Fluoride contents in tea and soil from tea plantations and the release of fluoride into tea liquor during infusion

Tea Camellia sinensis (L.), a perennial shrub, is cultivated in acidic soils. It has been noted that the occurrence of fluorosis in some inhabitants of pastoral and semiagricultural, semipastoral areas of Sichuan Province, People's Republic of China, is due to drinking a large quantity of tea liquor made from brick tea. Brick tea is made from fallen leaves and old leaves, and is not a considered a quality tea. The fluoride (F) contents of tea bushes and soil samples collected from five plantations from Guangdong Province, People's Republic of China, were tested. Fluorine accumulated mainly in leaves, especially in fallen leaves. The F concentration in fallen leaves (0.6-2.8 mg/g) were higher than that in young leaves (0.3-1.0 mg/g). Their concentrations were related to the total F and extractable F contents in the top soil (0-20 cm): In addition, soil pH and extractable Al concentration also affected the F contents in soils and plant tissues. Two methods (repeated and continuous) of infusing tea were employed to brew 17 brands of tea leaves in six categories: green tea, black tea, oolong tea, pureh tea, brick tea and black tea from England and Sri Lanka. In general, F contents in the infusions accounted for 24 to 83% of the total F contents of the original tea leaf samples. The cumulative F contents detected in the tea liquor prepared by repeated infusion were slightly higher than those prepared by continuous infusion. Brick tea released an extremely high F content (7.34 mg/litre), when compared with release from black tea (1.89 mg/litre) or green tea (1.60 mg/litre). In order to prevent development of fluorosis, the maximum consumption of fu-brick tea and black brick tea should be 1.7 litres and 4.8 litres/day respectively. (C) 1999 Elsevier Science Ltd. All rights reserved.