Physiologic Conditions Affect Toxicity of Ingested Industrial Fluoride

The effects of calcium ion and broad pH ranges on free fluoride ion aqueous concentrations were measured directly and computed theoretically. Solubility calculations indicate that blood fluoride concentrations that occur in lethal poisonings would decrease calcium below prevailing levels. Acute lethal poisoning and also many of the chronic effects of fluoride involve alterations in the chemical activity of calcium by the fluoride ion. Natural calcium fluoride with low solubility and toxicity from ingestion is distinct from fully soluble toxic industrial fluorides. The toxicity of fluoride is determined by environmental conditions and the positive cations present. At a pH typical of gastric juice, fluoride is largely protonated as hydrofluoric acid HF. Industrial fluoride ingested from treated water enters saliva at levels too low to affect dental caries. Blood levels during lifelong consumption can harm heart, bone, brain, and even developing teeth enamel. The widespread policy known as water fluoridation is discussed in light of these findings. 1. Introduction Synthetic industrial fluoride compounds lack calcium and are listed toxic substances (Buck [1], Gleason [2], Blakiston [3], The Merck Index [4]). Calcium fluoride is found in natural minerals and is not labeled a toxic compound because of the comparatively high lethal oral acute dose of the purified compound when tested in mammals (LD50 ~ 3,750？mg/kg). The fluoride compounds, sodium fluoride NaF and fluorosilicic acid H2SiF6, added into municipal water for human ingestion purposes are synthesized artificially by industrial reaction and have been used as rodenticides, insecticides, and pediculicides, with acute oral lethal doses in experimental animals comparable to arsenic and lead (LD50 ~ 125？mg/kg) (The Merck Index [4]) due to the fluoride at ~60–90？mg/kg. Waters in the U.S. can contain natural calcium fluoride along with other calcium and magnesium salts (U.S. Centers for Disease Control (CDC) [5]), but pure pristine fresh drinking water does not contain fluoride. Fluoride is not a normal constituent of the mammalian bloodstream (Merck manual for Health Care Professionals [6]). It has no nutritive value [7] or physiologic function but has been believed by some to be useful for teeth based on an initial correlation with natural calcium fluoride in drinking water [1, 8]. The chief ingredient in normal teeth enamel is hydroxyapatite that contains calcium phosphate, not fluoride. After nearly 7 decades of adding industrial fluoride compounds into public water supplies in the U.S. and other