The relationship between the endemic fluorosis and the geological environment as well as the prevention measures in Dali County, Shaanxi Province

Abstract：In order to study the relationship between the endemic fluorosis disease and the geological environment in Dali County, Shaanxi Province, the authors carried out a detailed statistical analysis of the group of patients suffering from fluorosis, and collected groundwater, soil, crop and vegetable samples for the determination of fluorine content. It is found that fluorine content of loess and saline soil is lower than that of clay，but the water-soluble fluoride of the former is higher than that of the latter, and the higher the alkaline, the higher the ratio of water-soluble fluoride to perfluoro. Fluorine content of unit mass of vegetables such as spinach and Indian lettuce is higher than that of wheat and corn. Fluoride in groundwater is concentrated in areas where hydrodynamic action is weak and salinity is high. Such fluoride comes mainly from the primordial rock, loess and clay. Areas with severe endemic fluorosis are located at the edge of low-lying land and the conversion position from steep slope to gentle slope. High prevalence of fluorosis patients is not only related to fluorine content of atmosphere, crops and vegetables, but also associated with fluoride content of groundwater. Based on these characteristics, the authors suggest that the methods for preventing and controlling endemic fluorosis disease should lie in the strengthening of exploitation and consumption of low-fluoride groundwater as well as the growing of low-fluoride crops. In addition, physical and chemical means should be employed to reduce the fluorine content of groundwater so as to reduce the prevalence rate of the endemic fluorosis disease in this area.