Researchers Closing In On Potential Microbial Solution for MTBE-Contaminated Groundwater

MTBE, or methyl tertiary butyl ether, is a gasoline additive which has been used since 1979. It was originally used to help gasoline burn more smoothly and efficiently after lead was phased out as an additive. At room temperature, MTBE is a volatile, flammable, and colorless liquid that is more soluble in water than most other gasoline components.

Starting in 1992, oil companies started adding MTBE to gasoline to improve combustion and decrease harmful carbon monoxide emissions from motor vehicles, especially in the winter months. The goal was to improve the air quality in urban areas and to help cities meet Clean Air Act standards.

Exposure to MTBE can occur when pumping gasoline, living near bulk gasoline loading and unloading facilities or near facilities that can leak gasoline from underground or above-ground storage containers thereby contaminating drinking water.

In most of these situations, the most important form of exposure is the inhalation of MTBE-contaminated air. However, it is also absorbed through the contact with the skin. Contamination of the groundwater near storage facilities can also result in exposure from the tap water.

Other sources of MTBE in the environment (and potentially into drinking water sources) are associated with gasoline spillage when fuel is transported or transferred, leaking gasoline pipelines, spills at gas stations, automobile accidents where fuel tanks are ruptured, improper disposal of “old” gasoline, and emissions from older and inefficient two-stroke marine engines.

Drinking water in at least 1,800 water systems in 29 states is contaminated to some degree by MTBE.

In a news release on July 11, 2005, the Environmental working Group (EWG) announced ( that a draft risk assessment by the Environmental Protection Agency (EPA) contained language linking “MTBE to cancers such as leukemia and lymphoma.”

Although this would represent a significant shift in the EPA’s position, the draft has been circulating within the agency for review purposes for over a year. It must still be “signed off on” by all EPA divisions and “go through external review.” EWG states that people within the EPA “have been trying to get this out of the agency forever.”

Currently, there is a debate in Congress over legislation that would compel the petroleum industry to clean up the problem it created as a result of underground contamination from leaking storage facilities and pipelines. The estimates cost of such a massive cleanup range from $25 billion to as high as $85 billion.

The House of Representatives has passed an energy bill that would prohibit municipalities and water systems from suing MTBE makers for “knowingly manufacturing and distributing a defective product.” This is despite evidence that the oil industry already knew in 1979 that MTBE was a threat to water supplies.

EWG President, Ken Cook, observed: “We knew the idea to exempt MTBE makers from lawsuits was bad news for taxpayers. Now EPA is learning how dangerous it would be for public health. No matter how the risk assessment finally comes out, this is clearly not the time to be letting the makers of this chemical off the hook.”

Although MTBE is slowly being banned – 25 states have passed laws to ban its future use and 7 others considering its prohibition – experts in the fields of biodegradation and bioremediation warn that the chemical will remain in groundwater for centuries.

As a result, scientists have been searching for a method of effectively cleansing the environment of this deadly toxin. The most promising work appears to be that of Max Haggblom, a professor in the department of biochemistry and microbiology at Rutgers, The State University of New Jersey, and the Biotechnology Center for Agriculture and the Environment on Rutgers’ Cook College campus.

Prof. Haggblom and his team have discovered that anaerobic bacteria feed on MTBE. Since these bacteria exist in oxygen-free environments, they would be able to attack MTBE underground where it contaminates groundwater sources throughout the U.S.

In a recent paper published in Applied and Environmental Microbiology, the researchers discussed their efforts to identify the specific (one or more) bacteria that feed on gasoline hydrocarbons and MTBE. Currently, a group of about twelve types of bacteria are in the mix and it is not clear whether one or several are consuming the toxin.

In addition to identifying the bacterium or bacteria involved, the researchers must also find a way to greatly accelerate the feeding process since, in its natural state, it is extremely slow.

According to Haggblom, however, they are applying for a patent on a technique that involves “some tricks to actually speed it up, one of which is adding a relatively innocuous natural substance that appears to stimulate the process.” If it can be perfected and replicated on a large scale, anaerobes may someday provide a workable means of bioremediation of  MTBE-contaminated groundwater.    

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