1. ^aResearch Center for Environmental Changes, Academia Sinica, Nankang, Taipei, Taiwan
2. ^bDepartment of Public Health, College of Health Care and Management, Chung Shan Medical University, Taichung, Taiwan
3. ^cDepartment of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan

Correspondence: Professor S.-C. C. Lung, Research Center for Environmental Changes, Academia Sinica, No. 128, Sec. 2, Academia Rd, Nankang, Taipei Tel.: +886 2 26539885 ext. 277; Fax: +886 2 27833584; E-mail: sclung@rcec.sinica.edu.tw

Received 28 June 2006; Accepted 9 February 2007; Published online 4 April 2007.

Abstract

Tea is the second most commonly consumed drink in the world. Excess fluoride intakes from tea drinks may cause health effects. This work assesses infusible fluoride levels in popular tea sold in Taiwan and evaluates potential exposure factors. Lungjing, pouchong, tienguanyin, oolong, pureh, and black tea specimens were purchased from different counties in Taiwan. Fluoride levels were evaluated in one complete cycle of tea making as well as at different calcium carbonate contents in water, with glass or porcelain teapots, and with/without adding sugar. Oolong tea leaves in each manufacturing step were also analyzed for infusible fluoride. Potential fluoride intakes and risks are estimated based on a national survey. Among six kinds of tea, black tea had the highest fluoride concentrations (8.642.96 mg/l), whereas pureh (1.972.70 mg/l) had the lowest levels. Higher percentages of infusible fluoride can be rinsed away from tea leaves curved lengthways compared to those curved end-to-end in the first 2.5 min. The use of glass or porcelain teapots and calcium carbonate content (up to 400 mg/l) in water would not affect infusible fluoride levels, whereas adding sugar increased the infusible fluoride in the first few minutes. In addition, it was found that the critical step during the manufacturing process affecting the percentage of infusible fluoride was ball rolling rather than fermentation. Furthermore, intakes of high amounts (5 l/week) of certain tea may result in excess risks of dental or skeletal fluorosis. Tea lovers could be exposed to excess fluoride and may be at risk of fluorosis.