In response to “Cite Your Sources” which appeared in the Aug. 1-7 issue of North Country This Week: The trusted Cochrane group of researchers could not find any quality evidence to prove fluoridation changes the “existing differences in tooth decay across socioeconomic groups.” Neither could they find valid evidence that fluoride reduces adults’ cavity rates nor that fluoridation cessation increases tooth decay. Fluoridation may reduce cavities in children (2 primary teeth or 1 permanent tooth). But Cochrane cautions these studies have “high risk of bias” and were mostly done before preventive measures were widespread, e.g. fluoridated toothpaste and sealants. There is clear evidence that small amounts of fluoride, at or near levels added to U.S. water supplies, present potential risks to the thyroid gland, according to the 2006 National Research Council's (NRC) first-ever published review of the fluoride/thyroid literature. Fluoride impairs thyroid hormones at lower water concentrations than dentists claim is safe, according to “Impact of Drinking Water Fluoride on Human Thyroid Hormones: A Case Control Study,” published in Scientific Reports (Feb 2018).