| Objective: Iodine is one of the trace elements essential for thyroid hormone synthesis and has a lot of affects on our health. Low iodine level results in iodine deficiency disorders (IDD), while high level of iodine cause iodine excess disorders (IED). Children affected by hypothyroidism caused by iodine deficiency suffer both mental and physical disabilities and had been the main public health concern in China. This situation was approved dramatically by an intervention method called universal salt iodization. Followed the USI intervention and advance in the treatment of iodine deficiency disease, the IDD is under control gradually. On the other hand, the disease caused by IED is becoming as a main player. In this study, we first survey the iodine level in water source and describe the data by geographic distribution, geomorphic characteristics and sedimental environment of geologic strata. Then investigate the prevalence rate of endemic goiter in school children, so master the effect of high iodine on people.Methods: Based on the historical data, 63 small towns were selected to investigate the iodine concentration of drinking water (ICDW) in the central and east area of Cangzhou. 5 villages were selected according to directions of east, west, south, north and center of each town. Drinking water samples from each village were determined for their water iodine concentration and the data was collected regarding the type of water source and the depth of wells. Water iodine concentration was determined by cerous sulfate catalytic spectrophotometry, and the distribution of water iodine was mapped by using Autodesk Map 3D. Thyroid of children aged 8~10 years in 14 small towns was diagnosed by palpating and diagnostic criterion was GB16004-1995 (Diagnostic and classificatory criteria of endemic goiter); urine samples were collected and urine iodine was determined by arsenic-cerium catalytic spectrophotometry. The database was created by Excel2003, and analyzed by SPSS13.0 software package.Results: A total of three hundred and fifteen water samples were collected and the median of water iodine (MWI) was 359.72μg/L. The lowest ICDW was 6.76μg/L and the highest ICDW was 1457.50μg/L. The ICDW in 272 samples was higher than 150μg/L, accounting for 86.35% of the total; the ICDW in 193 samples was higher than 300μg/L, accounting for 61.27%. The MWI was over 150μg/L in all 63 towns, and the MWI in 39 towns was over 300μg/L.15 out of 315 water samples were from hand-press well, and the MWI was 202.11μg/L; 295 samples were from driven well, and the MWI was 375.53μg/L; 5 samples were from water reservoir, and the MWI was 371.89μg/L. The median of well depth was 360m in 310 wells. The shallowest was 7m, and the deepest was 920m. The depth of 40 wells was below 40m, accounting for 12.90%, and the MWI was 176.55μg/L. The depth of 270 wells was over 40m, accounting for 87.10% , the MWI was 395.32μg/L. The ICDW in deep phreatic well was higher than that in shallow well (u=2099, P<0.001). There was no correlation between well depth and ICDW in shallow wells (P>0.05). But there was a positive correlation between well depth and ICDW in deep phreatic wells (rs=0.414, P<0.001).Iodine excess areas ranged from northeast to southwest, and the tendency of the ICDW was heightening from west to east, from north to south in the central and east area of Cangzhou. Most iodine excess areas were connected with others. The survey scope was involved in two geomorphic units. They were Yellow River–Zhangwei River alluvial plain and alluvial and marine accumulating littoral plain. 109 water samples were collected in Yellow River–Zhangwei River alluvial plain, and the MWI was 274.33μg/L, accounting for 34.60%; 206 water samples were collected in alluvial and marine accumulating littoral plain, and the MWI was 447.40μg/L, accounting for 65.40%. The ICDW in alluvial and marine accumulating littoral plain was higher than that in Yellow River–Zhangwei River alluvial plain (u=6355, P<0.001).The survey scope were divided to two parts by different sedimental environments in geologic strata with the depth between 100m and 400m based on unclear marine transgression in Pleistocene of Quaternary period in Cangzhou. They were sediment area of sea and continental alternation and continental sediment area. 111 water samples with the well depth between 100m and 400m were in continental sediment area; 61 samples were in sediment area of sea and continental alternation. The ICDW in sediment area of sea and continental alternation was higher than that in continental sediment area (u=1173.5, P<0.001).207 cases of I°goiter and 15 cases of II°goiter were diagnosed among 2952 children aged 8~10 years in 14 towns and the goiter rate was 7.19%, between 3.45% and 14.63%. 12 out of 14 towns were identified as iodine excess areas in line with national criterion, accounting for 85.71% of the total. There was a positive correlation between the goiter rate of children and water iodine (P<0.05). The median of urine iodine was 258.01μg/L in 1494 urine samples, between 104.24μg/L and 489.06μg/L. There were positive correlations between urine iodine and the goiter rate of children and between urine iodine and water iodine (P<0.05).Conclusions: 1.Most drinking water using by inhabitants was deep phreatic well water in the central and east area of Cangzhou. There was a positive correlation between well depth and ICDW in deep phreatic wells; there was no correlation in shallow wells.2. The central and east area of Cangzhou included two geomorphic units. They were Yellow River–Zhangwei river alluvial plain and alluvial and marine accumulating littoral plain. The ICDW in the latter was higher than that in the former.3. High iodine water may be related to marine transgression in Quaternary period in geologic layer.4. With the concentration of water iodine increasing, the concentration of urine iodine and the goiter rate of children both increased in iodine excess areas in the central and east area of Cangzhou.The finding suggests that intervention measures should be taken to reduce the intake of iodine on the basis of the distribution of water iodine and the goiter prevalent condition. The purpose is to lower the prevalence rate of goiter.
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