Js. Tepper et al., ESTIMATION OF RESPIRATORY IRRITANCY FROM INHALED METHYL TERTIARY BUTYL ETHER IN MICE, Inhalation toxicology, 6(6), 1994, pp. 563-569
The Clean Air Act Amendments require the use oi oxygenated fuels in th
e winter months to reduce carbon monoxide levels in areas of the count
ry that exceed national health standards for carbon monoxide. Methyl t
ertiary butyl ether (MTBE, CAS number 1634-044) is the most widely use
d fuel additive for this purpose. During implementation, people in a f
ew areas oi the country reported nose, eye, and throat irritation. To
evaluate the potential for MTBE to produce symptoms indicative of sens
ory irritation, mice were tested using a standard bioassay. Concentrat
ion-response data obtained from 1-h exposures to MTBE between 300 and
30,000 mg/m(3) revealed that slight to severe sensory irritation occur
red with exposure to all concentrations. At the highest concentration
both sensory and pulmonary irritation was observed, indicative or acut
e lung injury. However, lung lavage protein and lactate dehydrogenase
measurements did not support this contention. Respiratory rate was pre
dicted by linear interpolation to be decreased by 50% (RD50) at 16,600
mg/m(3) MTBE. Some experts suggest that 3% of the RD50 (in this case
500 mg/m(3)) would not cause significant sensory (i.e., discomforting)
irritation. Since this estimate is at least an order of magnitude gre
ater than typical peak atmospheric exposure levels during refueling, t
he data would suggest that few healthy individuals would experience se
nsory irritation during transient exposures to MTBE.