Manganese accumulation in the olfactory bulbs and other brain regions of “asymptomatic” welders

Welding-generated metallic fumes contain a substantial amount of manganese (Mn), making welders susceptible to Mn toxicity. Although overtMn toxicitymanifests as a type of parkinsonism, the consequences of chronic, low-level Mn exposure are unknown. To explore region-specific Mn accumulation and its potential func-tional consequences at subclinical levels ofMn exposure, we studied seven welders without obvious neurological deficits and seven age-and gender-matched controls. Mn exposure for welders was estimated by an occupational questionnaire. High-resolution brain magnetic resonance imaging (MRI), Grooved Pegboard perfor-mance of both hands, Trail making, and olfactory function tests were obtained from all subjects. Compared with controls, the welders had a significantly higher T1 relaxation rate (R1) in the olfactory bulb (OB, p5 0.02), meanT1-weighted intensity at frontal white matter (FWM; p 5 0.01), bilateral globus pallidus (GP; p