Fluoride exposure in the endemic fluorosis area of Guizhou, China

Abstract

The dental and skeletal fluorosis is highly prevalent in Zhijin, Guizhou, especially at Hualuo Village, Hehua Village and Majiazhuang Village. The contents of fuorine in coal, clay used for coal combustion, mixed fuel of coal and clay, corn, and chili from households of the three villages were determined by the pyrohydrolysis-fluorine ion-selective electrode method. The average contents of fluorine in the above samples respectively are 237 mg/g, 2262 mg/g, 828 rag/g, 1419 mg/g, and 110 mg/g. The clay used for coal combustions is the main fluorine source of endemic fluorosis and the inferior coal and weathered coal are the secondary source of fluorine. During the combustion of mixed fuel of coal and clay, about eighty percent of fluorine was volatilized, approximately two thirds of which was from the clay and the other one third from the coal. The occurrence of fluorine in clay used for coat combustion is closely related to apatite and hornblende. The contents of fluorine in corn and chili, dried by coal-clay mixed fuel are about 1400 and 73 times higher than the permitted level of fluorine in foods according to the Chinese Standard. It is worth paying attention to the high-fluorine indoor surroundings, such as coal, clay, corn, and chili, particularly ash from boiler bottom with the fluorine content of 15738 ~g/g. Besides the technologies of fluorine fixation during the combustion, changes in living habits of the residents will help reduce the fluorine absorption, for example, washing the corn and chili before eating and improving the ventilation condition.