MTBE Summary of Facts

Department of Natural Resources fact sheet
Department of Natural Resources Director: Carol S. Comer

What is MTBE?
MTBE stands for methyl tertiary butyl ether. It is commonly used as a gasoline additive to reduce engine knocks. MTBE is being tested to see if it causes cancer or other health problems. The U. S. Environmental Protection Agency is working to reduce the use of MTBE as a gasoline additive as a result of the taste and odor problems in water and unreasonable risk to the environment.

What is the concern about MTBE?
It’s showing up in groundwater all over the country, and it’s tough to clean up.

Is MTBE still in gasoline in Missouri?
No. A law effectively banning MTBE in Missouri’s gasoline supply was passed in 2002. A phase-out was concluded July 1, 2005.

MTBE and Missouri’s Water
How did MTBE get into drinking water?
MTBE can enter the water through gasoline spills, gasoline storage tank leaks, or discharges from two-cycle engines on motorboats and other watercraft. It also enters the atmosphere from airborne emissions from vehicles. MTBE travels through groundwater faster than the other components of gasoline. It does not readily break down.

How will I know if I have MTBE in my water?

Public water systems are routinely tested for MTBE and if any were present in your water system, officials would notify you. MTBE has a very unpleasant taste and a strong turpentine-like odor. If you are on a private well you would be able to smell or taste MTBE contamination long before it would get to a harmful level. EPA has set an advisory level of 20 to 40 parts per billion (ppb) based on the ability of people with a sensitive sense of smell being able to detect it in this range.

Who watches over my drinking water?
The Missouri Departments of Health and Senior Services and Natural Resources are responsible for protecting the quality of drinking water in Missouri. The Department of Health and Senior Services assists private well owners by offering routine water analyses to all well owners and special analyses on an as-needed basis. The Department of Natural Resources is responsible for making sure public water supplies are safe. The Department of Natural Resources also regulates well drillers to assure wells are properly constructed and to protect groundwater quality.

What should I do if I have a private well and suspect that it is contaminated?
For routine water sampling, you should first contact your county health department. If you think that your well is contaminated with MTBE, please call the Missouri Department of Health and Senior Services - Bureau of Environmental Epidemiology at 866-628-9891.

What if I get water supplied to me?
The Department of Natural Resources routinely monitors about 2,000 community public drinking water wells for MTBE and over 100 other potentially harmful compounds at least once every three years. Testing for MTBE began in 1995, so there have been several complete rounds of testing on every public well. The 70 public drinking water systems that use surface water are tested annually for MTBE. Your public water supplier will inform you of any problems. Community water systems publish an annual Consumer Confidence Report that lists all detected contaminants.

How big of a problem is MTBE in our water?
MTBE has been detected in 25 public drinking water wells at 16 different sites since the Department of Natural Resources has been testing.

MTBE has also been found in 41 private drinking water wells, bringing the total number of wells in Missouri contaminated by MTBE to 66 at a total of 37 different sites as of October 2009.

The tables list all the contaminated sites, the date when MTBE was first detected and the highest concentration of MTBE measured. Levels higher than about 20 ppb can cause the water to have a bad taste and smell.

Are these the only places that need to be concerned about MTBE?
No, groundwater moves much more slowly than water in streams, thus many pollution problems aren’t found until years after the pollution entered the groundwater. This means that we may find additional sites contaminated with MTBE in the future and it is why the Department of Natural Resources will continue to monitor public wells for MTBE.

How concerned should I be about MTBE contamination?
Most of Missouri’s drinking water supplies come from treated surface water. Wells used for public drinking water supplies in Missouri are constructed to the state’s highest standards. These wells are typically deeper than private wells and sealed more effectively to prevent nearsurface contaminants from entering our drinking water. Private wells drilled since 1987 are also constructed to a higher standard than older wells. Drinking water from older, shallow wells or springs located near gasoline storage or transportation systems are the most likely to be contaminated. Consumers are only at risk if their water is contaminated.

How many gasoline storage tanks are there in Missouri?
There are nearly 10,000 underground storage tanks in use in Missouri and 31,182 tanks have been permanently closed in the last two decades. The Department of Natural Resources’ goal is to inspect each of the active tanks in use approximately once every three years.

What is being done to check on underground tanks?
When a gasoline storage tank leaks, many harmful chemicals can flow into the groundwater. This has led Missouri to require new safety measures and to inspect all tanks. All underground tank operators must monitor their tanks and piping monthly. The records they keep are reviewed by department staff and staff of the Petroleum Storage Tank Insurance Fund. All tanks in use after Dec. 22, 1998, must meet strict design and operating requirements.

What about above ground tanks?
Aboveground tank owners are required to meet safety and fire requirements. This includes having leak and spill prevention equipment. The Missouri Department of Agriculture inspects aboveground fuel storage and dispensing systems. Some of the aboveground tanks are also insured by the Petroleum Storage Tank Insurance Fund, which also makes sure the owner has
a current spill prevention plan.

MTBE and Human Health
How much MTBE is bad for me?

EPA sets health-based, legally enforceable drinking water standards called Maximum Contaminant Levels for potential drinking water contaminants. MTBE does not currently have a Maximum Contaminant Level, but it is on EPA’s Contaminant Candidate List and is being considered for regulation in the future. In lieu of a Maximum Contaminant Level, Missouri’s Department of Health and Senior Services has recommended three action levels for MTBE based on the latest risk assessment information. The first action level is a long-term, or lifetime number, which would be equivalent to a Maximum Contaminant Level and it is 20 ppb. A second action level, which would be protective of shorter-term exposures, is 400 ppb. This action level is designed to set a limit on the amount of exposure that a community public water supply could receive from MTBE while obtaining an alternate water supply. The third action level is an acute one where the water would not be considered safe to drink, even for a short period of time. The acute action level is 1,000 ppb.

It is important to know that MTBE has a strong taste and odor that make it unlikely that you would drink enough MTBE to make yourself seriously ill. EPA’s Human Health and Criteria Division has recommended keeping contamination below the 20 to 40 ppb range to ensure that your water does not have a bad taste and odor. Levels much higher than this advisory range quickly become unacceptable to the public. EPA estimates that concentrations from 20,000 to 100,000 times higher than this are associated with illness or disease in rodent studies.

How much do we know about MTBE’s health effects?
Rats and mice have been given MTBE internally and forced to breathe air rich in MTBE. Some of these animals got sick or developed cancers, apparently as a result of their exposure to high concentrations of MTBE. Few tests have been conducted on humans, and none of these studied the effects of drinking MTBE. Because MTBE is mixed with other harmful chemicals, it has been difficult to study its effects on humans. MTBE is thought to cause cancer based on the animal studies, but only at concentrations far above those likely to be found in humans because of MTBE’s offensive taste and smell.

How much of a risk is gasoline?
A federal government study concluded that other components of gasoline pose much more serious cancer risks than MTBE. Benzene, a component of all gasoline, is known to cause cancer at levels much lower than the likely exposure of anyone to MTBE. In addition, gasoline contains other compounds known to pose health risks at high concentrations.

What can I do?
Handle all petroleum products carefully and never pour them on the ground. Make sure that your well is properly constructed and never dump anything on the ground near your well. If you are on a public water system, read the annual Consumer Confidence Report that is made available each year describing the quality of your water. If your water smells or tastes of turpentine or has some other unusual smell or taste, contact your local water supplier. For private well owners, please call the Missouri Department of Health and Senior Services at 866-628-9891.

Where can I get more information?
For more information about MTBE call or write:
Missouri Department of Natural Resources
P.O. Box 176
Jefferson City, MO 65102 0176
800-361 4827

What programs deal with drinking water quality in Missouri?

Missouri Department of Natural Resources’ Public Drinking Water Branch
Helps ensure the safety of public drinking water by routinely monitoring over 100 chemicals and bacteria that can cause illness.

Missouri Department of Natural Resources’ Environmental Services Program
Conducts field sampling and laboratory tests on Missouri’s water and air. Responds to emergencies involving hazardous chemicals.

Missouri Department of Natural Resources’ Hazardous Waste - Underground Storage Tanks Section
Helps prevent contamination caused by corrosion, leaks, overfilling and spills from underground storage tanks.

Missouri Department of Natural Resources’ Geological Survey Wellhead Protection Section
Protects the groundwater from contamination by ensuring that all private wells are built to state standards.

Missouri Department of Health and Senior Services - Environmental Epidemiology

Missouri Department of Agriculture – Petroleum Quality and Inspection Program
Assures that all motor fuels and other fuels meet minimum quality specifications.

Petroleum Storage Tank Insurance Fund
Provides pollution liability insurance to owners and operators of underground and aboveground tanks and pays to clean up old tank sites.