United States
Environmental Protection Agency
Office of Water
4304
EPA-822-F-97-009
December 1997
CDA FACT SHEET
Drinking Water Advisory: Consumer Acceptability
Advice and Health Effects Analysis on Methyl
Tertiary-Butyl Ether (MtBE)
The Advisory
The U.S. Environmental Protection Agency (EPA) Office of Water is issuing an Advisory on
methyl tertiary-butyl ether (MtBE)in drinking water. This Advisory provides guidance to communities
exposed to drinking water contaminated with MtBE. This document supersedes any previous drafts
of drinking water health advisories for this chemical.
What is an Advisory?
The U.S. EPA Health Advisory Program was
initiated to provide information and guidance to
individuals or agencies concerned with
potential risk from drinking water contaminants
for which no national regulations currently
exist. Advisories are not mandatory standards
for action. Advisories are used only for
guidance and are not legally enforceable. They
are subject to revision as new information
becomes available. EPA's Health Advisory
program is recognized in the Safe Drinking
Water Act Amendments of 1996, which state
in section 102(b)(1)(F):
"The Administrator may publish health
advisories (which are not regulations)
or take other appropriate actions for
contaminants not subject to any
national primary drinking water
regulation".
As its title indicates, this Advisory includes
consumer acceptability advice as "appropriate"
under this statutory provision, as well as a health
effects analysis.
What is MtBE?
MtBE is a volatile, organic chemical. Since the
late 1970's, MtBE has been used as an octane
enhancer in gasoline. Because it promotes
more complete burning of gasoline, thereby
reducing carbon monoxide and ozone levels, it
is commonly used as a gasoline additive in
localities which do not meet the National
Ambient Air Quality Standards.
In the Clean Air Act of 1990 (Act), Congress
mandated the use of reformulated gasoline
(RFG) in areas of the country with the worst
ozone or smog problems. RFG must meet
certain technical specifications set forth in the
Act, including a specific oxygen content.
Ethanol and MtBE are the primary oxygenates
used to meet the oxygen content requirement.
MtBE is used in about 84% of RFG supplies.
Currently, 32 areas in a total of 18 states are
participating in the RFG program, and RFG
accounts for about 30% of gasoline nationwide.
Studies identify significant air quality and public
health benefits that directly result from the use
of fuels oxygenated with MtBE, ethanol or other
chemicals. The refiners' 1995/96 fuel data
submitted to EPA indicate that the national
emissions benefits exceeded those required.
The 1996 Air Quality Trends Report shows that
toxic air pollutants declined significantly between
1994 and 1995. Early analysis indicates this
progress may be attributable to the use of RFG.
Starting in the year 2000, required emission
reductions are substantially greater, at about
27% for volatile organic compounds, 22% for
toxic air pollutants, and 7% for nitrogen oxides.
Why is MtBE a Drinking Water Concern?
A limited number of instances of significant
contamination of drinking water with MtBE have
occurred due to leaks from underground and
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above ground petroleum storage tank systems
and pipelines. Due to its small molecular size
and solubility in water, MtBE moves rapidly into
groundwater, faster than do other constituents of
gasoline. Public and private wells have been
contaminated in this manner. Non-point
sources, such as recreational watercraft, are
most likely to be the cause of small amounts of
contamination in a large number of shallow
aquifers and surface waters. Air deposition
through precipitation of industrial or vehicular
emissions may also contribute to surface water
contamination. The extent of any potential for
build-up in the environment from such deposition
is uncertain.
Is MtBE in Drinking Water Harmful?
Based on the limited sampling data currently
available, most concentrations at which MtBE
has been found in drinking water sources are
unlikely to cause adverse health effects.
However, EPA is continuing to evaluate the
available information and is doing additional
research to seek more definitive estimates of
potential risks to humans from drinking water.
There are no data on the effects on humans of
drinking MtBE-contaminated water. In laboratory
tests on animals, cancer and noncancer effects
occur at high levels of exposure. These tests
were conducted by inhalation exposure or by
introducing the chemical in oil directly to the
stomach. The tests support a concern for
potential human hazard. Because the animals
were not exposed through drinking water, there
are significant uncertainties about the degree of
risk associated with human exposure to low
concentrations typically found in drinking water.
How Can People be Protected?
MtBE has a very unpleasant taste and odor, and
these properties can make contaminated
drinking water unacceptable to the public. This
Advisory recommends control levels for taste
and odor acceptability that will also protect
against potential health effects.
Studies have been conducted on the
concentrations of MtBE in drinking water at
which individuals can detect the odor or taste of
the chemical. Humans vary widely in the
concentrations they are able to detect. Some
who are sensitive can detect very low
concentrations, others do not taste or smell the
chemical even at much higher concentrations.
Moreover, the presence or absence of other
natural or water treatment chemicals can mask
or reveal the taste or odor effects.
Studies to date have not been extensive enough
to completely describe the extent of this
variability, or to establish a population threshold
of response. Nevertheless, we conclude from
the available studies that keeping
concentrations in the range of 20 to 40
micrograms per liter (ug/L) of water or below will
likely avert unpleasant taste and odor effects,
recognizing that some people may detect the
chemical below this.
Concentrations in the range of 20 to 40 ug/L are
about 20,000 to 100,000 (or more) times lower
than the range of exposure levels in which
cancer or noncancer effects were observed in
rodent tests. This margin of exposure is in the
range of margins of exposure typically provided
to protect against cancer effects by the National
Primary Drinking Water Standards under the
Federal Safe Drinking Water Act. This margin is
greater than such standards typically provided to
protect against noncancer effects. Thus,
protection of the water source from unpleasant
taste and odor as recommended will also
protect consumers from potential health effects.
EPA also notes that occurrences of ground
water contamination observed at or above this
20-40 //g/l taste and odor threshold - that is,
contamination at levels which may create
consumer acceptability problems for water
suppliers - have to date resulted from leaks in
petroleum storage tanks or pipelines, not from
other sources.
What is Being Done About the Problem?
Research
The EPA, other federal and state agencies, and
private entities are conducting research and
developing a strategy for future research on all
health and environmental issues associated with
the use of oxygenates. To address the research
needs associated with oxygenates in water, a
public, scientific workshop to review the EPA's
Research Strategy for Oxygenates in Water
document was held on October 7, 1997.
Discussions included current, or soon to be
started, oxygenate projects in the areas of
environmental monitoring/occurrence, source
characterization, transport and fate, exposure,
toxicity, remediation, among others. The
identified research will help provide the
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necessary information to better understand the
health effects related to MtBE and other
oxygenates in water, to further our knowledge on
remediation techniques, and to direct future
research planning towards the areas of highest
priority. This document is expected to be
available for external review by January, 1998.
EPA plans to hold a workshop with industry to
secure commitments on conducting the needed
research in the Spring of 1998.
The EPA has also recently notified a consortium
of fuel and fuel additive manufacturers of further
air-related research requirements of industry
under section 211(b) of the Clean Air Act (CAA).
The proposed animal inhalation research
focuses on the short and long term inhalation
effects of conventional gasoline and MtBE
gasoline in the areas of neurotoxicity,
immunotoxicity, reproductive and developmental
toxicity, and carcinogenicity. The testing
requirements will also include an extensive array
of human exposure research. This research will
be completed at varying intervals over the next
five years and could be very useful for assessing
risks from MtBE in water, depending on the
outcome of studies underway on the
extrapolation of inhalation risks to oral ingestion.
When adequate research on the human health
effects associated with ingestion of oxygenates
becomes available, the EPA Office of Water will
issue a final health advisory to replace the
present advisory.
Monitoring
The EPA's Office of Water has also entered into
a cooperative agreement with the United States
Geological Survey (USGS) to conduct an
assessment of the occurrence and distribution of
MtBE in the 12 mid-Atlantic and Northeastern
states. Like California, these States have used
MtBE extensively in the RFG and Oxygenated
Fuels programs. This study will supplement the
data gathered in California and will attempt to
shed light on the important issues of (1)
whether or not MtBE has entered drinking water
distribution systems or impacted drinking water
source supplies, and (2) determine if point (land)
or nonpoint sources (air) are associated with
detections of MtBE in ground water resources.
Activities are underway to begin collecting data
in early 1998.
Underground Storage Tanks
Under EPA regulations, leaks from underground
storage tank systems (USTs) which may cause
contamination of groundwater with MtBE or
other materials are required to be reported to
the "implementing agency" which, in most
cases, is a state agency. The EPA Office of
Underground Storage Tanks and State and local
authorities are addressing the cleanup of water
contaminated by such leaks. All USTs installed
after December 1988 have been required to
meet EPA regulations for preventing leaks and
spills. All USTs that were installed prior to
December 1988 must be upgraded, replaced, or
closed to meet these requirements by
December 1998.
Safe Drinking Water Act Candidate List
The Safe Drinking Water Act (SDWA), as
amended in 1996, requires EPA to publish a list
of contaminants that may require regulation,
based on their known or anticipated occurrence
in public drinking water systems. The SDWA,
as amended, specifically directs EPA to publish
the first list of contaminants (Contaminant
Candidate List, or CCL) by February 1998, after
consultation with the scientific community,
including EPA's Science Advisory Board, and
after notice and opportunity for public comment.
The amendments also require EPA to select at
least five contaminants from the final CCL and
make a determination of whether or not to
develop regulations, including drinking water
standards, for them by 2001. The EPA Office
Water published a draft CCL for public comment
in the Federal Register on Octobers, 1997 (62
FR 52194). MtBE is included on the draft CCL
based on actual MtBE contamination of certain
drinking water supplies, e.g., Santa Monica, and
the potential for contamination of other drinking
water supplies in areas of the country where
MtBE is used in high levels.
How Can I Get My Water Tested?
A list of local laboratories that can test your
water for MtBE can be obtained from your state
drinking water agency. The cost for testing is
approximately $150 per sample. The analysis
should be performed by a laboratory certified to
perform EPA certified methods. The laboratory
should follow EPA Method 524.2 (gas
chromatography/mass spectrometry).
How Can I Get Rid of MtBE If It's In My
Water?
In most cases it is difficult and expensive for
individual home owners to treat their own water.
Any detection of MtBE should be reported to
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your local water authority, who can work with
you to have your water tested and treated.
Are There Any Recommendations for State or
Public Water Suppliers?
Public water systems that conduct routine
monitoring for volatile organic chemicals can test
for MtBE at little additional cost, and some
States are already moving in this direction.
Public water systems detecting MtBE in their
source water at problematic concentrations can
remove MtBE from water using the same
conventional treatment techniques that are used
to clean up other contaminants originating from
gasoline releases, such as air stripping and
granular activated carbon (GAC). However,
because MtBE is more soluble in water and
more resistant to biodegradation than other
chemical constituents in gasoline, air stripping
and GAC treatment requires additional
optimization and must often be used together to
remove MtBE effectively from water. The costs
of removing MtBE will be higher than when
treating for gasoline releases that do not contain
MtBE. Oxidization of MtBE using
UV/peroxide/ozone treatment may also be
feasible, but typically has higher capital and
operating costs than air stripping and GAC.
John Brophy, U.S. EPA, Office of Air and
Radiation; phone (202) 564-9068;
www.epa.gov/omswww/omsfuels.htm
For Further Information on the Advisory,
Contact:
Charles Abernathy
U.S. EPA, Office of Water, Mail Code 4304
1200 Pennsylvania Ave., Washington, DC. 20460
mtbe.advisory@epa.gov
(202)260-5374
For Further Information on the Research
Strategy, Contact:
Diane Ray, U.S. EPA, Office of Research and
Development, NCEA, MD-52, RTP, NC 27711
or by phone (919)541-3637.
To Obtain the Advisory:
Call the National Center for Environmental
Publications and Information (NCEPI) at 1-800-
490-9198 to be sent a copy or write to NCEPI,
EPA Publications Clearinghouse, P.O. Box
42419, Cincinnati, OH 45242 .
Internet download:
www.epa.gov/OST/Tools/MtBEaa.pdf
To Obtain the Research Strategy on
Oxygenates in Water, External Review
Draft, Contact: Diane Ray, U.S. EPA, Office
of Research and Development, NCEA,
MD-52, RTP, NC 27711 or by phone
(919)541-3637.
Internet download:
www.epa.gov/ncea/oxywater.htm
To Obtain the 211 (b) Air-Related Research
Requirements, Contact:
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