Manganese Exposures in Toronto During Use of the Gasoline Additive, Methylcyclopentadienyl manganese tricarbonyl

Methylcyclopentadienyl manganese tricarbonyl (MMT) is a manganese containing compound produced by Ethyl Corporation (Richmond, Virginia) to raise the octane rating of gasoline. MMT was used in leaded gasoline in the U.S. from 1976 until leaded gasoline was phased out in 1995. It was also used in unleaded gasoline from 1976 until the adoption of the 1977 Amendments to the Clean Air Act, and for a short period in 1979 while crude oil was in short supply. Use of MMT in unleaded gasoline was temporarily discontinued because of a provision in the 1977 Amendments that required manufacturers to demonstrate that use of an additive would not harm a vehicle’s emission control equipment. In 1995, a Federal court ruled that MMT satisfied this requirement, and MMT was approved for use in unleaded gasoline.

Kenny S. Crump (Journal of Exposure Analysis and Environmental Epidemiology, 2000)