MANGANESE IN THE US GASOLINE SUPPLY

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic manga nese compound recently approved for use in the United States as a gaso line additive. MMT use is expected to increase. This Commentary analyz es the impact of MMT use on population exposure to manganese, the heal th effects associated with manganese exposure, and the possibility tha t MMT use will lead to toxicity in the population. Although MMT Else w ould result in only a small increment in most people's manganese expos ure, certain populations will be disproportionately exposed. Although manganese is an essential nutrient at low levels, high-level manganese exposure leads to a characteristic severe nervous system toxicity. Pu lmonary toxicity also occurs at high levels of exposure, and developme ntal toxicity to fetuses is an important concern based on more limited data. Selected subpopulations may be especially susceptible to the to xic effects of manganese. The critical question is whether the additio nal population exposure to manganese that would result from widespread MMT use would lead to toxic effects. Currently available evidence doe s not permit firm conclusions. Common sense and prudence therefore dic tate that MMT not be used until further data are available and its saf ety is confirmed. Several measures are recommended to address the impe nding use of MMT in the U.S. gasoline supply. (C) 1997 Wiley-Liss, Inc .