Arizona Governor Janet Napolitano (D) on May 12 signed legislation banning the additive methyl tertiary butyl ether (MTBE) from gasoline sold in the state. The legislation had passed by unanimous votes in the Arizona House and Senate.
“Miracle Additive” Gone Bad
Since 1997, Arizona has relied on MTBE to satisfy the 1990 Clean Air Act amendments, which require oxygenated additives to be blended with gasoline to reduce pollution from vehicle exhaust systems. MTBE initially was billed as a “miracle additive” that would cause gasoline to burn more cleanly. MTBE-treated gasoline costs more than gasoline without the additive, but it gained popularity and market share by virtue of the government’s oxygenate mandate.
MTBE’s star began to fade, however, as leaking underground storage tanks resulted in groundwater contamination in some communities. Studies have suggested high levels of MTBE contamination in drinking water supplies may cause cancer in humans. Although the science behind such claims is still uncertain and the alleged harms largely speculative, juries have begun to assess large financial penalties on gasoline companies for MTBE contamination, and a number of states have taken steps to ban the additive. Arizona was the 18th state to enact such a ban.
“It can be very dangerous in our water,” said Arizona State Rep. Carolyn Allen (R), who sponsored the House legislation. “When they first started using it, there wasn’t an understanding about it getting into the water.”
“The concern about MTBE is widely known,” said Steve Owens, director of the Arizona Department of Environmental Quality. “This is one thing we will not have to worry about again.”
Alternatives Pose Similar Problems
But the state ban on MTBE holds no real promise of ending groundwater contamination. According to a January 2004 study published by researchers at the University of California at Los Angeles, MTBE alternatives pose environmental risks very similar to those presented by MTBE.
“All indications suggest the alternative ether oxygenates would pose groundwater contamination threats similar to MTBE if their scale of usage is expanded,” concluded the study.
“Several other fuel oxygenates with similar properties are present in formulations supplied to gasoline stations,” said Tom Shih, an environmental scientist with the California Environmental Protection Agency and coauthor of the study. “However, unlike MTBE, there is virtually no research on the environmental behavior of these alternative fuel oxygenates.”
Without a better understanding of these chemicals, there is a risk of repeating the MTBE problem, he warned.
The study, which appears in the January 1 issue of Environmental Science & Technology, a peer-reviewed journal of the American Chemical Society, analyzed more than 850 leaking underground fuel tanks in the Los Angeles area. According to the study, the science suggests expanded use of MTBE alternatives may be just as environmentally harmful as was MTBE’s widespread use. Accordingly, say the study’s authors, the answer to stopping groundwater contamination is to design better storage tanks. Regardless of what additive is mixed with gasoline, the additive will contaminate groundwater if allowed to leak.
Without MTBE, Arizona’s gasoline will more closely match the fuel formula of neighboring California, which already has banned MTBE and utilizes ethanol to meet Clean Air Act requirements. Southern California already supplies nearly 60 percent of Arizona’s gasoline.
Ethanol, however, poses its own set of potential problems.
According to Shih, ethanol has a number of drawbacks: It is more expensive than other additives; doesn’t offer the same air quality benefits; and can’t be mixed with gasoline and transported long distances.
An Unnecessary Mandate
Policy analysts have not missed the opportunity to point out that groundwater contamination by MTBE would not have occurred if the federal government had not mandated costly and only marginally effective gasoline additives in the first place.
According to Ben Lieberman, director of clean air policy for the Competitive Enterprise Institute, “Given the downward trends in motor vehicle emissions, and expected continued declines as older cars and trucks are continually replaced by newer, cleaner ones, it is arguable that there was no need for the federal government to regulate fuel content. Nonetheless, the 1990 amendments to the Clean Air Act established detailed requirements for gasoline.
“Fortunately, the MTBE battle has broadened into a larger debate over whether oxygenates are needed at all,” added Lieberman. He said the best response to MTBE concerns is “to entirely eliminate the oxygen content requirement” from the Clean Air Act.
James M. Taylor is managing editor of Environment & Climate News. His email address is [email protected].