MTBE reductions imminent as EPA panel confirms the chemical improves air but pollutes water

An EPA panel has found that the use of MTBE, an oxygenate used in lower-emission gasoline blends, causes significant pollution to ground and surface water. Despite its proven success in the area of air quality, the Blue Ribbon Panel on Oxygenates in Gasoline has recommended that MTBE use be reduced substantially - with action by the EPA "to ensure that there is no loss of current air quality benefits".


MTBE – or methyl tertiary butyl ether – has been a key component of the Federal Reformulated Gasoline (RFG) Program, in place since 1995. The chemical has been added to gasoline by oil refiners since the 1970s, but its use has risen sharply since 1995. RFG is used in smog-prone areas such as California and states in the north east. Currently, all RFG must contain 2% oxygen by weight with the most commonly-used oxygenate – in 85% of RFG – being MTBE. Ethanol, produced from corn, is used in 8% of RFG.

MTBE causes cancer in animals. The Blue Ribbon panel confirmed that there have been “growing detections of MTBE in drinking water, with between 5% and 10% of drinking water supplies in high oxygenate use areas showing at least detectable amounts of MTBE”. MTBE can be detected by taste and odour. In many instances, consumer detection has led water suppliers to stop using certain water supplies or to undertake treatments to tackle the problem. The panel is also concerned about MTBE contamination of private wells and surface water contamination from watercraft.

In addition to recommending reduction in MTBE use, the EPA panel has suggested that:

  • Congress remove the 2% oxygen requirement in RFG
  • Research and monitoring programmes be established to identify the extent of MTBE contamination as well as comparative studies to identify levels of MTBE, ethanol, benzene and other gasoline compounds
  • Improvements be made to the safety and monitoring of gasoline storage tanks, particularly in areas using RFG that contains MTBE

The expected reduction in MTBE use could result in increasing dependence on ethanol, especially if Congress fails to remove the 2% oxygen requirement for RFG. Several oil refiners have stated that they are able to produce RFG without oxygenates (including ethanol) that meet Clean Air Act standards, but reports have suggested that the use of ethanol may continue to be encouraged in order to assist America’s corn farmers.

EPA’s administrator, Carol Browner welcomed the panel’s findings and stated that the Agency will act to reduce MTBE use.

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