1.1 What is MTBE? |
1.2 What happens to MTBE when it enters
the environment? |
1.3 How might I be exposed to MTBE? |
1.4 How can MTBE ether enter and leave
my body? |
1.5 How can MTBE affect my health? |
1.6 Is there a medical test to determine
whether I have been exposed to MTBE? |
1.7 What recommendations has the federal
government made to protect human health? |
1.8 Where can I get more information? |
References |
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August 1996 |
Public Health Statement |
for |
Methyl-tert-butyl Ether |
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This Public Health Statement is the
summary chapter from the Toxicological
Profile for methyl-tert-butyl ether . It is one
in a series of Public Health Statements about hazardous substances
and their health effects. A shorter version, the ToxFAQs™,
is also available. This information is important because this
substance may harm you. The effects of exposure to any hazardous
substance depend on the dose, the duration, how you are exposed,
personal traits and habits, and whether other chemicals are
present. For more information, call the ATSDR Information
Center at 1-888-422-8737.
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This public health statement tells you
about methyl tert-butyl ether (MTBE) and the effects of exposure.
The Environmental Protection Agency (EPA)
identifies the most serious hazardous waste sites in the nation.
These sites make up the National Priorities List (NPL) and
are the sites targeted for long-term federal cleanup activities.
MTBE has been found in at least 12 of the 1,430 current or
former NPL sites. However, it’s unknown how many NPL
sites have been evaluated for this substance. As more
sites are evaluated, the sites with MTBE may increase. This
information is important because exposure to this substance
may harm you and because these sites may be sources of exposure.
When a substance is released from a large
area, such as an industrial plant, or from a container, such
as a drum or bottle, it enters the environment. This
release does not always lead to exposure. You are exposed
to a substance only when you come in contact with it.
You may be exposed by breathing, eating, or drinking the substance
or by skin contact.
If you are exposed to MTBE, many factors
determine whether you'll be harmed. These factors include
the dose (how much), the duration (how long), and how you
come in contact with it. You must also consider the
other chemicals you're exposed to and your age, sex, diet,
family traits, lifestyle, and state of health.
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1.1
What is MTBE? |
MTBE is the common name for a synthetic
chemical called methyl tert-butyl ether. It is a flammable
liquid made from combinations of chemicals like isobutylene
and methanol. It has a distinctive odor that most people
find disagreeable. It was first introduced as an additive
for unleaded gasolines in the 1980s to enhance octane ratings.
In city areas where there are concerns over pollutants like
carbon monoxide, EPA may require the use of MTBE or ethanol
as an oxygenating agent to make the fuel burn more cleanly
during the winter months. Fuels containing these additives
are called reformulated gasolines. Most MTBE is mixed
with gasoline, so most people would come in contact with it
while exposed to automobile fuel vapors or exhausts.
MTBE has other special uses as a laboratory chemical and in
medicine to dissolve gallstones.
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1.2
What happens to MTBE when it enters the environment? |
MTBE will quickly evaporate from open
containers. In the open air, it will quickly break down
into other chemical compounds, with half of it disappearing
in about 4 hours. Like most ethers and alcohols, MTBE
dissolves readily in water. If spilled on the ground,
rain water can dissolve MTBE and carry it through the soil
and into groundwater. Spills or leaks from storage containers
can seep into deeper soil layers and pollute groundwater,
especially near manufacturing sites, pipelines, and shipping
facilities. Leakage from underground storage tanks,
such as tanks at gasoline filling stations, can also add MTBE
to groundwater. MTBE is not expected to concentrate
in fish or plants found in lakes, ponds, and rivers.
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1.3
How might I be exposed to MTBE? |
Low levels of MTBE can be present in
both indoor and outdoor air, and are mostly linked with the
use of MTBE as a gasoline additive. Because it is not
presently considered a major harmful pollutant, it is usually
not included in routine national monitoring programs for liquids.
This makes it difficult to estimate how much you could be
exposed to. Because MTBE evaporates quickly, large amounts
of the vapor could enter closed spaces. Leaks, spills,
or open containers of MTBE pose a fire and explosion threat
in the presence of open flames and electrical sparks, especially
in closed spaces. Most people are exposed to MTBE from
auto exhaust when driving or from gasoline while fueling their
cars. People can also be exposed to MTBE from groundwater
pollution. The chemical is likely to be present in very
small amounts in the air in cities or near highways.
MTBE is used to treat gallstones, so patients treated with
this medical procedure will have some exposure.
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1.4
How can MTBE ether enter and leave my body? |
MTBE can enter your body rapidly if you
breathe air, drink water, or eat food that contains it.
If your skin comes into contact with MTBE, it can enter your
body through the skin, but this happens more slowly.
Most of the MTBE that you breathe in or take in by mouth can
get into your blood. Not as much gets into the blood
through the skin. No matter how you are exposed, a large
amount of MTBE is breathed out without being changed into
other chemicals. The MTBE that is not breathed out is
changed into other chemicals such as butyl alcohol, methyl
alcohol, formaldehyde, formic acid, and carbon dioxide.
These chemicals also leave the body quickly in the air that
you breathe out or in the urine. MTBE does not stay
in any organs of your body for a long time. Most of
it and its breakdown products leave the body in 1 or 2 days.
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1.5
How can MTBE affect my health? |
Some people who were exposed to MTBE
while pumping gasoline, driving their cars, or working as
attendants or mechanics at gas stations complained of headaches,
nausea, dizziness, irritation of the nose or throat, and feelings
of spaciness or confusion. These symptoms were reported
when high levels of MTBE were added to gasoline in order to
lower the amount of carbon monoxide, a known poison, released
from cars. MTBE has a very unpleasant odor that most
people can smell before any harmful effects would occur, but
some people might feel irritation of the nose or throat before
noticing the smell. MTBE caused side effects in some
patients who were given MTBE to dissolve gallstones.
The MTBE is given to these patients through special tubes
that are placed into their gallbladders. If MTBE leaks
from the gallbladder into other areas of the body, the patient
can have minor liver damage, a lowering of the amount of white
blood cells, nausea, vomiting, sleepiness, dizziness, and
confusion. These effects are not long-lasting.
We know more about how MTBE affects the
health of animals than the health of humans. Some rats
and mice died after they breathed high amounts of MTBE, but
these levels were much higher than people are likely to be
exposed to. MTBE also caused irritation to the noses
and throats of animals that breathed MTBE. The most
common effect of MTBE in animals is on their nervous systems.
Breathing MTBE at high levels can cause animals to act as
if they are drunk. For example, some became less active,
staggered, fell down, were unable to get up, and had partially
closed eyelids. These effects lasted only for about
an hour, and then the animals seemed normal again. Some
animals that breathed high levels of MTBE for several hours
a day for several weeks gained less weight than normal, probably
because they ate less food while they were inactive.
When rats breathed high levels of MTBE for several hours every
day for two years, some got more serious kidney disease than
these rats usually get as they grow old. Some of the
male rats developed cancer in the kidney, but whether this
has meaning for people is not known. When mice breathed
high levels of MTBE for several hours every day for a year
and a half, some had larger livers than normal, and some mice
developed tumors in the liver. When rats were given
high levels of MTBE by mouth for 2 years, some male rats developed
cancer in the testes and some female rats developed cancer
of the blood (leukemia) and cancer (lymphoma) of some of the
tissues that produce blood cells. The Department of
Health and Human Services (DHSS), the International Agency
for Research on Cancer (IARC), and the EPA have not classified
MTBE for its ability to cause cancer. When pregnant
rats, rabbits, or mice breathed MTBE, birth defects occurred
only in the baby mice. We do not know if this has any
relevance for people. MTBE did not affect the animals'
ability to reproduce.
Some rats and mice died after being given
very large amounts of MTBE by mouth. The amounts were
much higher than people are likely to swallow from drinking
water containing MTBE. The effects on the nervous system
in animals that are given MTBE by mouth are the same as the
effects that occur in animals that breathe MTBE. Some
animals that were given MTBE by mouth had diarrhea and irritation
in their stomachs and intestines. Some animals also
had very slight liver damage.
MTBE irritated the skin of animals when
it was placed directly on their skin. MTBE also irritated
the eyes of animals when it was placed in their eyes or when
air containing MTBE came into contact with their eyes.
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1.6
Is there a medical test to determine whether I have been exposed
to MTBE? |
There are no specific medical tests to
determine whether you have been exposed to MTBE. But
MTBE and its breakdown product, butyl alcohol, can be measured
in exhaled air, in blood, and in urine. Because MTBE
and its breakdown products leave the body in 1 or 2 days,
these measurements can only tell if you have been exposed
recently. The effects of exposure to MTBE, such as stomach
aches, fatigue, and dizziness, are common to many chemicals
and illnesses. These symptoms are not very useful in
determining whether you were exposed to this particular chemical.
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1.7
What recommendations has the federal government made to protect
human health? |
To protect workers, the American Conference
of Governmental Industrial Hygienists (ACGIH) recommends that
the amount in workroom air be limited to 100 parts per million
(ppm) in an 8- to 10-hour work shift. At this time,
governmental agencies such the National Institute for Occupational
Safety and Health (NIOSH), Occupational Safety and Health
Administration (OSHA), and EPA have not established exposure
criteria for MTBE.
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1.8 Where can I get more information? |
If you have any more questions or concerns, please contact
your community or state health or environmental quality department or:
Agency for Toxic Substances and Disease Registry
Division of Toxicology
1600 Clifton Road NE, Mailstop F-32
Atlanta, GA 30333
Information line and technical assistance:
Phone: 888-422-8737
FAX: (770)-488-4178
ATSDR can also tell you the location of occupational and environmental health
clinics. These clinics specialize in recognizing, evaluating, and treating illnesses
resulting from exposure to hazardous substances.
To order toxicological profiles, contact:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Phone: 800-553-6847 or 703-605-6000
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References |
Agency for Toxic Substances and Disease
Registry (ATSDR). 1996. Toxicological
profile for methyl t-butyl ether. Atlanta, GA: U.S. Department
of Health and Human Services, Public Health Service.
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