Methyl Tertiary Butyl Ether (MTBE) Summary of Facts - PUB2080

What is MTBE?

MTBE stands for methyl tertiary butyl ether. It was used as a gasoline additive to reduce engine knocks. MTBE is still being evaluated by EPA to determine if it causes cancer or other health problems.  Due to its mobility and persistence, MTBE releases are known to pose a risk to the environment. MTBE is also associated with taste and odor issues in contaminated water, even at very low concentrations. For these reasons MTBE as a gasoline additive was subject to a nationwide phaseout beginning in 2006.

What is the concern about MTBE?

It has been found in groundwater all over the country, and it’s difficult 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. In addition to these state level bans, MTBE was subject to a nationwide phase-out beginning in 2006.

MTBE and Missouri’s Water

How did MTBE get into drinking water?

MTBE contamination can generally be linked to legacy gasoline spills or gasoline storage tank leaks. For many decades, MTBE was also released to the atmosphere through airborne emissions from vehicles. Due to its solubility, MTBE travels through groundwater faster than other components of gasoline. It does not readily break down.

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

The Department of Natural Resources requires that community and nontransient noncommunity (factories, schools, etc. with their own well) public water systems routinely sample for MTBE. Results of this testing should be made available to community water system customers through the water supply’s annual consumer confidence report. 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 producing water that meets all applicable safe drinking water standards. As part of this effort, the Department of Natural Resources also regulates well drillers to ensure wells are properly constructed 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. Significant historical data exists on MTBE levels in Missouri drinking water supplies as these wells have been routinely testing for MTBE since 1995. The 65 public drinking water systems that use surface water are tested annually for MTBE. If MTBE is detected in this routine sampling, community water systems should make results of this testing available to customers through their annual Consumer Confidence Report.

How big of a problem is MTBE in our water?

MTBE has been detected in 16 active public drinking water supplies sites since the Department of Natural Resources has been testing.

MTBE has also been found in private drinking water wells, bringing the number of sites in Missouri contaminated by MTBE to 37.

Are these the only places that need to be concerned about MTBE?

No. Groundwater moves much more slowly than water flowing in streams or rivers, 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 originates 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 near-surface 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 more than 8,000 underground storage tanks in use in Missouri and 34,040 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. Despite this, there was a nationwide phase-out of MTBE as a gasoline additive in the United States beginning in 2006.

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
573-751-6102
info@dhss.mo.gov

Missouri Department of Agriculture – Fuel Quality 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.