Methyl Tertiary Butyl Ether (MTBE)

For more information on MTBE Treatment, please contact:

Linda Fiedler
Technology Assessment Branch
(703) 603-7194
fiedler.linda@epa.gov

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Toxicology

The majority of the human health-related research conducted to date on MTBE has focused on adverse effects that might result through inhalation of the chemical. At high doses by the inhalation route, MTBE has caused non-cancer health effects as well as tumors in two strains of rat and one strain of mouse in a variety of organs; however, studies have been lacking for human or animal health effects resulting from the ingestion of MTBE in drinking water.

EPA classified MTBE as a "possible" human carcinogen under its 1986 cancer risk assessment guidelines on the basis of results of inhalation cancer tests and has suggested that it be regarded as posing a potential carcinogenic hazard and risk to humans, though no quantitative estimate of the cancer potency of MTBE has been established by EPA because of limitations in the available data. While MTBE has been characterized as an animal carcinogen, both the International Agency for Research on Cancer and the U.S. Department of Health and Human Services have indicated that there are not enough data to classify MTBE with regard to human carcinogenicity under their classification schemes. It should be noted that conclusions in the Office of Science and Technology Policy's 1997 Interagency Assessment of Oxygenated Fuels [cited under Environmental Occurrence] and in a 1996 report by the Health Effects Institute generally support EPA's view on potential carcinogenic hazard. The Interagency Assessment stated, in regard to inhalation risks, that "it is not known whether the cancer risk of oxygenated gasoline containing MTBE is significantly different from the cancer risk of conventional gasoline." The estimated upper bound cancer units risks of MTBE are similar to or slightly lower than those of fully vaporized conventional gasoline, which has been listed by EPA as a probable human carcinogen based on animal carcinogenicity data; however, because of lack of health data on the nonoxygenated gasoline vapors to which humans are actually exposed, it is not possible to have a reasonably good estimate of population cancer risk to conventional gasoline.

EPA reviewed available health effects information on MTBE in its 1997 drinking water advisory guidance and determined that there was insufficient information available on MTBE health effects and exposure to allow EPA to establish a national primary drinking water regulation. The drinking water advisory document indicated there is little likelihood that MTBE concentrations between 20 and 40 µg/L would cause adverse health effects. Nevertheless, California , New Hampshire, and other states have proposed conservative health-based primary drinking water standards of their own for MTBE.

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Human Health

Drinking Water Advisory: Consumer Acceptability Advice and Health Effects Analysis on Methyl Tertiary-Butyl Ether (MtBE)
U.S. EPA, Office of Water, EPA 822-F-97-009, 48 pp, 1997.

An Evaluation of the Scientific Peer-Reviewed Research and Literature on the Human Health Effects of MTBE, its Metabolites, Combustion Products and Substitute Compounds
John R. Froines, et al.
Health and Environmental Assessment of MTBE: Report to the Governor and Legislature of the State of California As Sponsored by SB 521, Volume II.
University of California Toxic Substances Research & Teaching Program, Davis, CA. 267 pp, 1998.

Exposure of Humans to MTBE from Drinking Water
Michael L. Johnson.
Health and Environmental Assessment of MTBE: Report to the Governor and Legislature of the State of California as Sponsored by SB 521. Volume V: Risk Assessment, Exposure Assessment, Water Treatment & Cost-Benefit Analysis.
University of California Toxic Substances Research & Teaching Program, Davis, CA. 13 pp, 1998.

Human Exposure to Methyl tert-Butyl Ether (MTBE) While Bathing with Contaminated Water
S.M. Gordon.
EPA 600-R-05-094, 59 pp, 2003

Describes the results of a study to estimate the relative contribution of the inhalation and dermal pathways during normal baths in water containing MTBE.

Health Risk Perspectives on Fuel Oxygenates
U.S. EPA, Office of Research and Development.
EPA 600-R-94-217, 16 pp, 1994.

Human-Health Effects of MTBE: A Literature Summary
Patty Toccalino, Oregon Health & Science University.
U.S. Geological Survey, National Water-Quality Assessment (NAWQA )Program.
Contact: Patty Toccalino, toccalino@ese.ogi.edu

Interagency Assessment of Potential Health Risks Associated with Oxygenated Gasoline
National Science and Technology Council, Committee on Environment and Natural Resources. 1996.

Methyl tert-Butyl Ether: Summary of Data Reported and Evaluation
IARC Monographs Programme on the Evaluation of Carcinogenic Risks to Humans, Vol 73, p 339, 1999.

Proceedings of the Conference on MTBE and Other Oxygenates: a Research Update
U.S. EPA, National Center for Environmental Assessment.
EPA 600-R-95-134, 274 pp, 1995.

Toxicological and Performance Aspects of Oxygenated Motor Vehicle Fuels
National Research Council, National Academies Press, 176 pp, 1996.

Toxicological Profile for Methyl t-Butyl Ether (MTBE)
Agency for Toxic Substances and Disease Registry, 1996.

TOXNET
National Library of Medicine Specialized Information Services.

This site contains a cluster of databases on toxicology, hazardous chemicals, and related areas, including the Hazardous Substances Data Bank (HSDB), Integrated Risk Information System (IRIS), and Toxics Release Inventory (TRI). The site supports simultaneous searching in multiple databases.

Ecological Impacts

Ecological Risk of MTBE in Surface Waters
Michael L. Johnson.
Health and Environmental Assessment of MTBE: Report to the Governor and Legislature of the State of California as Sponsored by SB 521. Volume III: Air Quality & Ecological Effects.
University of California Toxic Substances Research & Teaching Program, Davis, CA. 10 pp, 1998.

MTBE (t-butyl methyl ether, Methyl tertiary butyl ether, Methyl-Tert-Butyl-Ether, CAS number 1634-04-4)
Environmental Contaminants Encyclopedia, R.J. Irwin, M. VanMouwerik, L. Stevens, M.D. Seese, and W. Basham (compilers).
National Park Service, Water Resources Division, Fort Collins, CO. 36 pp, 1997.

Toxicity of MTBE to Freshwater Organisms
Inge Werner and David E. Hinton.
Health and Environmental Assessment of MTBE: Report to the Governor and Legislature of the State of California as Sponsored by SB 521. Volume III: Air Quality & Ecological Effects.
University of California Toxic Substances Research & Teaching Program, Davis, CA. 19 pp, 1998.

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Last updated on Friday, November 30, 2007