Fluoride exposure from burning coal-clay in Guizhou Province, China

The very high prevalence of dental and skeletal fluorosis in relation to the fluorine content of local coal and clay was investigated in two rural regions with low water fluoride (Hualuo Village and Majianzhuang Village) of Guizhou Province, China. The fluorine content of coal in the two regions is considerably lower than the total fluorine content of the commonly used coal-clay (a mixture of coal and clay). The fluorine released from combustion of the coal itself accounts for less than 15% of the total fluorine emissions during the combustion of coal-clay, thereby indicating that the fluorine source that contaminates the food and air is mainly from the clay rather than the coal.