Fluoridation Side Effects
Does water fluoridation
have negative side effects?
(Note by Andrew Saul: Fluoridation of water owes its continued existence more to politics than to science. If safety and effectiveness are truly considered, fluoride would be questionable even as a prescription drug. But to freely add it to public water supplies, often without any public vote whatsoever, is far beyond questionable. Mr. Meiers' discussion of the dangers of fluoride is important reading.)
The National Health
Service (NHS) Centre for Reviews and Dissemination at the
This is not a new
experience. Fears of undesired effects of the controversial "public
health measure" have never been taken serious by its promoters. Even
though animal experimentation on fluoride and cancer, performed long before
any fluoridation experiment was started in the United States [Meiers 1984,
1986], could have given reason for concern, investigations into possible
fluoride effects on human cancer victims were not initiated by promoters of
the measure prior to any fluoridation efforts nor in the course of the first
experimental trials, but by opponents whose charges posed a threat to the
continuing supply of public funds and thus necessitated appropriate replies
[American Dental Association 1952]. For example, at government hearings in
Relative to the city of
Grand Rapids, fluoridated since January 1945, Perkins wrote:
It was these claims that
prompted Swanberg  to evaluate the cancer data of
"The death rate from
Several studies published
after the 1956 Newburgh-Kingston "final report" focused on possible
effects of natural fluoride waters on the incidence or mortality of cancer
and revealed some major shortcomings. They were essentially static (comparing
data of just one year) as opposed to the time-trend analyses quoted above.
Further-more, the concentration of natural fluoride varies (even in one and
the same water supply), and so does the num-ber of registered water supplies
within each municipality [Heasman and Martin 1962; Glattre and Wiese 1979].
Therefore, it seems to make no sense to compare areas with a water fluoride
level of 0.06-0.10 mg/l to areas with 0.11-0.5 mg/l, as Glattre and Wiese do,
nor to arrange fluoride cities into groups based on a difference of one
hundredth mg/l (i.e. 0,5-0,99 vs.1 mg/l and more) as Kinlen [1974,
1975] does. Where more than one water source supplies a local authority some
authors calculated "weighted means" [Chilvers and
"The method for
obtaining the ratios shown in table I was to calculate for each sex and each
age group the number of cases that would be expected in the population in
question in each fluoride category if the total number of cases in all areas
combined was distributed uniformly." That means, he pooled the groups to
calculate his "expected" cancer deaths and thus used a reference
population partly exposed to the variable to be tested! While the
In case fluoride increases the number of deaths, inclusion of exposed people in the reference population would raise the number of (speculative) "expected" deaths in the groups to be examined (depending on population structure). As Standardized Mortality Ratios (SMR´s) are calculated by dividing the number of observed cancer deaths per 100,000 people (O) by the number of "expected" cancer deaths per 100,000 people (E), the SMR (O:E) becomes the lower the higher the "expected" (E) rate. This kind of SMR calculation applied in time-trend studies to populations of different size and structure (fluoridated vs. non-fluoridated cities) using a shifting refer-ence population (USA 1950, 1960, 1970 as the standard for the corresponding census years) creates the artifact of decreasing cancer death rates in fluoridated cities.
An example: In a hypothetical population with no change both in population structure and the number of cancer deaths during 1950 to 1970, applying U. S. data in 1950 by age, gender and race to calculate the number of deaths expected for 1950 in that population, and likewise U.S. data in 1960 and 1970 for those respective years, will result in an increasing number of expected deaths in the time span 1950 to 1970, since cancer death rates rose in the U.S. during that time. As the number of deaths expected in the hypothetical population will increase, i.e. "E" becomes higher, the O:E ratio (SMR) becomes lower. Thus one will be able to show that the cancer death rates decreased in that population (while, as presupposed above, nothing happened at all with the actual rates). What a large increase in cancer death rates would be required just to balance the misleading SMR calcu-lations for the hypothetical population if it were exposed to a carcinogen to be evaluated!
This is why the
re-analyses by Smith  as well as Kinlen and Doll  of the
Yiamouyiannis and Burk  study on the fluoridation-cancer link are
useless. Of these, the Smith paper got a high ranking according to the
As the Grand Rapids and Newburgh/Kingston data show, there are large fluctuations of cancer death rates over time in individual cities so that it isn´t appropriate to select just two data points for statistical evaluation, but the best approach would be to make a linear regression analysis to compare rates before and after fluoridation started. As differences might be small it seems to be a good idea to pool the data of several fluoridated cities and to compare them to a set of non-fluoridated ones.
In 1975, Yiamouyiannis and Burk reported to the U.S. Congress that a set of 20 U.S. central cities had almost identical cancer mortality rates (cancer deaths per 100,000 people per year) between 1940 and 1950, but that since fluoridation started (in 1952-1956) in a group of ten of these cities their cancer death rate increased faster than that of the ten cities remaining non-fluoridated (Fig. 3). The study was later published in the Journal "Fluoride" [Yiamouyiannis and Burk 1977] and caused quite a stir.
Early in 1976, a
representative of the National Cancer Institute (NCI) claimed in a letter to
Congressman Delaney that the NCI´s re-analysis showed that the increase was
entirely due to changes in the age, race and sex structure of the population
in question [Fredrickson 1976]. While refusing congressional requests for
detailed data (weighted or unweighted rates used? Which reference population?
etc.), the NCI clandestinely has passed this data on to other scientists
[Yiamouyiannis 1977] who reported them as their "independent analysis"
[Doll and Kinlen 1977;
However, the main point of disagreement between the statisticians is that whereas Burk and his group derived putative "observed Cancer Death Rates" (CDRo) by linear regression analysis of all available and pertinent data, i.e. the crude CDR´s characterizing the observation period of 1953 to 1968, and extrapolation to 1950 and 1970, other investigators have taken reported or pericensal CDRo figures for 1950 and 1970. "If, as they say, only the censal or pericensal data for 1950 or 1970 ought to be taken into account, the association between fluoridation and cancer is wiped away by adjustment. If instead, as we insist, the intermediate data for 1953 through 1968 must be used, a large association remains, notwithstanding adjustment" [Graham et al. 1987]. Neither regression analysis of cancer death rates [Mahoney et al. 1991] nor calculation of intercensal population by interpolation of data acquired in census years [Cohn 1992] seem to be unacceptable methods. Furthermore, a look at age-specific cancer mortality data for the twenty cities, unfortunately only available for 1970, indicates a higher cancer mor-tality at an earlier age in the fluoridated group (Fig. 4). The difference is obvious in these large populations even though people in non-fluoridated cities are exposed to fluoride from sources other than drinking water (tablets, drops, mouthwashes, topical applications, canned foods prepared in fluoridated cities, etc.).
hitherto essentially looked for evidence in human populations of a per se
carcinogenic effect of fluoride, substantiated by more recent in-vitro
experiments [Tsutsui et al. 1984; Jones et al. 1988; Lasne et al. 1988], the
question raised by Perkins in 1952 relative to the promoter effects of
fluorides has still not been addressed, neither by health officials in
general nor by the York team. Humans today are exposed to not one but many
different carcinogenic agents (including chemicals, viruses, ionizing
radiation) which interact in very intri-cate ways. Fluoride is known to
inhibit some enzymes and to activate others. Fluoride inhibits the enzymatic
deacetylation of N-Hydroxy-Acetylaminofluorene [
According to a WHO scientific group "the occurrence of tumors earlier than in the controls, without increased incidence" is among the types of responses "used to classify chemicals as carcinogens" [WHO 1969].
Enhancing effects are also apparent from some life table data published in the National Toxicology Program carcinogenicity test of sodium fluoride [NTP 1990]. This test had been requested by the U.S. Congress during hearings in 1977. Back then, NCI representative Kraybill  presented a list of publications which, he al-leged, had already shown that sodium fluoride has no carcinogenic activity. However, not a single one of the publications on his list had anything to do with fluoride and cancer. Anyway, the start of the carcinogenicity test requested by Congress was announced four years later [Whitmire 1981]. After another four years, a first result was declared inadequate because the low fluoride semisynthetic diet "was deficient in several vitamins and minerals" [NTP 1985]. Another two-year study was scheduled to begin in October 1985. The report, released in 1990, focused on the occurrence of a rare form of cancer, osteosarcoma, in several of the male (but not the fe-male) dosed rats used in the study [NTP 1990]. This evidence of carcinogenicity was downgraded to be "equivocal".
Nevertheless, a few
epidemiological studies addressed a possible influence of water fluoridation
on the incidence of osteosarcoma in humans. It occurs in less than one in
100,000 people or about 0.1 percent of all reported can-cers, and therefore
it would be hard to detect small increases in risk (on the order of five to
ten percent) [USPHS 1991]. Examinations in a very limited number of
afflicted people led to conflicting results. The study designs (e.g.
exclusion of people formerly exposed to some radiation) reveal that still the
search for a per se carcinogenic effect of fluoride was in the foreground.
There seems to be agreement that osteosarcoma incidence in the
In summary, the
Association (1952): "
Cohn P.D. (1992): "A brief report on the association of drinking water fluoridation and the incidence of osteosarcoma among young males"; New Jersey Department of Health, Nov. 8
Doll R., Kinlen L.
(1977): "Fluoridation of water and cancer mortality in the
Dophuoc H., Bompart G., Bourbon P. (1981): "Effects of hydrogen fluoride on benzo(a)pyrene and dimethylnitrosamine metabolism in rats"; Naturwiss. 68: 621
Dophuoc H., Bompart G., Bourbon P., Bouteille L. (1983): "Action du fluorure sur le métabolisme hépatique de la diméthyl-nitrosamine et du benzo(a)pyrène chez le rat"; Toxicol. Eur. Res. 5: 31
Fredrickson D.S. (1976): Letter to Hon. J. J. Delaney, Feb. 6, 1976; reproduced in: The National Cancer Program, Part II: Fluoridation of Public Drinking Water , Hearings before a subcommittee of the committee on government operations, House of Representatives, 95th Congress, 1st session, Sept. 21 and Oct. 12, 1977; Washington, p. 356
Graham J.R., Burk D., Morin P. (1987): "A current restatement and continuing reappraisal concerning demographic variables in American time-trend studies on water fluoridation and human cancer"; Proc. Pennsylv. Acad. Sci. 61:138
Irving C.C. (1966): "Enzymatic deacetylation of N-Hydroxy-2-Acetylaminofluorene by liver microsomes"; Cancer Res. 26:1390
Kinlen L. (1974): "Cancer incidence in relation to fluoride level in water supplies"; Commun. Health 6:69
Kinlen L. (1975): "Cancer incidence in relation to fluoride level in water supplies"; Brit. Dent. J. 138:221
Kinlen L., Doll R. (1977): "Cancer and Fluoride"; The Lancet II, 1039
Kraybill H. (1977): "The National Cancer Program, Part II: Fluoridation of Public Drinking Water, Hearings before a sub-committee of the committee on government operations, House of Representatives, 95th Congress, 1st session, Sept. 21 and Oct. 12, 1977; Washington , Government Printing Office, p. 239
Lasne C., Lu Y.P., Chouroulinkov L.(1988):"Transforming activities of sodium fluoride in cultured Syrian Hamster Embryo and BALB/3T3 cells"; Cell Biol. Toxicol. 4:311
Mahoney M.C., Nasca P.C.,
Burnett W.S., Melius J.M. (1991): "Bone cancer incidence rates in
McDonagh M., Whiting P., Bradley M., Cooper J., Sutton A., Chestnutt I., Misso K., Wilson P., Treasure E., Kleijnen J. (2000): "A systematic review of public water fluoridation", NHS Centre for Reviews and Dissemination, University of York
Meiers P. (1984):
"Zur Toxizität von Fluorverbindungen mit besonderer Berücksichtigung der
Onkogenese"; Verlag für Medizin,
Meiers P. (1986): "Experimente ueber Fluoridwirkungen im Krebsgeschehen", Erfahrungsheilkunde No. 6:424-432
NTP (1985): "Statement to accompany preliminary data tables from the NTP two-year sodium fluoride study performed Dec. 1981 to Dec. 1983 – prepared July 29, 1985"
NTP (1990): "Toxicology and carcinogenesis studies of sodium fluoride (CAS No. 7681-49-4) in F344/N rats and B6C3F1 mice (Drinking Water Studies)", National Toxicology Program, Technical Report Series 393, U.S. Department of Health and Human Services
Oldham P.D., Newell D.J. (1979): "Letter to the editors"; Appl. Statist. 28: 184
Perkins C.E. (1952):
"The truth about water fluoridation"; published by the Fluoridation
Schepers G.W.H. (1961): "Neoplasia experimentally induced by beryllium compounds"; Progr. Exp. Tumor Res. 2:203
Schlesinger E.R., Overton D.E., Riverhead L.I., Chase H.C., Cantwell K.T. (1956): "Newburgh-Kingston caries-fluorine study. XIII. Pediatric findings after ten years"; J. Am. Dent. Assoc. 52:296
Schuld A. (2000): "UK Review", http://www.bruha.com/fluoride/html/uk_review.html (Oct. 2000)
Smith A. H. (1980):
"An examination of the relationship between fluoridation of water and
cancer mortality in 20 large
Swanberg H. (1953):
"Fluoridation of water and its relation to cancer",
Tannenbaum A., Silverstone H. (1949): "Effect of low environmental temperature, dinitrophenol, or sodium fluoride on the formation of tumors in mice", Cancer Res. 9:403
Taylor A. (1952): Testimony, Feb. 19, "Chemicals in Food and Cosmetics", Hearings before the House Select Committee to investigate the use of chemicals in foods and cosmetics, House of Representatives, 82nd Congress, 2nd session, pursuant to H. Res. 74 and H. Res. 447, Part 3, U. S. Government Printing Office
Taylor A. (1954): "Sodium fluoride in the drinking water of mice", Dental Digest 60:170
Taylor A., Taylor N.C. (1965): "Effect of sodium fluoride on tumor growth", Proc. Soc. Exp. Biol. Med. 119:252
Tsutsui T., Suzuki N., Ohmori M.(1984): "Sodium fluoride-induced morphological and neoplastic transformation, chromo-some aberrations, sister chromatid exchanges, and unscheduled DNA synthesis in cultured Syrian Hamster Embryo cells"; Cancer Res. 44:938
USPHS (1991): "Review of fluoride. Benefits and Risks. Report of the ad hoc subcommittee on fluoride of the Committee to coordinate environmental health and related programs", Department of Health and Human Services, U. S. Public Health Service; (Study of Hoover et al. (NCI) in Appendix F)
Wagner H. J. (1981): "Der Einfluß von Fluorid, Licht und 3,4-Benzpyren auf die Tumorinduktion bei NMRI-Mäusen"; Inau-gural Dissertation, Erlangen-Nürnberg
Whitmire C.E. (1981) : "Carcinogenesis bioassay of sodium fluoride"; Tox-Tips 56:56-19
WHO (1969) :
"Principles for the testing and evaluation of drugs for carcinogenicity.
Report of a WHO Scientific Group", World Health Organization, Technical
Report Series, No. 426,
Yiamouyiannis J., Burk D. (1975): "Cancer from our drinking water?", Congressional Record, Proceedings and debates of the 94th Congress, 1st session
Yiamouyiannis J. (1977): "The National Cancer Program, Part II: Fluoridation of Public Drinking Water", Hearings before a subcommittee of the committee on government operations, House of Representatives, 95th Congress, 1st session, Sept. 21 and Oct. 12, 1977; Washington, Government Printing Office
Yiamouyiannis J., Burk D. (1977): "Fluoridation and cancer. Age dependence of cancer mortality related to artificial fluori-dation"; Fluoride 10:101
Ziegelbecker R. (1987): "Zur Frage eines Zusammenhangs zwischen Trinkwasserfluoridierung, Krebs und Leberzirrhose"; gwf – Wasser – Abwasser 128: 111
Reprinted with permission of the author, Peter Meiers.
Andrew Saul is the author of the books FIRE YOUR DOCTOR! How to be Independently Healthy (reader reviews at http://www.doctoryourself.com/review.html ) and DOCTOR YOURSELF: Natural Healing that Works. (reviewed at http://www.doctoryourself.com/saulbooks.html )
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