[A preliminary report on endemic fluorosis caused by treating food with hot spring water].

Fengliang town is situated in the hot spring area in the eastern part of Guangdong province. The concentrations of fluorine in drinking water were less than 0.4 ppm and the prevalence rate of dental fluorosis was 55.43%. A preliminary epidemiological survey showed that the fluorine concentrations of vegetables treated with hot-spring water (F- 20.33 ppm) and dried and those with control water (0.12 ppm) were 55.35 and 16.29 mg/kg respectively. The former was significantly higher than the latter. There was a positive correlation between the dental fluorosis prevalence rate and the distance from residential site to the hot spring in five residential sites and a dose response relationship between prevalence rate and frequency of using hot spring water was observed. It is suggested that the major epidemiological factor of fluorosis in this town is the food contaminated by hot spring water and this area could be designated as an endemic fluorosis area due to food contamination by hot-spring water.