[Fluoride in the environment and brick-tea-type fluorosis in Tibet].

To explore whether endemic fluorosis in Tibet is related to local factors, an epidemiological survey of fluorosis was conducted in 3 districts in Tibet. The survey used the WHO and FAO established "Guideline for the study of dietary intake of chemical contaminants" and the Horowitz suggested criteria for children dental fluorosis examination. The fluorine in the local environment of the 3 selected districts was studied in detail. The possible fluorine sources examined indicated that only the brick-tea carried a high content of fluoride; water, other food materials, and fuel contents were insignificant. The children daily fluorine intake was high, where Naqu was 8.03 mg, Lahsa was 6.93 mg, Dingri was 7.68 mg. All the dietary fluoride was come from the brick-tea processed foods: the buttered-tea and zamba, these two contributed 99.74%, 98.70% and 99.60% of their daily fluorine intake respectively. The dental fluorisis index indicated that Naqu and Dingri were severe epidemic and Lahsa was moderate epidemic. The endemic fluorosis that occurs in Tibet was essentially due to heavy consumption of foodstuffs prepared with brick-tea, however, the high altitude, harsh living conditions, and poor nutritional status aggravated the fluorosis. Brick-tea type fluorosis is a new type of fluorosis recently discovered in China. Compared with the drinking water type and coal combustion type of fluorosis, it covered extensive area, more covert, and difficult to control. Decrease the fluorine content of brick-tea might be the most promising measure.