Fluoride Action Network

Fluoride’s Mutagenicity: In vitro Studies

Fluoride Action Network | by Michael Connett | Updated April 2015

According to the National Toxicology Program, “the preponderance of evidence” from laboratory “in vitro” studies indicate that fluoride is a mutagenic compound. Many substances which are mutagens, are also carcinogens (i.e. they can cause cancer). As is typical for in vitro studies, the concentrations of fluoride that have generally been tested are far higher (millimolar levels) than the concentrations found in human blood (micromolar levels). Some studies, however, have found effects at micromolar concentrations. In Khalil (1995), the authors found a statistically significant mutagenic effect at a concentration of just 1 micromole (19 parts per billion). This is the average blood fluoride concentration among individuals living in fluoridated communities. More recent research has found effects at 24 uM (Zhang 2009) and 34 uM (Tiwari & Rao 2010).

The relevance of the in vitro findings are further amplified by the fact that there are certain “microenvironments” in the body, such as the bones, oral cavity, kidney, bladder, and pineal gland, where the cells can be exposed to fluoride levels orders of magnitude greater than the fluoride levels found in the blood. Bones, for example, regularly accumulate 1,000 to 4,000 parts per million fluoride. Since bone mineral is regularly broken down by osteoclasts as part of the bone remodeling process, the fluoride sequestered in bones may be periodically released, exposing bone cells to sharp spikes in fluoride levels. This might help explain why fluoride has been associated, in both human and animal studies, with osteosarcoma (bone cancer). One in vitro study, for example, found that 10 to 19 ppm fluoride caused mutagenic effects in bone cells after 24 to 48 hours of exposure. (Mihashi 1996). According to the authors:

“Significant increases in the frequencies of chromosome aberrations were induced in a dose- and treatment time-dependent fashion when NaF was administered to [rat vertebral bone] cells at 0.5 and 1.0 mM [=9.5 to 19 ppm] 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(1):7-13.

Of further interest is the fact that cells from humans and apes have been found to be more susceptible to fluoride-induced genetic damage than rodent cells. (Kishi 1993). Accordingly, chromosome breaks occurred in human and ape cells at fluoride concentrations (19 to 114 ppm) that had no effects on rodent cells.

Finally, a number of recent “in vivo” studies, including studies of humans exposed to high levels of fluoride, have also found increased levels of genetic damage. Although the in vivo research is still limited, the weight of evidence from the in vitro and in vivo studies strongly indicate that fluoride is a mutagen, a finding that has significant implications with respect to fluoride’s capacity to induce or promote cancer.

reviews of In-Vitro research on fluoride’s mutagenicity:

“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. (There is also an abbreviated report)

“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 Studies:

“Our study has supported the role of As [arsenic] and F [fluoride] as potent genotoxic agents, since in vitro exposure of both caused increased chromosomal anomalies along with primary DNA damage, in human peripheral blood cultures.”
SOURCE: Tiwari H, Rao MV. (2010). Curcumin supplementation protects from genotoxic effects of arsenic and fluoride. Food & Chemical Toxicology 48(5):1234-8.

“In order to analyze potential carcinogenic and genotoxic responses caused by exposure to pollutants existing in environment, a screening method has been established in our laboratory that uses a stably transfected HepG2 cell lines containing gadd153 promoter regions which drive a luciferase reporter gene. Activation of the exogenous gadd153 promoter was quantified using the luciferase activity following drug exposure. Twenty four agents were used to evaluate this screening assay. We selected the agents, ranging from DNA alkylating agents, oxidative agent, radiation, DNAcross-linking agent, nongenotoxic carcinogens, precarcinogenic agents, which included cadmium chloride, chromium trichloride, mercuric chloride, lead nitrate, dichloro-diphenyl-trichloroethane, deltamethrin, biphenylamine, 2-aminofluorene, benzo[a]pyrene, 2,3,7,8,-tetracblorodibenzo-p-dioxin, diethyl-stilbestrol, carbon tetrachloride, mitomycin C, hydroxycamptothecin, UV, sodium fluoride, acrylamide, hydrogen peroxide. In addition, two complex genotoxic agents (water samples) existing in the environment were selected. The results showed that all 20 tested known carcinogenic and genotoxic agents were able to induce gadd153-Luc expression at a sublethal dose. In contrast, four tested non-carcinogens, included 4-acetylaminofluorene, pyrene, benzylpenicillin sodium and vitamin C, were unable to induce gadd153-Luc expression. In conclusion, this reportersystem can facilitate in vitro screening for potential carcinogens. Therefore, the gadd153-Luc test system we have developed appears to be a useful and complementary system to existing genotoxic and mutagenic tests.”
SOURCE: Zhang R, et al. (2009). A stable and sensitive testing system for potential carcinogens based on DNA damage-induced gene expression in human HepG2 cell. Toxicology In Vitro. 23(1):158-65.

“In this study we concluded that NaF, in 5 and 10 lg/ml NaF concentrations cause genotoxic alterations. So genotoxic, mutagenic and teratogenic effects of NaF need to be carefully screened and evaluated together with other long-term effects using in vitro and in vivo animal test models.”
SOURCE: Erciyas K, Sarikaya R. (2009). Genotoxic evaluation of sodium fluoride in the Somatic Mutation and Recombination Test (SMART). Food & Chemical Toxicology 47(11):2860-2.

“Some recent studies have suggested that DNA damage may be a potential neurotoxic mechanism of fluoride. The tail length, as measured by an ocular micrometer, is increased in fluoride-treated human embryonic hepatocytes in a previous study carried out to investigate the geneotic effect of fluoride (Wang et al., 2004). In the present study, we performed OTM and percentage of DNA in the tail as indices of DNA damage. OTM, multiplication of the tail length and percentage of DNA in the tail, objectively and sensitively reflects the effect of fluoride on DNA damage. Our findings showed that fluoride-induced DNA damage and OTM was more a sensitive measure than percentage of DNA in the tail. The correlation analysis showed a positive correlation between ROS formation and OTM level (r2=0.583, P < 0.05), which indicated that ROS might play an important role in the course of DNA damage.”
SOURCE: Zhang M, et al. (2008). Effects of fluoride on DNA damage, S-phase cell-cycle arrest and the expression of NF-kappaB in primary cultured rat hippocampal neurons. Toxicology Letters 179(1):1-5.

“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, considering 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 dose- and 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.

“Conflicting evidence has been reported concerning the mutagenicity of sodium fluoride (NaF), especially clastogenicity at concentrations of more than 1 mM. NaF is known to induce chromosome aberrations at these concentrations in human cells, but not in most rodent cells. We considered that such species-specific difference in chromosomal sensitivity would be derived from the phylogenetic distance between rodents and man. To clarify the role of interspecies differences, we investigated the chromosomal sensitivity to NaF in cell lines from various primates, which diverged into many species, including rodent-like prosimians and human-like great apes. The results showed that the clastogenicity of NaF was limited to human and 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(2): 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(1): 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 time-dependent 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(1): 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(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 effects of sodium fluoride and idoacetamide on mutation induction by X-irradiation in mature spermatozoa of drosophila. Mutation Research 6(2): 217- 25.