| Co-Investigator(Kenkyū-buntansha) |
ISHII Noriko Akita University, School of Medicine, Professor, 医学部, 教授 (10222944)
NAKAI Kunihiko Tohoku University, Graduate School of Medicine, Associate Professor, 大学院・医学系研究科, 助教授 (00291336)
KARITA Kanae Teikyo University, School of Medicine, Lecturer, 医学部, 講師 (40224711)
IWATA Toyoto Akita University, School of Medicine, Instructor, 医学部, 助手 (00321894)
DAKEISHI Miwako Akita University, School of Medicine, Instructor, 医学部, 助手 (70375236)
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| Research Abstract |
The objectives of this research were to clarify the subclinical effects of environmental hazardous factors such as lead, cadmium, and methylmercury (MeHg), on nervous and renal functions in humans. (1) The first study was carried out to estimate the critical dose of lead affecting the neuromotor function in workers by introducing the benchmark dose (BMD) approach. Postural sway parameters with spectral analysis were compared between 121 lead workers with BPb levels of 6-89 μg/dl and 60 unexposed controls. All sway parameters, except for sagittal sways with eyes open, were significantly larger in the lead workers than in the controls. The critical dose of BPb was estimated to be 12.1-17.3 μg/dl for postural sway. (2) To investigate the relations among total mercury (THg) levels in hair, toenail, and urine, together with potential effects of MeHg intake on renal tubular function, their levels, and urinary N-acetyl-glucosaminidase activity (NAG) and α1-microglobulin (AMG) were determined
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in 59 women, and estimated daily mercury intakes from fish and other seafood using a food frequency questionnaire. THg levels in the women were 1.51±0.91 (SD) μg/g in hair, 0.59±0.32 μg/g in toenail, and 0.86±0.66 μg/g creatinine (Cre) in urine ; and, there were positive correlations among them. The daily mercury intake of 9.15±7.84 μg/day was significantly correlated with THg levels in hair, toenail, and urine. Among the women, the NAG and AMG were positively correlated with both the daily mercury intake and THg levels in hair, toenail, and urine ; and, these relations were almost similar when using multiple regression analysis to adjust for possible confounders such as urinary cadmium (0.47±0.28 μg/g Cre). In conclusion, MeHg resulting from fish consumption can explain total mercury levels in hair, toenail, and urine to some degree, partly through the degradation into the inorganic form. (3) To clarify the neuromotor effects of occupational exposure to mercury vapor, hand tremor and postural sway were measured in 27 miners and smelters and 52 unexposed subjects. The means of the urinary mercury level (UHg) were 228 μg/g Cre for the exposed workers and 2.6 μg/g Cre for the unexposed subjects. Total tremor intensity and frequency-specific tremor intensities at 1-6 and 10-14 Hz were significantly larger in the exposed workers than in the unexposed subjects, but they were not significantly related to the UHg among the exposed workers. In contrast, there were no significant differences in any postural sway parameters between the above two group, but the transversal sway with eyes open was positively related to the UHg among the exposed workers in using multiple regression analysis. These findings suggest that postural sway and hand tremor, may be affected by elemental mercury vapor exposure. Less
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