ABSTRACT
In 1995, tetraethyl lead was finally phased out of gasoline in the United States.
That same year, however, the Ethyl Corporation began selling another metal-
based gasoline additive in this country. Ethyl is the same company which pre-
viously made and sold tetraethyl lead (TEL). The new additive, methylcyclo-
pentadienyl manganese tricarbonyl (MMT) is used for the same purpose as TEL:
it enhances octane and thereby acts as an anti-knock agent in gasoline. The
Environmental Protection Agency (EPA) had refused for years to allow Ethyl
to market MMT for addition to unleaded gasoline in the U.S. on the grounds that
“there is a reasonable basis for concern about the effects on public health that
could result (from manganese in gasoline)” [1]. The company challenged this
EPA ruling in court and won. The court of appeals held that the EPA had exceeded
its authority under the Clean Air Act (CAA), and directed the agency to grant the
necessary license. Thus, the court ruling has removed any barrier to introduction
of this additive into our fuel supply.
