Chapter 46 - Methyl tert-butyl ether

Abstract

This chapter discusses the reproductive and developmental toxicity of Methyl tert-butyl ether (MTBE) in different species, including rodents, rabbits and aquatic organisms, since the human toxicity data are limited. MTBE is a kind of oxygenate used as a fuel additive in gasoline. It enables fuel to burn more efficiently and helps prevent engine knocking by raising the oxygen content of gasoline and increasing its octane rating. Aside from its use as an oxygenate, MTBE is also used therapeutically for dissolving gallstones in humans. As of 2010, the global production capacity of MTBE is estimated to be approximately 18 million metric tons annually. Thus, the potential exposure of humans to MTBE should be monitored. MTBE has more favorable qualities than other oxygenates, such as its low sulfur content, boiling point, blending vapor pressure and high octane number. It is also inexpensive. In conclusion, in both reproductive and developmental studies of rodents and rabbits with MTBE exposure, no-observed-adverse-effect level (NOAEL) for reproduction and developmental toxicity was at least 1,000 ppm in rodents or rabbits, much higher than the current non-occupational exposure dose (1 ppm). Whether or not the results found in rats or mice are indicative of human responses in terms of health risks associated with MTBE exposure is not currently known. The mouse model seems to be more appropriate to compare with humans than the rat model, but no significant effects to mouse testes or other reproductive organs have been induced by MTBE. Therefore, MTBE unlikely poses human reproductive or developmental hazards.