MTBE water contamination raises health concerns, research questions The discovery of the fuel additive methyl tert-butyl ether (MTBE) in groundwater and drinking water reservoirs has raised new public health concerns about the oxygenate, which is currently classified as a possible carcinogen. In California, public health officials in one municipality shut down some drinking water supplies because of high MTBE concentrations, and the state recently ordered testing of all drinking water An EPA draft MTBE lifetime health advisory has been stalled while the agency awaits validation of a 1995 study showing an increased cancer risk MTBE has been used since the mid-1970s as a fuel additive, first in concentrations of 3% to boost octane, and more recendy in concentrations of 13-15% to reduce carbon monoxide emissions during the winter in areas that do not meet federal carbon monoxide standards. Concerns about the health effects from inhaling gas fumes began in winter 1992 when residents of Alaska, Montana, Wisconsin, and New Jersey reported symptoms such as headaches and nausea which were attributed to increased levels of MTBE in gasoline EPA's Office of Research and Development (ORD) in February launched a concerted effort to pull together existing and ongoing research on MTBE and determine where to target new research. A draft interagency report by the White House Office of Science and Technology Policy says that animal studies suggest MTBE is either "possibly or probably a human carcinogen." The report raises many more questions about MTBE than research has answered. An Italian study of MTBE (Belpoggi et al., Toxicol. .nd. Health, 1995, 11, 119-49), one of a few that have looked at ingestion, showed increased leukemia and lymphoma in female rats and increased tumors in the testes of male rats. EPA is awaiting verification of that study before releasing a draft MTBE health advisory stating that adverse health effects from MTBE are unlikely from levels of exposure below 70 parts per
billion, according to Charles Abernathy of the Office of Water. EPA and the scientific community, which focused MTBE research on inhalation over the past decade, were blindsided by the recent discovery of MTBE in water. U.S. Geological Survey data from 1993-94 show MTBE in
California recently began requiring public water systems to test for MTBE. shallow groundwater in Denver, New England, and other areas in the United States, with highest concentrations in urban areas (ES&T, ,uly y195, p. 305A). Now, scientific interest in MTBE is on the rise. Researchers attending the American Chemical Society's national meeting in San Francisco this month will present a general review of MTBE studies. EPA likewise plans to take stock of MTBE research in the ORD effort. Michael Davis of ORD said the agency would like to find a way to use inhalation data from past studies to assess oral toxicity. ORD is interested in a Chemical Industry Institute of Toxicology (CUT)
project that might offer a shortcut the agency is looking for, he said. CUT researcher Susan Borghoff has developed a physiologically based pharmacokinetic model to extrapolate route-to-route MTBE exposures from inhalation to ingestion and from rats to humans. Borghoff explained that the model mathematically simulates drinking water ingestion and applies absorption data gleaned from inhalation studies done during the past 20 years. Borghoff said the model results will either indicate or rule out the need for long-term studies. "Now short-term studies need to verify the ability of the model to predict [MTBE concentration in tissues] following different exposure scenarios," she said. James Prah, a researcher with EPA's National Health and Environmental Effects Research Laboratory in Research Triangle Park, N.C,, said EPA is considering his proposal for a short-term human inhalation exposure study designed to look at the accumulation of MTBE and its main metabolite, tert-butanol, in the blood. "We're aiming at levels people are more likely to be exposed to/' said Prah. For his experiment, those levels will be about 30 parts per million He said data from this study could be used to verify Borghoff's models Borghoff said CUT will also use data from the pharmacokinetic
Groundwater contamination A U.S. Geological survey study released in 1995 showed MTBE in shallow groundwater of some urban areas.
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model to better understand results from various animal studies that showed signs of carcinogenicity from MTBE exposure. Key to this understanding, said Borghoff, is linking MTBE exposure to the dose of MTBE and metabolites that actually reach the target tissue and cause some effect. After contamination was found in 11 drinking water sources in California, state officials in February started requiring all public water systems to test for MTBE. The worst contamination to date resulted from underground gas tank or pipeline leaks in Santa Monica, where concentrations reached 94 ppb. "We have shut down the majority of the city's
wells," said Craig Perkins, director of the city's Environmental and Public Works Department. Perkins said the city believes MTBE has worked its way into both shallow and deep groundwater. Cleanup of Santa Monica's drinking water is at a standstill because the state doesn't know how to filter out MTBE contamination, said Perkins. Researchers and water authorities have found MTBE to be highly soluble and resistant to most filtration systems. Oregon Graduate Institute researcher Clinton Church said aeration seems to be the best way to get MTBE out of water. However it is much harder to remove the compound from the environ-
ment, said Church, because it vaporizes when removed from water and is extremely persistent. Church said researchers have found that MTBE biodegradation takes from one to three years. Another researcher at the Oregon Graduate Institute, James Pankow, has shown that the atmosphere in major cities where MTBE is being used may have become a nonpoint source for the transport of MTBE into shallow groundwater. MTBE in urban atmospheres partitions into rain in easily quantifiable measures according to Pankow's study. He will present his results at the American Chemical Society's meeting this month. VINCENT LECLAIR
EPA issues new guidance to improve states' water quality reports This month, EPA will issue new guidance that it hopes will lead to a more complete and accurate assessment of the nation's aquatic health. Under the Clean Water Act, section 305(b), states are required to submit a biennial report to EPA assessing the condition of their waters. The reports have been criticized for poor data quality resulting from nonrepresentative sampling methods, limited state monitoring resources and inconsistent use of biological indicators. According to Barry Burgan, EPA's national 305(b) coordinator, the reports cover less than onefifth of the nation's waters and data quality varies widely from state to state. Following the recommendations of an advisory group convened last year, the new 305(b) guidance advises states to submit reports on a fiveyear cycle, adopt a probabilistic sample design, and report on biological indicators. State water quality officials Steve Butkus of the Washington Department of Ecology and Chris Yoder with the Ohio EPA applauded the guidance as a way to reduce bias in assessments. But they questioned how many states would adopt the voluntary guidance. The switch to a five-year reporting cycle is being made, according to Burgan, because states were spending too much time preparing reports and not enough time monitoring water quality.
Beginning this August, EPA will ask states to report annually on 20% of their waters, so that after five years all bodies of water in each state will have been covered. Butkus called the switch from census sampling to probabilistic sampling "one of the most positive changes in the new guidance." Census sampling design requested that states directly
The agency advocates biological indicators, probabilistic sampling on 305(b) reports. sample all water bodies, but states have not had the resources to undertake such extensive sampling. Butkus reports that Washington State, for instance, was able to report on only 4% of its streams in 1996. He noted that census sampling led to targeted sampling of a few large water bodies, resulting in a national 305(b) report that was largely incomplete and heavily biased toward a few sampling stations. Probabilistic sampling takes data from a random sample of a state's watersheds and extrapolates the results to all watersheds in the state. According to Burgan, probabilistic sample design will enable EPA for the first time to track trends in water quality.
Butkus cautioned that states will need assistance because "probabilistic sampling design requires GIS [geographic information systems] skills for designing sample surveys and assessing data." Dave Chestnut, watershed coordinator with the South Carolina Department of Health and Environmental Control, questioned whether this approach would be economically feasible. He claimed that in his state the effort spent on sampling would have to nearly double because census stations that target problem areas could not be abandoned The move to report on biological indicators shows that "EPA is starting to recognize that there is a gradient of data quality among the states' 305(b) reports," concluded Yoder. He explained that although some states may base their water quality assessments only on chemical data from a few stations, others may have hundreds of stations sampling a full range of physical and biological data. Therefore Yoder said results among states are not easily compared Despite improvements to the 305(b) reporting process, critics are not entirely satisfied with the changes. Yoder noted that although EPA "has done everything to promote biological monitoring, short of requiring it," further incentives will be needed to get states to adopt it. JANET PELLEY
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