Environmental effects and exposures to manganese from use of methylcyclopentadienyl manganese tricarbonyl (MMT) in gasoline

Methylcyclopentadienyl Manganese Tricarbonyl (MMT) has been used since the 1970s in the U.S. as a gasoline octane enhancer. Extensive testing of the e ffects of MMT on regula ted gaseous emissions carried out on a wide variety of automobiles showed that use of MMT resulted in significantly lower NOx emissions. Tests showed that less than 15% of the manganese from MMT combus tion was emitted from the tailpipe, mostly in the PM2.5 fraction as mangane se phosphate, with some manganese sulfate and a very small amount of mangan ese oxide. MMT has been used in Canada in virtually all unleaded gasoline f or about 20 years. A probability-based study involving over 900 personal ex posure samples in Toronto confirmed exposures to airborne PM2.5 Mn in the g eneral population are quite low (.008 mu g/m(3) - median). Ambient levels o f airborne manganese in Toronto are about the same as those in areas where MMT is not used. Exposures to manganese among the general population in Tor onto are well within safe limits determined by the U.S. EPA and other stand ard setting bodies around the world. (C) 1999 Inter Press, Inc.