This site makes the claim that the reason the FDA never tested fluoride for human consumption was because it was on the market prior to 1938, when the FDA was formed. This claim is pretty well referenced with a letter I will presume to be accurate, from the FDA:

Drugs on the market prior to enactment of the 1938 law were exempted, or "grandfathered", and manufacturers were not required to file an NDA. The premise was that all pre-1938 drugs were considered safe, and if the manufacturer did not change the product formulation or indication, then an NDA was not required.

The author of the site (not of the letter quoted) makes the additional claim, however, that fluoride was sold as rat poison prior to 1938.

I am willing to accept as granted that fluoride was sold as rat poison prior to 1938.

What I find a bit harder to believe is the jump to the author's conclusion that fluoride being sold as rat poison prior to 1938 is the reason it was grandfathered in under the (then) new FDA rules.

Was fluoride also sold as a medication intended for humans, that would have exempted it from the new rules, or is it true it was only considered a rat poison in 1938?


1 Answer 1


There are several false claims in the site quoted.

The arguments seem to be based on a "petition" to the FDA (filed as Docket 00P-1602) from then politician John V. Kelly.

The main thesis seems to consist of the following claims:

  1. Sodium Flouride was only used as rat poison, in bulk, prior to 1938.
  2. It was not considered as an anti-cavity treatment until the 1950s and 1960s.
  3. Any drugs sold before 1938 were grandfathered into the new FDA law.
  4. The FDA never approved it as safe for children's anti-cavity supplements.
  5. Therefore, Sodium Fluoride has never been shown as safe for ingestion for children's anti-cavity supplements, and was only approved because it was used as rat poison.

Several of these claims are untrue.

Prior Art in Patents

  • June 29, 1909: German patent 222,716 Verfahren zur Herstellung leicht resorbierbarer Fluorpräparate covered the use of "an easily absorbable fluoride preparation" by precipitating "calcium fluoride (using sodium fluoride plus a calcium salt) together with a protein like egg-white, albumin, casein, to which it becomes adsorbed on co-precipitation.)", based on experiments by Deninger in 1896.

  • Nov 28, 1911: German patent 281,148 Verfahren zur Herstellung leicht löslicher, haltbarer Desinfektionsmittel zur Bereitung von Mund- und Spülwasser unter Verwendung von Natriumfluorid und Natriumsiliciumfluorid, covered "a mouthwash and disinfectant made of sodium fluoride or sodium fluosilicate".

  • May 19, 1927: US Patent (US) 1,813,936 Mineral Food Composition and Process of Making Same, covered a calcium, magnesium and phosphate preparation as a food supplement, also containing Sodiom Fluoride.


So, the claim that Sodium Fluoride was only used as rat poison prior to 1938 is false.

Prior Art in Science

The 1952 book A Survey of the Literature of Dental Caries by the Food and Nutrition Board of the National Research Council shows that there was a lot of literature already existing by the beginning of the 1950s.

Cox write [in 1939]: "Our evidence that fluorine aids in the formation of caries-resistant teeth, linked with the findings of Armstrong (1938) and of Dean, Jay, Arnold, Mclure and Elvove (1939), shows that a very great reduction of the incidence of human caries can be obtained by supplying in food and water an optimum amount of fluorine during teeth formation.

Other scientists were looking at natural fluoride overdoses (Source: Fluoridation Facts from the ADA):

During the 1930s, Dr. H. Trendley Dean, a dental officer of the U.S. Public Health Service, and his associates conducted classic epidemiological studies on the geographic distribution and severity of fluorosis in the United States. These early studies were aimed at evaluating how high the fluoride levels in water could be before visible, severe dental fluorosis occurred. By 1936, Dean and his staff had made the critical discovery that fluoride levels of up to 1.0 part per million (ppm) in the drinking water did not cause the more severe forms of dental fluorosis. Dean additionally noted a correlation between fluoride levels in the water and reduced incidence of dental decay

Admittedly, this was looking at natural levels of fluoride, rather than supplements.

In 1874, though, Erhardt 'recommended fluorine for internal use "since it is fluroine which gives hardness and lasting quality to the enamel of teeth and so protects against caries"' He went on to discuss the (existing) fluorine pastilles available in England, and performed experiments with potassium fluoride as a supplement for a dog.

Alas, I haven't directly contradicted the claim that "Sodium fluoride supplements weren't tested as a decay preventative until the 1950's or 1960's", but certainly fluoride supplements, and experiments on the safety and effect of fluoride had started well before this time.

Prior Art in FDA Records

In 1936, the FDA asked a court to destroy 4,500 Sodium Fluoride tablets that had been shipped in 1935, claiming they "contained two-fifths grain of sodium fluoride each instead of one-half grain as represented on the label." (i.e. 25 mg not 32 mg).

There is no record here of what the tablets were to be used for, but it is clear that 32mg tablets isn't "in bulk form" or an appropriate form for use as rat poison.

Whether modern FDA records indicate this history of Sodium Fluoride is less clear. The original link quotes an unnamed FDA bureacrat saying:

We don't have information on the medical uses of fluoride before 1938.

and John V. Kelly claimed:

The FDA records show only that sodium fluoride in bulk form was available prior to 1938. The FDA has no record of use as tablets, drops or any therapeutic dosage form. The only pre-1938 use of sodium fluoride my office has been able to identify is as a rodenticide and insecticide

FDA Examination of Safety

It is not true that the FDA has simply ignored the ingestion of flourides since 1938.

For example in 1990, they examined a number of proposed changes in anti-cavity dentrifices (e.g. toothpaste). They rejected the idea of introducing lower fluoride versions and higher fluoride version, they tweaked what could be put on the labels, they noted that "an NDA was approved in 1986 for an extra-strength fluoride dentrifice" for over 2 year olds, and then recommended it be adjusted to over 6 year olds. They cite a number of submissions and scientific papers they used to make these determinations.

The point being: there is evidence that the FDA has not ignored fluorides for 70+ years; they are reviewing the new evidence as it comes in, and adjusting their recommendations and approvals as required.

  • 6
    One addendum: you often hear from the anti-fluoridationists that fluoride in drinking water has never been approved by the FDA, which is true but misleading, as drinking water quality in the US is the balliwick of the EPA, not the FDA. Aug 26, 2012 at 22:27
  • 3
    The EPA also doesn't "approve" or endorse water fluoridation (it used to, but it withdrew its endorsement a few years ago). Rather, it simply sets maximum allowable levels, as it does for many other toxins.
    – Flimzy
    Aug 27, 2012 at 1:51
  • @Flimzy Careful with "toxins". The EPA does set a limit on fluoride in water, but the term is "contaminants". The EPA notes that fluoride is a "water additive which promotes strong teeth". Like many things, a little is good, too much is bad. For example, they regulate chlorine, a "water additive used to control microbes" and other chemicals used in disinfecting drinking water. They also measure "turbidity" which is just how cloudy the water is. epa.gov/ground-water-and-drinking-water/…
    – Schwern
    Jul 13, 2018 at 17:34
  • Here's what the EPA had to say about flouride as of 2011. epa.gov/sites/production/files/2015-10/documents/… They mostly defer to the CDC who unequivocally support fluoridated water. cdc.gov/fluoridation/index.html HHS as of 2015 recommends 0.7 mg/L. ada.org/~/media/EBD/Files/…
    – Schwern
    Jul 13, 2018 at 17:40
  • @Schwern: "Like many things, a little is good, too much is bad" -- citation needed (and more on-topic on other questions on this site, I'm sure)
    – Flimzy
    Jul 14, 2018 at 16:06

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