Potential Exposure and Risk of Fluoride Intakes from Tea Drinks Produced In

Home , Black tea, Fermented tea, Taiwanese tea, Tieguanyin

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Potential exposure and risk of ﬂuoride intakes from tea drinks produced in Taiwan

SHIH-CHUN CANDICE LUNGa,b,c, HUI-WEN CHENGb AND CHI BETSY FUa,b aResearch Center for Environmental Changes, Academia Sinica, Nankang, Taipei, Taiwan bDepartment of Public Health, College of Health Care and Management, Chung Shan Medical University, Taichung, Taiwan cDepartment of Atmospheric Sciences, National Taiwan University, Taipei, Taiwan

Tea is the second most commonlyconsumed drink in the world. Excess fluoride intakes from tea drinks maycause 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 (8.6472.96 mg/l), whereas pureh (1.9772.70 mg/l) had the lowest levels. Higher percentages of infusible fluoride can be rinsed awayfrom tea leaves curved lengthwayscompared 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 (Z5 l/week) of certain tea mayresult in excess risks of dental or skeletal fluorosis. Tea lovers could be exposed to excess fluoride and maybe at risk of fluorosis. Journal of Exposure Science and Environmental Epidemiology (2008) 18, 158–166; doi:10.1038/sj.jes.7500574; published online 4 April 2007

Keywords: tea drink, ﬂuoride, exposure assessment, risk assessment, beverage intake.

Introduction severe skeletal problems (WHO, 2001, 2002). A higher prevalence of overall bone and hip fractures were observed in Fluoride is ubiquitous in the environment. An appropriate areaswithwaterfluoridelevelshigherthanorequalto intake of fluoride is beneficial in preventing dental caries. 4.32 mg/l (Li et al., 2001). In addition, children living in the However, an excessive intake of fluoride might have adverse endemic fluoride village in China (water supply ¼ 4.12 mg effects. In Norway, high fluoride concentrations (Z0.50 F/l) showed statisticallysignificantlylower IQ scores than mg/l) in drinking water were statisticallyassociated with an those in nonendemic areas (Zhao et al., 1996). Fluoride increased risk of dental fluorosis (odd ratio: 18.9, 95% CI: toxicityin human kidneycollecting duct cells is also 8.85–40.44, Bardsen et al., 1999). Similar observations were documented (Cittanova et al., 1996; Klaassen, 2001). Thus, reported in the US, Canada, Chile, and other countries the potential risk of excess fluoride intake is a real concern. (Ismail and Messer, 1996; Karthikeyan et al., 1996; Villa Although not lethal, the effect of excessive fluoride intake et al., 1998; Kumar and Swango, 1999). Erdal and can have serious consequences. Bone fractures in aged people Buchanan (2005) stated that some children in the US may mayreduce their activitylevels, confine them to wheelchairs be at risk of dental fluorosis considering multi-pathway or to beds, make them dependent on long-term care from fluoride intakes. Morgen et al. (1998) reported that 69% of familyor professional nurses, and reduce their life quality children 7–11 years of age examined in a suburban Boston and expectancy(Shyuet al., 2004). It will also affect the life pediatric practice were found to have dental fluorosis. qualityof their familyand increase their psychological Ingestion of excess fluoride leads to dental effects, and burden, resulting in substantial societal costs and leading to long-term ingestion of large amounts can lead to potentially serious public health problems (Lin and Lu, 2005). Levels of dailyexposure to fluoride depend on the 1. Address all correspondence to: Professor S.-C. C. Lung, Research geographical area, if diets contain tea, exposure maybe Center for Environmental Changes, Academia Sinica, No. 128, Sec. 2, particularlyhigh (WHO, 1996). High concentrations of Academia Rd, Nankang, Taipei Tel.: þ 886 2 26539885 ext. 277. fluoride have been reported in the tea drinks of India, Tibet, Fax: þ 886 2 27833584. E-mail: [email protected] Received 28 June 2006; accepted 9 February2007; published online 4 China, and Taiwan (Gulati et al., 1993, 1.55–3.21 mg/l; April 2007 Cao et al., 1996, 2.5971.73 mg/l; Fung et al., 1999, Fluoride intake and potential risk from tea drinks Lung et al.

1.60–7.34 mg/l; Lung et al., 2003, 3.16–33.4 mg/l). Next to Methods and materials water, tea is the most commonlyconsumed drink in the world (Manil and Zbinden, 2001). In 1981, world produc- Sampling Strategy tion of tea amounted to 2,033,000 tons. Taiwan was then Using tea leaves rather than tea bags is the traditional wayof the seventh largest exporter of tea in the world (Manil and tea making. Tea leaves from different growth areas have Zbinden, 2001). The exporting quantityhas been decreasing slightlydifferent production processes resulting in different in recent years. In 2004, Taiwan exported 2388 tons of tea to characteristics. The most popular kinds of teas in Taiwan at least 17 countries, including the US, Canada, the UK, were selected, including lungjing (unfermented), pouchong China, Australia, etc. (TTPIA, 2006b). People around the (lightlysemi-fermented, 20% fermentation), tienguanyin world consume tea produced in Taiwan. In addition, as tea (semi-fermented, 50–60% fermentation), oolong (semi-fer- drinking has been a long tradition in our culture, Taiwanese mented, 60–70% fermentation), pureh (semi-fermented, consume tea drinks frequentlyand in considerable amounts. 60–70% fermentation), and black tea (fullyfermented) Manyfamilies drink tea rather than water as their primary (Huang, 1991; Manil and Zbinden, 2001). Pureh goes through means of fluid intake. According to the ‘‘Nutrition and a post-fermentation process; thus, the fermentation degree Health Surveyin Taiwan’’ conducted in 1993–1996 on 4964 varies greatlyamong different production areas and is greater men and 4998 women, the mean tea-drinking frequencyof than the initial fermentation degree (60–70%) (Lai, 2003). all subjects were higher than 4 times/week, except for women To assess fluoride contents of tea leaves produced from in the group of 65 þ . Men in the age of group 45–64 had the various plantation areas in Taiwan and consumed bythe highest tea drinking frequency, 9.7718.4 times/week (Pan majorityof Taiwanese, nine counties were selected to be the et al., 1999; Tzeng et al., 1999). specimen-purchasing area. The plantation areas of these nine Traditionally, tea can be classified according to the degree counties account for 83% of the plantation area in Taiwan of fermentation, namelyunfermented (green tea), semi- (TTPIA, 2006a), and the population of these areas accounts fermented, and fullyfermented (black tea) for 0%, 10–70%, for nearly75% of the Taiwanese population (DGBAS, and 80–100% fermentation, respectively(Huang, 1991; 2005). Several tea stores in the center of one particulate Manil and Zbinden, 2001). Green tea is traditionallythe countywere randomlychosen initiallyas theyusuallyhave most popular kind of tea in Asian countries, whereas semi- higher sales volumes compared to stores in other locations. fermented tea such as oolong, produced in large quantities The clerks of these stores were asked whether the store in Taiwan, is also well liked byTaiwanese. Black tea is carried the above-mentioned six kinds of tea and where the traditionallyverypopular in western countries. In recent tea was grown. One store was selected in each countywhich years, the consumption of black tea has been increased carried the most kinds of the above-mentioned tea grown among young people in Taiwan, especially at afternoon locally. Specimens of each kind of tea were purchased there. teatime. Taiwan produces all three classes of tea (unfermented, Nevertheless, not all plantation areas grow all kinds of tea semi-fermented, and fullyfermented) for both local sales and leaves; we purchased tea specimens preferablygrown locally, for export (TTPIA, 2006b). or at least produced in Taiwan if not grown locally. The Kanis et al. (2002) categorized Taiwan as one of the exception was pureh that was mostlyimported from China. high-risk countries in the world in term of hip fracture In addition, stores in these nine counties did not carryall six probability. In 1996–2000, the age-adjusted incidence kinds of tea leaves; thus, onlyeight specimens of lungjing and rates of hip fracture were 225 (95% CI: 188–263) per pouchong were obtained. 100,000 in men and 505 (95% CI: 423–585) per 100,000 in women in Taiwan, as compared with US white rate of Extraction and Analysis 187 in men and 535 in women (Chie et al., 2004). Owing An amount of 2.5 g of tea leaves was added to a glass tea to the tea drinking tradition in Taiwan, fluoride intake maker and 150 m of hot deionized water (95–981C) was via tea consumption is doubtlesslyone of the important added to simulate the traditional wayof tea brewing. As the risk factor of hip fracture. Although a varietyof tea usual tea-brewing time is 2–3 min (Huang, 1991), the tea drinks are consumed, there have been few studies focusing infusion was filtered into a sample vial for analysis after on the fluoride intake from them. Therefore, we conducted 2.5 min. As tea drinkers normallydrink up to four rounds, this studyto assess fluoride concentrations in popular tea this procedure was repeated three more times to collect tea drinks sold in Taiwan. Concentration differences infusions from the second, third, and fourth round as among them and potential influential factors were assessed. separate samples (Figure 1). The ‘‘infusible fluoride’’ referred In addition, tea leaves were collected during the manufacturing to in this work is defined as the fluoride content infused process and analyzed in order to identify the critical within one complete cycle of tea making (four rounds), step affecting the percentage of infusible fluoride. 10 min. Intake levels and potential risks were also estimated and A fluoride standard was purchased from Merck (Merck discussed. KgaA, Darmstadt, Germany). A fresh calibration curve was

Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) 159 Lung et al. Fluoride intake and potential risk from tea drinks

Add Add reported; thus, we assessed the effect of adding sugar on 150ml 150ml water 2.5 water 2.5 fluoride levels. Small sachets of sugar with a mean weight of minutes minutes 1.43 g of the most popular brand were purchased from a The Second Tea The First round round supermarket in Taipei. One, two, three, and four sachets of leaves sugar were added to separate black tea drinks and the same experimental procedures were followed. Fluoride levels from Add Add 150ml 150ml these tea infusions were assessed to compare with those in water 2.5 water 2.5 minutes minutes black tea infusions without sugar. The Third The Fourth round round Assessment of Critical Steps Affecting Fluoride Infusion Figure 1. Process of making one complete cycle of tea drinks (four The major determinants of fluoride infusible from tea leaves rounds). are the original fluoride content and the infusible percentage. The original content of fluoride in leaves depends largelyon the soil fluoride content of the growth area, which is not a prepared for each batch. The linear correlation of calibration controllable factor. On the other hand, tea leaves go through curve (R) was larger than 0.999 for all the calibration curves. manymanufacturing steps before being sold on the markets Fluoride was analyzed with Dionex DX120 Ion Chromato- and fermented tea leaves go through more steps than graphy(Dionex Corp., Sunnyvale, CA, USA) with AS12A unfermented ones. It is interesting to know the critical steps s column (IonPac 4*200 mm). The eluent was 0.2 mM during the manufacturing process, which might be respon- NaHCO3 and 1.8 mM Na2CO3 with 1.0 ml/min. sible for enhancing the infusible percentage of fluoride. A tea farm in Nantou County, which has the largest tea Assessment of Potential Factors plantation area in Taiwan, was invited to participate in this Natural water mayhave different degrees of hardness, which studyto assess the infusible fluoride from tea leaves in each is usuallyexpressed as the concentration of calcium manufacturing step. Oolong tea is grown on this farm. The carbonate. The standard of hardness for drinking water in manufacturing process for oolong tea leaves includes picking, Taiwan is 300 mg/l of calcium carbonate in water (TEPA, solar withering, indoor withering, panning, fermentation, 2005). Different degrees of hardness represent different ion rolling, primarydrying, ball rolling, roasting, and finalizing strengths of the solution, which mayinterfere with fluoride the product (Manil and Zbinden, 2001; TRES, 2002). After infusion. Thus, fluoride levels were assessed with 0, 75, 150, tea leaves had been picked from the trees, specimens of tea 300, and 400 mg/l of calcium carbonate in water with the leaves from each manufacturing step were reserved without same experimental and analytical processes. further processing. These specimens were selected randomly In addition, containers made of different materials may within this batch of tea leaves. Later 80 tea leaves were have different influences on infusible fluoride. Fluoride may randomlyselected from these specimens and divided into four adsorb on the surfaces of containers and that mayinduce samples. As the final product is dry, the water content of tea more fluoride infused from tea leaves. The effects of different leaves decreases during the manufacturing process. Thus, one containers on fluoride were examined. In recent years, glass sample (20 tea leaves) of each step was weighed, baked at tea makers have become increasinglypopular; therefore, 801C for 72 h, and reweighed to assess their original water glass tea makers were used in the experimental procedures in contents. Three samples of 20 tea leaves from each step went this work. However, porcelain and potteryteapots are used through the same tea making process to examine the infusible in traditional tea making. It has been reported that there amounts of fluoride in one complete cycle of tea making (four was no difference in fluoride concentrations byusing glass or rounds, 10 min). potterytea makers (Lung et al., 2003). Thus, we only assessed fluoride levels in tea infusions in glass and porcelain QA/QC containers. One sample (5 g) of tea leaf was divided into two The mean values of blanks were 0.2870.04 mg/l (n ¼ 29). subsamples. One was added to a porcelain teapot and The presented results in this work have all been another to a glass tea maker. Fluoride levels were assessed via blank corrected. The method detection limit (MDL) based the same experimental process mentioned above. on the variation of blanks, was 0.12 mg/l. The Moreover, some people drink black tea with sugar and sample concentrations in this work were all higher than the milk. Gulati et al. (1993) had assessed the effect of adding MDL. Deionized water was spiked with known concentra- milk and reported that there is no difference between levels of tions and taken through the extraction and analysis fluoride with or without addition of milk in the English style procedures to assess recovery. The percentage of recovery where tea leaves are not boiled, whereas, for the Indian style, rates was 97.8%71.4% (n ¼ 5). Variations of repeated addition of milk and subsequent boiling resulted in reduction measurements were within 3.1%, and those of triplicate of fluoride levels. However, no effect regarding sugar was samples were 8.6% and 4.4% for samples around 0.8 and

160 Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) Fluoride intake and potential risk from tea drinks Lung et al.

2.5 ppm, respectively. All samples were analyzed on the same fluoride from tea leaves curved lengthways than those curved dayof extraction. end to end. In this work, the first run was set for 2.5 min; however, it Exposure and Risk Assessment usuallytakes only0.5 min to rinse tea leaves. Assuming the The health risks were assessed with hazard quotient (HQ) for fluoride infusion from 0 to 2.5 min was a linear relationship objectionable dental fluorosis and margin of safety(MOS) with time, it was estimated that on average 11.7%, 9.6%, for crippling skeletal fluorosis. The equations are as follows: 9.7%, 8.0%, 11.5%, and 12.0% of fluoride were infused in

Cavgðmg=lÞÂTðl=weekÞÂ52ðweeks=yearÞ the first 0.5 min for lungjing, pouchong, tienguanyin, oolong, HQ ¼ pureh, and black tea drinks, respectively. That is, 8–12% of WpðkgÞÂ365ðday=yearÞÂRfDðmg=kg=dayÞ infusible fluoride would not be consumed if tea drinkers rinse for objectionable dental fluorosis ð1Þ tea leaves for 0.5 min. The fluoride concentrations in six kinds of tea drinks 7 7 NOAELðmg=lÞÂ2ðl=dayÞ averaged over four rounds were 6.28 2.14, 4.65 1.20, MOS ¼ 7.3072.40, 6.8771.60, 1.9772.70, and 8.6472.96 mg/l for Cavgðmg=lÞÂTdðl=dayÞ lungjing, pouchong, tienguanyin, oolong, pureh, and black for crippling skeletal fluorosis ð2Þ tea drinks, respectively(Figure 3). If the leaves were rinsed where Cavg is the mean fluoride concentration of tea drinks, T for 0.5 min, the corresponding fluoride levels were is the average amount of weeklytea intake in Taiwan, Wp is the typical bodyweight (65 kg) for Taiwanese adults; and 120 RfD is 6 Â 10À2 mg/kg/dayof fluoride for objectionable dental fluorosis (USEPA 1989a); it is an estimate of daily 100 exposure to that part of the population that is likelyto be without an appreciable risk of deleterious effects during their 80 lifetime. Thus, HQ o1 represents that dailyintake which is lungjing (n=8) unlikelyto result in objectionable dental fluorosis in the long pouchong (n=8) 60 run. The no-observed-adverse-effect level (NOAEL) for tienguanyin (n=9) oolung (n=9) crippling skeletal fluorosis is 4ppm assuming a dailyintake 40 pureh (n=9) of 2 l of fluids (USEPA, 1989a). MOS larger than 1 means black (n=9) that no crippling skeletal fluorosis would be expected in this fluoride percentage (%) 20 population. Both HQ and MOS are unitless.

0 1234 round Results and discussion Figure 2. The percentage (mean7SD) of fluoride infused in different rounds of tea drinks. Fluoride Concentration in Six Kinds of Tea Drinks A total of 52 tea specimens were purchased from tea stores, and a total of 208 infusion samples were collected from one 20 L: lungjing (n=8) complete cycle of tea making (four rounds, Figure 1). Taking C: pouchong (n=8) fluoride infused in one complete cycle as 100%, the T: tienguanyin (n=9) percentages of fluoride infused in different rounds of drinks 15 O: oolong (n=9) P: pureh (n=9) are plotted in Figure 2. The percentages of fluoride infusion B: black (n=9) in the first round could varyfrom less than 40% to around 60%. During the experiments, it was observed that tea leaves 10 curved end-to-end usuallytook longer to expand. Fluoride maybe infused slowlyin this kind of tea leaves. Therefore, tea leaves were divided into two groups: curved end-to-end 5

(tienguanyin, oolong, and one specimen of pouchong) and fluoride (mg/l) concentration curved lengthways (lungjing, pureh, black, and seven specimen of pouching). The result of Wilconxon rank sum test 0 LCTOPB showed that tea leaves curved lengthways indeed had a higher tea percentage of ﬂuoride infused in the ﬁrst round (P ¼ 0.0004). Figure 3. Fluoride concentrations (mg/l) in six different kinds of tea Some people use hot water to rinse tea leaves before making drinks without rinsing tea leaves; middle lines represent median values; tea. Our results suggest that this practice rinses awaymore dots represent 5%/95% percentiles.

Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) 161 Lung et al. Fluoride intake and potential risk from tea drinks

5.5471.76, 4.2071.01, 6.5972.05, 6.3271.47, 1.7472.39, Table 1 . The effect of different concentrations of calcium carbonate in and 7.6172.46 mg/l, respectively. Black tea drinks had the water (mg/l) on the fluoride levels (mg/l) in tea infusions of black tea highest mean concentrations of fluoride with or without drinks. rinsing. In addition, our results show that fluoride levels in tea infusions are not different according to the degree of Calcium carbonate in water (mg/l) fermentation. It also shows a certain degree of variation Time (min) 0 75 150 300 400 Mean SD %CV among tea samples obtained from different locations. As soil fluoride content would affect fluoride concentrations in tea 2.5 7.71 8.19 6.67 8.57 8.25 5 6.77 7.99 10.3 8.90 7.67 leaves (Fung et al., 1999), varied infusible fluoride contents in 7.5 1.63 1.71 1.92 2.42 2.86 tea leaves from different growing areas are anticipated. 10 1.06 0.71 0.84 0.64 1.49 Among these six kinds of tea drinks, pureh had the largest Total fluoride variation. This is because samples purchased from central Infusion 17.2 18.6 19.7 20.5 20.3 19.3 1.38 7.2% Taiwan had about 6B9 times the concentrations of the other pureh samples. Some of the purchased pureh samples were packed in brick form (so-called brick tea). Previous studies showed that brick tea infusion contained a high fluoride strength of water was not strong enough to affect infusible content (Fung et al., 1999, 7.34 mg/ml). However, brick tea fluoride levels in tea drinks. could be made from either compacted fine broken tea leaves or from whole leaves (Manil and Zbinden, 2001). Gulati Influence of Containers et al. (1993) reported that leaching of fluoride was increased The percentages of coefficient of variance (%CV) between with decreased grain size. All pureh samples in this study samples from the glass and porcelain teapots were 4.3%, (including those in brick form) were whole-leaf samples. 4.0%, 4.5%, 4.0%, 22.7%, and 28.6% for lungjing Thus, our results did not show such high concentrations, (5.5970.24 ppm), pouching (3.3670.13 ppm), tienguanyin except for those from central Taiwan. The samples purchased (5.5670.25 ppm), oolong (4.4270.18 ppm), pureh from central Taiwan were grown in central Taiwan, as (1.3770.31 ppm), and black tea drinks (7.1272.04 ppm), opposed to the others imported from mainland China. The respectively. The variation of the first four tea drinks was result of the Wilcoxon rank sum test showed that pureh close to the variation of triplicate samples, while the large grown in Taiwan had significantlyhigher fluoride concentra- variation of pureh was mainlydue to the low fluoride tions (6.04 and 5.35 mg/l for drinks without and with rinsing, concentrations. In addition, previous studyshowed that respectively) than those from mainland China (0.82 and fluoride infused from black tea did have higher variation 0.73 mg/l for drinks without and with rinsing, respectively) compared to other tea drinks (%CV of black tea was up to (Po0.05). The different ways of tea-leaf processing and 20%, Lung et al., 2003); this mayaccount for high variation different fluoride contents of the growth areas might explain of black tea in this experiment. Thus, our results suggest that this discrepancy. the use of glass tea makers or porcelain teapots would not The Kruskal–Wallis’s test and Scheffe test were used to affect fluoride levels in tea infusions for these tea leaves. compare fluoride concentrations among the six kinds of tea drinks. For tea drinks without rinsing, black tea had higher Influence of Sugar on Black Tea Drinks fluoride levels than pouchong and pureh (Po0.05). In Fluoride concentrations in tea infusions at 2.5, 5, 7.5, and addition, the fluoride levels of pureh were significantlylower 10 min for black tea with no, one, two, three, and four sugar than those in lungjing, tienguanyin, oolong, and black tea sachets are presented in Figure 4. Larger variations were seen drinks (Po0.05). For tea drinks with rinsing, pureh tea had in fluoride in black tea with no and one sugar sachet. the lowest fluoride concentrations compared to those in the Nevertheless, it shows that less fluoride (50–100% less) was other five kinds of tea drinks (Po0.05). infused in black tea with no sugar in the first 2.5 min. From 5 to 10 min, the infusion of fluoride did not show significant Influence of Calcium Carbonate differences among black tea with or without sugar. The According to the results in the last section, black tea had the total amounts of infusible fluoride in one complete round highest fluoride concentrations. Therefore, black tea samples with no, one, two, three, and four sugar sachets were were used in the assessment of water hardness. Table 1 shows 2.1070.22, 4.5270.5, 3.5270.04, 4.3470.37, and less than 8% variation of infusible fluoride in tea samples 4.5270.09 mg. The %CV of fluoride among infusions with with different calcium carbonate contents in water. The one to four sugar sachets were 11%. The average fluoride in variation was close to the variation of triplicate samples. In infusions with anyamounts of sugar (one to four sachets: Taiwan, the criterion of hardness for drinking water is 4.2270.48 mg) were about twice of those in infusions 300 mg/l. Our results suggest that, even with a high degree of without sugar (2.1070.22 mg). In summary, our results hardness (300 and 400 mg/l of calcium carbonate), the ion suggest that adding sugar increases the fluoride infusion from

162 Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) Fluoride intake and potential risk from tea drinks Lung et al.

30 a 0.9 zero (n=3) one (n=2) two (n=2) 0.8 25 three (n=2) Four (n=2) 0.7 0.6 20 0.5 0.4 15 0.3 0.2 0.1 10 fluoride (mg/g tea-leaf) 0.0 fluoride (mg/L)

rolling asting picking 0 panning ro 2.55 7.5 10 ball rolling fermentation final product

primary drying time (minutes) solar withering indoor withering Figure 4. Fluoride concentrations (mg/l) at 2.5, 5, 7.5, and 10 min in process black tea infusions with no, one, two, three, and four sugar sachets. b 80 70 60 50 black tea leaves and the excess infusion occurs primarilyin 40 30 the ﬁrst few minutes. 20 10 water content (%) water Critical Steps Affecting Infusible Fluoride During the 0

t g g g g g n g g g c n n n n n Manufacturing Process n i o n i n i i i i i i i u r l r t l l t k n l y d r e e a s c n o o i t r o Fluoride levels in oolong tea leaves of each manufacturing h h r d a r t t a n p i i l o y l p p r e r step are plotted in Figure 5(a). It is clear that the infusible w w a l a r r m b a r n a o m l e i i f fluoride per gram of tea leaves in 10 min (one complete cycle o f r o d s p n of tea making) stayed almost constant during the first six i steps, and increased slightlyafter rolling and greatlyafter ball process rolling. Rolling and ball rolling aim at breaking tea-leaf cells Figure 5. (a) Fluoride concentrations (mg/g, n ¼ 3) and (b) water and releasing their essential oils, whereas fermentation contents in oolong tea leaves during each manufacturing step. involves a series of complex chemical reactions that cause leaves to blacken (Manil and Zbinden, 2001). Tea leaves grown in the same area, such as specimens collected for this experiment, presumablyhave similar original fluoride con- mainlyresponsible for the enhancement of the infusible tents (from soil). Our results showed that fermentation does percentage of fluoride, are the physical processes such as ball not enhance the infusible percentage of fluoride; it is physical rolling. processes such as rolling and ball rolling that damage leaf tissues and increase the infusible percentage of fluoride. The Exposure and Risk Assessment of Fluoride Intakes from breakdown of leaf tissues incurred in these two steps are also Tea confirmed bythe loss of water contents of tea leaves, which In the ‘‘Nutrition and Health Surveyin Taiwan’’ conducted decreased evidentlyafter rolling and ball rolling (Figure 5b). in 1993–1996 on 4964 men and 4998 women subjects, the tea As all tea leaves, including unfermented, semi-fermented, and drinking frequencies for men subjects age groups 13–18, fullyfermented, go through a certain typeof rolling (Manil 19–44, 45–64, and 65 þ were 5.7710, 8.8722.3, 9.7718.4, and Zbinden, 2001; TRES, 2002), their tissues are damaged and 7.2715.7 times/week, respectively; and the correspond- to a certain degree and thus fluoride is prone to be infused in ing tea drinking frequencies for women were 4.176.3, water, regardless the fermentation degree. This can explain 5.6711.9, 4.9710, and 2.7710.5 (Pan et al., 1999; Tzeng whythe fluoride concentrations in the six kinds of tea drinks et al., 1999). The average frequencyin each age group was assessed in this work were not different according to the used as a central tendencyexposure (CTE) estimation, and degree of fermentation. Nevertheless, different manufacturers three times the SD plus the average frequencyin each age process tea leaves in slightlydifferent ways; it is during this group was used as the estimation for the reasonable process that different types acquire their different character- maximum exposure (RME) to represent a plausible worst- istics and personality(Manil and Zbinden, 2001). Therefore, case scenario (USEPA, 1989b). Assuming people consume our results based on specimens from one tea farm byno 200 ml of tea each time, it was found that CTE were from means represent all the processes. Nevertheless, it clearly 0.54 to 1.94 /week and those of RME were from 4.60 to points out that the critical steps in the process, which are 15.1 l/week for different age groups. In addition, people may

Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) 163 Lung et al. Fluoride intake and potential risk from tea drinks

Ta bl e 2 . Mean fluoride intakes (mg/week) based on fluoride levels in Table 3 . Potential risks expressed as (a) HQ for dental fluorosis and various tea samples and tea-drinking quantities. (b) MOS for skeletal fluorosis based on mean fluoride levels.

CTE (l/week) RME (l/week) CME (l/week) RME (l/week)

Rinsing 0.5 1 2 5 10 15 20 Rinsing 0.5 1 2 5 10 15 20

Lungjing No 3.14 6.28 12.6 31.4 62.8 94.2 126 (a) Yes 2.77 5.54 11.1 27.7 55.4 83.2 111 Lungjing No 0.1 0.2 0.5 1.1 2.3 3.4 4.6 Pouchong NO 2.33 4.65 9.31 23.3 46.5 69.8 93.1 Yes 0.1 0.2 0.4 1.0 2.0 3.0 4.1 Yes 2.10 4.20 8.41 21.0 42.0 63.1 84.1 Pouchong No 0.1 0.2 0.3 0.9 1.7 2.6 3.4 Tieguanyin NO 3.65 7.30 14.6 36.5 73.0 110 146 Yes 0.1 0.2 0.3 0.8 1.5 2.3 3.1 Yes 3.30 6.59 13.2 33.0 65.9 98.9 132 Tieguanyin No 0.1 0.3 0.5 1.3 2.7 4.0 5.3 Oolong No 3.44 6.87 13.7 34.4 68.7 103 137 Yes 0.1 0.2 0.5 1.2 2.4 3.6 4.8 Yes 3.16 6.32 12.6 31.6 63.2 94.9 126 Oolung No 0.1 0.3 0.5 1.3 2.5 3.8 5.0 Pureh No 0.99 1.97 3.94 9.85 19.7 29.6 39.4 Yes 0.1 0.2 0.5 1.2 2.3 3.5 4.6 Yes 0.87 1.74 3.49 8.72 17.4 26.2 34.9 Pureh No 0.0 0.1 0.1 0.4 0.7 1.1 1.4 Black No 4.32 8.64 17.3 43.2 86.4 130 173 Yes 0.0 0.1 0.1 0.3 0.6 1.0 1.3 Yes 3.80 7.61 15.2 38.0 76.1 114 152 Black No 0.2 0.3 0.6 1.6 3.2 4.7 6.3 Yes 0.1 0.3 0.6 1.4 2.8 4.2 5.6

(b) Lungjing No 17.8 8.9 4.5 1.8 0.9 0.6 0.4 drink more than 200 ml each time. Some people use 500 ml Yes 20.2 10.1 5.0 2.0 1.0 0.7 0.5 mugs to drink tea and it is easyto purchase tea drinks with Pouchong No 24.1 12.0 6.0 2.4 1.2 0.8 0.6 500–600 ml in local stores in Taiwan. Therefore, 20 l/week is Yes 26.6 13.3 6.7 2.7 1.3 0.9 0.7 used as a reasonable estimation of Taiwanese RME tea Tieguanyin No 15.3 7.7 3.8 1.5 0.8 0.5 0.4 Yes 17.0 8.5 4.2 1.7 0.8 0.6 0.4 consumption. In the following exposure and risk assessment, Oolung No 16.3 8.1 4.1 1.6 0.8 0.5 0.4 the intake amounts are classified as 0.5, 1, 2, 5, 10, 15, and Yes 17.7 8.9 4.4 1.8 0.9 0.6 0.4 20 l/week, which cover a range of reasonable tea drinking Pureh No 56.9 28.4 14.2 5.7 2.8 1.9 1.4 quantities in Taiwan. The first three intake levels can be Yes 64.2 32.1 16.1 6.4 3.2 2.1 1.6 viewed as CTE for different age groups, while the rest are Black No 13.0 6.5 3.2 1.3 0.6 0.4 0.3 Yes 14.7 7.4 3.7 1.5 0.7 0.5 0.4 RME. The estimated fluoride intakes based on average fluoride Numbers in bold are HQ41orMOSo1. concentrations of the six kinds of tea drinks are shown in Table 2. The fluoride intakes for CTE are from o1 mg/week (pureh with 0.5 l/week) to 415 mg/week (black tea with shown in some samples analyzed here. Their fluoride intake 2 l/week), whereas those for RME could be up to 40–173 levels and potential risks would be higher than those mg/week depending on the types of tea drinks. estimated. Thus, 95 percentile of fluoride concentrations The potential health risks expressed as HQ and MOS are were calculated for the six kinds of tea and the potential presented in Tables 3a and b. People with CTE are free of the health risks are presented in Tables 4a and b. The results risk of dental fluorosis, whereas an intake rate of 10 l/week show that there is potential risk of dental fluorosis for people would be associated with potential dental fluorosis risk for of RME that consume more than 5 l/week of anyof the six consumers of studied tea types, except the pureh tea. In kinds of tea. Moreover, people who drink more than 5 l/week addition, MOSs of pureh lovers in CTE and RME groups black tea would encounter excess risks of crippling skeletal are higher than 1 (Table 3(b)); thus, no health effect is fluorosis; and consumers of the other five kinds of tea should expected for them, so as for the drinkers of the other five not drink more than 10 l/week in order to avoid such adverse kinds of tea in the CTE group. For lungjing tea lovers who health effects. rinse tea leaves and pouchong tea lovers, the fluoride intakes Taiwan also exports these teas to other countries, including are still in the safe range if theydrink up to 10 l/week. Canada, the US and the UK (TTPIA, 2006b). People Nevertheless, tea consumption of 10 l/week of tieguanyin, in these countries could also be exposed to these fluoride oolong, and black tea mayresult in excess risks of crippling levels from tea drinks. The mean tea intake per capita skeletal fluorosis. These consumers should lower their tea for adults in Canada, the US, and England are 1.5–3, 0.8– intakes to reduce the potential health risks. 1.2, and 4–4.5 l/week, respectively(Hopkins and Ellis, The estimation of fluoride intake levels and potential risks 1980; CMNHW, 1981; USDA, 1995). According to mentioned above were based on the mean concentrations Tables3aandband4aandb,theirrisksofdentaland obtained in this study. To be conservative, it is possible that skeletal fluorosis are slim with average intake levels; however, consumers could be exposed to higher fluoride levels as tea lovers in the UK who drink more than the average

164 Journal of Exposure Science and Environmental Epidemiology (2008) 18(2) Fluoride intake and potential risk from tea drinks Lung et al.

Ta bl e 4 . Potential risks expressed as (a) HQ for dental fluorosis and obtained from tea drinks and other sources such as tooth- (b) MOS for skeletal fluorosis based on 95 percentile of fluoride levels. paste. Caution should be taken in carrying out water fluoridation in Taiwan in order to avoid side effects. 95 percentile CME (l/week) RME (l/week)

Washing F(mg/l) 0.5 1 2 5 10 15 20 Conclusion (a) Lungjing No 8.9 0.2 0.3 0.7 1.6 3.3 4.9 6.5 This work presents the fluoride concentrations of six kinds of Yes 7.9 0.1 0.3 0.6 1.4 2.9 4.3 5.8 popular tea drinks in Taiwan; manyof them had not been Pouchong No 6.4 0.1 0.2 0.5 1.2 2.4 3.5 4.7 Yes 5.8 0.1 0.2 0.4 1.1 2.1 3.2 4.2 studied previously. The mean fluoride levels were 1.97– Tieguanyin No 11.2 0.2 0.4 0.8 2.1 4.1 6.2 8.2 8.64 mg/l; black tea had the highest fluoride concentrations. Yes 10.1 0.2 0.4 0.7 1.9 3.7 5.6 7.4 Exposure factors of infusible fluoride were evaluated. Rinsing Oolung No 8.9 0.2 0.3 0.7 1.6 3.3 4.9 6.5 tea leaves for 0.5 min can wash away8–12% of infusible Yes 8.2 0.1 0.3 0.6 1.5 3.0 4.5 6.0 fluoride; and higher percentages of infusible fluoride could be Pureh No 6.7 0.1 0.2 0.5 1.2 2.5 3.7 4.9 Yes 5.9 0.1 0.2 0.4 1.1 2.2 3.3 4.3 rinsed awayin tea leaves curved lengthways. Making tea with Black No 13.2 0.2 0.5 1.0 2.4 4.8 7.3 9.7 water containing different levels of calcium carbonate (up to Yes 11.6 0.2 0.4 0.9 2.1 4.3 6.4 8.5 400 mg/l) and with containers made of glass or porcelain did not affect the infusible fluoride in tea drinks. While adding (b) sugar in black tea increased the infusible fluoride in the first few Lungjing No 8.9 12.5 6.3 3.1 1.3 0.6 0.4 0.3 Yes 7.9 14.2 7.1 3.6 1.4 0.7 0.5 0.4 minutes. In addition, it was found that the manufacturing steps Pouchong No 6.4 17.4 8.7 4.4 1.7 0.9 0.6 0.4 responsible for the enhancement of the infusible percentage of Yes 5.8 19.3 9.7 4.8 1.9 1.0 0.6 0.5 fluoride is the physical processes such as ball rolling rather than Tieguanyin No 11.2 10.0 5.0 2.5 1.0 0.5 0.3 0.3 the chemical processes such as fermentation. Furthermore, Yes 10.1 11.1 5.5 2.8 1.1 0.6 0.4 0.3 intakes of high amounts (Z5l/week) of certain tea drinks may Oolung No 8.9 12.6 6.3 3.2 1.3 0.6 0.4 0.3 Yes 8.2 13.7 6.9 3.4 1.4 0.7 0.5 0.3 result in excess risks of dental or skeletal fluorosis. To avoid Pureh No 6.7 16.7 8.4 4.2 1.7 0.8 0.6 0.4 adverse effects, we suggest reducing fluoride intakes by YES 5.9 18.9 9.4 4.7 1.9 0.9 0.6 0.5 selecting teas with leaves curved lengthways, rinsing tea leaves Black No 13.2 8.5 4.2 2.1 0.8 0.4 0.3 0.2 before making tea, and drinking black tea without adding Yes 11.6 9.6 4.8 2.4 1.0 0.5 0.3 0.2 sugar. These studied tea drinks are probablyalso popular in Numbers in bold are HQ41orMOSo1. manyother countries. Governments should take tea drinking cultures into account before carrying out water fluoridation in order to avoid side effects. Drinking tea has certain relaxation amounts should be cautious about the potential dental and and soothing effects and it is enjoyed around the world. We skeletal fluorosis. would like to caution tea lovers to bear in mind the potential Furthermore, tea drinkers who like stronger tea brew the risks of excess fluoride intakes while enjoying tea. tea for a longer period of time (each round 42.5 min) or use more tea leaves. More fluoride would be infused in drinks with a longer preparation time and with more tea leaves; Acknowledgements thus, those tea lovers would consume more fluoride than these reported here. Besides, this work was conducted with This publication was made possible bygrant number deionized water; and fluoride concentrations in the drinking NSC90–2815-C-040–009-B from National Science Council water of Taiwan are from less than 0.01 to 0.28 mg/l (Yang (NSC), Republic of China. Its contents are solelythe et al., 2000). Thus, fluoride intakes in actual tea drinking responsibilityof the authors and do not necessarilyrepresent would be higher than the current estimations. the official view of the NSC. The optimal level for water fluoridation is between 0.7 and 1.2 mg/l, depending on the temperature of that area, prevent References dental caries (Galagan et al., 1957; Galagan and Vermillio, 1957b). According to the annual average of maximum daily Bardsen A., Klock K.S., and Bjorvatn K. Dental fluorosis among persons exposed temperature in Taiwan (74–771F, CWB, 1999), the optimal to high- and low-fluoride drinking water in western Norway. Commun Dent Oral Epidemiol 1999: 27: 259–267. fluoride concentration should be 0.8 mg/l for Taiwanese. Cao J., Bai X., Zhao Y., Liu J., Zhou D., Fang S., Jia M., and Wu J. The Recently, the Taiwan government has been considering relationship of fluorosis and brick tea drinking in Chinese Tibetans. Environ adding fluoride to drinking water to prevent dental caries. Health Perspect 1996: 104: 1340–1343. Chie W.C., Yang R.S., Liu J.P., and Tsai K.S. High incidence rate of hip fracture However, due to the high accessibilityof tea drinks in in Taiwan: estimated from a nationwide health insurance database. Osteo- Taiwan, it is verylikelythat sufficient fluoride is already porosis Int 2004: 15: 998–1002.

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