tert-Butyl methyl ether（MTBE）

On average, levels of methyl t-butyl ether in urine samples from Finnish gasoline road-tanker drivers after a work shift and 16 hours later were reported to be 113 and 18 nmol/L, respectively(1). Breathing zone concentrations among Finnish gasoline lorry drivers were reported at a geometric mean of 4.3 (October 1994) and 6.4 mg/cu m (August 1995). Concentrations in blood were 143 and 213 nmol/L, for October and August, respectively; levels in urine ranged from <5 to 401 nmol/L and 30 to 253 nmol/L 3 and 23 hours post exposure in October, respectively; 17 to 488 nmol/L and <5 to 562 nmol/L 3 and 23 hours post exposure in August, respectively(2). According to the 1999-2000 US National Health and Nutrition Examination Survey (NHANES) methyl t-butyl ether was detected in 26.3% of 354 person...

LC50; Species: Alburnus alburnus (Bleak); Conditions: saltwater, static, salinity 7 ppt; Concentration: >1000000 ug/L for 96 hr /formulation/

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), methyl t-butyl ether, which has a vapor pressure of 250 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere. Vapor-phase methyl t-butyl ether is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 7 days(SRC), calculated from its rate constant of 2.94X10-12 cu cm/molecule-sec at 25 °C(3). Aliphatic ethers, such as methyl t-butyl ether, do not absorb light at wavelengths >290 nm(4), and, therefore, methyl t-butyl ether is not expected to be susceptible to direct photolysis by sunlight(SRC).

The Koc of methyl t-butyl ether has been reported to range from 11 to 12(1,2). In an equilibrium adsorption study using Cohansey soil (94% sand, 2% silt, 4% clay, 1.44% organic carbon)/water systems, the solid/liquid phase partition coefficient was calculated to be 0.0925 from the slope of the isotherm(3). This partition coefficient corresponds to a Koc of 6(4). According to a classification scheme(5), these Koc values suggest that methyl t-butyl ether is expected to have very high mobility in soil(SRC). Methyl t-butyl ether sorbs only weakly to subsurface solids; therefore, sorption does not substantially retard the transport of methyl t-butyl ether by groundwater(6).

PURE CULTURE: Methyl t-butyl was shown to biodegrade using Methylibium petroleiphilum, Methylibium sp., Aquincola tertiaricarbonis and Rhodococcus ruber isolated from an aerated treatment pond system next to a refinery plant in Leuna, Germany(1). In a cometabloic test of methyl t-butyl ether and ethyl t-butyl ether was degraded by Pseudonocardia K1 via biodegradation and acid hydrolysis to ethyl tert-butyl ether and tert-amyl methyl ether(2). An enrichment culture was developed from biosludges of municipal, refinery and chemical plant processes and acclimated to 30-50 mg/L methyl t-butyl ether and incubated for 60 days. t-Butyl alcohol was identified as a metabolite using the enrichment culture following addition of 120 mg/L methyl t-butyl ether. A peak concentration of fo 50 mg/L was o...

Methyl t-butyl ether is not expected to bioaccumulate in surface water aquatic organisms(1). A BCF 1.5 was measured in Japanese carp exposed to methyl t-butyl ether at a concentration of 9.6 to 10.2 ppm over 4 weeks(2). According to a classification scheme(3), this BCF suggests that bioconcentration in aquatic organisms is low(SRC).

The Henry's Law constant for methyl t-butyl ether is 5.87X10-4 atm-cu m/mole(1). This Henry's Law constant indicates that methyl t-butyl ether is expected to volatilize from water surfaces(2). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(2) is estimated as 4 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(2) is estimated as 4 days(SRC). Methyl t-butyl ether's Henry's Law constant indicates that volatilization from moist soil surfaces may occur(SRC). Methyl t-butyl ether is expected to volatilize from dry soil surfaces(SRC) based upon a vapor pressure of 250 mm Hg(3). A recent survey of 15 air-stripping installations indicated...

The rate constant for the vapor-phase reaction of methyl t-butyl ether with photochemically-produced hydroxyl radicals is 2.94X10-12 cu cm/molecule-sec at 25 °C(1). This corresponds to an atmospheric half-life of about 7 days at an atmospheric concentration of 5X10+5 hydroxyl radicals per cu cm(2). tert-Butyl formate has been identified as the major atmospheric degradation product of methyl t-butyl ether; other degradates include methyl acetate, acetone, tert-butyl alcohol, and formaldehyde(3). The rate constant for the reaction of methyl tert-butyl ether with nitrate radicals is 6.4X10-16 cu cm/molecule-sec at 22 °C(4). This corresponds to an atmospheric half-life of about 50 days(SRC) at an average atmospheric concentration of 5X10+8 nitrate radicals per cu cm(5). Methyl t-butyl ether...

ENVIRONMENTAL: Methyl t-butyl ether was detected at average concentrations of 0.01 (max 0.03), 0.01 (max 0.02), and 0.01 (max 0.03) ng/L (detection limit = 0.01 ng/L) in whole milk, 2% milk, and 1% milk, respectively, following analysis of 35 cow milk samples from Los Vegas, NV, surveyed from January 2002 through February 2002; samples represent eight processing plants from Arizona, California, Nevada, and Utah. The average ratio of presence in milk to reported concentration in air was determined to be 0.06(1). A median concentration of 0.09 ng/mL was reported in samples collected May to July 2005 from three residents within nonsmoking household in inner-city Baltimore, MD(2).

Methyl t-butyl ether is present in the gas phase at 5,700 and 1,620,000 ug/km in catalyst-equipped and non-catalyst-equipped emissions, respectively, tailpipe emissions from an in-use fleet of gasoline-powered automobiles and light-duty trucks (production year ranged from 1969 through 1994) tested in California. The composition in gasoline is 109,000 ug/g(1). Based on analysis of automobile emissions in the Guerner Tunnel, Switzerland in 2004, methyl t-butyl ether annual emissions have been estimated to be 0.02 kilotons/year(2).

It is strongly advised not to let the chemical enter into the environment because it is persistent.

SOURCE DOMINATED: The mean levels of methyl t-butyl ether in air at gasoline stations have been reported as 2.6 ppbV at service station perimeters; 29-67 ppbV at the pump island; <5.5 ppbV in the breathing zone during refueling; <6.3 ppbV in vehicle cabin during refueling(1).

Methyl t-butyl ether's production and use as a gasoline additive, chemical intermediate(1), and chromatographic eluent(2) and administration as a cholelitholytic agent(2) may result in its release to the environment through various waste streams(SRC). Among the industrial sources, petroleum refineries formed the largest source category at about 3 million pounds per year, followed by industrial organic chemicals at about 0.34 million pounds; emissions from service stations during refueling were estimated to be 1.3 to 8 million pounds, emissions from 192 million vehicles in the United States were estimated to be 149 to 179 million pounds, with tailpipe emissions accounting for about 73% and the remainder due to evaporation, including about 12% from running losses and 15% from hot soak los...

SOIL: Methyl t-butyl ether exhibited a 4.2% frequency of detection in 720 soil samples from 30 industrial sites in Taiwan(1).

Occupational exposure to methyl t-butyl ether via short-term exposure, less than 30 minutes (TWA, between 6 and 9 hours) was 11.0 (0.24) ppm for transporting neat methyl t-butyl ether, 5.1 (0.58) ppm for blending neat methyl t-butyl ether, 4.7 (0.77) ppm for service station attendants, 3.3 (0.13) ppm for transporting a methyl t-butyl ether/fuel mix, 1.0 (0.14) ppm for manufacturing-maintenance, 0.85 (0.13) ppm for distributing methyl t-butyl ether, 0.84 (0.06) ppm for manufacturing-routine, and 0.58 (0.10) ppm for blending a methyl t-butyl ether/fuel mix(1). Long-term (93 to 570 minutes) methyl t-butyl ether exposure concentrations for refueling attendants were 0.5 ppm or less; winter and summer geometric mean exposures were 0.2 ppm and 0.08 ppm, respectively(2). Winter and summer mecha...

Methyl t-butyl ether's production and use as gasoline additive, chemical intermediate, and chromatographic eluent may result in its release to the environment through various waste streams. If released to air, a vapor pressure of 250 mm Hg at 25 °C indicates methyl t-butyl ether will exist solely as a vapor in the atmosphere. Vapor-phase methyl t-butyl ether will be degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals; the half-life for this reaction in air is estimated to be 7 days. Aliphatic ethers, such as methyl t-butyl ether, do not absorb light at wavelengths >290 nm, and, therefore, the compound is not expected to be susceptible to direct photolysis by sunlight. If released to soil, methyl t-butyl ether is expected to have very high mobility base...

Ingestion Exposure: Abdominal pain. Nausea. Vomiting. Further see Inhalation.

Urinary

LC50 (rat) = 23,576 ppm/4h

ACGIH Carcinogen - Confirmed Animal.

The substance can be absorbed into the body by inhalation and by ingestion.

Methyl tert-butyl ether (MTBE) is a high-octane fuel component that helps gasoline burn cleaner and reduces automobile emissions. In 1999, the International Agency for Research on Cancer (IARC) categorized MTBE as "not classifiable" regarding human carcinogenicity, and additional studies since 1999 have substantially added to the evidence base to examine the carcinogenic potential of MTBE in humans. The authors of this publication conducted a systematic literature search and review to identify mechanistic data, as well as studies investigating cancer in MTBE-exposed humans and experimental animals. They noted that evidence extracted from the literature demonstrates that the mechanism of male rat renal tumors does not operate in humans and stated that MTBE is unlikely to be a carcinogeni... CDC-ATSDR Toxicological Profile

AIR INTAKE: Arithmetic mean occupational doses via air were in the range of 0.1 to 1.0 mg/kg-day, while doses from residential exposures, commuting, and refueling were in the range of 0.0004 to 0.006 mg/kg-day(1). WATER INTAKE: The estimated arithmetic mean dose for the population exposed via water was 1.4X10-3 mg/kg-day(1).

Oral Slope Factor Reference: CALEPA

IARC Monographs: Volume 138

LC50 Mouse inhalation 180,000 ppm/ 10 min

Soil Saturation Concentration (mg/kg): 8.87e+03

Evaluation: There is limited evidence in humans for the carcinogenicity of methyl tert-butyl ether. There is limited evidence in experimental animals for the carcinogenicity of methyl tert-butyl ether. Overall evaluation: Methyl tert-butyl ether is not classifiable as to it carcinogenicity to humans (Group 3).

Advanced treatment: Consider orotracheal or nasotracheal intubation for airway control in the patient who is unconscious, has severe pulmonary edema, or is in severe respiratory distress. Positive-pressure ventilation techniques with a bag-valve-mask device may be beneficial. Consider drug therapy for pulmonary edema ... . Monitor cardiac rhythm and treat arrhythmias if necessary ... . Start IV administration of D5W /SRP: "To keep open", minimal flow rate/. Use 0.9% saline (NS) or lactated Ringer's (LR) if signs of hypovolemia are present. For hypotension with signs of hypovolemia, administer fluid cautiously. Consider vasopressors if patient is hypotensive with a normal fluid volume. Watch for signs of fluid overload ... . Use proparacaine hydrochloride to assist eye irrigation ... . /...

Soil Saturation Concentration (mg/kg): 8.87e+03

Reference: Smith, C.D. and Nowell, L.H., 2024. Health-Based Screening Levels for evaluating water-quality data (3rd ed.). DOI:10.5066/F71C1TWP