Distribution of Fluoride in the Drinking Water in the Suburbs of Hirosaki City in a Dental Fluorosis Area

Abstract

This report describes the distribution of fluoride in the drinking water of six primary schools located along the west side of the Iwaki River in Hirosaki City. In these areas, 41 samples were collected from all 37 deep wells (200-300 meters in depth) and four selected shallow wells. The fluoride content of these 41 samples collected in June and November in 1977 was determined with a fluoride-ion electrode. In addition to fluoride analysis, chlorine and sodium were determined in the samples collected in November. The fluoride concentrations of these samples ranged 0.05 to 1.78mg/l. Water containing fluoride over 0.8mg/l came from 14 of these 41 sources. Each area of the six primary schools revealed at least one source which supplied drinking water containing more than 0.8mg/l of fluoride. The concentrations of chlorine and sodium ranged 10-316mg/l and 28-246mg/l in these 41 samples. Many sources showed a higher concentration of these two chemical components than most common ground water in Japan. The fluoride concentrations did not show an evident correlation with chlorine and sodium concentrations (r=-0.190, r=0.033). However, the correlation of chlorine and sodium concentrations showed a high and positive value (r=0.842, p<0.001) in these samples.