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MTBE in Well Water

What is MTBE?

MTBE (Methyl Tertiary Butyl Ether) was used as a gasoline additive to improve automobile emissions and achieve federal air quality standards. Sources of MTBE in ground water can occur from underground gasoline storage tanks, home heating fuel storage tanks, and improper handling or disposal of gasoline or fuel oil on a property. Once a spill occurs, MTBE travels rapidly in ground water and may affect private wells. MTBE can be detected in well water at low levels and has an unpleasant taste and strong turpentine-like odor. Water quality testing is recommended where private wells are vulnerable to MTBE contamination or where taste and odor problems occur.

How is MTBE measured?

A laboratory test for volatile organic compounds (VOC) is used to measure MTBE levels in well water. The laboratory equipment is capable of measuring MTBE at extremely low levels or in parts per billion (ppb). One part per billion is 1 part in 1,000,000,000. As an example, the measurement of one part per billion of MTBE in ground water is equivalent to one minute in 2,000 years.

What is the drinking water standard for MTBE?

A drinking water standard has not been established for MTBE. In 1997, the U.S. Environmental Protection Agency (EPA) issued a drinking water advisory indicating taste and odor problems may be experienced at levels of 20 to 40 ppb. A value above the drinking water advisory does not indicate that harmful effects will occur, but that taste and odor problems may be experienced and a risk exists that should be evaluated. EPA has placed MTBE on a contaminant candidate list to further evaluate the human health effects and the need for establishing a drinking water standard. There are no regulations that require owners of existing private wells to test or meet the drinking water advisory for MTBE.

How can MTBE affect my health?

MTBE enters the body through breathing and swallowing water contaminated with MTBE. EPA has determined that MTBE has a potential to cause hazardous effects in humans. However, there is no scientific evidence to indicate MTBE is a human carcinogen or a serious health threat. Laboratory studies of animals exposed to high doses of MTBE showed stomach irritation, liver and kidney damage, and nervous system effects. Other studies involving rats and mice breathing high levels of MTBE showed an increased risk of kidney and liver cancer.

What wells are vulnerable to MTBE contamination?

Wells constructed in shallow aquifers (less than 150 feet) and located near gasoline service stations, home heating fuel storage tanks, or where gasoline is used or stored, run the greatest risk of being impacted by MTBE. In some cases, MTBE has traveled distances of up to 1/2 mile in ground water and may affect wells constructed in aquifers greater than 150 feet in depth. For more information on the construction of your well and well depth, contact the Well Construction Water Quality Program staff at 410-222-7398.

Where can I have my well water tested for MTBE?

Water quality testing is recommended where private wells are vulnerable to MTBE contamination or where taste and odor problems occur. Water quality testing may be performed by the Anne Arundel County Department of Health or by a laboratory certified for VOC analysis. A list of certified laboratories can be mailed to you by calling the Well Construction Water Quality Program staff at 410-222-7398 or by sending an e-mail to: Contact Us.

If elevated MTBE levels are found in my well water, what can I do?

The Anne Arundel County Department of Health Well Construction Water Quality Program staff is available at 410-222-7398 to consult with you on water treatment and well replacement options. Well replacement is recommended based on a user's taste and odor threshold or where MTBE levels are found above 20 ppb. The replacement well must meet Department of Health well construction requirements to adequately protect the water supply from MTBE contamination. Activated carbon filter or multi-stage water treatment systems are effective alternatives where MTBE levels are found below 20 ppb. Before choosing a water treatment system, contact the Department of Health or a water treatment company listed under water filtration and purification equipment in the Yellow Pages. The Department does not endorse any brand or company but can advise on which type of water treatment is likely to work. Homeowners using water treatment units to reduce elevated MTBE levels must maintain the unit according to manufacturer's instructions. After installing a water treatment system, a second VOC test is recommended to assure the unit is removing MTBE effectively.

What can I do to protect my well from MTBE contamination?

Never pour, spill or dispose of products such as gasoline, motor oil, diesel fuel, and home heating fuel on the ground or in your septic system. Unused petroleum products must be disposed of properly at an approved hazardous waste collection facility. For more information on County household hazardous waste collection days, visit www.aacounty.org/DPW or contact the Department of Public Works at 410-222-7951. If you have an underground storage tank, consider replacing it with an above ground tank. Leaks and the condition of your tank can be monitored more readily with an above ground storage tank. If tank replacement is too costly, annual inspection of your underground storage tank is recommended. Contact your home heating fuel company to assist with inspection and leak detection of underground storage tanks.

Where can I get more information?

If you have additional questions, please contact:

Well Construction Water Quality Program
Anne Arundel County Department of Health
3 Harry S. Truman Parkway
Annapolis, Maryland 21401
410-222-7398