放射化分析による頭髪中水銀量の測定 : 1症例より頭髪中水銀量の経時的変化

抄録

The concentration of mercury in head hair obtained from a man, who is suspected to have been exposed to mercury vapours and inhaled it, was determined by a method of non-destructive activation analysis based on the detection of the 68 Kev X-rays and 77 Kev Gamma-rays of 65-hour ¹⁹⁷Hg. About 100 mg of hair, cut to equal length and at the same distance from the scalp at the same part of the head every month for seven months, was washed to be got rid of surface contamination with either a nonionic detergent or organic solvents, followed by rinsing with distilled water. After neutron irradiation of the sample in HTR reactor for 5 hours in a thermal neutron flux of about 1×10¹²n/cm²-sec, followed by cooling for 5 days to decrease short-lived contaminating activities, mercury was determined by direct gamma-ray spectrometry. Results from the hair samples showed that the concentration of mercury decreased monotonically from 20.4 ppm to 4.6 ppm. On the other hand, results from samples obtained from a group consisting of seven individuals who had shared similar diets with the man above stated and another group of twelve individuals belonging to the other groups showed a significant difference between the man inhaling mercury vapours and these groups. Namely, the range of the concentration of mercury of these groups was from 1.9 ppm to 6.2 ppm. By the non-destructive activation analysis of head hair, it is able to deal with more cases in a shorter period. Detectable limit is 0.07 ± 0.02μg, and the necessary minimum quantity of hair is enough below 50 mg. It is necessary to care in obtaining hair, because mercury is very tightly bound to the hair and not easily removed by washing.