The health implications of increased manganese in the environment resulting from the combustion of fuel additives: A review of the literature

Abstract

Methylcyclopentadienyl manganese tricarbonyl (MMT) is effective in raising the octane level of gasoline and is currently used in Canada for that purpose in a maximal concentration of 18 mg Mn/l (slightly less than 0.07 g Mn/U.S. gal). It has been estimated that if MMT were used in all U.S. gasoline in these amounts, the median increase of Mn in ambient air would be not more than 0.05 microgram Mn/m3, with increments generally less than 0.5 microgram Mn/m3 along urban corridors. The scientific literature was reviewed to determine how the increases in environmental manganese predicted from MMT use would relate to the amounts in the natural environment and necessary to life and to the concentrations associated with toxic effects. Even with additional manganese from the use of fuel additives, total Mn intakes would remain within the range of average amounts absorbed from food and water. Respirable manganese in ambient air due to MMT combustion would be many order of magnitude below the concentrations associated with occupational manganism and respiratory problems and also below those reported in isolated episodes of respiratory symptoms in communities near ferromanganese plants. Evidence was reviewed on the possibilities of: (1) increased absorption of inhaled manganese compared with ingested manganese; (2) hypersusceptibility of infants and persons of advanced age; and (3) increased absorption associated with iron deficiency. While relevant to high levels of exposure, these factors would not be expected to lead to toxic effects from the very low concentrations of Mn resulting from MMT use. Experimental animals that inhaled the combustion products of MMT in concentrations of approximately 10, 100, and 1000 micrograms Mn/m3 for 9 mo did not show toxic effects, although there was temporary elevation of tissue levels of Mn. Rhesus monkeys, susceptible to the neurologic effects of Mn, showed no symptoms after inhaling the combustion products of MMT in concentrations of 100 micrograms Mn/m3 for up to 66 wk. Monkeys exposed to 5000 microgram Mn/m3 also showed no symptoms. There is thus a wide margin of safety between the intakes of Mn essential to health and the high concentrations that have been associated with toxic effects. The small amounts of manganese added to the environment by the combustion of MMT used as a fuel additive would be comparable to the normal background and should not create health problems.

Seasonal contribution of air pollution of urban transport in the city of Chillán, Chile

“…All components from mobile sources increased in the fall and winter and were lower in spring and summer. Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) used in unleaded gasoline as an antiknock agent [16]. Its use has increased substantially and its combustion leads to the formation of oxides of manganese (99.9%), especially manganese tetraoxide or hausmannite (Mn 3 O 4 ).…”

Exposure of urban ecosystems to Mn and Pb contaminants from gasoline additives beside a major highway in the Greater Toronto Area, Canada

“…This disease, known as manganism, begins as a loss of appetite, apathy, fatigue, psychotic behaviour, and clumsiness. At lower levels of exposure, delayed reaction time, poor hand-eye coordination, memory loss, and tremors have been reported (Mena 1974, Moran 1975, Tar Haar et al 1975, USEPA 1975, Pierson et al 1978, Barbeau 1984, Cooper 1984, Abbott 1987, Ethyl Corporation 1990. Experimental data on animals have shown that exposure to MMT produces severe injury to the kidneys, liver, lungs and the central nervous system (Komura andSakamoto 1992, U.S. Dept.…”

“…It has been suggested that one of the main sources of inorganic Mn contamination in the urban environment may be the combustion of fuel containing MMT (Joselow et al 1978, Davis et al 1988, Zayed and (Cooper 1984). 1994). Since 1974, medical studies have attempted to predict the contribution of Mn fi-om the combustion of W-containing fuels to the atmospheric Mn concentration.…”

“…MMT [CH,C5H4Mn(C0)3] is an organic derivative of manganese (Mn) used as an anti-knock agent in unleaded gasoline (Cooper 1984). Introduced in Canada in 1976(Environment Canada 1987, MMT has seen a substantial increase in utilization over the last few years , and has now completely replaced lead in gasoline (Royal Society of Canada 1986, U.S. Dept.…”

Deposition of Mn from Automotive Combustion of Methylcyclopentadienyl Manganese Tricarbonyl beside the Major Highways in the Greater Toronto Area, Canada

“…1 The additive was first developed in the 1950s by scientists at Ethyl Corp. and is marketed under the trade name HiTEC 3000-performance additive. 2 MMT was first used in Canada in 1976 as an antiknock agent in unleaded gasoline.…”