Originally, sodium fluoride was used to fluoridate water; hexafluorosilicic acid (H2SiF6) and its salt sodium hexafluorosilicate (Na2SiF6) are more commonly used additives, especially in the United States. The fluoridation of water is known to prevent tooth decay and is considered by the U.S. Centers for Disease Control and Prevention as "one of 10 great public health achievements of the 20th century", according to the US Centers for Disease Control and Prevention.
Fluoride, consumed excessively, as can be the case with fluoridated water, leads to its accumulation in the pineal gland, severely slowing down the production of melatonin, an essential hormone for optimal functioning of the body, including sleep regulation. It is also known to accumulate in other parts of the body, thereby rendering them unhealthy. Fluoride can also cause bone cancer in young men, thyroid malfunction, and arthritis in otherwise healthy humans, to name only a few.
Additionally, as reported in the Huffington Post, a recently-published Harvard University meta-analysis funded by the National Institutes of Health (NIH) has concluded that children who live in areas with highly fluoridated water have "significantly lower" IQ scores than those who live in low fluoride areas. Fluoride can also increase manganese absorption, compounding problems, since manganese in drinking water has also been linked to lower IQ in children. Studies have shown that fluoride toxicity can lead to a wide variety of health problems, including:
• Increased lead absorption
• Disrupts synthesis of collagen
• Hyperactivity and/or lethargy
• Muscle disorders
• Thyroid disease
• Bone fractures
• Lowered thyroid function
• Bone cancer (osteosarcoma)
• Inactivates 62 enzymes and inhibits more than 100
• Inhibited formation of antibodies
• Genetic damage and cell death
• Increased tumor and cancer rate