MTBE isn't carcinogenic, experts rule

State science board: Fuel additive gets a clean bill of health.

San Jose Mercury News
11 Dec 1998
A state board of scientists has concluded there is not enough evidence to condemn the gasoline additive MTBE as either a human carcinogen or a cause of birth defects.

The decision by the Proposition 65 Science Advisory Board shifts the debate over MTBE from health issues to concerns about taste and odor in drinking water contaminated by underground fuel tanks and boat exhausts leaking into reservoirs.

The scientists, who advise the state Environmental Protection Agency on implementation of Proposition 65, which requires public listing of chemicals known to cause cancer or reproductive toxicity, announced their findings Thursday in Sacramento.

``This is significant,'' said agency spokesman James Spagnole. ``At this time, the best and most independent minds in California are saying that under the guidelines they don't find this stuff a danger.''

Spagnole said the board's findings probably won't change the state's efforts to find alternatives to MTBE as oxygenates to cause gasoline to burn cleaner and reduce air pollution.

But, he added, ``it takes one of the arguments against MTBE off the table. From our perspective, it is not a carcinogen. Now the case has to be made for or against MTBE on different merits.''

The decision was applauded by the Oxygenated Fuels Association, the MTBE industry trade organization.

``This will hopefully take away the hysteria (about MTBE), resolve the health issue once and for all, and allow California and its political leaders to focus on proven air benefits of MTBE,'' said Don Olsen, senior vice president of Huntsman Corp., a Salt Lake City manufacturer of the chemical.

There remains much debate, however, over the air benefits. Early studies credited MTBE with reducing auto emissions including those of the carcinogen benzene, but the most recent report by the University of California found that MTBE doesn't substantially reduce air pollution.

The chemical -- methyl-tertiary butyl ether -- has been added to fuel since 1996 as an oxygenate to make gasoline burn cleaner. It reduces smog-forming compounds in automobile exhausts.

The 1990 federal Clean Air Act requires the use of oxygenates such as MTBE or ethanol, an alcohol produced from corn, in areas that do not meet federal air quality standards, such as the Los Angeles basin and Sacramento.

MTBE became the additive of choice in California because it is a byproduct of the refining process and costs relatively little compared with other oxygenates.

However, the U.S. Environmental Protection Agency has listed MTBE as a possible human carcinogen, a listing now disputed by the state's science advisory board.

In the Bay Area, which has less air pollution than other regions, refineries have been given permission by the state Air Resources Control Board to produce gasoline without MTBE so long as they can still meet state and federal pollution standards.

In Santa Clara County, the controversy blossomed early this year when MTBE contamination from motorboat and personal watercraft exhausts was found in three reservoirs and two wells that supply drinking water.

That discovery prompted the Santa Clara Valley Water District to impose boating limits on the reservoirs to reduce contamination.

Last month, the state Department of Health Services announced new limits on the levels of MTBE permitted in drinking water for taste and odor reasons. Even at low levels, the chemical imparts a bitter taste to water.

Also this fall, the California Energy Commission recommended phasing out MTBE from gasoline over a six-year period.

The state's science board advises the EPA's Office of Environmental Health Hazard Assessment, which is responsible for identifying chemicals whose presence must be disclosed to the public under Proposition 65.

In two separate panels, the board found that it was not clearly shown that MTBE, through ``scientifically valid testing according to generally accepted principles,'' causes cancer or developmental or reproductive toxicity.

The panels of scientists based their conclusions on reviews of toxicological and epidemiological data from the EPA, a report by the University of California-Davis and written public comments and testimony at hearings.

Bill Vance, a special assistant to state Secretary for Environmental Protection Peter M. Rooney, said Thursday that the board's decision is that the evidence does not clearly show MTBE causes cancer.

``But the standard for listing under Proposition 65 is fairly high. It has to be shown that it causes cancer,'' Vance said, adding that the available evidence is ``fuzzy.''

Spagnole said the board's review was the ``broadest examination,'' rolling in all of the studies done in California. It should end Proposition 65 debate about the chemical unless someone files a petition for re-examination or if new legislation is adopted to regulate MTBE.

©1997 - 1998 Mercury Center

Return to Recreational Boat Building Industry Home Page