Results of magnetic resonance imaging in long-term manganese dioxide-exposed workers

Within a cross-sectional study, the neurotoxic effects of occupational expo sure to manganese were examined. From a group of 90 (58 male and 32 female) workers, 11 men with long-term and high exposure to manganese dioxide (MnO 2) dust were defined as exposed workers. Eleven age-matched workers of simi lar socioeconomic status were used as a reference group. Ambient air and bi ological monitoring (blood, urine, hair), clinical (Webster Rating Scale, W RS), neurophysiological (visual evoked potentials (VEP), nerve conduction v elocity (NCV), electroencephalography (EEG)), and motor performance (Wiener Testsystem) examinations were performed. The pallidal index (PI), the rati o of globus pallidus to subcortical frontal white-matter signal intensity i n T-1-weighted magnetic resonance imaging (MRI) planes multiplied by 100, w as used. For the individual body burden, manganese in blood was the most re liable bio marker. A "job exposure matrix" for the cumulative Mn-exposure i ndex (CEI) was calculated for each worker. The results of WRS, VEP, NCV, EE G, and motor performance tests showed no significant group differences. How ever, the pallidal index was increased in Mn-exposed persons. Furthermore, a statistically significant positive correlation was found between CEI and pallidal index. The results of other studies are discussed. The meaning of MRI findings for health status as well as gender-specific differences shoul d be examined in further follow-up studies. (C) 2000 Academic Press.