Estimation of Respiratory Irritancy from Inhaled Methyl Tertiary Butyl Ether in Mice

Abstract

The Clean Air Act Amendments require the use of oxygenated fuels in the winter months to reduce carbon monoxide levels in areas of the country that exceed national health standards for carbon monoxide. Methyl tertiary butyl ether (MTBE, CAS number 1634–04–4) is the most widely used fuel additive for this purpose. During implementation, people in a few areas of the country reported nose, eye, and throat irritation. Jo evaluate the potential for MTBE to produce symptoms indicative of sensory irritation, mice were tested using a standard bioassay. Concentration-response data obtained from 1-h exposures to MTBE between 300 and 30,000 mglm³ revealed that slight to severe sensory irritation occurred with exposure to all concentrations. At the highest concentration both sensory and pulmonary irritation was observed, indicative of acute lung injury. However, lung lavage protein and lactate deliydrogenase measurements did not support this contention. Respiratory rate was predicted by linear interpolation to be decreased by 50% (RD50) at 16,600 mg/m³ MTBE. Some experts suggest that 3% of the RD50 (in this case 500 mg/m³) would not cause significant sensory (i.e., discomforting) irritation. Since this estimate is at least an order of magnitude greater than typical peak atmospheric exposure levels during refueling, the data would suggest that few healthy individuals would experience sensory irritation during transient exposures to MTBE.