Fluoride poisoning is occurring due to contaminated water supplies, coal-burning pollution, and tea consumption (phosphate fertilizer contamination)."According to the survey, endemic fluorosis in China is distributed in more than 1,300 counties, and the population exposed to high fluoride environment is about 260 million people. It is known as the largest endemic fluorosis area in the world." (Zhu et al., 2017)
China also has a huge iodine problem.
Not only is there still iodine deficiency, but excessive iodine intake is also occurring now, due to contaminated water supplies, coal-burning pollution, and iodized salt consumption.
Prior to 1970, China was an iodine-deficient country, with 370 million people living in iodine-deficient areas. (There were no known reports of iodine excess prior to 1965).
In 1996, a mandatory Universal Iodized Salt program was introduced nationwide.
Unfortunately, this caused an excessive iodine intake for millions of people who were living in areas with elevated iodine levels in water or air.
To combat the ever-increasing iodine intake, national standards for iodized salt were revised and lowered in 2002 (Sun et al., 2014).
However, the revised levels proved still too high, and in 2013, standards were lowered again. In addition, a new policy was implemented allowing provincial governments to set their own local iodine concentration in salt to account for iodine exposure from other sources (Lin et al., 2021).
At present, the WHO still considers China a country with more-than-adequate iodine intake.
THE PROBLEM (just one of many...)
Among women of childbearing age, subclinical hypothyroidism from either iodine deficiency or excessive iodine, and positivity for thyroid autoantibodies, are now prevalent (Li et al., 2021).
All thyroid conditions may be exacerbated by fluoride. Fluoride may act in a synergistic or antagonistic way with iodine - depending on dose, timing, and duration.
Assessment of fluoride intake must be the first step in rectifying any iodine problem.
Maternal subclinical hypothyroidism causes high TSH in male newborns/delayed dental development
Li Y, Shan Z, Teng W; Thyroid Disorders, Iodine Status and Diabetes Epidemiological Survey Group - "The Iodine Status and Prevalence of Thyroid Disorders Among Women of Childbearing Age in China: National Cross-sectional Study" Endocr Pract 27(10):1028-1033 (2021)
Lin Y, Chen D, Wu J, Chen Z - "Iodine status five years after the adjustment of universal salt iodization: a cross-sectional study in Fujian Province, China" Nutr J 20(1):17 (2021)
https://www.ncbi.nlm.nih.gov/labs/pmc/a ... MC7903767/
Liu H, Li J, Cao H, Xie X, Wang Y - "Prediction modeling of geogenic iodine contaminated groundwater throughout China" J Environ Manage 303:114249 (2022)
Shi X, Han C, Li C, Mao J, Wang W, Xie X, Li C, Xu B, Meng T, Du J, Zhang S, Gao Z, Zhang X, Fan C, Shan Z, Teng W - "Optimal and safe upper limits of iodine intake for early pregnancy in iodine-sufficient regions: a cross-sectional study of 7190 pregnant women in China" J Clin Endocrinol Metab 100(4):1630-8 (2015)
Sun X, Shan Z, Teng W - "Effects of increased iodine intake on thyroid disorders" Endocrinol Metab (Seoul) 29(3):240-7 (2014)
https://www.ncbi.nlm.nih.gov/labs/pmc/a ... MC4192807/
Zhu Wenjing, Zhang Zigui, Shen Xiuying, Xu Xiaohong, Zhang Jing - "The pathogenesis of fluorosis and the anti-fluoride effect of selenium" Chinese Journal of Endemic Diseases 6 (2009) [Institute of Ecology, Zhejiang Normal University, Jinhua 321004, Department of Bioengineering , Zhejiang University of Science and Technology]