|IDENTIFICATION AND USE: Methyl tertiary-Butyl Ether (MTBE) is a colorless liquid. It is used as octane booster for unleaded gasoline (up to 7% by volume). HUMAN STUDIES: Humans exposed to motor fuel containing MTBE have experienced increase frequency of respiratory, allergic, and neurologic reactions. Symptoms in humans also include headaches; nausea; vomiting; burning sensation in the nose, mouth, or throat; cough; dizziness; nosebleeds; eye irritation; spaciness and disorientation; breathing problems; fatigue; inability to concentrate; shortness of breath; anxiety; depression; stomach cramps; poor memory; insomnia; and loss of appetite. Aspiration into the lungs may result in chemical pneumonitis. MTBE induced DNA double-strand breaks at 200 uM in human lymphocytes. ANIMAL STUDIES: In studies on animals, MTBE is moderately acutely toxic and induces mild skin and eye irritation but not sensitization. Repeated exposure in rodents affects primarily the kidney and the liver. Exposure to MTBE results in reversible central nervous system (CNS) effects including sedation, hypoactivity, ataxia and anesthesia at higher concentrations and biphasic effects on motor activity at lower concentrations. Inhalation exposure to MTBE produced increased incidences of kidney and testicular tumors in male rats and liver tumors in mice. Oral administration of MTBE produced increased incidences of leukemias and lymphomas (combined) in female rats and testicular tumors in male rats (see the table). MTBE has not induced adverse reproductive or developmental effects in rodents at concentrations less than those that were toxic to the parent. In zebrafish embryos MTBE disrupted angiogenesis. MTBE was not genotoxic in Salmonella assay and the mouse bone marrow micronucleus test. However, statistically significant increases in sister chromatid exchange were observed in female rats given MTBE. ECOTOXICITY STUDIES: Chronic exposure over three weeks to effective MTBE concentrations as low as 0.11 mg/L induced a significant increase in the vitellogenin concentration of male zebrafish (Danio rerio). In African catfish Clarias gariepinus developmental exposure to MTBE resulted in deformed eyes, mouthparts, and spinal cord and in increased larval mortality. MTBE is toxic to various aquatic organisms at concentrations of 57 to 1000 mg/L (invertebrates), and 388-2600 mg/L (vertebrates). MTBE was toxic to earthworm species. Lettuce was most sensitive to MTBE, followed (in order of decreasing sensitivity) by wild oats, wheat, and sweet corn.