Water Iodine Level Research Articles

Iodine Excess Is Associated with Thyroid Dysfunction Among the Elderly.

The relationship between high water iodine levels and thyroid dysfunction in the elderly remains poorly understood. This study aimed to elucidate how excessive iodine in drinking water affects iodine nutrition and thyroid function in the elderly population. This cross-sectional study was performed in the elderly in Yuncheng, Heze, Shandong. We identified a total of 385 patients with thyroid dysfunction and 385 propensity score-matched controls with euthyroid. Water, urinary, and blood samples were collected to detect the concentrations of iodine in water and urine, as well as thyroid hormones. The median (IQR) iodine concentrations in cooking water and drinking water for the total population were 294.99 (48.99, 478.14) µg/L and 172.87 (20.87, 462.13) µg/L, respectively. Among the elderly, median (IQR) urinary iodine concentration (UIC) was 394.20 (169.47, 764.41) µg/L, and 24-h urinary iodine concentration (24-h UIE) was 523.04 (277.84, 910.76) µg/day. Subjects with thyroid dysfunction reported higher intake of iodine from water (P < 0.001) and urinary iodine levels (P < 0.001) than controls. Logistic regression analysis showed thyroid dysfunction was associated with higher risks of elevated iodine concentrations in cooking water (OR 1.957, 95% CI 1.413-2.711), drinking water (OR 2.206, 95% CI 1.607-3.027), UIC (OR 3.612, 95% CI 2.494-5.230), and 24-h UIE (OR 2.568, 95% CI 1.784-3.698), indicating increased thyroid dysfunction risk among the elderly with high water iodine levels. Elevated iodine levels in water are associated with an increased risk of thyroid dysfunction among the elderly. Clinical trial registry number: Medical Ethics Committee of Tianjin Medical University; Trial registration number: NCT05716191, date of registration was December 08, 2023.

Following the footsteps of goiter expeditions in the Urals

Historically, regions with low levels of iodine in soil and water have been associated with a higher prevalence of goiter. The link between iodine deficiency and goiter has led to innovative efforts to address this problem. The article discusses the history of the study of endemic goiter in the Urals, presents the results of a large complex work of goiter expeditions of 1929-1934, thanks to which numerous data were obtained that served as the basis for the organization of therapeutic and mass preventive anti-goiter measures in places where goiter is endemic.

Association between different water iodine exposures and thyroid cancer: A retrospective study of high water iodine areas in China from 2009 to 2020

In recent years, the incidence of thyroid cancer has been on a significant rise worldwide, and a number of environmental factors have been suspected to be risk factors for thyroid cancer, especially the relationship between iodine intake and thyroid cancer has attracted attention. In this study, we want to assess the relationship between different water iodine exposures and thyroid cancer incidence before and after water alteration in areas with high water iodine in China. Thyroid cancer patients (2009–2020) were enrolled at two hospitals, both in Heze City, Shandong Province, an area with high water iodine levels. According to the criteria of the study, 5826 cases out of 8785 cases were selected for inclusion in the study. Before and after water alteration, the incidence of thyroid cancer was highest in areas with water iodine concentrations of 200–300 μg/L in high iodine areas. In areas where water iodine decreased to adequate iodine levels, there was a strong negative correlation between the decreased level of water iodine and the incidence of thyroid cancer. In addition, in cases with pathology reports, we found that the greater the decrease in water iodine values, the markedly smaller the maximum diameter of the thyroid cancer lesions. Taken together, these findings suggest that we should continue to monitor the incidence of thyroid cancer in areas with high water iodine and continue to optimize population iodine intake to reduce the incidence of thyroid cancer.

Examining the influence of desalinated water on iodine concentration in tap water in Israel

IntroductionIn Israel, desalinated water is a major source of drinking water. Previous studies have suggested that the levels of iodine in water provided by authorities may not accurately reflect the levels reaching end-users. Materials and MethodsWe analyzed 21 tap water samples collected from different localities across Israel, 13 post-treated desalinated water samples from three of the largest Israeli desalination plants, and several natural water samples. An improved method of ICP-MS developed in our laboratory was used to analyze the content of iodine and other macro-elements, and determination of iodine was performed in alkaline media. ResultsOur results showed that it is possible to distinguish between sample groups based on iodine concentration, water hardness, and Ca/Mg ratio. The median iodine concentrations for four groups of tap water samples ranged from 0.3 to 12.3 µg/L, which is lower than the concentrations previously reported by other researchers in Israel. Based on typical consumption, the water samples can provide no more than 3.39% of the recommended dietary allowance level for iodine. The analysis of post-treated desalinated water samples indicated that these waters comply with industrial specifications but contain only trace concentrations of iodine and much less magnesium than recommended by different public health authorities for public consumption of drinking water. ConclusionThe total iodine concentrations found were lower than several observations reported in previous years in the literature. There are currently no strict regulations regarding iodine and magnesium levels in drinking and/or softened (desalinated) water, but the intensive desalination plant application is already exhibiting a negative impact on public health. Further investigations are needed, but the present study provides useful insights for developing an effective policy to ensure adequate iodine supply for the population of Israel through drinking water.

Iodine level of goats from Shiwalik and middle mountains of north-west Himalayas in relation to soil, fodder, and water status

A baseline survey was carried out to determine the iodine status of goats and its relationship with the levels of soil, water, and fodder samples collected from different agro-climatic zones (sub-tropical, lower, and upper-intermediate) of the Jammu division. A total of 74 blood and 60 milk samples from goats, as well as soil (50), water (50), and fodder (56) samples, were collected. Plasma inorganic iodine (PII), milk inorganic iodine (MII), iodide ion (I-), and thyroid hormone (T3 and T4) levels were measured along with biochemical parameters. The average PII, I-, and MII concentrations of goats from unorganized farms were 55.99±4.56 ng/ml, 1.37±0.11 ppm, and 47.3±5.68 ng/ml compared 74.68±8.40 ng/ml, 1.43±0.11 ppm and 62.01±8.55 ng/ml, respectively from the organized farm. Based on PII level, 71.62% of goats had moderate deficiency (level 50-100 ng/ml) and 28.37% had severe deficiency (level &lt;50 ng/ml). The average levels of iodine in soil and water were 0.24 ppm and 0.06 ppm, respectively. Rabi and kharif fodders showed average iodine levels of 1.25 ppm and 0.37 ppm, respectively. Significant changes were recorded in glucose, HDL and T4 levels. Pearson correlation performed between PII (ng/ml) and biochemical parameters established correlation with T4 (r = -0.465), glucose (r = 0.510), HDL (r = -0.355) and cholesterol (r = 0.271). The study concluded that iodine deficiency is prevalent in the goat population due to lower levels in the environment implying an urgent need for regular supplementation in the diet.

Effect of different iodine levels on the DNA methylation of PRKAA2, ITGA6, THEM4 and PRL genes in PI3K-AKT signaling pathway and population-based validation from autoimmune thyroiditis patients.

Autoimmune thyroiditis (AIT) is one of the most common autoimmune endocrine diseases. The currently recognized causes are genetic susceptibility, environmental factors and immune disorders. It is important to clarify the pathogenesis for the prevention, diagnosis, treatment of AIT and scientific iodine supplementation. This study analyzed the DNA methylation levels of PRKAA2, ITGA6, PRL and THEM4 genes related to PI3K-AKT signaling pathway, compared the DNA methylation levels between cases and controls from different water iodine levels in Shandong Province of China, and evaluated the contribution of PI3K-AKT signaling pathway-related genes in AIT. A total of 176 adult AIT patients were included from three different water iodine areas, and 176 healthy controls were included according to gender, age and BMI. According to the results of the Illumina Methylation 850K BeadChip in our previous research, the significant methylation differences of genes on the PI3K-AKT signaling pathway related to AIT were determined. The MethylTarget™ assay was used to detect the methylation levels of the target genes, and real-time PCR experiments were used to verify the mRNA expression levels. Compared with the control group, PRKAA2_3 and 15 CpG sites were hyper-methylated. ITGA6 gene and 2 CpG sites were hypo-methylated in AIT cases. The mRNA expression of ITGA6 gene was negatively correlated with the DNA methylation levels of ITGA6 gene and 2 CpG sites. Compared with cases and controls in areas with different water iodine levels, methylation differences were mainly in PRKAA2 and ITGA6 genes. The methylation levels of PRKAA2_1 and PRKAA2_3 were positively correlated with age. The methylation levels of PRL and THEM4 genes were negatively correlated with age. The methylation level of PRKAA2_3 was positively correlated with FT4. In summary, we identified aberrant DNA methylation levels of PRKAA2 and ITGA6 genes related to PI3K-AKT signaling pathway in the blood of AIT patients. Both iodine supplementation after long-term iodine deficiency and iodine excess can affect the DNA methylation levels of PRKAA2 and ITGA6 genes, and the former affects more obviously. In ITGA6 gene, this aberrant epigenetic modification is associated with the increased mRNA expression.

The Whole Blood DNA Methylation Patterns of Extrinsic Apoptotic Signaling Pathway Related Genes in Autoimmune Thyroiditis among Areas with Different Iodine Levels.

Autoimmune thyroiditis (AIT) has a complex etiology and the susceptibility to it is determined by a combination of genetic and environmental factors, although these are not yet fully understood. The present research aimed to explore the DNA methylation patterns in whole blood of extrinsic apoptotic signaling pathway related genes in AIT among areas with different iodine levels. We selected the iodine-fortification areas (IFA), iodine-adequate areas (IAA) and water-based iodine-excess areas (IEA) from Shandong Province of China as survey sites. Totally 176 AIT cases and 176 controls were included. MethylTargetTM and QT-PCR technology were used to detect candidate genes' DNA methylation levels and mRNA expression levels, respectively. We found that DAPK1 DNA methylation levels in AIT cases (especially in female) were significantly higher than controls (t=2.7715, P=0.0059; t=2.4638, P=0.0143 in female). There were differences in DAPK1(t=2.5384, P=0.0121), TNFSF8(t=2.1667, P=0.0334) and TNFAIP8(t=2.5672, P=0.0121) genes methylation between cases and controls with different water iodine levels. The mRNA expression of DAPK1(t=4.329, P<0.001) and TNFAIP8(t=3.775, P<0.001) in the cases were increased. We identified the differences in the DNA methylation status of the extrinsic apoptotic signaling pathway related genes between AIT and controls and in different iodine levels areas. The results were verified at the mRNA level. The environmental iodine may affect DNA methylation to some extent.

What Iodine Intervention Measures Should Be Taken in Different Water Iodine Areas? Evidence from a Cross-sectional Chinese Survey.

The aim of this study was to assess the population's iodine nutrition and thyroid diseases in different water iodine areas and to offer suggestions to the governments of different countries to adjust the present policy in different water iodine areas. A cross-sectional survey was conducted in different water iodine areas in China. Urinary iodine, water iodine, salt iodine and thyroid function were determined. The thyroid volumes and nodules were measured by ultrasound. Upon categorization by water iodine level for the 10.0 ~ 39.9μg/L, 40.0 ~ 100.0μg/L and 100.1 ~ 150.0μg/L areas, in adults, the prevalence of subclinical hypothyroidism was 9.28%, 5.35% and 11.07%, and the median urinary iodine (MUI) was 153.7μg/L, 189.8μg/L and 317.0μg/L; in children of the three areas, the prevalence of goitre was 3.83%, 4.47% and 16.02%, and the MUI was 164.1μg/L, 221.0μg/L and 323.3μg/L; in pregnant women of those areas, the MUI was 148.6μg/L, 176.9μg/L and 324.9μg/L. Logistic regression results indicated that low iodine intake was a risk factor for developing hypothyroxinaemia in pregnant women. The iodine status of pregnant women is insufficient in areas with a median water iodine level of 10.0 ~ 39.9μg/L. Low iodine intake increases the risk of developing hypothyroxinaemia in pregnant women. The iodine status of adults and children is excessive, and the iodine status of pregnant women is above the requirements in areas with a median water iodine concentration of 100.1 ~ 150.0μg/L. Iodized salt, especially for pregnant women, should be supplied in areas with a median water iodine concentration of 10.0 ~ 39.9μg/L to improve the iodine status of pregnant women. Supplying non-iodized salt is not enough to protect local residents from the harm from excess iodine in areas with a median water iodine concentration above 100.0μg/L.

DNA Methylation Patterns in the HLA-DPB1 and PDCD1LG2 Gene Regions in Patients with Autoimmune Thyroiditis from Different Water Iodine Areas.

Background: Epigenetic disorders play an important role in the pathogenesis of autoimmune thyroiditis (AIT). Therefore, the study of the possible role of DNA methylation in AIT is of great significance to explore the pathogenesis of AIT. Methods: From May 2019 to June 2019, whole blood samples were collected from 176 AIT patients and 176 controls from different water iodine levels in Shandong Province, China. We used the Illumina Methylation 850K BeadChip to determine significant differences in methylation status of genes and used the MethylTarget™ assay to verify the methylation level in 176 cases and 176 controls. The relative mRNA levels of genes were detected by quantitative real-time-polymerase chain reaction. Results: There were multiple differential methylation sites in the HLA-DPB1 and PDCD1LG2 genes between the case and control population with different water iodine levels. Some target regions of HLA-DPB1 and PDCD1LG2 genes were negatively correlated with relative mRNA expression in the case and control populations and with different water iodine levels. Conclusions: There is differential methylation status in genomic DNA in patients with AIT. The methylation patterns of HLA-DPB1 and PDCD1LG2 genes related to cell adhesion molecule pathway may be different based on different water iodine levels. HLA-DPB1 and PDCD1LG2 genes related to the cell adhesion molecules pathway may play a role in the development of AIT. This study is registered with Chinese Clinical Trial Registry, www.chictr.org.cn, number ChiCTR2000039105.

The Effects of Long-Term High Water Iodine Levels in the External Environment on the Carotid Artery

Iodine excess typically affects thyroid function in the human body and may damage carotid artery. Four investigation plots with different water iodine levels were selected in Shandong Province, China. These included a low, medium, and high iodine group and an iodine excess group whose water iodine content was < 10, 50–150, 150–300, and > 300 μg/L, respectively. Residents aged 20–65 years answered a questionnaire and underwent carotid artery ultrasonography, and their height, weight, and urinary iodine concentrations were measured. A total of 2026 individuals participated in the study. Urinary iodine concentration increased with increased water iodine levels. The medial thickening rate and intimal roughness rate in the iodine excess group were significantly higher than in the other three groups. After controlling for factors such as gender, age, and BMI, iodine excess remained as a risk factor for carotid intima-media thickening. Excess water iodine in the external environment is a risk factor for intima-media thickening of the carotid artery, suggesting that iodine excess may cause vascular injury and promote atherosclerosis.

Impact of removing iodized salt on the iodine nutrition of children living in areas with variable iodine content in drinking water

Excess iodine in drinking water has emerged as a public health issue in China. This study assesses the effectiveness of removing iodized salt on reducing the iodine excess in populations living in high-iodine areas and also to identify the threshold value for safe levels of iodine in water. Twelve villages from 5 cities of Hebei Province with iodine content in drinking water ranging from 39 to 313µg/l were selected to compare the urinary iodine content of children aged 8-10years before and after removing iodized salt from their diet. For 3 villages where median water iodine content (MWIC) was below 110µg/l, following the removal of iodized salt (the intervention), the median urinary iodine content (MUIC) reduced to under 300µg/l decreasing from 365, 380, 351 to 247, 240, 281µg/l, respectively. However, the MUIC in the 9 villages with MWIC above 110µg/l remained higher than 300µg/l. The children's MUIC correlated positively with the MWIC in the 12 villages (p≤ 0.001). The linear regression equation after removing iodized salt was MUIC=0.6761MWIC+225.67, indicating that to keep the MUIC below 300µg/l (the iodine excess threshold recommended by the WHO) requires the MWIC to be under 110µg/l. Removing iodized salt could only correct the iodine excess in the population living in the areas with MWIC below 110µg/l. In the areas with water iodine above 110µg/l, interventions should be focused on seeking water with lower iodine content. This study suggests a threshold value of 110µg/l of iodine in drinking water to maintain a safe level of dietary iodine.

Geographical distribution patterns of iodine in drinking-water and its associations with geological factors in Shandong Province, China.

County-based spatial distribution characteristics and the related geological factors for iodine in drinking-water were studied in Shandong Province (China). Spatial autocorrelation analysis and spatial scan statistic were applied to analyze the spatial characteristics. Generalized linear models (GLMs) and geographically weighted regression (GWR) studies were conducted to explore the relationship between water iodine level and its related geological factors. The spatial distribution of iodine in drinking-water was significantly heterogeneous in Shandong Province (Moran’s I = 0.52, Z = 7.4, p < 0.001). Two clusters for high iodine in drinking-water were identified in the south-western and north-western parts of Shandong Province by the purely spatial scan statistic approach. Both GLMs and GWR indicated a significantly global association between iodine in drinking-water and geological factors. Furthermore, GWR showed obviously spatial variability across the study region. Soil type and distance to Yellow River were statistically significant at most areas of Shandong Province, confirming the hypothesis that the Yellow River causes iodine deposits in Shandong Province. Our results suggested that the more effective regional monitoring plan and water improvement strategies should be strengthened targeting at the cluster areas based on the characteristics of geological factors and the spatial variability of local relationships between iodine in drinking-water and geological factors.

The Standard, Intervention Measures and Health Risk for High Water Iodine Areas

Our study aims to clarify the population nutrient status in locations with different levels of iodine in the water in China; to choose effective measurements of water improvement(finding other drinking water source of iodine not excess) or non-iodised salt supply or combinations thereof; to classify the areas of elevated water iodine levels and the areas with endemic goiter; and to evaluate the risk factors of water iodine excess on pregnant women, lactating women and the overall population of women. From Henan, Hebei, Shandong and Shanxi province of China, for each of 50∼99 µg/L, 100∼149 µg/L, 150∼299 µg/L, and ≥300 µg/L water iodine level, three villages were selected respectively. Students of 6–12 years old and pregnant were sampled from villages of each water-iodine level of each province, excluded iodized salt consumer. Then the children's goiter volume, the children and pregnant's urinary iodine and water iodine were tested. In addition, blood samples were collected from pregnant women, lactating women and other women of reproductive age for each water iodine level in the Shanxi Province for thyroid function tests. These indicators should be matched for each person. When the water iodine exceeds 100 µg/L; the iodine nutrient of children are iodine excessive, and are adequate or more than adequate for the pregnant women. It is reasonable to define elevated water iodine areas as locations where the water iodine levels exceed 100 µg/L. The supply of non-iodised salt alone cannot ensure adequate iodine nutrition of the residents, and water improvement must be adopted, as well. Iodine excess increases the risk of certain thyroid diseases in women from one- to eightfold.

The iodine status in Hangzhou, Zhejiang province 2010

To explore the iodine level in the environment and the iodine status among the general population as well as the prevalence of thyroid nodules in Hangzhou city. Relationship between the prevalence of thyroid nodules and the policy of universal salt iodization in Hangzhou was also analyzed. Questionnaire, a 3-day weighed dietary record method, and 3 days' 24-hour dietary recall method were used to understand the iodine nutrition status and dietary intake of iodine among the general population in the city. Drinking water, edible salt and morning urine were collected to determine iodine content. All objects under survey underwent the thyroid B ultrasonic examination. Statistical analysis was done by SPSS 13.0 and SAS 9.1. (1) In total, 12 620 effective questionnaires were available, with 221 water samples, 12 730 urine samples, and 3593 salt samples collected. 12 515 objects underwent B ultrasonic examination, and 1848 received dietary investigation. (2) Water iodine level of Hangzhou was in the range of 0.20 - 5.99 µg/L, with the median level as 2.58 µg/L. (3) Average daily dietary intake of iodine for adult males in Hangzhou was 289.2 µg/d. The contribution of iodine intake from iodized salt was 74.4%. (4) The median of Hangzhou residents' urinary iodine was 178.80 µg/L, with the urinary iodine levels at 100 µg/L-, 200 µg/L-, < 100 µg/L, and ≥ 300 µg/L groups were 37.14%, 23.11%, 21.05%, and 18.69% respectively. Urinary iodine of pregnant women was 141.0 µg/L. (5) Incidence of thyroid nodules in females (28.6%) was higher than that of males (20.1%). The detection rate increased with age (6.4% at group 6-, 10.9% at 12-, 12.0% at 18-, 24.4% at 40-, and 38.8% at 65-); with the highest in urban area (29.8%), followed by suburbs (23.3%) and in rural area it showed the least (20.3%). Urinary iodine level was found lower among the population who had been detected with thyroid nodules (160.36 µg/L) than those among the undetected population (182.00 µg/L). Hangzhou appeared to be an area where the environmental was iodine deficient. Iodized salt was the major source of iodine intake. The iodine status among the general population seemed to be safe and suitable, but the iodine level for pregnant women was not sufficient. There was still no evidence indicating that the universal salt iodization policy in Hangzhou was associated with the prevalence of thyroid nodules.

Environmental implication of iodine in water, milk and other foods used in Saharawi refugees camps in Tindouf, Algeria

A cross-sectional survey among Saharawi refugees in four camps carried out in 2007 revealed enlarged thyroid volume and high urinary iodine concentration in women and school children. The purpose of this paper is to describe the content of iodine in food and water and explore whether any sources in the environment can explain the situation. Samples of water (n=143), milk (n=19) and salt (n=89) were collected. Different wells supplied the camps with water and the median iodine concentration was 108μg/L (range 55–545μg/L) and significantly higher in two of the camps (El Aiune and Ausserd; 300μg/L (range 55–545μg/L)), compared to the two other camps (Smara; 87μg/L (55–127μg/L) and Dakla; 70μg/L (55–96μg/L)). In local goat milk the median iodine concentration was 370μg/L (70–13,070μg/L). The median content of iodine in salt was 6μg/g (0–51μg/g). Water and local milk were the most important sources of iodine for women. High levels of iodine in water seem to be one of the main sources of iodine that affects humans as well as animals.

Determinants of iodine deficiency in school children in different regions of Ethiopia.

To determine the magnitude of goitre in school children and measure indicators of iodine deficiency including the most commonly consumed staple foods. A cross-sectional study. Ten villages from four administrative regions of Ethiopia. A total of 2485 randomly selected elementary school children were examined for clinical signs of goitre. Indicators of iodine deficiency disorders (IDD) assessed were urinary iodine excretion (UIE) rate, iodine concentration in water, the commonly consumed individual foods of plant origin and milk, and bacterial contamination of drinking water. The gross prevalence (mean of male and female values) among school children was 53.3%. The prevalence was higher in females (56.1%) than in males (50.8%). The highest prevalence (82 and 91%, respectively) were observed in the villages of Lotte and Kodowono and the lowest (31%) in the village of Abossara. Of the urinary measurements, 70% of the samples showed moderate and 30% mild iodine deficiency. Levels of iodine in water and individual food samples were low in general. Breast milk iodine content was similarly low and related to the maternal daily iodine intake which may affect the nutritional status of the nursing infant. The study also provides further evidence that coliforms and E. coli isolated from drinking water contribute to the high incidence of endemic goitre other than iodine deficiency. It is difficult to obtain a sufficient iodine intake in the survey villages as the individual foods are very low in the element. However, IDD can be prevented by ensuring normal iodine nutrition through instituting ways that avail iodinated salt to the survey population.

Rapid, specific determination of iodine and iodide by combined solid-phase extraction/diffuse reflectance spectroscopy.

A new, rapid methodology for trace analysis using solid-phase extraction is described. The two-step methodology is based on the concentration of an analyte onto a membrane disk and on the determination by diffuse reflectance spectroscopy of the amount of analyte extracted on the disk surface. This method, which is adaptable to a wide range of analytes, has been used for monitoring ppm levels of iodine and iodide in spacecraft water. Iodine is used as a biocide in spacecraft water. For these determinations, a water sample is passed through a membrane disk by means of a 10-mL syringe that is attached to a disk holder assembly. The disk, which is a polystyrene-divinylbenzene composite, is impregnated with poly(vinylpyrrolidone) (PVP), which exhaustively concentrates iodine as a yellow iodine-PVP complex. The amount of concentrated iodine is then determined in only 2 s by using a hand-held diffuse reflectance spectrometer by comparing the result with a calibration curve based on the Kubelka-Munk function. The same general procedure can be used to determine iodide levels after its facile and exhaustive oxidation to iodine by peroxymonosulfate (i.e., Oxone reagent). For samples containing both analytes, a two-step procedure can be used in which the iodide concentration is calculated from the difference in iodine levels before and after treatment of the sample with peroxymonosulfate. With this methodology, iodine and iodide levels in the 0.1-5.0 ppm range can be determined with a total workup time of approximately 60 s with a RSD of approximately 6%.

Endemic goiter associated with high iodine intake.

This study assessed the relation of iodine content of household water to thyroid size and urinary iodine excretion in an area with high iodine concentration in the water. The iodine content of household water and indicators of iodine status (thyroid size and urinary iodine level) were assessed in selected villages in Jiangsu Province, China. Water iodine levels were positively correlated with urinary iodine levels and indicators of thyroid size at the township level. Excess iodine in household water was the likely cause of endemic goiter and elevated urinary iodine levels in the study area. This finding affects public health policy on the institution of universal salt iodization for the elimination of iodine deficiency disorders.

Iodine concentrations in groundwater of northern Israel and their relation to the occurrence of goiter

A high incidence of goiter has been reported in the population of the northern Golan Heights in Israel. In the early 1960s, endemic goiter was reported from Upper and Western Galilee and from northwestern Samaria. Assuming that low levels of iodine in water contribute to the etiology of goiter, its concentration was investigated in the main water-sources of northern Israel. In atmospheric precipitation, the I −-content is <2 μg/l, in the tributaries of the river Jordan 2–2.5 μg/l and in Lake Kinneret, 13–15 μg/l. In groundwater, the I −-content fluctuates between<5 μg/l in the upper flow course and 10 μg/l downflow. The very low concentrations are explained by the low level of iodine in local atmospheric precipitation, by the filtering-effect of terra-rossa and rendzina soils, and by the rapid flow of groundwaters through thoroughly leached pipe-like karstic cavities which preclude enrichment of groundwaters in iodine. During the last decade, there have been no reports of endemic goiter in the northern part of the country. This is attributed to the establishment of integrated regional water-supply systems and to the operation of the National Water Carrier Network distributing water with an I −-content of 14 μg/l.