Investigation of iodine concentration in salt, water and soil along the coast of Zhejiang, China

1200 .Lu et al.1J Zhejiang Univ SCIENCE B 2005 6(12):1200-1205Journal of Zhejiang University SCIENCE BISSN 1673-1581htp://ww.zju.edu.cn/jzusJZuSE-mail: jzus@zju.edu.cnInvestigation of iodine concentration in salt, waterand soil along the coast of Zhejiang, ChinaLU Ying-li (陆颖理)f", WANG Ning-jian (王宁荐), ZHU Lan (朱岚)', WANG Guo-xing (王国兴),WU Hui (吴晖), KUANG Lin (匡琳), ZHU Wen-ming (朱文明)2( Department of Endocrinology, Sir Run Run Shaw Hospital, School of Medicine, Zhejiang University, Hangzhou 310016, China)(Disease Control Center, Hangzhou 310006, China)'E-mail: luyingli2008@ 126.comReceived Oct. 17, 2005; revision accepted Nov.5, 2005Abstract: Objective: We aim to describe the environment iodine concentration in salt, water and soil along Zhejiang Provincecoast in the China foreland. It will be helpful for us to judge whether this area is insufficient in iodine and universal iodized salt isnecessary or not. Methods: We collected idized salt samples, drinking water samples (tap water in the towns, and well water orspring water in the vllages), water samples from diferent sources (ditches, lakes, river) and soil samples through random sam-pling in June, 2005. Salt, water and soil iodine was detected by arsenic-cerium redox method. Statistical analysis was expressed aswater samples were colleted. The water iodine value was 0.6~-84.8 ug/L (mean of 11.66 ugL). The watershed along the QiantangRiver has significantly higher iodine content than the water in Lin 'an in mountain area (P<0.01). The iodine content and meaniodine content of tap water, well or spring water and natural water sources were 4.30+2.43 ug/L (n=34), 23.59+27.74 ug/L (n=19)and 12.72+10.72 μugL (n=22) respectively. This indicated that among environmental water sources, the ditch iodine content wasthe highest with river water iodine being the lowest (P<0.01). (3) Soil iodine value was 0.1 1~2.93 mg/kg (mean of 1.32 mg/kg).Though there was no statistical difference of soil iodine in different districts (P =0.131), soil iodine content correlated positivelywith water iodine content. Conclusion: lodine concentration in salt accords with national policy of adding iodine in salt. Forelandhas more iodine in water than mountain area. The data reflected that water and soil iodine in foreland area was not high, whichsuggests universal iodized salt should be necessary. Environment iodine has relatively close association with pollution.Key words: lodine, Salt, Water, Soil, Coastdoi: 10.1631/jzus.2005.B1200Document code: ACLC number: R12; R581INTRODUCTION(WHO, 2002). Although the number of iodine defi-Significantly close relationship exists amongciency disorders affecting people is declining, on aenvironment, health and disease such as thyroid dis-global scale the number of affected people is still overease associated with iodine metabolism. Iodine has740 million which is 13% of the world's populationlong been recognized as an essential micronutrient forwith 30% of the remainder being at risk (WHO, 2002).Human iodine intake is closely related to iodineThyroid disease is closely associated with absorptionconcentration of water, soil and salt. Iodine concen-of iodine in food. Its deficiency causes goiter andtration in water and soil reflects the environmentaldifferent forms of physical and mental retardationiodine distribution, and is also an important index ofhuman s natural iodine intake and an indirect index ofenvironmental pollution. In recent years argument has"Project (No. C200221) supported by the Environmental Protectionalways existed whethor h“11 nfintinp intakeFoundation of Hangzhou City, Chinahas impact or not中国煤化工hyroidfYHCNMH G .Lu et al.1J Zhejiang Univ SCIENCE B 2005 6(12):1200-12051201disease. Hangzhou famous for Westlake in Zhejiang lodine assayProvince is located in the China foreland. In order toSalt, water and soil iodine was detected by ar-get the statistics on proper iodine addition in salt, and senic-cerium redox method. Reaction indicator andon prevention and cure of iodine related disease, inseconds- counter were used to indicate reaction endJune 2005 we conducted for the first time survey of point and time. As there was a linear correlation be-iodine concentration of salt, water and soil in the tween the logarithm of iodine concentration and theHangzhou area.logarithm of reaction time, iodine concentration insolution could be calculated by double logarithmicregression equation. Staff in the Center of DiseaseMATERIALS AND METHODSControl of Zhejiang Province did the detection ofiodine content. Water iodine-detection kit was pro-Sources of materialsduced by Wuhan Zhongsheng Biochemical Tech-(1) Iodized salt in different supermarkets, (2)nique Limited Company in China. The laboratorydrinking water (tap water in towns, well water orprocedures are described below: (1) Salt samplesspring water in villages) and water samples fromwere dissolved in distilled water and water samplesditches, lakes, rivers, (3) soil. All the samples men-were detected directly. Soil samples were incineratedtioned above were collected randomly from theat 550 °C for 4 h with mixed alkalinous compoundingchemicals including potassium carbonate, zinc sulfate,potassium chlorate and sodium chloride. The ash leftwas dissolved in distilled water and the supernatantSample collction methodsWe chose an ecosphere in the south, west, north,was removed for detection; (2) A pipette was used toeast and center of the study area as shown in Fig.1 andaccurately transfer 1.0 ml of standard io-collected samples including water from ditches, lakes,dine-detection solution and water or solution samplerespectively into test tube (There were two kinds ofrivers, well water, tap and superficial soil. The re-standard iodine- detection solution. One for low watersearch team members were mainly from the Depart-iodine concentration is 2~10 ug/L and the other forment of Endocrinology of Sir Run Run Shaw Hospital,high concentration of 10~80 μg/L); (3) Reducer of0.5and received unified training to guarantee the qualityml was added into each tube and joggled; (4) Indica-control. All the sampling bottles were soaked in di-tor of 0.5 ml was added into each tube and joggled; (5)luted hydrochloric acid, cleaned and heated dry.One tube was chosen. Sample injector was used torapidly add 0.5 ml oxidant into the tube while theseconds-counter was started. After the tube was jog-gled, the solution color turned blue. White paper wasused as background to observe the changing of color.With continuing reaction, the color turned from blueHangzhouto amethyst and finally to red. The seconds-counterwas stopped when the amethyst just turned red andLin'anBaythe time was recorded; (6) odine concentration wascalculated. As there was a linear correlation betweenthe logarthm of iodine concentration C (ug/L) [lgC]and logarithm of reaction time S (s) [lgsS], the regres-sion equation of standard curve [lgC= a+blgS] couldbe obtained by computer. With this equation andsample reaction time, sample iodine content (μg/L)Fig.1 Geographic instructioncould be calculated. Unit (μg/L) of salt and soil wasHangzhou including Yuhang， Jianggan, Xiacheng,converted to another unit (mg/kg).Shangcheng and Xihu districts is along the QiantangRiver. Fuyang is a plain region of the Fuchun River'sdrainage basin upstream the Qiantang River flowing intoStatistical analysisHangzhou Bay in the East China Sea. Lin'an is inComparison W| 中国煤化工Win-mountain areadows SPSS 13.0 sofYHCNM HG1202Lu et al.1J Zhejiang Univ SCIENCE B 2005 6(12):1200-1205RESULTS .lodine concentration of well or spring drinkingwater sample (Table 2)Iodine content in saltThe concentration range and mean of 19 samplesWe randomly obtained 108 salt samples from were 0.6~84.8 μg/L and 23.59 μg/L respectively.different supermarkets of different districts. The dis- Y uhang and Lin'an had the highest and lowest iodinetribution of iodine value was 20.0~37.8 mg/kg andcontent respectively. There was significant differenceiodine concentration in salt was 27.9+4.33 mgkg (P<0.001) among these districts.which accorded with Chinese official policy pub-lished in 1995.Iodine concentration of natural water source (Ta-ble 3)Iodine concentration of tap water sample (TableTwenty-two samples were gathered. The con-centration range and mean were 1.4~ 39.9 ug/L andThirty-four 0.6~9.9 ug/L (mean of 4.30 ugL) 12.72 μg/L respectively. The natural water sourcetap water samples were collected. Tap water sample iodine concentration in natural ditches, lakes and riveriodine concentration was highest in Y uhang district(Fuchun River) differed significantly (P=0.001). Thend lowest in Lin' an City, there was significant dif- muddier the water was, the higher was the iodineference (P<0.001) between the two values.content.Table 1 Tap water iodine concentrationlodineSig. (-J)(I) Districtcone(J) District. L-AF-YX-C，S-CX-H J_GY-HL-A1.45+0.930.5030.0070.0060.000 0.0002.01+0.16 0.5030.0260.0240.0220.000Hangzhoul X-C3.80+0.35 0.0070.9790.9380.001 0.000Hangzhou2 S-C3.82+0.19 0.007 0.0240.959 0.001 0.000Hangzhou3 X-H3.86+0.22 0.006 0.0220.9590.001 .Hangzhou4 J-G0.0010.147Hangzhou5 Y-H7.88+0.44 0.000000Total34 4.30+2.43F= 17.858, P<0.001Lin'an=L-A, Fuyang=F-Y, Yuhang=Y -H, Jianggan=J-G, Xiacheng=X-C, Shangcheng- s-C, Xihu=X-H; Statistics showed that all thepaired groups had significant difference except Xihu and Xiacheng district (P=0.938), Xihu and Shangcheng district (P=0.959), Yuhangand Jianggan district (P -0.147), Xiacheng and Shangcheng (P=0.979)Table 2 Well (or spring) water iodine concentrationTable 3 Physical environment water iodine concentra-_Sig. (-J)tionodine conc.(1) DistrictN lodi() District(ug/L)Iodine conc.L-A F-Y J-G Y-H(I) Water source I(J) Water source(μg/L)4 1.45+0.93一0.660 0.041 0.0000Rivers Lakes DitchesF_Y5.20+2.30 0.660- 0.077 0.000Rivers5 5.202.300.684 0.001Hangzhou4J-G 5 20.18+17.38 0.041 0.077- 0.000Lakes6.99+4.10 0.684Hangzhou5Y-H_ 5 63.10+16.58 0.000 0.000 0.000Ditches922.00+10.91 0.001 0.00119 23.59+27.74 F=24.693, P<0.00122 12.72+10.72F=11.505, P=0.001Comparison between every two groups showed that there was sig-nificant between Lin'an and Yuhang district (P=0.000), JianganNo statistical difference existed between water of rivers and lakesand Yuhang (P=0.000), Fuyang and Yuhang (P-0.000). No statis-(P=0.684). Significant difference existed between water of lakes andtical difference was found to exist between Lin ' an and Fuyang dis-natural diches (P= 0.001), water of rivers and natural ditchestrict (P=0.660), Fuyang and Jianggan (P- =0.077)(P=0.001)中国煤化工MHCNM HGLu et al.1J Zhejiang Univ SCIENCE B 2005 6(12):1200-12051203Result of comparing iodine content among tap Comparison of iodine concentration between wa-water, well or spring water and natural water ter and soil sample (Fig.3)source sample (Fig.2)Fig.3 shows that the curves of concentration ofWe collected 75 water samples with iodine iodine in water and soil have similar rising trend inconcentration of 0.6~84.8 ug/L (mean of 11.66 μg/L). direction. The higher the water iodine content was,Well or spring water had highest iodine content of the higher was the soil iodine content. lodine contentdrinking water samples, followed by natural water in the environment was found to decrease with in-source, with tap water having the lowest content. creasing distance from the sea.Significant difference (P<0.01) existed. Undergroundwater had more iodine than surface water.3o -✧-Soil -0- Water25.00 |25 t20.0020 t15.0010.005.00 |Lin'an Fuyang Westlake Jianggan Yuhang0.00Fig.3 The trend of iodine concentration in soil andTap NaturalWellwaterWater sampleFig.2 Water iodine compared in Hangzhoulap: Tap water sample; Natural: Natural water s. sample:sampleWell:spring drinlwater sample,DISCUSSION AND CONCLUSIONConc.: Concentration;Represents, values stiticallyhigher than tap water (P=0.045); * Represents valuesHuman health including character developmentstatistically higher than tap waterP<0.001) and naturalwater source (P- 0.025)and mental change is generally associated withphysical environment. Air, soil and water are neces-Iodine content in soil of Hangzhou area (Table 4)sary for all life. Some ingredients in soil and waterForty-six soil samples were collected in whichplay an important role in human life's development.iodine concentration was 0.11~2.93 mgkg (mean of As an important endocrine gland maintaining life1.32 mgkg). The statistics indicated there was high- activity, the thyroid secretes thyroxine which pro-est iodine content in Xihu district and lowest in motes growth and development of bone, muscle,Lin'an City.height and weight, and maintains the stabilization ofenergy and material metabolism (Fuge and Johnson,Table 4 Soil iodine1986). It is known that iodine is necessary for theIodinesynthesis of thyroxine. lodine content in soil and(I) District N conc.(J) District(ug/L) L-A F-Y J-G Y-H X-Hwater is directly associated with the content of humanL-A8 0.76+0.33 - 0.525 0.123 0.036 0.040food iodine and affects survival rate and living quality.FY10 1.02+0.11 0.5250.316 0.102 0.109Both extremely high and low iodine intake has ob-Hangzhou4101.41+0.25 0.1230316 - 0.498 0.485vious damage to human: (1) hyperthyroidism, (2)hypothyroidism and young children's mental retar-Y-H101.68+0.21 0.036 0.102 0.498- 0.952 dation due to hypothyroidism, (3) thyroid carcinoma,Hangzhou38 1.71+0.48 0.040 0.109 0.485 0.952(4) autoimmune thyroid diseases. A body of clinicaland epidemiologic evidence points to excessive in-Total 46 1.32+0.14F=2.047, P=0.131gestion of iodine as an environmental agent (Rose etSatisies ofa avery twoa groups let had no sgficon dferere al, 2002). As inducers of autoimmune thyroid dis-excluding Lin' an City and Xihu district (P=0.040), Lin' an City andYuhang district (P=0.036)eases, environment中国煤化工gravateYHCNM HG1204 .Lu et al. IJ Zhejiang Univ SCIENCE B 2005 6(12):1200-1205already existing autoimmune thyroid diseases (Mar- gic disease due to water pollution and promote sus-rack et al., 2001).tainable development of our natural resources andThis survey revealed that water iodine contentsociety.was highest in Hangzhou, that Fuyang was the secondOn the basis of our standards that define waterhighest, and that Lin'an water iodine content was the iodine value<10 ug/L as iodine-deficient district andlowest. The data indicate that water sources of fore- water iodine value> 200 μgL as iodine-abundantland have higher iodine content than those of inland. district, China is an iodine-deficient country whoseAlthough statistical difference did not exist in soil endemic area involves 29 provinces, including moreiodine concentrations of different districts, their ab-than 7000000 iodine-deficient patients compromis-solute values were similar to those of water samples. ing more than half of the patients in the world (ZhengSo we considered that iodine content in the environ- et al, 2002). Distribution of soil iodine values inment decreases from high to low level with increasingChina (A level) is 0.39~14.71 mg/kg (mean of 3.76distance from the sea, probably because during the mg/kg). Because mean of iodine content in water andprocess of forming land plain area continuously bat- soil samples is 11.66 μgL and 1.32 mg/kg respec-tered and infiltrated by seawater, the iodine content of tively, generally the Hangzhou area still lacks iodineoil and freshwater in this area is high. Foreland although it is in the China foreland. Normal adults andresidents have more iodine intake than inland resi- children need 150 ug and 200 ug per day respectivelydents due to the water they drink.(Chen, 2001). According to normal amount o1We also found tap water from factory had less drinking water per day iodine intake from water plusiodine than that of the main drinking water source in intake from food still cannot reach the standard. Inthe countryside. Water management includingI 995, our country reformed the policy on iodized saltprecipitation, filtration and disinfection when part of in order to ameliorate the iodine-deficient condition.iodine is absorbed and volatilized probably results in Iodine values in salt samples accords with nationalthis phenomenon. Because well water directly per-standard. If we take 3~5 g salt everyday routinelymeates through the soil and soil iodine content (Chen, 2001), we can have 100~150 ug iodine intake(mean=1.32 mg/kg) was higher than water iodinewhich mainly satisfies human requirement for iodine.(mean=11.66 μg/L), underground has even moreThe relationship between the iodine intake leveliodine. Most drinking water sources in the country- of a population and the occurrence of thyroid diseasesside are well supplying mainly underground water. in the population is U-shaped with an increase in riskThis caused the distinction of iodine intake throughfrom both low and high iodine intakes (Chen et al,water. The amount of town residents’ water iodine 2002; Laurberg et al, 2001). Endocrinologists nowintake may be smaller than that of countryside resi- have complete understanding of the relation betweendents' on the basis of the analysis above.iodine and incidence rate of goiter by combiningIodine content indirectly reflects environmental epidemiological investigations and experiments withpollution especially of the water. When clear water is animal models. Severe iodine deficiency with medianpolluted, iodine cannot be easily precipitated from it, 24-h urinary iodine excretion below 25 mg needsinfiltrated into it and voltilized from it, leading to" immediate attention and correction. Less severe io-more solutes in the water. This survey revealed that dine deficiency with median urinary iodine excretionditches and Fuchun River have the highest and lowest below 120 mg per 24 h is associated with multi-iodine concentrations respectively and significant nodular autonomous growth and function of the thy-difference (P<0.01) existed between them. The roid gland leading to goiter and hyperthyroidism inmuddier thecontent, especially near large factories. The pollution dine intake, the earlier and more prominent are theof ditches and lakes may be the worst, although it isabnormalities. At the other end of the spectrum, se-possible that Fuchun River which is one of the most verely excessive iodine intake starting at medianimportant water systems in Hangzhou is still less urinary iodine excretion levels of around 800 mg perpolluted. That makes us think highly of environ- 24 h is associated with a higher prevalence of thyroidmental protection to decrease the incidence of ecolo- hypofunction and中国煤化工ber ofYHCNM HGLu et al.1J Zhejiang Univ SCIENCE B 2005 6(12):1200-12051205studies indicated that moderate and mild iodine ex- Referencescess (median urinary iodine >220 mg per 24 h) are Chen, H.Z., 2001. Practial Intermal Medicine. People' Medi-associated with a more frequent occurrence of hypo-cal Publishing House, Beijing, p.883-885 (in Chinese).thyroidism, especially in elderly subjects (Laurberg etChen, B.H, Guo, W.H, Shi, W., Kan, H.D, 2002. Risk as-sessment of extremely high or low necessary trace ele-al, 2001). Finally the bottom represents sporadicments intake. Chin. J. Prev. Med, 36:414-417.goiter which could not be a public health problem. In Fuge, R., Johnson, C.C, 1986. The geochemistry of iodine.short, extremely high or low iodine intake harmsEnviron. Geochem. Health, 8:31-54.human health, so the mistake of taking universal io- Kelly, F.C, Snedden, W.w., 1960. Prevalence and Geo-dized salt regardless of iodine content in the envi-graphical Ditribution of Endemic Goitre. In: WHOMonograph Series. WHO, Geneva, p.27-233.ronment should be corrected. Some factories nowLaurberg, P., Bulow, P.I, Knudsen, N, Ovesen, L., Andersen,producing food with excessive iodine will cause se-S., 2001. Environmental iodine intake affects the type ofvere overflow of iodized food.nonmalignant thyroid disease. Thyroid, 11:457-469.Finally, research about incidence rate of thyroiddoi:10.1089/105072501300176417.disease along the Zhejiang Province coast has notyet Mrrack, P, Kapplr, J, Kotzin, B.L, 2001. Autoimmunefinished. The results of relationship between the en-disease: why and where it occurs. Nat. Med, 7:899-905.doi: 10.1038/90935.vironment iodine and prevalence of thyroid diseaseRose, N.R., Bonita, R, Burek, C.L, 2002. lodine: an envi-will be presented.ronmental trigger of thyroiditis. Autoimmun.Rev,1:97-103. doi:10.1016/S 1568-9972(0100016-7.WHO, 2002. Micronutrient Deficiency- -lodine DeficiencyDisorders. http:www.who.int/nutidd.htm.Zheng， Q.S, Dai, Z, Ma, Y., 2002. Current situation andstrategy of prevention and cure of iodine-deficiency dis-eases in China. Chin. J. Epidemiol, 23:243 (in Chinese). .JzusEditors-in-Chief: Pan Yun-he & Peter H. Byers(ISSN 1673-1581, Monthly)Journal of Zhejiang UniversitySCIENCE Bhtp://www.zju.edu.cn/jzusJZUS-B focuses on“Biomedicine, Biochemistry & Biotechnology”Welcome Contributions to JZUS-Bjzus@zju.edu.cnJournal of Zhejiang University SCIENCE B warmly and sincerely welcome scientists all over theworld to contribute to JZUS-B in the form of Review, Article and Science Letters focused on Bio-medicine, Biochemistry and Biotechnology areas. 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