Manganese neurotoxicity in industrial exposures: Proof of effects, critical exposure level, and sensitive tests

Manganese neurotoxicity has been known for more than 150 years, since Coupe r(1837) described a syndrome, similar to Parkinsonis disease, in Scottish w orkers exposed to high levels of dust while grinding "black oxide of mangan ese" at a chemical industry. Since then, the syndrome has been described in several groups of highly exposed miners and other workers. A thorough revi ew of manganese neurotoxicity was provided by the WHO (1981) and a recent u pdate was written by Mergler and Baldwin (1997). From these reviews it is e vident that the critical effect from manganese exposure is damage to the ce ntral nervous system, and that the effects, once established, are generally irreversible. Therefore, the early detection of symptoms of manganese neur otoxicity in populations at risk is of the utmost importance. In spite of t his fact, only about a dozen studies of manganese exposed groups of workers have been performed using psychological test methods. These studies are br iefly presented, the preponderance of proof for Mn neurotoxicity even in pr esent industrial settings is demonstrated, the critical exposure level is b riefly discussed, the test methods are evaluated, and recommendations for a test battery useful for studies of manganese neurotoxicity, are presented. (C) 1999 Inter Press, Inc.