Fluoridation of water

Hileman, Fluoridation of Water A Special Report, C E News August 1, 26-42 (1988). See also B. Hileman, C E News February 25, 6-7 (1991). 

HBF4 (aq) and metal fluoroborates electroplating of metals, catalysts, fluxing in metal processing and surface treatment. HzSiF6 and its salts fluoridation of water, glass and ceramics manufacture, metal-ore treatment. 

A town adds 2.0 ppm of F ion to fluoridate its water supply (fluoridation of water reduces the incidence of dental caries). If the concentration of Ca2+ in the water is 3.5 X 10-4 M, will a precipitate of CaF2 form when the water is fluoridated ... 

Because of the low natural levels of fluoride in some water supplies and correspondingly high levels of dental caries, many authorities worldwide have permitted, or instigated, fluoridation of water supplies, although this has met some opposition, partly because of the potential health or dental effects including fluorosis. In order to prevent dental caries, fluoride is deliberately added to salt or milk in some countries. 

This much is certain there has been a dramatic decline in the incidence of dental caries since fluoridation of water supplies became widespread. This is doubly fortunate inasmuch as the safety of mercury amalgams, the... 

Fluoridation of water is often used to help reduce tooth decay. However, whereas levels of 1 ppm are commonly used, excessive fluoride levels (>2 ppm) can be a problem and need to be corrected. Analytical Technology Inc. manufactures a fluoride-sensitive ISE for this purpose [152]. 

The United States Public Health Service (USPHS) recommends the fluoridation of water as a means for preventing tooth decay. The recommended concentration is 1 mg F"/L. The presence of calcium ions in hard water can precipitate the added fluoride. What is the maximum molarity of calcium ions in hard water if the fluoride concentration is at the USPHS recommended level (Ksp for CaF2 = 4.0 X 10-11.)... 

Not all epidemiology is observational, and experimental studies have a role to play in evaluating the efficiency of an intervention program to prevent disease (e.g., fluoridation of water). An intervention study at one extreme may closely resemble a clinical trial with individuals randomly selected to receive some form of intervention (e.g., advice on reducing cholesterol levels). However, in some instances it may be a whole community that is selected to form the intervention group. The selection may or may not be random. 

Occupational exposure to inhaled fluoride dusts in cryolite workers during aluminum refining has resulted in severe bone abnormalities, but safety equipment now limits such exposure. No cases of skeletal fluorosis are attributed to use of controlled fluoridation of water supplies. However, skeletal fluorosis may occur in areas of the world where naturally occurring drinking water has high levels of fluoride, such as China and the Indian subcontinent. It is thought that exposure to fluoride intakes of 10 to 25mg/day for 10 years or more may result in skeletal fluorosis, but other nutritional factors may make these populations more susceptible. ... 

Yet another option, magnesium fluosilicate, used in Portland cements, or sodium fluosilicate used for the fluoridation of water supplies may be prepared for sale (Eqs. 10.16 and 10.17). 

Sodium fluoride is soluble. The sodium fluosilicate may be purified and marketed directly for purposes such as fluoridation of water supplies, or it may be used to prepare other salts, for example, synthetic cryolite (NasAlFg), valuable for aluminum smelting. 

Before fluoride was added to toothpastes (1950-1970), fluoridated water provided considerable protection from caries, but now that virtually all toothpastes are fluoridated, some have questioned the need for water fluoridation. Yet carefully controlled studies in Scotland, where public pressure to remove fluoride from the water supply has been extremely strong, indicate a marked increase in caries despite the continued use of fluoridated toothpaste (see Sect. 16.3.2). Fluoride toothpaste-mediated protection from caries is dependent on oral hygiene efficacy, whereas protection from caries by fluoride in the water supply appears independent of oral hygiene. Protection from caries by artificial fluoridation of water supplies and fluoridated toothpaste is independent and additive. 

In the USA, water fluoridation became widely available after 1955 and fluoridated toothpastes after 1975 and caries in adolescent children has decreased by 66%. The effects of fluoride on caries are topical from the surface to the interior. Water fluoridation ensures small amounts of fluoride throughout a tooth and fluoridated toothpaste enhances the fluoride concentration at the tooth surface. Protection from caries by artificial fluoridation of water supplies and fluoridated toothpaste is cumulative. Investigations as to how fluoridation protects from caries has identified three mechanisms of caries protection (1) inhibition of demineralization, (2) enhancement of remineralization, and (3) inhibition of bacterial enolase activity reducing lactate production from ingested carbohydrates. Fluoride has little effect on bacterial growth, and gives no direct protection from gingivitis, periodontitis, or osteoporosis... 

H2SiF6 and its salts fluoridation of water, glass and ceramics manufacture, metal-ore treatment. 

Questions of possible long-term toxicity remain. Since 1976 there has been a greater than 25% decrease in the incidence of ischemic heart disease in the United States.)) Increased exercise, a decreased severity of influenza epidemics, and fluoridation of water have been suggested as explanations. ... 

Calcium fluoride has a lower solubility than magnesium fluoride. Eventual production of Cap2 is important in the fluoridation of water. 

The reduction in dental caries as a result of fluoridation of water supplies and use of fluoride containing toothpastes is well known (Shell s and Duckworth 1994). This is clearly linked in part to the fact that the solubility product of fluorapatite is less than that of HAP (Moreno et al. 1977). For a partial replacement of OIT by F ions, the solubility product for Ca5(P04)3(0H)i.xFx is a minimum for x = 0.56 (Moreno et al. 1977). Chow and Banes (2001) and LeGeros (1991) discuss further the effects of F ions on the solubility, rate of dissolution and formation of apatites. Fluoride has also been used in attempts to rebuild bone lost as a result of osteoporosis (see Grynpas and Cheng 1988 and Baud et al. 1988 for references). Fluoride has effects on both bone mineral and cellular activity (Baylink et al. 1970, Banes and Reddi 1979). For example, F ions reduce the rate of dissolution of the mineral in acidic buffers (Grynpas and Cheng 1988). Other effects on the mineral will be mentioned later. 

Adding to drinking water is controversial. See Bette Hileman, Fluoridation of Water, Chem. 

Fluoride, on the other hand, is a trace element in animals and is normally present in blood serum at about the 5 X 10 mol dm level, but this can be considerably enhanced in patients anaesthetised with certain fluorocarbons and in the employees of certain important industries. The recent interest in fluoridation of water supplies has also focused attention on serum fluoride, but a dif-Hculty here is access to low fluoride serum for preparing standards. Hence, human serum from a normal young adult who has not drunk fluoridated water for 24 h is acceptable when the inorganic fluoride will be <5 XIO mol dm" [160] fluoride-free water may also be used with little loss of accuracy. 

Sodium fluoride (ca. 1903) n. NaF. A poisonous crystalline salt that is used in trace amounts in the fluoridation of water, in metallurgy, as a flux, and as a pesticide. 

The principal use for anhydrous HF is in the preparation of other inorganic fluorides for fluoridation of water, for use as fluxes and catalysts, and for the manufacture of glass and ceramics. 

A report by the Royal College of Physicians (1978) endorsed this view and recommended the fluoridation of water supplies in the United Kingdom where the fluoride level is appreciably below 1 mg per litre. 

When the beneficial effect of fluoride had been established, public health authorities proposed that fluoride compounds be added to water supplies in low-fluoride communities. Fluoridation started in the 1950s, and by 1965, nearly every medical and dental association in the United States had endorsed fluoridation of water supplies. In the past decade, however, that trend slowed as opposition to fluoridation grew. 

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