Biological Monitoring of Inorganic Mercury in Workers in a Fluorescent Lamp Plant



Masako IDEM, et al

Matsushita Electronics Corp., Okayama Factory

Inorganic mercury, Occupational exposure, Biological monitoring,
N-acetyl-beta-D-glucosaminidase, Fish consumption. Confounding factor S. Kira, Department of Public Health, Okayama University Medical School, 2-5-1 Shikata-cho, Okayama City 700, Japan
J Occup Healthyear1998Vol40No168-72

The level of mercury in urine is measured as an exposure monitoring of mercury, and the activity of urinary N-acetyl-beta-D-glucosaminidase (NAG) is used as an index of adverse effects of mercury on human kidneys. Here we examined the validity of these procedures by comparing the urinary total mercury (U-Hg) level and NAG activity in both 75 male workers exposed to inorganic mercury and age-matched unexposed male workers in a fluorescent lamp plant. To investigate factors affecting the levels of U-Hg, 12 items were selected in relation to oral intake and excretion of mercury: consumption of 1) soft drink, 2) coffee or tea, 3) milk and 4) alcohol; 5) habit of drinking tap water at the work place; frequency of 6) eating fish and 7) alcohol intake; 8) smoking; 9) use of dental amalgam; 10) eating of home grown rice; 11) exercise habit and 12) age. The U-Hg level and NAG activity were adjusted by creatinine levels. Personal exposure levels of inorganic mercury in air (A-Hg) and the U-Hg level correlated well (p<0.001) in the exposed group but neither the exposed nor unexposed group showed a correlation between the U-Hg level and NAG activity. Although the mean level of U-Hg in the exposed group was higher than that in the unexposed (p<0.001), no difference was observed in the mean level of NAG activity. A multiple regression analysis followed by a one-way ANOVA revealed that only the frequency of eating fish per week contributed to increase the level of U-Hg. The results suggest that oral intake of mercury from fish is a possible confounding factor in the exposure monitoring of inorganic mercury in the work place.