Testimony of Daniel S. Greenbaum,
President, Health Effects Institute
Before the United States Senate
Committee on Public Works and the Environment
Hearing on the Use of Methyl Tertiary-Butyl Ether (MTBE) in Gasoline
September 16, 1998

Mr. Chairman, Senator Baucus, and members of the Committee, I am pleased to have the opportunity to testify before you today to present the views of the Health Effects Institute (HEI) on the health effects of MTBE in gasoline. My name is Dan Greenbaum, and I am President of HEI, an independent, not-for-profit research institute, funded jointly by U.S. EPA and industry to provide high-quality, impartial, and relevant science on the health effects of air pollution to inform public and private decisions.

HEI, as one part of its larger strategic research plan for air pollution, has been engaged in scientific assessment and research on MTBE and other oxygenates added to gasoline for several years. In 1995 and 1996, at the request of the White House Of lice of Science and Technology Policy (OSTP), and of the Administrator of EPA, we convened an Expert Panel to review all existing science on exposure to and health effects from the addition of MTBE and Ethanol to gasoline. Their report, The Potential Health Effects of Oxygenates Added to Gasoline, which I will present to you today, became part of the larger Interagency Assessment of Oxygenated Fuels completed by OSTP last year. Following that report, HEI launched a targeted program of studies to answer key remaining questions about these oxygenates, most notably the first studies of the potential interaction of MTBE in a mixture with gasoline, and studies comparing the body's metabolism of MTBE with other additives such as ETBE and TAME.

The Potential Health Effects of Oxygenates Added to Gasoline

In April of 1996, the HEI Oxygenates Evaluation Committee -- consisting of leading experts in toxicology, epidemiology, cancer, reproduction and development, and exposure, and chaired by the former Director of the National Cancer Institute Dr. Arthur Upton -- issued the report of its 9-month review of all available data on the health effects of oxygenates added to gasoline. This study, which involved detailed review of over 300 individual studies of MTBE and ethanol, looked at the detailed effects of each substance and found that there were a number of potential short term and cancer health effects for MTBE whose existence in humans needed further investigation, but that there were not likely to be any health effects from ethanol at the levels to which most people would be exposed. The Committee then attempted to place the MTBE effects in the context of what the scientific community knows about the effects of exposure to vapors and emissions from gasoline that does not contain oxygenates. Overall, the Committee concluded that:

The potential health effects of exposure to components of conventional gasoline (without oxygenates) include short-tern and cancer effects similar to those that could result from exposure to gasoline containing oxygenates.

Adding oxygenates to gasoline can reduce the emission of carbon monoxide and benzene from motor vehicles, and thereby lower certain risks to members of the population. At the same time, using oxygenates increases exposure to aldehydes, which are carcinogenic in animals, and to the oxygenates themselves.

Adding oxygenates is unlikely to substantially increase the health risks associated with fuel used in motor vehicles; hence 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.

For the Committee's benefit, I have attached a list of the members of the Oxygenates Evaluation Committee, and a copy of the report's executive summary. We have also provided the full report to your staff.

Further Analyses and Research on Oxygenates in Gasoline

Subsequent to the release of the HEI report, research and analyses continued on several fronts:

The Interagency Assessment of Oxygenated Fuels In June, 1997, the Office of Science and Technology Policy issued the results of its comprehensive review of the use of oxygenates in fuel. This review, which incorporated the HEI findings on health effects, and also analyzed the effects of oxygenates on fuel economy, engine performance, and water quality, drew similar conclusions to those of HEI on the health effects of MTBE. In reviewing the health effects, the Interagency Task Force also conducted a preliminary quantitative risk assessment for MTBE, based on animal cancer data, and concluded that:

"The estimated upper-bound cancer unit risks for MTBE are similar to or slightly less than those for fully vaporized conventional gasoline, substantially less than that for benzene, a minor constituent in gasoline that is classified as a know human carcinogen; and more than 100 times less than that for 1,3-butadiene, a carcinogenic emission product of incomplete fuel combustion."

The World Health Organization Earlier this year, the International Programme on Chemical Safety (IPCS) of the World Health Organization issued its Environmental Health Criteria for MTBE. They reached many conclusions similar to those of HEI and the Interagency Report and, as a result of an detailed review of the data on MTBE and cancer, concluded that:

"Based on these data, MTBE should be considered a rodent carcinogen. MTBE is not genotoxic and the carcinogenic response is only evident at high levels of exposure that also induce other adverse effects. The available data are inconclusive and prohibit their use for human carcinogenic risk assessment until outstanding complications in their interpretation have been addressed."

New research In keeping with the needs identified in the HEI report, additional research, funded by HEI, by industry in response to U.S. EPA requirements under section 211 of the Clean Air Act, and by other government agencies has gone forward to answer key questions, including understanding better (1) the way MTBE and other oxygenates such as ETBE and TAME are metabolized by the body, (2) how MTBE might cause cancer, and (3) the effects of MTBE-gasoline mixtures.

In addition, in response to concerns about the potential effects of MTBE in drinking water, the State of California in October, 1997 enacted legislation requiring a comprehensive analysis of the health and environmental significance of MTBE and other oxygenates by the University of California, and the U.S. EPA issued in April of this year a draft Research Strategy for Oxygenates in Water.

The studies underway as a result of these efforts are expected to provide new information over the next 12 to 18 months. To date, however, relatively few studies have been completed beyond those reviewed in the HEI Oxygenates Study.

The Issue of MTBE in Water Supplies

Both the HEI and the Interagency Task Force reports identified reports of water contamination by MTBE as a potential route of exposure, but noted that there were relatively few data on the extent of such contamination, or the health effects of ingesting rather than inhaling MTBE. The Interagency Report also noted that MTBE appears to move faster in ground water and is more resistant to biodgradation than other components of gasoline, although the data on this issue, particularly from field studies, is limited.

Given concerns about potential contamination of drinking water, California in 1991 established an "action level" for MTBE in drinking water of 35 ug/L, and U.S. EPA, in December, 1997, published a drinking Water Advisory for MTBE that identified the level of 20 -- 40 ug/L as a level below which health effects are unlikely, and above which water users are likely to smell and/or taste MTBE before levels become unhealthful. Most recently, California is considering the establishment, in response to recent legislation, of a Maximum Contaminant Level, or"goal" of 12.5 ug/L.

In recent years, in response to drinking water concerns, there has been an increase in the sampling of water supplies for MTBE, especially in California. To date, the results of that sampling confirm the findings in the Interagency Report that MTBE is detected in a relatively small number of water sources of those tested, and of those where it is detected, relatively few have levels above existing or proposed levels of concern. Specifically, as of February, 1998, California had tested 24 % (2,638) of all water sources in the state, and detected MTBE in 1.3% (34) of those sources. Of those 34 where MTBE was detected, five sources, which had been contaminated by leaking underground storage tanks, had levels in excess of the current California action level, and nine sources appeared to have levels exceeding the currently proposed M.C.L.

Thus, it appears that contamination to date has not been widespread, but that potential drinking water contamination by MTBE continues to be of some concern and regular monitoring, particularly of wells located near underground storage tanks, may be appropriate.

Summary and Conclusions

In closing, let me thank the Committee again for this opportunity to testify, and summarize the key points of my comments:

First, reviews of the health effects of MTBE in gasoline by HEI and others have concluded that although potential health effects have been identified, the use of oxygenates in gasoline does not appear to substantially increase the risk of health effects from inhalation when compared to gasoline without oxygenates.

Second, questions about these health effects continue, and HEI, government agencies, and industry groups have studies underway to address them; and

Third, incidents of high levels of contamination of water supplies with MTBE have increased concerns about the health effects of ingesting MTBE, although more comprehensive sampling has suggested that such high-contamination incidents are relatively isolated to intense contamination incidents such as leaking underground storage tanks. Continued regular monitoring of water supplies may be appropriate to ensure that such risks do not become more widespread.

Thank you for your attention. I would be pleased to answer any questions you might have, and to provide other information that might help the Committee's efforts.