Fuel Additive Under Attack as Health Risk


In a cruel twist in the battle to clean the environment, promoters of MTBE, a major additive in what officials call California’s cleaner burning gasoline, are finding that the ingredient itself is on trial.

Clean air experts are convinced that reformulated gasoline containing the additive has brought about significant smog reductions in the state with the nation’s worst air quality. But it may be a carcinogen, and it threatens to foul drinking water.

In the Legislature, conservative lawmakers and environmentalists alike are carrying measures that would require detailed health studies of MTBE, keep the chemical from getting into water, and, in the extreme, ban it outright.


“We’re sitting on a keg of dynamite,” said Sen. Richard Mountjoy (R-Arcadia), a conservative sponsoring a bill that could result in the additive’s ban if a University of California study shows it to be hazardous.

The measure cleared its final Senate committee last week and is headed for a Senate floor vote as early as this week. The Senate also could vote this week on legislation by Sen. Tom Hayden (D-Los Angeles) that would require the state to determine whether the chemical is a carcinogen or causes birth defects. Hayden’s bill also could result in a phaseout of the additive, if studies find that its risks outweigh its benefits.

All the while, radio talk show hosts are slamming the California Air Resources Board for supporting the use of MTBE in gasoline, an additive they say causes everything from cancer and asthma to engine fires.

On the other side, the oil industry--having spent $5 billion in the 1990s to retool California refineries to make the reformulated gasoline--has embarked on a major lobbying effort to defend the additive.

Allied with clean air officials and some environmentalists, oil industry lobbyists proclaim that the additive is the closest thing to a smog-reducing silver bullet they’ve found.

“It has been the biggest success in 25 years, maybe ever,” said K.C. Bishop, a lobbyist for Chevron. “It has worked beyond the wildest dreams.”


Air Resources Board officials say the introduction of gasoline containing MTBE has been equivalent to taking 3.5 million cars off California’s roads. Air pollution readings show that the new gasoline has cut the presence of asthma-inducing ozone and cancer-causing benzene in the air.

“If we lose this, we’ll have dirtier air,” said Janet Hathaway, a senior attorney for the Natural Resources Defense Council.

But unlike most components of gasoline, which cling to the soil and degrade when they spill into the ground, MTBE dissolves like salt in water. Once it mixes with water, it flows downward at the speed of ground water and does not readily break down.

Already, the additive leaking from underground storage tanks has been detected in a number of wells in the state. State officials have not determined that its presence in water can cause cancer or other illnesses--but they have not been able to rule out the possibility, either. Moreover, the substance can be tasted and smelled at extremely low levels. If it can be tasted, water purveyors say, people won’t drink the water.

Is the additive as good or as bad as its supporters and critics suggest? A look at the chemical, through the prism of more than 20 interviews and a review of major research, shows uncertainty about its risks, as well as some questions about its benefits.

Developed by the Arco oil company, methyl tertiary butyl ether is a petroleum-based byproduct made in part from methanol.


It was used in small amounts in gasoline starting in 1979 to boost octane. That changed when Congress approved the Clean Air Act of 1990, which required states to crack down on the source of half the nation’s smog--auto emissions.

One way to reduce emissions is to increase oxygen content in gasoline. Oxygen causes the fuel to burn more completely. Led by Arco, the oil industry offered MTBE as the additive of choice. Other so-called oxygenates, such as ethanol, had supply uncertainties and other problems, industry officials said. Federal officials approved MTBE.

Suddenly, the additive became an industry unto itself. Oil companies and their sister corporations produce 20 billion pounds of it a year, making it the second-most-common commercial chemical produced in the nation, with production rising 25% a year. In California, the largest single market, it accounts for 11% of the 30 million gallons of gasoline used each day.

Reformulated gasoline was introduced in Southern California in 1995, and in the rest of the state last year. Other states are considering switching to California’s reformulated gasoline, making the fight in California even more important to the additive’s producers.

For all its use, however, scientific conclusions about the chemical’s effects are few.

“We find ourselves concerned about its toxicity years after the decision to add it as an oxygenate,” said toxicologist John Froines, chairman of the Department of Environmental Health Sciences at UCLA. “We need more research. Saying that now comes a bit late.”

The National Research Council and the Health Effects Institute reached similar conclusions last year in studies funded in part by the U.S. Environmental Protection Agency. Both called for more study into reformulated fuel: its cancer risks, its effect on the nervous and respiratory systems, and the extent to which it threatens water and cleans the air.


Given that gasoline itself is highly toxic, the Health Effects Institute gave MTBE faint praise, saying it “is unlikely to substantially increase the health risks associated with fuel used in motor vehicles.”

“Hence,” the report said, “the potential health risks of oxygenates are not sufficient to warrant an immediate reduction in oxygenate use at this time. However, a number of important questions need to be answered if these substances are to continue in widespread use over the long term.”

Many of those questions involve the additive’s affect on water.

In the early 1990s, when California officials were considering requiring oil companies to switch to cleaner gasoline, their focus was on air, not water. They did not consider the impact of the new gas on water quality.

“The short answer is, it was never an issue,” said Joan Denton, an air pollution expert for the state air board. “Nobody raised it.”

The magnitude of the additive’s threat to water in California is not known. The California Department of Health Services has directed water agencies across the state to test for its presence in drinking water. Results are expected by late summer.

To date, state health officials say the number of drinking water sources in which the additive has been detected is small--21 of 1,850 tested. But among the contaminated wells are seven used for drinking water in Santa Monica. They were fouled by leaking underground gasoline storage tanks. MTBE levels were so high that officials closed the wells. Water experts worry that Santa Monica is a harbinger.


“The concern is that it’s on the way,” said Mark Beuhler, head of water quality for the Metropolitan Water District of Southern California.

The potential for water pollution is there. A third of Southern California’s drinking water comes from wells, and there are thousands of underground gasoline storage tanks, many of them leaking. The chemical already has shown up in hundreds of monitoring wells not used for drinking.

“We have a lot of potential leakage,” Beuhler said. “It may well be we’re seeing the tip of iceberg.”

To track the migration of pollutants into drinking water, local water officials monitor shallow aquifers not used for drinking. The findings are raising concerns. In Santa Clara County, the additive has turned up in more than 220 shallow wells not used for drinking water.

In Orange and Riverside counties, tests of shallow aquifers beneath 376 gasoline leaks showed the additive at 332 sites, said Kurt Berchtold, assistant executive officer of the Santa Ana Regional Water Quality Control Board.

“The level of concern is high,” Berchtold said. “At least for some of those sites, if left unabated, the concentrations that we see in ground water now could pose a threat to drinking water supplies.”


MTBE has also been detected in reservoirs, including Lake Perris in Riverside County, Castaic Lake near the Grapevine, and Lake Shasta in Northern California. All are used for drinking water--and each is open to motor boats, suggesting that the additive enters lakes from exhaust and spills, and that it is washed from the air by rain.

One way to limit the additive’s presence in lakes would be to require that boats use fuel without it. A more drastic step would be to ban motorboats on reservoirs. Such a move is not under discussion now, but “it’s certainly something that could be considered in the future,” said Beuhler.

Homing in on water issues, Democrats led by Sens. Byron Sher of Stanford and Hayden of Los Angeles hope to use concerns over the additive to force Gov. Pete Wilson’s administration to require more aggressive cleanup of spills from the state’s 70,000 gasoline storage tanks.

They also want the administration to scrap a proposed policy that would require owners of leaking gas tanks to merely “contain” leaks, in the hope that the pollutants will dissipate before reaching drinking water.

Although unsure of the additive’s health risks, the state health department’s guideline for its presence in water is 35 parts per billion, twice as strict as the federal government’s tentative standard.

By contrast, the state standard for a far more toxic component of gasoline--benzene--is one part per billion, roughly the equivalent of a speck of dust in a liter of water.


In the early 1990s, as state officials looked for ways to clean smog, one of their prime targets was benzene, a poison so potent that in 1986 it became the first pollutant ever listed by the Air Resources Board as a toxic air contaminant. Benzene is also highly soluble in water and has been found in many shallow aquifers near leaking gasoline tanks.

Gasoline emissions account for 90% of benzene in the air, but benzene, a naturally occurring component of petroleum, was needed in gasoline to boost combustion. Adding MTBE allowed benzene levels in gasoline to be cut by half.

Air board experts believe that by reducing benzene and the cancer-causing 1,3-butadiene, the new gasoline will reduce the incidence of cancer in California by 35 cases a year.

Though far less potent than benzene, MTBE is considered a possible or probable carcinogen. It has been shown to cause various types of cancer in mice and rats, “something that cannot be dismissed,” said UCLA’s Froines. The new gas also adds to airborne formaldehyde, another carcinogen.

However, convinced of its overall benefits, the Air Resources Board cites readings showing that introduction of the new gasoline coincides with a drop in ozone levels, a major cause of respiratory disease.

Ozone levels in Southern California have dropped 18%--greater than what was anticipated when reformulated gas was proposed. There were somewhat lesser reductions of carbon monoxide, which is a threat to people with heart problems. Initially, the board predicted a 17% cut. Readings show an 11% decrease.


“There is no way you could get a reduction of that magnitude without the cleaner gas,” said the air board’s Allan Hirsch.

Given such findings, the air board is working hard to build support for reformulated gasoline. In a paper extolling the new gasoline’s air benefits, the board called the additive a potentially “weak carcinogen” that might cause one to two cancers per million people a year.

Said the paper: “The very slight increase in risk from MTBE in ambient air is overwhelmingly offset by the reduced cancer risk from the use of California cleaning burning gasoline.”



MTBE, or methyl tertiary butyl ether, has emerged in the 1990s as the most common additive used to boost gasoline’s oxygen content and make it burn cleaner. Oil companies recently completed a retooling of their California refineries at an estimated cost of as much as $5 billion to manufacture reformulated gasoline with MTBE to comply with state and federal clean air requirements. By using MTBE, oil refiners were able to remove most benzene, a known human carcinogen, from gasoline. MTBE can cause cancer in laboratory animals, although it is thought to be far less toxic than benzene. Experts say reformulated gasoline has improved air quality and dramatically lowered concentrations of benzene in the air, but MTBE has been spreading into water wells, primarily from leaking underground gasoline tanks. In California, the problem is most acute in Santa Monica, where water from several municipal wells has been rendered undrinkable.