Neurobehavioral functioning after cessation of manganese exposure: A follow-up after 14 years

Background Little is known on the long-term course of early manganese (Mn) neurotoxic effects. Mn alloy workers were examined in a follow-up study 14 years after exposure ceased at a Canadian facility. Methods The same battery of neurofunctional tests used in the initial examination in 1990 was administered to 77 Mn-workers and 81 referents in 2004. Results Manganese-workers had poorer scores compared to referents both in the initial and follow-up examinations for several motor tasks of the Luria Motor Scale. At follow-up, older Mn-workers (> 45 years at cessation of exposure) had poorer scores than referents for tests of cognitive flexibility. Cumulated exposure was associated with poorer test scores for certain neuromotor and cognitive tests and on a mood scale. Differences on certain tests observed at initial examination were not present at follow-up. Conclusions Manganese exposure was associated with persistent deficits for certain neuromotor functions, cognitive flexibility, and adverse mood states, while recovery occurred for other functions.