Fooling with Numbers: The Anti-Fluoridation Campaign

What would you say if someone told you that you are putting your family at risk of almost certain death because a known highly toxic poison comes out of the exhaust pipe of your car, and that riding in the car will reduce children’s intelligence because there is lead in the car battery?

You’d say the concentration is very low, and the evidence of deadly toxicity comes from studies with much higher concentrations, so it is not a significant risk, even though granted, carbon monoxide and lead are toxic.

Suppose someone argued against gardening by saying that by eating your garden vegetables you are putting cadmium, arsenic, and lead into your body, and that study after study has shown that these heavy metals cause severe mental health disease and eventual death. You would question the amounts, even though these are indeed found in garden soil and in your body. Finding that the rates you are getting from home-grown veggies are well below safety levels, you would not worry. The anti-fluoridation campaign presents interpretations that seem like the same approach, evidence of harm at excessively high levels held up as evidence of risk at very low levels.

Articles and posts with names like “Fluoride may be your next contraceptive?” and websites on “Fluoride’s Effect on Male Reproductive System” have been turning up in the news, and have been uncritically reposted in anti-fluoridation campaign internet sites and newsletters. One article (foodconsumer.org) that appeared in my news alert yesterday claims “A new study suggests that exposure to all currently used fluoride chemicals including sodium fluoride, one of the chemicals that are commonly used for drinking water fluoridation, may make men infertile or reduce their fertility”, and links to the following research article:

Rice JR, Boyd WA, Chandra D, Smith MV, Den Besten PK, Freedman JH. 2013. Comparison of the toxicity of fluoridation compounds in the nematode C. elegans. Environ Toxicol Chem. [Epub ahead of print; available in Pubmed]

Abstract: …The toxicity of these fluorides on the growth, feeding, and reproduction in the alternative toxicological testing organism Caenorhabditis elegans [nematode] was examined. Exposure to these compounds produced classic concentration-response toxicity profiles. Although the effects of the fluoride compounds varied among the 3 biological end-points, no differences were found between the 3 compounds, relative to the fluoride ion concentration, in any of the assays. This suggests that silicofluorides have similar toxicity to NaF.

Although the research seems useful, it is not convincing evidence that fluoridation “may make men infertile”. The anti-fluoridation commenters then explain that “It was found that exposure to all fluoride chemicals produced classic dose-responsive toxicity.”

Most things have some sort of dose-response effect, and possibly even toxicity at high doses. This is not unusual. This just means that low quantities of most things (including salt, soap, smoke, essential oils, wine, etc.) have no detectable effect, and as the dosage increases so does the response, even eventually becoming harmful. Paracelsus (1493-1541), founder of toxicology as a field of study, is famous for his observation that the “dose makes the poison” (actually, “Alle Dinge sind Gift und nichts ist ohne Gift; allein die Dosis macht, dass ein Ding kein Gift ist.”, “All things are poison and nothing is without poison, only the dose makes a thing poison or not.”) Some toxic effects may seem surprising. For example, a study conducted at the University of Utah and published last month found that when mice ate a diet high in sugar (the news said 25% extra sugar), female mice died at twice the normal rate and male mice were a quarter less likely to hold territory and reproduce.

The anti-fluoridation news continues the argument, then links to another study.

Lu Z, Wang S, Sun Z, Niu R, Wang J. 2013. In vivo influence of sodium fluoride on sperm chemotaxis in male mice. Arch Toxicol. 2013 Jul 24. [Epub ahead of print; in Pubmed]

Abstract: …260 healthy Kunming [China] male mice (8 weeks old) were randomly divided into four groups and exposed to 50, 100, 150 mg NaF/L in the drinking water for 8 weeks. At the end of the exposure, sperm chemotaxis was examined… In the 100 and 150 mg/L groups, Ca2+ concentration and AC content were notably lower than the control group. Compared with the control group, mRNA expression of CatSper1 in the 100 and 150 mg/L treatment groups was decreased significantly, and other genes showed no statistical difference. These data suggested that excessive fluoride did adversely affect sperm chemotaxis.

Did you get that? Exposure to 50 mg sodium fluoride per liter (which would contain 22.5 mg fluoride), which yields more than 32 times the rate of fluoride supplement that is used for fluoridation (0.7 mg fluoride per L), did not result in a detectable reduction in fertility. The researchers found a detectable effect on calcium levels and some gene expression at 100 mg NaF/L, which is 64 times the rate used in water fluoridated in water treatment programs such as in my city.

And yet, the anti-fluoride reader concludes the opposite. Not only is there no such harm at levels near what could be obtained from fluoridated water, it is a conservative result (meaning that if anything is probably even safer). Mice in the cages typically drink around 3 to 5 mL per day, or about 15 mL of water per 100 g body weight per day, which is around 3 times the rate of water use humans (official figures are 2.7 to 3.7 L per day). So, the claim that this result indicates a human health risk is on even shakier ground. Also, the 3 L or so a day that a person may drink is not all city water, so the actual consumption is probably lower.

Much of the basis for the claim of an effect on reproduction comes from articles collected and listed at the “Fluoride Action Network”: “Fluoride’s Effect on Male Reproductive System: Animal Studies“, and “Fluoride’s Effect on Male Reproductive System – Human Studies“.

These are a selective collection of science articles that they say supports the conclusion of “associations between fluoride exposure and damage to the male reproductive system”. Their list is included below with my comments. None of these articles have any data or inference that indicates negative effects at the levels of fluoridation that result from supplementation of drinking water for the purpose of dental health (currently 0.7 mg/L). Most of the studies appear to concern excessive levels found in areas of naturally high geological-source fluoride, and that is a worthy, but unrelated, area of research.

It would be very interesting to see results simply comparing non-fluoridation with fluoridation, but as I said where the low levels are included in these studies, they are used as controls for comparison – they are the “safe” subset. Even non-fluoridated sites would have some level of fluoride. Fluoridation in Canada is typically adjusted to 0.7 mg/L, and non-fluoridation water sources would have typically 0.05 to 0.2 mg/L (WHO, 1996, Fluoride in Drinking-water, Background document for development of WHO, Guidelines for Drinking-water Quality, WHO/SDE/WSH/03.04/96). This is a good position to be in, geographically and hydrologically, because it means water treatment can raise fluoride levels to the optimum zone that provides reduced cavities in children, without being near levels that could darken teeth or accumulate in bones, a rare condition usually restricted to areas of high natural fluoride. Other effects occur at levels that are unheard-of in Canada, in the same way that we do not have many natural highly toxic levels of other substances.

The selected set of literature posted on the news link that has been going around does not contain all of the research papers on fluoride and health; there are hundreds more. A broader search of research results shows no negative effects (cancer, bone disease, heart disease, effect on mental functions, etc.) from fluoride at levels used in managed fluoridation. If such a result could be shown, it would be taken very seriously by scientists and city managers. Evidence and data are all that matter in such studies. Unfortunately, some cities have been convinced by a vocal group of activists, for reasons other than what could be fairly called evidence.

Here is an example:

An L, et al. 2004. Combined effects of vitamin E and fluoride on reproductive function in male mice. Chinese Journal of Control of Endemic Disease.

Conclusions: 200 or 300 mg/L sodium fluoride in drinking water can significantly decrease sperm count and mobility of male mice. Vitamin E was given while administrated with NaF, but effects on mice were not improved.

Fluoridated water has a managed target level of 0.7 mg/L. 200 mg of NaF would provide about 90 mg of fluoride.

Is research in this area worth doing (meaning actually doing tests, rather than simply talking or reading about it)? Certainly, it is. Sodium fluoride is mildly toxic, and in concentrated form it should be handled with care. In relative toxicity, it is next to nicotine and the phenolic amide capsaicin (the active ingredient in chili pepper spice; does this mean that hot food is “the most toxic substance”, as some anti-fluoridation activists say about fluoride?). The LD50, a standardized estimate of the dose that would result in a 50% chance of mortality if ingested in a short time, is 32 to 64 mg fluoride per kg body weight. It would not be possible to ingest this much from drinking water treated at 0.7 mg/L, but it could happen in an industrial accident, for example, as is true with any mineral. For a 70-kg adult, 32 to 64 mg/kg would mean drinking 3000 to 6000 liters of water in a day. The lethal dose for water is generally considered to be 20 L per day.

The Appendices below includes the articles mentioned, and my comments.

Appendices

Human studies cited by fluoridealert.org

Hao P, Ma X, Cheng X, Ba Y, Zhu J, Cui L. 2010. Effect of fluoride on human hypothalamus-hypophysis-testis axis hormones. [in Chinese]. Wei Sheng Yan Jiu. 39(1):53-5.

OBJECTIVE: To study of endocrine disturbing effect of fluoride on human hypothalamus-hypophysis-testis axis hormones. METHODS: Sunying County, Kaifeng City was selected as polluted district which the fluoride in drinking water was 3.89 mg/L, and Shenlilou county was selected as control district which the fluoride was less than 1.0 mg/L. 150 individual lived there more than 5 years were selected randomly.

This was a study of polluted water in which the natural fluoride concentration was too high. Their safe “control” for comparison is higher than the fluoridation level applied in water treatment here. It has nothing to do with water treatment to supplement low levels of fluoride to the higher but still low level of 0.7 mg/L for dental health of children.

Ortiz-Pérez D, Rodríguez-Martínez M, Martínez F, Borja-Aburto VH, Castelo J, Grimaldo JI, de la Cruz E, Carrizales L, Díaz-Barriga F. 2003. Fluoride-induced disruption of reproductive hormones in men. Environmental Research 93:20-30.

Fluoride-induced reproductive effects have been reported in experimental models and in humans. However, these effects were found in heavily exposed scenarios. Therefore, in this work our objective was to study reproductive parameters in a population exposed to fluoride at doses of 3-27 mg/day (high-fluoride-exposed group-HFEG). Urinary fluoride levels, semen parameters, and reproductive hormones in serum (LH, FSH, estradiol, prolactin, inhibin-B, free and total testosterone) were measured. Results were compared with a group of individuals exposed to fluoride at lower doses: 2-13 mg/day (low-fluoride-exposed group-LFEG).

This was a study of polluted water in which the natural fluoride concentration was extremely high. Their safe “lower doses” for comparison were 2.8 to 18.5 times higher than the fluoridation level applied in water treatment here. This study has nothing to do with water treatment to supplement low levels of fluoride to the higher but still low level of 0.7 mg/L.

Chen P, et al. 1997. Effects of hyperfluoride on reproduction-endocrine system of male adults. Endemic Diseases Bulletin 12(2):57-58.

In order to explore the effects of excess fluoride on reproductive function of male adults, a research was conducted in 31 male adults from a hyperfluoride area and 26 subjects in normal area as control in present study.

This was a study of polluted water in which the natural fluoride concentration was greater than 4 mg/L, compared to one with <1.0 mg/L (the level here is 0.7 mg/L). The paper is widely cited by the anti-fluoridation campaigners, but it is not available. It has nothing to do with water treatment to supplement low levels to 0.7 mg/L.

Susheela AK, Jethanandani P. 1996. Circulating testosterone levels in skeletal fluorosis patients. Journal of Toxicology and Clinical Toxicology 34(2):183-9.

OBJECTIVE: The present study focuses on serum testosterone concentrations in patients with skeletal fluorosis, in order to assess the hormonal status in fluoride toxicity. METHODS: Serum testosterones were compared for patients afflicted with skeletal fluorosis (n = 30) and healthy males consuming water containing less than 1 ppm fluoride (Control 1, n = 26) and a second category of controls (Control 2, n = 16): individuals living in the same house as the patients and consuming same water as patients but not exhibiting clinical manifestations of skeletal fluorosis.

This was a study of people who actually had clear symptoms of a disease resulting from living in areas with excessively high natural levels. It has nothing to do with water treatment to supplement low levels of fluoride to 0.7 mg/L.

Michael M, et al. 1996. Investigations of soft tissue functions in fluorotic individuals. Fluoride 29:63-71.

Circulating levels of testosterone were decreased, but not significantly enough to indicate an effect on reproductive functions.

The paper relates some measurements from villages in areas of excessively high levels of natural fluoride from geological sources (the kind that would be controlled and reduced by water treatment). It does not seem to be available on-line, and does not have any relevance to fluoridation at low levels for dental caries prevention.

Freni SC. 1994. Exposure to high fluoride concentrations in drinking water is associated with decreased birth rates. Journal of Toxicology and Environmental Health 42:109-121.

A review of fluoride toxicity showed decreased fertility in most animal species studied. The current study was to see whether fluoride would also affect human birth rates. A U.S. database of drinking water systems was used to identify index counties with water systems reporting fluoride levels of at least 3 ppm.

This study compared regions with fluoride above 3 mg/L, with those below, and concluded that there could be an effect at the higher natural levels, but apparently the lower ones like used in water treatment do not have any effect. This study has nothing to do with water treatment to supplement low levels of fluoride to 0.7 mg/L.

Liu H, et al. 1988. Analysis of the effect of fluoride on male infertility in regions with reported high level of fluoride (endemic fluorosis). Journal of the Medical Institute of Suzhou 8(4):297-99.cite

A survey was made on fluoride contents in drinking water, mattled enamel, bone fluorosis, fluoride concentration in human spermatic fluid, and male infertility in fluoric area in Xinjiang Province. Is suggested that the fluorosis may be associated with human male infertility in fluoric areas.

The paper is not available, but it concerns excessively high natural levels, the kind that would be controlled and reduced by water treatment. This study has nothing to do with water treatment to supplement low levels of fluoride.

Neelam, K, et al. 1987. Incidence of prevalence of infertility among married male members of endemic fluorosis district of Andhra Pradesh. In: Abstract Proc Conf Int Soc for Fluoride Res. Nyon, Switzerland.

Married men in an endemic fluorosis area in India (with water fluoride levels ranging up to 38.5 ppm) are found to have higher rates of infertility than men from a non-fluorosis area.

This presentation apparently gave some results from a region that has extremely high natural levels and noted diseases, compared to safe levels. Our low level of 0.7 mg/L would be considered almost none, by comparison.

Chinoy NJ, Narayana MV. 1994. In vitro fluoride toxicity in human spermatozoa. Reprod Toxicol. 8(2):155-9 (citing Tarinsky AP. 1972). The influence of some industrial factors of aluminum industry on generative function of men. PhD Thesis, Sverdlovsk).

Preliminary studies in human subjects suffering from industrial fluorosis reported azoospermia and oligospermia, which may have been due to hypogonadism.

Not available on-line, but apparently a study of industrial toxicity at very high levels. No conclusions can be drawn about very low levels such as ours.

Tokar VI, Savchenko ON. 1977. Effect of inorganic fluorine compounds on the functional state of the pituitary-testis system. Probl Endokrinol (Mosk). 23(4):104-7.

The radioimmunological method was applied to the study of blood testosterone, LH, and FSH content in 41 men suffering from fluorosis, aged from 33 to 45 years. Nineteen men who had no contact with fluorine compounds served as control. In comparison with healthy individuals testosterone content proved to be decreased and FSH content elevated in patients with fluorosis. Blood LH content was increased only in those patients with fluorosis who had long contact with fluorine compounds (over 15 years). The changes in the blood hormone concentration were connected with disturbances of the hormonal, and, possibly, of the germinative function of the testes. The hypophysis proved to suffer less, and the changes of its function were apparently secondary in character.

This paper, in Russian, is not available on-line, but the abstract indicates that it is obviously a study of men , perhaps industrial workers or miners, with severe exposure and disease symptoms. It has nothing to do with water treatment to supplement low levels to the higher but low level of 0.7 mg/L.

Animal studies cited by fluoridealert.org

The animal studies cited below were generally conducted with very high rates, and never show any negative effects at the low levels use for supplementation in fluoridation for dental health purposes. Some of them were already listed and cited. There are many other studies available in journals and on-line, but this selection was chosen by fluoridealert.org. These papers are mainly from places like China and India, where extremely high levels of naturally occurring fluoride present a problem, and often must be reduced by water treatment.

My comments are reduced in this section, because it is the same case over and over: the work was conducted to see the effects at very high rates.

Kumar N, et al. 2012. To study the effect of vitamin D and E on sodium-fluoride-induced toxicity in reproductive functions of male rabbits. Toxicology International 19(2):182-87.

20 mg/kg body weight/day, for 30 days which they refer to as a “high dosage of fluoride”

Sun Z, et al. 2011. Fluoride-induced apoptosis and gene expression profiling in mice sperm in vivo. Arch Toxicol. 85(11):1441-52.

mice treated with 150 mg/l NaF for 49 days (very high)

Kumar N, et al. 2010. Effect of duration of fluoride exposure on the reproductive system in male rabbits. J Hum Reprod Sci. 3:148-52.

sodium fluoride (20 mg/kg body weight) for 30 days and Group III was fed on sodium fluoride (20 mg/kg body weight) for 60 days, very high

Wu PF, et al. 2010. Morphologic observation of mouse testicular tissue lesions induced by fluorine. Animal Husbandry and Feed Science.

A total of 20 Kunming mice at the age of 20 days were divided into four groups randomly.The mice in different group were respectively fed with water containing 0,50,100 and 150 mg/L sodium fluoride for 120 d.

Izquierdo-Vega JA, et al. 2010. NADPH oxidase participates in the oxidative damage caused by fluoride in rat spermatozoa. Protective role of a-tocopherol. J Appl Toxicol. 2010 Nov 19. doi: 10.1002/jat.1600.

Four experimental groups of maleWistar ratswere administered with deionizedwater, NaF, at a dose equivalent to 5 mg fluoride kg-1 per 24 h, NaF plus 20 mg kg-1 per 24 h a-tocopherol, or a-tocopherol alone for 60 days.

Sun Z, et al. 2010. Effects of sodium fluoride on hyperactivation and Ca2+ signaling pathway in sperm from mice: an in vivo study. Arch Toxicol. 84(5):353-61.

Adult male Kunming mice were administrated with 30, 70, and 150 mg NaF/l (corresponding to 2.84 +/- 0.29, 6.28 +/- 0.61, and 14.18 +/- 1.00 mg F/kg body weight per day) through drinking water for 49 days. The results showed that NaF reduced the sperm hyperactivated motility in a dose-dependent manner. Compared with the controls, intracellular Ca2+ concentration and CAMK2 protein were significantly decreased in mice treated with 70 and 150 mg NaF/l, while no effect on CALM was determined in all treatment groups. Furthermore, decreased sperm CatSper1 mRNA expression was also observed in response to middle and higher doses of NaF (70, 150 mg/l) with comparison to the control group, whereas no change in the mRNA expression of CatSper2 was detected in NaF administrated groups. Treatment with 30 mg NaF/l exhibited slight effects on the above indexes with no statistical difference. These findings indicated that exposure to 70 and 150 mg/l NaF for 49 days could result in low hyperactivation via alteration of Ca2+ signaling pathway involving CatSper1 in sperm from mice.

Dvoráková-Hortová K, et al. 2008. The influence of fluorides on mouse sperm capacitation. Anim Reprod Sci. 108(1-2):157-70.

Increasing infertility, due to pathological changes on sperm, has become a serious issue. Eco-toxicological effect of rising concentration of fluorides can be enhanced in the presence of aluminium ions by forming fluorometallic complexes, analogues of phosphate groups that interfere with the activity of G-proteins and P-type ATPases, which are part of several signalling pathways during sperm maturation. … The present paper reports the findings of 3-month oral toxicity in mice of fluorides at the concentrations 0, 1, 10, and 100ppm and their synergic action with aluminium at dose of 10ppm. There were no mortalities, clinical signs of discomfort or body weight loss during the experiment. The analysis revealed, for the concentrations of 10 and 100ppm, abnormalities of spermatogenesis and ability of epididymal spermatozoa to capacitate in vitro, as the result of decreased sperm head tyrosine phosphorylation and actin polymerization. The enhancing overload caused by fluorides represents a potential factor, having an impact on function of sperm, hence contributing to a growing infertility in the human population.

(ppm = mg per kg)

Izquierdo-Vega JA, et al. 2008. Decreased in vitro fertility in male rats exposed to fluoride-induced oxidative stress damage and mitochondrial transmembrane potential loss. Toxicol Appl Pharmacol. 230(3):352-7.

Fluorosis, caused by drinking water contamination with inorganic fluoride, is a public health problem in many areas around the world. The aim of the study was to evaluate the effect of environmentally relevant doses of fluoride on in vitro fertilization (IVF) capacity of spermatozoa

5 mg fluoride/kg body mass/24 h, or deionized water orally for 8 weeks. One would have to drink 225 liters of water to get this much.

Sharma JD, et al. 2008. Amelioration of fluoride toxicity in rats through vitamins (C, D) and calcium. Toxicology International 15:111-6.

The healthy, adult male rats (Rattus norvegicus) were treated with fluoride water (F.W.+5.8 ppm), F.W.+ ascorbic acid and F.W. + vitamins (C, D) and Ca+2 for 60 days. Fluoride water ingestion to rats for 60 days… The exogenous feeding of ascorbic acid and vitamin C, vitamin D and calcium along with fluoride water for 60 days caused recovery in all altered parameters studied including circulating level of testosterone, blood physiology, sperm function and fertility. The data suggest that ascorbic acid and vitamin C, vitamin D and Ca +2 treatment can play a prophylactic role to maintain normal physiology in fluoride toxicity.

Chen SJ, et al. 2008. Testis damage induced by chronic fluorosis and antagonism of taurine-zinc. Journal of Environment and Health.

Objective: To investigate the adverse effect of chronic fluorosis on the testicular structure of rats testis and the antagonism of taurine-zinc. Methods 30 male Wistar rats were randomly divided into 5 groups (6 in each) and treated with fluoride and taurine-zinc through drinking water: control, low fluorine (LF, 100 mg NaF/L), high fluorine (HF, 200 mg NaF/L), low fluorine plus Zn(LF+Zn), high fluorine plus Zn (HF+Zn). After 5 months of fluoride treated, the rats in LF+Zn and HF+Zn groups were given taurine-zinc (0.34 g/L) by added in the drinking water for another month. Six months later, the testicle structure in all groups was examined under the microscope. Results: In LF group, the loosened testicular gland and interstitial edema were seen. In HF group, primary spermatocyte became smaller and sperm head disappeared. However, in LF+Zn and HF+Zn groups there were no so significant damages, the changes were similar to normal testis. Conclusion: Chronic fluorosis can cause testis damage and taurine-zinc presents an obvious ameliorative effect in rats.

‘low’ 100 mg/L! High 200. Even the low is many times higher than could be encountered from managed fluoridation.

Reddy PS, et al. 2007. Suppression of male reproduction in rats after exposure to sodium fluoride during early stages of development. Naturwissenschaften. 2007 Jul;94(7):607-11.

Sodium fluoride (NaF), a widespread natural pollutant was given to sperm-positive female rats throughout gestation and lactation at a dose of 4.5 and 9.0 ppm via drinking water. The neonates were allowed to grow up to 90 days on tap water, and then sperm parameters, testicular steroidogenic marker enzyme activity levels, and circulatory hormone levels were studied. The sperm count, sperm motility, sperm coiling (hypoosmotic swelling test), and sperm viability were decreased in experimental rats when compared with controls. The activity levels of testicular steroidogenic marker enzymes (3beta hydroxysteroid dehydrogenase and 17beta hydroxysteroid dehydrogenase) were significantly decreased in experimental animals indicating decreased steroidogenesis. The serum testosterone, follicle stimulating hormone and luteinizing hormone levels were also significantly altered in experimental animals. Our data indicate that exposure to NaF during gestation and lactation affects male reproduction in adult rats by decreasing spermatogenesis and steroidogenesis.

A study of high doses only.

Gupta RS, et al. 2007. The toxic effects of sodium fluoride on the reproductive system of male rats. Toxicol Ind Health. 23(9):507-13.

The present study was undertaken to evaluate the effect of fluoride toxicity on the reproductive system of male rats. Sexually mature male Wistar rats were exposed to 2, 4, and 6 ppm sodium fluoride in their drinking water for 6 months ad libitum. Sperm motility and density in cauda epididymis were assessed. Biochemical and histological analysis were performed in reproductive organs. Fluoride treatment brought about a significant decrease in the weight of testis, epididymis, and ventral prostate. The sperm motility and density were significantly reduced. There was a marked reduction in the number of primary spermatocyte, secondary spermatocyte, and spermatids. The Sertoli cell counts and their cross sectional surface areas were significantly decreased. The Leydig cell nuclear area and the number of mature Leydig cells were also significantly decreased. The protein content of the testis and epididymis were significantly reduced. Fructose in the seminal vesicles and cholesterol in testes were increased significantly. In conclusion, sodium fluoride administrated in drinking water of 2, 4, and 6 ppm concentration for 6 months to male rats adversely affected their fertility and reproductive system.

I was not able to find the paper, and cannot find any information on how much they consumed or how the assessments were conducted.

Sarkar SD, et al. 2006. Management of fluoride induced testicular disorders by calcium and vitamin-E co-administration in the albino rat. Reprod Toxicol. 22(4):606-12.

Fluoride contamination of drinking water can disrupt male gametogenesis and steroidogenesis and induce testicular oxidative stress. Treatment of rats with sodium fluoride at the dose of 20 mg/kg/day for 28 days resulted in significant diminution of testicular Delta5,3beta-hydroxysteroid dehydrogenase (HSD) and 17beta-hydroxysteroid dehydrogenase (HSD) activities and low plasma levels of testosterone, follicular stimulating hormone (FSH) and leutinizing hormone (LH). Spermatogenesis inhibited after sodium fluoride treatment has been assessed here by the quantification of different generation of germ cells like spermatogonia A (ASg), preleptotene spermatocyte (PLSc), midpachytene spermatocyte (MPSc) and step 7 spermatid (7Sd) at stage VII of seminiferous epithelial cycle. Furthermore, fluoride treatment was associated with low activities of testicular, prostatic and epididymal catalase (CAT), superoxide dismutase (SOD) and peroxidase along with elevation of malondialdehyde (MDA) and conjugated dienes (CD) in those tissues. Co-administration of calcium and Vitamin-E with fluoride resulted in a significant recovery from testicular disorders and oxidative stress in the testis and male accessory sex organs. The results of this study demonstrate that fluoride exposure, at the dose available in drinking water in contaminated areas, led to inhibition of testicular gametogenesis and steroidogenesis in association with oxidative stress in the testis and male accessory sex organs, which are protected significantly by dietary agents like Vitamin-E and calcium.

20 mg/kg/day is extremely high; useful in support of science regarding effects in extremely high natural levels.

Chinoy NJ, et al. 2006. Effects of fluoride ingestion with protein deficient or protein enriched diets on sperm function of mice. Fluoride 39:11-16.

The [fluoride-induced] decrease in sperm motility appears to be related to decline in SMAI and abnormal sperm counts. The significant decrease in sperm viability along with the above parameters would be expected to affect fertility, whereas inhibition of hyaluronidase and to some extent of acrosin could affect fertilizing capacity of the sperm. The results reveal that dietary factors such as increased protein intake can be especially valuable in curbing fluoride fertility toxicity.

Cai Z. 2006. Determination the changes of rooster sperm quality induced by chronic fluorosis. Livestock and Poultry Industry.

To ascertain the effect of chronic fluorosis on rooster sperm quality, chronic fluorosis model of roosters was rebuilt artificially by adding F- to the drinking water. In the 30th, 50th and 70th day, sperms of each animal were collected and the sperm density, sperm vigour and sperm abnormality rate were determined. [Results]: Chronic fluorosis may cause the reduction of sperm density and sperm vigour and raise of sperm abnormality rate. The control group has no discrepancy in different testing time. In the experimental group, sperm density of the 50th and 70th day is lower than 30th day, but there is no statistics discrepancy between the 50th and 70th day; and sperm vigour of the 70th day is lower than the 30th day . . . .

A study of excessively polluted areas.

Mou S, et al. 2006. Effect of fluorine, selenium and cadmium on lipid peroxide and microelements in rat’s testicle. Chinese Journal of Public Health.

In the fluorine group and cadmium group, the contents of lipid peroxide noticeably increased and the contents of glutathione peroxidase (GSH-Px) were remarkably reduced in the testicle of rats…

High levels.

Pushpalatha T, et al. 2005. Exposure to high fluoride concentration in drinking water will affect spermatogenesis and steroidogenesis in male albino rats. Biometals 18:207-12.

Semen analysis including sperm morphology assessment has been suggested to be a useful indication of the factors in man’s macro-environment, which can modulate or damage spermatogenesis (Mac Leod & Gold 1953). The present study was aimed to determine the reproductive toxic effects of male rat after ingestion of NaF [4.5-9 ppm] through drinking water.

Again, useful information regarding areas with excessively high natural levels.

Das S, et al. 2005. Induction of oxidative stress on reproductive and metabolic organs in sodium fluoride-treated male albino rats: protective effect of testosterone and vitamin e coadministration. Toxicol Mech Methods. 15(4):271-7.

The results of our experiment suggests that fluoride at the dose noted in drinking water in contaminated areas may induce oxidative stress in reproductive and metabolic organs that can be ameliorated significantly by testosterone or vitamin E coadministration. Moreover, as there was no significant variation in body weights among these groups, it may be predicted that this effect of fluoride on reproductive and metabolic organs is specific and is not due to general effect of fluoride.

High levels.

Jiang CX, et al. 2005. [Relationship between spermatogenic cell apoptosis and serum estradiol level in rats exposed to fluoride]. Wei Sheng Yan Jiu. 34:32-4.

The content of NaF in testis and the ratio of apoptotic spermatogenic cell in fluoride treatment groups significantly increased with increased experimental dosage and prolonged experimental period (P < 0.05). Meanwhile, the serum estradiol level significantly decreased (P < 0.05), which was negatively correlated with the content of NaF in testis as well as the ratio of apoptotic spermatogenic cell (P < 0.05). CONCLUSION: Excessive fluoride could lead disturbance to serum estradiol level during some range of dose and time, which is an important factor to spermatogenic cell apoptosis.

By excessive, they refer to the extremely high natural levels in some parts of China.

Jiang Q, et al. 2005. Effect of fluoride on expression of proliferating cell nuclear antigen in germ cells of rats’ testes. Chinese Journal of Endemiology.

In [fluoride] treated groups there were significant decreases in the sperm count and the rate of sperm motility (P 0.05), while the rate of sperm deformity increased (P 0.05) compared with the control group. Conclusions By inhibiting the expression of PCNA, NaF may decrease the count of germ cells and then damage the male reproductive system.

High levels.

Krasowska A, et al. 2004. Zinc protection from fluoride-induced testicular injury in the bank vole (Clethrionomys glareolus). Toxicology Letters 147: 229-235.

These data suggest that a zinc-enriched diet protects seminiferous tubules against fluoride toxicity by preventing the fluoride-induced testicular zinc deprivation.

Useful information for locations with extremely high natural levels, although water treatment to reduce fluoride levels is the desired management action.

An L, et al. 2004. Combined effects of vitamin E and fluoride on reproductive function in male mice. Chinese Journal of Control of Endemic Disease.

Conclusions: 200 or 300 mg/L sodium fluoride in drinking water can significantly decrease sperm count and mobility of male mice. Vitamin E was given while administrated with NaF, but effects on mice were not improved.

High levels.

Cui LX, et al. 2003. Experimental study on effect of fluoride on reproductive system of male rats. Chinese Journal of Endemiology.

Objective: To study the effects of excessive fluorine on reproductive system of male rats.Methods Sodium fluoride was administered to male rats with drinking water (150 mg/L) for 10 weeks. The sperm count, the rates of sperm mobility and aberration, the levels of biochemical marker enzyme of testis and epididymidis, as well as the levels of gonadal hormone in serum, were examined. And pathological alterations of testes were observed. Results: Contrasted with control rats, the sperm count, the rate of sperm mobility, as well as the levels of serum testosterone (T) and luteinizing hormone (LH), were suppressed by fluoride. While the rate of sperm aberration was elevated. The differences between two groups were significant ( P 0.05). Pathological alterations of testes were also found. Conclusions: The long-term exposure to fluorine of high dose could produce toxic effect on male reproductive system.

Ghosh D, et al. 2002. Testicular toxicity in sodium fluoride treated rats: association with oxidative stress. Reproductive Toxicolology 16(4):385.

This study examined the effect of sodium fluoride, a water pollutant important through the world, including India, on testicular steroidogenic and gametogenic activities in relation to testicular oxidative stress in rats. Sodium fluoride treatment at 20mg/kg/day for 29 days by oral gavage resulted in significant diminution in the relative wet weight of the testis, prostate, and seminal vesicle without alteration in the body weight gain. Testicular delta(5),3beta-hydroxysteroid dehydrogenase (HSD) and 17beta-HSD activities were decreased significantly along with significant diminution in plasma levels of testosterone in the fluoride-exposed group compared to the control. Epididymal sperm count was decreased significantly in the fluoride-treated group and qualitative examination of testicular sections revealed fewer mature luminal spermatozoa in comparison to the control. The seminiferous tubules were dilated in treated animals. Fluoride treatment was associated with oxidative stress as indicated by an increased level of conjugated dienes in the testis, epididymis, and epididymal sperm pellet with respect to control. Peroxidase and catalase activities in the sperm pellet were decreased significantly in comparison to the control. The results of this experiment indicate that fluoride at a dose encountered in drinking water in contaminated areas exerts an adverse effect on the male reproductive system and this effect is associated with indicators of oxidative stress.

Yang KD, et al. 2002. [Study on antagonistic effects of selenite on fluoride-induced impairments of testis and epididymis in rats]. Chung-Kuo Kung Kung Wei Sheng 18: 427-9.

To study the mechanisms of the antagonistic action of selenite on fluoride-induced male reproductive damages, and find out the optimal level of selenite in drinking water against fluoride toxicity… Results: Fluoride could cause the elevation of fluorine concentrations in blood and urine, the abnormalities of trace elements in serum and testis, as well as the significant increase of lipid peroxide (LPO) levels, and the obvious decreases of activities of glutathione peroxidase (GSH-Px) and ATPase in testis and epididymis of rats exposed to fluoride in drinking water (68 mg/L).

Chinoy NJ, Sharma A. 2000. Reversal of fluoride-induced alteration in cauda epididymal spermatozoa and fertility impairment in male mice. Environmental Sciences 7: 29-38.

The effects of sodium fluoride (NaF) ingestion (10 mg NaF/kg body weight) and the possible therapeutic effects of ascorbic acid (AA, 15 mg/animal/day) and/or calcium phosphate (Ca, 25 mg/animal/day) on the reproductive functions and fertility of male mice were investigated. NaF-ingestion brought about a significant decline in sperm acrosomal acrosin and hyaluronidase. Cauda epididymal sperm stained with alcoholic acidic silver nitrate reagent revealed acrosomal damage and deflagellation. However, sperm nuclear integrity was not affected by the treatment. The reduced activity of the enzymes as well as the structural and metabolic alterations in the sperm led to a significant decrease in sperm count, and motility and live:dead ratios but an increase in abnormal sperm which ultimately lead to a poor fertility rate. The cessation of NaF-treatment was not conducive to bringing about a complete recovery. However, the administration of AA or Ca to NaF-treated mice revealed significant recovery from fluoride toxicity in all the above parameters.

Elbetieha A, et al. 2000. Fertility effects of sodium fluoride in male mice. Fluoride 33: 128-134.

Sexually mature male Swiss mice were exposed at 60 days of age to 100, 200 and 300 ppm sodium fluoride (NaF) in their drinking water for 4 weeks or 10 weeks. The effect of NaF exposure on fertility was assessed by breeding these males with untreated female mice after the exposure periods. Fertility was significantly reduced at all three concentrations by exposure for 10 weeks but not for 4 weeks. The number of implantation sites and viable fetuses was significantly reduced in females mated with males that had ingested NaF at a concentration of 200 ppm for 10 weeks. Relative weights of seminal vesicles and preputial glands were significantly increased in mice exposed to 200 and 300 ppm NaF for 4 weeks but not in mice exposed for 10 weeks. These results indicate that long-term ingestion of NaF adversely affects fertility in male mice.

Lu Y, et al. 2000. Effect of water defluoridation by activated magnesia on sperm morphology in mice. Chinese Journal of Control of Endemic Diseases.

Conclusion: The sperm aberration rate of mice were significantly increase after drinking high fluoride water [50 + 100 mg/l F].

High levels.

Zhu X. 2000. The primary study of antagonism of selenium on fluoride induced reproductive toxicity of male rat. China Public Health.

The protective effect of ascorbic acid [vitamin C] at a dose level of 1.0mg/L in drinking water against the fluoride induced damage on reproductive system of rat was studied.150 mg/L sodium fluoride (NaF) in drinking water of male rat can cause significant decreases in sperm count and mobility, increases in serum and testicular lipid peroxides (LPO) contents, and depress the adenosine triphosphatase (ATPase) activity in epididymis. All of these effects are reversible by adding adequate ascorbic acid in drinking water simultaneously. The effects of ascorbic acid against fluoride induced damages are similar to those produced by 2.0 mg/L selenium in the drinking water of rats. However, no significant recovery of fluoride-induced effects on GSH Px activities in the tissues of testis and epididymis were observed in the ascorbic acid and fluoride group. The mechanism of ascorbic acid on fluoride induced damage of male reproductive system needs to be further studied.

Chinoy NJ, Mehta D. 1999. Effects of protein supplementation and deficiency on fluoride-induced toxicity in reproductive organs of male mice. Fluoride 32: 204-214.

These results clearly indicate that protein supplementation is beneficial to overcome the toxic effects of fluoride on testicular steroidogenesis, protein, carbohydrate, and energy and oxidation metabolisms in the reporductive organs of male mice. Protein deficiency, on the other hand, aggravates fluoride toxicity. A protein-supplemented diet might therefore substantially mitigate certain fluoride-induced health hazards in humans living in endemic areas.

Chinoy NJ, Sharma A. 1998. Amelioration of fluoride toxicity by vitamin E and D in reproductive functions of male mice. Fluoride 31: 203-216.

Studies on the beneficial effects of vitamins E and D supplementation on functions of caput and cauda epididymides, their spermatozoa, vas deferens and seminal vesicle of sodium fluoride (NaF) treated male mice were carried out. The NaF treatment resulted in significant decrease in the body and epididymis weight but those of vas deferens and seminal vesicle were not affected. NaF treatment brought about alterations in epididymal milieu as elucidated by the significant decrease in levels of sialic acid and protein as well as activity of ATPase in epididymides. As a result, the sperm maturation process was affected leading to a significant decline in cauda epididymal sperm motility and viability. This caused a significant reduction in fertility rate. The cauda epididymal sperm count was also significantly reduced. The data obtained suggest that fluoride treatment induced significant metabolic alterations in the epididymides, vas deferens and seminal vesicles of mice.

Pinto R, et al. 1998. NaF may disturb male fertility in rodents. Toxicology Letters 95(Suppl 1): 214.

Conclusions: The modification of some parameters related to fertility by the repeated oral NaF intake, in rodents, suggest that NaF has potential to disturb male fertility.

Chinoy NJ, et al. 1997. Fluoride toxicity in the testis and cauda epididymis of guinea pig and reversal by ascorbate. Medical Science Research 25: 97-100.

The cauda epididymal spermatozoa were highly sensitive to the effects of sodium fluoride as their structural and metabolic alterations led to marked decreases in their motility, live:dead ratio and sperm mitochondrial activity index but increases in sperm abnormalities and alterations in sperm membrane phospholipids, particularly phosphatidylinositol and phosphatidyl serine. The activities of ATPase and succinate dehydrogenase as well as glutathione levels were decreased in testis by sodium fluoride treatment, revealing disturbances in its metabolism.

Chinoy NJ, et al. 1997. Fluoride toxicity on rat testis and cauda epididymal tissue components and its reversal. Fluoride 30: 41-50.

The toxic effects were evaluated of sodium fluoride (NaF) ingestion on the physiology of tissue components of testis and epididymis of adult, male albino rats, and the possible reversal of the effects by use of some antidotes. The results revealed that the testis and cauda epididymal proteins were altered, with disappearance of some proteins and induction of some new ones. This is the first report of such changes… On comparing the alterations in protein profile, phospholipds and glutathione in both tissues, it was evident that the protein profile was disturbed more in testis than in cauda epididymis, whereas phospholipids and gluthathione levels were affected more in cauda than in testis… As the proteins of testis and cauda epididymis are known to be involved as androgen carrier proteins, in testicular functions and in sperm motility, it follows that NaF treatment might affect the levels of these proteins as well as alter sperm motility and viability.

Luke J. 1997. The Effect of Fluoride on the Physiology of the Pineal Gland. Ph.D. Thesis. University of Surrey, Guildford. p. 177.

At 16 weeks, the [High-Fluoride] males had a significantly lower mean testes weight than the [Low-Fluoride] males: 1.10 ± 0.11 vs. 1.32 ± 0.18 g, respectively (p < 0.002). The reason for this is not clear.

High levels.

Susheela AK, Kumar A. 1997. Ultrastructural studies on the leydig cells of rabbits exposed to chronic fluoride toxicity. Environmental Sciences 5:79-94

The present communication addresses the effect of chronic fluoride toxicity on the structure of rabbit Leydig cells using light, scanning and transmission electron microscopy… [T]he extensive degenerative changes (which are progressive) seen in the Leydig cells due to fluoride toxicity may lead to a decrease in testosterone production resulting initially in regression of seminiferous tubules and structural damage of the epididymis and finally cessation of spermatogenesis.

Yang K, et al. 1996. Study on effects of selenium on lipid peroxidation and trace elements changes induced by fluorine and selenium in tissue of rat testis.

The key point is that high dosage of fluoride may cause testicular lipid peroxidation, wheareas the selenium possesses the antagonistic action against the lipid peroxidation resulting from fluoride.

Chinoy NF, et al. 1995. Amelioration of fluoride toxicity in some accessory reproductive glands and spermatozoa of rat. Fluoride 28: 75-86.

The [fluoride] treatment resulted in structural and metabolic alterations in sperm, leading to low sperm motility, a low sperm mitochondrial activity index (SMAI), reduced viability (live:dead ratio), and changes in sperm membrane phospholipids (particularly phosphatidylinositol, phosphatidylserine and phosphatidylethanolamine, which would affect hormone receptor interaction and their functions). A significant reduction in electrolyte levels of sperm also occurred which would also affect their viability. The protein levels in cauda epididymal sperm suspension, vas deferens, seminal vesicle and prostate were significantly decreased after NaF administration, which may be due to altered protein metabolism by interference of fluoride ions. The changes in epididymal protein profile, with absence of some proteins and induction of some new ones, were probably a result of the “stress proteins” in NaF-treated rats affecting the structural and functional integrity of sperm. Glycogen accumulation in vas deferens and a decrease in fructose in seminal vesicles and vas deferens indicated disturbances in carbohydrate metabolism in these organs. However, withdrawal of treatment resulted in partial recovery. A significant recovery from NaF-induced toxic effects occurred following administation of ascorbic acid and/or calcium, while combined treatment (AA + Ca++) for 70 days manifested a synergistic effect. The transient fluoride-induced effects were reversible. The results, corroborated by earlier data from our laboratory, show that fluoride has a definite effect on male reproduction and fertility. Ascorbic acid and calcium are proposed as therapeutic agents in endemic populations for amelioration of effects of fluoride.

Zhao ZL, et al. 1995. The influence of fluoride on the content of testosterone and cholesterol in rat. Fluoride 28: 128-130.

Results showed that the serum testosterone level had decreased with time in rats drinking water containing 100 and 200 mg/L fluoride. Testis cholesterol level did not change . . . . Results suggest that fluoride may have some harmful effects on the reproductive system in male rats.

Chinoy NF, et al. 1994. Beneficial effects of ascorbic acid and calcium on reproductive functions of sodium fluoride-treated prepubertal male rats. Fluoride 27: 67-75.

The therapeutic effects of ascorbic acid and calcium (Ca2+) supplementation on reproductive functions of fluoride-treated (10 mg/kg body weight) male rats were investigated. Sodium fluoride treatment resulted in a decrease in almost all parameters studied except concentration of testicular cholesterol, which implies that androgen synthesis might not be affected by NaF treatment. Succinate dehydrogenase activity decreased in testis suggesting that its oxidative metabolism was altered by NaF treatment. Adenosine triposphatase activity, protein, and sialic acid levels in caput and cauda epididymides also showed a decrease. All these changes resulted in a significant decrease in sperm motility and thereby fertility rate.

Kumar A, Susheela AK. 1994. Ultrastructural studies of spermiogenesis in rabbit exposed to chronic fluoride toxicity. International Journal of Fertility and Menopausal Studies 39(3):164-71.

OBJECTIVE–To address the role of fluoride in causing defects to spermatids and epididymal spermatozoa. METHODS–Male rabbits were treated with 10 mg NaF/kg body weight daily for 18 months and maintained under identical laboratory conditions along with the control rabbits not given NaF. Testis and epididymis (caput) were investigated for ultrastructural details of spermatids and spermatozoa. RESULTS–A wide variety of structural defects were observed in the flagellum, the acrosome, and the nucleus of the spermatids and epididymal spermatozoa of fluoride-treated rabbits. Abnormalities included absence of outer microtubules, complete absence of axonemes, structural and numeric aberrations of outer dense fibers, breakdown of the fibrous sheath, and structural defects in the mitochondria of the middle piece of the flagellum. Detachment and peeling off of the acrosome from the flat surfaces of the nucleus were also observed. CONCLUSION–The abnormalities observed render the sperm nonfunctional and ineffective, and thus there is a possible role of fluoride in causing infertility.

Narayana MV, Chinoy NJ. 1994. Reversible effects of sodium fluoride ingestion on spermatozoa of the rat. International Journal of Fertility and Menopausal Studies 39(6):337-46.

The results revealed that the sperm acrosomal hyaluronidase and acrosin were reduced after 50 days of NaF treatment. Sperm stained with acidic alcoholic silver nitrate revealed acrosomal damage and deflagellation, which might be causative factors for the reduced activity of the enzymes. These alterations also resulted in a decline in sperm motility. The cauda epididymal sperm count was decreased, perhaps because of spermatogenic arrest. Thus, the low sperm motility and count ultimately contributed toward reduction in fertility by NaF treatment. However, withdrawal of NaF treatment for 70 days produced incomplete recovery, while administration of ascorbic acid and calcium, individually and in combination, brought about significant recovery of fluoride-induced effects. Thus, the effects of fluoride on sperm structure and metabolism of rats are transient and reversible.

Narayana MV, Chinoy NJ. 1994. Effect of fluoride on rat testicular steroidogenesis. Fluoride 27: 7-12.

In view of reports of infertility among human populations in fluorosis prevailing regions, we investigated the effect of fluoride ingestion on testicular steroidogenesis in rats. Sodium fluoride (NaF) was administered to the rats orally at a daily dose of 10mg/kg bodyweight for 50 days. The treatment did not cause significant change in testicular cholesterol levels, indicating that metabolism was not altered and that there was no hypo/hypercholesterolemic effect. In addition, activities of the intermediary enzymes in androgenesis, viz., 3ß- and 17ß-hydroxysteroid dehydrogenase were only modestly decreased by NaF ingestion. Subsequently, the determination of circulating androgen levels in NaF-treated rats showed a downward trend compared to those of the control group, suggesting alteration in testosterone concentration. The histomorphometric studies revealed significant change in the Leydig cell diameter m correlation with the androgen levels. These results indicate that fluoride does interfere with steroidogenesis in short-term low-dose exposures in rats.

Zhao Z, et al. 1994. Influence of fluoride on the contents of testosterone and cholesterol. Chinese Journal of Endemiology

The results showed that the level of serum testosterone had the tendency to decrease as the period of time was prolonged in the rats drinking water containing 100 mg/L and 200 mg/L fluoride. The level of cholesterol in testis did not change significantly, but in liver it was significantly declined at the fourth and sixth week as compared with the control group. The results suggest that fluoride may have a harmful effect on the reproductive system.

Zhen J, et al. 1993. Experimental study on effect of sodium fluoride on reproductive system of male rats. Industrial Health and Occupational Diseases.

Sodium fluoride was administered to male rats with drinking water for 6 months. The count, morphological change and motility of sperms were examined. The levels of serum testosterone and activity of testicular lactate dehydrogenase were determined, arid the changes of testes in ultrastucture were observed. The results showed that the long-term exposure to fluoride of high dose may produce toxicity effect on male reproductive system.

Chinoy NJ, et al. 1992. Effects of fluoride ingestion on the physiology of reproductive organs of male rats. Journal of Environmental Biology 13: 55-61.

In fluorotic rats, testicular cholesterol and serum testosterone levels were not affected. However, succinate dehydrogenase activity in testis was inhibited. Similarly, adenosine triphosphatase activity and sialic acid levels in epididymides were also suppressed with more pronounced effect on cauda epididymis. Consequently, sperm motility and count were decreased leading to a significant decline in fertility by fluoride treatment. Hence, rat is also sensitive to fluoride toxicity.

Chinoy NJ, Sequeira E. 1992. Reversible fluoride induced fertility impairment in male mice. Fluoride 25 71-76.

Sodium fluoride (NaF) fed to adult male albino mice at a dose of 10 mg and 20 mg/kg body weight, caused a significant decrease in sperm county and motility. Scanning electron microscopy and silver nitrte staining showed large numbers of deflagellated spermatozoa, with acrosomal, midpiece and tail abnormalities. The treatment caused loss of fertility rate when normal cycling female mice were mated with treated males.

Krasowska A, Wiostowski T. 1992. The effect of high fluoride intake on tissue trace elements and histology of testicular tubules in the rat. Comparative Biochemistry and Physiology: Part C 103(1):31-4.

Fifty percent of the 100- and 200 ppm F rats after 16 weeks exhibited histopathologic changes in the germinal epithelium of the testes, which resembled those in Zn-deficient rats. The data suggest that a deprivation of testicular Zn due to a high F intake may be directly responsible for the injury of testicular tubules.

Chinoy NJ, et al. 1991. Microdose vasal injection of sodium fluoride in the rat. Reproductive Toxicolology 5(6):505-12.

A single microdose (50 micrograms/50 microL) injection of sodium fluoride (NaF) into the vasa deferentia of adult male albino rats (Rattus norvegicus) caused arrest of spermatogenesis and absence of spermatozoa in the lumina of the seminiferous tubules of the testes, which consequently led to a decline in the sperm count in the caudae epididymides. Scanning electron microscopy of cauda and vas deferens sperm revealed deflagellation and tail abnormalities. This is probably related to the alterations in the internal milieu of these organs which rendered the spermatozoa immotile and consequently caused fertility impairment in the experimental animals. Thus microdoses of sodium fluoride were found to affect reproductive function and fertility rate.

Susheela AK, Kumar A. 1991. A study of the effect of high concentrations of fluoride on the reproductive organs of male rabbits, using light and scanning electron microscopy. Journal of Reproductive Fertility 92(2):353-60.

Fluoride was orally administered to rabbits at 10 mg NaF/kg body weight for 18 or 29 months. The animals were then killed and the structure of the testis, epididymis and vas deferens studied under light and scanning electron microscopes. In animals treated for 29 months, the spermatogenic cells in the seminiferous tubules were disrupted, degenerated and devoid of spermatozoa. In animals treated for 18 or 29 months, loss of cilia on the epithelial cells lining the lumen of the ductuli efferentes of the caput epididymidis and of stereocilia on the epithelial cells lining the lumen of the vas deferens was observed. In some regions of the epithelial lining of the lumen of the ductuli efferentes and vas deferens, the boundaries of the cells were not clear and appeared to be peeled off. Mucus droplets were abundant in the vas deferens of control animals, but absent in both the treated groups. Spermatogenesis ceased only in animals treated for 29 months. The difference in the structural changes observed in the testes of the 2 treated groups may have been due to the blood-testis barrier. It is concluded that ingestion of high concentrations of fluoride has harmful effects on the male reproductive system.

10 mg NaF/kg body weight for 18 or 29 months would be equivalent to 450 L of city water treated at the rate of 0.7 mg/L.

Shashi A. 1990. Histopathological changes in rabbit testes during experimental fluorosis. Folia Morphol (Praha) 38(1):63-5.

The aim of the study was to evaluate relationship between infertility and the histological structure of the testes following the subcutaneous administration of different doses of sodium fluoride (5, 10, 20 and 50 mg/kg/day), for 100 days, to groups of six male albino rabbits; the six control animals were given 1 cc distilled water/kg b.w./day for the same length of time. Deficient maturation and differentiation of the spermatocytes and an increase in the amount of interstitial tissue were found in the experimental animals. In the higher dosage groups, spermatogenesis stopped and the seminiferous tubules became necrotic. The study thus established the existence of a definite relationship between fluorosis and testicular damage.

Keqin S, et al. 1990. Ultrastructural observations of testes and prostrate gland in rat with chronic fluorosis. Journal of China Medical University.

The results in this experiment suggest that: interstitial cell of testes could be damaged and spermiogenesis could be blocked [by fluoride exposure]. These might supply a morphologic basis for decrease in serum testosterone level and impairment of reproduction during chronic fluorosis.

Araibi AA, et al. 1989. Effect of high fluoride on the reproductive performance of the male rat. Journal of Biological Sciences Research 20: 19-30.

The effect of high fluoride intake (100 and 200 ppm) in the ration was studied in male rats. After sixty days of treatment, rats showed a decrease in the mean diameter of the seminiferous tubules and the percentage of the tubules containing spermatozia and increase in the in the thickness of the peritubular membranes. The effect was more prominent with the higher dose of fluoride. Serum testosterone level in rats [which] received 200 ppm fluoride showed a sharp decrease, whereas in those treated with 100 ppm did not differ significantly from the control. The fertility performance of treated rats was reduced and the results revealed a reduction in the number of pregnant females and newborns of both treated groups. Lowest dose of fluoride had a similar but less marked effect on the fertility performance than the higher dose. It is concluded that the high fluoride intake causes a decline in the reproductive performance of the adult male rats, although the clinical signs in the teeth are absent.

Chinoy NJ , Sequeira E. 1989. Effects of fluoride on the histoarchitecture of reproductive organs of the male mouse. Reproductive Toxicolology 3(4):261-7.

The effects of sodium fluoride (NaF) ingestion in two doses (10 and 20 mg/kg body weight) for 30 days on histology and histocytometry of reproductive organs of the adult male mouse were investigated. In order to study reversibility, treatment was withdrawn for one and two months… NaF treatment caused severe disorganization and denudation of germinal epithelial cells of seminiferous tubules with absence of sperm in the lumina. The Leydig cell and nucleus diameters were not affected. The caput epididymis showed fewer changes than the cauda. However, epithelial cell nuclear pyknosis and absence of luminal sperm were observed. A reduction in epithelial cell height, nuclear pyknosis, denudation of cells, and absence of sperm occurred in the cauda epididymis. The vas deferens epithelium showed nuclear pyknosis, clumped stereocilia, and cell debris but no sperm in the lumen and an increase in the lamina propria. The prostate and seminal vesicles were not affected by treatment. Withdrawal of treatment caused marked recovery in the histoarchitecture of these organs. The effects of NaF treatment are therefore transient and reversible.

Eckerlin RH, et al. 1988. Ameliorative effects of reduced food-borne fluoride on reproduction in silver foxes. Cornell Veterinarian 78(4):385-91

The serum testosterone decreases significantly and there is a dose response relationship between the level of serum testosterone and fluoride concentration of drinking water. The serum [luteinizing hormone] has no significant change.Reduction of ingested fluoride in a skulk of silver foxes resulted in the reduction of fluoride burden, decreased neonatal mortality and increased kit production during a two breeding and whelping season period.

Yuan S. 1989. The influence of fluorosis on the function of pituitary-gonadal axis in rat. Chinese Journal of Endemiology.

Animal models of subacute and chronic fluorosis were developed in male rats with injection of NaF solution and drinking water with high NaF content respectively. The results were as follows: In the rats suffered from subacute fluorosis the relative weight of prostate, testis and pituitary has no significant change; serum testosterone decreases ,serum LH increases significantly and pituitary LH content has no change. In the rats suffered from chronic fluorosis the relative weight of testis and pituitary has no significant change, H owever, the relative weight of prostate shows a tendency of decrease with increasing F- concentration added tothe drinking water. The serum testosterone decreases significantly and there is ad ose-response relationship between the level of serum testosterone and F- concentration of drinking water. The serum LH has no significant change. The pituitary LH content shows a tendency of decrease.

Pattee OH, et al. 1988. Effects of dietary fluoride on reproduction in Eastern Screech-Owls. Archives of Environmental Contamination and Toxicology 17: 213-218.

Sixty-six eastern screech-owls (Otus asio) were paired and randomly assigned to dietary treatment groups of 0, 40, or 200 ppm (mg/kg) fluoride (as sodium fluoride) in November 1981. Hatching success was adversely affected at the 200 ppm (mg/kg) level, suggesting potential detrimental impacts to wild populations exposed to fluoride pollution.

Pati PC, Bhunya SP. 1987. Genotoxic effect of an environmental pollutant, sodium fluoride, in mammalian in vivo test system. Caryologia 40:79-87.

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.

Kour K, Singh J. 1980. Histological finding of mice testes following fluoride ingestion. Fluoride 13: 160-162.

The study was designed in order to assess the relationship between infertility and histological structure of testes following administration of varying doses of sodium fluoride. One hundred adult male albino mice were fed 10 ppm (Group A), 500 ppm (Group B) and 1000 ppm (Group C) of sodium fluoride in drinking water. The Group A animals were sacrificed at the end of one month, Group B after two and Group C after three months. The testes were removed and, after being processed in the usual manner, they were stained with hematoxylin and eosin. In Groups B and C, the higher dosage groups, there was a lack of maturation and differentiation of spermatocytes. In animals sacrificed at the end of three months, spermatogenesis had stopped and the seminiferous tubules had become necrotic. A definite relationship between fluorosis and damage to the testes has, therefore, been established by this study.

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