Water supplies fluoridation

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 ... 

Fluoride therapy and fluoridation of drinking water has played a significant role in deccreasing the dental caries. The incidence of dental caries can be significantly decreased by adding fluorides into the drinking water supply. Fluorides prevent decalcification of the structure of tooth by inhibiting bacterial enzymes which produce lactic acid. Fluorides also increase the tooth resistance to acid decalcification. 

The toxic nature of fluoride ion, F, is not confined to its presence in HF. It is toxic in soluble fluoride salts, such as NaF. At relatively low levels, such as about 1 ppm, used in some drinking water supplies, fluoride prevents tooth decay. At excessive levels, fluoride causes fluorosis, a condition characterized by bone abnormalities and mottled, soft teeth. Livestock are especially susceptible to poisoning from fluoride fallout on grazing land as a result of industrial pollution. In severe cases, the animals become lame and even die. 

In areas where there is no fluoridation of the community water supply, fluoride may be added to school water. This is not a substitute for community water fluoridation because fluoride intake from birth is important. 

One of the best known uses of fluorine is in the production of fluorides, used as additives in toothpastes and municipal water supplies. Fluorides are effective in preventing tooth decay and have been widely used in the United States for this purpose since the 1950s. 

Because fluoride is so effective against tooth decay, many states have established school fluoridation programs in which schools with independent water supplies fluoridate their water through the use of special equipment. In addition, schools in some areas of the country have adopted programs that provide fluoride tablets or a mouth rinse to children in the schools. The procedure takes only a few minutes each day and is supervised by someone trained to administer the supplement, usually the teacher. 

Fluoridation of water supplies—Fluoridation of water supplies to bring the concentration of fluoride to 1 ppm (1 part of fluorine to a million parts of water) has prov to be a safe, economical, and efficient way to reduce tooth decay a highly important public health measure in areas where natural water supplies do not contain this amount. Extensive medical and public health studies have clearly demonstrated the safety and nutritional advantages that result from fluoridation of water supplies. In communities in which fluoridation has been introduced, the incidence of tooth decay in children has been decreased by 50% or more. 

The presence of fluorine as a soluble fluoride in drinking water to the extent of 2 ppm may cause mottled enamel in teeth, when used by children acquiring permanent teeth in smaller amounts, however, fluorides are added to water supplies to prevent dental cavities. 

A city s water supply is fluoridated by adding NaF. The desired concentration of F is 1.6 ppm. How many milligrams of NaF should be added per gallon of treated water if the water supply already is 0.2 ppm in F ... 

The enrichment program followed in the United States is (/) the enrichment of flour, bread, and degerminated and white rice using thiamin [59-43-8] C 2H y N O S, riboflavin [83-88-5] C2yH2QN4Na02P, niacin [59-67-6] CgH N02, and iron [7439-89-6]-, (2) the retention or restoration of thiamin, riboflavin, niacin, and iron in processed food cereals (J) the addition of vitamin D [67-97-0] to milk, fluid skimmed milk, and nonfat dry milk (4) the addition of vitamin A [68-26-8], C2qH2qO, to margarine, fluid skimmed milk, and nonfat dry milk (5) the addition of iodine [7553-56-2] to table salt and (6) the addition of fluoride [16984-48-8] to areas in which the water supply has a low fluoride content (74). 

Eluoride added to a compatible dentifrice base at a level of 1000 ppm has been clinically proven to reduce the incidence of dental caries by about 25% on average, even in areas where the water supply is fluoridated (4). Elevation to 1500 ppm increases the protection. Sources of fluoride approved for use in dentifrices are sodium fluoride [7681-49-4] (0.22%), sodium monofluorophosphate (0.76%), and stannous fluoride [7783-47-3] (0.41%). The Eood and Dmg Administration regulates fluoridated dentifrices as dmgs and has estabUshed parameters for safe and effective products. CompatibiUty of the fluoride with the abrasive is an important requirement. 

Specific ion electrodes, similar in design to the glass electrode, have been developed to analyze for a variety of cations and anions. One of the first to be used extensively was a fluoride ion electrode that is sensitive to F- at concentrations as low as 0.1 part per million and hence is ideal for monitoring fluoridated water supplies. An electrode that is specific for Cl- ions is used to diagnose cystic fibrosis. Attached directly to the skin, it detects the abnormally high concentrations of sodium chloride in sweat that are a characteristic symptom of this disorder. Diagnoses that used to require an hour or more can now be carried out in a few minutes as a result, large numbers of children can be screened rapidly and routinely. 

The addition of fluoride ions to domestic water supplies (in the form of NaF) is now widespread and has resulted in a dramatic decrease in dental cavities. Fluoridated toothpastes, containing either tin(II) fluoride or sodium monofluorophos-phate (MFP, Na2FP03), are also recommended to strengthen tooth enamel. 

The use of fluoridated products, as well as fluoridation of domestic water supplies, has been one of the most successful approaches ever adopted to improve any aspect of public health. Continued use of such products, albeit under careful control and supervision by the dental profession, will remain important if the advances in oral health of the past 50 years are to be maintained in the future. 

So far, there have been no studies to confirm or refute the suggestion that water supplies contain polymeric species, and there have been only very few studies on the relevant equilibria which are involved in liberating free fluoride ions from the hexafluorosilicate additives [123]. What data there are, though, suggest that equilibrium will have been reached by the time the water reaches the consumer, even though it may not have been achieved when the water left the waterworks. 

A major benefit of water fluoridation to children is that it reduces disparities between socio-economic groups [133,134], Children in lower socio-economic groups tend to suffer more severely from dental caries, and though the reasons for this are not clear, the result has been confirmed in many parts of the world. Children in these groups therefore benefit enormously from fluoridation of the water supply and in areas where the water supply is fluoridated, the differences in dental caries experience between the social classes are much less than in non-fluoridated areas [135],... 

The use of fluoridated products, as well as fluoridation of domestic water supplies, has been one of the most successful approaches ever adopted to... 

F.A. Arnold Jr., H.T. Dean, J. Knutson, Effect of fluoridated public water supplies on dental caries incidence. Results of the seventh year of study at Grand Rapids, Muskegon, Mich., Public Health Rep. 68 (1953) 141-148. 

S.J. Jacobsen, W.M. O Fallon, L.J. Melton, Hip fracture incidence before and after the fluoridation of the public water supply, Rochester, Minnesota, Am. J. Public Health 83 (1993) 743-745. 

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. 

Fluoride in drinking water appears to be most effective in preventing dental caries if consumed before the eruption of the permanent teeth. The optimum concentration in drinking water supplies is 0.5-1 ppm. Topical application is most effective if done just as the teeth erupt. There is little further benefit to giving fluoride after the permanent teeth are fully formed. Excess fluoride in drinking water leads to mottling of the enamel proportionate to the concentration above 1 ppm. 

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