2009 - Effects of fluoride in water on excess iodine

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2009 - Effects of fluoride in water on excess iodine

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李筱翠, 申红梅, 刘丽香, and 韩贺鹏. "饮水氟含量对高碘危害的影响研究." 中国地方病防治杂志 24, no. 5 (2009): 348-349.
http://www.cqvip.com/qk/94093x/200905/32046867.html
Study on the effect of drinking water fluoride levels on the hazard caused by excessive iodine

目的了解饮水氟含量对高碘危害是否有影响。方法应用全国高水碘地区调查和全国饮水型氟中毒病区水氟筛查结果,进行数据分析。结果当饮水氟含量〉1.0 mg/L时,高碘地区和高碘病区的8~10岁儿童甲肿率均随着饮水氟含量而增加,饮水氟含量在1~2 mg/L之间时,儿童甲肿率最低。在高碘地区,当饮水氟含量〉1.0 mg/L时,8~10岁儿童尿碘中位数有随着水氟值增加而减少的趋势,而在高碘病区,儿童尿碘中位数呈现出无规律的变化。结论高氟可以加强高碘危害的程度,二者具有协同作用,而且氟的水平也有最适范围,并非越低越好。饮水氟含量是否对尿碘水平存在影响还需进一步研究。

Objective: To find out whether the fluorine content in drinking water has any effect on the hazard of high iodine.

Methods: The results of the national survey of areas with high water iodine and the national water fluoride screening in drinking water fluorosis areas were used for data analysis.

Results: When the fluorine content in drinking water was more than 1.0 mg/L, the goiter rate of children aged 8-10 in high-iodine areas and high-iodine endemic areas increased with the fluorine content in drinking water, and the fluorine content in drinking water was between 1 and 2 mg/L. , the rate of goiter in children was the lowest. In areas with high iodine content, when the fluorine content of drinking water is > 1.0 mg/L, the median urinary iodine of children aged 8-10 tends to decrease with the increase of water fluorine value, while in high iodine disease areas, the median urinary iodine of children show irregular changes.

Conclusion: High fluorine can strengthen the harmful degree of high iodine, the two have a synergistic effect, and the level of fluorine also has an optimum range, not the lower the better. Whether the fluorine content of drinking water has an effect on the urinary iodine level needs further study.

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Re: 2009 - Effects of fluoride in water on excess iodine

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Translation:

Our country has a wide variety of endemic diseases, with a broad distribution. Many regions simultaneously experience multiple endemic diseases, posing a serious threat to the health of the local population. In China, there are 28 provinces with endemic fluorosis (referred to as "fluorosis"), and 11 provinces with areas of endemic goiter due to high iodine levels. In many areas, both of these endemic diseases coexist.

From 2005 to 2006, a nationwide survey was conducted in high-iodine areas to assess the distribution of iodine in water and to conduct a sampling survey on endemic goiter. From 2005 to 2007, a screening of fluoride levels in water was carried out in areas with endemic fluorosis nationwide, providing a basic understanding of the distribution of fluoride in water in these areas. To understand whether the fluoride content in drinking water affects the harm of high iodine, we conducted relevant analyses.

Data and Methods

1.1 General Information

For the investigation of high-iodine areas nationwide, data from high-iodine villages in nine provinces, including Anhui, Beijing, Hebei, Henan, Jiangsu, Inner Mongolia, Shandong, Shanxi, and Tianjin, were collected. Additionally, fluoride data from water samples in these provinces corresponding to areas with endemic fluorosis were included in the nationwide screening for fluoride levels in drinking water.

1.2 Statistical Analysis

Statistical analysis and data processing were conducted using SPSS 13.0 statistical software. Excel software was utilized for graphing and some data processing.

Results

2.1 The Influence of Drinking Water Fluoride Content on Goiter Rate in Children Aged 8-10

According to the classification standards for areas with endemic fluorosis (GB17018-1997), the fluoride content in drinking water was categorized into four levels. When the fluoride content in drinking water exceeded 1.0 mg/L, with a certain level of water iodine, the goiter rate in children increased with the increase in drinking water fluoride content. The lowest goiter rate in children was observed when the fluoride content in drinking water was between 1 and 2 mg/L. Refer to Table I and Figure 1.

2.2 The Influence of Drinking Water Fluoride Content on Urinary Iodine Levels in Children Aged 8-10

In high-iodine areas, the median urinary iodine levels in children aged 8-10 showed a decreasing trend with increasing fluoride levels in drinking water when the fluoride content exceeded 1.0 mg/L. However, in areas with endemic goiter due to high iodine levels, the median urinary iodine levels in children aged 8-10 exhibited irregular changes, indicating that further research is needed to determine whether drinking water fluoride content affects urinary iodine levels. Refer to Table 2 and Figure 2.

Discussion

Excessive or insufficient levels of fluoride and iodine elements can harm the body. In nature, iodine and fluoride often coexist, and there are some reports on the combined effects of iodine and fluoride, but the underlying mechanisms remain unclear. Studies on the effects of fluoride on the thyroid gland suggest that high fluoride levels are harmful to the thyroid. The degree of damage may vary due to factors such as fluoride intake dosage, duration of exposure, and individual and environmental conditions.

The main mechanisms by which fluoride affects the thyroid gland include:

Competition between fluoride and iodine, which inhibits the thyroid's uptake of iodine.

Inhibition of thyroid peroxidase activity by fluoride, which hampers the synthesis of thyroid hormones.

However, the precise interactions and effects of fluoride and iodine on thyroid function require further investigation.

It is important to note that the impact of fluoride on iodine levels in the body remains inconclusive, as observed in our study where urinary iodine levels in children showed irregular changes in areas with endemic goiter due to high iodine levels. This suggests that more research is needed to fully understand the relationship between fluoride intake and urinary iodine levels.

In conclusion, considering the potential hazards of both excessive fluoride and iodine intake, it is crucial to carefully monitor and manage the levels of these elements in drinking water to safeguard public health. Further research is warranted to elucidate the complex interactions between fluoride and iodine and their effects on thyroid function.

Thyroglobulin molecules are decomposed into thyroxine and triiodothyronine by the activity of proteases, thereby inhibiting the iodination of tyrosine residues and the coupling of iodinated tyrosine residues, leading to a decrease in serum T3 and T4 levels. Additionally, fluoride controls thyroid secretion by affecting the feedback mechanism regulated by the hypothalamus and anterior pituitary, and it also disrupts cellular function in thyroid tissue.

Thyroid enlargement is often prevalent in areas with endemic fluorosis. Hong Fugui and Yang Yingkui reported in Qingyun County, Shandong Province, and the Yellow River Delta region, respectively, that due to the dual hazards of high iodine and high fluoride, the rates of thyroid disease, enlargement, and dental fluorosis in residents were higher than those in the normal control group. When the fluoride content in drinking water exceeded 1.0 mg/L, the prevalence of childhood goiter increased with the increase in fluoride content in both high-iodine and endemic goiter areas, indicating a synergistic effect between high fluoride and high iodine. However, when the fluoride content in drinking water was between 1 and 2 mg/L, the prevalence of childhood goiter was the lowest, suggesting that there is an optimal range for fluoride levels, and lower is not necessarily better.

The changes in median urinary iodine levels in children aged 8-10 varied greatly depending on the fluoride content in drinking water. In areas with high iodine levels, there was a tendency for the median urinary iodine levels in children to decrease with increasing fluoride concentrations above 1.0 mg/L. This negative correlation might be due to both iodine and fluoride being halogen elements, where an increase in fluoride promotes the excretion of iodine. However, in areas with endemic goiter due to high iodine levels, this negative correlation did not appear, and the median urinary iodine levels in children exhibited irregular changes, indicating that further research is needed to determine whether fluoride levels in drinking water affect urinary iodine levels.

Due to the data used in this study not being specifically designed for research on the interaction between iodine and fluoride, and the on-site investigation being influenced by various factors, the analysis results of this study have certain limitations and are only provided for reference in studying the combined effects of iodine and fluoride.

References:

Yang Hongxiang, Liu Jicai, Zhang Zhiguang. Research on eliminating the dual hazards of high iodine and high fluoride water sources in Binzhou area [J]. Chinese Journal of Endemic Diseases Prevention and Control, 2002, (17)2: 98-100.

Guo Xiujuan, Shan Zhongyang, Teng Weiping. Experimental study on the influence of excessive fluoride and iodine on thyroid function and morphology [J]. Chinese Journal of Internal Medicine, 2006, (45)10: 846-847.

Xu Xiaolu, Zhang Zigui, Shen Xiuying. Effects of combined iodine and fluoride exposure on liver and kidney antioxidant capacity in mice [J]. Chinese Journal of Endemic Diseases, 2003, 22(i): 19-21.

Zhang Zigui, Zhong Xiuying, Xu Xiaolu. Effects of combined iodine and fluoride on red blood cell membrane phospholipids and fatty acids in rats [J]. Chinese Journal of Public Health, 2005, 21(2): 157-158.

China Center for Disease Control and Prevention, Endemic Disease Control Center. Endemic diseases [M]. Harbin: Heilongjiang People's Publishing House, 1999, 149.

Hong Fugui, Yang Dong, Xu Xia, et al. Prevalence of endemic goiter and fluorosis in the Yellow River Delta region due to high iodine and high fluoride in water sources [J]. Occupation and Health, 2001, 17(12): 89-90.

Yang Yingkui, Wang Xiuhong, Guo Xiaowei, et al. Study on the effects of high iodine and high fluoride on children's intelligence and iodine and fluoride metabolism [J]. Chinese Journal of Epidemiology, 1994, 15(5): 296-298.

(Received on: April 30, 2009)
(Editor: Liu Jianxin)
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