Metabolism of Ether Oxygenates Added to Gasoline

Research Report 102,

Human Cytochrome P450 Isozymes in Metabolism and Health Effects of Gasoline Ethers Jun-Yan Hong, Yong-Yu Wang, Sandra N Mohr, Flordeliza Y Bondoc, and Chenjun Deng

Biotransformation of MTBE, ETBE, and TAME After Inhalation or Ingestion in Rats and Humans Wolfgang Dekant, Ulrike Bernauer, Elisabeth Rosner, and Alexander Amberg

MTBE Inhaled Alone and in Combination with Gasoline Vapor: Uptake, Distribution, Metabolism, and Excretion in Rats Janet M Benson, Edward B Barr, and Jennifer R Krone

The three research projects contained in this report were initiated to increase our knowledge of the metabolism of ether oxygenates in humans and other species. Adding oxygenates, such as MTBE (methyl tert-butyl ether), to gasoline promotes more efficient combustion and reduces emission of carbon monoxide, ozone-forming hydrocarbons, and some air toxics, by increasing the oxygen content of the fuel. On the other hand, some oxygenates may increase emission of toxic compounds such as formaldehyde or acetaldehyde, and increased use of MTBE in fuel in the early 1990s led to complaints of unpleasant odor, headaches, and burning of eyes and throat. Dr Jun-Yan Hong (the University of Medicine and Dentistry of New Jersey – Robert Wood Johnson Medical School) used rat and human liver cells to determine the relative contribution of different members of a family of liver enzymes to the metabolism of MTBE, ethyl tert-butyl ether (ETBE), and tert-amyl methyl ether (TAME). He also examined blood samples from human volunteers who reported that they were sensitive to the health effects of MTBE, in order to determine whether genetic variants of CYP isozymes were present. Dr Wolfgang Dekant (University of Würzburg) exposed rats and human volunteers by inhalation to two concentrations of MTBE, ETBE or TAME in order to provide detailed data for interspecies comparison. He also exposed human volunteers by ingestion to MTBE or TAME to compare metabolic pathways after inhalation and ingestion of these compounds. Dr Janet Benson (Lovelace Respiratory Research Institute) exposed rats by inhalation to several concentrations of MTBE alone or to MTBE in combination with gasoline vapors in order to determine how the presence of gasoline effects the uptake, kinetics, metabolism and excretion of MTBE.