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ABSTRACT: Chronic exposure to the fluoride ion (F) can result in multisystem morbidity including skeletal fluorosis. The aim of this study was to investigate the relationship between urinary F levels and the daily intake of F in brick tea type fluorosis areas. The F levels were measured in brick tea infusions in six villages in Qinghai and five villages in Sinkiang, where the average intake of F from brick tea was >3.5 mg F/day and in which some residents had been diagnosed with having skeletal fluorosis using the WS/192-2008 standard of China. In addition, measurements were made of spot urine samples from the participants, who were aged over 16 yr, were born in the villages, and who continued to live in them. We found that differences may exist between Tibetans and Kazakhs in their F absorption and their sensitivity to F-induced damage. Although there was, in general, a significant positive correlation between the urinary F level and the daily intake of F from brick tea, this relationship was not consistently present when the subjects were stratified by ethnicity, age, and the presence or absence of skeletal fluorosis.
Keywords: Correlation; Fluoride load; Kazakhs; Tibetans; Urinary fluoride.
INTRODUCTION
Chronic exposure to the fluoride ion (F) can result in multisystem morbidity including skeletal fluorosis. Brick tea type fluorosis is a special type of fluorosis which is mainly found in the People's Republic of China.1 It is caused by the exposure, over a long period, to a high concentration of F in brick tea infusions.2 Over 30 million residents are threatened by brick tea type fluorosis and it is a serious public health problem. The affected residents are mainly the minority who follow the custom of drinking brick tea.3 The concentration of F in the water of a brick tea infusion is well above the concentration of F in drinking water and food.4 The F in the water of a brick tea infusion is the main source of the F exposure in the brick tea type of fluorosis 5.
It is estimated that approximately 36% of the F absorbed by adults becomes associated with the skeleton, while the rest is excreted in the urine. The level of urinary F excretion reflects the physiologic balance determined by the previous...