Toxicity of fluoride

The toxicity of fluoride depends on the type of compound ingested. Generally, the more soluble salts of inorganic fluorides, such as sodium fluoride, are more toxic that those that are either weakly soluble or insoluble [42]. Readily soluble fluoride compounds release free fluoride ions on dissolution, while fluoride compounds that are insoluble or poorly soluble do not [57,58]. Fluoride from the former... 

K. Akinaw/a, Re-examination of acute toxicity of fluoride. Fluoride 30 (1997) 89-101. G.M. Whitford, Fluoride in dental products Safety considerations, J. Dent. Res. 66(1987) 1056-1060. 

The dark side of hydrofluoric acid is its toxicity and corrosiveness. Aqueous and anhydrous HF readily penetrate the skin, and, because of its locally anesthetizing effect, even in very small quantities can cause deep lesions and necroses [4, 5]. An additional health hazard is the systemic toxicity of fluoride ions, which interfere strongly with calcium metabolism. Resorption of HF by skin contact (from a contact area exceeding 160 cm ), inhalation, or ingestion leads to hypocalcemia with very serious consequences, for example cardiac arrhythmia. 

K ion is a cofactor for the aldolase reaction. Pyruvic kinase from all known sources also requires univalent cations, in addition to a divalent cation. This enzyme needs K, ammonium, or Rb ions as a cofactor. Mg ions serve an important function in photosynthetic processes in tobacco as it is an essential constituent of chlorophyll a and chlorophyll b. Some heavy metal and nonmetal ions are toxic to tobacco and can serve as metabolic inhibitors. The toxicity of fluoride, for example, is explained in part on the basis of the formation of a magnesium-fluorphosphate complex that inhibits the eno-lase reaction in glycolysis. Other enzymes are inhibited by substrate analogs, sulfhydryl complexing agents, and metal chelating agents. 

B. Fluoride Appropriate concentrations of fluoride ion in drinking water (0.5-1 ppm) or as a dentifrice additive have a well-documented ability to reduce dental caries. Chronic exposure to the ion, especially in high concentrations, may increase new bone synthesis. It is not clear, however, whether this new bone is normal in strength. Clinical trials of fluoride in patients with osteoporosis have not demonstrated a reduction in fracmres. Acute toxicity of fluoride (usually caused by ingestion of rat poison) is manifested by gastrointestinal and neurologic symptoms. Chronic toxicity (fluorosis) includes ectopic bone formation and exostoses. 

Because of the corrosive effects and discomfort associated with inhalation of fluorine, chronic toxicity does not occur. Although the metaboHc fate of fluorine is not clear, it does not seem that much is converted to fluoride ion in the body (107). Therefore comparisons to effects of fluoride ion poisoning, known as fluorosis, are probably incorrect. 

The toxicity of these fluoroaluminates is mainly as inorganic fluorides. The ACGIH adopted (1992—1993) values for fluorides as F is TLV 2.5 mg/m. The oral toxicity in laboratory animal tests is reported to be LD q rat 2.15 mg/kg (41). Because of the fine nature of the products they can also be sources of chronic toxicity effects as dusts. 

Health and Safety Factors. Boron trifluoride is primarily a pulmonary irritant. The toxicity of the gas to humans has not been reported (58), but laboratory tests on animals gave results ranging from an increased pneumonitis to death. The TLV is 1 ppm (59,60). Inhalation toxicity studies in rats have shown that exposure to BF at 17 mg/m resulted in renal toxicity, whereas exposure at 6 mg/m did not result in a toxic response (61). Prolonged inhalation produced dental fluorosis (62). High concentrations bum the skin similarly to acids such as HBF and, if the skin is subject to prolonged exposure, the treatment should be the same as for fluoride exposure and hypocalcemia. No chronic effects have been observed in workers exposed to small quantities of the gas at frequent intervals over a period of years. 

Health and Safety Factors. The low solubiUty of calcium fluoride reduces the potential problem of fluoride-related toxicity. Water saturated with calcium fluoride has a fluoride concentration of 8.1 ppm as compared to the recommended water fluoridation level of 1 ppm fluoride ion. However, because the solubiUty of calcium fluoride ia stomach acid is higher, continued oral ingestion of calcium fluoride could produce symptoms of fluorosis. The adopted TWA limit for fluorides as F is 2.5 mg/m (68,69). 

Because PTFE resins decompose slowly, they may be heated to a high temperature. The toxicity of the pyrolysis products warrants care where exposure of personnel is likely to occur (120). Above 230°C decomposition rates become measurable (0.0001% per hour). Small amounts of toxic perfiuoroisobutylene have been isolated at 400°C and above free fluorine has never been found. Above 690°C the decomposition products bum but do not support combustion if the heat is removed. Combustion products consist primarily of carbon dioxide, carbon tetrafluoride, and small quantities of toxic and corrosive hydrogen fluoride. The PTFE resins are nonflammable and do not propagate flame. 

The Du Pont HaskeU Laboratory for Toxicology and Industrial Medicine has conducted a study to determine the acute inhalation toxicity of fumes evolved from Tefzel fluoropolymers when heated at elevated temperatures. Rats were exposed to decomposition products of Tefzel for 4 h at various temperatures. The approximate lethal temperature (ALT) for Tefzel resins was deterrnined to be 335—350°C. AH rats survived exposure to pyrolysis products from Tefzel heated to 300°C for this time period. At the ALT level, death was from pulmonary edema carbon monoxide poisoning was probably a contributing factor. Hydrolyzable fluoride was present in the pyrolysis products, with concentration dependent on temperature. 

PVDE is not hazardous under typical processing conditions. If the polymer is accidentaky exposed to temperatures exceeding 350°C, thermal decomposition occurs with evolution of toxic hydrogen fluoride (HE). 

Polymer Solvent. Sulfolane is a solvent for a variety of polymers, including polyacrylonitrile (PAN), poly(vinyhdene cyanide), poly(vinyl chloride) (PVC), poly(vinyl fluoride), and polysulfones (124—129). Sulfolane solutions of PAN, poly(vinyhdene cyanide), and PVC have been patented for fiber-spinning processes, in which the relatively low solution viscosity, good thermal stabiUty, and comparatively low solvent toxicity of sulfolane are advantageous. Powdered perfluorocarbon copolymers bearing sulfo or carboxy groups have been prepared by precipitation from sulfolane solution with toluene at temperatures below 300°C. Particle sizes of 0.5—100 p.m result. 

Other studies of the toxicity of stannous fluoride, sodium pentafluorostannite, sodium pentachlorostannite, sodium chlorostannate, stannous sulfide [1314-95-0] stannous and stannic oxides, stannous pyrophosphate [15578-26 ] stannous tartrate [815-85-0] and other inorganic tin compounds are reviewed in References (dh—12. The OSHA TLV standard for inorganic tin compounds is two milligrams of inorganic tin compounds as tin per cubic meter of air averaged over an eight-hour work shift (47). 

Polytetrafluoroethylene decomposition products thermal decomposition of the fluorocarbon chain in air leads to the formation of oxidized products containing carbon, fluorine and oxygen. Because these products decompose in part by hydrolysis in alkaline solution, they can be quantitatively determined in air as fluoride to provide an index of exposure. No TLV is recommended pending determination of the toxicity of the products, but air concentration should be minimal. (Trade names Algoflon, Fluon, Teflon, Tetran.)... 

Chemical Reactivity - Reactivity with Water Reacts vigorously to form toxic hydrogen fluoride (hydrofluoric acid) Reactivity with Common Materials When moisture is present, causes severe corrosion of metals (except steel) and glass. If confined and wet can cause explosion. May cause fire in contact with combustible material Stability During Transport Stable Neutralizing Agents for Acids and Caustics Flush with water, rinse with sodium bicarbonate or lime solution Polymerization Not pertinent Inhibitor of Polymerization Not pertinent. 

In order to achieve high yields, the reaction usually is conducted by application of high pressure. For laboratory use, the need for high-pressure equipment, together with the toxicity of carbon monoxide, makes that reaction less practicable. The scope of that reaction is limited to benzene, alkyl substituted and certain other electron-rich aromatic compounds. With mono-substituted benzenes, thepara-for-mylated product is formed preferentially. Super-acidic catalysts have been developed, for example generated from trifluoromethanesulfonic acid, hydrogen fluoride and boron trifluoride the application of elevated pressure is then not necessary. 

Toxicity. A 1% concn of the gas in air is lethal to rats in 1 hour, its effect being similar to C monoxide the LD50 in rats when injected intra-peritoneally is 8.2ml/kg (Ref 16). Earlier workers assumed that the toxicity of N trifluoride would be similar to H fluoride and that the latter would be formed by hydrolysis in body tissues (Ref 1). This has recently been shown to be erroneous, and that it is stable under physiological conds. The toxic effect is due to its ability to complex with the hemoglobin of the blood causing anoxia. This effect is reversible, and animals receiving a sublethal dose recover rapidly upon removal from contact with N trifluoride (Ref 14)... 

First, we investigated whether Sh I could be reduced under denaturing conditions, exposed to the hydrogen fluoride cleavage procedure we intended to use, then reoxidized and refolded successfully. The toxicity of the resulting polypeptide (50% yield) was the same as that of the untreated natural toxin. 

Leirskar, J. Helgeland, K. (1987). Mechanism of an in vitro toxicity of restorative materials pH, fluoride and zinc. International Endodontic Journal, 20, 246-7. 

The physiological effects of the fluoride ion were reviewed by McClure 74) in 1933. Lehmann 72) published an article on the toxicity of aromatic fluorine compounds in 1928. However, it has been impossible to investigate the toxicity of the organofluorine compounds as thoroughly as that of the organochlorine compounds. 

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