Methyl tert-Butyl Ether



Methyl tert-butyl ether (MTBE) is a flammable liquid with a distinctive, disagreeable odor. It is made from blending chemicals such as isobutylene and methanol, and has been used since the 1980s as an additive for unleaded gasolines to achieve more efficient burning.

MTBE is also used to dissolve gallstones. Patients treated in this way have MTBE delivered directly to their gallbladders through special tubes that are surgically inserted.

Structural diagram: National Institutes of Health

Fate & Transport

MTBE quickly evaporates from open containers and surface water, so it is commonly found as a vapor in the air. Small amounts of MTBE may dissolve in water and get into underground water. It remains in underground water for a long time. MTBE may stick to particles in water, which will cause it to eventually settle to the bottom sediment. MTBE may be broken down quickly in the air by sunlight. MTBE does not build up significantly in plants and animals.

Exposure Pathways

Touching the skin or breathing contaminated air while pumping gasoline

Breathing exhaust fumes while driving a car

Breathing air near highways or in cities

Drinking, swimming, or showering in water that has been contaminated with MTBE

Receiving MTBE treatment for gallstones

Health Effects

Breathing small amounts of MTBE for short periods may cause nose and throat irritation. Some people exposed to MTBE while pumping gasoline, driving their cars, or working in gas stations have reported having headaches, nausea, dizziness, and mental confusion. However, the actual levels of exposure in these cases are unknown. In addition, these symptoms may have been caused by exposure to other chemicals.

There is no data on the effects in people of drinking MTBE. Studies with rats and mice suggest that drinking MTBE may cause gastrointestinal irritation, liver and kidney damage, and nervous system effects.

There is no evidence that MTBE causes cancer in humans. One study with rats found that breathing high levels of MTBE for long periods may cause kidney cancer. Another study with mice found that breathing high levels of MTBE for long periods may cause liver cancer.

The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified MTBE as to its carcinogenicity.

MTBE and its breakdown product, butyl alcohol, can be detected in your breath, blood, or urine for up to 1 or 2 days after exposure. These tests aren't available at most doctors' offices, but can be done at special laboratories that have the right equipment. There is no other test specific to determining MTBE exposure.

Information excerpted from:

Toxicological Profile for Methyl tert-Butyl Ether 1996

Agency for Toxic Substances and Disease Registry
U.S. Dept. of Health and Human Services