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MTBE: A Health Hazard You Can Do Something About

by Marina Michaels

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Table of Contents

The Problem

I no longer buy gasoline anywhere but at 76, because 76 is the only gasoline company in the state of California that has finally (though reluctantly and with legal force) stopped manufacturing gasoline with the deadly additive, MTBE (methyl tertiary-butyl ether). (Other oil companies are on their way; they are all making this change because the law is forcing them to, though they fought long and hard for the privilege of continuing to use MTBE. Watch for them all, one by one, to make a virtue of finally being forced to stop polluting of the planet.)

For those who aren't aware of it yet, MTBE is in almost every gallon of gas you buy in California (and many other states, though some have legislated against it now). It is supposed to reduce exhaust emissions to meet Federal air quality requirements, yet it doesn't even do what it is supposed to do.

Aside from its ineffectiveness, what makes it so bad?

  1. It is a solvent (a volatile organic compound—VOC) that is a human and environmental health hazard.
  2. Practically no storage tank can hold it, so that it leaks readily into the ground, contaminating both the ground and our ground water.
  3. It is easily airborne, so that it also contaminates the air.
  4. It does not biodegrade readily.

To quote from a document published by the American Petroleum Institute, "...many fuel oxygenates are more mobile and persistent in groundwater than BTEX or other petroleum hydrocarbons. ... for example, a small surface release of conventional fuel may have no apparent impact on shallow groundwater, while an equivalent release of oxygenated fuel may result in unacceptable concentrations of dissolved-phase MTBE." (BTEX stands for benzene, toluene, ethybenzene, and xylenes, all of which are pretty toxic chemicals themselves.) According to this paper, when MTBE does degrade, it turns into other compounds that are also toxic.

From the transcripts of the California public hearings on MTBE held in February, 1999, one finds that a University of California, Berkeley study on MTBE concluded without question that MTBE causes asthma in humans; that it poses a certain cancer hazard to humans; and that it was known to be in, at the time of the hearings, 3,000 to 6,000 sites

that are impacting groundwater and the plumes are moving faster than anything we've seen in connection with fuel tank sites before MTBE. I think it's a significant problem, and the models show that the number of impacted sites is going to increase with time. ... Remediation is difficult. Lots of money will be spent on trying to contain them, but we expect those will be problems for years to decades to come, so those sites are not going to go away any time soon. We know that even the upgraded tanks have a significant probability of continuing to leak. The jury is still out to some agree on whether the upgrade program is really going to curtail future leaks, so we anticipate that even with the upgraded tanks, there's going to be a finite number of new leaking tank cases per year. I think you just have to weigh the additional burden of that on the already overloaded leaking tank regulatory staff, which was essentially overwhelmed even before MTBE was in the gasoline product. (, pages 52-53)

Why do refineries use it? Because it is makes them lots more money. They can severely pollute the ground, air, and water, and they are paid for doing so. And don't expect the EPA to do anything about it—they are moving with glacial slowness toward issuing "standards" many years too late—long after the horses have not only left the barn, but have been slaughtered and eaten by the wolves. The EPA thinks that it is acceptable to allow a certain amount of MTBE in our soil and water, even though even those standards are unenforceable. (See page 2-7 (page 19) of

Yet "the Environmental Protection Agency seems to be confusing Reformulated Gasoline with Reformulated Gasoline containing MTBE. ... In addition, there seems to be a strong emphasis on air and a much lesser emphasis on water, at least in the covering letter that comes with the document, and I find that surprising, especially from an Agency that is supposed to be worrying about both." (, pages 12-13)

Further testimony stated that the "EPA ... ignored its own research [revealing the hazards of MTBE] that was published in the Federal Register" (, page 13).

The ultimate scam with MTBE is that it doesn't even work. Oxygenated fuel might produce fewer emissions per gallon, but the problem is that they reduce the miles-per-gallon of your vehicle so severely that you end up buying far more gallons of fuel, so that you are in effect putting just the same amount of pollutants into the air anyway. I am not the only one who noticed the drastic drop in my gasoline mileage when oxygenated fuels were introduced in California. Where I used to be able to go nearly 500 miles on a tank of gas (with my car at the time), I started to feel lucky to get 390 miles out of a tank. And that was with a very energy-efficient vehicle. From the MTBE hearing, again, we find that "there is little or no beneficial effect of the added oxygenates, including MTBE, on air quality, on emissions from most cars in California." (, page 9) Yet the EPA is still denying Governor Davis's request for a waiver from the Federal requirements for oxygenated fuel. (

And MTBE is expensive, not just to the environment and human health, but to the corporations that use it. On August 6, 2002, Shell Oil agreed to pay $28 million to restore drinking-water wells polluted by leaking gas stations on the south shore of Lake Tahoe. (

More on MBTE

Here is a more in-depth description of MTBE:

MTBE, or methyl tertiary butyl ether, has contaminated groundwater and surface water sources in nearly every region of the state and is considered a possible human carcinogen. It is highly soluble in water, does not readily degrade in the environment, and most public water systems are not equipped to completely remove it from drinking water.

Public drinking water wells have been closed due to MTBE contamination or the threat of contamination in Santa Monica, San Jose, South Lake Tahoe, Sacramento, Cambria, Temecula, Kern County and Ventura County and other locations. In addition, varying levels of MTBE detected at reservoirs around the state has forced many water agencies to restrict motorized recreation to reduce the release of MTBE from two-stroke marine engines.

A 1998 study by the Lawrence Livermore National Laboratory estimated that MTBE had contaminated groundwater at over 10,000 shallow monitoring sites in California. That number is likely to be higher today, and water suppliers fear that more drinking water sources will be affected if contamination moves from shallow groundwater to deeper aquifers.

According to data compiled by the California Department of Health Services, MTBE has been detected in 85 drinking water sources in California to date. That number includes 54 groundwater sources and 31 surface water sources. Not reflected in the DHS database, however, is the number of wells taken out of service due to the threat of contamination. A recent example is Ventura County, where 16 drinking water wells are within 1,000 feet of two distinct MTBE plumes. At least four of the wells have been removed from service.

A Legacy of Contamination

Despite regulations that required underground storage tanks to be upgraded by the end of 1998, there is evidence MTBE continues to leak into soil and groundwater. Preliminary results of a new state study found that as many as two-thirds of the upgraded tanks and piping systems tested in two counties are leaking MTBE.

Because MTBE does not significantly degrade once it is in groundwater, the problem will not go away anytime soon. Experts believe that even if MTBE were taken out of gasoline tomorrow, existing contamination would continue to threaten drinking water sources for several years to come.

There is currently no cost-effective treatment technology available to remove MTBE from drinking water. Experts believe treatment costs could exceed $1 million per drinking water well. The University of California has further estimated that MTBE treatment costs could climb as high as $1.5 billion.


What Can You Do?

Additional Links on MTBE

For some information on MTBE, see

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