1990, the federal Clean Air Act was passed to improve air quality in the United States. President Bush’s proposed amendments to the Clean Air Act initially would have led to the introduction of alternative, non-petroleum fuels. The petroleum and oxygenate industries responded by offering a reformulated gasoline program as a substitute for most of the alternate fuel proposals. As a result, the amendments to the federal Clean Air Act adopted in 1990 required steps to achieve lower vehicle emissions, including programs to oxygenate and reformulate gasoline. Oxygenated gasoline is designed to increase the combustion efficiency of gasoline, thereby reducing carbon monoxide emissions. Since January 1995, the 1990 Clean Air Act Amendments require areas that have the most severe ozone pollution to use reformulated gasoline containing fuel oxygenates to improve air quality.
Methyl Tertiary Butyl Ether is one of the most commonly used fuel oxygenates because it is produced in very large amounts from isobutylene, a waste product in the refining process. MTBE can be easily produced at the refinery, at a low cost, and can be transferred through existing pipelines once it has been blended with gasoline. In contrast to other gasoline additives used in the past, MTBE is a member of a class of chemical compounds, ethers, whose unique properties are enhanced solubility in water and chemical attraction to water molecules.
These properties, along with widespread use of MTBE, have resulted in frequent detection of MTBE in samples of shallow groundwater from urban areas throughout the United States. MTBE moves quickly to shallow groundwater because it is not attached to soil particles, and is chemically attracted to water molecules. MTBE the potential to impact regional groundwater sources and may present a cumulative contamination hazard due to its mobility and apparent recalcitrance. The United States Geological Survey, in a paper presented to the American Chemical Society in San Francisco in April 1997, noted that MTBE can move from shallow to deeper aquifers with time. MTBE enters the environment, and eventually the groundwater, mainly from leaking underground fuel tanks and associated piping, but also from incomplete combustion in internal combustion engines, spilling and evaporation during transportation and refueling, and watercraft exhaust. Atmospheric precipitation may be another potential source of MTBE in groundwater, because MTBE percolates easily through soil due to its small molecular size and solubility in water, allowing it to move rapidly into groundwater.
The Environmental Protection Agency has classified MTBE as a possible human carcinogen, but no drinking-water regulation has been established for the compound. The Environmental Protection Agency has issued a drinking water advisory of 20- 40 micrograms per liter, based upon odor and taste thresholds, and to provide a large margin of safety from carcinogenic effects. Since February 1997, the California Department of Health Services has required public water suppliers to monitor their drinking water sources for MTBE. As of December 1997, about 23%of drinking water sources in California had been sampled for MTBE contamination. Of those sites tested, 33 or 1.3%, had detectable levels of MTBE. Of the contaminated sites tested, 36% had MTBE levels above the state’s proposed drinking water standard.
Some water systems only test every three years for volatile organic compounds, such as MTBE, so it will be the end of 2000 before all systems will have been tested. For MTBE, this frequency of impact to public drinking wells may not be a reliable indicator of future trends because it reflects a history of releases, including those involving gasoline formulations containing no or only low volumes of MTBE. It also appears that dissolved benzene plumes were of larger regulatory concern than MTBE in previous studies.
Most studies have indicated that MTBE does not biodegrade easily under various environmental conditions. If a research investigation determines that a compound does not degrade, a half-life is not reported and the compound is classified as recalcitrant. MTBE is generally reported as recalcitrant, and there are no widely accepted estimates of the half-life. Investigators have reported that MTBE is recalcitrant in anaerobic laboratory studies including denitrifying conditions, sulfate-reducing conditions, methanogenic-reducing conditions, and anaerobic conditions in landfill-affected aquifer material, soils, and sludges. One 1995 result indicated there was no degradation of MTBE in an aerobic laboratory study after more than 100 days of incubation.
Degradation of MTBE has been reported on occasion and this indicates that some microorganisms are able to degrade MTBE. Resent research has demonstrated that bacterial populations and certain pure bacterial strains, when isolated from biotreated sludges and other sources, have the ability to use MTBE as a sole carbon source. Engineers in the laboratory of Marc Deshusses, an assistant professor of chemical engineering at University of California at Riverside, are studying how microorganisms with an affinity for MTBE degrade the additive under various conditions. They found the biodegradation rate of MTBE in both laboratory flasks and bioreactors was greatly improved by adding trace amounts of peat humic substances, large organic molecules that can be extracted from peat. The substances seem to stimulate the microbes, but scientists do not yet know how.
There are no studies of effects on humans of long term exposure to MTBE. Studies used to determine the hazards have been done with laboratory animals, which creates many limitations and uncertainty. Animal tests performed in 1997 were not conducted by exposing animals to MTBE in drinking water, but rather by introducing oil containing MTBE directly into their stomachs several times a week. The Environmental Protection Agency determined, although useful for identifying potential hazards, limitations of the reported studies do not allow confident estimates of the degree of risk MTBE may pose to humans from low-level drinking water contamination.
In 1997, the California Legislature addressed several issues surrounding MTBE. Four bills passed the Legislature and were signed by Governor Wilson. These bills included SB 521, which paid University of California to determine the risks and benefits of MTBE to human health and the environment, and required the governor to take appropriate action once these determinations were made about the safety of MTBE. SB 1189 required the Department of Health Services to set primary and secondary standards for drinking water, and require public notification if contamination occurs. AB 592 required several actions related to the contamination and clean up of groundwater by MTBE, and the funds to reimburse owners of contaminated drinking sources. AB 1491 prohibited delivery of gasoline to any underground fuel storage tank not in compliance with state and federal standards after January 1, 1999. As a result, Governor Gray Davis ordered MTBE to be banned in California by December 2002.
Many water suppliers now want to blame the oil industry for the contamination of their drinking water. On June 20, 2000, the city of Santa Monica, Ca filed a lawsuit against 18 oil companies for 200 million dollars for the estimated costs of cleanup of the cities polluted drinking water wells. In November 1997, Mr. Bordvick of the Tosco Corporation testified at a public hearing of the Assembly of Natural Resources Committee that Tosco’s position was in support of the ban of MTBE because of concern of the potential liability the company would face if MTBE contaminated drinking water. Several months earlier, a U.S. District Court in Wilmington, North Carolina, awarded 9.5 million dollars to the 178 residents of a mobile home park because MTBE had contaminated their drinking well.
Although it was known that MTBE was a menace in the 1980’s, the petroleum and oxygenate industries knew that MTBE was the only hope of achieving the requirements of the Clean Air Act. Non-petroleum fuels are the future of this planet, yet these companies are stubbornly resisting to accept the fate of our future.