MTBE is water soluble and decomposes slowly. It is also more difficult to remove MTBE from water. Surface water sources such as lakes and reservoirs are affected by recreational watercraft and elevated levels of MTBE can be detected near marinas. In addition, precipitation can contribute to higher levels of MTBE in surface water where there is MTBE contaminated air. A. MTBE has a turpentine like smell and taste and has been detected by consumers at levels ranging from 15 - 40 ppb.
More sensitive individuals can detect it at even lower levels.
Because MTBE concentration at this level makes water undesirable for human consumption, health officials feel that current advisory levels are well below levels that are likely to cause adverse health effects. The EPA advisory level of 20 - 40 ppb is 20,000 to 100,000 times lower than the range typically seen for carcinogens. There is limited data available to link MTBE exposure in drinking water with serious adverse health effects and short term exposure to high levels of MTBE is unknown. The most common form of exposure, however, is not drinking water but the inhalation of MTBE contaminated air or through MTBE contact with the skin. While not legally enforceable, the advisory is provided as guidance to communities where MTBE may be a problem.