Lawmakers Look to Scientists for Answers: Haze of Uncertainty Surrounds Gas Additive

At what price do we bring clean air to cities around the United States? To some government agencies and oil refiners, the answer is clear. At an average cost of 2-3 cents per gallon of gasoline, the oxygenate methyl tertiary-butyl ether (MTBE) can significantly reduce toxic automobile emissions and improve air quality in many smog-choked cities throughout the nation. To lawmakers, the answer has been less certain. MTBE has taken center stage in a political debate that has cast doubt on the safety and efficacy of this widely used oxygenate. With advocates and opponents of MTBE deadlocked, policymakers now have turned to scientists to provide crucial data that would help to determine the fate of MTBE. BACK TO THE BENCH: ASU researcher Jeffrey M. Rousch says scientists have many more questions to answer regarding MTBE. MTBE was introduced in the U.S. in 1979 as an octane booster in unleaded gasoline. But under the Clean Air Act Amendments of 1990, use of the additive skyrocketed. The federal act required use of oxygenates such as MTBE to help gasoline burn cleaner. By 1995, MTBE was added to gasoline in 17 states to help meet air-quality goals. U.S. automobiles now guzzle more than 4 billion gallons of MTBE each year. More than a third of that amount is burned off in automobiles in California. Following the widespread introduction of the additive to gasoline, many areas of the nation saw an increase in reports of such acute symptoms as headaches, skin and eye irritation, dizziness, and a host of other effects. Around the U.S., lawmakers have appropriated funds for comprehensive study and review of the environmental prevalence and effects of the oxygenate. For example, Maine Gov. Angus King ordered widespread groundwater testing for MTBE in May. He then informed federal officials that the state reserves the right to withdraw from the federal reformulated gasoline program in 2000, once more thorough studies of the oxygenate have been completed. California also approved legislation that provides $500,000 for six studies and reviews of the health and environmental effects of MTBE. Interim reports from investigators will be made this month, and final results are due in October. Among the projects funded are: an evaluation of peer-reviewed literature on the human health and environmental effects of MTBE, directed by John R. Froines , a professor of environmental health sciences at the University of California, Los Angeles a risk-based analysis of the relative cost and benefits of oxygenated fuels, coordinated by Arturo Keller, a professor of environmental science and management at UC-Santa Barbara. Following review of the studies by the U. S. Geological Survey (USGS) and the Centers for Disease Control and Prevention, state environmental officials will be required to rule on whether the compound is a human carcinogen. The governor then will have the authority to ban MTBE within the state if necessary. The U.S. Environmental Protection Agency (EPA) hopes that a new report from its Office of Research and Development (ORD) will provide investigators with guidance in the beginning to answer key questions regarding MTBE and its effect on water supplies around the nation. A draft of Research Strategy for Oxygenates in Water has been approved by researchers in the field, and a final report is being prepared for public review, according to J. Michael Davis, a senior scientist at ORD. The report identifies several key areas of assessment that could influence the work of researchers in the life sciences. For example, it notes that little information exists on the extent of human exposure to MTBE-contaminated water. A statistically representative sample of wells and other water sources may be the most cost-effective way to estimate and monitor exposure. The report also notes that although the effects of inhaled oxygenates have been thoroughly studied, little is known about the effects of ingested MTBE. California Sen. Dick Mountjoy , principal author of the legislation that gives the governor authority to ban MTBE, describes recent actions of California lawmakers as necessary steps in beginning to resolve the controversy. Mountjoy's concern over MTBE began as it did in many people. He was showing his grandson how to clean greasy engine parts. As he had done many times before, he put on rubber gloves and began to clean an engine part in gasoline. Surprisingly, the gloves quickly disintegrated. Later that night, his face was covered with red blotches. "I later found out that around that same time, levels of MTBE in gasoline in California had dramatically risen," Mountjoy recalls. Hundreds of reports of acute symptoms linked to exposure to MTBE have been registered around the nation. In New Jersey, more than 800 individuals reported experiencing symptoms such as dizziness, headaches, and rashes soon after the introduction of MTBE into gasoline in 1992. Similar complaints have been recorded in other states, including Alaska, Colorado, Wisconsin, North Carolina, and Maine. Moreover, some studies have cast doubt on whether the oxygenate really can reduce air pollution. Myron A. Mehlman, former chief of toxicology at Fairfax, Va.-based Mobil Corp. and an outspoken opponent of oxygenated fuels, says reports of acute health effects alone warrant a ban on the oxygenate. He is no stranger to doing battle with the oil industry. At Mobil, Mehlman led the fight to reduce levels of benzene, a probable carcinogen by EPA standards, in unleaded gasoline. He was fired from Mobil when he informed a subsidiary in Japan that gasoline there contained dangerous levels of benzene (The Scientist, 12[3]:31, Feb. 2, 1998). In 1996, he won a $7 million wrongful dismissal lawsuit against Mobil. Many researchers in the life sciences are hard at work attempting to answer crucial questions about methyl tertiary-butyl ether (MTBE) and its use as an oxygenate. The U.S. Environmental Protection Agency (EPA) has identified more than 60 new and ongoing projects focusing on the effects of MTBE on air pollution, the environment, and human health, reports J. Michael Davis, a senior scientist at EPA's Office of Research and Development. Many of these studies are expected to be completed this year or in 1999. Glenda J. Moser, a molecular toxicologist at Integrated Laboratory Systems Inc. in Research Triangle Park, N.C., has taken strides in beginning to understand MTBE. She recently completed a study which considered the toxic pathway and effects of chronic exposure of mice to MTBE (G.J. Moser et al., Toxicology Science, 41[1]:77-87, 1998). Moser found that after exposure to carcinogenic doses (8,000 ppm) of MTBE vapor, female mice had significantly decreased body, ovary, and pituitary weight, and the estrous cycle was lengthened. The research team at ILS also observed that DNA synthesis in cervical and epithelial layers of the cervix and vagina decreased significantly. MTBE CYCLE: USGS researchers have identified several possible entryways for MTBE into the hydrologic cycle. For example, MTBE can evaporate at the gas tank and enter surface water through precipitation. Runoff then can wash more MTBE into bodies of water. While Moser admits that the results show an adverse effect of MTBE on the reproductive system of mice, she notes that it is difficult to extrapolate these results to humans. "The doses that the mice were exposed to are massive compared to doses humans are likely to encounter," she says. The study also found that many of the adverse effects of MTBE appeared to quickly reverse, once exposure had ended. "If we can prove that such effects are reversible in humans, then we have gone a long way in answering some of the most important questions about acute and chronic exposure to MTBE," she notes. Jeffrey M. Rousch , a Ph.D. student in plant biology at Arizona State University, also says scientists have many more questions to answer regarding MTBE. His research under ASU plant biologist M.R. Sommerfeld has focused on the effects of MTBE on photosynthetic aquatic life. In his recent study on MTBE and algae, Rousch found that the oxygenate had distinct adverse effects on various species of algae (J.M. Rousch and M.R. Sommerfeld, Archives of Environmental Contamination and Toxicology, 34:6-11, 1998). "Although these doses are realistic in situations like gasoline spills and leakage from holding tanks, it is unlikely that most aquatic life would be exposed to such high concentrations," Rousch says. "But you can't say for sure what effect even small doses would have on other forms of aquatic life. We know very little in this area of study."--S.H. "In the past, the same claims for the safety of MTBE were made for benzene," Mehlman recalls. "Then as more concerns were raised, acceptable levels of benzene exposure began to plummet. The question with MTBE is whether we want to wait until the damage is done and continue to use humans as guinea pigs." Other scientists are less certain. In 1996, the White House National Science and Technology Council issued an interagency assessment of oxygenated fuels ( Interagency Assessment of Oxygenated Fuels, Washington, D.C., Executive Office of the President, 1996). The committee, which included more than 30 researchers, concluded that evidence shows that most people do not experience acute symptoms from exposure to common levels of MTBE. However, they emphasized that these acute claims cannot be dismissed and more controlled research is needed to address these concerns. Much of the oil-refining industry has remained steadfast in its support of MTBE. Officials at the Oxygenated Fuels Association (OFA) in Arlington, Va., tell The Scientist that reports of acute symptoms from normal exposure have been anecdotal and cannot be attributed to MTBE . They note that opponents of MTBE frequently cite studies that appeared in journals not reviewed by peers and that most studies showing adverse health effects of MTBE used massive doses of the additive, which would be unlikely to be encountered in the real world. But in October, Stamford, Conn.-based Tosco Corp. broke ranks with the petroleum industry. In a letter to the California EPA Air Resources Board, Duane Bordvick, vice president for external and environmental affairs at Tosco, urged the agency to allow companies to use oxygenates other than MTBE in gasoline. "Our main concern has been the potential liability the company takes on with MTBE," Bordvick says. "In some places, MTBE has gotten into groundwater, and cleanup costs can be huge." Last December, oil giant Chevron Corp. of San Francisco, joined with Tosco in the plea for more flexible regulations. Chevron maintains that MTBE is safe when handled properly, but it questions whether oxygenates have had an effect in reducing emissions in California. The benefits to the environment from MTBE-enhanced gasoline are numerous, says Charles T. Drevna, director of government and regulatory affairs at OFA. He notes that since the 1980s, more than 70 health studies and assessments of the efficacy of MTBE have been conducted. Many of these studies have shown that MTBE--at levels used by the petroleum industry--is not carcinogenic. Moreover, he says, areas using reformulated gasoline have seen ozone decrease by 11 percent, evaporative emissions by 15 percent, and volatile organic compound (VOC) emissions by 7 percent. Most important, the presence of air toxins such as benzene, which is classified as a probable carcinogen by EPA, fell by about 25 percent. "We welcome the studies by the University of California," Drevna says. "I'm confident that MTBE will be proven safe and effective as we have argued all along." OFA also has vigorously supported measures in California to improve and upgrade underground storage systems of gasoline and MTBE. "In the debate over MTBE, many have forgotten that gasoline--oxygenated or not--is a hazardous material, and it is not something you want to find in water supplies," Drevna says. "As with any hazardous material, oxygenated fuel must be handled, stored, and transported properly to be safe. Hysteria over MTBE has overshadowed this larger issue." The potential for MTBE to enter drinking water supplies has been a major concern in California and the rest of the nation. In 1996, MTBE contaminated 80 percent of Santa Monica's public wells, forcing the city to spend more than $3 million to import untainted water. MTBE also has turned up in groundwater throughout the nation. In 1995, USGS researchers reported that MTBE was present in 27 percent of 211 shallow urban wells tested (P.J. Squillace et al., Environmental Science and Technology, 30:1721-30, 1996). They found that chloroform and MTBE were the two most frequently detected VOCs. However, only 3 percent of those wells exceeded 20 ppb of MTBE, EPA's lower threshold for human detection of the compound by taste and smell. John S. Zogorski, project chief of the VOC National Synthesis Project of USGS and an investigator on the study, says USGS continues to study the sources and extent of MTBE contamination throughout the nation. "MTBE is of particular concern because it is unlike other components of hydrocarbon fuels," Zogorski explains. "MTBE is not readily absorbed by organic material, and it can pass rapidly into the water table and spread as quickly as water. That means that MTBE is harder and more expensive to clean up." Ongoing USGS studies also focus on characterizing ambient sources of MTBE contamination and evaluating how long the chemical can persist in the environment. For example, while most MTBE is thought to be released into the environment from leaky underground storage tanks, it can enter the hydrologic cycle when it is evaporated into the atmosphere from incidental spills at the gas pump or in the backyard. "In our research, we have not taken a position on the health effects of MTBE," Zogorski says. "But the work of other scientists in this area is important to us. After a chemical is introduced into widespread use, you will typically see permissible exposure levels drop as more research is done. When this happens, our understanding of the sources, pathways, persistence, and extent of MTBE in water becomes very important in helping policymakers arrive at an accurate assessment of risk."

Lawmakers Look to Scientists for Answers: Haze of Uncertainty Surrounds Gas Additive

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