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HEALTH EFFECTS: Fluoride's Mutagenicity (Genotoxicity)
(Genotoxicity is a word in genetics defined as a destructive effect on a cell's genetic material (DNA, RNA) affecting its integrity. Genotoxins are mutagens; they can cause mutations. Genotoxins include both radiation and chemical genotoxins. A substance that has the property of genotoxicity is known as a genotoxin.)
Key Findings - Fluoride's Mutagenicity:
1) According to the National Toxicology Program, "the
preponderance of evidence" from laboratory 'in vitro'
studies indicate that fluoride is a mutagenic compound.
2) Many substances which are mutagens, are also
carcinogens (i.e. they can cause cancer).
3) While the concentrations of fluoride causing mutagenic
damage in the in vitro studies is higher than the
concentrations found in human blood, there are certain
"microenvironments" in the body (e.g. the bones) where
the concentrations of fluoride can accumulate to levels
comparable to, or in excess of, those causing mutagenic
effects in the laboratory.
4) A study comparing fluoride's ability to cause mutagenic
damage in cells from apes and humans versus cells from
rodents, found that the cells from apes and human were
much more sensitive to fluoride's mutagenic effects
5) Five studies on fluoride-exposed humans, published
since 1994, have reported an increased incidence of
mutagenic damage when compared to comparable controls. Two studies conducted during this period
did not find this effect. The primary type of mutagenic damage found in fluoride-exposed humans was
sister chromatid exchange.
Excerpts from In-Vivo Human Studies
- Fluoride's Mutagenicity: (back to
top)
"A number of investigators have utilized
the SCE (Sister Chromatid Exchange)
test to study the genotoxicity of fluoride.
In the present study, human populations
directly exposed to fluoride in drinking
water in endemic regions of North
Gujarat were investigated to evaluate the
possible effect of fluoride on SCE. To
the best of our knowledge this is the first
report on genotoxic effects following
long-term fluoride intake in an endemic
area in India... The results of the present
investigation suggest that in fluorideaffected persons exposed to 1.95 - 2.2
ppm fluoride in drinking water
chromosomal alterations as indicated by
SCE frequency and chromosome
aberrations were higher than in normal
persons exposed to 0.6 - 1.0 ppm
drinking water fluoride."
SOURCE: Sheth FJ, et al. (1994). Sister
chromatid exchanges: A study in
fluorotic individuals of North Gujurat.
Fluoride 27: 215-219.
"In recent years, SCE analysis has been considered to be a sensitive method for detecting DNA
damage. There is a clear relationship between a substance's ability to induce DNA damage, mutate
chromosomes, and cause cancers. The SCE frequency in the human body in peripheral blood
lymphocytes is very steady, and does not vary with age or sex. Any increase of the SCE frequency is
primarily due to chromosome damage. Thus using a method to detect SCE for exploring the toxicity
and harm caused by fluoride is of great importance. The results in this paper showed an obvious
increase in the SCE frequency of the patients with fluorosis, indicating that fluorine had some
mutagenic effects, and could give rise to DNA damage. The fact that the SCE frequency of the healthy
people in the endemic regions was also higher than that of the controls in the non-endemic regions
suggests that early harm by fluorine can be cytogenetically detected in the sub-clinical patients with
fluorosis who could not be given an early diagnosis clinically. Under normal circumstances, the
incidence rate of micronucleus is very low, usually 0-2%. The normal value checked in this paper is 0-
2%, which agrees with that reported in the literature. The results show that the mean value of the
micronucleus rate of the fluorine-toxic patients was 1.94 + 0.86% (range 1-15%) which is 2-3 times
more than that of 0.57 + 0.44% in the controls... To sum up, the rise of SCE and MN in the peripheral
blood lymphocytes of the fluorine-intoxicated patients indicates that fluorine is a mutagenic agent
which can cause DNA and chromosomal damage."
SOURCE: Wu DQ, Wu Y. (1995). Micronucleus and Sister Chromatid Exchange Frequency in
Endemic Fluorosis. Fluoride 28: 125-127.
"Our study here provided evidence that the air pollutants at the phosphate fertilizer factory, of which
HF and SiF4 are the main chemicals, could induce SCEs in human blood lymphocytes in vivo. These
results imply that even if the concentration of the chemical pollutants in the air is low (e.g.F: 0.50 -
0.80 mg/m3), it may cause damage to genetic material at the chromosomal level, although the general
health of the workers in the phosphate fertilizer factory was found to be satisfactory... HF and SiF4 are
the main air pollutants; however, dust containing fluoride, phosphate fog, ammonia (NH3), and sulfur
dioxide (SO2) were also released in small amounts into the air during fertilizer production. These
pollutants may also make a contribution to the induction of SCES. Hence, further study of the
induction effect of HF or SiF4 alone on SCEs in human lymphocytes to understand the cytogenetic
damage of fluoride pollution in the air would be needed."
SOURCE: Meng Z, et al. (1995). Sister-chromatid exchanges in lymphocytes of workers at a
phosphate fertilizer factory. Mutation Research 334(2):243-6.
"Our study here provides evidence that the air pollutants at the phosphate fertilizer factory, in which
HF and SiF4 are the main chemicals, could induce both CA (chromosomal aberrations) and MN
(micronuclei) in human blood lymphocytes in vivo. Our earlier observation on sister-chromatid
exchanges (SCE) of peripheral blood lymphocytes from this same population showed that the mean
SCEs/cell of the workers was significantly higher than that of the controls (p < 0.01) [13]. The results
of our studies imply that even if the concentration of the chemical pollutants in the air is low (e.g. F
0.50-0.80 mg/m 3), it may cause damage to genetic material at the chromosomal level... it is suggested
that chromosomal abnormalities induced by fluoride could be the results from interaction with the
enzymes responsible for DNA synthesis or repair, rather than directly with DNA."
SOURCE: Meng Z, Zhang B. (1997). Chromosomal aberrations and micronuclei in lymphocytes of
workers at a phosphate fertilizer factory. Mutation Research 393: 283-288.
"Our results indicate that there is a significant increase in the frequencies of chromosome aberrations
and SCE in one of the village populations exposed to a fluoride concentration higher than the
permissible limit. The lymphocytes of these residents were also more susceptible to a clastogen such as
Mitomycin-C than the other populations and displayed a significant increase in chromosome
aberrations."
SOURCE: Joseph S, Gadhia PK. (2000). Sister chromatid exchange frequency and chromosome
aberrations in residents of fluoride endemic regions of South Gujarat. Fluoride 33: 154-158.
Consensus View of In-Vivo Animal Studies - Fluoride's Mutagenicity: (back to top)
"The disagreements among the in vivo tests for chromosome damage in rodents can not yet be
reconciled. There are a few reports of positive results for chromosome aberrations in rodent bone
marrow and testes, but other studies, using similar protocols and dose ranges, have reported no induced
chromosome damage... Therefore, at this time, the in vivo clastogenicity of fluoride should be
considered unresolved."
SOURCE: Department of Health and Human Services. (1991). Review of fluoride: benefits and risks.
Report of the Ad Hoc Subcommittee on Fluoride. Washington, DC. p. 70.
Excerpts from In-Vivo Animal Studies - Fluoride's Mutagenicity: (back to top)
"The results concerning the SCE rate induced by sodium fluoride are shown in Table 1. Although no
significant increase was observed with the two low doses tested (from 2 to 4 mg/kg), a significant SCE
increase was found with the three highest doses. The cumulative frequency of these data reveals about
70% of cells with four SCE in the group treated with the high dose, a value which is twice the level of
the negative control."
SOURCE: Velazquez-Guadarrama N, Madrigal-Bujaidar E, Molina D, Chamorro G. (2005). Genotoxic
evaluation of sodium fluoride and sodium perborate in mouse bone marrow cells. Bulletin of
Environmental Contamination and Toxicology 74:566-72.
"We tested the induction of mutagenic effects by in vivo and in vitro bone marrow micronucleus tests.
A significant increase in micronucleated polychromatic erythrocytes was observed 24 H after
intraperitoneal injection of sodium fluoride at a dose of 30 mg/kg body weight. In the in vitro
micronucleus test, the frequency of micronucleated polychromatic erythrocytes was increased
significantly at concentrations of 2 and 4 MM. These results indicate that the micronucleus test may be
useful in evaluating the cancer risk of sodium fluoride."
SOURCE: Suzuki Y, Li J, Shimizu H. (1991). Induction of micronuclei by sodium fluoride. Mutation
Research 253:278.
"Genotoxicity of Sodium fluoride was evaluated in mice in vivo with the help of different
cytogenetic assays. The frequency of chromosome aberration was dose - and time -
dependent but not exactly route-dependent. Fractionated dosing induced less aberration.
Incidence of micronucleus and sperm abnormality increased with dose. Relative sensitivity of
the three assays has been found to be: Sperm abnormality > Chromosome aberration >
Micronucleus. The present results have revealed the mutagenic property of NaF."
SOURCE: Pati PC, Bhunya SP. (1987). Genotoxic effect of an environmental pollutant,
sodium fluoride, in mammalian in vivo test system. Caryologia 40:79-87.
"The test animals were fed with low-grade food during 2-5 months under conditions of acute
and chronic action of hydrogen phosphide and hydrogen fluoride induced by inhalation, that
resulted in the pronounced impairment of the chromosomal apparatus of the bone marrow
cells in the rats. A principal possibility has been established of modification of the hydrogen
phosphide and hydrogen fluoride cytogenetic effect by the alimentary action. In particular, it
has been found that the effect is significantly higher when the rats are fed with a low-grade
ration than under conditions of balanced nutrition."
SOURCE: Tazhibaev ShS, et al. (1987). [Modifying effect of nutrition on the mutagenic
activity of phosphorus and fluorine compounds]. Vopr Pitan. Jul-Aug;(4):63-6.
"Cytological studies on bone marrow cell chromosomes and spermatocytes showed that 1-
200 ppm F (as sodium fluoride) was able to induce chromosomal changes in a dosedependent manner. The frequency of the induced chromosomal damage was significantly
higher in each treatment than in the controls. The observed abnormalities included
translocations, dicentrics, ring chromosomes, and bridges plus fragments, or fragments by
themselves. There was a significant correlation between the amount of fluoride in the body
ash and the frequency of the chromosomal abnormalities."
SOURCE: Mohamed AH, Chandler ME. (1982). Cytological effects of sodium fluoride on
mice. Fluoride 15: 110-18.
"Cryolite concentrations of 3 mg/m3 as well as a mixture of 0.5 mg/m3 of cryolite and 0.35
mg/m3 of hydrogen fluoride increases 3 1/2 to 4 1/2 times (over controls) the percentage of
cells with chromosomal aberrations in the bone marrow of rats. The data indicate the need for
further study of the mutagenic features of fluoride compounds in relation to their potential for
harmful impact on the mechanism of inheritance in humans."
SOURCE: Gileva EA, et al. (1975). The mutagenic activity of inorganic fluorine compounds.
Fluoride 8: 47-50.
"The mutagenic effect of hydrogen fluoride in concentration 1.0 mg/m-3 was studied in rats
and mice. Prolonged inhalation of this compound increased the frequency of cells with
chromosome abnormalities in the bone marrow of albino rats. The mutagenic effect was
higher in older animals."
SOURCE: Voroshilin SI, et al. (1975). Mutagenic effect of hydrogen fluoride on animals. Tsitol
Genet. 9: 42-44.
"On the grounds of the results obtained during our experiments F compounds are able to
produce certain changes in chromosomes from somatic cells of animals treated in vivo by
them... Most of the aberrations observed in the case of bone marrow cells were chromatidtype aberrations... [W]e entertain the opinion that the main damage to chromosomes during
our experiments with F compounds also took part during the S-phase... [T]hese data enable
us to consider as sufficiently established the conclusion that inorganic fluorine compounds
may present a mutagenic danger to human beings."
SOURCE: Voroshilin SI, et al. (1973). Cytogenetic effect of inorganic fluorine compounds on
human and animal cells in vivo and in vitro. Genetika 9: 115-120.
"In 54 tests involving 991 mice bearing transplanted tumors and 58 tests including 1817
tumor-bearing eggs, data were obtained which indicated a statistically significant acceleration
of tumor tissue growth in association with comparatively low levels of NaF."
SOURCE: Taylor A, Taylor NC. (1965). Effect of sodium fluoride on tumor growth.
Proceedings of the Society for Experimental Biology and Medicine 119:252-255.
Consensus Statements on In-Vitro Laboratory Studies - Fluoride's Mutagenicity: (back to top)
"In summary, sodium fluoride is mutagenic in cultured mammalian cells and produces transformation
of Syrian hamster cells in vitro. The reports of in vivo cytogenetic studies are mixed, but the
preponderance of the evidence indicates that sodium fluoride can induce chromosome aberrations and
sister chromatid exchanges in cultured mammalian cells. These mutagenic and clastogenic effects in
cultured cells are supported by positive effects in Drosophila germ cell tests that measure point
mutations and chromosome breakage. In vivo tests in rodents for chromosome aberrations provide
mixed results that cannot readily be resolved because of differences in protocols and insufficient detail
in some study reports to allow a thorough analysis. The mechanism(s) by which these effects result
from exposure to sodium fluoride is not known."
SOURCE: National Toxicology Program [NTP] (1990). Toxicology and Carcinogenesis Studies of
Sodium Fluoride in F344/N Rats and B6C3f1 Mice. Technical report Series No. 393. NIH Publ. No 91-
2848. National Institute of Environmental Health Sciences, Research Triangle Park, N.C.
"The effects of fluoride as a mutagen, carcinogen, and antimutagen are inconsistent, but the
preponderance of evidence in cultured mammalian cells indicate that sodium fluoride can
induce chromosome aberrations and sister chromatid exchanges.”
SOURCE: Bassin EB. (2001). Association Between Fluoride in Drinking Water During Growth and
Development and the Incidence of Ostosarcoma for Children and Adolescents. Doctoral Thesis,
Harvard School of Dental Medicine. p. 15.
"Fluoride (as sodium fluoride) should be considered capable of inducing chromosomal aberrations,
micronuclei, and sister-chromatid exchanges in vitro in mammalian cells, although the results from
such studies have been inconsistent."
SOURCE: Environment Canada. (1993). Inorganic Fluorides: Priority Substances List Assessment
Report. Government of Canada, Ottawa.
"Genotoxicity studies are highly dependent on the methods used... Despite the apparently contradictory
reports appearing in the published literature, fluoride has not been shown to be mutagenic in bacteria
(Ames test). In some studies fluoride has been reported to induce gene mutations in both cultured
rodent and human cells. Fluoride has also been reported to transform rodent cells in vitro. Although
there is disagreement in the literature concerning the ability of fluoride to be a clastogen (induce
chromosome aberrations) in cultured cells, it has been suggested that fluoride can cause chromosome
aberrations in rodent and human cells. Fluoride induced primarily chromatid gaps and chromatid
breaks, indicating that the cells are most responsive in the G stage of the cell cycle, i.e., after
chromosome duplication in preparation for cell division. Negative results reported in some cytogenetic
studies are likely the effect of inadequate test protocols.... Although the mechanism(s) by which these
cellular effects result from exposure to fluoride is not known, a number of possible mechanisms have
been proposed to explain the genetic activity observed. These mechanisms have been based on the
observed reactions of fluoride in solution with divalent cations or necleotides, or the physiological and
biochemical responses of cells treated with fluoride. Sodium fluoride inhibits both protein and DNA
synthesis in cultured mammalian cells. The inhibition of DNA synthesis may be a secondary effect of
the inhibition protein synthesis, or a result of the direct inhibition of DNA polymerase. Fluoride can
react with divalent cations in the cell so as to affect enzyme activities that are necessary for DNA or
RNA synthesis, or chromosome metabolism or maintenance; it may react directly with DNA as part of
a complex; or it ca disrupt other cellular processes such as cell differentiation or energy metabolism."
SOURCE: Department of Health and Human Services. (1991). Review of fluoride: benefits and risks.
Report of the Ad Hoc Subcommittee on Fluoride. Washington, DC. p. 70.
"Fluoride has displayed mutagenic activity in studies of vegetation, insects, and mammalian oocytes.
There is a high correlation between carcinogenicity and mutagenicity of pollutants, and fluoride has
been one of the major pollutants in several situations where a high incidence of respiratory cancer has
been observed. For these reasons, the relation between airborne fluoride and incidence of lung cancer
needs to be investigated."
SOURCE: Marier J, Rose D. (1977). Environmental Fluoride. National Research Council of Canada.
Associate Committe on Scientific Criteria for Environmental Quality. NRCC No. 16081.
Excerpts from In-Vitro Laboratory Studies - Fluoride's Mutagenicity: (back to top)
"As cells were exposed to higher doses of fluoride, the percentage of L-02 cells with DNA
damage increased. This result is consistent with other studies... Therefore, considereing
previous studies, we think that fluoride can cause lipid peroxidation, DNA damage and
apoptosis, and that there is a positive relationship among these changes."
SOURCE: Wang AG, et al. (2004). Effects of fluoride on lipid peroxidation, DNA damage and
apoptosis in human embryo hepatocytes. Biomedical and Environmental Sciences 17: 217-
22.
"For fluoride concentrations of 2 ppm to 35 ppm, non vital cells of less than 10% could be
shown. After incubation with 71 ppm and 213 ppm Olaflur, there were 15% and 43% of
damaged cells, respectively. Weak genotoxic effects on mucosal cells as well as on
lymphocytes could be demonstrated at all concentrations tested. In fluoride concentrations of
213 ppm genotoxicity increased to max."
SOURCE: Kleinsasser NH, et al. (2001). [Cytotoxicity and genotoxicity of fluorides in human
mucosa and lymphocytes]. Laryngorhinootologie 80(4):187-90.
"To investigate the effects of fluoride on DNA damage as well as the effects of selenium and
zinc against fluoride respectively or jointly in pallium neural cells of rats, single cell gel
electrophoresis was used to detect the DNA damage of neural cells prepared in vitro. The
results showed that the degree of DNA damage in the fluoride group and the selenium group
were significantly greater than that in control group(P < 0.01). The damage in the fluoride
group was even more serious. The damage in the fluoride + selenium group and fluoride +
zinc group was slighter than that in the fluoride group but with no significant difference. The
extent of DNA damage in the fluoride + selenium + zinc group was significantly slighter than
that in the fluoride group(P < 0.05). It suggested that fluoride and selenium could induce DNA
damage in pallium neural cells of rats respectively."
SOURCE: Chen J, et al. (2000). [Effects of selenium and zinc on the DNA damage caused by
fluoride in pallium neural cells of rats]. Wei Sheng Yan Jiu. 29(4):216-7.
""In the present work, 13 compounds [chlordane, Arochlor 1260, di(2-ethylhexyl)phthalate, 1,1,1-
trichloro-2, 2-bis(4-chlorophenyl)ethane, limonene, sodium fluoride, ethionine, o-anisidine, benzoyl
peroxide, o-vanadate, phenobarbital, 12-O-tetradecanoylphorbol 13-acetate and clofibrate] have been
tested for their ability to induce morphological transformation and affect intercellular communication
in Syrian hamster embryo (SHE) cells... In vitro morphological transformation of SHE cells is now one
of the most frequently used cell transformation systems. Around 500 chemicals have been tested in this
system, and a good correlation has been obtained with the ability of compounds from different
chemical groups to cause tumours in animals and humans. The SHE cell transformation assay also
responds to tumour promoters and carcinogens not detected by tests for genotoxicity... [N]ine of the 13
tested substances (TPA, o-vanadate, DEPH, phenobarbital, Arochlor 1260, clofibrate, o-anisidine,
limonene and NaF) are considered positive for induction of morphological transformation."
SOURCE: Rivedal E, et al. (2000). Morphological transformation and effect on gap junction
intercellular communication in Syrian hamster embryo cells as screening tests for carcinogens devoid
of mutagenic activity. Toxicology In Vitro 14(2):185-92.
"Significant increases in the frequencies of chromosome aberrations were induced in a doseand treatment time-dependent fashion when NaF was administered to [rat vertebral bone]
cells at 0.5 and 1.0 mM for 24 and 48 h. The results indicate that NaF is genotoxic to rat
vertebrae, providing a possible mechanism for the vertebrae, as a target organ of NaF
carcinogenesis."
SOURCE: Mihashi M, Tsutsui T. (1996). Clastogenic activity of sodium fluoride to rat
vertebral body-derived cells in culture. Mutation Research 368:7-13.
"The genotoxic effects of inorganic fluorides were investigated by treating cultured rat bone
marrow cells with varying concentrations (0.1-100 microM) of potassium fluoride (KF) and
sodium fluoride (NaF) for different durations (12, 24 and 36 h) and measuring the incidence of
cells with aberrations and number of breaks per cell. Both forms of fluoride were found to be
weak mutagens relative to the positive control N-methyl-N-nitro-N-nitrosoguanidine (MNNG).
A specificity of fluoride ion in inducing chromosome aberrations (CA) was indicated by the
observation that both NaF and KF behaved almost equivalently in this study and at
significantly higher variations from the results with potassium chloride (KCl) and sodium
chloride (NaCl)."
SOURCE: Khalil AM. (1995). Chromosome aberrations in cultured rat bone marrow cells
treated with inorganic fluorides. Mutation Research 343:67-74.
"The testing of hydrogen fluoride (HF) for its mutagenic activity by fumigation of barley
seedlings showed that the mutation rate was linear with dose. It was found that the cytogenic
effects of gaseous fluoride on grain crops was correlated with the fluoride content in plant
tissue."
SOURCE: Gritsan, NP. (1993). Cytogenetic effects of gaseous fluorides on grain crops.
Fluoride 26: 23-32.
"A significant increase in the incidence of chromosome aberrations was observed only in
cultures treated with NaF during early and/or middle S phases of cell cycle. These results
suggest that cytotoxicity and clastogenicity of NaF to cultured human diploid fibroblasts are
cell cycle dependent, and that the cells in early and middle S phases are more sensitive to
the effects."
SOURCE: Hayashi N, Tsutsui T. (1993). Cell cycle dependence of cytotoxicity and
clastogenicity induced by treatment of synchronized human diploid fibroblasts with sodium
fluoride. Mutation Research 290: 293-302.
"We show here that NaF is clastogenic not only in human cells but also in great ape cells. The
mechanism of NaF clastogenicity is still unknown, but the same profile of chromosomal
aberrations in man and chimpanzees suggests that its action on these cells and the response
of the cells will be consistent. The different response to NaF among non-human primates
might give us a clue to clarify the mechanism of NaF clastogenicity."
SOURCE: Kishi K, Ishida T. (1993). Clastogenic activity of sodium fluoride in great ape cells.
Mutation Research 301:183-8.
"We tested the induction of mutagenic effects by in vivo and in vitro bone marrow micronucleus tests.
A significant increase in micronucleated polychromatic erythrocytes was observed 24 H after
intraperitoneal injection of sodium fluoride at a dose of 30 mg/kg body weight. In the in vitro
micronucleus test, the frequency of micronucleated polychromatic erythrocytes was increased
significantly at concentrations of 2 and 4 MM. These results indicate that the micronucleus test may be
useful in evaluating the cancer risk of sodium fluoride."
SOURCE: Suzuki Y, Li J, Shimizu H. (1991). Induction of micronuclei by sodium fluoride. Mutation
Research 253:278.
"Sodium fluoride was found to induce gene-locus mutations at the thymidine kinase (tk) and
hypoxanthine guanine phosphoribosyl transferase (hgprt) loci in human lymphoblastoid cells."
SOURCE: Crespi CL, et al. (1990). Sodium fluoride is a less efficient human cell mutagen at
low concentrations. Environmental Molecular Mutagenesis 15:71-7.
"Based on these results and those previously reported for NaF and APC, it is proposed that
NaF-induced aberrations may occur by an indirect mechanism involving the inhibition of DNA
synthesis/repair."
SOURCE: Aardema MJ, et al (1989). Sodium fluoride-induced chromosome aberrations in
different stages of the cell cycle: a proposed mechanism. Mutation Research 223:191-203.
"Inducibility of chromosome aberrations of the cells following treatment with sodium fluoride
was also dependent upon the phase of cell cycle. Significant increase in the incidence of
chromosome aberrations was observed only in cultures treated during early and/or middle S
phases of the cell cycle. These results indicate that cytotoxicity and clastogenicity of sodium
fluoride to cultured human diploid fibroblasts are cell phase dependent, and that the cells in
early and middle S phases are more sensitive to these effects."
SOURCE: Suzuki N, Tsutsui T. (1989). [Dependence of lethality and incidence of
chromosome aberrations induced by treatment of synchronized human diploid fibroblasts with
sodium fluoride on different periods of the cell cycle]. [Article in Japanese] Shigaku. 77:436-
47.
"Sequential treatment of Syrian hamster embryo (SHE) cells with a chemical carcinogen
followed by sodium fluoride (NaF) resulted in a higher yield of morphologically transformed
cell colonies than treatment of the cells with carcinogen alone... This enhancement/promotion
of cell transformation by NaF was only expressed after the cells had been pretreated with
either direct-acting carcinogens or procarcinogens. Pretreatment of the cells with
noncarcinogens or weakly-acting carcinogens or administration of NaF prior to treatment with
the carcinogen failed to enhance the yield of transformation. Transformation was enhanced
even when the NaF treatment was delayed for several days after the carcinogen treatment.
However, the continued presence of NaF was necessary for maintenance of the increased
level of transformation. Removal of NaF prior to termination of the assay resulted in a reversal
of the transformed clonal morphologies to a normal phenotype such that the final yield of
transformants was decreased, but was still greater than that observed after carcinogen
treatment alone."
SOURCE: Jones CA, et al. (1988). Sodium fluoride promotes morphological transformation of
Syrian hamster embryo cells. Carcinogenesis 9: 2279-84.
"Sodium fluoride was found to induce morphological transformation of SHE cells seeded on a
feeder layer of X-irradiated cells at high concentrations (75-125 micrograms/ml). When the
cells were seeded in the absence of a feeder-layer, the transformation frequencies increased
in a dose-dependent manner with the concentrations of sodium fluoride ranging from 0 to the
highly toxic concentration of 200 micrograms/ml. In the BALB/3T3 cell system, sodium
fluoride was negative in the standard Kakunaga procedure, while through the experiment
designed by table L8 (2(7] of the orthogonal method, an initiating-like effect and a weak
promoting activity were detected within the concentrations ranging from a 25 micrograms/ml
to a 50 micrograms/ml concentration which is highly toxic for BALB/3T3 cells. From these
results, it is suggested that, besides a genetic mode of action, sodium fluoride could possibly
act through a non-genotoxic mechanism."
SOURCE: Lasne C, et al. (1988). Transforming activities of sodium fluoride in cultured Syrian
hamster embryo and BALB/3T3 cells. Cell Biology and Toxicology 4:311-24
"Chromosomal aberrations were recorded for all the concentrations used. Maximum effect at
all concentrations was observed after 24 hours of treatment. Several kinds of abnormalities
were revealed with the main ones being bridges, double bridges, sidearm bridges, bridges
with fragments, tripolar and multipolar anaphases with and without bridges, fragments, and
laggards. "Y" and "X" configurations were also noted at metaphase... The authors conclude
that sodium-fluoride may be considered to be clastogenic in these cells."
SOURCE: Albanese R. (1987). Sodium fluoride and chromosome damage (in vitro human
lymphocyte and in vivo micronucleus assays). Mutagenesis 2:497-9.
"While the results in this paper demonstrate the ability (of fluoride) to induce genetic damage
in cultured mammalian cells, the potential risks to animals or man are not addressed."
SOURCE: Caspary WJ, et al (1987). Mutagenic activity of fluorides in mouse lymphoma cells.
Mutation Research 187:165-80.
"The results are used to illustrate the problems associated with quantitative extrapolation from
in vitro tests to human risk, as follows. (1) There appears to be a threshold response
(clastogenicity vs. dose) with NaF at around 10 micrograms/ml (48 h exposure) but a more
definitive conclusion must await elucidation of the mechanisms of clastogenicity. (2) NaCl is
weakly clastogenic at 1000 times the threshold dose for NaF. The mechanisms are unlikely to
be similar. (3) No clastogenicity was detected with NaF below about 30% mitotic inhibition but
the relationship between clastogenicity and mitotic inhibition was similar for NaF and MMC.
(4) There was no obvious threshold in the relationship between clastogenicity and cell killing
with NaF. MMC was less clastogenic than NaF at equitotoxic doses. Observations 3 and 4
preclude the possibility of regarding the clastogenicity of NaF as a false positive by virtue of
associated cytotoxicity."
SOURCE: Scott D, Roberts SA. (1987). Extrapolation from in vitro tests to human risk:
experience with sodium fluoride clastogenicity. Mutation Research 189:47-58.
"These observations, and an analysis of the colony size of trifluorothymidine-resistant
mutants in TK+/- cells, suggest that sodium fluoride is clastogenic to dividing cultured
mammalian cells at high, toxic concentrations. Further work is desirable to investigate the
mechanism by which chromosomes are damaged at high concentrations of fluoride, since
without such a mechanistic understanding, extrapolation of our data to the human situation
must be insecure."
SOURCE: Cole J, et al. (1986). The mutagenicity of sodium fluoride to L5178Y [wild-type and
TK+/- (3.7.2c)] mouse lymphoma cells. Mutagenesis 1:157-67.
"The clastogenic effect of NaF has been tested by the use of several cytogenetic assay
systems, but the findings on its genotoxicity are not consistent. In this study, the effects of
NaF on chromosomes, unscheduled DNA synthesis (UDS) and sister-chromatid exchanges
(SCEs) were investigated using cultured human lymphocytes. For clastogenicity testing, cells
were treated for 24 h in various concentrations of NaF. At least two donors were tested for
each concentration and more than 10,000 cells were totally observed... Sodium fluoride
treatment had remarkable effects on the induction of isochromatid gaps and chromosome
breaks (NUpds)."
SOURCE: Kishi K, Tonomura A. (1984). Cytogenetic effects of sodium fluoride. Mutation
Research 130: 367.
"Mass cultures of cells treated with NaF (75 or 100 micrograms/ml) for 24 hr, followed by
continuous cultivation for 35 to 50 passages, developed the ability to grow in soft agar and to
produce anaplastic fibrosarcomas when injected into newborn hamsters. In contrast, no
morphological and neoplastic transformation was observed in untreated cells. Furthermore, a
significant increase in chromosome aberrations at the chromatid level, sister chromatid
exchanges, and unscheduled DNA synthesis was induced by NaF in a dose- and timedependent manner. These results indicate that NaF is genotoxic and capable of inducing
neoplastic transformation of Syrian hamster embryo cells in culture. A potential for
carcinogenicity of this chemical, which is widely used by humans, is suggested. However, the
carcinogenic risk of this chemical to humans may be reduced by factors regulating in vivo
dose levels."
SOURCE: Tsutsui T, Suzuki N, Ohmori M. (1984) Sodium fluoride-induced morphological and
neoplastic transformation, chromosome aberrations, sister chromatid exchanges, and
unscheduled DNA synthesis in cultured syrian hamster embryo cells. Cancer Research
44:938-41.
" A significant increase in the frequency of chromosome aberrations at the chromatid level
was observed in treated cells in a dose-dependent manner... These results suggest that NaF
causes DNA damage in human diploid fibroblasts in culture."
SOURCE: Tsutsui T, Suzuki N, Ohmori M, Maizumi H. (1984). Cytotoxicity, chromosome
aberrations and unscheduled DNA synthesis in cultured human diploid fibroblasts induced by
sodium fluoride. Mutation Research 139:193-8.
"The effect of treatment of cultured human oral keratinocytes with sodium fluoride (NaF) has
been investigated with respect to induction of unscheduled DNA synthesis (UDS)...
Significant levels of UDS were induced in a dose-related fashion by NaF treatment. The
results suggest that NaF causes DNA damage in cultured human oral keratinocytes."
SOURCE: Tsutsui T, Ide K, Maizumi H. (1984). Induction of unscheduled DNA synthesis in
cultured human oral keratinocytes by sodium fluoride. Mutation Research 140:43-8.
"The study, by light and fluorescent microscopy, of sternal and femoral bone marrow taken
from young Swiss mice exposed for period up to 280 days to elevated levels of sodium
fluoride in drinking water, has revealed morphologic abnormalities in cell structure and mitotic
figure formation in immature leukocytes. Alterations in the content and distribution of RNA
and DNA also appear after several weeks of exposure... The results of this investigation
indicate that young leukocytes chronically exposed to elevated fluoride levels have the
potential for an irreversible shift toward the formation of neoplasm."
SOURCE: Greenberg SR. (1982). Leukocyte response in young mice chronically exposed to
fluoride. Fluoride 15: 119-123.
"Human leucocytes in the cultures in vitro were exposed to the action of lead and fluorine
ions... Both factors caused structural and quantitative aberrations in the chromosome set,
which seems to indicate their mutagenic character. It is noteworthy that the smallest of the
applied concentrations of fluorine ions (3.15 x 10-5M) is equal to the concentration of these
ions in the running water of Szczecin, given for the prevention of caries."
SOURCE: Jachimczak D, Skotarczak B. (1978). The effect of fluorine and lead ions on the
chromosomes of human leucocytes in vitro. Genetica Polonica 19: 353-7.
"These findings indicate that HF in addition to being a mutagenic agent is also able to reduce
crossing over in certain chromosome segments."
SOURCE: Mohamed AH. (1977). Cytogenetic effects of hydrogen fluoride gas on maize.
Fluoride 10: 157-164.
"while NaF can be a potent meiotic mutagen in the particular in vitro experimental situations
reported here, the variation of in vitro sensitivity between the mouse (which nevertheless
showed some oocyte abnormality when tested in vivo) and the higher forms (cow and ewe)
would suggest an assessment of abnormal progeny from the latter species for chromosomal
abnormalities in NaF-contaminated areas, as a reasonable next step for ascertaining the
probability of the mutagenicity of this compound."
SOURCE: Jagiello G, Lin JS. (1974). Sodium fluoride as potential mutagen in mammalian
eggs. Archives of Environmental Health 29:230-5.
"Two strains of Drosophila melanogaster were treated with sub-lethal levels of gaseous
hydrogen fluoride for six weeks. Egg samples were collected at various times for hatchability
determinations. Adults reared from these samples were evaluated for fecundity and fertility.
Treatment with HF caused a marked reduction in hatchability and fecundity in the more
sensitive strain. Male fertility was depressed but female fertility remained stable over the test
period. The reduction of these parameters in the offspring of populations subjected to low
levels of atmospheric HF contamination for prolonged periods suggests that HF causes
genetic damage."
SOURCE: Gerdes RA, et al. (1971). The effects of atmospheric hydrogen fluoride upon
Drosophila melanogaster. II. Fecundity, hatchability and fertility. Atmospheric Environment
5:117-122.
"Genetic differences were observed in the response of the progeny of treated flies. The
maintenance of a population at sub-lethal concentrations of HF revealed an apparent
accumulation of of physiological abberations resuting in sterility in the treated flies. Results
indicate that treatment increased the incidence of genetic abberations as measured by at
least two parameters."
SOURCE: Gerdes RA. (1971). The influence of atmospheric hydrogen fluoride on the
frequency of sex-linked recessive lethals and sterility in Drosophila Melanogaster. Fluoride 4:
25-29.
"Maize seedlings of the genotype A1A2C1Wx were fumigated in growth chambers with
hydrogen fluoride (HF) at a concentration of about 3 ug/m3. The experiment was run for 10
days, with the first group of treated plants removed from the chambers after 4 days and then
at intervals of 2 days. Microsporocyte smears from the treated plants revealed chromosomal
aberations that included asynaptic regions, translocations, inversions, and bridges plus
fragments or fragments by themselves. It is believed that these abnormalities were due to the
physiological effect of HF causing the chromosomes to become sticky and/or to the
occurrence of chromatid breakage followed by reunion to form structural changes. These
findings indicate that HF is a mutagenic agent."
SOURCE: Mohamed AH. (1970). Chromosomal changes in maize induced by hydrogen
fluoride gas. Canadian Journal of Genetics and Cytology 12: 614-620.
"Studies on the effects of HF on meiotic chromosomes of tomatoes indicated a trend toward a
higher frequency of chromosomal aberrations with an increase in the fumigation period. It was
indicated that HF was capable of inducing paracentric inversions with the possibility of the
induction of deficiencies, duplications or even translocations. The progeny obtained from the
treated plants produced a number of abnormal phenotypes, the same as, or similar to, known
mutations. Further studies in maize microsporocytes for plants treated with HF confirmed the
cytological results obtained in tomatoes with clear evidence of the occurrence of inversions,
translocations and deficiencies. These results suggest that HF seems to affect primarily the
DNA molecule by blocking its replication, probably through its action on the enzymatic
system."
SOURCE: Mohamed AH. (1969). Cytogenetic effects of hydrogen fluoride on plants. Fluoride
2: 76-84.
"From the results, it is clear that NaF, not being mutagenic by itselft, interacts with the
mechanism of mutation induction by X-irradiation in fully mature spermatozoa. In fact, the
enhancing effect has been observed in 21 out of 23 experiments where pre-treatment with
NaF was compared to that with saline."
SOURCE: Mukerjee RN, Sobels FH. (1968). The effect of sodium fluoride and idoacetamide
on mutation induction by X-irradiation in mature spermatozoa of drosophila. Mutation
Research 6: 217- 25.
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