Physiologic Conditions Affect Toxicity of Ingested Industrial Fluoride
Journal of Environmental and Public Health
Volume 2013, Article 43940 http://dx.doi.org/10.1155/2013/43940
Hindawi Publishing Corporation
Special Issue: Water, Sanitation, and Public Health
1Department of Chemistry, University of California, San Diego, La Jolla, CA 92037
2Palomar Community College, San Marcos, CA 92069
Received 30 September 2012; Revised 13 March 2013; Accepted 3 April 2013
Academic Editor: Stephen Peckham
Copyright ©2013 Richard Sauerheber. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.
Abstract 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 toxicity 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.
Synthetic industrial fluoride compounds lack calcium and are listed toxic substances (Buck, 1, Gleason , Blakiston , The Merck Index ). Calcium fluoride CaF2 is found in natural minerals and is not labeled a toxic 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)  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. CDC ) but pure pristine fresh drinking water does not contain fluoride. Fluoride is not a normal constituent of the mammalian bloodstream (The Merck Manual for Health Care Professsionals ). It has no nutritive value (Lovering ) 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 (, Connett ).