Partial Defluoridation of a Community Water Supply and Dental Fluorosis: Final Evaluation in Britton, S. Dak

In 1948, a defluoridation plant was installed in Britton, S. Dak., where the water supply averaged 6.7 ppm of fluoride. Synthetic hydroxy apatite, used initially as the defluoridating medium, was unsatisfactory; it was replaced with bone char in 1953. The average fluoride level achieved with the bone char was 1.56 ppm, only slightly above the target level of 1.50 ppm. The Britton plant cost $12,245 in 1947. Today, the cost of installing a similar plant is estimated at $50,000. A baseline survey using Dean's fluorosis index was conducted in 1948 on children in grades 1-12; the final followup survey was made in 1970. Data were analyzed only for children who had lived in Britton from birth to 8 years of age and who had used the city's water supply exclusively during that period. Results showed that 100 percent of the 71 children examined in 1948 had fluorosis, whereas of the 154 children examined in 1970, only 46 percent had fluorosis. Moderate to severe forms of fluorosis decreased from 42 percent in 1948 to 3 percent (five children) in 1970. The fluorosis index for baseline examinees was 2.63. Although the fluorosis index declined to 0.81 by 1970, it still exceeded 0.6, the point above which fluorosis is an esthetic problem from a public health standpoint. The most probable reasons that the fluorosis index was not lower related to operational problems of the plant and to the relatively high target level. Results in Britton offer justification for the adoption of partial defluoridation as a public health measure by other communities having water sources containing excessive fluorides.