yet to be determined (see Section 2, Source Characterization), sites of

known or possible UST releases obviously warrant particular attention. For example, Happel

et al. (1998) analyzed data from 236 leaking UST sites in California and found that MTBE was

detected at 78% of these sites. Of the 32,409 known leaking UST sites in California, 13,278 are

known to have contaminated groundwater. Based on their analysis, Happel et al. estimated that

the minimum number of California UST sites with MTBE present was greater than 10,000.

Buscheck et al. (1998) evaluated groundwater plume monitoring data from more than

700 service station sites in four states in different regions of the country. MTBE was detected at

approximately 83% of the sites, with about 43% of all sites having MTBE concentrations greater

than 1,000 μg/L. The highest frequencies of detection occurred at sites of currently operating

stations (n = 466) in Texas and Maryland (96 and 98%), with northern and southern California

intermediate (83 and 84%), and Florida the lowest (76%). Similar but slightly lower rates of

occurrence were found at sites with nonoperating stations (n = 243). Concentrations greater than

1,000 μg/L were found at 55% of the operating sites and 22% of the nonoperating sites. 

The authors suggested that differences in the incidence and levels of MTBE occurrence may have

been due to factors such as hydrogeologic differences, differing histories of MTBE usage, and

UST upgrade efforts in the states considered.

An EPA-supported survey of the 50 states and District of Columbia found that, of the

34 states that acquire MTBE data from leaking UST sites, 27 (79%) indicated that MTBE was
15

present at more than 20% of their sites and 10 (29%) reported MTBE at more than 80% of their

sites (Hitzig et al., 1998). Interestingly, five states reported detecting MTBE (at >20 μg/L) with

non-gasoline petroleum such as diesel fuel, jet fuel, and heating oil. The survey also asked about

contamination of drinking water wells. Of the 49 state programs that responded to the survey,

25 (51%) had received reports of private wells contaminated with MTBE. It was estimated that

the total number of contaminated private wells ranged from 2,256 to 2,663. In addition,

19 (39%) programs had reports of public drinking water wells contaminated with MTBE, with the

estimated total number of such wells ranging from 251 to 422. These totals are presented as

ranges because the survey requested data in ranges (e.g., 1-10, 11-20, etc.) or as highest estimates

(e.g., estimate if greater than 40).

The contamination of drinking water wells also was examined by the USGS in an extension

of the NAWQA study described above (Squillace et al., 1996). Data were collected in 1995 from

additional wells in the same 20 NAWQA study units, combined with previously collected data

from these units, and analyzed for the entire period of 1993-1995 (Zogorski et al., 1998). 

The data were sorted according to whether or not the sampled wells were used for drinking

water. This analysis showed MTBE detections in 12 (14%) of 83 urban wells used for drinking

water and in 19 (2%) of 949 rural wells used for drinking water, with a median concentration of

approximately 0.50 μg/L. Only one of the more than 1,000 samples exceeded the EPA Drinking

Water Advisory of 20-40 μg/L.

The USGS findings for drinking water wells are consistent in certain respects with results

from a recent study in Maine in which 951 household drinking water wells and 793 Public Water

Supplies (PWSs) were sampled for MTBE (Maine Department of Human Services, Bureau of

Health, 1998). At a minimum reporting level of 0.1 μg/L, preliminary results showed MTBE

detections in 150 (15.8%) of the sampled household wells. The incidence of private well samples

exceeding state’s maximum contaminant level of 35 μg/L for MTBE was 1.1%, somewhat higher

than the incidence of such concentrations in the USGS analysis. The Maine report projected that

approximately 1,400-5,200 private wells across the state could be contaminated at levels

exceeding 35 μg/L. For the Maine PWSs, 125 (16%) of the samples had detectable levels of

MTBE, with no samples above the 35 μg/L standard and 48 (6.1%) between 1 μg/L and 35 μg/L.

In another recent study, the American Water Works Service Company (Siddiqui et al.,

1998) collected data from drinking water wells in 16 states. Forty-four (2%) of 2,120 samples
16

from 17 (4%) of 450 wells tested positive for MTBE at a minimum reporting level of 0.2 μg/L,

with the highest concentration reported at 8.0 μg/L. The detections occurred primarily in eastern

states in areas with known UST releases.

Since February 1997, the California Department of Health Services has required public

water suppliers to monitor their drinking water sources (i.e., ground water and surface water) for

MTBE. To date, over 4,566 (39%) of 11,837 drinking water sources in California have been

sampled for MTBE (California Department of Health Services, 1998). Of these, 26 (0.6%)

sources (18 ground water and 8 surface water) had detectable levels of MTBE, including

9 sources with samples exceeding California’s drinking water interim action level of 35 μg/L. 

These data are based on a detection limit of 5 μg/L. If all detections are considered, including

possible false positives below 5 μg/L, 65 sources (1.4%) had detectable levels of MTBE. None

of the surface water samples exceeded 35 μg/L.

Other USGS regional studies are ongoing for New England aquifers (Grady, 1997), aquifers

and surface waters of Long Island, New York and in New Jersey (Stackelberg et al., 1997), and

fractured bedrock aquifers in Pennsylvania (Lindsey et al., 1997). Also, the USGS and EPA

entered into a cooperative agreement to conduct a pilot study (managed under the USGS

National Synthesis Program) in 12 northeastern states to describe the occurrence and distribution

of MTBE and other VOC’s in drinking water sources through a stratified statistical sampling of

recent public water supply system data (both ground water and surface water) and ambient

ground water data (Grady, 1997).

To require monitoring of drinking water for MTBE or other oxygenates, EPA must first

promulgate regulations requiring the collection of the data, with monitoring schedules based on

the size of the public water system. As required by the Safe Drinking Water Act (SDWA),

amended in 1996 (U.S. Code, 1996), EPA published a drinking water Contaminant Candidate List

(CCL) on March 2, 1998 (Federal Register, 1998). The CCL is a list of currently unregulated

contaminants targeted for consideration in priority-setting for the Agency’s drinking water

program, including regulatory determinations, drinking water research, occurrence monitoring,

and guidance development such as health advisories. The 1998 CCL identified MTBE as a

contaminant with specific data gaps in the areas of health effects and occurrence data. These data

gaps must be filled in order for EPA to make a scientifically informed determination as to whether

or not MTBE should be regulated with a health-based National Primary Drinking Water
17

Regulation. The CCL also serves as a source list of chemicals to evaluate for possible inclusion in

the Unregulated Contaminant Monitoring Rule (UCMR), required by the SDWA to be finalized

by August 1999. The proposed UCMR is expected to be published by early 1999 and to include

MTBE. Contaminants included in the forthcoming rule will be subject to required monitoring by

the states. Data collected during implementation of the final UCMR will be stored in the National

Contaminant Occurrence Database (NCOD). The NCOD will provide the basis for identifying

contaminants for future CCLs, supporting the Administrator’s decisions to regulate contaminants

in the future, and to assist in reviewing existing regulations and monitoring requirements every six

years, as required by SDWA.

The Clean Water Act, Section 305(b) (U.S. Code, 1977) requires states and other

participating jurisdictions to submit water quality assessment reports to EPA every two years. 

Based on these reports, EPA prepares the National Water Quality Inventory Report to Congress. 

However, a state may or may not provide data on specific unregulated contaminants such as

MTBE in 305(b) reports, depending on the individual state’s water quality priorities.

The detection and reporting of oxygenate contamination in water presupposes that adequate

analytic methods are available for this purpose. The ether oxygenates can be analyzed with

several standard EPA methods. The most reliable methods use purge-and-trap capillary column

gas chromatography/mass spectrometry (GC/MS) such as EPA Drinking Water Method 524.2

(Eichelberger et al., 1992), EPA Waste Water Method 624 (U.S. Environmental Protection

Agency, 1998b), or EPA Solid Waste (SW-846) Method 8260B (U.S. Environmental Protection

Agency, 1998c). The USGS GC/MS method SH2020 also has been determined to be reliable for

ether oxygenates (Connor et al., 1998). These GC/MS methods provide positive identification of

specific constituents and, as such, they overcome the problem of false identification of coeluting

constituents. Standard EPA methods that use a GC/photoionization detector (PID) (i.e., Drinking

Water Method 502.2, Waste Water Method 602, SW-846 Method 8021) also can be useful, but

because identification with these methods is based on the expected time that a chemical takes to

pass through the capillary column, false positives are possible from coeluting constituents. 

Depending on the purpose of the analysis (e.g., UST site assessment, drinking water supply

monitoring), the problem of false identification can be minimized by first determining if MTBE or

another ether oxygenate is present with a GC/MS method, then performing analyses on additional

samples with a GC/PID method (Happel et al., 1998). Gas chromatography/flame ionization
18

detector (FID) methods can be useful for detection of the alcohols as well as the ether

oxygenates. However, as with PID, FID is subject to misidentification of coeluting compounds,

and because FID is sensitive to all organic compounds, detection of specific compounds can be

more difficult than with other equipment. Despite these problems, a two-dimensional GC/FID

method for water samples with high hydrocarbon content has been developed using a modified

ASTM method D4815 (Galperin, 1998). This method has been approved for use in California. 

Both EPA methods 8260B and the modified ASTM method 4815 are capable of detecting TBA

concurrently with the ether oxygenates, although the detection limit for TBA is significantly

higher than the detection limits for the ether oxygenates—approximately 30 to 40 μg/L for TBA

and less than 1 μg/L for the ethers (Rhodes et al., 1998). However, a direct aqueous injection

GC/MS method (Church et al., 1997) exists for detection of low levels of the ether oxygenates

and TBA.

5.2 Needs

As stated in the Interagency Assessment of Oxygenated Fuels (Interagency Oxygenated

Fuels Assessment Steering Committee, 1997) and affirmed by the NAS/NRC Review Committee

(National Research Council, 1996), oxygenates should be added to existing VOC analyte

schedules and included as routine target analytes for VOCs in drinking water, waste water,

surface water, ground water, and remediation sites. Monitoring should be long term to support

trend analyses of possible changes in water quality and the potential for population exposures. 

However, some discretion should be exercised with respect to including oxygenates that have not

been used or are not expected to be used to any appreciable extent, if by their inclusion the cost of

such monitoring would be significantly increased. Similarly, any decision to monitor for

oxygenate transformation products on a widespread basis should be guided by information on the

occurrence of the respective parent oxygenates and by definitive identification of the respective

transformation products that would be targeted (see Section 4, Transformation). Given the

existence of TBA as a primary oxygenate, as a contaminant of MTBE, and as a degradation

product of MTBE, the inclusion of TBA in ambient ground water quality monitoring programs is

advisable. It also would be useful to monitor for TBA at specific sites where MTBE

contamination is known or suspected to have occurred.
19

The Interagency Assessment of Oxygenated Fuels (Interagency Oxygenated Fuels

Assessment Steering Committee, 1997) recommended that a national database for monitoring

data should be developed cooperatively among relevant governmental and private organizations,

to be administered by a single federal agency. At present, existing “national” databases appear to

be limited in their respective scopes. The EPA Safe Drinking Water Information System

(SDWIS) contains drinking water data from public water supply distribution systems, whereas the

USGS National Water Inventory System database contains ambient water quality data. 

As specified by the SDWA Amendments of 1996, EPA’s Office of Ground Water and Drinking

Water is currently developing the first release version (by August 1999) of the NCOD, which will

expand the existing capabilities of SDWIS. In the longer-term (i.e., 2000 - 2002) the Agency

plans to upgrade the NCOD to include both public water system and ambient water quality data.

Assuming that oxygenates are added to VOC analyte monitoring lists, an effort should be

made after a reasonable period (e.g., 3 to 5 years from now) to analyze these or other databases

for trends in the occurrence of oxygenates in water. These analyses should be linked to exposure

assessment efforts (see Section 6, Exposure) and evaluated for guidance as to whether more

intensive monitoring or other actions are warranted. To the extent possible, monitoring efforts

and database designs should be undertaken in a manner to relate qualitatively and quantitatively to

exposure assessments for human populations and aquatic biota.

The most pressing research need related to analytical methods is to validate existing

methods for the detection of alcohol oxygenates other than TBA, or develop new cost-effective

methods for these alcohols. In addition, development of low cost, simple field methods for ether

oxygenates would be useful. Although field portable GC/PID and GC/FID methods can likely be

adapted for this purpose, supportive research would be helpful for facilitating their widespread

use.

6. EXPOSURE

6.1 Background

Based on limited monitoring and occurrence data (see Section 5), a potential for exposure

of biota and human populations to oxygenates exists. Exposure implies actual contact with a

contaminant, not just the existence or occurrence of the substance in the environment. Exposure
20

characterization requires information on the magnitude and distribution of exposures. Among

many factors that can affect exposure to oxygenate-contaminated water, unpleasant odor and

taste have been reported as particularly notable in the case of MTBE in drinking water

(e.g., Angle, 1991). However, it cannot be assumed that the sensory properties of oxygenates

would prevent human population exposures to such contaminants. Individuals vary greatly in

sensory and subjective reactions, and indeed, anecdotal evidence indicates that some individuals

may have unknowingly consumed drinking water contaminated with MTBE at levels exceeding

35 μg/L (Maine Department of Human Services, Bureau of Health, 1998). Also, young children

could be exposed via infant formula and beverages prepared with oxygenate-contaminated water. 

Even if all human exposures to oxygenates could be averted by water treatment processes,

exposure of biota to contaminated surface or ground water could still occur.

Taste and odor detection thresholds for MTBE have been reported ranging from

24 to 135 μg/L for taste and from 15 to 180 μg/L for odor (Malcolm Pirnie, Incorporated, 1998b;

Dale et al., 1997; Shen et al., 1997; Young et al., 1996; Prah et al., 1994; Vetrano, 1993a,b;

TRC Environmental Corporation, 1993). Limited testing suggests taste and odor thresholds may

be somewhat lower for ETBE and TAME than for MTBE (e.g., Shen et al., 1997; TRC

Environmental Corporation, 1993; Vetrano, 1993a,b). None of the above studies attempted to

characterize a population distribution of threshold responses.

It is important to note that detection and recognition thresholds for taste and odor

sensations are distinct from their hedonic properties, which involve dimensions such as the

(un)pleasantness and intensity of the sensory experience. The detection threshold is typically

defined as the concentration at which a subject can detect a taste or odor difference between a

standard (e.g., “plain” water) and the diluted test substance on a specified percentage (e.g., 50%)

of the trials. The recognition threshold is the concentration at which a subject can recognize or

identify the target substance in the diluent. In one study (Dale et al., 1997), four panelists were

asked to describe the taste and odor of MTBE in odor-free water at concentrations ranging from

2 μg/L to 190 μg/L. At concentrations of 2 to 5 μg/L, the consensus judgment of the panelists

was that the taste of MTBE could be described as “sweet.” At concentrations of 21 to 190 μg/L,

the characterization was either “solvent” or “sweet solvent.” Similar characteristics were

attributed to the odor of MTBE at concentrations of 21 to 190 μg/L. The panelists also were

asked to rate the intensity of the taste and odor, which they considered “objectionable” at a
21

concentration of approximately 50 μg/L for taste and at approximately 90 to 100 μg/L for odor. 

Note that these tests were conducted with nonchlorinated, odor-free water at 25 EC. 

Chlorination would likely raise the thresholds for the taste and odor of MTBE in water, and

higher temperatures (e.g., for showering) would likely lower these thresholds. Also, thresholds

will vary with instruction, training, motivation, age, gender, and other variables that are often not

controlled for or reported.

Hedonic responses, along with considerations of consumer cost, convenience, and other

factors, may figure importantly in the levels of contamination that individuals or communities will

reject or accept (and consequently be exposed to) in their drinking water. Because cognitive

factors, including attitudes that may be shaped by information provided through the social milieu,

can significantly influence sensory perception (Dalton, 1996), populations as well as individuals

may vary considerably in sensitivity to, and tolerance of, odors and tastes, such that a given

concentration of contaminant might be quite acceptable to a large majority of persons in one

group and strongly rejected by an equal proportion in another (cf. Anderson et al., 1995).

Microenvironmental measurements of VOCs such as benzene and trichloroethylene in

relation to household water usage (e.g., Lindstrom et al., 1994; Wilkes et al., 1996; McKone and

Knezovich, 1991) point to the importance of considering multi-media, multi-route personal

exposures. “Drinking water” is used in many ways besides direct ingestion, including food

preparation, dish washing, laundering, and bathing. In particular, showering affords a significant

exposure potential by the inhalation and dermal routes, with variables such as water flow rate and

temperature influencing exposure levels (Giardino and Andelman, 1996). Although

physicochemical and other properties of oxygenates differ from VOCs investigated thus far, the

importance of microenvironmental personal exposures to contaminated household water is

relevant to oxygenates as well.

Aquatic, terrestrial, and marine biota are subject to exposure to acute and/or chronic

releases of fuels and fuel additives. However, very little information exists to characterize

exposure pathways or exposed ecological receptors in relation to oxygenates (Carlsen et al.,

1997).
22

6.2 Needs

Limited empirical information is available either on the overall distribution of exposures to

oxygenates in water for the U.S. population as a whole or on “high-end” exposure scenarios

where oxygenate contamination is already known to occur. One step toward determining the

prevalence and level of potential exposures to oxygenates would be to obtain monitoring data

from public water suppliers (see Section 5, Occurrence). However, establishing large-scale

monitoring programs is probably not the most efficient means for characterizing the potential for

human population exposures to oxygenates. Rather, statistically representative sampling of public

and private water supplies, including wells, may afford a more cost-effective approach. 

By coupling such data with qualitative and quantitative data on water usage and consumption

patterns, it should be possible to model human exposures to specified oxygenates for risk

assessment purposes (cf. Brown, 1997). The USGS NAWQA program may help address part of

this need through a stratified statistical sampling of wells across the United States. Also, the

National Health and Nutrition Examination Survey (NHANES) program may be used to collect

data on population exposures to oxygenates and their metabolites, by sampling blood and drinking

water for MTBE and TBA levels. Although the focus of this document is water contamination,

exposure to oxygenates must ultimately be considered in terms of all relevant pathways and

routes, including inhalation, ingestion, and dermal contact.

With respect to locales where oxygenate contamination of the public water supply has

already been documented, the focus should be on evaluating potential personal exposure scenarios

involving all household uses of oxygenate-contaminated water (e.g., for drinking, food

preparation, cleaning, bathing). Several studies of multi-route VOC exposures through showering

and other uses of tap water (e.g., Weisel and Jo, 1996) provide a substantial foundation for

modeling as well as empirical studies of oxygenate exposure. As a first step, modeling of personal

exposures, building on integrative approaches that incorporate macro- and micro-environmental

pathways and even pharmacokinetic aspects (e.g., Georgopoulos et al., 1997; Piver et al., 1997;

Rao and Ginsberg, 1997) should be undertaken, using sensitivity analyses to identify areas of

needed additional data. Although a substantial database already exists for the pharmacokinetics of

MTBE by inhalation (e.g., Borghoff et al., 1996), additional work is needed to supplement the

limited pharmacokinetic data for the oral and dermal routes. Biomarkers of exposure
23

(e.g., metabolites such as TBA) might warrant investigation if exposures prove to be of sufficient

concern.

More extensive data on odor and taste thresholds and hedonic responses to the various

oxygenates are needed to determine whether or how population exposures may be affected by

sensory variables. The question of what contaminant levels may be acceptable to different

consumer populations is not an exposure assessment issue per se, but more data on thresholds and

hedonic reactions would provide a stronger basis for determining consumer acceptance levels and

for estimating actual usage of (and thus exposure to) oxygenate-contaminated water.

7. AQUATIC TOXICITY

7.1 Background

The aquatic toxicity of oxygenates has been briefly summarized in the Interagency

Assessment of Oxygenated Fuels (Interagency Oxygenated Fuels Assessment Steering

Committee, 1997). Some basic toxicity data exist for MTBE, ETBE, TAME, DIPE, ethanol, and

TBA for selected aquatic species (e.g., Daphnia magna, Pimephales promelas, Carassius

auratus). However, EPA has not established water quality criteria for oxygenates for the

protection of freshwater or marine aquatic life. Currently, testing is underway to evaluate the

acute and chronic toxicity of MTBE to aquatic organisms (Christensen et al., 1998; Mancini et al.,

1998). Based on the results of this work and other existing data (e.g., Huttenen et al., 1997), the

EPA Office of Water expects to have a complete data set available for deriving water quality

criteria for MTBE in early 1999.

7.2 Needs

Current actions should provide an appropriate basis for determining whether additional

effects testing or research is needed.
24

8. HEALTH EFFECTS

8.1 Background

Most of the testing and research on the toxicity of oxygenates has been concerned with the

effects of inhaled MTBE in laboratory animals and human volunteers. Little information exists on

the effects of ingested oxygenates on humans, with the notable exception of the extensive

database on the health effects of ingested ethanol. However, in the absence of any evidence

indicating that human populations are exposed to ethanol-contaminated drinking water, the well

characterized health effects of ingested ethanol need not be considered here. 

A few studies have examined the toxicity of MTBE in laboratory animals via the oral route

of exposure (Belpoggi et al., 1995; Robinson et al., 1990; IIT Research Institute, 1992;

Bio-Research Laboratories Limited, 1990). None of these studies used drinking water as a

medium for administering MTBE to animals; rather, they typically delivered MTBE mixed in olive

oil or corn oil in a bolus dose through a tube into the stomach. This method does not correspond

very well to the way that drinking water is typically consumed by people. Apart from such

methodological problems, other questions have been raised about the use of some of these studies

for risk assessment purposes (cf. National Research Council, 1996; Belpoggi et al., 1998). 

Considerable uncertainty hampers attempts to characterize the health risks related to MTBE in

drinking water, as illustrated by the absence of a quantitative health risk estimation in a recent

Drinking Water Advisory on MTBE (U.S. Environmental Protection Agency, 1997) and the

somewhat divergent conclusions reached by different assessments of the data on MTBE toxicity

(e.g., International Agency for Research on Cancer, 1998; Froines et al., 1998; California

Environmental Protection Agency, 1998; European Centre for Ecotoxicology and Toxicology of

Chemicals, 1997; Interagency Oxygenated Fuels Assessment Steering Committee, 1997).

Oral toxicity data for other ethers are even more limited, although some work on inhaled

vapors of ETBE and TAME is currently being conducted under provisions of a Toxic Substances

Control Act Enforceable Consent Agreement (Federal Register, 1995), and some work has been

published on the kinetics and toxicity of inhaled ETBE (e.g., Hong et al., 1997; Johanson et al.,

1997; Dorman et al., 1997) and TAME (e.g., Daughtrey and Bird, 1995). TBA is of relevance

both as a metabolite of MTBE (Borghoff et al., 1996) and as an oxygenate or oxygenate

by-product. Ingested TBA has been evaluated in rats and mice in a chronic bioassay by the
25

National Toxicology Program (Cirvello et al., 1995). Long-term exposure to TBA in drinking

water produced various toxicologic and carcinogenic effects, including increased incidences of

kidney and thyroid tumors.

8.2 Needs

Given the limitations of information on the oral toxicity of MTBE and the much greater

database on the inhalation toxicity of MTBE, the question arises as to whether more oral toxicity

studies should be initiated, or should inhalation toxicity data be extrapolated to estimate oral

toxicity risk. A significant effort has already been devoted to investigating the kinetic behavior of

MTBE in rodents with the goal of developing a physiologically based pharmacokinetic (PBPK)

model to describe the dosimetry of MTBE and TBA in rats and humans (Borghoff et al., 1996). 

This ongoing work is expected to yield a more refined quantitative PBPK model in the near term. 

In addition, a pharmacokinetic study of human volunteers exposed to MTBE by the inhalation,

oral, and dermal routes is being conducted by the EPA Office of Research and Development. 

As the results of these studies become available, it is anticipated that it will be possible to

accurately predict levels of MTBE and TBA in rodent and human target organs for different

routes and levels of exposure to MTBE. Consequently, it should be feasible to use inhalation

toxicity data from past laboratory animal studies (Bird et al., 1997) to quantitatively estimate oral

toxicity risks of MTBE in humans. Ultimately, the net health risks from multi-pathway exposures

to MTBE (e.g., via refueling and motor vehicle use as well as drinking water) need to be assessed. 

The options of initiating further oral toxicity studies or of using PBPK modeling to

extrapolate from inhalation effects to oral toxicity risk are not mutually exclusive. A study of

subchronic oral exposure to MTBE would provide better data on the potential for toxic effects as

well as help validate a PBPK model for cross-route extrapolation. If such an extrapolation is

unsuccessful, then a new chronic bioassay may be needed to reduce the uncertainties in assessing

human health risks from chronic exposure to MTBE in drinking water.

Questions about the human relevance of carcinogenic effects observed in laboratory rodents

exposed to high concentrations of MTBE also need to be resolved if uncertainties in current

assessments of human cancer risk are to be reduced. In view of the weight necessarily attached to

the cancer bioassays on MTBE, it would be desirable to reexamine and confirm the pathology

data from all of these studies. Alternative assays for carcinogenicity, such as transgenic mice
26

(Tennant et al., 1995) and medaka fish (Boorman et al., 1997) assays, may offer relatively rapid

approaches for collecting additional data that could contribute to a weight-of-evidence

determination as well as insights on the modes of action. Although the latter approaches are

unlikely to provide dose-response information that would enhance quantitative potency estimation

(a critical need), and interpretation of negative results from these assays could be problematic,

they could provide supporting or confirmative evidence of certain tumor types and thus assist in

interpreting the relevance of inhalation effects for drinking water exposure.

The database for TBA may be adequate to characterize the oral toxicity of TBA. Given the

potential for human exposure to TBA either as a metabolite, as an oxygenate itself, or as a natural

biodegradation product of MTBE in ground water, an assessment of the carcinogenic and

noncarcinogenic health risks of TBA should be undertaken.

The best strategy for the other ethers may be to obtain pharmacokinetic data (for some,

work is already underway or anticipated for the inhalation route [U.S. Environmental Protection

Agency, 1998d]) and take such information into account in designing and conducting oral toxicity

testing of these ethers. This strategy is predicated on low usage of ethers other than MTBE. 

If occurrence or exposure data become available and suggest otherwise, the need for more

intensive investigation of the pharmacokinetics and health effects of other ethers may be elevated. 

As for degradation products of oxygenates (other than TBA), more information on the occurrence

and concentrations of these chemicals is needed to guide decision-making about which chemicals

to test.

9. RELEASE PREVENTION

9.1 Background

Although the contribution of point source releases to the problem of environmental

contamination from fuel oxygenates cannot be quantitatively characterized at present, such

releases are clearly a matter of risk management concern. The compatibility of fuel storage and

distribution system components with the fuel they contain has always been an issue for system

component manufacturers, petroleum refiners and distributors, and regulators. Federal

regulations (§280.32, Code of Federal Regulations, 1990) require that UST system components
27

be compatible with the constituents they contain. The changing composition of gasoline,

particularly with the addition of ethers and alcohols, has raised the question of whether all existing

systems are compatible with newer fuels and fuel additives.

Steel tanks and piping are not thought to be significantly corroded by oxygenates (Douthit

and Davis, 1988; Geyer, 1995), but the effects of oxygenates on fiberglass reinforced plastic

(FRP) tanks and piping have been less clear. Although MTBE and other fuel ethers have been

shown not to cause corrosion of FRP (Douthit et al., 1988; Drake et al., 1995), manufacturers

such as Owens-Corning (Bartlow, 1995) have indicated that they do not extend their 30-year

warranties to older (pre-1984) FRP tanks exposed to alcohols, depending on the type and

concentration of the alcohol used. No known published research has examined older tanks

exposed to up to 10% ethanol.

The possibility exists that some UST system components, such as FRP tanks and piping and

flexible piping, may be permeable to MTBE and other oxygenates. Such permeability might

account for cases of MTBE contamination at gasoline stations where no leak could be detected

and no other gasoline constituents were found. However, some doubt exists that the relatively

large molecular weight of MTBE would allow it to pass through FRP (Curran, 1997). The only

known study of FRP permeability to fuel oxygenates evaluated gasoline with 10 percent ethanol

and found no liquid gasoline loss after 31 days (Smith Fiberglass Products Inc., 1996). No known

work has been conducted on FRP permeability to any other oxygenate.

Elastomer seals, used for gaskets and o-rings throughout UST systems and petroleum

pipelines, may have compatibility problems with oxygenated fuels. An American Petroleum

Institute (1994) survey indicated that petroleum pipeline and terminal managers had noticed

significant deterioration of many different types of elastomers associated with fuel oxygenates. 

The study, however, did not discuss the specific types of oxygenates that caused specific

problems, nor did it discuss the concentrations of the oxygenates. Many of the problems listed

were likely caused by “neat” (pure) solutions of the oxygenates, but the study raises the concern

that more dilute solutions could cause problems as well.

Another study (Alexander et al., 1994) tested six elastomers in various concentrations of

MTBE, ETBE, TAME, ethanol, and methanol. The authors found that although three of the seals

were not able to withstand neat MTBE, all of the seals were acceptable for use in solutions of all

five oxygenates when concentrations were less than 20% (immersed for 168 hours at 23 oC). 
28

Hotaling (1995) tested 15 elastomers at 46 oC for 6 months and found significant deterioration of

three types of elastomers when exposed to concentrations of only 5% MTBE in gasoline. As a

result, Hotaling found that these seals may be “... unsuitable for even low percentages of MTBE.” 

In actual use, however, EPA is not aware of any reports of UST system elastomers failing and

causing a release because of exposure to gasoline containing oxygenates.

In addition to liquid-phase oxygenates, compatibility with vapor phase oxygenates also

should be considered. Because the vapor pressure of MTBE is much higher than many other

gasoline constituents, gasoline vapors should theoretically have much higher concentrations of

MTBE than are found in the liquid phase (Davidson, 1998). These vapors would occur in the

headspace of tanks and vapor recovery systems. In addition, liquid-phase MTBE-enriched

condensate could form inside these vapor recovery systems. Hotaling (1995) tested elastomers

exposed to MTBE vapors and found significant deterioration to some elastomers throughout the

concentration ranges tested (5 to 100%).

Dispenser sumps, used to catch small amounts of fuel below gasoline dispensers, are

typically made of high density polyethylene. Although these sumps should be checked

periodically to remove any fuel, it is possible that some measurable quantities of gasoline and

oxygenates could be released via the sumps. Another potential concern is tank liners. These are

plastic tanks within tanks, typically used inside steel tanks that may have started to corrode, and

are used to avoid replacing the original tank. Certain liner materials may not be compatible with

oxygenated fuels (Meli, 1996).

Some information suggests that leak detection systems may not be mitigating UST releases

as much as might be desired. In a survey of UST leak cases in California (Farahnak and Drewry,

1997), 263 (84%) of 313 cases were discovered in the course of tank closure activities; 15 (<5%)

of the cases were identified through leak detection methods. For 132 cases with available

monitoring data, the average lag between the date of last monitoring and discovery of a leak was

29 months. No information was provided regarding the presence of oxygenates in the survey. 

Although the survey did not resolve whether problems were due to the systems, misuse or a lack

of use of them, or a combination of these factors, the report highlights the importance of leak

detection issues, which in turn are clearly relevant to addressing oxygenated fuel releases.
29

9.2 Needs

The issue of materials compatibility with oxygenated fuels may prove to be quite

manageable. However, a number of unanswered questions need to be resolved to ensure that

releases do not and will not occur. It is important to characterize fully the effects of ethers and

alcohols on elastomers, FRP, and other components of pipelines and tanks, particularly after

several years of aging. The potential for leakage is unknown for older (pre-1984) FRP tanks that

may be exposed to high (e.g., 10%) concentrations of ethanol. Also, the possible permeability of

MTBE through FRP tanks and piping or flexible piping cannot be ruled out with existing data. 

Additional research is needed to resolve contradictory findings on the compatibility of elastomer

seals with MTBE. Vapor recovery systems need to be examined more closely in terms of

compatibility with concentrated MTBE vapor. Dispenser sumps need to be evaluated to

determine if they are a potentially significant source of releases. Independent research is needed

on the compatibility of currently marketed tank liners with ethanol.

Although newer technologies and regulations are intended to reduce the problem of leaking

UST systems for conventional fuels, the different chemical properties of the various oxygenated

fuels raise questions not only about the compatibility of existing systems but also about leak

detection methodologies. Even though the differences in the physicochemical properties of

oxygenated and non-oxygenated fuels may be small, modest research efforts may be required to

reevaluate and confirm the performance and accuracy of in-tank and external leak detection and

monitoring technologies.

Based upon the results of the above studies, new and improved approaches and technologies

could be developed to repair or replace problem areas and to prevent future problems through the

use of more advanced materials and design concepts.

10. CONTAMINANT REMOVAL

10.1 Background

Various methods are available for removing contaminants from soils, ground water, waste

water, and drinking water. Many of these techniques are potentially applicable to contamination

from oxygenates. However, very limited information exists on the technical feasibility and costs
30

of implementing them for oxygenate removal under field-scale operating conditions. 

The following background discussion is not meant to differentiate these processes in their

applications, but rather to address their general efficiency for soils or waters contaminated with

MTBE or other oxygenates. The discussion also notes those technologies that may be

appropriate for in situ subsurface remediation, those that may be more applicable to above ground

treatment of contaminated ground water, and those that may be more suitable for drinking water

treatment at the wellhead or in a drinking water treatment plant.

Water treatment to remove MTBE and other oxygenates will frequently be conducted as

part of an overall treatment process to remove other contaminants such as benzene. 

Consequently, it is worthwhile to ask if an ongoing treatment process also will be effective for

oxygenate removal. However, because oxygenates have different physical and chemical

properties, a technology suitable for one oxygenate may not be suitable for another.

Subsurface treatment methods are often classified as those that transform, immobilize, or fix

the contaminants in situ, and those that extract the contaminant from the subsurface for ex situ

treatment on the surface. Both types are potentially applicable to MTBE and other oxygenates. 

In situ biological treatment is known to be effective for the BTEX component of fuels, but its

effectiveness for oxygenates is subject to debate. The feasibility of an in situ bioremediation

process depends on many factors, including the biodegradation rate, the redox conditions, and the

presence of other contaminants. Information is very limited on the field application of in situ

bioremediation to oxygenates either as part of an active treatment process or for natural

attenuation.

Soil vapor extraction (SVE) is commonly used to remove gasoline contaminants from the

unsaturated zone at spill sites. Based on its high vapor pressure and low affinity for organic

carbon in soil, MTBE would be expected to be readily removed from soil by vapor extraction. 

A computer model, VENT2D, has been used to simulate this process for a gasoline-MTBE

mixture (Conrad and Deever, 1995). In this simulation, MTBE showed the highest rate of mass

loss of five gasoline components, as would be predicted based on their relative vapor pressures. 

Hence, MTBE and other ethers with high vapor pressures are not expected to be problematic for

this technology. Grady and Johnson (1995) empirically demonstrated that SVE was successful in

recovering MTBE, and as expected, the recovery of MTBE was greater than the recoveries for

BTEX compounds.
31

Low-temperature thermal desorption (LTTD) is an ex situ soil treatment technology that

uses temperatures below ignition levels to separate volatile contaminants from soil. Due to the

high vapor pressure of MTBE, LTTD should be very effective in removing MTBE from soil. 

However, because MTBE separates from gasoline and dissolves quickly in water, both SVE and

LTTD must be used soon after a release; otherwise most of the MTBE may have already moved

from the soil into the ground water.

Air sparging involves the injection of air below the water table. The mechanisms for

removal are stripping and potentially oxygen-enhanced biodegradation. Bass (1996) found that

air sparging removed MTBE from ground water, with down-gradient wells showing 99% removal

of MTBE. Levels continued to decline for 13 months after the air sparging unit was shut off,

presumably due to aerobic degradation. Similar results also were reported by Cho et al. (1997).

Because MTBE does not adsorb well to soil and is highly soluble in water, “pump and treat”

technology (i.e., pumping contaminated ground water and treating it above ground) may be

effective in conjunction with certain above-ground biological or physical/chemical

contaminant-removal processes. Conditions such as the presence of complex hydrogeology that

create “dead” zones that are isolated from zones of high hydraulic conductivity will reduce the

effectiveness of pump and treat for MTBE, despite its favorable chemical and physical

characteristics.

Studies have indicated that MTBE can biodegrade in ex situ biological treatment systems

under aerobic and anaerobic conditions (see Section 4, Transformation). Once the conditions for

biodegradation of oxygenates are fully defined, field work can be completed to determine the

practicality of ex situ biological treatment for oxygenates removal.

Granular activated carbon (GAC) adsorption is a frequently used treatment process for

organic contaminants. However, because of its limited adsorption capacity for MTBE, GAC is

generally not cost effective for removing MTBE (Speth and Miltner, 1990). Therefore, it is not

expected that adsorption would be generally used for removing MTBE on a large scale. This is

especially true at high influent concentrations that would limit the time that a GAC column could

be effective. For public water supplies, field studies have shown that carbon adsorption is not

cost effective for MTBE removal unless the concentrations are very low (McKinnon and Dyksen,

1984). For example, even with an influent concentration of 30 μg/L, the carbon beds need to be

regenerated frequently. Other ether oxygenates have slightly lower solubilities than MTBE and
32

thus would be more effectively adsorbed. However, alcohol oxygenates such as ethanol and TBA

are infinitely soluble, and thus adsorption would be ineffective for these compounds. Carbon

adsorption may be useful as a polishing step to air stripping.

Malley et al. (1993) have shown that MTBE adsorbs more strongly to synthetic adsorbents

than to GAC. Because the capital cost of the synthetic adsorbents was much higher than that of

GAC, the authors concluded that synthetic adsorbent removal of MTBE was not economically

feasible. However, synthetic adsorbents could be economically feasible for oxygenate removal if

an inexpensive in situ regeneration process such as steam could be used (Malley et al., 1993).

For volatile organic compounds, air stripping is a cost effective alternative. However, the

Henry’s Law constant for MTBE is low (see Appendix 1), indicating a relatively low efficiency

for air stripping. Air stripping at a very high air-to-water ratio (e.g., 200:1) has been found

effective in removing 93 to 99% of MTBE from ground water (McKinnon and Dyksen, 1984;

American Petroleum Institute, 1990), but at air-to-water ratios of 44:1, 75:1, and 125:1 the

percentage of MTBE removed was 44, 51, and 61%, respectively (McKinnon and Dyksen, 1984). 

By comparison, an effective air-to-water ratio for benzene is typically near 50:1. High air-towater ratios can lead to severe operating problems such as scaling and freezing during cold

weather operations. McKinnon and Dyksen (1984) found that the cost of air stripping treatment

was approximately 55% of that for carbon treatment. However, the off gas of the air stripping

unit was not treated. Treating the off-gas stream would approximately double the cost of the air

stripping system. Air stripping followed by GAC adsorption was found to be very effective for

MTBE removal in this study, as also was found by Truong and Parmele (1992). Other

oxygenates such as ETBE, TAME, and DIPE have higher Henry’s Law constants than MTBE

(approximately 3 to 20 times higher), indicating that air stripping would be at least slightly more

effective for them. For example, in the study by McKinnon and Dyksen (1984) the percentage

removal of DIPE at an air-to-water ratio of 200:1 was greater than 99% (McKinnon and Dyksen,

1984). However, alcohol oxygenates have very low Henry’s Law constants, indicating that air

stripping would not be effective for these compounds.

Yeh (1992) found that hydrogen peroxide in the presence of iron (Fenton’s reaction)

degraded ETBE and MTBE. This was later confirmed under laboratory conditions by Chen et al.

(1998) and other researchers. Therefore, the hydroxyl radicals produced by Fenton’s reaction

appear to be an effective treatment agent. Ozone/ultraviolet (UV), ozone/peroxide, UV/peroxide,
33

and ozone/sonication also have potential as treatment technologies for oxygenate destruction. 

The American Petroleum Institute (1991) reported that advanced oxidation is more cost effective

than other zero emission technologies such as steam stripping, ex situ biological oxidation, and air

stripping with off-gas control. Malcolm Pirnie Incorporated (1997) also concluded that advanced

oxidation is more cost-effective than carbon adsorption or air stripping with off-gas control. 

Malley et al. (1993) reported over 95% removal of MTBE using UV/peroxide. Oxidation

byproducts included methanol, formaldehyde, and 1,1-dimethylethyl formate. Using UV/peroxide

with a highly contaminated ground water produced less removal (up to 83%) presumably due to

the effects of alkalinity scavenging of hydroxyl radicals and competition from other organics

(Malley et al., 1993). The American Petroleum Institute (1997) reported up to 98% removal of

MTBE in a UV/peroxide reactor under various conditions. Diisopropyl ether had higher removal

rates than MTBE, indicating that DIPE is more easily destroyed by hydroxyl radicals than MTBE. 

Compared to benzene, MTBE is only moderately reactive, with reaction rate constants seven

times lower than that for benzene. Kang and Hoffmann (1998) found that the combination of

ozonation and sonication can effectively degrade MTBE into tert-butyl formate, TBA, methyl

acetate, and acetone. Leitner et al. (1994) found that ozone/hydrogen peroxide treatment could

eliminate ETBE and MTBE, with ETBE more reactive than MTBE. The ozonation byproducts

were tertiary butyl formate, tertiary butyl acetate, and TBA.

Because advanced oxidation systems increase the biodegradability of the organic matter in

the water, biofiltration may be recommended following oxidation to control for biogrowth in

drinking-water distribution systems. The result could be an effective two-stage process: abiotic

oxidation followed by aerobic biodegradation of the oxygenates.

10.2 Needs

Numerous areas of contaminant-removal research are needed for MTBE and other

oxygenates. Because remediation and drinking water sites often differ with regard to contaminant

concentration, clean-up goals, secondary-effect issues such as biological regrowth and corrosion,

and public acceptability, this section is separated into remediation and drinking-water subsections. 

For both subsections, comparative cost estimates for all technologies are needed. 

The research needs for the removal of oxygenates from waste water are not discussed

separately here. Although waste waters typically contain higher levels of background organics
34

and inorganics that might interfere with the removal of oxygenates, it is not clear that oxygenate

contamination of waste water is a widespread occurrence. To the extent that biological

treatments (e.g., activated sludge, trickling filters) that are commonly practiced for wastewater

streams may be effective in removing oxygenates by virtue of the biodegradation and stripping

mechanisms within these technologies, many of the research needs discussed below will be

pertinent to the removal of oxygenates from waste water. This is especially true of biological

degradation, extensively covered in Section 4 (Transformation).

10.2.1 Remediation Needs

Remediation research is needed for both in situ remediation and ex situ cleanup of extracted

ground water. This research should build on and expand earlier and ongoing work on remediation

of ground water contaminated by other organic compounds. Research is likely to be most

productive if it focuses initially on evaluating the applicability of known remediation technologies

and adapting them to remediation of MTBE and other oxygenates. Cost as well as technical

feasibility should be examined.

There is a pressing need for data on biodegradation (see Section 4, Transformation). 

Optimal conditions for biodegradation processes for in situ and ex situ contaminant removal need

to be determined. This information is needed both to develop enhanced bioremediation

technologies and to better understand the applicability of natural attenuation and risk based

corrective action at UST sites with oxygenate contamination. A particular focus should be on the

introduction of oxygen and nutrients for in situ plume treatment and the potential for abiotic

oxidation and aerobic biodegradation in porous-reactor barriers. Data are needed from field

research and supporting laboratory studies under a variety of conditions, including different 

geochemical conditions, presence of other contaminants, and oxygenate concentrations. 

Information gathered from research regarding optimal biological conditions for oxygenate

removal may lead to cost-effective remediation processes. Research on in situ abiotic oxidation is

a lower priority.

Extraction processes, including pump and treat, SVE, LTTD, in-well stripping, dual-phase

extraction, and air sparging, need to be further evaluated. Specifically, the optimal operating

conditions, effectiveness, and costs of these processes should be investigated for MTBE and other

oxygenates. Also, off-gas control for SVE, air sparging, in-well extraction, and LTTD need to be
35

addressed when appropriate. Finally, the effect of temperature on Henry’s Law constants for the

entire class of oxygenates should be studied.

There is a particular need for research to develop and evaluate both biotic and abiotic

surface treatment systems for extracted ground water. Air stripping is known to work, but many

locations may require off-gas treatment. Research is needed to determine the effectiveness and

cost of off-gas control. Promising research on bioreactors should be continued. For ex situ

abiotic oxidation, Fenton’s reagent, ozone/UV, ozone/peroxide, UV/peroxide, and

ozone/sonication need to be further evaluated in terms of efficiency and cost under a variety of

operating conditions. By-products of oxygenate degradation should be identified under different

conditions. By-product destruction also may need to be evaluated. These oxidative processes

should be optimized so that a site demonstration can be conducted to determine their cost

effectiveness. GAC is not likely to be cost effective as an ex situ treatment process for MTBE in

water but may have applicability to situations with low flow and low concentrations.

Sorbents such as vermiculite, straw, and peat have been proposed for oxygenate removal. 

Although their low cost may offset their low adsorption capacities, this is a low priority research

area and should be limited to gathering and evaluating existing information at this time.

10.2.2 Drinking-Water Treatment Needs

Drinking-water treatment research needs to focus on low concentrations of contaminants

typically found in source waters. Consideration should be given to the scale of water treatment;

from large drinking water plants that treat hundreds of millions of liters a day to point-of-use

systems that treat liters per day. Two technologies that should be investigated first include air

stripping and hydroxyl-radical processes. For air-stripping, a matrix of the effectiveness and cost

needs to be completed for various conditions (e.g., with and without off-gas control), which

would allow more direct comparison to other treatment technologies. Also, configurations other

than packed-tower aerators should be evaluated. Finally, the effect of temperature on Henry’s

Law constants for the entire class of oxygenates needs to be thoroughly studied so as to aid in the

design and evaluation of heated air stripping and steam stripping systems.

For abiotic oxidation processes, a hydroxyl radical treatment, Fenton’s reagent, has been

shown to be effective for MTBE. Because of secondary effects, it is unlikely that Fenton’s

reagent would be used in a drinking water facility. However, other hydroxyl radical processes
36

that utilities have experience with, such as ozone/peroxide, ozone/UV, and peroxide/UV, need to

be more extensively evaluated. Also, the applicability of the ozone/sonication process for

drinking water treatment needs to be evaluated, including evaluation of UV lamp technologies. 

Oxidation byproducts, including bromate, should be identified and quantified under different

conditions and byproduct destruction also may need to be evaluated. These oxidative processes

need to be optimized so that a site demonstration can be conducted to determine their relative

cost effectiveness. 

Also, as previously mentioned, oxidation processes have been shown to increase the

biodegradability of natural organics in water. Therefore, biofilters may be used in drinking water

facilities to control distribution-system regrowth. The removal of oxygenates and oxygenate

degradates or byproducts in these biofilters should be studied. Limited data exist for

biodegradation under drinking-water conditions, but the increase in biodegradability of natural

organics due to hydroxyl-radical treatment potentially holds promise for the removal of

oxygenates and their degradates as a secondary substrate, even at low concentrations. Drinking

water biodegradation work must concentrate on removing low levels of oxygenates.

Other biofiltration processes that utilize the addition of primary substrates should not be

conducted under the auspices of drinking water treatment research. Primary substrates added to

drinking water treatment streams are potentially problematic for several reasons: the primary

substrate could contribute to deleterious human health effects; the primary substrate or its

degradation byproducts might serve as disinfection byproduct precursor material; biogrowth

might occur in the distribution system; and public dissatisfaction might result for these and other

reasons.

Other drinking-water contaminant removal processes that need to be evaluated include

GAC, carbonaceous adsorbents, and new bioreactor membrane technologies. For GAC, work

needs to be completed in developing a matrix of the effectiveness and cost under various

conditions. Because of its expected poor removal of oxygenates, GAC should be evaluated as a

polishing step for air stripping technologies or as a biologically-active filter. Desorption from

GAC also should be studied.

Synthetic carbonaceous adsorbents are very effective in removing many types of organic

compounds from water. In general, steam is very effective for reversing adsorption processes for
37

weakly adsorbing contaminants such as MTBE. Therefore, a study of an automated system that

would adsorb oxygenates then desorb (regenerate) under steam conditions should be initiated.

An automated reverse osmosis system may be applicable for small utilities (under

500,000 gal/day). However, the potential for success for reverse osmosis is limited due to the

low molecular weights (32 to 102 Daltons) of most oxygenates, and thus only a quick, low-cost

evaluation of this process is warranted. Other membrane devices such as carbon-fiber bioreactor

membranes may be more effective; however, preliminary information is needed before extensive

research is conducted.

11. CONCLUSIONS

The following priorities emerge from the foregoing discussion. No attempt is made to rank

these needs relative to each other because they are all critical and are independent of each other in

certain respects. For example, even though more information on biodegradation would assist in

the development of contaminant removal methods, it does not follow that needed work on

contaminant removal methods should be deferred to biodegradation studies. It is reasonable to

expect that efforts can proceed concurrently in each of the areas identified here. It is also

recognized that different organizations may rank priorities differently, depending on their mission,

mandates, programmatic objectives, funding constraints, and other factors. For this reason,

priority ranking of the following needs may vary among organizations, but all of them are valid

and important. Therefore, each of the following needs should be given priority consideration.

C Determination of the relative contributions of point and non-point sources of oxygenate fluxes

to surface and ground waters.

C Determination of oxygenate biodegradation rates and pathways under representative

geochemical conditions, and identification of degradation by-products and their environmental

fate.

C Inclusion of oxygenate analytes and principal suspected transformation products wherever VOC

monitoring of water is routinely performed.

C Statistically representative sampling of public and private water supplies and modeling of

multi-media, multi-pathway personal exposures for estimating population distributions of
38

exposures; modeling and empirical studies of “high-end” microenvironmental exposure

scenarios.

C Completion of PBPK modeling and cancer mechanistic studies to enhance confidence in

extrapolating from laboratory animal inhalation toxicity data as a basis for estimating oral

toxicity risk of MTBE for humans; subchronic oral toxicity study of MTBE in drinking water.

C More extensive evaluation of oxygenate effects on materials used in tanks and pipelines,

especially after aging over a period of years.

C Evaluation of the relative cost-effectiveness of candidate technologies for removing oxygenate

contaminants from water under various conditions, with iterative efforts to optimize the most

promising technologies, develop new innovative approaches, and evaluate the comparative cost

effectiveness of available technologies. 

C Updating of risk characterizations as results of the above work become available.

Efforts to address the issues identified in this document have been underway for some time,

and new efforts are continually being initiated. Consequently, it is very difficult to describe the

current state of the science in an accurate, up-to-date manner. Appendix 2 contains a listing of

current projects related to oxygenates in water. The descriptions of projects are not adequate to

convey the extent of work being undertaken; the intent is to provide an impression of the scope of

studies underway and information to assist readers if they wish to obtain more details about any

particular project.

The purpose of conducting the work identified in this document is to provide a better basis

for characterizing the potential health and environmental risks of oxygenates and for informing

risk management and policy decision making. Risk assessment and risk management efforts

directed at oxygenates in water have been occurring and will likely continue. If the environment

and public health are to be protected effectively and efficiently, however, adequate scientific

information and technical data are essential.
39

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oxygenates methyl tert-butyl ether, ethyl tert-butyl ether, and tert-amyl methyl ether by propane-oxidizing

bacteria. Appl. Environ. Microbiol. 63: 4216-4222.

Suflita, J. M.; Mormile, M. R. (1993) Anaerobic biodegradation of known and potential gasoline oxygenates in the

terrestrial subsurface. Environ. Sci. Technol. 27: 976-978.

TRC Environmental Corporation. (1993) Odor threshold studies performed with gasoline and gasoline combined

with MTBE, ETBE and TAME. Washington, DC: American Petroleum Institute; API publication no. 4592.

Tennant, R. W.; French, J. E.; Spalding, J. W. (1995) Identifying chemical carcinogens and assessing potential

risk in short-term bioassays using transgenic mouse models. Environ. Health Perspect. 103: 942-950.

Truong, K. N.; Parmele, C. S. (1992) Cost-effective alternative treatment technologies for reducing the

concentrations of methyl tertiary butyl ether and methanol in groundwater. In: Calabrese, E. J.; Kostecki,

P. T., eds. Hydrocarbon contaminated soils and groundwater: v. 2. Boca Raton, Fl: Lewis Publishers;

pp. 461-486.

U. S. Code. (1977) Clean Water Act. U. S. C. 33: §305(b).

U.S. Code. (1990) Clean Air Act, §211, regulation of fuels: (k) reformulated gasoline for conventional vehicles;

(m) oxygenated fuels. U. S. C. 42: §7545.

U.S. Code. (1996) Safe Drinking Water Act, as amended by PL 104-208, September 30. U. S. C. 42: §300f et seq.

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47

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chromatography/mass spectrometry (GC/MS). Washington, DC: Office of Solid Waste. Available online at:

www.epa.gov/epaoswer/hazwaste/test/8xxx.htm.

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from Margo T. Oge, Director, Office of Mobile Sources to Carol Henry, Director, Health and Environmental

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TRC Environmental Corporation; project no. 13442-M31.

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additives methyl tert-butyl ether and tert-butyl alcohol over the temperature range 240-440 K. Environ. Sci.

Technol. 22: 842-844.

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18.

Wyborny, L., II. (1998) Methyl tertiary butyl ether (MTBE) emissions from passenger cars [draft technical report].

Ann Arbor, MI: U.S. Environmental Protection Agency, Office of Mobile Sources.

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Polytechnic Institute.
48

Young, W. F.; Horth, H.; Crane, R.; Ogden, T.; Arnott, M. (1996) Taste and odour threshold concentrations of

potential potable water contaminants. Water Res. 30: 331-340.

Zogorski, J. S.; Delzer, G. C.; Bender, D. A.; Squillace, P. J.; Lopes, T. J.; Baehr, A. L.; Stackelberg, P. E.;

Landmeyer, J. E.; Boughton, C. J.; Lico, M. S.; Pankow, J. F.; Johnson, R. L.; Thomson, N. R. (1998)

MTBE: summary of findings and research by the U.S. Geological Survey. In: Proceedings of the 1998

annual conference of the American Water Works Association [in press].
49

APPENDIX 1

CHEMICAL PROPERTIES OF SELECTED OXYGENATES

Chemical Name

Methyl Tertiary

Butyl Ether

Ethyl Tertiary

Butyl Ether

Tertiary Amyl

Methyl Ether

Diisopropyl

Ether

CAS Registry No. 1634-04-4 637-92-3 994-05-8 108-20-3

Synonyms MTBE; 2-methyl,

2-methoxy propane;

tert-butyl methyl

ether; methyl tert

butyl ether;

methyl-tert-butyl

ether

ETBE; tert-butyl

ethyl ether; propane,

2-ethoxy-2methyl;

1, 1-dimethyl ethyl

ether

TAME; 2-methoxy-2

methylbutane; methyl

tert-pentyl ether;

1,1-dimethylpropyl

methyl ether; methyl

tert-amyl ether

DIPE; 2'2-

oxybispropane;

2-isopropoxypropane

Molecular

Weight (g/mol)

88.15 102.18 102.18 102.18

Molecular

Formula

C5H12O C6H14O C6H14O C6H14O

Structural

Formula

CH3OC(CH3)3(CH3)3COCH2CH3 CH3CH2C(CH3)2OCH3(CH3)2CHOCH

(CH3)2

Boiling Point

(at 760 mm Hg)

55.2 EC 72.2 EC 86.3 EC 68.2 EC

Vapor Pressure

(mm Hg at

20 EC)

240 130 75 159

Vapor Density

(air = 1)

3.1 3.6 3.6 3.6

Density

(g/ml at 20 EC)

0.74 0.74 0.77 0.73

Solubility

(g/100 g water)

4.8 1.2 1.2 0.2

Henry’s Law

Constant

 (Atm-m3)/

 (g-mole)

5.28E-4 to 3E-3 2.64E-3 1.95E-3 4.77E-3

 Dimensionless 2.2E-2 to 1.2E-1 0.11 0.081 0.199

Log Koc 0.55 to 0.91 NA NA 1.13

Log Kow 0.94 to 1.30 NA NA 1.52
50

CHEMICAL PROPERTIES OF SELECTED OXYGENATES (cont’d)

Chemical Name

Tertiary Amyl Ethyl

Ether Dimethyl Ether Tertiary Butanol Ethanol

CAS Registry No. 919-94-8 115-10-6 75-65-0 64-17-5

Synonyms TAEE; ethyl tert-amyl

ether; butane,

2-ethoxy-2-methyl

DME; methane,

oxybis

TBA; tertiary butyl

alcohol; 2-propanol,

2-methyl

ethanol;

ethyl alcohol

Molecular

Weight (g/mol)

116.20 46.07 74.12 46.07

Molecular

Formula

C7H16O C2H6O C4H10O C2H6O

Structural 

Formula

CH3CH2C(CH3)2OCH2C

H3

CH3OCH3(CH3)3COH CH3CH2OH

Boiling Point

(at 760 mm Hg)

102 EC !24.8 EC 82.4 EC 78.5 EC

Vapor Pressure

(mm Hg at 20 EC)

NA 758 to 5086*41 44

Vapor Density

(air = 1)

4.0 1.6 2.6 1.6

Density

(g/mL at 20 EC)

0.75 0.66 0.79 0.79

Solubility 

(g/100 g water)

NA 4.7 to 35.3 miscible miscible

Henry’s Law

Constant

 (Atm-m3)/

 (g-mole)

NA 4.89E-4 to 9.97E-4 1.21E-5 6.91E-6

 Dimensionless NA 2.03E-2 to 4.15E-2 5.03E-4 2.83E-4

Log Koc NA -0.29 1.57 -0.14

Log Kow NA 0.10 0.35 -0.32

*At 25EC
51

APPENDIX 2

CURRENT PROJECTS RELATED TO

OXYGENATES IN WATER

This list of projects and activities is organized alphabetically according to the organizations

conducting and/or sponsoring the work. Contact persons are identified parenthetically for

obtaining further details, followed by a short title, brief description, and status of the project. 

After each item, topic identifiers are included for cross referencing to areas of needed work

identified in the base document. This list was completed in December 1998 with the intention of

being as complete and accurate as possible. However, given the breadth and dynamic nature of

this area of work, some omissions and errors may have occurred.

Alpine Environmental (James Davidson)

MTBE Remediation; An Evaluation of Technologies, Field Experience, and Case Studies.

Review and analysis of remediation technologies applicable for MTBE; discusses both theory

and actual case studies [American Petroleum Institute report, in press].

Contaminant Removal; Assessment

American Petroleum Institute (H. Hopkins)

MTBE Site Characterization Technical Bulletin.

Describes approaches for characterizing and monitoring subsurface MTBE sources and plumes,

highlighting differences between MTBE and BTEX [expected completion second quarter 1999].

Source Characterization; Transport; Transformation

Association of California Water Agencies; Western States Petroleum Association;

Oxygenated Fuels Association; California Environmental Protection Agency; U.S.

Environmental Protection Agency (Krista Clark, ACWA; Dave Smith, ARCO)

MTBE Treatability Research Partnership.

Joint research program to evaluate existing and emerging treatment technologies to remove

MTBE from public drinking water supplies [report expected by mid-1999].

Contaminant Removal

Chemical Industry Institute of Toxicology; Oxygenated Fuels Association (Susan Borghoff,

CIIT; John Kneiss, OFA)

MTBE Cancer Mechanisms.

Study of role of alpha-2u-globulin in MTBE-induced kidney tumors in male rats [report expected

late 1998].

Health Effects
52

Environmental and Occupational Health Sciences Institute; ARCO Chemical; State of New

Jersey (Paul Lioy, Nancy Fiedler, EOHSI)

Inhalation Chamber Study of MTBE in Humans.

Inhalation exposure to MTBE in gasoline evaluated in controls and in subjects self-described as

sensitive to MTBE; although only inhalation route used, results might be relevant to other routes

[expected completion early 1999].

Health Effects

European Union; Finnish Environmental Institute; Finnish National Product Control

Agency for Welfare and Health (Riitta Leinonen, FEI)

MTBE Risk Assessment.

Assessment of environmental and health risks of MTBE under Commission directive 93/67/EEC

[publication expected 1999].

Assessment

International Agency for Research on Cancer (Julian Wilbourne)

MTBE Monograph.

Evaluation of carcinogenic risks of MTBE to humans [workgroup review October 1998;

publication 1999].

Assessment

Lawrence Livermore National Laboratory; American Petroleum Institute (Anne Happel,

LLNL; Bruce Bauman, API)

Study of MTBE and BTEX Plumes at California/UST Release Sites.

Characterize trends in the attenuation, magnitude of impact, and mobility of MTBE plumes in

groundwater as compared to BTEX and evaluate the effectiveness of tank upgrades in preventing

MTBE impacts [expected completion first quarter 2000].

Transport; Transformation; Release Prevention

Lovelace Respiratory Research Institute; Health Effects Institute (Janet Benson, LRRI;

Maria Costantini, HEI)

Toxicokinetics of MTBE With and Without Gasoline.

Quantify uptake, metabolism, and excretion of C-14 labeled MTBE alone and in gasoline over a

range of concentrations and repeated inhalation exposures in rats [ongoing through 1998].

Health Effects

Metcalf & Eddy; American Petroleum Institute (R. Claff, API)

Characterization of Service Station Stormwater Runoff.

Contractor to develop sampling plan to collect stormwater samples at several retail marketing

facilities; samples to be analyzed for BTEX, MTBE, heavy metals, and a variety of other

parameters [draft report expected late 1998].

Source Characterization; Occurrence
53

Metropolitan Water District of Southern California (Marshall Davis)

Surface Water Sampling.

Sampling for MTBE and other gasoline components in drinking water reservoirs used for

recreational boating [ongoing through 1998].

Occurrence; Source Characterization

Metropolitan Water District of Southern California; U.S. Geological Survey; American

Water Works Association Research Foundation (Bart Koch, MWDSC; Kenan Ozekin,

AWWARF)

Sampling of Public Drinking Water Supplies.

Nation-wide sampling of source waters for community water systems to characterize MTBE

contamination [expected completion 1999].

Occurrence; Exposure

MTBE Water Quality Criteria Workgroup (American Petroleum Institute) (Gene Mancini,

ARCO; Alexis Steen, API)

Eco/aquatic Biota Toxicity.

After literature search to determine gaps in aquatic toxicity database, testing to develop data set

to enable EPA to determine acute and chronic water quality criteria for MTBE in both fresh

water and marine environments [report expected early 1999].

Aquatic Toxicity

National Research Council, Water Science and Technology Board (J. McDonald)

Intrinsic Remediation Study.

Assessment of current scientific understanding of natural processes that degrade or immobilize

contaminants, including oxygenates, in soil and groundwater [report expected November 1999].

Assessment

National Toxicology Program (C.W. Jameson, NTP-NIEHS)

Proposed Listing of MTBE.

NTP to review recommendations of review committees and public comments regarding

recommendations to the Secretary, DHHS, for listing MTBE in the Ninth Edition of the “Report

on Carcinogens;” in December 1998 review, NTP Board of Scientific Counselors Subcommittee

voted against motion to list MTBE as “reasonably anticipated to be a human carcinogen;” final

public comment period open until February 15, 1999 [current status available at:

http://ntp-server.niehs.nih.gov/].

Assessment

North Carolina State University; American Petroleum Institute (M. Hyman, NCSU; Bruce

Bauman, API)

Cometabolism of Gasoline Oxygenates by Alkane-Utilizing Bacteria.

Evaluate and quantify the role of gasoline alkanes as stimulators, inhibitors, and regulators of

in situ bacterial cometabolic biodegradation of MTBE in soil and groundwater [completion

third quarter 2000].

Transformation
54

North Carolina State University; American Petroleum Institute (Robert Borden, NCSU;

Bruce Bauman, API)

Monitoring Degradation: Sampson County, NC.

Monitoring degradation of MTBE, BTEX in plume from UST in shallow coastal aquifer in

Sampson County, NC; leak discovered ~1986, remediated 1990 [ see: Borden, et al., Intrinsic

biodegradation of MTBE and BTEX in a gasoline-contaminated aquifer. Water Resour. Res. 33:

1105-1115, 1997; Borden et al., Field studies of BTEX and MTBE intrinsic bioremediation.

Washington, DC: American Petroleum Institute; Health and Environmental Sciences

Department. API publication no. 4654, 1997; final report expected late 1998].

Transport; Transformation

Oregon Graduate Institute; American Petroleum Institute (Rick Johnson, OGI; 

Bruce Bauman, API)

Removal of MTBE from a Residual Gasoline Source through in situ Air Sparging.

Evaluate the effectiveness of in situ air sparging to remove MTBE from source zone and the

extent that such treatment results in reduction in MTBE in groundwater downgradient [expected

completion early 1999].

Contaminant Removal; Transport; Transformation

Oregon Graduate Institute; Arizona State University; American Petroleum Institute

(H. Hopkins, OGI; Bruce Bauman, API)

Field Tracer Experiment at Port Hueneme, CA.

Deuterated MTBE and tracer injected into existing MTBE plume followed by quarterly sampling

for 1-2 years to determine changes attributable to biodegradation [report expected early 1999].

Transport; Transformation

Rutgers University; American Petroleum Institute (R. Cowan, RU; Bruce Bauman, API)

Ex Situ Biological Treatment of Water Containing MTBE.

Development of technology to biologically treat MTBE-contaminated water ex situ [ongoing

through 2000; interim report expected late 1998].

Contaminant Removal

Rutgers University; Health Effects Institute (Jun-Yan Hong, RU; Maria Costantini, HEI)

Role of Human Cytochrome P450 2E1 in Metabolism and Health Effects of Gasoline Ethers.

Characterize metabolism of MTBE and other ethers in human liver microsomes, with attention to

role of CYP 2E1 and its genotypic distribution in humans; compare ether metabolism in human

liver microsomes versus rat and monkey nasal mucosa microsomes, to illuminate relevance of

animal studies to humans [ongoing through 1998].

Health Effects

Shell Development Corporation (J.P. Salanitro)

MTBE Bioremediation.

Isolation of bacterial culture capable of degrading MTBE in groundwater [ongoing].

Contaminant Removal; Transport; Transformation
55

Shell Development Corporation (P.A. Westbrook)

Polymer-Solvent Interactions.

Prediction of polymer/elastomer response to MTBE-gasoline blends based on response to neat

MTBE [see: Westbrook, P. A. and French, R. N., Elastomer swelling in mixed solvents, Rubber

Chem. Technol. (in press); other reports in preparation].

Release Prevention

State of California, Department of Health Services (Steven Book)

Drinking Water Standards for MTBE.

Secondary and primary maximum contaminant levels (MCLs) for MTBE in drinking water to be

established as required by 1997 state law; proposed secondary MCL of 5 μg/L to protect public

from exposure to MTBE in drinking water at levels than can be smelled or tasted; proposed

primary MCL, in preparation, to utilize Public Health Goal developed by California EPA's

Office of Environmental Health Hazard Assessment (see separate listing) [secondary MCL

adopted November 12, 1998 and currently under review by California Office of Administrative

Law; proposed primary MCL to be released for public comment in spring 1999].

Assessment; Risk Management

State of California, Department of Health Services; U.S. Environmental Protection AgencyRegion 9 (Leah Walker, CA DHS; Judy Bloom, EPA-Region 9)

California Drinking Water Source Assessment Program.

Compile data for MTBE in ground/surface source water from State Drinking Water programs;

evaluate vulnerability to contamination and need for further assessment [ongoing; data

available at http://www.dhs.cahwnet.gov/org/ps/ddwem].

Occurrence

State of California, Environmental Protection Agency, Office of Environmental Health

Hazard Assessment (Juliet Rafol)

Public Health Goal for MTBE.

PHG for MTBE in drinking water intended to pose no significant risk to individuals, including

most sensitive subpopulations, consuming the water daily over a lifetime; PHG considered by

California Department of Health Services in setting primary MCL for drinking water; draft

value, 14 μg/L [report to California Legislature due January 1999].

Assessment

State of California, Environmental Protection Agency, Office of Environmental Health

Hazard Assessment (Susan Luong)

Proposition 65 Listing.

Science Advisory Board subcommittees evaluate whether MTBE meets criteria under California

Proposition 65 for listing as "known to the state to cause cancer or reproductive toxicity"

[subcommittees voted December 1998 not to list MTBE as either a carcinogen or reproductive

toxicant].

Assessment
56

State of California Regional Water Quality Control Board; Lawrence Livermore National

Laboratory; U.S. Environmental Protection Agency-Region 9 (Heidi Temko, CA RWQCB;

Anne Happel, LLNL; Matt Small, EPA)

California GIS Mapping and Data Management Advisory Committee

Provide Governor's Office, legislature, and public entities with information on vulnerability of

Calif. groundwater to MTBE; initiate state-wide geographical information system (GIS) to

manage risk of MTBE contamination to groundwater supplies; investigate in two pilot project

areas the feasibility and appropriateness of establishing a state-wide GIS mapping system

[estimated completion June 1999; data available at http://www-erd.llnl.gov/mtbe/].

Source Characterization; Occurrence

State of California; University of California (Arturo Keller, UC-Santa Barbara)

Health and Environmental Assessment of MTBE.

As mandated by California State Legislature appropriating funds to the University of California,

specific areas of study and reports as follow: (1) Evaluation of the Peer-reviewed Research

Literature on the Human Health, including Asthma, and Environmental Effects of MTBE, John

Froines, UCLA; (2) Integrated Assessment of Sources, Fate & Transport, Ecological Risk and

Control Options for MTBE in Surface and Ground Waters, with Particular Emphasis on

Drinking Water Supplies, John Reuter and Daniel Chang, UC-D; (3) Evaluation of Costs and

Effectiveness of Treatment Technologies Applicable to Remove MTBE and Other Gasoline

Oxygenates from Contaminated Water, Arturo Keller, UCSB; (4) Drinking Water Treatment for

the Removal of Methyl Tertiary Butyl Ether from Ground Waters and Surface Water Reservoirs,

Irwin Suffet, UCLA; (5) Evaluation of MTBE Combustion Byproducts in California

Reformulated Gasoline, Catherine Koshland, UCSB; and (6) Risk-based Decision Making

Analysis of the Cost and Benefits of MTBE and Other Gasoline Oxygenates, Arturo Keller,

UCSB [initial report released November, 1998; final report expected spring 1999; report

available at: http://tsrtp.ucdavis.edu/mtberpt].

Assessment

State of Maine; Departments of Human Services, Environmental Protection, Conservation

(Andrew Smith, Bureau of Health, Maine DHS)

Monitoring Public and Private Water Supplies: Maine.

Preliminary results of random statewide monitoring for MTBE and other gasoline constituents in

public and private drinking water supplies statewide [preliminary report available at

http://www.state.me.us/dep/blwq/gw.htm; final report expected early 1999].

Occurrence

University of California-Davis (John E. Reuter)

Sources, Fate, and Transport of MTBE in Sierra Nevada Multiple Use Lakes.

Study of sources, transport, and fate of MTBE in Lake Tahoe and Donner Lake [ongoing; see 

Reuter et al., Concentrations, sources, and fate of the gasoline oxygenate methyl tert-butyl ether

(MTBE) in a multiple-use lake, Environ. Sci. Technol. 32: 3666-3672, 1998].

Transport; Transformation; Source Characterization
57

University of California-Davis; American Petroleum Institute (E. Schroeder, UC;

Bruce Bauman, API)

Vapor Phase Biodegradation of MTBE.

Evaluate effectiveness of biofilters in MTBE vapor phase treatment; culture aerobic, natural 

microbial consortium that rapidly degrades MTBE, uses MTBE as its sole carbon and energy

source, and has been shown (Eweis et al., Proceedings 90th AWMA Meeting, Toronto, June 8-13,

1997) to degrade MTBE in both liquid and gas streams (biofilters); assess impact of other

organics (e.g., aromatics, alkanes) on MTBE biodegradation; characterize potential limitations

of technology [report expected second quarter 1999].

Contaminant Removal

University of California-Davis; EPA-OSWER-OUST (Thomas Young, UC; David Wiley,

EPA-OSWER-OUST)

Field Verification of UST System Leak Detection Performance.

Evaluate data from UST closures and release investigations from approximately 16 state

environmental agencies to (1) quantify probability of types of leak detection failures (missed

detections, false alarms) for different methods and equipment brands, and (2) understand

sources of failure (e.g., human error, mechanical failure, environmental variables) [report and

database expected late 1999].

Release Prevention

University of Houston; American Petroleum Institute (William G. Rixey, UH; Bruce Bauman,

API)

Characteristics of MTBE from a Gasoline Source.

Characterize dissolution and desorption of MTBE from a gasoline source residually trapped in

soil; assess duration of MTBE in source area; leaching behavior evaluated in laboratory

fixed-bed columns and results modeled [expected completion late 1998].

Transport; Transformation

University of Massachusetts-Amherst; American Petroleum Institute (Derek Lovley, UM;

Bruce Bauman, API)

Anaerobic Degradation of MTBE, BTEX, and PAHs in Petroleum-Contaminated Aquifers.

Determine: 1) potential for ferric iron to serve as electron acceptor for anaerobic

biodegradation of MTBE and BTEX in groundwater and rates associated with this process in

variety of aquifers; 2) anaerobic processes in the source area of fuel spills; 3) anaerobic

biodegradability of PAHs in groundwater [report expected late 1999].

Transport; Transformation; Contaminant Removal

University of Medicine and Dentistry of New Jersey (Clifford P. Weisel)

Modulation of Benzene Metabolism by Exposure to Environmental Mixtures

Evaluate (1) metabolism of benzene when inhaled by humans alone or as part of a mixture of

MTBE or metals such as iron, and (2) in vitro toxicity of metabolites of mixtures such as benzene

and MTBE [ongoing].

Health Effects
58

University of Michigan-National Center for Integrated Bioremediation (Michael Barcelona)

MTBE Behavior in BTEX Plume.

Characterize natural fate and transport of dissolved MTBE/BTEX under different shallow

groundwater redox regimes, and effects of oxygen-releasing material; information on the

evolution of microbial ecology also to be collected [expected completion fourth quarter 1999].

Transport; Transformation

University of Nebraska (H. Noureddini)

Remediation Efficiency for ETBE compared to MTBE.

Comparative experimental studies of removal of ETBE and MTBE from contaminated water by

air stripping and carbon adsorption; literature review of available ETBE research data

[ongoing; unpublished report available upon request].

Contaminant Removal

University of Nevada-Reno (Glenn Miller)

Sampling for MTBE in Lake Tahoe.

Sample for MTBE from various depths and locations, including temperature and meteorology

data; evaluate MTBE and BTEX contamination from watercraft [ongoing].

Occurrence; Source Characterization; Transport; Transformation

University of Northern Iowa; Exxon (C. M. Horan, UNI)

Effect of MTBE on Microbial Consortia.

MTBE added to microbial consortia increased oxygen consumption, but concentrations up to

740 mg/L inhibited mineralization potential of hexadecane up to 50%; although MTBE can be

metabolized in environment, toxicity may adversely affect overall biodegradation of fuel HCs

[ongoing; report available at http://www.engg.ksu.edu/HSRC/95Proceed/horan.html].

Contaminant Removal; Transport; Transformation

University of Notre Dame; Amoco Corporation (Charles Kulpa, UND)

MTBE Biodegradation by Pure Cultures.

Isolation of pure and mixed bacterial strains capable of degrading MTBE in soil and water

[ongoing; see Mo et al., Biodegradation of methyl t-butyl ether by pure bacterial cultures,

Appl. Microbiol. Biotechnol. 47: 69-72, 1996].

Contaminant Removal; Transport; Transformation

University of Oklahoma; American Petroleum Institute (Bruce Bauman, API)

Anaerobic Biodegradation of Gasoline Hydrocarbons and Oxygenates.

Summarize results of previous research on anaerobic processes and continue to evaluate

anaerobic biodegradation of dissolved hydrocarbons, whole gasoline, and oxygenates [drafts of

papers expected March 1999].

Contaminant Removal
59

University of Texas-Austin; American Petroleum Institute (Robert Mace, UT; Bruce

Bauman, API)

Spatial and Temporal Variability of MTBE Plumes in Texas

Characterize spatial and temporal variation of MTBE plumes and their relation to other

dissolved hydrocarbons, the nature of the release source, and site hydrogeology using existing

database of 361 Texas UST sites [expected completion fourth quarter 1998].

Transport; Transformation

University of Washington (Crispin H. Pierce)

Toxicokinetics of Ethyl Tertiary-butyl Ether

Develop quantitative, predictive models that account for person- and gender-specific factors that 

influence ETBE toxicokinetics, using controlled exposures to stable isotope-labeled and

unlabeled compounds and accurate measurements of these compounds and metabolites in blood,

breath, and urine [ongoing].

Health Effects

University of Washington; American Petroleum Institute (Lee Newman, UW; Bruce Bauman,

API)

Phytoremediation of MTBE.

Evaluate capabilities of selected plants to take up, degrade, or transpire MTBE [expected

completion late 1999].

Contaminant Removal

University of Waterloo; American Petroleum Institute (Doug Mackay, UW; Bruce Bauman,

API)

MTBE Natural Attenuation Field Research, Phase 1.

Identify suitable research site and generate initial site characterization data to determine: 

1) mass flux of MTBE from a release site and its influence on the size of the resultant dissolved

phase plume; and 2) natural attenuation processes that act to limit the migration of dissolved

MTBE at that site [ongoing through 2000; interim reports expected annually].

Transport; Transformation

University of Waterloo; American Petroleum Institute (Jim Barker, UW; Bruce Bauman, API)

Monitoring Border Aquifer Plume.

Monitoring of MTBE, BTEX, MeOH, NaCl in experimental plume at Canada Forces Base

Borden, Ontario; began ca. 1988, tracked for 16 months, resumed in 1996 [expected completion

fourth quarter 1998; e.g., see Schirmer and Barker, A study of long-term MTBE attenuation in

the Borden Aquifer, Ontario, Canada, Ground Water Monit. Rem. 18: 113-122, 1998].

Transport; Transformation
60

University of Wurzburg; Health Effects Institute (Wolfgang Dekant, WW; Maria Costantini,

HEI)

Comparative Biotransformation of MTBE, ETBE, TAME, and DIPE in Rats and Humans.

Compare relative excretion of ether metabolites in humans and rats exposed in vitro and in vivo

via inhalation, with attention to individual differences [ongoing through 1998].

Health Effects

U.S. Centers for Disease Control and Prevention (David L. Ashley)

Blood Levels of MTBE and TBA.

As part of NHANES IV, determine a reference range of blood levels of MTBE and TBA in

non-occupationally exposed U.S. residents and examine relationship of these levels to local

MTBE usage in gasoline and presence of MTBE in household water samples [pilot work begins

January 1999; survey begins April 1999].

Exposure

U.S. Environmental Protection Agency, Office of Prevention, Pesticides, and Toxic

Substances (Catherine Roman, EPA-OPPTS-CCD)

Proposed Children's Health Test Rule.

Toxicity testing of selected chemicals, including MTBE and TBA, with exposure potential for

children [draft proposed rule in preparation; notice of proposed rule making expected March

1999 and final rule December 1999].

Health effects

U.S. Environmental Protection Agency, Office of Research and Development (Thomas F.

Speth, EPA-ORD-NRMRL)

Cost Comparison of MTBE Removal Technologies.

Evaluation of ozone/peroxide oxidation and air stripping technologies for MTBE removal; air

stripping to include off-gas control by adsorption and pilot-scale experiments [expected

completion 2000].

Contaminant Removal

U.S. Environmental Protection Agency, Office of Research and Development (Fran Kremer,

EPA-ORD-NRMRL)

Natural Attenuation of MTBE in Ground Water and Soils.

Field and laboratory studies on UST sites impacted with MTBE; preparation of technical

resource documents on natural biodegradation of MTBE and associated HCs in ground water

and soils, and on the potential for enhanced biodegradation [ongoing].

Transport; Transformation; Contaminant Removal

U.S. Environmental Protection Agency, Office of Research and Development (John Wilson,

EPA-ORD-NRMRL)

Natural Attenuation of MTBE.

Field and laboratory study evaluating the role of natural attenuation of MTBE in a fuel plume at

Elizabeth City, NC, and other sites [ongoing; report due FY2000].

Transport; Transformation
61

U.S. Environmental Protection Agency, Office of Research and Development (James Prah,

EPA-ORD-NHEERL)

Human Pharmacokinetics of MTBE.

Pharmacokinetics study of human volunteers given multiple acute exposures to MTBE by

inhalation, oral, and dermal routes [scheduled completion 1999].

Health Effects

U.S. Environmental Protection Agency, Office of Research and Development (Jim Weaver,

EPA-ORD-NERL)

Simulation of Multicomponent Gasoline Dissolution.

Aquifer transport, leaching, and chemical property estimation models used to study

multicomponent dissolution from MTBE- and non MTBE-gasolines, effects of MTBE on

dissolution of BTEX, and minimum number of components required to simulate dissolution of a

given gasoline component [report expected May 1999].

Transport; Transformation

U.S. Environmental Protection Agency, Office of Research and Development (Peter Gabele,

EPA-ORD-NERL)

Marine Engine Emissions Characterization.

Characterize emissions in air and water from small outboard (<15hp) engines using 12%-vol

MTBE-gasoline [expected completion fall 1999].

Source Characterization

U.S. Environmental Protection Agency, Office of Research and Development; IT

Corporation (Anthony Tafuri, EPA-ORD-NRML)

Technologies for Remediating Petroleum-contaminated Soil.

Studies (bench and pilot field) of hydrogen peroxide with Fenton’s reagent to oxidize MTBE in

soil and water; identify intermediate products that may develop in treatment process and

determine operational parameters (Chen et al., Chemical oxidation treatment of petroleum

contaminated soil using Fenton’s reagent, J. Environ. Sci. and Health, A33: 987-1008, 1998)

[ongoing].

Contaminant Removal

U.S. Environmental Protection Agency, Office of Research and Development; New York

State Department of Environmental Conservation (Jim Weaver, EPA-ORD-NERL; Joseph

Haas, NY DEC)

Modeling Plume: East Patchogue and Uniondale.

3-D monitoring and modeling of MTBE, BTEX in contaminant plume from UST site on Long

Island, NY, a demonstration site for EPA Hydrocarbon Spill Screening Model (HSSM)

[J. Weaver, Transport and transformation of BTEX and MTBE in a sand aquifer, Ground Water

Monit. Remed. (accepted); additional report in preparation].

Transport; Transformation
62

U.S. Environmental Protection Agency, Office of Research and Development; U.S.

Environmental Protection Agency-Region 9 (Lance Wallace, EPA-ORD-NERL; Henry Lee,

EPA-Region 9)

MTBE Exposure During Showering.

Personal exposure measurements of MTBE in shower microenvironment [expected to begin

1999].

Exposure

U.S. Geological Survey; American Petroleum Institute (Art Baehr, USGS; H. Hopkins, API)

Modeling Groundwater Impacts from MTBE Vadose Zone Transport.

Determine minimum mass source in vadose zone to create a persistent oxygenate impact to

groundwater [begin December 1998; expected completion second quarter 1999].

Occurrence; Source Characterization

U.S. Geological Survey-NAWQA (John Zogorski, Wayne Lapham, USGS)

National Retrospective Analyses: Selected Areas.

Retrospective analysis of VOC and limited MTBE data in about 20 U.S. areas: CA, ID, IA, NJ,

NY, TX, WI; several other areas available for further analyses; additional data being sought for

1998-1999 [ongoing through 2000; findings published yearly

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence; Source Characterization

U.S. Geological Survey-NAWQA (Mary Ann Thomas, USGS)

Groundwater Monitoring: Michigan.

Characterization of groundwater in residential suburban Detroit area 1996-1998; preliminary

data analysis did not indicate presence of MTBE or TBA [data release expected mid-1999

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence; Source Characterization

U.S. Geological Survey-NAWQA (Arthur Baehr, Mark Ayers, USGS)

Glassboro Comprehensive Urban Study.

Monitor MTBE, VOCs in air, precipitation, surface water, unsaturated zone, ground water in

Glassboro, NJ area aquifer [ongoing 1996-2000; project description published; shallow

groundwater VOC data published; research published periodically

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation; Source Characterization

U.S. Geological Survey-NAWQA (John Zogorski, USGS)

Monitoring Urban Storm Water: Selected Areas.

Monitor urban storm water for VOCs, including MTBE, in 16 U.S. metropolitan areas: Boise,

Phoenix, Colorado Springs, Denver, San Antonio, Dallas, Omaha, Independence, Little Rock,

Davenport, Baton Rouge, Mobile, Huntsville, Birmingham, Montgomery, Atlanta [reports

available upon request (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence; Source Characterization
63

U.S. Geological Survey-NAWQA; U.S. Environmental Protection Agency-Office of Water

(Steve Grady, USGS; Mike Osinski, EPA-OW)

Retrospective Analyses: New England-Mid Atlantic.

Retrospective data analysis for MTBE and other VOCs in ground/drinking water in 12 southern

New England and Mid-Atlantic states; focus primarily on ambient ground water and PWS

drinking water data for MTBE and other VOCs, with one objective to create protocol for state

drinking water quality data collection [design completed; retrospective approximately 50%

complete; report expected late 1999 (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence; Source Characterization

U.S. Geological Survey-NAWQA; Oregon Graduate Institute (John Zogorski, USGS; 

Jim Pankow, Wes Jarrell, OGI)

Plant Transpiration.

Measurement of plant transpiration on VOC levels including MTBE [report and journal article

expected 1999 (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation

U.S. Geological Survey-NAWQA; Oregon Graduate Institute; University of Washington

(John Zogorski, USGS; Jim Pankow, OGI; Bill Asher)

VOC Behavior and Fate.

Modeling the behavior and fate of VOCs including MTBE in PWS reservoirs [journal article and

report expected 1999 (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation

U.S. Geological Survey-NAWQA (Paul Squillace, Mike Moran, John Zogorski, USGS)

Occurrence of MTBE and Other VOCs in Ambient Groundwater.

VOCs in groundwater of the United States, 1985-1995 [journal article in preparation

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence

U.S. Geological Survey-NAWQA; Oregon Graduate Institute (John Zogorski, USGS; Jim

Pankow, Rick Johnson, OGI)

Modeling MTBE Transport to a Production Well.

Preliminary evaluation of factors that influence the capture of MTBE UST release by a

hypothetical production well [article expected early 1999

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation

U.S. Geological Survey-NAWQA; Oregon Graduate Institute (John Zogorski, USGS; 

Jim Pankow, OGI)

VOC Analytic Methods: Air.

Analytic methods developed for VOCs, including MTBE, TAME, DIPE, and ETBE, in ambient

air [article to appear in Analytical Chemistry, late 1998 or early 1999

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence (Analytic Methods)
64

U.S. Geological Survey; Oregon Graduate Institute (John Zogorski, USGS; James Pankow,

OGI)

Degradation Assessment.

Determine degradation pathways, by-products, kinetics, and their relationship to varied

geological environments for MTBE, TBA, TBF, TAME, TAA, and acetone based on monitoring

data from several plumes and lab studies [field monitoring and lab studies continuing in 1998;

project findings and lab analytical method published

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation

U.S. Geological Survey; Oregon Graduate Institute (John Zogorski, USGS; James Pankow,

OGI)

Modeling Non-point Source Inputs.

Modeling of atmospheric and land-based non-point source inputs of MTBE to ground water

systems (see also USGS: Glassboro comprehensive urban study) [ongoing 1996-2000; research

published periodically (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Source Characterization; Occurrence; Transport; Transformation

U.S. Geological Survey-Toxics Hydrology Program (Herb Buxton, John Zogorski,

J. Landmeyer)

Monitoring Plume: Beaufort, SC.

Ongoing monitoring of shallow ground water and unsaturated zone above the ground water

plume for VOCs, including MTBE, BTEX, TBA, for movement and degradation since 1991 at

Laurel Bay UST (Beaufort Marine Corps Air Station, SC); remediated 1993; flow and

contaminant modeling; long-term hydrology study site [ongoing; project scope and findings

through 1997 published (see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Transport; Transformation

U.S. Geological Survey (Carol Boughton)

Survey of Man-Made Organic Compounds in Lake Tahoe and Selected Tributaries,

California-Nevada 1998-99.

Sample multiple sites on Lake Tahoe and major tributaries for the presence of organochlorine,

semi-volatile industrial, synthetic-hydrocarbon compounds (including MTBE) and soluble

pesticides [results expected to be published in 1999

(see http://wwwsd.cr.usgs.gov/nawqa/pubs/)].

Occurrence

Western States Petroleum Association (Jeff Sickenger)

Well Purging Study: California.

Comparison of MTBE, BTEX, and TPH-g in groundwater samples before and after purging at

CA wells: concentrations higher before than after purging, variability of before/after

concentrations comparable to variability between purging methods; high variability in small

population of sites due to site-specific conditions [completed (Final Report: the California

groundwater purging study for petroleum hydrocarbons, SECOR International, Inc., 1996;

Lundegard et al., Net benefit of well purging reevaluated, Environ. Geosci. 4: 111-118, 1997;
65

see http://www.secor.com/purge/purge.htm); however, also see: Flood, F., New study advocates

no purging prior to sampling, http://www.grac.org/spring97/article2.htm].

Contaminant Removal; Transport; Transformation

Woodward-Clyde; American Petroleum Institute (R. Claff, API)

Occurrence, Treatment, and Impact of Oxygenates in Effluents.

Characterize and quantify presence of oxygenates in petroleum marketing terminal and refinery

wastewater streams and treatment processes; identify and quantify fate of oxygenates in terminal

and refinery wastewater treatment facilities [expected completion late 1999].

Occurrence; Transport; Transformation

World Health Organization - IPCS (Edward Smith, WHO Geneva)

Environmental Health Criteria for MTBE.

Critical review of effects of MTBE on human health and the environment [in press].

Assessment