It is especially dangerous to young children. In 1994, the E.P.A. blocked the manufacture of the addditive, citing the health hazards. But in October a Federal appeals court in Washington ruled on narrow technical grounds that M.M.T. was not covered by a regulation that required fuel additives to be tested before they could be sold. It ruled that the Ethyl Corporation could test the additive while selling it, and set no deadlines for completion of the tests. Both the E.P.A. and the Environmental Defense Fund want the petroleum industry to label pumps that use gasoline containing M.M.T. Ethyl's assertions that M.M.T. is safe do not withstand scientific scrutiny.
Laboratory studies show that manganese crosses the placenta and retards growth in fetal rodents.
When inserted into the brain cells of rats, it disturbs the normal functioning of the cells. Ethyl claims that M.M.T. has been used safely in Canada for 19 years. But no systematic studies of manganese in humans have been done in Canada or elsewhere. Children are more vulnerable than adults to most neurotoxins. They live and play close to the ground, where fumes from tailpipes settle.