Safety evaluation and fluorine concentration of Pu'er brick tea and Bianxiao brick tea.

Pu'er brick tea and Bianxiao brick tea are both compressed types of tea. Fluorine analysis was carried out on samples of Pu'er brick tea produced at different times in Yunnan Province and on samples of Bianxiao brick tea made in Hunan and Sichuan Province for supply especially to minority ethnic groups in border areas of China. The levels of water-soluble and water-insoluble fluorine were measured in the tea samples using an ion-specific electrode potentiometer. The concentration of water-soluble fluorine was much greater in Bianxiao brick tea than in Pu'er brick tea (mean levels 441 and 77 mg/kg, respectively). According to these figures, the fluorine intake associated with consuming an infusion of 30 g Pu'er brick tea/person/day is safe because it does not exceed the maximum recommended daily allowance (RDA) of up to 4.0 mg for adults. In contrast, the almost six times higher intake of fluorine from Bianxiao brick tea greatly exceeds the 4 mg RDA and is unsafe. The difference in the fluorine levels of the two types of brick tea can be attributed to differences in the materials used to make them: Pu'er brick tea is made from tender leaves whereas Bianxiao brick tea is made from old tough leaves in which fluorine has accumulated. We conclude that consumption of Pu'er brick tea is unlikely to induce fluorosis, which has been associated with consumption of Bianxiao brick tea.