The prevalence of dental caries and dental fluorosis was examined in 380 14-yr-old children living in four geographic areas of Sri Lanka with water F-levels of 0.09-8.0 ppm. A reduction in caries prevalence by 43% was recorded in children consuming 0.6-0.79 ppm F- compared to those in low fluoride areas (< 0.4 ppm). Among those consuming drinking water containing < 1.0 ppm F-, however, 32% of the children had mild forms and 9% severe forms of dental fluorosis (Dean's index). Although other sources of F- may contribute to this effect, the prevalence and severity of dental fluorosis seen in low fluoride areas was confirmed to be high in rural Sri Lanka. Our data are comparable with recent findings from other tropical countries, e.g. Kenya and Senegal, and reaffirm that WHO guidelines for the upper limit of F- in drinking water may be unsuitable for developing countries with a hot, dry climate. Current knowledge now enables us to recommend 0.8 ppm as an appropriate upper limit for F- in drinking water supplies for these populations.

This survey examined 59,158 children from 87 schools in 17 out of 24 districts in Sri Lanka for goitre. The overall prevalence rate was 18.8%: 23.2% for girls and 14.0% for boys. Prevalence in districts varied from 30.2% in Kalutara to 6.5% in Matale. It was higher in rural than urban areas, and in inland than coastal areas. The sex ratio of prevalence rates was directly related and the ratio of palpable to visible goitre was inversely related to the severity of the endemic. It is suggested that for a rapid epidemiological assessment when the latter ratio is less than four, it is indicative of endemicity for public health purposes and calls for intervention. The iodination of salt is both practical and feasible in Sri Lanka.

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The prevalence of goiter in a rural community was determined in a defined geographical area, namely, the Hindagala Community Health Project (HCHP). In this area which is divided into six Public Health Midwife (PHM) areas, the mean altitude varies from 450 to 775 meters. The house-to-house goiter survey conducted by the trained field health staff covered 70% of the population. The total goiter prevalence was 7% while the prevalence of visible goiter was 2.8%. The goiter prevalence was higher in the females than in the males at all age groups. Among males, the prevalence was highest in the school-going age group 6-18 years, while among females the highest prevalence was in the early childbearing period of 19-34 years. Further, an increasing trend in the prevalence was observed with increase in mean altitude of the PHM area. Correlation between community prevalence and age-sex specific prevalence gave the best relationship with the 6-18 year age group and a regression equation to predict the community prevalence from the prevalence in the school-going age group is presented.

A total of 13,566 school girls from 17 districts in Sri Lanka recalled their date of menarche for a study on the prevalence of goitre. Seventy-four percent (10,036) did not have any signs of goitre, and the recalled mean age of menarche for this group was 13.6 years. This figure was significantly lower than the mean age of 13.9 years observed in the goitrous group. The mean age was lowest for thyroid grade 0 and highest for thyroid grades 1b and above. The mean age in high prevalence areas was significantly higher both among goitrous and nongoitrous groups, and in different areas of prevalence the mean age was higher among the goitrous than the nongoitrous. These findings strongly suggest a delay in sexual maturation among girls living in endemic goitre areas and among girls with evidence of goitre.