How Does Fluorosilicic Acid Leach Lead?
And Why Does Fluorosilicic Acid Leach Lead So Much More Than Sodium Fluoride Does?
By Richard Sauerheber, Ph.D.
Working with James Robert Deal J.D.
December 31, 2012
Acknowledgments. Thanks to James Robert Deal for asking the questions which prodded me to write this article and for translating my article, as James says, from Scientific American terminology to Popular Science terminology.
Background: There is virtually no lead in Everett’s pristine water source, Spada Lake, just north of Sultan, in the heart of the “convergence zone”, where the winds which went north to get around Mount Olympus converge with the winds which went south to get around Mount Olympus, and which gets 140 inches of rainfall each year. In 1991 Everett’s city fathers were scammed into “fluoridating” Everett’s water, not knowing at the time that the so-called fluoride, commonly known as fluorosilicic acid, H2SiF6, contained small amounts of a score of poisonous elements and compounds, including lead. The fluorosilicic acid used to fluoridate can bring with it and add up to 1.1 ppb lead to drinking water, according to the National Sanitation Foundation.
As bad as 1.1 ppb lead is, there is enormously more lead at the tap. How can this be? This is so because there is lead in old service lines, old galvanized pipe, copper solder, and water taps, and fluorosilicic acid – and its break down compound orthosilicic acid – leach lead very well.
We hear a lot about paint as a source of lead poisoning, but almost nothing about lead in drinking water. It is a health district bind spot. This is not a trifling matter. Lead has been measured at up to 63 ppb at random taps in Everett and up to 1,600 ppb in Seattle school drinking fountains.
Coplan, Masters, Maas, and Sawan showed that that there is much more lead in tap water fluoridated with fluorosilicic acid than with sodium fluoride. However, they did not explain the mechanism by which fluorosilicic acid dissolves lead.
Industrial grade fluorosilicic acidcomponents are the most widely consumed non-nutritive chemical substance in the world. Because fluorosilicic acid is much cheaper than sodium fluoride, it is used in around 90% of water districts which fluoridate.
When diluted in water, fluorosilicic acid breaks down in drinking water into fluoride ion, hydrogen fluoride, and orthosilicic acid, H4SiO4, as the 2006 NRC study on fluoride stated. Little has been written in the fluoridation debate about orthosilicic acid, and that has been a mistake. Orthosilicic acid is classed as a weak acid and is often dismissed as relatively harmless. Unfortunately for our health, it is able to dissolve – slowly but surely – lead salts out of lead based pipes and fittings, especially brass.
In this article the author explores why orthosilicic acid dissolves lead and also proposes that orthosilicic acid passing over the teeth can directly slowly degrade calcium phosphate in teeth enamel.
The author challenges those who disagree to explain why and challenges biologists and chemists to run studies and experiments to confirm or refute these hypotheses.
Many countries followed the lead of the U.S. and initiated fluoridation. The following countries provide fluoridated water to the listed percentage of their respective populations: Singapore (100%), Hong Kong (100%), the Republic of Ireland (71%), United States (70%), Chile (70%), Australia (70%), Malaysia (66%), Israel (65%), Brazil (60%), New Zealand (50%), Canada (40%), South Korea (12%), Spain (10%), Great Britain (10%), Vietnam (4%), and Japan (1%). There is mandatory salt fluoridation in many other countries.
Many countries experimented with fluoridation but terminated it, usually on the grounds that it was the uncontrolled administration of a drug without informed consent.
The mass treatment of public fresh drinking water with industrial fluorosilicic acid to produce fluoride ion at 1.0 ppm also produces approximately 6 ppm sodium ion and .7 ppm orthosilicic acid. None of these is found in or belongs in fresh drinking water.
Fluoridation began with sodium fluoride in 1945, a granular solid produced by the aluminum and uranium industries. However, when fluoridation became a runaway presumed best seller in the 1950s, there was not enough sodium fluoride to go around. So industrial fluorosilicic acid, which comes in liquid form, and sodium silicofluoride, which comes as a granular solid, together referred to as silicofluorides, have largely supplanted sodium fluoride as the fluoridation material of choice.
Fluoridationists continue to convince water districts to begin fluoridating or not to stop fluoridating, however some 250 cities have halted the practice since 1990. They did so for a variety of reasons, including its expense, the irrefutable evidence that ingested fluoride does not decrease dental caries, and the fact that fluoridation is the imposition of a drug upon those who have not given their informed consent to be so treated.
Neither fluoride nor silicic acid are constituents of normal pristine human or mammalian blood, but rather are contaminant materials, so the decision to alter normal fresh drinking water into an industrial liquid, argued to be improved over normal water for human health, is a modern conception that has also significantly altered the composition of the bloodstream of entire populations. The present article addresses the ingestion of the orthosilicic acid component, the second most widely consumed industrial chemical after fluoride. Fluoride is not a mineral nutrient or a normal constituent of the bloodstream and thus of course is not listed in tables of ranges for blood constituents in any Clinical Chemistry, Nursing, or Veterinary text .
Unique Chemical Properties of Orthosilicic Acid.
It is essential to understand selected unusual chemical properties of orthosilicic acid. The first dissociation constant of this acid in water is very low, 2 x10-10, and it is therefore classified as a ‘very weak’ acid.
Aside: The dissociation constant is the ratio of the concentration of hydrogen ion protons times the silicate anion concentration divided by the concentration of the intact acid at a given temperature. Strong acids dissociate completely in water, and their dissociation constants are high as not to be accurately measurable. Strong acids with pH less than zero may be used for destructive purposes such as rapid oxidation and dissolution of metals that weak acids do much less readily or cannot do at all.
However, the terms strong and weak applied to acids are relative. In the stomach hydrochloric acid is a strong acid, which at dilute concentrations and a pH of 3, assists with digestion of food. The gastric mucosa lining of the stomach protects the rest of the body from this acidic environment. The intestines then neutralize HCL with weak base bicarbonate and a wide variety of ‘weak’ acid/base conjugate pairs in sufficient amounts so that body extracellular fluids are maintained at a pH of 7.4. The pH of the bloodstream is the most tightly regulated parameter in all physiology, and deviations of only ± 0.2 pH units causes unconsciousness. Through autonomic neural brain pathways, breathing rates are automatically adjusted to retain proper pH by adjustment of carbon dioxide through exhalation and carbonic acid/bicarbonate ratios in the blood.
Note that strong acids are rendered neutral by the addition of either equal amounts of strong bases or the addition of larger amounts of weak conjugate bases such as bicarbonate or biphosphate, turning the acid into a harmless conjugate base. Most important for this discussion, note that “weak” acids are nevertheless capable of important physiologic effects, that is by acting as acid catalysts or as reactants. Strong acids cause skin burns, but the weak acid hydrofluoric acid HF, one which does not dissociate well, causes even more serious burns and does deeper tissue damage. Because the HF molecule is neutral and very small, it can slip easily through the neutral fatty lipid layer and slowly penetrate deeply into the body. The point is that some weak acids can be extremely harmful.
Orthosilicic ‘weak’ acid has been long used in agriculture to break down solid calcium phosphate Ca3(PO4)2, thereby releasing soluble phosphate ion in soils even at neutral pH, for uptake by plant life. The reaction of silicic acid with calcium phosphate under neutral pH conditions is: H4SiO4 + Ca3(PO4)2 → HPO4-2 + 3Ca2+ + PO4-3+ H3SiO4–. This reaction occurs at a pH where any strong acid would have been neutralized. Orthosilicic acid is reluctant to dissociate and can break down calcium phosphate. This reaction is relevant not only to calcium phosphate in soil but also to calcium phosphate in teeth enamel. By means of orthosilicic acid, enamel is subject to slow and progressive degradation. This is so because the dissociation constant for biphosphate, HPO4-2, is only approximately 1 x 10-12, which is much lower than that for silicic acid, which again is 2 x10-10.
The pH of drinking waters in the U.S. typically range from 7 to 8.4 and remains so after treatment with fluorosilicic acid because the industrial acid is neutralized by the injection into water of alkalizing agents, usually caustic soda, NaOH, also known as Drano which is a strong base, or in the case of Everett and Seattle by sodium carbonate, Na2CO3, a weak base, also known as soda ash. While this neutralization works on fluorosilicic acid, it does not work on orthosilicic acid, and this is because of orthosilicic acid’s low dissociation constant. The pH would have to be raised to roughly 10 before the alkalinizing agent would neutralize the orthosilicic acid, but it would be impractical or impossible to raise the pH to 10, because doing this would create a new set of problems. Thus, the intact orthosilicic acid is fully retained in all treated drinking water, ready to dissolve lead in service lines, copper pipe solder, and plumbing faucets when the water gets to the home.
After assimilation, orthosilicic acid remains intact throughout the body except that silicate is known to incorporate into bone calcium phosphate and into collagen. Orthosilicic acid is eliminated by healthy kidneys, but a substantial amount is retained in kidney and other tissues.
As with any acid, orthosilicic is also capable of reacting with any metal having a reduction potential greater than hydrogen. Lead and aluminum are such metals, having reduction potentials greater than that for hydrogen, -0.13 and -1.66 volts, respectively.
Moreover, orthosilicic acid will leach aluminum from cookware and can contribute to significant uptake of aluminum ion in fluoride treated water. Although the Alzheimer’s Association no longer recognizes officially that aluminum may cause this disease, nevertheless silicate bound with aluminum is often found complexed to abnormal proteins in the brains of those afflicted with this disease, and even if orthosilicic acid binding of aluminum is not a primary cause in some cases of Alzheimer’s, it could certainly aggravate the condition and at minimum most certainly does not belong in brain tissue. For this reason alone, given the fact that Alzheimer’s incidence is rising precipitously in the U.S., the infusion of industrially produced orthosilicic acid intentionally into public water supplies should be considered a contraindication.
Silicic Acid Entry into Public Water Supplies.
Thus it happens that silicic acid, a primary breakdown chemical of fluorosilicic acid, makes its way into most fluoridated water. During neutralization of the acid with caustic soda, every 30 tons of fluoridation materials added produce about 10 tons of fluoride ion, 10 tons of sodium ion, and 10 tons of intact orthosilicic acid. When diluted the reaction is:
H2SiF6 + 4NaOH → 4F– + H4SiO4 + 4 Na+ + 2HF,
When fluoride ion is present at 0.8 ppm and water pH is 7.4, currently the situation in Everett and Seattle, there will be approximately 0.7 ppm free fluoride ion, around 0.6 ppm orthosilicic acid, and around 0.6 ppm sodium ion products. There will be trace amounts of hydrofluoric acid HF (and much more at stomach pH). Note that the principle of conservation of mass of course applies, where 1.9 mg of starting materials (the total mass of fluorosilicic and soda added) yield 1.8 mg of product materials per liter of water treated.
Turning to hydrofluoric acid, again at a water pH of 7.4, the HF level is only around 0.05 ppb (2 x 10-9 M); however, the intact orthosilicic acid concentration at 0.6 ppm (6 x 10-6 M) is over 3,000 times greater. Thus, orthosilicic acid is the chief weak acid generated in the process, rather than hydrofluoric acid. (The 0.05 ppb level of HF at pH 7.4 is calculated from the Henderson-Hasselbach equation, pH = pKa + log [F-]/[HF] where the pKa for HF dissociation is approximately 3.2. See Lide, editor, CRC Handbook of Chemistry and Physics, Chemical Rubber Company).
Further, water supplies frequently use aluminum sulfate as a flocculent to neutralize the negative charges on small dirt particles so they will clump together and can be filtered out. Aluminum forms complexes with fluoride in the acidic stomach. Likewise, silicofluoride complexes also form in the acidic stomach. A recent NMR study confirmed that such a complex which it suggested was SiF5–, forms at a pH around 3.
Lead ion in Drinking Water and Fluorosilicic Acid.
NSF admits that some lots of fluorosilicic acid produce after dilution up to 1.1 ppb lead in the product water. This level is after dilution 230,000 times to get the fluoride ion down to 1.0 ppm, and so this is the maximum part of total lead which comes from the fluoridation materials. Although below the EPA Maximum Contaminant Level of 10 ppb, 1.1 ppb lead is a significant amount of lead, but much more significant is the amount of lead leached by orthosilicic acid. Random taps in Everett have shown lead present at up to 63 ppb. Lead levels were measured at up to 1,600 ppb in Seattle school drinking fountains.
Coplan, Masters, Maas, and Sawan published that that there is much more lead in tap water fluoridated with fluorosilicic acid than with sodium fluoride, and that blood lead levels were higher. However, as stated previously, they did not explain the mechanism by which fluorosilicic acid dissolves lead and increases blood lead levels. Many ask how is it possible that fluorosilicic acid and sodium fluoride both yield the same amount of fluoride ion when dissolved in our drinking water, but fluorosilicic acid leaches so much more lead than does sodium fluoride.
The answer to this question is that it is not the fluoride which dissolves the lead well, but the orthosilicic acid (H4SiO4), the primary breakdown product left when fluorosilicic acid is diluted to the point where fluoride ion is at 1.0 ppm at neutral pH (see National Research Council, Report on Fluoride in Drinking Water, 2006 p. 53). This is the orthosilicic acid form that remains the intact acid even at a very alkaline pH of 10 because its dissociation constant Ka is only 2 x 10-10. Thus it is the intact orthosilicic acid, the predominant acid form present over the pH range 7 to 10 that is leaching lead or lead salts from pipes and plumbing fixtures where the following reactions can occur:
2H4SiO4 + Pb(s) → Pb2+ + H2 + 2H3SiO4–.
Indeed, it is well known that even the weak organic acids including intact acetic acid (CH3COOH) dissolve lead, despite the fact that the potent hydrofluoric acid, HF, is unable to dissolve lead well (see Merck Index, 9th edition, 1976, entry 5242, p. 5235). Orthosilicic acid is a ‘weak’ acid, remaining un-ionized at high pH, but this makes the acid able to react at alkaline pH with lead, or especially lead salts known to typically line old pipe surfaces such as lead hydroxide, lead phosphate or lead carbonate where, since the Ka2 for bicarbonate is 2 x 10-11 the following reaction occurs:
2H4SiO4 + PbCO3 → 2HCO3– + Pb2+ + 2H3SiO4–.
And the Ka for HOH is 10-14 where the following reaction occurs:
2H4SiO4 + Pb(OH)2 → Pb2+ + 2H3SiO4– + 2OH–.
Coplan and Masters found that brass fixtures containing lead are most susceptible to fluorosilicic acid treated water. They demonstrated that higher blood lead levels occur in children ingesting this treated water compared to water treated with either sodium fluoride or left untreated. It is not surprising that fluorosilicic acid treatment of water might cause increased lead levels in blood, while sodium fluoride treatment does not. Infusions of industrial fluorosilicic acid typically produce after dilution into municipal water supplies roughly equal amounts of fluoride ion, sodium ion and intact orthosilicic acid (NRC, 2006, p. 56). It is orthosilicic acid which is responsible for the increased lead leeching from plumbing.
The pH at which orthosilicic acid is neutralized (i.e. ionized) by caustic soda, so it would be unable to react with lead or its salts, is very high, above pH 10. Its pKa of 9.7 is the pH at which the acid would only be half-dissociated. The higher the acid content, the more corrosive the orthosilicic acid can be.
Fluorosilicic acid treated water dissolves lead from pipes more readily than does sodium fluoride treated water, even though the HF trace concentration is the same at a given fluoride level from either source. Therefore, as expected, it may be the un-ionized orthosilicic acid that is responsible for the dissolved lead from pipes exposed to this acid in waters treated with fluorosilicic acid, but which is not present in water treated with sodium fluoride.
Silicic Acid May React with Calcium Phosphate in Enamel.
Intact acids readily dissolve weak acid salts, including enamel calcium phosphate, the extent determined by concentration and exposure time. The “weak” organic carbonic acid H2CO3 (Ka = 4.5 x 10-7) in soda pop eventually dissolves teeth enamel soaked in vitro in large volumes of carbonated beverages. The intact acid concentration of 0.8 ppm at pH 5.6, compared to the intact orthosilicic acid concentration of 0.6 ppm in drinking water at pH 7-8. The slow reaction with calcium phosphate is:
2H4SiO4 + Ca3(PO4)2 → 2HPO4-2 + 2H3SiO4– + 3Ca2+..
Although material safety data sheets on orthosilicic acid indicate it is fully assimilated and well-excreted by normal kidneys, lifelong orthosilicic acid from treated drinking water has not been evaluated, and dental effects have not been examined in controlled studies.
Orthosilicic acid was reported to be found in dental calculus by virtue of preventing calcium phosphate precipitation on gingival surfaces of teeth (S. Hidak, Archives of Oral Biology Volume 38, Issue 5, May 1993, Pages 405–413, http://www.sciencedirect.com/science/article/pii/0003996993902125).
Because of claims of benefit without adequate clinical trials testing for longer term side effects, orthosilicic acid tablets are sold for optional use in solid form for swallowing, under the assumption of absence of peripheral harm. These tablets would not affect teeth topically, but lifelong orthosilicic acid from industrial sources in drinking water however is completely contraindicated in any topical caries preventive or as an ingestible.
Silicic Acid/Fluoride are Non-Nutritive, Abnormal Materials in Blood.
It is proper to state that neither silicic acid nor fluoride ion are listed as constituents of normal human blood (Teitz, Clinical Chemistry, W.B. Saunders, 1976; the Merck Manual, any edition; Leahy, Foundations of Nursing Practice, W.B. Saunders, 1998; or equivalent Nursing or Clinical Chemistry text with tabulated listings for normal blood constituents). These substances at any concentration are contaminants in blood.
Silicic acid is widely argued in the dental industry to be “innocuous” and argued to be “metabolized away” after ingestion. This of course has not been established for lifelong consumption nor have controlled human clinical trials been conducted for effects on either brain function or teeth health.
The effects caused by the continuous lifelong consumption of orthosilicic acid in the human are not well understood. Silicon is found cross-linking collagen fibers and stimulates collagen synthesis in vitro, but this effect is not known with certainty to be either physiologic or pathologic. In chicks, evidence of bone damage was presented in one study presumed to be due to silicon lack, but no evidence of disease is known in humans due to a deficiency of silicon. There is no official minimum dietary requirement for silicon and no designation that it is a mineral nutrient, although the agent is marketed without FDA clinical trials and approval as an oral ingestible for the purpose of strengthening nails and as an anti-wrinkling agent. The anhydrous form of silicon, silica found in quartz and granite, is not assimilated by ingestion but when inhaled or injected causes the well-known condition silicosis of the lung and liver with associated fibrosis and hepatic carcinoma.
Neither the EPA, FDA, nor WHO have assigned either a minimum or maximum level for silicic acid in drinking water, and no agency has recognized a dietary need for it. As such, there is little likelihood that Federal regulations for silicic acid infusions into public water supplies will be developed anytime soon.Health Impacts of Silicic Acid.
Although a positive view has been presented for possible benefits of silicic acid consumption in man, nevertheless silicic acid at levels discussed here from water silicofluoridation leads to softer fingernails and changes in skin structure (see: Barel A, Calomme M, Timchenko A, De Paepe K, Demeester N, Rogiers V, Clarys P, Vanden Berghe D., Archives of Dermatolical Research 2005 Oct;297(4):147-53. Epub 2005 Oct 26) associated with artificial stimulation of collagen formation by fibroblasts that could be non-physiologic.Orthosilicic acid is sold as an anti-wrinkling oral agent and possible “vitamin” or “dietary supplement”, marketed as such under the name Biosil: http://www.amazon.com/Biosil-Orthosilicic-Acid-Veg-Caps/dp/B003WGCK70 even though this agent has no known purpose in human blood. So, treatment of water with fluorosilicic acid provides two substances, both argued by different promoters as being mineral “nutrients” or “supplements”, orthosilicic acid and fluoride, despite the fact that neither has been shown to serve any purposes in the human body.
That silicic acid can be a nutrient is not well-founded. It has long been known that lung silicosis is eventually a lethal condition in silica and granite workers and that hepatic and lung fibrosis and hepatic carcinomas are easily induced in mammals with silica at known high single doses, where 100% of rodents directly injected with this material, without inhalation, after one year develop these conditions, associated with acute fibrosis that the silica causes. The interpretation that “silicic acid improves skin by increasing collagen synthesis” fails to consider that the opposite interpretation may be more scientific, which is that collagen synthesized by silicon stimulation could be abnormal, and is formed as a defense mechanism in response to physical insult from silica. The excess collagen in silicosis of course is an abnormality (see: Williams AO, Knapton AD, Hepatic silicosis, cirrhosis, and liver tumors in mice and hamsters: studies of transforming growth factor beta expression, Hepatology, 1996 May;23(5):1268-75) (http://onlinelibrary.wiley.com/doi/10.1002/hep.510230548/pdf).
The International Agency for Research on Cancer (IARC) has concluded that crystalline silica in the form of quartz from occupational inhaled sources should be classified as carcinogenic to humans (Group 1), upgraded from its previous classification as probably carcinogenic to humans (Group 2A). This conclusion was drawn on the basis of a relatively large number of human population studies that together provide sufficient evidence in humans for the carcinogenicity of inhaled crystalline silica (Archives of Oral Biology, Volume 38, Issue 5, May 1993, Pages 405–413). Silicates under acidic conditions such as in the stomach are converted to the fully soluble form silicic acid which is fully assimilated. Oral ingestion of this acid is well tolerated in the human, but no acute toxicity data are available. In dogs, 250 mg/kg silicate is the minimum single lethal oral dose (see: http://ntp.niehs.nih.gov/ntp/htdocs/chem_background/exsumpdf/sodiummetasilicate.pdf).
Although silicic acid is fully assimilated and excreted by normal kidneys, evidence that silicic acid is not always well-excreted is plentiful. In carefully controlled experiments, alligators treated with silicofluoridated public water developed silicosis of the liver after fluorosilicic infusions began in Kansas City (personal communication, Dr. Albert Burgstahler) (Toxic Effects of Silicofluoridated Water in Chinchillas, Caimans, Alligators, and Rats held in Captivity, Fluoride 41:83, 2008) that was absent in alligators in the facility living in water without silicofluoride.
At the University of California, Davis, researchers now recognize that silicosis induced bone deformations occur in CA horses and may be responsible for the high incidence of racehorse breakdowns in the State (http://www.vetmed.ucdavis.edu/vorl/research_programs/musculoskeletal_disease_injuries/index.cfm). These horses typically have abnormal lung and respiration involvement which is consistent with animal studies of silicosis that always involve both lung and hepatic tissue. The source of exposure for silicon are mostly from feeds but also in CA from water treated with industrial fluorosilicic acid.
Human silicosis has historically been associated with sandblasters and miners where exposure is through long term inhalation of silica, so most postmortem studies centered on lung tissue, but in 1996 a call for investigations into hepatic disorders that are expected to accompany lung silicosis in humans was made (A M Arens, B Barr, S M Puchalski, R Poppenga, R M Kulin, J Anderson, S M Stover, Osteoporosis associated with pulmonary silicosis in an equine bone fragility syndrome, Veterinary Pathology (2011), Volume: 48, Issue: 3, Pages: 593-615; www.ncbi.nlm.nih.gov).
People with kidney disease on dialysis would be expected to have silicic acid excretion difficulties.Although Material Safety Data Sheets on orthosilicic acid casually indicate that there may be no known adverse effects from ingestion, there are no human studies available for lifelong orthosilicic acid assimilation from treated drinking water or as an ingestible, particularly in the infirmed. Regardless of whether for most people silicic acid ingestion may be safe and tolerated, any putative minimum requirement for daily silicon in the diet is small, and foods such as grains already provide this ingredient. Treating water intentionally with the substance is unwarranted, and our present knowledge base does not justify intentional infusions.
The reaction of aluminum in cookware with water treated with sodium fluoride has been known since 1940. Since this is due to reaction of aluminum metal with trace hydrofluoric acid (HF), the dissolution is more significant when cooking under acidic conditions such as cooking tomatoes where all the fluoride ion is protonated to HF. However, the present article here indicates that fluoridation with fluorosilicic acid treated water is expected to produce even greater amounts of dissolved aluminum ion from aluminum cookware because there is far more silicic acid in drinking water at neutral pH than there is HF.
Finally, it is ironic that the fluoride level that bathes teeth topically in saliva from that ingested from treated water, only 0.02 ppm, is argued to be an effective caries preventive, when in fact toothpaste fluoride is 75,000 times more concentrated than this. The CDC old adage, that fluoridation is a public health achievement at 1 ppm because only a ‘small’ amount of ugly dental fluorosis abnormal enamel hypoplasia was thought would occur, is now known to be in error. 41% of U.S. 12-15 year olds have significant enamel fluorosis in the U.S. as of 2004. Meanwhile, millions of Americans are consuming industrial fluorides believing that ingesting fluoride ion can reduce dental caries without ill effect, but the CDC reported that systemic fluoride is unable to affect caries (CDC, Morbidity and Mortality Weekly Report, Aug, 2001), and instead is responsible for enamel fluorosis, and saliva fluoride at only 0.02 ppm (National Research Council, Report on Fluoride in Drinking Water, 2006) is also unable to affect teeth topically.
Medical treatments always must balance between adverse side effects and potential benefit. The long and admirable mission of the CDC is to protect the health of all Americans, and in some cases this simply means leaving citizens alone. We now have exceptional methods of reducing decay, in addition to brushing, flossing and good dietary habits, including dilute antibiotic trays fitted to teeth that eliminate caries-causing bacteria in otherwise difficult cases. The infusion of any food or nutriment, as well as any contaminants, into public water supplies is forbidden by the U.S. Safe Drinking Water Act which prohibits any National requirement for any substance in water other than to sanitize the water and that the States can be no less restrictive. Vitamin C for example is an essential substance to prevent illness, scurvy, and yet it is illegal to inject vitamin C into public water supplies to treat people. Likewise, it is illegal to infuse into public water supplies any silicic acid (which is not officially a mineral nutrient, vitamin or food), either with direct intent, or intentionally but indirectly as discussed here as a byproduct from diluted industrial fluorosilicic acid.