Abstract
A widespread dental fluorosis has been found recently in two primary school districts, Soekawadaiichi and Umezawa, in the Kitatsugaru area (northern part of Japan), which was reported in our previous paper (1976). The fluorine concentrations in drinking water were determined monthly by fluoride electrode with samples from 23 deep wells (100-300 meters in depth) during eight months in 1975.
The fluorine concentrations of these samples ranged from 0.31 to 3.18ppm. The waters containing fluorine over 0.8ppm are supplied to 734 houses, which shows 85.4 percent of the total number of houses in these districts. The value of 0.8ppm is the maximum allowable amount of fluorine in communal water established by the communal water administration in Japan. The drinking waters with fluorine concentrations of more than 2.0ppm are supplied to 190 houses (44.4%) in Soekawadaiichi district and 55 houses (12.8%) in Umezawa district.
On the whole, relatively high pH values (pH 7.2-8.7), high sodium (41-265ppm) and chlorine (19-460ppm) concentrations, and low values in total hardness were observed in these samples. It was also noticed that the concentrations of fluorine showed a positive correlation with sodium and chlorine in these samples.
The source of the fluorine detected in the water of these districts has not yet been ascertained. However, the possibilities that result from a mixing of mineral and hot spring waters, an influence of oceanic factors, or elution from fluorine-rich rocks were discussed.
