抄録
Recently, the accumulation of radioactive strontium in human bone and teeth caused by nuclear bomb test fallout are increasing. Kerwin proposed the speculation that the retention of radioactive strontium in human body will be increased by drinking fluoridated water everyday, because strontium and fluorine may precipitate within the body as insoluble SrF2. The purpose of this study was to investigate the retention or accumulation of radioactive strontium in the body of animals drinking fluoridated water in graded concentration.
Experimental method and result were as follows:
Four-week aged rats were used for this study. All animals received relatively low fluoride diet and fluoridated drinking water throughout the experiment. According to the concentration of fluorine in drinking water, the animals were divided into 1, 10, 25 and 100 ppm of fluorine groups and control group, and fed for forty days. At forty-first day, those animals were orally administered a single dose of 89Sr, and were sacrificed after one, ten and twentyfive days. 89Sr in femurs in all groups and 89Sr in lower incisor in 10 and 100 ppm fluorine group and control group were analysed.
The significant increase of radioactivity over that of the respective control group were found in 1 ppm fluorine group sacrificed on the 26th day and in 100 ppm fluorine group sacrificed next day, while other experimental groups showed no significant difference compared with the control group.
Following the above experiment, the accumulation of 89Sr in rats was investigated, which were given 89Sr everyday through the experiment. The animals were first given 1, 10 or 50 ppm fluoridated water and low fluoride diet respectively for four weeks and then 89Sr was added to the ration for fifty days. Finally 89Sr in femur and incisor were analysed.
Nither average value of 89Sr in femur nor in incisor in experimental groups (drinking fluoridated water) showed significant differences as compared with that of the control group (drinking distilled water).
The conclusion drawn from above two experiments was that there was no constant correlation between fluorine concentration of drinking water and the retention of 89Sr in hard tissue. And the accumulation of 89Sr in hard tissue in fluoridated groups were not significantly higher than that of the control group even after 50 day administration of 89Sr. Based on these findings the authers could not acknowledge the validity of the speculation of Kerwin.
