GAS ADDITIVE'S POTENTIAL TOXICITY ALARMS SCIENTISTS

Warning against an "unnecessary and dangerous" public health experiment, 37 U.S. organizations have called on American oil refiners to refrain from using MMT, a manganese-based gasoline additive.

The Ethyl Corporation, which manufactures MMT, argues that the additive is harmless. But critics--including the American Psychological Association, the Learning Disability Association, the Parkinson's Disease Foundation, the Sierra Club, and the Society for Developmental and Behavioral Pediatrics--charge that "Ethyl's claims that this product is safe do not withstand scrutiny." They add that Ethyl made the same safety claims decades ago when it introduced leaded gasoline, a product later banned because of its neurotoxicity.

While the body needs traces of manganese, excess amounts of airborne manganese-- which is more readily absorbed by the brain than dietary manganese--are toxic. High levels of airborne manganese are known to cause speech and movement disorders similar to Parkinson's disease. Miners exposed to excess manganese have a high rate of psychosis, severe neurological disease, and premature death.

No one knows, however, what the effects of chronic, low-level exposure to manganese are. MMT has been used in Canada for more than 15 years (although a number of researchers are lobbying to have it banned there), but no long-term studies have been conducted on its effects. However, one Canadian researcher--initially collecting data on a related topic--found that higher levels of manganese in middle-aged men were linked to an increased rate of poor hand steadiness, a possible sign of neurological impairment. None of the study subjects had been exposed to manganese on the job.

The Environmental Protection Agency attempted to ban MMT for sale in the U.S. because of health concerns, but a court barred the EPA from considering health issues in deciding whether to allow the additive to be marketed, saying the EPA could only evaluate MMT's effect on pollution-control devices. The court also ruled that the EPA's new rules requiring pre-market safety testing of gas additives did not apply in this case, because the application for MMT was filed before the rules took effect.

Because MMT cannot be banned by the EPA at this time, the coalition of anti-MMT groups in the United States is asking for a voluntary ban by refiners. Writing to Exxon, the groups charged that "adding MMT to gasoline will cause uncontrolled dispersion of manganese nationwide and beyond, even though the public health impacts of this action are largely unknown and yet to be evaluated." They also pointed out that several major automobile manufacturers are opposed to use of the additive, which the companies say may cause or contribute to the failure of some emissions control systems.

Herbert Needleman, the leading researcher behind the successful movement to remove lead from gasoline, and colleague Philip Landrigan of Mt. Sinai School of Medicine, are particularly concerned about the potential effects of elevated manganese levels on children. "A child's brain differs in many ways from an adult's," they say, "and [children's] daily lives differ also. As a result, children are more vulnerable to most neurotoxins. Children live and play close to the ground, where automobile exhausts settle." During the critical early stages of brain development, the researchers say, "any noxious influence is likely to produce long-term effects. These effects may announce themselves years later as difficulties in learning, language expression, or in behavioral and attentional disturbances."

Noting the deleterious effects of leaded gasoline, Needleman and Landrigan say, "Surely we can learn something from this costly experience. Surely, this time, before we permit the introduction of a new neurotoxin into our children's lives, we have the right to demand proof that it is unquestionably without harm to them."