Environ Monit Assess (2013) 185:3687–3695 DOI 10.1007/s10661-012-2820-9

Health risk assessment of fluoride in drinking water from Province in

Hong-jian Gao & You-qian Jin & Jun-ling Wei

Received: 4 February 2012 /Accepted: 25 July 2012 /Published online: 19 August 2012 # Springer Science+Business Media B.V. 2012

Abstract This study analyzes the concentrations and safety in drinking water and controlling endemic health risks of fluoride in 249 drinking water samples fluorosis in different regions of Anhui Province. collected from different regions of Anhui Province in China. Results indicated that fluoride content in drinking Keywords Fluoride concentrations . Drinking water . waterrangedfrom0.12to1.94mgL−1 (mean00.57 mg Health risk assessment . Endemic diseases L−1) in the following order: plain region > Jianghuai hill region ≈ Dabieshan mountainous region > plain along the Yangtze River region > Introduction southern Anhui mountainous region. The fluoride contents were less than 0.50 mg L−1 in 66.66 % of the Fluorine is the lightest halogen and one of the most drinking water samples, 0.51–1.0 mg L−1 in 23.29 %, reactive of all chemical elements (Kaminsky et al. − and higher than 1.0 mg L 1 in 12.04 %. The fluoride 1990). It is also the most electronegative element, levels in some samples were lower than the which indicates its strong tendency to acquire a nega- recommended values for controlling dental caries tive charge and form F− ions in solution (Helm 1985). − (0.50–1.0 mg L 1). The total fluoride intake from Fluorine is found as fluoride in the environment, drinking water was between 0.14 and 2.33 mg per day which together represent about 0.06–0.09 % of the in different regions of the province, supposing an earth’s crust. Fluoride occurs naturally in rock, soil, individual consumes 1.2 L of water per day. Therefore, water, plants, and animals (Ozsvath 2009; Walna et al. measures should be taken to increase fluoride intake in 2007; Zhu et al. 2007). Fluoride is absorbed by body the Jianghuai hill region, Dabieshan mountainous tissues, such as teeth and bones, when ingested by region, plain along the Yangtze River, and southern humans and other animals (Harrison 2005). Different Anhui mountainous region to control dental caries. On forms of fluoride exposure are critical and have shown the other hand, the fluoride levels must be reduced in the to affect fluoride content in the body, thus increasing Huaibei plain region to decrease endemic fluorosis. The the risk of fluoride-prone diseases (Harrison 2005). results serve as crucial guidelines for managing fluoride Fluoride in drinking water has beneficial effects on teeth at low concentrations (<1.0 mg L−1), such as : : preventing and reducing the risk of tooth decay H.-j. Gao (*) Y.-q. Jin J.-l. Wei (Harrison 2005;Ozsvath2009). However, concentra- School of Resources and Environment, tions lower than 0.5 mg L−1 intensify the risk of dental Anhui Agricultural University, 230036, China caries (Ozsvath 2009). Fluoride can also be detrimental − e-mail: [email protected] at concentrations exceeding 1.5–2.0 mg L 1 (WHO 3688 Environ Monit Assess (2013) 185:3687–3695

1984). High concentrations of fluoride increase the supply for both excessive and insufficient fluoride risks of dental and skeletal fluorosis depending on content. the level and period of exposure (Hileman 1988; Kaminsky et al. 1990). Fluoride is found most frequently in ground water Materials and methods at higher concentrations depending on the nature of rocks and natural fluoride-carrying minerals at certain Study area depths (Guo et al. 2007). Natural fluoride concentra- tions in ground water range from trace quantities to Anhui Province (114°54′–119°37′ E, 29°41′–34°38′ N) over 25 mg L−1 (Harrison 2005). High levels of fluo- is an inland province in Southeast China with a popula- ride in drinking water have been detected in India tion of over 64.6 million. It stretches over the Yangtze (Dhiman and Keshari 2006), Turkey (Oruc 2008), River and the Huaihe River. The province is divided into Pakistan (Tahir Shah and Danishwar 2003), and China five topographical zones from north to south: (1) The (Guo et al. 2007). Huaibei plain region, an alluvial plain on both banks of China is one of the countries that suffered from the Huaihe River, is part of the North China plain and serious endemic fluoride diseases, such as dental caries makes up half the farmland of the province. (2) The and skeletal fluorosis (Wang and Huang 1995). More Jianghuai hill region is the watershed of the Huaihe than 26 million people suffer from dental fluorosis, and River and the Yangtze River valleys. (3) The Dabieshan over one million suffer from skeletal fluorosis (Lennon mountainous region in the west extends to the east to et al. 2004). In Anhui Province of China, over three join the Huoshan Mountains. (4) The plain along the million and 0.1 million people reportedly suffer from Yangtze River, which is part of the Middle-Lower dental and skeletal fluorosis, respectively; most of the Yangtze River Plain, includes the flatlands along the cases are found in , , , Huaibei, Yangtze River and the Lake basin. (5) The , and seven other cities (Deng 2006). The high southern Anhui mountainous region is located south of fluoride content in both shallow and deeper ground the Yangtze River side plain. water is the major cause of endemic fluorosis in the province (Deng 2006). Instruments and Reagents Several measures have been conducted to adjust fluoride in drinking water. Fluoridation of public water The Thermo Scientific Orion 4-Star plus pH/ISE meter supplies is one of the most popular approaches to (9609BNWP fluoride ion-selective electrode and increase fluoride in drinking water to reduce the preva- 096019 stirrer probe) was purchased from Thermo Fish- lence of dental caries (Fawell et al. 2006). Three specific er Scientific Inc., USA. For the fluoride stock solution treatments, namely, chemical coagulation, activated alu- (1,000 mg L−1), 0.2210 g of sodium fluoride (dried 2 h mina, and membranes, have been successful in remov- at 110 °C and stored in a desiccator) was dissolved in ing fluoride from drinking water (Fawell et al. 2006). distilled water, diluted to 100 mL in a volumetric flask, However, most of the rural inhabitants in China are and then stored in a clean polyethylene bottle. Prior to accustomed to consuming drinking water collected from use, the fluoride standard solution was diluted to varied private ground water wells without any safe treatments concentrations with distilled water. The total ionic (Dai et al. 2004). Therefore, the low or high levels of strength adjustment buffer (TISAB) was prepared via fluoride in drinking water still pose threats for human the following steps: Approximately 57.0 mL of glacial health (Guo et al. 2007). acetic acid, 58.0 g of sodium chloride, and 68.0 g of This study aims to investigate the concentrations sodium citrate were added to 700 mL of distilled and distributions of fluoride in drinking water collected water in a 1.0-L beaker. Solution pH was adjusted from the rural and city inhabitants from different regions between 5.0 and 5.5 with 5 M NaOH after dissolving of Anhui Province. The health implications posed by and cooling to room temperature. The solution was fluoride levels in drinking water were also analyzed transferred to a 1,000-mL volumetric flask, diluted to according to the national and international quality the mark with distilled water, and finally stored in a standards. The results of the study would be helpful clean polyethylene bottle. All reagents used in this in working out strategies for safe drinking water study were of analytical grade. Environ Monit Assess (2013) 185:3687–3695 3689

Drinking water sampling (9609BNWP fluoride ion-selective electrode) follow- ing the method developed by Gao et al. (2010). The From 10 to 25 February 2009, 249 drinking water temperature of the drinking water samples was bal- samples were collected from the local inhabitants from anced to room temperature before the analysis. Ap- different regions of the province (Fig. 1). The sam- proximately 20.0 mL of drinking water and 20.0 mL pling sites were widely distributed in different regions of TISAB were added to a 50-mL polyethylene to assure the representative of water sample collection. beaker and completely mixed using a clean glass Well water from five rural inhabitants and public water bar. The fluoride ionic electrode tip was then im- from five city inhabitants in each sampling site were mersed into the mixed solution, and the meter read- randomly collected and then completely mixed to ing was recorded as soon as the reading was stable. form one water sample. Prior to sampling, 1.0-L poly- Triplicate experiments were performed for each ethylene bottles were washed with drinking water drinking water sample. three times. Water samples were collected from public Fluoride at concentrations of 0.25, 0.50, 1.0, water supply systems in cities and from wells in rural 2.0, 4.0, and 6.0 mg L−1 were spiked in double- regions into 1.0-L clean polyethylene bottles during distilled water to examine the assurance of the the sampling. Eighteen bottled drinking water samples analytical method. The line equation fitted the were purchased from supermarkets in Hefei City, the fluoride concentration reasonably well, and the capital of Anhui Province. The drinking water samples square of the correlation coefficient was 0.998. were filtered through a Millipore cellulose membrane The average recovery of fluoride spiked in double- (0.45 μm) and then stored in polyethylene bottles at a distilled water ranged from 90.5 to 106 %, and low temperature (−4 °C) before analysis. the relative standard deviation was between 5.60 and 9.4 %. The variation of fluoride concentra- Analytical method tions in the replicated samples was less than 12.0 %. The limit of detection, defined as the Fluoride concentrations in drinking water were deter- standard deviation from the mean blank (n05), was − mined using a fluoride ion-measuring instrument 0.10 mg L 1.

Fig. 1 General map of Anhui Province showing the study area 3690 Environ Monit Assess (2013) 185:3687–3695

Data analysis (0.34 mg L−1) > southern Anhui mountainous region (0.24 mg L−1). The highest fluoride concentrations of Fluoride concentrations in drinking water were expressed 1.94, 1.37, and 1.19 mg L−1 in drinking water were as milligram per liter of water. Excel 2003 for Windows found in Bozhou, Fuyang, and Suzhou Cities of the was used for data analysis. Huaibei plain region, with mean values of 1.05, 0.71, and 0.76 mg L−1,respectively. This result is consistent with the early studies in Results and analysis Jieshou and Taihe Cities of the Huaibei plain region, with mean fluoride concentrations of 1.02 and Fluoride in drinking water from different regions 1.03 mg L−1, respectively (Wu and Ye 2008). The of Anhui Province meanfluorideconcentrationof0.49mgL−1 was detected in Hefei City of the Jianghuai hill region Fluoride concentrations in 249 drinking water samples (Yang et al. 2008). The relatively low fluoride con- collected from different regions of the province were centration of 0.15 mg L−1 was found in Huangshan between 0.12 and 1.94 mg L−1, with a mean City of the southern Anhui mountainous region (Hu concentration of 0.57 mg L−1 (Table 1). Fluoride et al. 2008). levels in drinking water were in the following order: The fluoride levels in bottled drinking water in Hefei Huaibei plain region (0.85 mg L−1) > Dabieshan moun- City were between 0.12 and 0.53 mg L−1, with a mean tainous region (0.42 mg L−1) ≈ Jianghuai hill region concentration of 0.39 mg L−1. This level was higher (0.41 mg L−1) > plain along the Yangtze River region than the mean fluoride concentrations in southern Anhui

Table 1 Fluoride concentrations −1 in drinking water collected from Sampling regions Sampling sites Samples Fluoride concentration (mg L ) different regions of Anhui Province in China Maximum Minimum Mean SD

Huaibei plain region 96 1.94 0.25 0.85 0.42 Huaibei 6 0.91 0.45 0.68 0.25 Suzhou 21 1.19 0.28 0.76 0.35 Bozhou 36 1.94 0.44 1.05 0.42 Fuyang 12 1.37 0.33 0.71 0.41 21 0.94 0.25 0.58 0.22 Jianghuai hill region 33 0.86 0.19 0.41 0.18 Hefei 18 0.86 0.43 0.53 0.15 15 0.38 0.19 0.30 0.07 Dabieshan Lu’an 21 0.70 0.29 0.42 0.15 mountainous region Plain along the 63 0.60 0.16 0.34 0.12 Yangtze River 27 0.34 0.18 0.28 0.09 6 0.33 0.16 0.25 0.09 3 0.56 0.56 0.56 0.00 3 0.34 0.33 0.33 0.01 Maanshan 9 0.60 0.34 0.51 0.24 Southern Anhui 18 0.34 0.12 0.24 0.08 mountainous region Huangshan 9 0.33 0.12 0.22 0.09 9 0.34 0.17 0.24 0.07 Bottled drinking Supermarket 18 0.53 0.12 0.39 0.13 SD standard deviation water (Hefei) a All drinking water samples ∑a 249 1.94 0.12 0.57 0.14 analyzed Environ Monit Assess (2013) 185:3687–3695 3691 mountainous region (0.24 mg L−1) and plain along the Yuncheng City of Shanxi Province (Li et al. 2006), Yangtze River region (0.34 mg L−1) but lower than that Yongkang City of Zhejiang Province (Xu 2001), Daxing in the Huaibei plain (0.85 mg L−1), Jianghuai hill region District of (Zhao et al. 2008), and Shaoguang (0.41 mg L−1), and Dabieshan mountainous regions City of Guangdong Province (Wu et al. 2006) were 4.50, (0.42 mg L−1). 4.20, 4.20, 3.81, and 3.80 mg L−1, respectively. However, The frequency distributions of fluoride in drinking the low fluoride contents of 0.29, 0.27, and 0.10 mg L−1 water were also analyzed in this study (Fig. 2). Out of were reported in Yulin City of Guangxi Province (Chen the 249 drinking water samples studied, the fluoride et al. 2006), of Jiangxi Province (Gong 2008), concentrations were less than 0.50 mg L−1 in 66.66 % and Tibet (Cao et al. 2000), respectively. of the drinking water samples, 0.51–1.0 mg L−1 in 23.29 %, and higher than 1.0 mg L−1 in 12.04 %. The Guideline values for fluoride in drinking water mean fluoride concentrations in drinking water from the Jianghuai hill, Dabieshan mountainous, plain along the Fluoride in drinking water has beneficial effects on − Yangtze River, and southern Anhui mountainous teeth at low concentrations (0.50–1.0mgL1), but regions were all lower than 0.50 mg L−1.However,the excessive exposure to fluoride in drinking water or fluoride levels in 30.24 % of the samples from Huaibei in combination with exposure to fluoride from other plain region were higher than 1.0 mg L−1. The fluoride sources can give rise to a number of adverse effects levels in all the samples of bottled drinking water were (Dey et al. 2004; Kaminsky et al. 1990). In the 1980s, lower than 1.0 mg L−1, and 88.88 % of the samples were WHO noted that teeth mottling (i.e., dental fluorosis) lower than 0.50 mg L−1. is sometimes associated with the fluoride levels in drinking water above 1.5 mg L−1, and crippling Fluoride in drinking water in other skeletal fluorosis can ensue when the fluoride levels exceed 10 mg L−1 (WHO 1984). A guideline value Large differences of fluoride in drinking water are of 1.5 mg L−1 was, therefore, recommended by found in China (Table 2). The fluoride in selected WHO as a level at which dental fluorosis should drinking water samples from 12 provinces ranged be minimal (WHO 1984). The US Environmental from 0.02 to 4.50 mg L−1. The mean levels of fluoride Protection Agency set a maximum contaminant level in drinking water from Shaoguang City of Guangdong of 4.0 mg L−1 for protection against skeletal fluoro- Province (Wu et al. 2006), Yuncheng City of Shanxi sis and a secondary guidance value of 2 mg L−1 for Province(Lietal.2006), and Daxing District of protection against moderate to severe dental fluorosis Beijing (Zhao et al. 2008) were 4.18, 3.10, and 2.51 (Lennon et al. 2004). The fluoride level of the Chinese times higher than that from Anhui Province, respective- sanitary standard for drinking water is 1.0 mg L−1 ly. However, the mean concentrations of fluoride in (GB5749-2006 2006). drinking water from Tibet (Cao et al. 2000), Nanchang Compared with local and international drinking City of Jiangxi province (Gong 2008), and water quality guideline values for fluoride, 12.04 % City of Guangdong Province (Shi et al. 2008) were of the drinking water samples in Anhui Province lower than the levels from Anhui Province. The high were higher than the Chinese sanitary standard for fluoride concentrations in drinking water samples col- drinking water (1.0 mg L−1), 1.20 % were higher lected from Xi’an City of Shaanxi Province (Yao 2005), than the WHO drinking water quality guideline

Fig. 2 Frequency distribu- 100% 1 Huaibei plain region tions of fluoride in drinking 80% 2 Jianghuai hill region water in Anhui Province (%) 60% 3 Dabieshan mountainous region 4 Plain along the Yangtze River 40% 5 Southern mountainous Region. 20% Frequency distribution 6 Bottled drinking water samples 0% 12345677 Mean levels in Anhui province

0-0.50mg L-1 0.51-1.00mg L-1 1.01-1.50mg L-1 1.51-2.00mg L-1 3692 Environ Monit Assess (2013) 185:3687–3695

Table 2 Fluoride concentrations in drinking water from other provinces of China

Sampling province Sampling sites Samples Fluoride concentration (mg L−1) References

Maximum Minimum Mean SD

Anhui Meana 249 1.94 0.12 0.57 0.14 686 1.20 0.18 Shao et al. (2000) Heilongjiang Lindian 1,150 0.88 0.98 0.02 Zhang and Zhang (2005) Guangdong Shaoguang 10 3.80 0.52 2.38 Wu et al. (2006) Guangzhou 31 0.52 0.06 Shi et al. (2008) Shaanxi Xi’an 20 4.50 0.27 Yao (2005) Shanxi Yuncheng 108 4.20 1.77 0.88 Li et al. (2006) Zhejiang Yongkang 367 4.20 0.10 Xu (2001) Guangxi Yulin 5 0.29 0.11 Chen et al. (2006) Beijing Daxing 467 3.81 1.01 1.43 Zhao et al. (2008) Shandong Zaozhuang 98 1.66 0.33 0.49 0.54 Yu (2004) Jiangxi Nanchang 15 0.27 0.16 0.22 Gong (2008) Tibet Mean 71 0.10 0.02 Cao et al. (2000)

SD standard deviation a Mean concentration of all the drinking water samples from Table 1

value (1.50 mg L−1), and all of the samples were rich areas, such as bone and teeth, because of its high lower than the standard value of the USA (2.0 mg affinity for calcium (MMWR 2001). There are three L−1) (Lennon et al. 2004). ways by which fluoride influences the process of tooth decay, namely, improvement of the chemical structure of the enamel during development, making it more Discussions resistant to acid attack; encouragement of mineraliza- tion with an improved quality of enamel crystals; and Fluoride is one of the very few chemicals that cause reduction of the ability of plaque bacteria to produce significant influences on human health through drink- acid (Harrison 2005). The risks of dental caries in- ing water (Hamilton 1992). The optimal concentration crease when fluoride concentrations in drinking water − of fluoride in drinking water varies according to cli- are lower than 0.5 mg L 1 (Dissanayake 1991). About matic conditions; the range of 0.5–1.0 mg L−1 is 50–60 % of the inhabitants in China suffered from generally recommended by WHO (WHO 1994). Fluo- dental caries when fluoride levels in drinking water − ride in public water supplies required for the preven- were lower than 0.50 mg L 1. On the contrary, only tion of dental caries ranges from 0.7 to 1.2 mg L−1 in 30–40 % of dental caries were found when fluoride − the USA (Hamilton 1992). In Canada, the optimal concentrations increased between 0.50 and 1.0 mg L 1 fluoride concentration in drinking water is between (Ren 2002). About 82.3 % of children at ages 6– 0.8and1.0mgL−1 (Harrison 2005). In the UK, 14 years old suffered from dental caries due to low − concentration of 0.3–0.7 mg L−1 fluoride is considered fluoride levels (below 0.50 mg L 1) in drinking water to afford below optimal protection against tooth decay (Meng 2001). Fluoride concentrations in drinking water (Harrison 2005). In China, the optimal fluoride con- collected from Jianghuai hill, Dabieshan mountainous, tent in drinking water is between 0.50 and 1.0 mg L−1 plain along the Yangtze River, and southern Anhui (GB5749-2006 2006). mountainous regions in this study were all lower than − Once absorbed into the blood, approximately 99 % 0.50 mg L 1; thus, potential risk of dental caries may be of the body burden of fluoride is retained in calcium- high in these regions. Environ Monit Assess (2013) 185:3687–3695 3693

Fluoride at excessive levels in drinking water can Conclusions give rise to dental and skeletal fluorosis (WHO 1994). The severity depends upon the amount ingested and The fluoride concentrations in drinking water in dif- the duration of intake (Ozsvath 2009). Fluoride con- ferent regions of Anhui Province of China were be- centrations of 1.5–2.0 mg L−1 in drinking water may tween 0.12 and 1.94 mg L−1 (mean00.57 mg L−1). result in higher chances of dental fluorosis, whereas The fluoride contents were less than 0.50 mg L−1 in concentrations exceeding 4.0 mg L−1 may have high 66.66 % of the drinking water samples, 0.51–1.0 mg L−1 chances for skeletal fluorosis (Dissanayake 1991). in 23.29 %, and higher than 1.0 mg L−1 in 12.04 %. The Fluoride concentrations exceeding 10 mg L−1 may fluoride concentrations in drinking water sampled from give rise to crippling skeletal fluorosis and possible Dabieshan mountainous region, plain along the Yangtze cancer (Dissanayake 1991). Fluoride concentrations in River, and southern Anhui mountainous region were drinking water from different regions of Anhui Province lower than the recommended value for controlling were all lower than 2.0 mg L−1; only three regions dental caries (0.50 mg L−1). Therefore, measures showed concentrations higher than 1.50 mg L−1.How- should be taken to increase the fluoride intake in ever, fluoride in some drinking water form Xi’an of these regions. On the other hand, the fluoride levels Shaanxi Province (Yao 2005), Yuncheng of Shanxi in some samples collected from the Huaibei plain Province (Li et al. 2006), and Yongkang of Zhejiang region were higher than 1.0 mg L−1, which may Province (Xu 2001) in China were 4.50, 4.20, and increase the risk of dental fluorosis. 4.20 mg L−1, respectively, which may pose a high risk of skeletal fluorosis to the locals. Acknowledgments We thank the National Natural Science The most important factor for endemic fluorosis is Foundation of China (41071158) and the Key Project of the total amount of fluoride ingested from all sources Chinese Ministry of Education (210097) for financially supporting (drinking water, tea, foodstuffs, air, and so on) this work. We also gratefully acknowledge the anonymous reviewers who provided valuable comments and suggestions for (Kaminsky et al. 1990). A recommended fluoride in- improving this manuscript. take of 0.05 mg kg−1 per day for a 60-kg individual is considered acceptable. A daily intake of fluoride from 1 to 3 mg of body weight prevents tooth decay and References dental caries. However, the optimal dose of fluoride ingested daily by children under the age of six ranges from 0.5–1.0 mg per day of body weight (IPCS 1984). Cao, J., Zhao, Y., Liu, J. W., Xirao, R. D., & Danzeng, S. B. The optimal fluoride intake of 2.5–4.0 mg per person (2000). Environmental fluoride contents in Tibet. Environ- mental Research Section A, 83, 333–337. per day is recommended by WHO (1994). The total Chen, Y., Xie, Z. F., Yan, Q., Cai, G. Q., & Chen, J. Z. (2006). fluoride intakes of 2.5 mg per day for children and Preliminary investigation the contents of fluoride in the 2.5–4.0 mg per day for adults are recommended in the environmental water body and drinking water in Yulin of Guangxi Province, China. Journal of Yulin Teachers College, USA (Doull et al. 2006). In China, the upper limits of – – 27(3), 76 80 (in Chinese). fluoride are 4.0 mg per day for adults and 2.0 2.4 mg Dai, S., Ren, D., & Ma, S. (2004). The cause of endemic per day for children (Liang et al. 1996). fluorosis in western Guizhou Province, Southwest China. In this paper, the total fluoride intake from drinking Fuel, 83, 2095–2098. water was recorded between 0.14 and 2.33 mg per day Deng, Y. C. (2006). Reasons and distributions of high fluoride in underground water in Anhui Province, China. Jiang-huai in different regions of Anhui Province, supposing that Water Resource Science, 2,22–24 (in Chinese). one consumes 1.2 L of water per day. None of the Dey, S., Goswami, S., & Ghosh, U. C. (2004). Hydrous ferric drinking water exceeded the upper limits of national oxide (HFO)-a scavenger for fluoride from contaminated – (4.0 mg) and international (4.0 mg) recommended water. Water, Air, and Soil Pollution, 158,311 323. Dhiman, S. D., & Keshari, A. K. (2006). Hydrogeochemical values. However, most of the samples were lower than evaluation of high-fluoride ground water: a case study from the minimum recommended values (2.0 mg). Therefore, Mehsana District, Gujarat, India. Hydrological Sciences measures should be taken to increase fluoride intake Journal, 51(6), 1149–1162. through foodstuff, tea, beverage, and fluoridated tooth- Dissanayake, C. B. (1991). The fluoride problem in the ground waterofSriLanka—environmental management and paste consumption to prevent dental decay and caries in health. International Journal of Environmental Studies, some regions of Anhui Province. 38, 137–156. 3694 Environ Monit Assess (2013) 185:3687–3695

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