United States
Environmental Protection
Agency
Office of Research
and Development
Washington, DC 20460
EPA/600/R-98/048
December 1998
«EPA
Oxygenates in Water:
Critical Information
and Research Needs
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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
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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.
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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
in
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Table of Contents
(cont'd)
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
IV
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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
Contributors
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
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
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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, C A 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
VI
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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 Heffelfmger
Office of Solid Waste and Emergency
Response
Office of Underground Storage Tanks
Washington, DC 20460
Ronald Landy
Region 3
Philadelphia, PA 19107
Maureen Lewi son
Office of Solid Waste and Emergency
Response
Office of Underground Storage Tanks
Washington, DC 20460
vn
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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, C A 94105
Vlll
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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
IX
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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.
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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.
XI
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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 iig/L1 to over 20,000 |ig/L (Squillace et al., 1996). Reports of point-source MTBE
contamination of drinking water sources at well over 100 |ig/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
ll ng/L = 1 part per billion (ppb).
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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 jig/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 |ig/L in California to 230 |ig/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
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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
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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
(TEA). 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).
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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:
• Source Characterization
• Transport
• Transformation
• Occurrence
• Exposure
• Aquatic Toxicity
• Health Effects
• Release Prevention
• 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
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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 |ig/L, with a median of 1.5 |ig/L. Modeling calculations have predicted MTBE
concentrations in rainwater ranging from <1 |ig/L to 3 |ig/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
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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.
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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 |ig/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
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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
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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.
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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 TEA (Mormile et al., 1994), but
comprehensive identification of biodegradation products and reaction pathways has not been
undertaken.
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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
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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
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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 |ig/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 |ig/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 |ig/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 |ig/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
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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 |ig/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 |ig/L. Only one of the more than 1,000 samples exceeded the EPA Drinking
Water Advisory of 20-40 |ig/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 |ig/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 |ig/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 jig/L. For the Maine PWSs, 125 (16%) of the samples had detectable levels of
MTBE, with no samples above the 35 jig/L standard and 48 (6.1%) between 1 jig/L and 35 |ig/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
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from 17 (4%) of 450 wells tested positive for MTBE at a minimum reporting level of 0.2 |ig/L,
with the highest concentration reported at 8.0 |ig/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 |ig/L.
These data are based on a detection limit of 5 |ig/L. If all detections are considered, including
possible false positives below 5 jig/L, 65 sources (1.4%) had detectable levels of MTBE. None
of the surface water samples exceeded 35 jig/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 (SOWA),
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
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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
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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 TEA
concurrently with the ether oxygenates, although the detection limit for TEA is significantly
higher than the detection limits for the ether oxygenates—approximately 30 to 40 |ig/L for TEA
and less than 1 jig/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 TEA.
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 TEA as a primary oxygenate, as a contaminant of MTBE, and as a degradation
product of MTBE, the inclusion of TEA in ambient ground water quality monitoring programs is
advisable. It also would be useful to monitor for TEA at specific sites where MTBE
contamination is known or suspected to have occurred.
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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 TEA, 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
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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 |ig/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 |ig/L for taste and from 15 to 180 |ig/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 |ig/L to 190 |ig/L. At concentrations of 2 to 5 |ig/L, the consensus judgment of the panelists
was that the taste of MTBE could be described as "sweet." At concentrations of 21 to 190 jig/L,
the characterization was either "solvent" or "sweet solvent." Similar characteristics were
attributed to the odor of MTBE at concentrations of 21 to 190 |ig/L. The panelists also were
asked to rate the intensity of the taste and odor, which they considered "objectionable" at a
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concentration of approximately 50 |ig/L for taste and at approximately 90 to 100 |ig/L for odor.
Note that these tests were conducted with nonchlorinated, odor-free water at 25 °C.
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).
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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 TEA 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
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(e.g., metabolites such as TEA) 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
TEA for selected aquatic species (e.g., Daphnia magna, Pimephalespromelas, 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.
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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). TEA is of relevance
both as a metabolite of MTBE (Borghoff et al., 1996) and as an oxygenate or oxygenate
by-product. Ingested TEA has been evaluated in rats and mice in a chronic bioassay by the
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National Toxicology Program (Cirvello et al., 1995). Long-term exposure to TEA 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 TEA 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 TEA 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
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(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 TEA may be adequate to characterize the oral toxicity of TEA. Given the
potential for human exposure to TEA 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 TEA 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 TEA), 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
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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 °C).
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Hotaling (1995) tested 15 elastomers at 46 °C 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.
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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
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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.
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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 |ig/L, the carbon beds need to be
regenerated frequently. Other ether oxygenates have slightly lower solubilities than MTBE and
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thus would be more effectively adsorbed. However, alcohol oxygenates such as ethanol and TEA
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-to-
water 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,
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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, TEA, 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 TEA.
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
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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
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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
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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
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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.
• Determination of the relative contributions of point and non-point sources of oxygenate fluxes
to surface and ground waters.
• Determination of oxygenate biodegradation rates and pathways under representative
geochemical conditions, and identification of degradation by-products and their environmental
fate.
• Inclusion of oxygenate analytes and principal suspected transformation products wherever VOC
monitoring of water is routinely performed.
• Statistically representative sampling of public and private water supplies and modeling of
multi-media, multi-pathway personal exposures for estimating population distributions of
37
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exposures; modeling and empirical studies of "high-end" microenvironmental exposure
scenarios.
• 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.
• More extensive evaluation of oxygenate effects on materials used in tanks and pipelines,
especially after aging over a period of years.
• 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.
• 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.
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meeting; April; San Francisco, CA. Natl. Meet. Am. Chem. Soc. Div. Environ. Chem. 37: 394-397.
Steffan, R. J.; McClay, K.; Vainberg, S.; Condee, C. W.; Zhang, D. (1997) Biodegradation of the gasoline
oxygenates methyl fer/-butyl ether, ethyl fer/-butyl ether, and fer/-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.
U.S. Department of Energy. (1995) Petroleum supply annual 1995: volume 1. Washington, DC: Energy
Information Administration, Office of Oil & Gas; report no. DOE/EIA-0340(95).
U.S. Environmental Protection Agency. (1992) Alternative fuels research strategy [external review draft].
Washington, DC: Office of Research and Development; report no. EPA/600/AP-92/002.
U.S. Environmental Protection Agency. (1993) Assessment of potential risks of gasoline oxygenated with methyl
tertiary butyl ether (MTBE). Washington, DC: Office of Research and Development; November; report no.
EPA/600/R-93/206.
U.S. Environmental Protection Agency. (1994) Health risk perspectives on fuel oxygenates. Washington, DC:
Office of Research and Development; report no. EPA 600/R-94/217.
46
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Center for Environmental Assessment; report no. EPA/600/R-96/069. Available from: NTIS, Springfield,
VA; PB96-190665REB.
U.S. Environmental Protection Agency. (1997) Drinking water advisory: consumer acceptability advice and health
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EPA-822-F-97-008.
U.S. Environmental Protection Agency. (1998a) 1996 toxics release inventory public data release. Washington,
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gasoline and non-baseline (oxygenated) gasoline groups under section 211(b) of the Clean Air Act [letter
from Margo T. Oge, Director, Office of Mobile Sources to Carol Henry, Director, Health and Environmental
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2. Available online at: http://www.epa.gov/oms/consumer/fuels/mtbe/mtbe.htm.
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Washington, DC: American Petroleum Institute; API publication 4591.
Vetrano, K. M. (1993b) Final report to ARCO Chemical Company on the odor and taste threshold studies
performed with methyl tertiary-butyl ether (MTBE) and ethyl tertiary-butyl ether (ETBE). Windsor, CT:
TRC Environmental Corporation; project no. 13442-M31.
Wallington, T. I; Dagaut, P.; Liu, R.; Kurylo, M. J. (1988) Gas-phase reactions of hydroxyl radicals with the fuel
additives methyl tert-butyl ether and fer/-butyl alcohol over the temperature range 240-440 K. Environ. Sci.
Technol. 22: 842-844.
Weisel, C. P.; Jo, W.-K. (1996) Ingestion, inhalation, and dermal exposures to chloroform and trichloroethene
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Wilkes, C. R.; Small, M. J.; Davidson, C. I.; Andelman, J. B. (1996) Modeling the effects of water usage and
co-behavior on inhalation exposures to contaminants volatilized from household water. J. Exposure Anal.
Environ. Epidemiol. 6: 393-412.
Wyborny, L. A., II. (1997) Oxy-water res strategy question -reply [email memorandum to J. Michael Davis, U.S.
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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.
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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. I; 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].
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APPENDIX 1
CHEMICAL PROPERTIES OF SELECTED OXYGENATES
Chemical Name
CAS Registry No.
Synonyms
Molecular
Weight (g/mol)
Molecular
Formula
Structural
Formula
Boiling Point
(at 760 mm Hg)
Vapor Pressure
(mm Hg at
20 °C)
Vapor Density
(air=l)
Density
(g/mlat20 °C)
Solubility
(g/100 g water)
Henry's Law
Constant
(Atm-m3)/
(g-mole)
Dimensionless
LogKoc
Log Kow
Methyl Tertiary
Butyl Ether
1634-04-4
MTBE; 2-methyl,
2-methoxy propane;
tert-butyl methyl
ether; methyl tert
butyl ether;
methyl-tert-butyl
ether
88.15
C5H120
CH3OC(CH3)3
55.2 °C
240
3.1
0.74
4.8
5.28E-4 to 3E-3
2.2E-2to 1.2E-1
0.55 to 0.91
0.94 to 1.30
Ethyl Tertiary
Butyl Ether
637-92-3
ETBE; tert-butyl
ethyl ether; propane,
2-ethoxy-2methyl;
1, 1 -dimethyl ethyl
ether
102.18
C6H140
(CH3)3COCH2CH3
72.2 °C
130
3.6
0.74
1.2
2.64E-3
0.11
NA
NA
Tertiary Amyl
Methyl Ether
994-05-8
TAME; 2-methoxy-2
methylbutane; methyl
tert-pentyl ether;
1 , 1 -dimethy Ipropy 1
methyl ether; methyl
tert-amyl ether
102.18
QH140
CH3CH2C(CH3)2OCH3
86.3 °C
75
3.6
0.77
1.2
1.95E-3
0.081
NA
NA
Diisopropyl
Ether
108-20-3
DIPE; 2'2-
oxybispropane;
2-isopropoxy-
propane
102.18
QH140
(CH3)2CHOCH
(CH3)2
68.2 °C
159
3.6
0.73
0.2
4.77E-3
0.199
1.13
1.52
49
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CHEMICAL PROPERTIES OF SELECTED OXYGENATES (cont'd)
Chemical Name
CAS Registry No.
Synonyms
Molecular
Weight (g/mol)
Molecular
Formula
Structural
Formula
Boiling Point
(at 760 mm Hg)
Vapor Pressure
(mm Hg at 20 °C)
Vapor Density
(air=l)
Density
(g/mLat20 °C)
Solubility
(g/100 g water)
Henry's Law
Constant
(Atm-m3)/
(g-mole)
Dimensionless
LogKoc
Log Kow
Tertiary Amyl Ethyl
Ether Dimethyl Ether
919-94-8 115-10-6
TAEE; ethyl tert-amyl DME; methane,
ether; butane, oxybis
2-ethoxy -2 -methyl
116.20 46.07
C7H160 C2H60
CH3CH2C(CH3)2OCH2C CH3OCH3
H3
102 °C -24.8 °C
NA 758 to 5086*
4.0 1.6
0.75 0.66
NA 4.7 to 35.3
NA 4.89E-4 to 9.97E-4
NA 2.03E-2to4.15E-2
NA -0.29
NA 0.10
Tertiary Butanol
75-65-0
TEA; tertiary butyl
alcohol; 2-propanol,
2-methyl
74.12
C4H100
(CH3)3COH
82.4 °C
41
2.6
0.79
miscible
1.21E-5
5.03E-4
1.57
0.35
Ethanol
64-17-5
ethanol;
ethyl alcohol
46.07
C2H60
CH3CH2OH
78.5 °C
44
1.6
0.79
miscible
6.91E-6
2.83E-4
-0.14
-0.32
*At25°C
50
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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 andBTEX[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,
CUT; John Kneiss, OF A)
MTBE Cancer Mechanisms.
Study of role of alpha-2u-globulin in MTBE-induced kidney tumors in male rats [report expected
late 1998].
Health Effects
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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 93/6''/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 ofC-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
52
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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
53
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North Carolina State University; American Petroleum Institute (Robert Borden, NCSU;
Bruce Bauman, API)
Monitoring Degradation: Sampson County, NC.
Monitoring degradation ofMTBE, B'TEX in plume from LIST in shallow coastal aquifer in
Sampson County, NC; leak discovered-1986, remediated 1990 [see: Borden, et al, Intrinsic
biodegradation ofMTBE and BTEX in a gasoline-contaminated aquifer. Water Re sour. 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 ofMTBE 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 ofMTBE and other ethers in human liver microsomes, with attention to
role ofCYP 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
54
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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 ofS^g/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 Agency-
Region 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.
PHGfor 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 jUg/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
55
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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
[estimatedcompletion 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 Renter 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 andDonner 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
56
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University of California-Davis; American Petroleum Institute (E Schroeder, UC;
Bruce Bauman, API)
Vapor Phase Biodegradation of MTBE.
Evaluate effectiveness ofbiofilters 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
57
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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 ofmicrobial 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 water craft [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 ofhexadecane 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
58
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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
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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 TEA.
As part ofNHANESlV, determine a reference range of blood levels of MTBE and TEA 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 TEA, 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 FY2000J.
Transport; Transformation
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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 ofBTEX, 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, BTEXin 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
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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 ofVOC 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, groundwater 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
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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 andPWS
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, andETBE, 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)
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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, TEA, 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, TEA, 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 1997published (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 oforganochlorine,
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;
Lundegardet al, Net benefit of well purging reevaluated, Environ. Geosci. 4: 111-118, 1997;
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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
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