Research on Relationship Between Fluorine in Tap Water and That in Urine of Chinese Residents

Vol.23 No. 4CHINESE JOURNAL OF GEOCHEMISTRY2004Research on Relationship Between Fluorinein Tap Water and That in Urineof Chinese R esidentsWANG Binbin (王滨滨) , ZHENG Baoshan (郑宝山)，ZHAI Cheng (翟城),LIU Xiaojing (刘小静), and AN Ning (安宁)( State Key Lab of Enuiormental Geochemistry , Institute of Geochenistry , ChineseAcademy of Sciences, Guiyang 550002，China)Abstract: In this study, the relationship between fluorine in drinking water and that in urine ofurban residents in China is assessed. Fluorine concentrations in tap water and those in urineshow a good correlation with a linear regression cofficient of 0.9798，indicating that the fluorineconcentrations in big eities under investigation are extremely low, and the main source of fluo-rine is tap water. The weather effect on the intake amount of fluorine is also discussed. Whenair temperature is above 15C，people would intake more fluorine through drinking water withthe rise of air temperature. When temperature is below 15C, no remarkable relationship is ob-served between air temperature and the intake amount of fluorine. This phenomenon indicatesthat the main source of fluorine in China is tap water instead of foodstuff.Key words: fuorine; tap water; urine; dental health1 IntroductionFluorine is one of the crucial chemical elements to human health. Overloading of fluorine maycause dental and/ or skeletal fluorosis. While in the fluorine deficiency areas，fluoridation drinkingwater supply or other methods of fluoridation may greatly reduce the ratio of dental caries of local res-idents. During the early stage of biological evolution, the fluorine concentrations in the ancient 0-ceans were homogeneous. Ancient organisms did not develop any fluorine-resisting mechanism ，which made subsequent life forms living in terrene environments face more challenges due to differ-ent fluorine contents in different parts of the continent. And that is probably the fundamental reasonfor the prevalence of fluorosis and dental caries among human beings.Research on the relationship between fluorine concentrations in drinking water and ratios of hu-man dental caries, as well as on the efficacy evaluation of drinking water fluoridation has lasted over6 decades. Dean ( 1942) found that with increasing fluorine concentrations in drinking water from0.1 to 1.0 mg/L, the average number of decayed，missing and false teeth ( DMFT) decreased from7.0 to 3.5, but such decrease became less obvious when the fluorine concentrations of drinking wa-ter exceed 1.0 mg/L. His findings were confirmed by a great deal of subsequent studies. In 1945 ,the United States Public Health Service ( USPHS) carried out experiments in 3 cities to confirm theefficacy of drink ing water fluoridation in preventing dental caries, and the experimental results ap-proved that the ratio of dental caries of local children in中国煤化工! to half the origi-THCNMHGISSN 1000-9426* This project was financially supported by the National Committee for Oral Health ( NCOH) and the State Key Laboratory of Envi-ronmental Geochemistry, Institute of Geochemistry ，Chinese Academy of Sciences.374CHINESE JOURNAL OF GEOCHEMISTRYVol.23nal value with increasing concentrations of fluorine in drinking water to 1.0 mg/L. Similar resultswere obtained in Europe, Canada and some other cities of the U.S. Before 1992, the social and e-conomic benefits of drinking water fluoridation to adult residents lacked convincing confirmation. In1992, Thomas and Kassab reported that the DMFT of mothers from drinking-water -fluoridated re-gions was 30% lower than that of control regions ( Thomas and Kassab, 1992). In fact, drinkingwater fluoridation has been widely accepted as a public sanitation measure in some western coun-tries. By the year of 1993, 145 million residents in 42 out of the 50 biggest cities of the U. S. hademployed fluoridated water ( Hinman et al. ，1996)，and the project of drinking water fluoridationhad been implemented in Australia, Brazil, Canada ，Colombia, Hong Kong, Ireland ，Malaysia,New Zealand, Singapore ，Spain, and the U. K. In 1984, the WHO defined that drinking water fluo-ridation was a safe and economical measure of preventing dental caries and should be energetically adopted by fluorine- deficient regions. The appropriate concentrations of fluorine in drinking watershould vary between 0.5 mg/L and 1.0 mg/L according to different climates, daily drinking a-mount, etc. Furthermore, a great deal of research has proved that“there is no evidence for the con-nection between concentration and fluoridated drinking water" ( IARC，1987; Bucher et al. ，1991);“the negative affect on human procreation is least at any level of fluorine exposure. ”( Col-lins et al. , 1995; Sprando, 1996).In China, research on drinking water fluoridation faces great challenges. In the 1960's, re-search on the effect of experiment of tap water fluoridation was conducted in Guangzhou but did notyield any reliable results. Because of administration chaos during the Culture Revolution, the quan-titative control of fluorine concentrations in tap water was unstable, which caused slight fluorosisprevalence. Many Chinese scientists argued against drinking water fluoridation with the attitudeswhich lie in the following two aspects: 1) the amount of daily calcium intake of the Chinese peopleis far less than that for western counterparts, so drinking water fluoridation may cause dental fluoro-sis prevalence; and 2) due to significant difference in main diet between China and western coun-tries, the Chinese people can intake enough fluorine from diet and atmosphere ，which makes it un-necessary the fluoridation of drinking water. Therefore, the local government of Guangzhou stoppedthe experiment in 1983 and all relevant research paused from that time. Anyhow, the efficacy ofdrinking water fluoridation in China needs to be assessed again. There should be an appropriate con-centration standard of fluorine for tap water, according to which it is able not only to present dentalcaries, but also to avoid the prevalence of fluorosis. In this study , the relationship between fluorinecontent in drinking water and that in urine of urban residents, and the fluorine concentrations in tapwater in major cities, as well as the weather effect on the amount of daily fluorine intake were dis-cussed.2 Method2. 1 Population under investigationThe regions studied include 22 big cities in 9 provinces , 2 municipalities and 4 fluorine exposurevillages in China (Fig. 1). About 100 to 150 16- and 18-aged local residents of each city were inves-tigated. In 4 fluorine exposure villages, fewer target中国煤化工ailable in this study.Most of the targets were students at local high schoolseen living in their re-spective communities for more than 15 years. ResidenYHN M H Gr the Bahou region inHebei Province were good indicators for different levels of fluorine exposure in drinking water.No.4CHINESE JOURNAL OF GEOCHEMISTRY375Chaoyang,SheryangYellowBeijlingJlayuguan.。DallanBazhouQingdaoRiverLinyi''TanshuiDujiangyano*.Chengdu Xiangfan. WuhanD Shanghaiis SengtnYangzeXianning>ai' KunmingShaoguanoYimenGuangzhouoZuhaiFig.1. Map showing the locations of the cities and areas under investigation.2.2 Tap water and urine samplingIn each city and village investigated , the concentrations of fluorine in tap water and in the urineof local residents were determined. Tap water samples were collected from water sources, tap waterfactories，and residents’ houses. It is approved that the fluorine concentrations of urine excretedduring different periods of a day are slightly different. Research has confirmed that random tests ofurinary fluorine concentrations could substitute for 24 h sample tests when the number of targets islarge enough. In this study, urine samples from each community were ollected at8 - 10 o’clock inthe morning, which kept urine samples excreted almost at the same period of a day and made the da-ta of different research communities comparable. For sampling， typical polypropylene containersused for medical purpose were distributed among target groups. The tap water samples and urinesamples were analyzed on the same day for fluorine concentrations.2.3 Fluorine determination methodA monocrystalline fluorine electrode-based potentiometer was used to determine fluoride concen-trations in tap water, as well as in urine due to its high se中国煤化工response to inter-fering ions) , wide linear range ( over 4 decades) and low:0HCNMH(/L). The advan-tages of this approach include: short analysis time ( less Tnan J min), no neeu Ui sample pretreat-ment in most cases, easy reduction of possible matrix effects ( TISAB addition), simplicity of the376CHINESE JOURNAL OF GEOCHEMISTRYVol.23measuring system and relatively low instrument cost. The concentrations of fluoride ions were deter-mined on 3175 urine samples and 74 tap water samples were analyzed for their fluorine ion concen-trations. All the samples were analyzed with the direct reading method.3 ResultsTable 1 presents the number of persons under investigation，the average fluorine concentrationsin urine, and those in tap water for investigated communities. Due to their local residential durationnot meeting our demands ( local residential duration not less than 15 years) ，the numbers of personsunder investigation in Zhuhai, Linyi and Shenyang were less than 100. In 4 fluorine exposure villa-ges, it is diffcult to find qualified targets because many younger local residents were studying, work-ing and living in neighboring cities. Moreover, because some local residents were aware of the harm-fulness of exposure of high fluorine concentration in drinking water and used bottled distilled water astheir drinking water，the numbers of qualified targets in fluorine exposure villages were much lessthan those in cities.Fluorine concentrations in tap water in most cities ( expect 4 fluorine exposure villages in theBazhou region) are very low. Figure 2 shows the general concentrations of fluorine in tap water inthe cities investigated. Fluorine concentrations in tap water from 75% of the total investigated citiesare below 0.3 mg/L，and in more than 90% of the total investigated cities, the fluorine concentra-tions of tap water are below 0.5 mg/L. Only in 2 cities, are the fluorine concentrations of tap waterhigher than 0.5 mg/L. The highest values were reported from Shanghai (0. 667 mg/L). The aver-age fluorine concentrations in urine samples from different cities are within the range of 0.196 mg/L( Lanzhou) -1. 180 mg/L ( Neijiang). In fluorine exposure villages of the Bazhou region, HebeiProvince，fluorine concentrations both in tap water and in urine are within the range of 1.07 -4.29mg/L, and 1. 79 -4.36 mg/L, much higher than those of investigated cities. Figure 3 summarizesthe relationship between fluorine concentrations in tap water and those in urine of investigated com-munities, and shows a comparatively strict positive correlation ( linear regression coefficient R is0.96). The relationship between fluorine concentrations in drinking water and those in urine indi-cates that drinking water is the main source of fluorine intake of Chinese residents，though the fluo-rine contents of tap water from most investigated cities are very low. There is not remarkable differ-ence in the source of fluorine intake between Chinese and western people.色5r c 1.3293x+ 0.20116050着1▲200<0.30.3~0. 50.5~0.7(mg/L)25F concetration in tap water (mg/L)Fig. 2. Comparison of fluorine concentrations in tapFig.3. The relationship between fluorine concentra-water from the cities investigated ( Wang Binbin et al. ,2004).中国煤化工-urine, .In Fig. 3, there is a triangle located atx=4.THCN MH Ge trend line, indica-ting the correlation between fluorine concentrations in Tap water ana inose in unne at that point is notthe same as in other villages and cities. That point represents Shengfang Village- -a fluorine expo-No.4.CHINESE JOURNAL OF GEOCHEMISTRY377sure region. In Shengfang Village ，fluorine concentrations in tap water are the highest of all investi-gated communities. It is diffcult to explain the difference in correlation between Shengfang Villageand other communities. One possible explanation is that the local residents of Shengfang Village arericher and more aware of the harmfulness of local F-high tap water as compared with the other 3 fluo-rine exposure villages ，and many residents refuse to use tap water for drinking. This point is not in-volved in liner regression calculation.Table 1. Average fluorine concentrations in urine of target groups and in tap water in the cities andvillages under investigation ( Wang Binbin et al.，2004 )Cities and areas investigatedNumber Average fluorine content StandardMax.Min. Average fluorine contentof targetsin urine (mg/L)deviationin tap water ( mg/L)Lanzhou1090.1960. 1471.470 0.0530.064Jiayuguan1020. 2000. 0790.3760. 0860. 107Tianshui1320. 2470. 137.0.923 0.0670.101Guangzhou140. 5880.2431.2700. 1420.034Zhuhai610.3730. 2511.386 0.093Shaoguan090.3390. 1651. 0420. 0740.007Wuhan150.3290.150.0. 868 0.0480.222Xianning680. 2800. 1060.709 0. 1040. 089Dujiangyan1150.7150.2991.530 0. 150.0. 140Neijiang1051.1800.5362.600 0. 3600.570Chengdu050.. 5780.3101.8900. 1200. 190linan1140. 7000. 3441.920 0. 1200. 340Qingdao030.7310. 2941.650 0. 3100.448Linyi73). 4690. 2161.320 0. 150Hangzhou108). 5520. 3101.530 0.0830. 178Huangpu District, Shanghai131. 0800.5132.4400.160.0. 644Hongkou District ，Shanghai470.9430. 2581.580 0.4940. 699Xuhui District, Shanghai160. 8930. 2601.390 0.2390. 657.Xiangfan1460.3610.160.1.130 0.1110.107Kunming1470.2860.131.1.080 0.0660. 105 .Dali410.3170. 1551.110 0.0970. 104Dongcheng District, Bejjing1590.4950.1791. 0800. 0950.248Chongwen District, Bejjing390.2910.1200.731 0.0510. 270Haidian District, Bejing)20.135.851 0.1130. 156Y imen55). 1310. 0350.2880. 0650. 020Shenyang30.5620.2571.400 0.1260. 050Dalian1000. 7630.315.1. 630 0.2190. 300Chaoyang020.9800. 4143.010 0.292 .0. 400Nanhao Village04.3601.6108.5102. 3452.730Hongxing Village3.2201. 4006.670 0.9424. 290Nanmeng Village1. 7800. 7264.121 0. 6861. 070Yuanli Village172. 6100. 9754.092 0.0302. 0604 DiscussionIt is diffcult to determine the daily fluorine intake amount of Chinese residents from diet andair, because it is difficult to determine the fluorine conte中国煤化工of vegetables anddiet from different soils in different regions of China. ButYHCNMHG.: the regression e-quation of the correlation curve in Fig. 3. The equationY=1.3293x +0.2011378CHINESE JOURNAL OF GEOCHEMISTRYVol.23where Y stands for the fluorine concentrations in urine, and x indicates the fluorine concentrations intap water.From the above equation, it can be deduced that when no fluorine exists in tap water (x= 0),fluorine concentration in urine is 0.2011 mg/L, which probably represents the fluorine intake fromdiet and air. Supposing the average amount of excreted urine is 1L per person per day, the averagefluorine excretion from main diet and air is approximately 0.2 mg per person per day. Because littefluorine is excreted through sweat and dejecta and partly stored in bones and teeth, the exact amountof fluorine intake from diet and air should be slightly higher than 0.2 mg.Weather can probably affect the daily amount of water intake. People will consume more waterwhen air temperature is higher. Therefore , weather can also affect the fluorine intake of Chinese res-idents. In this study ，the average air temperature and relative humidity of the research month in theperiod of 10 years (1991 - 2000) in 19 cities were provided by the China Meteorological Adminis-tration ( Table.2). Figure 4 shows the relationship between the average air temperature and the flu-orine concentrations in urine. In the cities where the average air temperature of the research month isbelow 15C, no correlation between fluorine content in urine and average air temperature in the cit-ies investigated has been found. In the cities where the average air temperature of the researchmonth is higher than 15C, a general positive correlation between urinary fluorine and average airtemperature is established. This indicates that when the average monthly air temperature is higherthan 15C, the daily amount of fluorine intake can be affected, and this result can also be consid-ered as a proof of the main course of fluorine intake. Relative humidity also has some correlationwith fluorine content in urine, but does not seem so distinct as air temperature ( Fig. 5).Table 2. Average air temperature and relative humidity of the research month in the period of ten years(1991 - 2000) ( Data from the China Meteorological Administration)Avernage air temperature of the re Average relative humidity of theResearch communityResearch datesearch month in the period of 10research month in the period of 10years (C)years (% )LanzhouApr. 18, 200212.9JiayuguanApr. 22, 200210.235Tianshui，Apr. 25, 2002 .13.457GuangzhouMar. 08, 200218.032ZhuhaiMar. 12, 200219.279Shaoguan14.8Wuhan .Mar.25, 200210.477DujiangyanSep. 12, 200020. 8Neijiang23.230Chengdu21.83inanNov.19, 20008.5iov. 14, 20009.256LinyiNov. 18, 20008.1)4HangzhouOct.21, 200018.776Huangpu District, ShanghaiNov. 07, 200013.574Hongkou District, ShanghaiNov. 08, 200013. 5Xuhui District, ShanghaiNov. 09, 2000KunmingMar. 18, 200214.4DaliMar. 19, 200213.22Dongcheng District, BeijingApr. 10, 2002中国煤化工5Chongwen District, Beijinglpr. 18, 200215Haidian District, BejjingApr. 16, 2002 .MHCNMHG.45YimenMar.21, 200258No.4.CHINESE JOURNAL OF GEOCHEMISTRY3791.41.2+ - Average i ternture ot h rerart mnth r90↑↓2012甘Relative bumidity 阁)1.018j08，15+ 10040.01234567891011121314151617 18192021 22 23Communily groupCommunty groupFig. 4. The relationship between fluorine concentrationFig. 5. The relationship between fluorine concentrationin urine and air temperature.in urine and average humidity.It is obvious that the relationship between air temperature or relative humidity and urinary fluor-ide is not isolated. No enough data have been acquired to assess the effect of air temperature at thesame relative humidity. It is also diffcult to accurately estimate the percentage of fluorine from waterintake. What we can know from this research is that when air temperature is higher than 159C, peo-ple will intake more fluorine through drinking water, and when temperature is below 15C, thereseems no relationship between air temperature and the amount of fluorine intake. This can be consid-ered as a reference for further study.ReferencesBucher, J R.，R. Milton Hejitmancik, D. John ToftI, R. L Persing, S.L. Fustis, and J. K. 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