OBJECTIVES: The objective was to investigate potential nervous system effects of manganese (Mn) exposure in workers employed in manganese-alloy-producing plants. METHODS: One hundred male Mn alloy plant workers were compared with 100 age-matched referents. The subjects were examined with a comprehensive neuropsychological test battery. Exposure was assessed by measurement of Mn concentrations in the workroom air, blood and urine. RESULTS: The geometric mean (GM) concentration of inhalable Mn in workroom air was 301 microg/m(3). The GM concentration of Mn in whole blood (181 nmol/l vs 160 nmol/l) ( P=0.002) and urine (0.9 nmol/mmol creatinine vs 0.4 nmol/mmol creatinine) ( P<0.001) was higher among the exposed subjects than among the referents. The Mn-exposed subjects had increased postural tremor while conducting a visually guided tremor test (static steadiness test) compared with the referents (mean number of contacts 94 vs 59 ( P= 0.001); duration of contacts (in seconds) 5.1 vs 3.5 ( P=0.003)). The tremor had larger frequency dispersion, indicating that the tremor included a wider variety of frequencies, among the exposed subjects than among the referents, assessed by the "TREMOR" test system. Smoking habits (self-reported) influenced the tremor parameters significantly, the Mn-exposed smokers having more tremor than the non-smoking Mn-exposed subjects. No differences between the groups were found in tests for cognitive functions, reaction time or in symptom reporting. CONCLUSION: The Mn-exposed subjects had increased hand tremor compared with their referents. The tremor was related to exposure parameters. Smoking habits (self-reported) influenced the tremor parameters.
OBJECTIVES: The objective was to investigate potential nervous system effects of manganese (Mn) exposure in workers employed in manganese-alloy-producing plants. METHODS: One hundred male Mn alloy plant workers were compared with 100 age-matched referents. The subjects were examined with a comprehensive neuropsychological test battery. Exposure was assessed by measurement of Mn concentrations in the workroom air, blood and urine. RESULTS: The geometric mean (GM) concentration of inhalable Mn in workroom air was 301 microg/m(3). The GM concentration of Mn in whole blood (181 nmol/l vs 160 nmol/l) ( P=0.002) and urine (0.9 nmol/mmol creatinine vs 0.4 nmol/mmol creatinine) ( P<0.001) was higher among the exposed subjects than among the referents. The Mn-exposed subjects had increased postural tremor while conducting a visually guided tremor test (static steadiness test) compared with the referents (mean number of contacts 94 vs 59 ( P= 0.001); duration of contacts (in seconds) 5.1 vs 3.5 ( P=0.003)). The tremor had larger frequency dispersion, indicating that the tremor included a wider variety of frequencies, among the exposed subjects than among the referents, assessed by the "TREMOR" test system. Smoking habits (self-reported) influenced the tremor parameters significantly, the Mn-exposed smokers having more tremor than the non-smoking Mn-exposed subjects. No differences between the groups were found in tests for cognitive functions, reaction time or in symptom reporting. CONCLUSION: The Mn-exposed subjects had increased hand tremor compared with their referents. The tremor was related to exposure parameters. Smoking habits (self-reported) influenced the tremor parameters.
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