Clastogenic Cytotoxic Fetotoxic Genotoxic or Mutagenic
Sodium fluoride

CAS No. 7681-49-4

Return to Index Page
Return to Adverse Effects

Clastogenic = A clastogen is an agent that can cause one of two types of structural changes. A clastogen can cause breaks in chromosomes that result in the gain, loss, or rearrangements of chromosomal segments. A clastogen can also cause sister chromatid exchanges, which are "homologous chromatid strand interchanges and reunions [that occur] during DNA replication" (Thilly & Call, 1986, p. 181) -

Cytotoxic = of or relating to substances that are toxic to cells. Cell-killing.

Fetotoxic = Toxic to the fetus.

Genotoxic = Describes a poisonous substance which harms an organism by damaging its DNA.

Mutagenic =  capable of inducing mutation (used mainly of extracellular factors such as X-rays or chemical pollution)

Sister chromatid exchange (SCE) is a sophisticated cytomolecular technique that is commonly applied in a search for clastogenicity or genotoxicity. A clastogen is any environmental agent that causes damage to genetic material and may include carcinogens. An SCE analysis will tell us whether the chromosomes and thus DNA of a particular interest group has undergone some genetic damage compared to a control group.

Each chromosome comprises two sister chromatids which are genetically identical. In the SCE technique, one sister chromatid is stained dark and the other one pale. In a normal healthy person it is not unusual for the sister chromatids of one chromosome to break and swap pieces with each other (see Figure below). This is called sister chromatid exchange (SCE) and providing the number of SCEs do not go beyond a certain threshold, this is not considered to be harmful. Many studies have shown, however, that any increase in frequency of SCEs beyond the threshold indicates that something in that persons existence is or has caused genetic damage, which can lead to ill health. Many environmental agents, at home or at work, can increase the number of SCEs, for example, UV light, X-rays, nicotine and alcohol , to name a very limited few.


• Note: The following is a limited selection of abstracts from 1994 to present.
• Due to length, we present this as a separate section
• Click here to return to the same section for fluorine & organofluorine pesticides.
• When time allows more information will be added.

Anticancer Res. 2003. Sep-Oct;23(5A):3719-26.

Effect of antioxidants, oxidants, metals and saliva on cytotoxicity induction by sodium fluoride.

Tokunaga T, Morshed SR, Otsuki S, Takayama F, Satoh T, Hashimoto K, Yasui T, Ogawa S, Kanegae H, Yokote Y, Akahane K, Kashimata M, Satoh K, Sakagami H.

Department of Dental Pharmacology, Meikai University School of Dentistry, Sakado, Saitama, Japan.

have recently found that millimolar concentrations of sodium fluoride (NaF) induced apoptotic cell death, characterized by caspase activation and DNA fragmentation, in tumor cell lines. This finding paved the way to investigating the interaction between NaF and the oral environment. As an initial step, we investigated redox compounds, metals and saliva, which may modify the cytotoxic activity of NaF against a human oral squamous cell carcinoma cell line (HSC-2). The minimum exposure time to NaF required for cytotoxicity induction was 8 hours. Noncytotoxic concentrations of antioxidants (sodium ascorbate, gallic acid, epigallocatechin gallate, chlorogenic acid, curcumin, superoxide dismutase, catalase), oxidants (hydrogen peroxide, sodium hypochlorite), metals (CuCl, CuCl2, FeCl2, FeCl3, CoCl2) or saliva neither protected against, nor enhanced the cytotoxic activity of NaF. Cytotoxic concentrations of these compounds produced somewhat additive, but not synergistic, effects on the cytotoxicity of NaF. ESR analysis demonstrated that NaF did not apparently change the radical intensity of sodium ascorbate and gallic acid, measured under alkaline conditions. During the cell death induction in human promyelocytic leukemia HL-60 cells by NaF, the consumption of glucose rapidly declined, followed by a decline in the consumption of major amino acids. The present study suggests that the cytotoxic activity of NaF is not regulated by the redox mechanism, but rather linked to the rapid decline in glucose consumption at early stage.

PMID: 14666669 [PubMed - in process]

Zhonghua Yu Fang Yi Xue Za Zhi. 2002 Jul;36(4):222-4.

[Studies on DNA damage and apoptosis in rat brain induced by fluoride]

[Article in Chinese]

Chen J, Chen X, Yang K, Xia T, Xie H.

Department of Environmental Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, China.

OBJECTIVE: To explore the DNA damage effects and apoptosis in brain cells of rats induced by sodium fluoride.
METHODS: SD rats were divided into two groups, i.e. control group and fluoride treated group, which were injected intraperitoneally with distilled water and sodium fluoride (20 respectively. On the hand, 5 mmol/L NaF were used in in vitro study. Single Cell Gel Electrophosis (SCGE or Comet Assay) was utilized to measured DNA damage and apoptosis was detected by the TUNEL method and Flow Cytometry (FCM).
RESULTS: The DNA damage in pallium neurons in rats of the fluoride group was much more serious compared with those of the control group, with the Ridit value being 0.351 and 0.639 respectively (P < 0.01) in vivo, and 0.384 4 and 0.650 1 respectively (P < 0.01) in vitro. TUNEL positive cells were found in pallium, hippocampus and cerebellar granule cells in rats of fluoride group, whereas those in the control group were rare. It was demonstrated by FCM results that the percentages of apoptotic cells both in pallium and hippocampus were significantly higher (P < 0.01) in rats of fluoride group (27.12 +/- 3.08, 34.97 +/- 5.46) than those in control group (4.63 +/- 0.98, 5.35 +/- 0.79), (P < 0.01).
CONCLUSION: Sodium fluoride could induce DNA damage and apoptosis in rats brain.

PMID: 12411198 [PubMed - indexed for MEDLINE]

J Epidemiol 2001 Jul;11(4):170-9.

Regression analysis of cancer incidence rates and water fluoride in the U.S.A. based on IACR/IARC (WHO) data (1978-1992). International Agency for Research on Cancer

Takahashi K, Akiniwa K, Narita K.

Age-specific and age-standardized rates (ASR) of registered cancers for nine communities in the U.S.A. (21.8 million inhabitants, mainly white) were obtained from IARC data (1978-82, 1983-87, 1988-92). The percentage of people supplied with "optimally" fluoridated drinking water (FD) obtained from the Fluoridation Census 1985, U.S.A. were used for regression analysis of incidence rates of cancers at thirty six sites (ICD-WHO, 1957). About two-thirds of sites of the body (ICD) were associated positively with FD, but negative associations were noted for lip cancer, melanoma of the skin, and cancers of the prostate and thyroid gland. In digestive organs the stomach showed only limited and small in
testine no significant link. However, cancers of the oral cavity and pharynx, colon and rectum, hepato-biliary and urinary organs were positively associated with FD. This was also the case for bone cancers in male, in line with results of rat experiments. Brain tumors and T-cell system Hodgkin's disease, Non-Hodgkin lymphoma, multiple myeloma, melanoma of the skin and monocytic leukaemia were also correlated with FD. Of the 36 sites, 23 were positively significant (63.9%), 9 not significant (25.0%) and 4 negatively significant (11.1%). This may indicate a complexity of mechanisms of action of fluoride in the body, especially in view of the coexising positive and negative correlations with the fluoridation index. The likelihood of fluoride acting as a genetic cause of cancer requires consideration.

PMID: 11512573 [PubMed - indexed for MEDLINE]

Full report available at:

Fluoride 2000; 33(4):154-158

Sister chromatid exchange frequency and chromosome aberrations in residents of fluoride endemic regions of south Gujarat

Sajayan Joseph, PK Gadhia (a)

(a) For Correspondence: Department of Biosciences, South Gujarat University Surat 395 007, Gujarat, India. E-mail:

SUMMARY: Peripheral blood lymphocytes of residents of three villages and one nearby township in South Gujarat with fluoride concentrations in the drinking water of 1.56 - 3.46 and 0.6 - 0.8 ppm, respectively, were examined for their frequency of sister chromatid exchanges (SCE) and chromosome aberrations. The rates of SCEs and chromosome aberrations in persons living in one of the endemic villages were significantly higher than in the others, and their lymphocytes were more susceptible to the clastogen Mitomycin-C.

Chinese Journal of Endemiology 2000; 19(5):340-1.

The effects of high fluoride on micronucleus rate in humans and mice

  • As cited and abstracted in Fluoride 2001; 34(1):80

Li J, Zhou H-L, Yang Q, et al.

Objective: The human body and the mice were regarded as suitable subjects to study the effects of high-fluoride on micronucleus rate in mammalian animals.

Methods: In a test on the human body, the micronucleus rate of 51 adults from a high-fluoride area was compared with the micronucleus rate of 24 adults from a low-fluoride area. In a test on mice, the experimental group drank fluoride water, and the control group drank tap water. Differences were examined for significance by the chi-squared test.

Results: The micronucleus rate of adults from the high-fluoride area was higher than that of adults in the low-fluoride area, and the difference was sig-nificant (P<0.05). The micronucleus rate of mice drinking high-fluoride water was higher than that of the control group, and the difference was also signifi-cant (P<0.05).

Conclusions: High-fluoride intake increases the miconucleus rate in mammals, and can damage chromosomes. Fluoride may therefore be mutagenic.

Toxicol In Vitro 2000 Apr;14(2):185-92

Morphological transformation and effect on gap junction intercellular communication in Syrian hamster embryo cells as screening tests for carcinogens devoid of mutagenic activity.

Rivedal E, Mikalsen SO, Sanner T.

Department of Environmental and Occupational Cancer, Institute for Cancer Research, The Norwegian Radium Hospital, N-0310, Oslo, Norway.

A large fraction of chemicals observed to cause cancer in experimental animals is devoid of mutagenic activity.
It is therefore of importance to develop methods that can be used to detect and study environmental carcinogenic agents that do not interact directly with DNA. Previous studies have indicated that induction of in vitro cell transformation and inhibition of gap junction intercellular communication are endpoints that could be useful for the detection of non-genotoxic carcinogens. 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 cells. The substances were selected on the basis of being proven or suspected non-genotoxic carcinogens, and thus difficult to detect in short-term tests. The data show that nine of the 13 compounds induced morphological transformation, and seven of the 13 inhibited intercellular communication in hamster embryo cells. Taken together, 12 of the 13 substances either induced transformation or caused inhibition of communication. The data suggest that the combined use of morphological transformation and gap junction intercellular communication in Syrian hamster embryo cells may be beneficial when screening for non-genotoxic carcinogens.

PMID: 10793297 [PubMed - indexed for MEDLINE]

Fluoride 1998 May;31(2):61-73.

• As cited on Toxnet DART.

Fluoride-linked Down syndrome births and their estimated occurrence due to water fluoridation.

Takahashi K

Department of Internal Medicine and Biostatistics, Tokyo University Medical School, Tokyo, Japan. Source:

Abstract: Down syndrome (DS) birth rates (BR) as a function of maternal age exhibit a relatively flat linear regression line for younger mothers and a fairly steep one for older mothers with the second line intersecting the first line a little above maternal age 30. Consequently, overall DS-BR for all maternal ages are not a very reliable parameter for detecting environmental influences, since they may be strongly affected by the ratio of the number of younger to older mothers. For this reason, data for mothers under age 30 were selected to detect an association between water fluoridation and DS for which the lower maternal age regression would be a much smaller contributing factor. The early research of I Rapaport indicating a link between fluoride in drinking water and Down syndrome was followed by studies claiming there was no such association. Application of sound methodology to the data in those later investigations shows that none of the criticisms against Rapaport's work are valid. For example, in the data of J D Erickson on maternal age-specific DS births in Metropolitan Atlanta, Georgia, when the three youngest maternal age subgroups are reasonably combined into single groups for areas with and without water fluoridation, a highly significant association (P less than 0.005) is revealed between fluoridated water and DS births. It also appears that the dose-response line (DRL) or DS-BR for daily fluoride intake may have no allowable level that does not induce fluoride-linked DS births. Therefore fluoride may be one of the major causes of DS other than aging of mothers. The number of excess DS births due to water fluoridation is estimated to be several thousand cases annually throughout the world.

Arch Toxicol 1996;70(3-4):249-51

Apoptotic cell death following exposure to fluoride in rat alveolar macrophages.

Hirano S, Ando M.

Regional Environment Division, National Institute for Environmental Studies, Ibaraki, Japan.

Since inhaled fluoride is implicated in the acute respiratory failure, cytotoxic effects of fluoride on alveolar macrophages, primary target cells of inhaled toxicants, were investigated. The LC50 of sodium fluoride was estimated to be 0.41 mM, while 1 mM sodium chloride, bromide and iodide had virtually no effects on the viability of alveolar macrophages. Photomicroscopic observation revealed that nuclei of the fluoride-exposed alveolar macrophages were fragmented. The ladder formation was observed when DNA isolated from fluoride-exposed alveolar macrophages was electrophoresed in agarose gel. These results suggest that cytotoxicity of fluoride is associated with apoptosis in rat alveolar macrophages.

PMID: 8825685 [PubMed - indexed for MEDLINE]

Mutat Res 1996 May;368(1):7-13

Clastogenic activity of sodium fluoride to rat vertebral body-derived cells in culture.

Mihashi M, Tsutsui T.

Department of Pharmacology, School of Dentistry at Tokyo, Nippon Dental University, Japan.

The US National Toxicology Program has shown equivocal evidence of carcinogenic activity of sodium fluoride (NaF) in male F344/N rats based on the occurrence of five osteosarcomas in treated animals. In the study the osteosarcomas developed mainly in the rat vertebrae. To provide a possible mechanistic basis for the observed tumors, the genotoxic effects of NaF on the possible target organ of NaF carcinogenesis were examined. Rat vertebral body-derived (RVBd) cells were established from trabecular bone of vertebral bodies of a male F344/N rat 6 weeks of age and treated with NaF. RVBd cells in secondary culture exhibited a high level of alkaline phosphatase (ALP) activity when the cells at confluence were assayed by ALP staining. When the histochemical examination was performed on RVBd cell colonies, most of the colonies were stained positively for ALP. Confluent RVBd cells were responsive to 10(-8) M 1 alpha.25-dihydroxyvitamin D3 with a 7.7-fold increase in osteocalcin production over base line values. The von Kossa staining demonstrated that in the presence of 2 mM beta-glycerophosphate, RVBd cells that were allowed to grow past confluence for approximately 2 months formed mineralized nodules. When RVBd cells in tertiary culture were treated with NaF at 0.5-2.0 mM for 24-72 h, the growth and/or survival of the treated cells was reduced in a dose-dependent manner. Significant increases in the frequencies of chromosome aberrations were induced in a dose- and treatment time-dependent fashion when NaF was administered to RVBd 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.

PMID: 8637511 [PubMed - indexed for MEDLINE]

Mutat Res 1995 May;343(1):67-74

Chromosome aberrations in cultured rat bone marrow cells treated with inorganic fluorides.

Khalil AM.

Department of Biological Sciences, Yarmouk University, Irbid, Jordan.

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).

PMID: 7753108 [PubMed - indexed for MEDLINE]

Fluoride 1995; 28(4):193-200

Changes of the human erythrocyte membrane protein SH binding site property with exposure to fluoride and three strong mutagens

Wang YY, Li XJ, Xin WJ

Beijing Municipal Research Institute of Environemental Protection, Fu Wai Avenue, Beijing 100037, China

Summary: The effects of three strong mutagens (potassium bichromate, mitomycin C, and colchicine) and fluoride on the human erythrocyte membrane protein SH binding site property have been studied by using the maleimide nitroxide-ESR technique. The results indicate that in singular and combined treatments with mutagens, the ratio of weakly to strongly immobilized component protein is altered. It is possible that the inhibition in the cytogenetic response is induced by the interaction of fluoride with the other chemicals. There is a dose and temperature dependence of both the singular and the combined action of the mutagen on the membrane protein.

Fluoride 1995; 28(3):125-127

Micronucleus and sister chromatid exchange frequency in endemic fluorosis

DQ Wu and Y Wu

Inner Mongolia Sanitary and Anti-epeidemic Station, Hohhot 010020, China

Summary: Inhabitants of the Hohhot Region in Inner Mongolia who drink high-fluoride (4-15 mg/L) water were compared for their micronucleus (MN) rate and sister chromatid exchange (SCE) frequency in their peripheral blood lymphocytes. In persons with fluorosis as well as those considered "healthy", the MN rate and SCE frequency were significantly higher (t test) than in a neighbouring control group drinking low-fluoride water.

Fluoride 1994; 27(2):76-80.

Preliminary observations on alterations in rabbit ovary DNA and RNA content in experimental fluorosis

A Shashi

Abstract: Summary. Forty-eight albino rabbits were administered fluorde as sodium fluoride subcutaneously in daily doses of 5, 10, 20, and 50 mg/kg body weight for three and a half months. Twelve controls received 1 cc distilled water/kg body weight/day for the same period. Ovaries from the control and fluoridated animals were analysed for DNA and RNA content. The experimental animals showed significant depletion (P < 0.001) of ovarian DNA and RNA compared to the controls. The data indicate that fluoride inhibits nucleic acid synthesis in the ovary. The findings also suggest that fluoride acts directly on DNA to produce structural changes in ovarian tissue which were subsequently confirmed by histopathological examination of control and treated animals. Further studies are desirable to define the possible role of fluoride in causing deleterious effects on reproduction such as delayed oestrus, repeated failure to conceive, and lowered viability detected earlier in experimental animals.

Fluoride Action Network | Pesticide Project | 315-379-9200 |