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PUBLIC HEALTH STATEMENT 

METHYL-TERT-BUTYL ETHER 

CAS#: 1634-04-4 

Division of Toxicology August 1996 

This Public Health Statement is the summary 

chapter from the Toxicological Profile for Methyltert-butyl Ether . It is one in a series of Public 

Health Statements about hazardous substances and 

their health effects. A shorter version, the 

ToxFAQsTM, 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. 

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. 

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. 

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 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

METHYL-TERT-BUTYL ETHER 

CAS#: 1634-04-4 

Division of Toxicology August 1996 

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. 

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. 

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. 

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 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

METHYL-TERT-BUTYL ETHER 

CAS#: 1634-04-4 

Division of Toxicology August 1996 

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. 

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 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov 
 

 

 

 

 

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PUBLIC HEALTH STATEMENT 

METHYL-TERT-BUTYL ETHER 

CAS#: 1634-04-4 

Division of Toxicology August 1996 

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. 

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. 

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 

Reference 

Agency for Toxic Substances and Disease Registry 

(ATSDR). 1996. Toxicological profile for methyl tbutyl ether. Atlanta, GA: U.S. Department of Health 

and Human Services, Public Health Service. 

DEPARTMENT of HEALTH AND HUMAN SERVICES, Public Health Service
 

Agency for Toxic Substances and Disease Registry 

www.atsdr.cdc.gov/ Telephone: 1-888-422-8737 Fax: 770-488-4178 E-Mail: atsdric@cdc.gov