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most soluble and most mobile components in MTBE, and to a lesser amount the metabolite tertiary
<br /> gasoline In oxygenated gasoline, MTBE is even more butanol (Savolainen and others, I985) are the main
<br /> soluble and mobile than any of the BTEX compounds respiratory excretion products (Research Triangle
<br /> (Garrett and Moreau, 1986, Barker and others, 1990, Institute, 1994) Tertiary butanol has been determined
<br /> Luhrs and Pyott, 1992, Odermatt, 1994) In fact, to be a carcinogen in laboratory animals (Cirvello and
<br /> evidence indicates that MTBE moves as rapidly as a others, 1995) MTBE also is metabolized to formal-
<br /> conservative tracer(Barker and others, 1990, Hubbard dehyde, methanol, formic acid, carbon dioxide, 2-
<br /> and others, 1994) MTBE persists in ground water
<br /> under both aerobic and anaerobic conditions (Barrer methyl-1,2-propanediol, and a-hydroxyisobutyric
<br /> and others, 1990, Suflita and Mormile, 1993, Hubbard acrd (Research Triangle Institute, 1994) MTBE and
<br /> and others, 1994, Mormile and others, 1994, Yeh and its metabolites show little tendency to distribute and
<br /> Novak, 19%) because it resists physical, chemical, accumulate in tissues, although MTBE and tertiary
<br /> and microbial degradation It is anticipated that the butanol may distribute to the brain at concentrations
<br /> USEPA draft drinking-water lifetime health advisory similar to blood concentrations (Research Triangle
<br /> for MTBE will be assigned a value of 20 or 200µg/L Institute, 1994) Most MTBE and tertiary-butanol are
<br /> (micrograms per liter), an advisory of 20µg/L will be rapidly excreted (Research Triangle Institute, 1994),
<br /> used if the tentative classification as a possible human but there is evidence showing that a portion of these
<br /> carcinogen is accepted, otherwise the advisory will be
<br /> 200µg/L (USEPA, 1995) The health advisory is the chemicals are deposited in deeper body stores and are
<br /> maximum concentration in drinking water that is not slowly excreted over a longer period of time
<br /> expected to cause any adverse effects over a lifetime (Moolenaar and others, 1994, Prah and others, 1995)
<br /> of exposure, within a specified margin of safety The MTBE is not expected to bioaccumulate in surface-
<br /> USEPA expects to issue the final health advisory in water aquatic organisms (Research Triangle Institute,
<br /> the fall of 1995 MTBE is on the USEPA's Drinking 1994)
<br /> Water Priority List, which means it is a possible
<br /> candidate for future regulation under the Safe This report presents preliminary findings on the
<br /> Drinking Water Act. There are no current Federal occurrence and possible sources of MTBE in ground
<br /> regulations that require municipalities to test for water in selected areas of the United States sampled as
<br /> MTBE in drinking water, consequently, there are few
<br /> data on the occurrence of MTBE in ground water part of the U S Geological Survey's National Water
<br /> Quality Assessment (NAWQA) Program This
<br /> The USEPA has tentatively classified MTBE as a program is designed to describe current water-quality
<br /> possible human carcinogen on the basis of studies that conditions and trends for 60 of the largest and most
<br /> show MTBE is a carcinogen in animals (Burleigh- important river basins and aquifer systems nationwide
<br /> Flayer and others, 1992, Chun and others, 1992, (Leahy and Thompson. 1994) Investigations in these
<br /> Belpoggi and others, 1995), however, no epidemio- 60 areas,referred to as"Study Units,"are the principal
<br /> logical studies have been conducted to determine if building blocks of the NAWQA program Ground-
<br /> MTBE is a human carcinogen Documents describing water data from the first 20 Study Umts are summa-
<br /> the health effects from exposure to MTBE have been nzed in this report The data include analyses from
<br /> written by Environment Canada and Health Welfare water samples collected from 194 shallow monitoring
<br /> Canada (1993), Prah and others (1995), Research ,Hells, 12 springs and 5 shallow water supply wells in
<br /> Triangle Institute (1994), and the USEPA (1992x, urban areas, 562 shallow wells in agricultural areas,
<br /> 1994a) Rats and mice exposed to MTBE by and 412 wells screened to deeper parts of 9 Study Unit
<br /> inhalation or ingestion showed increased incidence of
<br /> benign and malignant tumors, and lymphomas and areas representing regionally extensive aquifers
<br /> leukemias (Burleigh-Flayer and others, 1992, Chun Samples from these wells were analyzed for 60 VOCs,
<br /> and others, 1992, Belpoggi and others, 1995) MTBE 82 pesticides, up to 17 trace elements, 15 mayor
<br /> is absorbed rapidly and extensively from the respi- inorganic compounds, 6 nutrients, and dissolved
<br /> ,ratory and gastrointestinal tracts, and unchanged organic carbon (filtered,0 45 µm (micrometer))
<br /> 4 A Preliminary Assessment of the Occurrence and Poselble Sources o-f MTBE In Ground Water
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