Conversation so far:
why is mtbe used as a gasoline additive
Methyl tert-butyl ether (MTBE) is a blending component of gasoline, used as an oxygenate to raise the octane number and to replace tetraethyllead (TEL).
what is the benefit of raising the octane number in gasoline
In the U.S. Methyl tert-butyl ether (MTBE) has been used in gasoline at low levels since 1979 as an antiknock (octane rating) additive to prevent engine knocking.
what are alternatives to methyl tert-butyl ether (mtbe) to prevent engine knocking
Alternative oxygenates to methyl tert-butyl ether (MTBE) available as additives for gasoline including ethanol and other ethers such as ethyl tert-butyl ether (ETBE).
what are other uses of methyl tert-butyl ether (mtbe) besides as an antiknock
Methyl tert-butyl ether is extensively used in industry as a safer alternative to diethyl ether as the tert-butyl group prevents forming potentially explosive peroxides.

Question: are there any health or environmental impacts
Self-contained rewrite: are there any health or environmental impacts from the use of methyl tert-butyl ether (mtbe)