Can We Be MTBE Free?

For years studies have shown the dangers of this once popular gasoline additive; now some in California and other parts of the nation might be taking the warnings to heart

Methyl Tertiary Butyl Ether (MTBE) is a gasoline additive used to oxygenate and add octane to gasoline. Since the late 1970s, lead has been banned from use in automobile fuel use due to its toxicity to humans, leading to the problem of low oxygenation in gasoline that has caused exhaust to be more easily trapped in urban airsheds.

Several additives have been used to reformulate, and as a gasoline oxygenate, with MTBE being the most used. However, the use of MTBE also poses some problems.

The use of gasoline additives has proved successful in preventing air pollution; at the same time, it has advanced problems concerning water contamination. The detection of even small amounts of MTBE in a potable watershed can necessitate its closing due to the unpleasant smell and taste, as well as the potential carcinogenic effects of the additive.

The Easy Way is Not Always the Best
MTBE is the most used gasoline additive for many reasons. It is easily produced with gasoline at the refinery and blends easily with gasoline without separating from it. Most importantly, MTBE can be shipped using the existing pipeline that gasoline uses. The use of current pipelines implies the greatest ease of transportation of the additive, requiring no modifications to the infrastructure of either the way in which MTBE is shipped, or the way in which automobile engines are built. Because of this, the production of MTBE makes a small percentage of profit, which many oil companies claim helps drive the oil economy.

Unlike most components of gasoline, MTBE is able to travel at nearly the same velocity as water through an aquifer, which leads to a larger plume of MTBE and a larger area that can become contaminated. Because the solubility of MTBE is so high (4.8 percent at 20 degrees Celsius) and because MTBE is able to move from a liquid to a vapor form as it follows the pressure gradient, it is possible for MTBE to be introduced into the environment with precipitation. Also, because MTBE is highly resistant to biodegradation, it is expensive and in a large part unsuccessful for remediation efforts to remove it from the environment. As difficult as it is to remediate MTBE, there are several ways for it to enter the environment:

  • Underground storage tanks (UST). There are an estimated 760,000 USTs in use for petroleum storage. In California alone, the minimum number of MTBE point sources from leaking UST is estimated at more than 10,000.
  • Aboveground storage tanks (AST). Approximately 444,000 facilities with ASTs are located so as to be expected to discharge oil to surface waters or adjoining shorelines.
  • Pipelines. An average of 29 gasoline spills occur annually from pipelines with a volume of 1.03 million gallons per year.
  • Watercraft. Two stroke engines used on some personal watercraft can discharge as much as 30 percent of each gallon of fuel used.
  • Stormwater runoff. Residues of gasoline that wash off the road after a rainstorm.
  • Other releases. Automobile accidents, tank truck spills, etc.

The U.S. Environmental Protection Agency (EPA) non-regulatory standard for MTBE stands between 20 micrograms per liter to 40 micrograms per liter. Though the reason MTBE is so effective at closing water supplies is that it is detectable by humans in much lower quantities and gives water a foul turpentine-like odor and taste. The state of California has established a secondary standard of five micrograms per liter to ensure the potability of water.

Bringing the Dangers to Light
MTBE follows a pressure gradient in determining what form it will be. It can exist as either a gas or a liquid, though it is interchangeable between the two through volatilization and condensation. Based on a study completed in 1995, high doses of MTBE by inhalation over a two-year period have caused non-cancer health problems, as well as tumors in two strains of rats and one strain of mouse. There were carcinogenic effects with high doses when administered in a liquid form as well, which led MTBE to be classified as a possible human carcinogen under the 1986 cancer risk assessment guidelines. In a report to the governor and the legislature of the State of California dated November 1998, the conclusion was made that MTBE is an animal carcinogen with potential to cause cancers in humans. Additionally, in a report of the White House National Science and Technology Council, the council concluded that there is sufficient evidence that MTBE is an animal carcinogen. The evidence also supports that MTBE is a carcinogenic hazard for humans.

More evidence of MTBE health dangers was presented in a report aired Jan, 17, 2000, on the CBS television program 60 Minutes. In the program, Dr. Nachman Brautbar, PhD, a clinical professor of medicine at the University of Southern California School of Medicine, and Dr. Aristo Vojdani, PhD, an associate professor at the Charles Drew School of Medicine in Los Angeles, reported the results of their study of a community of 300 patients who were exposed to both MTBE and benzene in drinking water for more than five years. Dr. Brautbar reported that water wells had been contaminated from a ruptured gasoline storage tank located in a nearby gasoline station. "These patients had headaches, skin rashes, sinus congestion, diarrhea and memory loss that was not present before they were exposed to the two gas additives. It is significant that the health problems only occurred after exposure to MTBE and benzene," Dr. Brautbar said.

Dr. Brautbar and Dr. Vojdani's study made four findings:

  • A significant number of the patients developed specific MTBE antibodies, indicating an immunological reaction.
  • Patient's white blood cell counts were abnormal and included increased cell death.
  • This defect is believed to play a role in cancer production; and
  • Eighty-seven percent of the patients exposed and tested showed cell cycles.

In another a study, entitled "Methyl Tertiary-Butyl Ether Antibodies among Gasoline Service Station Attendants," published in December 1997 in the Annals of the New York Academy of Sciences, Dr. Brautbar, Dr. Vojdani and Dr. Galal Namatalla, a dermatologist, reported that elevated levels of MTBE antibodies were found among gas attendants. The research compared 24 adults employed for more than two years in gas stations with a control group of 12 adults who rarely came into direct contact with fuel.

Seven individuals from the first group exhibited antibody levels of a three-fold to 15-fold elevation when compared with the antibody levels against MTBE in the control group.

"What this means is that they the gas attendants were exposed to MTBE at some time," said Dr. Brautbar. He also indicated that he has seen 450 patients with MTBE-related health problems, which are appearing throughout the country. This report can be found at

Additionally, when the Clean Air Act (CAA) was passed in 1990, a mandate was established for use of oxygenates to reduce smog, and MTBE came into widespread use in California, Texas and several eastern states. Other states, such as Oregon, Washington, Montana and Minnesota adopted ethanol, an alternative oxygenate that is derived from corn. MTBE was tried, but rejected by several states, including Alaska and North Carolina, after residents there developed health problems.

Cleaning Up the Problems
The potential carcinogenic effect that occurs from the liquid form of MTBE explains why groundwater contamination may prove to be so detrimental to the health of humans. As MTBE occurs most commonly in its liquid form and travels easily through aquifers, the potential to receive a lethal dose of MTBE from a major spill is plausible. In addition, asthma and respiratory illness also have been linked with MTBE exposure, as well as rashes and skin problems from contact.

Approximately nine billion gallons of fuel are released into the environment each year with MTBE present in a large number of those spills. The danger of contamination is highest in areas that are required by federal government guidelines to participate in winter oxy-fuel programs. MTBE is detected five times more frequently in such areas. These are areas that do not meet the requirement of the Clean Air Act.

Eighty-three percent of gasoline releases contained MTBE with 43 percent containing concentrations greater than 1000 micrograms per liter, according to a 1998 industry survey. This is a widespread problem that has moved EPA to try to ban MTBE all together as a fuel oxygenate. This total ban may prevent future leaks, but problems are still present for the remediation of current spill sites.

Two of the more commonly used techniques for the remediation of MTBE are:

  • Air stripping. In air stripping, contaminated groundwater is passed through an aeration tower, which collects the contaminants that can be converted into solid form and disposed. This treatment works best with higher air to water ratios, or where higher temperatures are used than most volatile compounds would require.
  • Granular activated carbon (GAC). GAC requires water to be passed through one or more beds of carbon, causing the contaminant to be adsorbed onto the carbon. The relatively low adsorption rate of MTBE means that more GAC must be used, driving up the cost of remediation. Therefore, MTBE is difficult and costly to remediate.

In addition to these, biological agents are used in the remediation of MTBE. This process is gaining popularity as is the use of resins.

Moving Toward a Solution?
The primary focus of remediation and banning efforts are taking place in California. Southern California is an area that has been classified as a winter oxygenate area. Current legislation to ban the use of MTBE as a gasoline additive in California is being studied in cities such as Santa Monica and Glennville, California. When, on March 25, 1999, Governor Gray Davis ordered the removal of MTBE from California gasoline at the earliest possible date, but no later than December 31, 2002, by signing Executive Order D-5-99, he began the process of the elimination of MTBE from California groundwater. He did, however, give an extension to the deadline on March 15, 2002, with a new executive order that gave a one-year extension to MTBE removal. Under the new time line, the MTBE phase-out will be accomplished by Dec. 31, 2003.

There have been numerous lawsuits filed against oil companies in the last decade.

The city of Santa Monica has a claim filed based on the acceptable levels of MTBE contamination in groundwater with the case Western States Petroleum Association et al. vs. Department of Health, June 27, 2002. Communities for a Better Environment, an environmental group in San Francisco, are also taking the oil companies to court with the assistance of attorneys from Texas and North Carolina. Communities for a Better Environment claims oil companies knew that MTBE was dangerous, yet used it anyway.

There have been more contamination cases reported in Virginia, Maine and other states with such cases as Michael A. Millett, Cathy Lemar, Richard Lemar, Victoria Emmons and Monique Leamon vs. Atlantic Richfield Company, Arco Chemical Company, Lyondell Chemical Company, Oxygenate Fuels Association and American Petroleum Institute in Cumberland County Maine on Aug. 30, 1999, and Aviation Oil Company vs. Department of Environmental Protection, which was held in the Supreme Judicial Court of Maine on Dec. 14, 1990. Many of the cases brought to court concern about setting limits on how much MTBE in parts per billion (ppb) should be deemed hazardous to human health.

The Future of MTBE
In addition to MTBE, other octane boosters and oxygenates are coming under scrutiny by regulatory agencies based upon concerns about their potentially negative effect on human health. Tertiary butyl alcohol (TBA), which is used as an octane booster as well as in the formulation of MTBE, is one of these. The strict guidelines to follow upon TBA contact, whether contact with the skin or by inhalation, and the possibility that it is a human carcinogen, should be enough to warrant the strictest handling procedures. Compounded with the fact that the reaction with groundwater is much the same as with MTBE, TBA would seem to warrant as much, if not more, caution than MTBE. With oxygenates and octane boosters that are more safe than TBA, its use may become as limited as MTBE.

While MTBE is in use, problems with contamination will continue to occur in groundwater. The continued use of MTBE as a gasoline additive will continue the current problems that are being discovered in both humans and other animals. MTBE has been classified as a carcinogen in animals and is suspected as a carcinogen in humans. Also the non-cancer effects are sure to be problematic with the continued use of MTBE in gasoline. It is probable that future legislation throughout the country will eliminate the use of MTBE as a gasoline additive and octane booster. With the availability of alternative oxygenates available the continued use of MTBE is in question.


This article originally appeared in the 05/01/2003 issue of Environmental Protection.

About the Author

Aaron Jensen is a freelance writer who is currently who has a bachelor of science degree in environmental studies from the University of Utah, Salt Lake City. He can be reached at (801) 671-5950.

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