The results obtained were as follows;

The highest airborne Mn fume concentration among the work process was found at charging (0.42 mg/m3), and ferromanganese crushing process (1.14 mg/m3) was the highest in Mn dust. However all of them were below threshold limit value. Mean Mn concentrations in blood and urine of crushing workers were higher than those of other part workers. Among all of them, workers whose urine Mn concentration were exceed normal reference level (10 microgram/l) were 31 (18.5%). There was statistically significant correlation between airborne and urine Mn concentration (r=0.60), and so between airborne and blood Mn concentration (r=0.49), while there was no statistically significant correlation between blood and urine Mn concentration. Mean Mn concentration in airborne (0.60 mg/m3), urine (6.92 microgram/l) and blood (3.16 microgram/dl) in exposed group were significantly higher than those of control groups (p<0.01). Clinical symptoms such as excessive sweating, hypoesthesia, libido change, anosmia, decreased visual acuity and difficulty in writing showed higher positive rate in exposed group. Positive rate of clinical signs such as eye blinking and masked face in exposed group was higher than external control group. However clinical and laboratory findings such as blood pressure, blood chemistry, grip strength in exposed group were not statistically different from those of control groups.

The results suggested that further studies were followed to evaluate the workers whose blood Mn concentration were below normal reference level but urine Mn concentrations above normal reference level, and to establish the questionnaire and the diagnostic tools to detect the Mn poisoning workers early.