WASHINGTON--Although the chemical MTBE, added to gasoline in the
winter to reduce the emission of carbon monoxide, does not pose
a substantial human health risk, more study needs to be undertaken
to assess both short- and long-term health effects, a National
Research Council (NRC) committee said in its review of a draft
of a federal report.
The federal study assessed the effects of methyl-tertiary-butyl
ether (MTBE) on air and water quality, motor vehicles (fuel economy
and engine performance), and public health.
In areas that have not met air quality standards for carbon monoxide,
federal law requires the use of additives that increase oxygen
levels in gas during winter months when lower temperatures tend
to cause vehicles to emit more carbon monoxide. However, available
data indicate that oxygenated fuels reduce winter air levels of
carbon monoxide by as little as 0% to about 10%, the committee
The NRC committee disagreed with the report's conclusion that
only a small percentage of the population may be sensitive to
MTBE, citing studies showing an increase in health problems among
workers exposed to MTBE on the job.
In addition, the panel said, cancer estimates for MTBE were based
on animal models and should not be taken as conclusive. The committee
recommended that further investigations be made into MTBE as a