Hygienic Studies on the Silica Contained in Drinking Water

Abstract

Silicosis poses a problem in the field of public welfare now. A member of reports indicate that silica causes arteriosclerosis. From the viewpoints of public hygiene, the author investigated the in vivo effects of silica taken by the oral route, namely by determining the quantity of silica contained in drinking water and its pattern of absorption in the living body. The results obtained were as follows : 1. Determinations were made on the quntities of silica containd in those drinking water samples collected in Kyogok Ucho, Hokkaido, in Tokyo-to, in Akiyama Muro, Yamanashi Prefecture, and in Gotenba City, Shizuoka Prefecture, with the result that apparent differences in the content of soluble silica were noted among the drinking water samples tested, In particular, the silica content of the drinking water sample collected in Kyogok Ucho, Hokkaido, was conspicuously high. 2. Each of the drinking water samples above indicated a high linear coefficient in the correlation between the soluble silica content (determined by means of the colorimetric silicomolybidate method) and the total silica content (determined by means of the gravimetric method). In the regression line, furthermore, these were significant differences noted among the drinking water samples tested. 3. In normal rabbits, a silicate (Na₂SiO₃) solution was immediately absorbed from the stomack and serum levels of SiO₂ were increased. Also, its rapidly excretions into the urine were observed. 4. In normal rats, a silicate (Na₂SiO₃) solution was absorbed from the small intestines, particularly well from the duodenum. 5. Rats were given Na₂SiO₃ solution at dosages of 1mg. daily over a perioa of 25 weeks. They did not develop any differences from control rats in terms of the pattern of growth. Pathological findings on the artery were normal.