The effect of occupational exposure to manganese dust and fume on neuropsychological functioning in Australian smelter workers.

Chronic low-level occupational exposure to manganese (Mn) is reportedly associated with the development of Parkinsonian-like symptoms. In a study of 143 manganese smelter workers, inhalable Mn exposure was associated with lower performances on the Digit Symbol Coding and Stroop tests; respirable Mn exposure was associated with improved Digit Symbol Coding test performance and reduced performance on the Trail Making (Part A), Matrix Reasoning, and Stroop tests. While these relationships reached statistical significance, the magnitude of these effects was significantly smaller than the standard error of measurement of the neuropsychological tests, indicating that these differences are not of clinical significance.