M.T.B.E. In The Environment

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Figure 1: From U.S. G.S. Open File- Report 95-456

MTBE in the Environment

 The 1990 Clean Air Act Ammendments require fuel oxygenates to be added to gasoline used in some metropolitan areas. Fuel oxygenates reduce atmospheric concentrations of carbon monoxide or ozone. Methl tert-butyl ether (MTBE) is the most commonly used fuel oxygenate. Currently MTBE is the second most manufactured orgfanic chemical in the United States. Recent developments, however, indicate that the use of MTBE may be creating more problems then it is solving.

What is MTBE

MTBE is an ether that smells like turpentine. It is a volatile, flammable, colorless liquid at room temperature. MTBE has the structural formula of:

and is miscible in gasoline and is soluble in water, alcohol, and other ethers. Additional chemical properties can be reviewed from the EPA Office of Pollution Prevention and Toxics.

Figure 2: MTBE Mass Spectral

MTBE is the most commonly used fuel oxygenate because of its low cost, ease of production and favorable transfer and blending characteristics. It can be produced at existing refineries.

MTBE in the Atmosphere

About 103 million Americans live in counties where MTBE is believed to be used (Figure 3). MTBE is on the Hazardous Air Pollutants List with 189 other chemicals to be regulated under the Air Toxics Program of the 1990 Clean Air Act Amendment. Interestingly, it was this same Clean Air Act which created the significant increase in the use of MTBE. Recently, considerable public attention has been focused on the presence of MTBE in the atmosphere , primarily the potential health risks envolved.

MTBE in Groundwater

MTBE has been detected in groundwater supplies in eight urban areas as part of a study conducted by the United States Geological Survey and recently, MTBE has been detected in groundwater supply wells in Southern California.

MTBE is a potentially important groundwater contaminant. MTBE does not adsorb onto soil organic matter very well, thus, it moves approximately 20% faster than other gasoline constituents. Also, MTBE is persistent in groundwater because it is resistant to biodegradation under aerobic or anaerobic conditions.

Potential Health Effects

Tests have been conducted to evaluate the health risks from exposure to MTBE. The USEPA has tentatively classified MTBE as a possible carcinogen and the draft drinking water lifetime health advisory level is estimated to be within the range of 20 to 200 ug/l.

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