Fluoride toxicity
[5] Although it is helpful topically for dental health in low dosage, chronic ingestion of fluoride in large amounts interferes with bone formation.
[8] In India an estimated 60 million people have been poisoned by well water contaminated by excessive fluoride, which is dissolved from the granite rocks.
[11] Other sources include glass-etching or chrome-cleaning agents like ammonium bifluoride or hydrofluoric acid,[12][13] industrial exposure to fluxes used to promote the flow of a molten metal on a solid surface, volcanic ejecta (for example, in cattle grazing after an 1845–1846 eruption of Hekla and the 1783–1784 flood basalt eruption of Laki), and metal cleaners.
Malfunction of water fluoridation equipment has happened several times, including a notable incident in Alaska.
Of this, about 10 percent, approximately 300 million people, obtains water from groundwater resources that are heavily contaminated with arsenic or fluoride.
[20] In 2024, a U.S. government study released by HHS found higher levels of fluoride exposure, such as drinking water containing more than 1.5 mg/L (which is the recommended safe limit set by the WHO), are associated with lower IQ in children.
[24]: 292 The kidney injury is characterised by failure to concentrate urine, leading to polyuria, and subsequent dehydration with hypernatremia and hyperosmolarity.
Inorganic fluoride inhibits adenylate cyclase activity required for antidiuretic hormone effect on the distal convoluted tubule of the kidney.
Fluoride also stimulates intrarenal vasodilation, leading to increased medullary blood flow, which interferes with the counter current mechanism in the kidney required for concentration of urine.
[24]: 266 Testing on mice shows that the medication gamma-Aminobutyric acid (GABA) can be used to treat fluoride toxicity of the thyroid and return normal function.
Urine tests have been used to ascertain rates of excretion in order to set upper limits in exposure to fluoride compounds and associated detrimental health effects.
[36] Ingested fluoride initially acts locally on the intestinal mucosa, where it forms hydrofluoric acid in the stomach.
