Welding fume contains manganese (Mn) which is known to be bio-available to and neurotoxic for the central nervous system. Although an essential metal, Mn overexposure may cause manganism, a parkinsonian syndrome. The present welder study sought to improve the clinical portrait of manganism and to determine dose-effect relationships. The welders were employed in the construction of the new Bay Bridge (San Francisco) and welded in confined spaces for up to 2 years with minimal protection and poor ventilation. Neurological, neuropsychological, neurophysiological, and pulmonary examinations were given to 49 welders. Clinical cases were selected on the basis of apriori defined criteria pertaining to welding history and neurological/neuropsychological features. Among the 43 eligible welders, 11 cases of manganism were identified presenting with the following symptoms: sleep disturbance, mood changes, bradykinesia, headaches, sexual dysfunction, olfaction loss, muscular rigidity, tremors, hallucinations, slurred speech, postural instability, monotonous voice, and facial masking. Significant associations between outcome variables and cumulative exposure index (CEI) or blood Mn (MnB) were obtained with CEI for variables implicating attention and concentration, working and immediate memory, cognitive flexibility, and verbal learning; and with MnB for executive function, cognitive flexibility, visuo-spatial construction ability, and visual contrast sensitivity. This study strongly suggests that neuropsychological features contribute in a dose-effect related way to the portrait of manganism usually characterized by tremor, loss in balance, diminished cognitive performance, and signs and symptoms of parkinsonism.
Rosemarie M. Bowler, 8371 Kent Dr, El Cerrito, CA 94530