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Developmental toxicity of sodium fluoride measured during multiple generations
Abstract
Sodium fluoride (NaF) has been used to fluoridate drinking water in the United States since the mid 1940s. Because of the lack of reliable studies on the multigeneration effects of the compound, NaF (0, 25, 100, 175 or 250 ppm in drinking water) was given to rats continuously during three generations. Parental (F0) generation rats were treated for 10 weeks and mated within groups. At gestation day 20, caesarean sections were performed and eight F0 females per group and their litters (F1) were observed for implant status, fetal weight and length, sex and morphological development. The remaining F0 females (29-32 per group) were allowed to litter. F1 offspring (36 of each sex per group) were mated within groups, and caesarean sections were performed at gestation day 20. The F1 females and their litters (F2) were observed for implant status, fetal weight and length, sex and morphological development. In addition, F2 fetuses were evaluated for internal (soft-tissue) and skeletal development. Decreased fluid consumption for F0 and F1 dams at 175 and 250 ppm was attributed to decreased palatability of the solution. No dose-related effects in feed consumption or mean body weight gain were observed in either F0 or F1 females. Numbers of corpora lutea, implants, viable fetuses and fetal morphological development were similar in all groups. No dose-related anomalies in internal organs were observed in F2 fetuses. Ossification of the hyoid bone of F2 fetuses was significantly decreased at 250 ppm. Because of the decreased ossification of the hyoid bone, 250 ppm is considered the effect level.
... Collins et al. [18,19] studied the effects of NaF ingestion at 0, 25, 100, 175 and 250 毺g/mL in drinking water in rats throughout three generations. Decreased fluid consumption observed at 175 and 250 毺g/mL was attributed to decreased palatability and did not affect reproduction. ...
... However, ossification of the hyoid bone of F2 foetuses was significantly reduced at 250 毺g/mL . Because of the decreased ossification of the hyoid bone, 250 毺g/mL (25.1 mg/kg body weight) is considered the effect level [19] . ...
High fluoride content is known to cause dental and skeletal abnormalities. In addition, present review indicates that sodium fluoride consumption caused increased number of r=esorptions and dead foetuses. Various skeletal anomalies such as wavy ribs, presence of 14th ribs, lacking 6th sternebrae and incompete ossification of skull occur. All these changes could be due to oxidative stress caused by fluoride consumption. Fluoride-induced changes could be successfully ameliorated by cotreatment with vitamins and calcium.
... Collins et al. [242,243] investigated effects of oral administration of 10, 25, 100, 175, and 250 ppm NaF daily throughout gestation in rats and throughout three generations. Decreased fluid consumption observed at 175 and 250 ppm was attributed to decreased palatability and did not affect reproduction. ...
... An increase in incidence of skeletal abnormalities, such as presence of 14 ribs, wavy ribs, dumbbell shaped 6 th sternebrae, and incomplete skull ossification, were observed in fetuses after oral administration of various doses of NaF from day 6 to 19 of gestation in rats [244]. A significant increase was seen in rats in average number of fetuses with three or more skeletal variation in the 250 ppm (25.1 mg/kg body weight) group [238,243]. Ossification of the hyoid bone of F2 fetuses was significantly decreased. Fluoride has been reported to Therapy, 2007, Vol. 2, No. 3 203 decrease the bone quality of femoral shaft and neck in 30 and 60 mg F -.L -1 treated young growing rats 6 weeks of age [248]. ...
Fluoride has long been known to influence the activity of various enzymes in vitro. Later it has been demonstrated that many effects primarily attributed to fluoride are caused by synergistic action of fluoride plus aluminum. Aluminofluoride complexes have been widely used as analogues of phosphate groups to study phosphoryl transfer reactions and heterotrimeric G proteins involvement. A number of reports on their use have appeared, with far-reaching consequences for our understanding of fundamental biological processes. Fluoride plus aluminum send false messages, which are amplified by processes of signal transduction. Many investigations of the longterm administration of fluoride to laboratory animals have demonstrated that fluoride and aluminofluoride complexes can elicit impairment of homeostasis, growth, development, cognition, and behavior. Ameliorative effects of calcium, vitamins C, D, and E have been reported. Numerous epidemiological, ecological, and clinical studies have shown the effects of fluoride on humans. Millions of people live in endemic fluorosis areas. A review of fluoride interactions from molecules to disease is necessary for a sound scientific assessment of health risks, which may be linked to the chronic intake of small doses of fluoride and aluminum from environmental and artificial sources.
... Even at 250 ppm (24 mg/kg bw/day), no adverse effects were observed in weights of organs including the reproductive organs, sperm parameters, serum LH, FSH and testosterone levels or the histopathology of the testes in P or F 1 males [60] or in the quantitative morphometry of the testes in F 1 males [61]. NaF was given to CD rats with the same regimen and procedure as above [60], and some pregnant P and F 1 females were sacrificed to examine the development of F 1 and F 2 fetuses, respectively, on GD 20 [62,63]. Although no adverse effects on reproduction or development were noted even at the highest dose of 250 ppm (24-28 mg/kg bw/day) [62], decreased ossification of the hyoid bone of F 2 fetuses was found at 250 ppm (28 mg/kg bw/day) [63]. ...
... NaF was given to CD rats with the same regimen and procedure as above [60], and some pregnant P and F 1 females were sacrificed to examine the development of F 1 and F 2 fetuses, respectively, on GD 20 [62,63]. Although no adverse effects on reproduction or development were noted even at the highest dose of 250 ppm (24-28 mg/kg bw/day) [62], decreased ossification of the hyoid bone of F 2 fetuses was found at 250 ppm (28 mg/kg bw/day) [63]. Drinking water containing NaF at 10, 50 or 100 mg/L (2, 10 or 19 mg/kg bw/day) was given to Wistar rats throughout gestation and lactation in the P generation through to 6 months after weaning in the F 2 generation, and F 2 males were examined [64]. ...
The present paper summarizes the results of animal studies on the reproductive and developmental toxicity of the degradation products of refrigerants, including trifluoroacetic acid (TFA), carbon dioxide (CO(2)), carbon monoxide (CO), carbonyl fluoride (CF), hydrogen fluoride (HF) and formic acid (FA). Excessive CO(2) in the atmosphere is testicular and reproductive toxic, embryolethal, developmentally neurotoxic and teratogenic in experimental animals. As for CO, maternal exposure causes prenatal and postnatal lethality and growth retardation, skeletal variations, cardiomegaly, blood biochemical, immunological and postnatal behavioral changes, and neurological impairment in offspring of several species. Very early studies of CO in rats and guinea pigs reported fetal malformations in exposed dams. The results of toxicological studies on sodium fluoride (NaF) were used to obtain insight into the toxicity of CF and HF, because CF is rapidly hydrolyzed in contact with water yielding CO(2) and HF, and NaF is similar in kinetics and dynamics to HF. Increased fetal skeletal variation, but not malformation, was noted after the maternal administration of NaF. Rat multiple-generation studies revealed that NaF caused retarded ossification and degenerative changes in the lung and kidney in offspring. There is a lack of information about the toxicity of TFA and FA.
... The teratogenic potential of sodium fluoride (NaF) has been investigated with pregnant laboratory rats. The administration of up to 250 ppm of NaF in drinking water was found to be non-teratogenic in single (Collins et al., 1995) and in multiple generational studies (Collins et al., 2001). Similarly, the NOAEL (no-observable-adverse-effect-level) for rats of NaF in drinking water was found to be > or=300 ppm (approximately 27 mg/kg/day) (Heindel et al., 1996). ...
... The teratogenic action of NaF has been reported in pregnant rats given NaF at a dose of 40 mg/kg/day (Guna Sherlin and Verma, 2001) but not in pregnant rats given smaller doses of NaF (Collins et al., 1995(Collins et al., , 2001Heindel et al., 1996). This indicates a dose-dependency of the teratogenic action of NaF; confirmed here with the frog embryos at a lower dose. ...
Fluoride was first associated with fetal malformation shortly after water fluoridation was initiated in the 1940s. Since many chemicals can interact directly with the embryo to cause malformation, the effects of fluoride on embryonic and fetal development were investigated. The effects of sodium fluoride on the development of frog embryos were studied under conditions described by the Frog Embryo Teratogenesis Assay-Xenopus (FETAX), a screening assay for teratogens. The most prominent malformations caused by sodium fluoride are reduction in the head-tail lengths and dysfunction of the neuromuscular system of the tadpoles. The values for LC50, EC50, and minimal concentration to inhibit growth (MCIG) of sodium fluoride met the limits established for a teratogen in frog embryos, showing that sodium fluoride is a direct acting teratogen on developing embryos. Since FETAX has a high degree of success in identifying mammalian teratogens, the observed teratogenic action of sodium fluoride on frog embryos would indicate a strong possibility that sodium fluoride may also act directly on developing mammalian fetuses to cause malformation.
... The discrepancy in experimental models and their relevance to humans might be due to the higher fluoride dosages in the animal models than the usual prevalent levels that are present in the environment which is in the range of 1-10 mg/l. Exposure to fluoride even at a higher dosage (250 ppm) throughout gestation did not cause any developmental defects in rats and rabbits (Collins et al. 1995;Heindel et al. 1996;Collins et al. 2001). Some studies report the effect of fluoride on development (Sherlin and Verma 2001), and impairment in IQ, thereby suggesting its status as a teratogen (Choi et al. 2012;Grandjean 2019), while other researchers question its validity (Guth et al. 2020). ...
Fluoride, one of the global groundwater contaminants, is ubiquitous in our day-to-day life from various natural and anthropogenic sources. Numerous in vitro, in vivo, and epidemiological studies are conducted to understand the effect of fluoride on biological systems. A low concentration of fluoride is reported to increase oral health, whereas chronic exposure to higher concentrations causes fluoride toxicity (fluorosis). It includes dental fluorosis, skeletal fluorosis, and fluoride toxicity in soft tissues. The mechanism of fluoride toxicity has been reviewed extensively. However, epigenetic regulation in fluoride toxicity has not been reviewed. This systematic review summarizes the current knowledge regarding fluoride-induced epigenetic toxicity in the in vitro, in vivo, and epidemiological studies in mammalian systems. We examined four databases for the association between epigenetics and fluoride exposure. Out of 932 articles (as of 31 March 2022), 39 met our inclusion criteria. Most of the studies focused on different genes, and overall, preliminary evidence for epigenetic regulation of fluoride toxicity was identified. We further highlight the need for epigenome studies rather than candidate genes and provide recommendations for future research. Our results indicate a correlation between fluoride exposure and epigenetic processes. Further studies are warranted to elucidate and confirm the mechanism of epigenetic alterations mediated fluoride toxicity.
... • Weight loss at 300 mg L -1 • Fluorosis of the teeth at 100 and 300 mg L -1 • Minimal hyperplasia of the gastric mucosa of the stomach at 100 and 300 mg L -1 (however, one high dose rat of each sex had an ulcer) • A dose-related increase in fluoride content of bone and urine with increasing fluoride concentration in the drinking water, and a significant increase in fluoride content in the plasma at 300 mg L -1 . Collins et al. (2001) reported that NaF in Sprague-Dawley rats' drinking water levels of up to 250 ppm. Concentrations of 28.4 mg NaF kg -1 body weight per day or 12.8 mg fluoride kg -1 body weight per day had no adverse effects on reproduction throughout three generations. ...
This report by the Danish Centre for Environment and Energy (DCE) and Greenland
Institute of Natural Resources (GINR) aims to gather worldwide information on
excitotoxicity data on fluoride (F), rare earth elements (REEs), and naturally occurring
radionuclides (NORs) that can potentially be used in Greenland. The report is not
explicitly focused on Kvanefjeld and Tanbreeze mineral exploration projects in south
Greenland but on the mining and milling of minerals containing REEs, NORs, and F in
general in Greenland.
The report provides relevant information to be used as a basis for environmental
regulation and monitoring of mining projects and establish guidelines on
concentrations threshold values for the REEs, NORs, and F in water, soil, dust,
vegetation, berries, birds, and fish both in the mining area but also for the surrounding
environment. This report can also be used for teaching or as guide for the general
public, politicians, authorities, education, industry, and other Greenland stakeholders.
... Chronic toxicity studies in rats, mice, and rabbits that focused on systemic effects of fluoride resulted in Lowest-Observed-Adverse-Effect Levels (LOAELs) ranging between 4.3 and 7.6 mg/kg b.w./day fluoride, and noobserved-adverse-effect levels (NOAELs) between 2.5 and 7.6 mg/kg b.w./day fluoride. Four well-conducted developmental toxicity studies (Collins et al. 2001(Collins et al. , 1995Heindel et al. 1996) are available which are in accordance with standard guidelines, used adequate numbers of animals, and administered sodium fluoride in drinking water. These studies resulted in NOAELs of 8.5-13.7 mg/kg b.w./day fluoride for rats and rabbits. ...
Since the addition of fluoride to drinking water in the 1940s, there have been frequent and sometimes heated discussions regarding its benefits and risks. In a recently published review, we addressed the question if current exposure levels in Europe represent a risk to human health. This review was discussed in an editorial asking why we did not calculate benchmark doses (BMD) of fluoride neurotoxicity for humans. Here, we address the question, why it is problematic to calculate BMDs based on the currently available data. Briefly, the conclusions of the available studies are not homogeneous, reporting negative as well as positive results; moreover, the positive studies lack control of confounding factors such as the influence of well-known neurotoxicants. We also discuss the limitations of several further epidemiological studies that did not meet the inclusion criteria of our review. Finally, it is important to not only focus on epidemiological studies. Rather, risk analysis should consider all available data, including epidemiological, animal, as well as in vitro studies. Despite remaining uncertainties, the totality of evidence does not support the notion that fluoride should be considered a human developmental neurotoxicant at current exposure levels in European countries.
... Based on the hypothesis that maternal fluoride exposure threatens foetal tooth development, we used the fluoride-exposed embryo model to investigate the miRNA profile changes (Fig. 1). Based on the literature (Bronckers et al., 2009;Collins et al., 1995Collins et al., , 2001aCollins et al., , 2001bPaul et al., 1998;Zhou et al., 2013) and our previous experience (Liu et al., 2014), 25-200 mg/L NaF is the most appropriate fluoride exposure concentration for female rats before gestation. The alternating white and orange bands and chalky white opaque were observed in female rats and the disorganized structure of the embryonic enamel organ indicated the success of model construction. ...
Evidence has shown that miRNAs could play a role in dental fluorosis, but there is no study has investigated the global expression miRNA profiles of fluoride-exposed enamel organ. In this study, we analysed the differentially expressed (DE) miRNAs between fluoride-treated and control enamel organ for the first time and found several candidate miRNAs and signaling pathways worthy of further research. Thirty Wistar rats were randomly distributed into three groups and exposed to drinking water with different fluoride contents for 10 weeks and during the gestation. The three groups were a control group (distilled water), medium fluoride group (75 mg/L NaF), and high fluoride group (150 mg/L NaF). On the embryonic day 19.5, the mandible was dissected for histological analysis, and the enamel organ of the mandibular first molar tooth germ was collected for miRNA sequencing (miRNA-seq) and quantitative real-time PCR analysis (qRT-PCR). Typical dental fluorosis was observed in the incisors of the prepregnant rats. In addition to the disorganized structure of enamel organ cells, 39 DE miRNAs were identified in the fluoride groups compared with the control group, and good agreement between the miRNA-seq data and qRT-PCR data was found. The functional annotation of the target genes of 39 DE miRNAs showed significant enrichment in metabolic process, cell differentiation, calcium signaling pathway, and mitogen-activated protein kinase(MAPK) signaling pathway terms. This study provides a theoretical reference for an extensive understanding of the mechanism of fluorosis and potential valuable miRNAs as therapeutic targets in fluorosis.
... Most of these investigations, which were conducted with a number of different animal species, including rats, mice and rabbits, found alterations in the levels of reproductive hormones, fertility, histological structures and developmental outcomes [18,19]. ...
Fluoride is a well-known environmental pollutant and its effect on human health has long been of interest to biomedical researchers. Various studies have shown that fluoride causes adverse effects on the fertility. Wistar albino female rats weighing 150-200 g were randomly divided into six rats in each group. The rats in experimental groups treated with 300 and 600 mg NaF/kg bw/day by oral gavage for 40 days. The present investigation focuses on the ovary of rat treated with sodium fluoride and its amelioration by curcumin. The results revealed that the sodium fluoride exposure to female rats treated with 300 mg NaF/kg bw/day, the surface epithelium had less number of ruffles and blebs of the plasma membrane. There was abrasion of ovarian surface epithelium. In rats treated with 600 mg/kg bw/day NaF, the cuboidal shape of the surface epithelium were changed into elongated appearance. The cells were devoid of microvilli, blebs and ruffles. After administration of curcumin, many follicles in different stages of development were visible. The ovarian surface epithelium showed normal surface epithelium with improvement in the shape of cuboidal cells.
... The result of the body weight change following fluoride ingestion is in agreement with the report of Collins et al. They stated that the decrease of body weight on NaF ingestion primarily could be due to malabsorption which can be reversed by selenium supplementation 15 . Increased generation of ROS and enhanced lipid peroxidation are considered responsible for the toxicity of a wide range of compounds 16 . ...
... This decrease in the body weight may due to decreased consumption of feed and water, which ultimately lead to reduced growth rate, whereas administration of selenium to NaF exposed rats caused no marked changes in the body weight. On the contrary, some authors while assessing the effects of NaF exposure in rats showed no alterations in body weight 6 , whereas other authors found significant amelioration in body weight and feed consumption in rats on the administration of Selenium 7 . ...
... There are also many reports on embryotoxicity influencing human fetuses/newborns using rodents and rabbits [42][43][44][45][46][47][48] . It has been reported that no detrimental influence on fetal growth was observed in a test with NaF administration in drinking water using pregnant rats, but reproductive failure due to reductions of spermatogenesis and steroid synthesis was observed in newborn animals in all treatment groups in another reported study. ...
The safety of fluoride use to prevent dental caries has been controversial. To clarify the risk of embryotoxicity of fluoride influencing human fetuses/newborns, we investigated the embryotoxicity levels of 4 fluorides (NaF, KF, SnF2, and CuF2) using the EST method, which is an in vitro embryotoxicity screening test developed by Spielmann et al. in 1997. Of the fluorides, NaF and SnF2 are used to prevent dental caries in Japan. All substances were "non-embryotoxic", but SnF2 and CuF2 were close to the borderline of "weak embryotoxic". Since many young people use fluoride to prevent dental caries, further investigation of the embryotoxicity of fluorine is desired.
... Il en ressort de ces résultats que la diminution de la production laitière peut être expliquée par la diminution de l'appétit due à la douleur au niveau dentaire et aux mauvaises conditions générales (amaigrissement, douleurs lors des déplacements, activité,…). Cependant, nous n'avons pas trouvé de relation entre la fluorose et la diminution de la capacité de reproduction, avec un p = 0.35 entre la reproduction et la fluorose osseuse et un p = 0.17 entre la reproduction et la fluorose dentaire, Collins et al. (2001) ont montré que des taux élevés en fluorures de sodium dans l'eau de boisson (supérieurs à 250 ppm), n'ont aucun effet sur la reproduction des rats. ...
Dans la région étudiée, second pôle industriel du Maroc, les eaux souterraines représentent les seules ressources en eau pour l'alimentation quotidienne de la population rurale et pour l'abreuvement du cheptel. Les résultats des analyses physico-chimiques des eaux montrent que la majorité des puits suivis dépassent les normes de l'OMS relatives à la qualité de l'eau. En effet, la concentration des fluorures dans l'eau de ces villages varie de 0,24 à 4,3 mg/l, ce qui semble être à l'origine de la fluorose dentaire observée chez le bétail de cette région. Les résultats de l'enquête épidémiologique réalisée sur le cheptel montrent une forte contamination par les fluorures générés, en grande partie, par les industries des phosphates. Plusieurs facteurs sont déterminants dans cette contamination, à savoir : approvisionnement en eau, durée d'exposition, approvisionnement en aliments, proximité des industries,…
... [37] The 2006 NRC review of EPA fluoride standards [46] concluded that adverse reproductive and developmental outcomes occur only at very high concentrations that are unlikely to be encountered by US populations. Although a single, small study on rats exposed to 2, 4, and 6 mg/L sodium fluoride for 6 months reported adverse affects on fertility and reproduction (reduced sperm motility), [177] other larger studies have shown no reproductive effects over multiple generations of rats exposed to fluoride in drinking water at doses up to 175 mg/L [178][179][180] and no effects on spermatogenesis in doses up to 100 mg/L. [181,182] A study of Mexican men found that fluoride intakes up to 27 mg/day did not affect sperm motility or other sperm parameters. ...
The World Health Organization (WHO), along with many other international health
authorities, recommends fluoridation of water supplies, where possible, as the most
effective public health measure for the prevention of dental decay.
A large number of studies and systematic reviews have concluded that water fluoridation is
an effective preventive measure against tooth decay that reaches all segments of the
population, and is particularly beneficial to those most in need of improved oral health.
Extensive analyses of potential adverse effects have not found evidence that the levels of
fluoride used for community water fluoridation schemes contribute any increased risk to
public health, though there is a narrow range between optimal dental health effectiveness
and a risk of mild dental fluorosis. The prevalence of fluorosis of aesthetic concern is
minimal in New Zealand, and is not different between fluoridated and non-fluoridated
communities, confirming that a substantial proportion of the risk is attributable to the intake
of fluoride from sources other than water (most notably, the swallowing of high-fluoride
toothpaste by young children). The current fluoridation levels therefore appear to be
appropriate.
This analysis concludes that from a medical and public health perspective, water
fluoridation at the levels used in New Zealand poses no significant health risks and is
effective at reducing the prevalence and severity of tooth decay in communities where it is
used. Communities currently without CWF can be confident that this is a safe option that is
cost saving and of significant public health benefit – particularly in those communities with
high prevalence of dental caries.
... Ghosh et al. /l in drinking water for 49 days. Sun et al. (2009, 2010) Rabbit 20 mg/kg by orally for 30 days Kumar et al. (2012) Rat 30 mg/l in drinking water for 4 months Oncu et al. (2007) Rat 5 mg/kg by gavage for 8 weeks Izquierdo-Vega et al. in head and tail length, decreased in the size of eggs and weight of hatchlings, malformation in developing brain, decline in learning and memory ability Frog 200 ppm with 1% DMSO when added to the embryos after 2and pulmonary tissue osteosarcomas of bone Rabbit Orally at a dose of 10, 20 mg/kg for 6 months Purohit et al. (1999) Rat 0, 25, 100, 175 or 250 ppm in drinking water for 10 weeksCollins et al. (2001) ...
Fluoride (F) is a naturally-occurring contaminant in the water. F is essential for normal maintenance of teeth and bones. However, prolonged exposure to high concentration of F is found to be deleterious to teeth, bones and other organs. Besides drinking water, F can enter the body through food, dental products, drugs and industrial emission. People living in areas where F contamination is much higher than the expected level, are found to suffer from not only teeth and bone problem but also other systems, including brain and its functions. Since animals respond to the toxic effects of F like human beings, the deleterious effects of F have been produced experimentally in animals in order to determine the mechanism involved in the action of F. The reports indicating the chronic harmful effects of F in teeth, bones, heart, liver, kidneys, gastrointestinal tract, lungs, brain, blood, hormones and biochemical parameters of experimental animals and in invitro studies have been reviewed in this article. The neurotoxic action of F that produces chiefly learning and memory impairment has also been included. The review also points out the harmful effects of F on reproduction, its teratogenic action and in inducing premature ageing. Finally, the reports indicating a reversal of certain toxicities of F in experimental animals after withdrawal of its exposure has been included.
... 4 Lower birth rates have also been found in areas with elevated F levels in the drinking water. 5 Various laboratory studies have investigated the effects of NaF on fetal development, 6,7 spermatogenesis, [8][9][10][11] and fertility. [12][13][14][15] Reproductive toxicity of F in cows and silver foxes has also been reported. ...
Ingestion of sodium fluoride at 100 and 300 ppm in drinking water for 12 weeks by adult male Sprague-Dawley rats was investigated for effects on territorial aggression, sexual behavior, and fertility. Body weight and absolute and relative testes weights were not affected, but the average weights of epididymis, ventral prostate, seminal vesicles, and preputial glands decreased significantly. A significant decline of spermatogenesis in testes due to a decrease in the number of spermatocytes (primary and secondary) and spermatids in the treatment group is attributed to a significant decrease in testosterone. Sperm motility and density were also significantly decreased in the cauda epididymis and in testes in both NaF- treated groups. In addition, the treatment markedly diminished aggressive and sexual behavioral parameters such as lateralization, boxing bouts, and ventral presenting postures. It also prolonged the time to the first mount, increased the intromission latency, decreased the number of intromissions, prolonged the post- ejaculatory interval, and increased the number of fetal resorptions in female rats impregnated by these males, thereby reducing their fertility.
... This decrease in the body weight can be attributed to decreased consumption of feed and water, which ultimately lead to reduced growth rate, whereas administration of vitamin E and selenium to NaF exposed rats caused no marked changes in the body weight. On the contrary, Collins et al., [12] while assessing the effects of NaF exposure in multigenerational rats, showed no alterations in body weight, whereas studies of Verma and Guna-Sherlin [13] found significant amelioration in body weight and feed consumption in rats on administration of vitamin E. The decrease found in body weight in the present investigation on fluoride ingestion could be due to primary malnutrition caused by fluoride by displacing other nutrients present in the diet (minerals/elements) and secondary malnutrition too results either from maldigestion or mal-absorption of nutrients. In addition, gastrointestinal complications could have altered nutritional abilities and deficiencies virtually on all the nutrients. ...
This experiment was designed to investigate the extent of peroxidative changes and histological alterations in the myocardium of rats exposed to high fluoride for two generations, in addition to ameliorative role of selenium and vitamin E on the above indices. Adult albino Wistar rats were given fluoride through drinking water (200 ppm F) and maintained subsequently for two generations, while they were exposed to fluoride throughout the experiment. Fluoride treatment significantly increased the lipid peroxidation and decreased the activity of antioxidant enzymes, viz., catalase, superoxide dismutase, and glutathione level in auricle and ventricle regions of the heart. Decreased feed and water consumption, organ somatic index and marginal drop in body growth rate were observed. Decreased antioxidant enzymes and increased malondialdehyde levels might be related to oxidative damage that occurs variably in the myocardium of rats. Biochemical changes were supported by the histological observations, which also revealed that chronic exposure to fluoride causes damage to the myocardium. Results of this study can be taken as an index of cardio-toxicity in rats exposed to water fluoridation. Further, oral supplementation of selenium and vitamin E not only inhibited oxidative stress but also enhanced the activities of antioxidant enzymes. Administration of antioxidants during fluoride exposure significantly overcame cardiac fluoride toxicity and therefore may be a therapeutic strategy for fluorotic victims.
... Developmental data collected during the study reported by Collins et al. (2001a) were more fully described by Collins et al. (2001b). When the gestation periods were specifically considered, fluid consumption was decreased in a dose-related manner, which became statistically significant only at the highest concentration of 250 ppm in F0 females (po0.01) and at 175 and 250 ppm for F1 females (po0.0001). ...
In developmental and reproductive toxicity studies, drinking water is a common means of delivering the test agent. Reduced consumption of toxicant-containing water raises questions about indirect effects of reduced maternal fluid consumption resulting from unpalatability, versus direct effects of the test compound. Issues to consider include: objective assessment of dehydration and thirst, the relative contributions of innate and learned behaviors to drinking behavior and flavor preference, and the objective assessment of physiologic stress. Not only do lab animals under ad lib conditions consume more water than the minimum required to maintain fluid balance, animals faced with water restriction have substantial physiologic capacity for protection of metabolic processes. Measures of blood biochemistry can provide quantifiable, objective indications of fluid balance, but changes in these parameters could result from other causes such as effects of a test toxicant. Consummatory behaviors in response to perceived need are highly influenced by learning. Hence, the drinking behavior, water intake, and flavor acceptance/preference of animals used in toxicology experiments could be subject to learning experiences with the test compound. Physiological symptoms of stress produced by water deprivation may be distinguishable from the symptoms associated with other generalized stressors, such as food deprivation, but doing so may be beyond the scope of most developmental or reproductive toxicity studies. Use of concurrent controls, paired to test groups for water consumption, could help distinguish between the direct effects of a test toxicant as opposed to effects of reduced water consumption alone.
Considerable integrative efforts have been made to investigate the effects of fluoride on female reproductive organs since the last years. The ingestion of fluoride causes adverse effects on human health like causing skeletal fluorosis, dental fluorosis, bone fractures, kidney problems, decrease birth rates, weakening of thyroid functionality, and impair intelligence, particularly in children. In this review, we discuss the adverse effects of fluoride on female reproductive organs and presented certain remedies. A total of 53 papers on the effect of fluoride on female reproductive organs, including 6 population surveys were examined. Google Scholar, Google, Research Gate, PubMed, and the International Journal of Fluoride have all been searched for fluoride research papers. Various doses and pathological effects have been described in this review article.
Puberty is one of the most important developmental milestones in life, involving complex physical and psychological changes. A trend towards earlier puberty has been well documented since the early 20th century. The decline in the pubertal age requires special attention due to its implications for long-term health outcomes with increased risks of reproductive cancers, type-2 diabetes, cardiovascular diseases, and psychological sequelae, and hence is a major public health concern. Increasing evidence suggests that environmental chemicals and nutrition may contribute to the trend towards earlier sexual maturation. Exposures that occur at susceptible developmental periods may impact the prenatal growth trajectory and development of the reproductive axis and potentially have long-term effects on the tempo of maturation later in life. Therefore, it is of public health importance to examine these modifiable elements at early life to improve the understanding of pubertal disorders and their link to adverse health conditions. The objectives of this dissertation were to determine whether exposures to environmental chemicals such as fluoride, lead and nutritional factors such as micronutrients at multiple life stages including in utero, early childhood and peripuberty are potential determinants of sexual maturation by using mother-offspring pairs from the Early Life Exposure in Mexico to ENvironmental Toxicants (ELEMENT) cohorts. We found that prenatal fluoride exposure during pregnancy was not associated with development of secondary sex characteristics directly, but associated with reduced peripubertal serum testosterone in boys and with increased peripubertal serum IGF-1 (insulin-like growth factor 1) in girls. Increased maternal consumption of selenium and zinc during pregnancy was related to advanced pubic hair growth, and increased maternal consumption of phosphorus and riboflavin during pregnancy was related to advanced genital development in boys. A significant negative association of prenatal and early childhood lead exposure with pubertal development was observed in girls. Our findings suggest that fluoride, lead, and intakes of micronutrients during early life may have long-term impacts on development of sexual maturation in adolescents, particularly in a sex-specific fashion. This work highlights the need for more research to examine associations between environmental factors during sensitive periods of development and sexual maturation to better understand pubertal disorders and their long-term consequences.
The current study was conducted at the Faculty of Pharmacy / University of Karbala for the period (12/2018 to 7/2019) and the study included the follow-up of (25) adult male rats from the Sprague dawley strain at the age of 75-90 day and the average weights (255-189) gram Divided into five groups each group included five males, The first group was dosed orally with the physiological saline solution at a concentration of 0.9 ml and considered as a control group (negative), The second group was dosed with sodium fluoride at a concentration of 20 mg / kg of body weight and was considered an infected control group (positive). The third group was dosed with sodium fluoride at the same concentration with vitamin B6 at a concentration of 0.83 mg / kg of body weight, The fourth group was dosed with sodium fluoride with the same concentration with vitamin B12 at a concentration of 25 micrograms / kg of body weight, The fifth group was dosed with sodium fluoride and vitamins B6 and B12 with the same concentrations mentioned above and by 1 ml of each of the above solutions and for all groups where the duration of the dose lasted 21 days and once daily.
After the end of the dose, the animals were sacrificed After anesthesia and blood drawing, which was divided into two groups, the first to measure blood standards and the second to measure biochemical standards, and then took the organs under study liver, kidneys and testes for the purpose of studying the pathological changes in these organs weights and measurements were recorded and the study showed the following results:
* There was a significant decrease (P <0.05) in body weight and organ
weights (liver and testes) while (kidneys) significant increase in weight in the References
2 positive control group dosed with sodium fluoride when compared with the negative control group and the other three groups dose fluoride and vitamins.
* There was a significant increase in (P <0.05) in the number of white blood cells and platelets, while the number of erythrocytes, hemoglobin level and packed cell volume decreased significantly (P <0.05) in the second group treated with sodium fluoride when compared with the negative control group while the totals did not appear treatment with vitamins no significant differences (p> 0.05).
* • There was a significant increase (P <0.05) in the liver enzymes ALT,
AST in the positive control group when compared with the negative control group while it was normal levels in other groups treated with vitamins. There was also a significant increase (P <0.05) in the ratio of cholesterol,
triglycerides, lipoproteins and LDL while the level of high density lipoproteins HDL decreased significantly (P <0.05) in the positive control group compared with the negative control group while Vitamin-treated groups were close to
normal.
* As well creatinine and bilirubin increased significantly (P <0.05) in the positive control group compared to the negative control group and were close to normal values in the other three groups treated with vitamins.
* The percentage of glutathione peroxidase decreased significantly (P <0.05) while the percentage of Malondyaldehyde increased significantly (P <0.05) in the positive control group compared with the negative control group while the proportions were close to their normal rates in vitamins treated groups.
* With regard to the results of histological study, histological changes in liver tissue were observed in the control group treated with sodium fluoride this is due to a change in the histological structure of the liver, represented by necrosis with apparent hepatocyte, a slight infiltration of inflammatory cells also, congestion, hemorrhage in the central vein and irregularity of hepatic cords compared to the negative control group. In the other three groups, the progressive improvement of tissue in vitamins was observed.
* Also, there were obvious histological changes in the kidney tissue in the positive control group, where there is a clear contraction of the glomerulus with congestion of nearby tissues with an outbreak, necrosis and breakdown in the tubules and cells with congestion and hemorrhage of the kidney tissue when compared with the negative control group. Minor pathological changes were observed in groups treated with vitamins.
* Changes in testicular tissue also occurred in the positive control group where the changes were represented by partial infarction and sperm tubular destruction with increased interphase due to death of intercellular cells with partial stop and damage to the stages of spermatogenesis and the disappearance of mature sperm with nearby blood vessels congestion compared to the control group. Negative changes were minor and tissues were close to normal in the groups treated with vitamins.
The results showed that treatment with vitamins B6 and B12 led to a
significant improvement in some blood and biochemical parameters as well as in the histological structure of the studied organs in male rats treated with sodium fluoride.
Recently, epidemiological studies have suggested that fluoride is a human developmental neurotoxicant that reduces measures of intelligence in children, placing it into the same category as toxic metals (lead, methylmercury, arsenic) and polychlorinated biphenyls. If true, this assessment would be highly relevant considering the widespread fluoridation of drinking water and the worldwide use of fluoride in oral hygiene products such as toothpaste. To gain a deeper understanding of these assertions, we reviewed the levels of human exposure, as well as results from animal experiments, particularly focusing on developmental toxicity, and the molecular mechanisms by which fluoride can cause adverse effects. Moreover, in vitro studies investigating fluoride in neuronal cells and precursor/stem cells were analyzed, and 23 epidemiological studies published since 2012 were considered. The results show that the margin of exposure (MoE) between no observed adverse effect levels (NOAELs) in animal studies and the current adequate intake (AI) of fluoride (50 µg/kg b.w./day) in humans ranges between 50 and 210, depending on the specific animal experiment used as reference. Even for unusually high fluoride exposure levels, an MoE of at least ten was obtained. Furthermore, concentrations of fluoride in human plasma are much lower than fluoride concentrations, causing effects in cell cultures. In contrast, 21 of 23 recent epidemiological studies report an association between high fluoride exposure and reduced intelligence. The discrepancy between experimental and epidemiological evidence may be reconciled with deficiencies inherent in most of these epidemiological studies on a putative association between fluoride and intelligence, especially with respect to adequate consideration of potential confounding factors, e.g., socioeconomic status, residence, breast feeding, low birth weight, maternal intelligence, and exposure to other neurotoxic chemicals. In conclusion, based on the totality of currently available scientific evidence, the present review does not support the presumption that fluoride should be assessed as a human developmental neurotoxicant at the current exposure levels in Europe.
Present study was undertaken to investigate the toxic effect of sodium fluoride (NaF)– and fluoride (F)-contaminated ground water on reproductive performances of male rats. Healthy adult male rats were categorised into three groups, first group of rats were served as control, whereas second group of rats were orally intubated with NaF (10 mg/kgbw/1 ml/rat) and third group of rats were allowed to drink F-contaminated ground water (5 mg/L) through drinking water bottles for 52 days. Exposure of NaF- and F-contaminated ground water caused significant decline in sperm motility, serum concentration of testosterone, and increase in sperm abnormality compared with controls. Further, significant histological alterations characterized with shrunken seminiferous tubules and degeneration of different stages of spermatogonial cells were observed in rats treated with NaF- and F-contaminated ground water. After the confirmation of toxic effect of F, these NaF- and F-contaminated ground water–treated male rats were allowed to mate with proven fertile untreated female rats to study the reproductive performances of male rats. There was a decline in parturition index, fertility index of male and female, gestation index and number of pups delivered in NaF-treated male rats compared with controls. However, gestation index and number of pups delivered were declined in F-contaminated ground water–treated male rats compared with controls. These results clearly indicate that F exposure affected the reproductive performances of male rats. The present study further revealed the fact that F-induced decline in testosterone levels, reduced sperm motility, and loss of spermatogonial cells affected the reproductive performances of male rats.
Fluoride, a ubiquitous environmental contaminant, is known to impair testicular functions and fertility; however the underlying mechanisms remain obscure. In this study, we used a rat model to mimic human exposure and sought to investigate the roles of apoptosis and autophagy in testicular toxicity of fluoride. Sprague–Dawley rats were developmentally exposed to 25, 50, or 100 mg/L sodium fluoride (NaF) via drinking water from pre-pregnancy to post-puberty, and then the testes of offspring were excised on postnatal day 56. Our results demonstrated that developmental NaF exposure induced an enhanced testicular apoptosis, as manifested by a series of hallmarks such as caspase-3 activation, chromatin condensation and DNA fragmentation. Further study revealed that fluoride exposure elicited significant elevations in the levels of cell surface death receptor Fas with a parallel increase in cytoplasmic cytochrome c, indicating the involvement of both extrinsic and intrinsic apoptotic pathways. Intriguingly, fluoride treatment also simultaneously increased the number of autophagosomes and the levels of autophagy marker LC3-II but not Beclin1. Unexpectedly, the expression of p62, a substrate that is degraded by autophagy, was also significantly elevated, suggesting that the accumulated autophagosomes resulted from impaired autophagy degradation rather than increased formation. Importantly, these were associated with marked histopathological lesions including spermatogenic failure and germ cell loss, along with severe ultrastructural abnormalities in testes. Taken together, our findings provide deeper insights into roles of excessive apoptosis and defective autophagy in the aggravation of testicular damage, which could contribute to a better understanding of fluoride-induced male reproductive toxicity.
Fluorosis is an endemic disease caused due to the chronic intake of fluoride, which alters body physiology, especially antioxidant status and lipid metabolism. There are reports which suggests that degenerative changes occur in cardiovascular system due to fluoride ingestion, may be caused due to oxidative stress. Selenium is a component of the antioxidant enzymes glutathione peroxidase and thioredoxin reductase has an antioxidant property. Hence, the present study was designed to evaluate the antioxidant effect of selenium and its ameliorative action on cardiac tissue damage of fluorotic rats. Eighteen male adult Wister rats were divided into 3 groups, 6 rats in each group. One group served as control and the other two groups as experimental control & experimental group. Both the experimental groups were given 200ppm of fluoride drinking water for 100days and only experiment group received supplement of selenium (5mg/kg body weight) which was given orally as single dose daily for another 20days and both the groups were continued to receive fluorinated drinking water during the extended period also. The control group rats received ordinary drinking water throughout the experimental period. At the end of the experimental period, the rats were sacrificed as per ethical guidelines and the cardiac tissues were harvested for histological & biochemical studies. One ml of blood was collected from retro-orbital plexuses before animals were sacrificed. Fluoride treatment significantly decreased the body weight, increased the oxidative stress, decreased glutathione levels, increased malondialdehyde levels in cardiac tissue homogenate and increased level of serum AST was observed in fluoride ingested rats. The histological scrutiny of the cardiac tissue of these rats showed degenerative changes. The result of experimental group which received oral supplementation of selenium for 20days showed the opposite of only fluoride ingested experimental control group. Here, the MDA & serum AST levels were decreased whereas GSH level was increased. These biochemical changes were supported by histological observation of the experimental rats where, the cytoarchitecture of cardiac tissues showed near normal picture. The result may suggest that dietary supplementation of selenium to animals and humans living in fluoride endemic zones may probably reduce the risk of cardiac tissue damage.
Fluorine is in the dynamic balance of two geochemical processes, enrichment and leaching, reflecting the adsorption and desorption of fluoride by clay minerals, respectively. The two geochemical processes of fluorine in soil are influenced by factors including geochemical characteristics of soil and clay minerals, pH and sanity of soil solutions, climate, grazing and agriculture activities. Main factors controlling enrichment and leaching process of fluorine in soil can be found with interaction consideration.
Territorial aggression, sexual behaviour and fertility parameters were evaluated at adulthood of male rats previously exposed to different concentrations of sodium fluoride (Na-F) at their gestation, lactation and post-weaning period till maturation. Sixty weanling male Wistar rats were received Na-F via their dams from second trimester of their pregnancy onward till weaning at 30 days of age at one of three different concentrations; 0, 50 and 100 ppm, 20 pups for each dose. Na-F was then administered in drinking water, at the same doses, to the three experimental groups throughout the course of the study till completing all investigations. Na-F treatment significantly diminished territorial aggressive behaviour parameters in adult male rats as indicated by reduced lateralization, boxing bouts, fighting as well as ventral presenting postures compared with controls. Likewise, a significant decline in sexual behaviour was also noted for Na-F-exposed rats, where latencies to first mount, intromission and ejaculation were significantly prolonged, and notably for the higher incorporated dose. Moreover, a significant decrease was evident for frequencies of mounts, intromissions and ejaculations when Na-F was given to males compared to their untreated counterparts. Higher post-ejaculatory intervals were observed with Na-F group, particularly at high dose. Compared to control group, high Na-F-treated rats displayed a significant inhibited profile of fertility as reflected in reduced number of impregnated females, implantations as well as viable fetuses, along with increased number of resorptions. Relative weights of reproductive organs were also lessened in Na-F-administered males. Histopathological examination showed degenerative changes in testes, seminal vesicles and prostate gland of Na-F-exposed males with varied degree of severity according to incorporated dose. Our study clearly signifies the adverse effect of fluoride on territorial aggression, sexual performance with inhibited fertility in adult male rats.
The toxicity of sodium fluoride (NaF) to female fertility is currently recognized; however, the mechanisms are unclear. Previously, we reported a reduction in successful pregnancy rates, ovarian atrophy and dysfunction following exposure to NaF. The purpose of this study was to elucidate the underlying molecular mechanisms. Female Sprague-Dawley rats (10 rats/group) received 100 or 200 mg/L NaF in their drinking water for 6 months or were assigned to an untreated control group. Apoptotic indices and oxidative stress indicators in blood and ovarian tissue were analyzed following sacrifice. The results confirmed the NaF-induced ovarian apoptosis, with concomitant activation of oxidative stress. Further investigations in ovarian granular cells showed that exposure to NaF activated extracellular regulated protein kinase (ERK) and c-Jun NH2 kinase (JNK), disrupting the ERK and JNK signaling pathways, while p38 and PI3K remained unchanged. These data demonstrated that oxidative stress may play a key role in NaF-induced ovarian dysfunction by activating the apoptotic ERK and JNK signaling pathways.
Fluorine, a toxic and reactive element, is widely prevalent throughout the environment and can induce toxicity when absorbed into the body. This study was to explore the possible mechanisms of developmental neurotoxicity in rats treated with different levels of sodium fluoride (NaF). The rats' intelligence, as well as changes in neuronal morphology, glucose absorption, and functional gene expression within the brain were determined using the Morris water maze test, transmission electron microscopy, small-animal magnetic resonance imaging and Positron emission tomography and computed tomography, and Western blotting techniques. We found that NaF treatment-impaired learning and memory in these rats. Furthermore, NaF caused neuronal degeneration, decreased brain glucose utilization, decreased the protein expression of glucose transporter 1 and glial fibrillary acidic protein, and increased levels of brain-derived neurotrophic factor in the rat brains. The developmental neurotoxicity of fluoride may be closely associated with low glucose utilization and neurodegenerative changes.
The toxicity and action mechanism of fluoride were reviewed in this paper. Fluoride disturbs the processes of individual growth and development at organism, organ and cell levels. Fluoride may cause malformation of embryo in individual development of animals. In addition, fluoride also possesses the toxicity effect on digestive system, skeletal system and nervous system. Finally, fluoride disturbs the activity of enzymes, and then induces the oxidative stress and cell apoptosis. Keywords-fluoride; toxicity; individual development; action mechanism
Fluoride occurs naturally in soil, water, plants and animals in trace quantities. When fluoride is ingested, some is taken up by body tissues, with long-term deposition in teeth and bones. Following the demonstration of a significant reduction in dental caries in childhood within populations exposed to higher levels of fluoride in drinking water, between 1964 and 1975 several Local Authority water fluoridation schemes were introduced in England and Wales, whereby the fluoride content was artificially increased to a level of 1ppm (1mgL−1). Although evidence continues to support the premise that fluoride in water helps protect children's teeth against caries, there are a number of potential adverse impacts, notably dental fluorosis (mottling of teeth). The situation is complicated by the fact that many individuals receive additional exposure to fluoride through the use of fluoride toothpaste, for example. Nonetheless, fluoridation of water continues to be generally regarded as a safe, simple and cost-effective public health measure to reach children most at risk and reduce the incidence of dental caries.Available evidence on risk of hip and other bone fractures suggests no effect of fluoride in water, although a small percentage change (in either direction) cannot be ruled out. There appears to be no link between water fluoridation and either cancer in general or any specific cancer type, but an updated analysis of UK data on fluoridation and cancer rates has nonetheless been recommended. Evidence for additional health outcomes suggested by some to be associated with fluoride ingestion, and on other concerns related to the chemicals that are added during the fluoridation process and indirect effects such as increased leaching of lead from pipes and aluminium from cooking utensils, is weak but the area deserves to be kept under review.
Long-term excessive fluoride intake is known to be toxic and can damage a variety of organs and tissues in the human body. However, the molecular mechanisms underlying fluoride-induced male reproductive toxicity are not well understood. In this study, we used a rat model to simulate the situations of human exposure and aimed to evaluate the roles of endoplasmic reticulum (ER) stress and inflammatory response in fluoride-induced testicular injury. Sprague-Dawley rats were administered with sodium fluoride (NaF) at 25, 50 and 100 mg/L via drinking water from pre-pregnancy to gestation, birth and finally to post-puberty. And then the testes of male offspring were studied at 8 weeks of age. Our results demonstrated that fluoride treatment increased MDA accumulation, decreased SOD activity, and enhanced germ cell apoptosis. In addition, fluoride elevated mRNA and protein levels of Glucose-regulated protein 78 (GRP78), inositol requiring ER-to-nucleus signal kinase 1 (IRE1), C/EBP homologous protein (CHOP), indicating activation of ER stress signaling. Furthermore, fluoride also induced testicular inflammation, as manifested by genes up-regulation of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), in a nuclear factor-κB (NF-κB)-dependent manner. These were associated with marked histopathological lesions including injury of spermatogonia, decrease of spermatocytes and absence of elongated spermatids, as well as severe ultrastructural abnormalities in testes. Taken together, our results provide compelling evidence that ER stress and inflammation would be novel and significant mechanisms responsible for fluoride-induced disturbance of spermatogenesis and germ cell loss in addition to oxidative stress.
The aim of this study was to investigate the effects of sodium fluoride (NaF) on female reproductive function and examine the morphology of the ovaries and uteri of rats exposed to NaF. Eighty female Sprague-Dawley (SD) rats were divided randomly into four groups of twenty: one control group and three NaF treated groups. The three NaF treated groups received 100, 150, and 200 ppm, respectively, of NaF for 6 months via their drinking water, while the control group (GC) received distilled water. The levels of follicle-stimulating hormone (FSH), luteinizing hormone (LH), testosterone (T), progesterone (P) and estradiol (E2) were measured using an enzyme-linked immunosorbent assay. Pathomorphological evaluation of the uteri and ovaries was conducted after staining with hematoxylin-eosin and immunohistochemistry. The rate of successful pregnancy in the NaF-treated groups declined in a dose-dependent manner. The concentration of reproductive hormones was significantly lower in the three NaF-treated groups, and the endometrium was damaged. The maturation of follicles was inhibited. In addition, the total number of follicles of all types was significantly lower in the NaF-treated groups. These results suggest that female reproductive function is inhibited by NaF and that exposure to NaF causes ovarian and uterine structural damage. NaF may thus significantly reduce the fertility of female rats.
In the absence of toxicological data on a chemical, the threshold of toxicological concern (TTC) approach provides a system to estimate a conservative exposure below which there is a low probability of risk for adverse health effects. The original toxicology dataset underlying the TTC was based on NOELs from repeat dose studies. Subsequently there have been several efforts to assess whether or not these limits are also protective for reproductive/developmental effects. This work expands the database of chemicals with reproductive and developmental data, presents these data in a comprehensive and transparent format and groups the chemicals according to the TTC "Cramer Class" rules. Distributions of NOAELs from each of these classes were used to assess whether the previously proposed TTC values based on repeat dose data are protective for reproductive/developmental toxicity endpoints as well. The present analysis indicates that, for each Cramer Class, the reproductive and developmental endpoints would be protected at the corresponding general TTC tiers derived by Munro et al. (1996).
High-fluoride (100 and 200 ppm) water was administered to rats orally to study the fluoride-induced changes on the thyroid hormone status, the histopathology of discrete brain regions, the acetylcholine esterase activity, and the learning and memory abilities in multigeneration rats. Significant decrease in the serum-free thyroxine (FT4) and free triiodothyronine (FT3) levels and decrease in acetylcholine esterase activity in fluoride-treated group were observed. Presence of eosinophilic Purkinje cells, degenerating neurons, decreased granular cells, and vacuolations were noted in discrete brain regions of the fluoride-treated group. In the T-maze experiments, the fluoride-treated group showed poor acquisition and retention and higher latency when compared with the control. The alterations were more profound in the third generation when compared with the first- and second-generation fluoride-treated group. Changes in the thyroid hormone levels in the present study might have imbalanced the oxidant/antioxidant system, which further led to a reduction in learning memory ability. Hence, presence of generational or cumulative effects of fluoride on the development of the offspring when it is ingested continuously through multiple generations is evident from the present study.
Since the mid 1940s, fluoride has been added to tap water in American communities in an effort to reduce the incidence of dental caries in the population. When the levels of fluoride in drinking water were tested and set, water was the only measurable source of fluoride for most communities. Now, adults and children ingest fluoride with foods and beverages prepared with fluoridated water, and they are exposed to fluoride-containing dental products. As a result, exposure to fluoride is greater than had been anticipated. In the early 1990s, the existing reproductive studies were reviewed in several reports and were considered to be inadequate to determine potential reproductive or developmental hazards. The effects of sodium fluoride ingestion at 0, 25, 100, 175 or 250 ppm in drinking water measured in rats throughout three generations are reported here. Feed and fluid consumption, body weights and clinical signs were recorded at regular intervals. Decreased fluid consumption observed at 175 and 250 ppm was attributed to decreased palatability and did not affect reproduction. No cumulative effects were observed in the three generations. Mating, fertility and survival indices were not affected. Organ-to-body-weight ratios and organ-to-brain weight ratios were not affected. Sodium fluoride up to 250 ppm did not affect reproduction in rats.
Oral administration of sodium fluoride (NaF; 40 mg/kg body weight) daily from day 6 of gestation to day 21 of lactation caused, compared with the distilled water control (group 2), significant reductions in body weight and feed consumption as well as concentration of glucose and protein in the serum of P- and F(1)-generation rats; however, sodium and potassium concentrations in the serum were significantly higher than those of the vehicle control (group 2). Administration of either vitamins C (50 mg/kg body weight/day), D (2 ng/0.2 ml olive oil/animal/day) or a combination of vitamins C+D+E along with NaF caused significant amelioration in body weight and feed consumption, as well as glucose, protein, sodium and potassium concentrations in the serum of P- and F(1)-generation rats compared with the NaF-only treated group. Withdrawal of NaF treatment during lactation caused significant amelioration in feed consumption (days 15-21 only), sodium, potassium, glucose and protein concentrations in the serum of both P- and F(1)-generation rats. Co- treatment with vitamin E (2 mg/0.2 ml olive oil/animal/day) caused significant amelioration in body weight (days 15 and 20 of gestation only), sodium, potassium, glucose (only in P-generation females) and protein (only in P-generation female) concentrations in the serum of rats than in NaF-treated rats alone. It is concluded that co-treatment with vitamins C, D and C+D+E were found more effective in ameliorating NaF-induced effects than vitamin E and withdrawal of NaF treatment during lactation.
The possible effects of multigenerational administration of sodium fluoride (NaF) via drinking water on lung tissue morphology and biochemistry and body and lung weight were investigated in second‐generation adult male rats. For this purpose we selected 45 Albino adult Wistar rats in nine cages, each of which consisted of four females and one male. Twenty‐eight pregnant rats were selected for the experiment, divided into four groups of seven rats given 1 (control group), 10, 50 and 100 mg l ⁻¹ NaF in drinking water during the gestation period. After gestation the rats had 165 pups in total. The mothers received fluoridated water during the lactation period and the offspring of the first generation had access to fluoridated water during the suckling period (21 days) and after the weaning period (30 days) until they became mature and at the start of the second part of the experiment. During this time 23 pups died and 79 female and 63 male first‐generation rats survived. These first‐generation rats were then used to obtain the second‐generation offspring in the same manner as before, which were subjected to the same treatments. At the end of 6 months the rats were sacrificed and autopsied. Serum fluoride levels and the activities of principal antioxidant enzymes were determined in lung tissue samples taken from all groups. In addition, the lung tissues were submitted for histopathological examination.
Histological findings showed alveolar congestion, alveolar cell hyperplasia and necrosis, prominent alveolar septal vessels, epithelial desquamation and macrophages in the alveolar spaces in the experimental groups. Additionally, there were inflammatory infiltrations in peribronchial, perivascular, intraparenchymal and respiratory tract lumen; intraparenchymal hyperaemic vessels; respiratory epithelial desquamation and proliferation; intraparenchymal thick valled vessels; parenchymal fibrosis; bronchiolitis; pneumonic and focal emphysematous areas. Furthermore, the lung parenchyma was observed to have a distorted appearance with loss of alveolar architecture. These histopathological findings were more pronounced for the rat groups of 50 and 100 mg l ⁻¹ fluoride. No significant histopathological changes were observed in the rats of the control group.
The increased activities of superoxide dismutase (SOD) and reduced glutathione peroxidase (GSH‐Px) and the decreased activity of catalase (CAT) in the lung tissues with 10 mg l ⁻¹ fluoride might indicate activation of the antioxidant defence mechanism. The decrease in SOD, GSH‐Px and CAT activities with 50 and 100 mg l ⁻¹ fluoride and the increase in thiobarbituric acid‐reactive substance levels might be related to oxidative damage that occurred in the lung.
This multigenerational evaluation of the long‐term effect of different doses of fluoride intake through drinking water on lung damage shows that the lung tissues were damaged, there was emphysema and inflammation of lung parenchyma associated with loss of alveolar architecture and the degree of lung damage seemed to correlate with the increased dosage of fluoride. A similar relationship was observed between the degree of lung damage, body and lung weight and serum fluoride levels according to the fluoride dose. Therefore, these results contribute to a better understanding of chronic fluoride toxicity in lung tissue of second‐generation rats, especially via drinking water, and the biochemical findings were in agreement with histological observations. In addition, increased fluoride concentration did not affect reproduction or the number of pups dying but the body weight and lung weight ratios were affected by the high dose of fluoride in a dose‐related pattern. Copyright © 2003 John Wiley & Sons, Ltd.
The objective of these studies was to evaluate the reproductive and developmental toxicity of a commercial fluoroalkylethanol mixture, which is an intermediate in the production of fluorotelomers. The test substance was administered daily by gavage to Sprague-Dawley rats as a suspension in 0.5% aqueous methylcellulose. In a one-generation reproductive toxicity study, rats (20 per sex per group) were given dosages of 0, 25, 100, or 250 mg kg(-1) day(-1) for a period of 74 days prior to cohabitation, and during mating, gestation, and lactation. Body weights, feed consumption, clinical signs, gross pathology, sperm parameters, estrous cyclicity, and reproductive performance were evaluated for the P1 generation. The F1 offspring were.evaluated during the lactation period for growth and survival and given a gross pathology examination at weaning. A subset of the offspring were retained; body weights, feed consumption, clinical signs, and age at onset of vaginal opening and preputial separation were evaluated, and gross pathology was performed on postnatal day 60. In the developmental toxicity study, groups of time-mated Sprague-Dawley female rats were given the test substance as a suspension in 0.5% aqueous methylcellulose at daily dosages of 0, 50, 200, or 500 mg kg(-1) day(-1) by gavage on gestation days 6-20. During the in-life portion of the study, growth parameters and clinical observations were made. On gestation day 21, dams were euthanized, and the thoracic and abdominal viscera were examined. The uterine contents were removed and examined, and fetuses were evaluated for any alterations. In the reproduction study, litter size at birth, number of live pups per litter on day 0 and 4 of lactation, and pup weights during lactation were reduced in groups administered > or =100 mg kg(-1) day(-1). No other reproductive parameters were affected. There were no adverse reproductive effects observed at 25 mg kg(-1) day(-1). In the developmental toxicity study, reduced maternal body weight parameters, increased perineal fur staining, and increased fetal skeletal alterations were observed at 500 mg kg(-1) day(-1). There was no maternal or developmental toxicity at 50 or 200 mg kg(-1) day(-1). Under the conditions of the studies, the no-observed adverse effect levels for this mixture were 25 mg kg(-1) day(-1) for subchronic toxicity and reproductive parameters and 200 mg kg(-1) day(-1) for developmental toxicity end points. No functional reproductive or developmental effects were observed at dose levels that did not adversely affect adult animals.
Free ionic fluoride concentrations were measured in the maternal blood plasma, cord blood plasma and the urine of pregnant and age matched nonpregnant women in two groups of subjects. Group 1 included females who had been living in endemic fluorosis areas with the mean intake of 21 mg/day of fluoride from drinking water and Group 2 consisted of women from non-endemic areas with the mean daily intake of 1.5 mg of fluoride from drinking water. The ionized fluoride concentrations in the maternal plasma and the urine decreased during the course of pregnancy; they were at their lowest at 36 weeks of gestation. In the nonpregnant controls these values remained largely unchanged. In the maternal and cord blood plasm obtained at the time of cesarean section the fluoride concentrations were similar and did not support the concept of a placental fluoride barrier. The higher fluoride content in the plasma and urine of the women in the endemic group (10 ppm F - in drinking water) indicated a direct relationship of these values to the amount of fluoride ingested. The fall in the maternal plasma and urine fluoride concentration during pregnancy is believed to be due to increasing accumulation of fluoride in the rapidly mineralizing fetal skeleton.
Sodium fluoride (NaF; Cas No. 7681-49-4) is used in fluoridating municipal water supplies, resulting in chronic exposure of millions of people worldwide. Because of a lack of pertinent developmental toxicity studies in the literature, sodium fluoride was administeredad libitumin deionized/filtered drinking water (to mimic human exposure) to Sprague–Dawley-derived rats (26/group) on Gestation Days (GD) 6 through 15 at levels of 0, 50, 150, or 300 ppm and New Zealand White rabbits (26/group) on GD 6 through 19 at levels of 0, 100, 200, or 400 ppm. Higher concentrations via drinking water were not practicable due to the poor palatability of sodium fluoride. Drinking water (vehicle) contained less than 0.6 ppm sodium fluoride (limit of detection) and sodium fluoride content of the feed was 12.4 ppm fluoride (rats) and 15.6 ppm fluoride (rabbits). Maternal food, water, body weights, and clinical signs were recorded at regular intervals throughout these studies. Animals were killed on GD 20 (rats) or 30 (rabbits) and examined for implant status, fetal weight, sex, and morphological development. In the high-dose group of both studies there was an initial decreased maternal body weight gain which recovered over time and a decreased water consumption—attributed to decreased palatability. No clear clinical signs of toxicity were observed. Maternal exposure to sodium fluoride during organogenesis did not significantly affect the frequency of postimplantation loss, mean fetal body weight/litter, or external, visceral or skeletal malformations in either the rat or the rabbit. The NOAEL for maternal toxicity was 150 ppm sodium fluoride in drinking water (∼18 mg/kg/day) for rats, and 200 ppm (∼18 mg/kg/day) for rabbits. The NOAEL for developmental toxicity was ≥300 ppm sodium fluoride (∼27 mg/kg/day) for rats and ≥400 ppm (∼29 mg/kg/day) for rabbits administered during organogenesis in drinking water. The total exposure to fluoride (mg F/kg body weight/day from food and drinking water combined) in the mid- and high-dose groups for both species was >100-fold higher than the range at 0.014–0.08 mg F/kg/day estimated for a 70-kg person from food and fluoridated (1 ppm) drinking water.
Procedures are given in the report for determining statistically whether the highest observation, or the lowest observation, or the highest and lowest observations, or the two highest observations, or the two lowest observations, or perhaps more of the observations in the sample may be considered to be outlying observations or discrepant values. Statistical tests of significance are useful in this connection either in the absence of assignable physical causes or to support a practical judgement that some of the experimental observations are aberrant. Both the statistical formulae and illustrative applications of the procedures to practical examples are given, thus representing a rather complete treatment of significance tests for outliers in single univariate samples.
A selective, progressive method for staining the skeleton in cleared specimens, developed with rat material. Fix in 95% alcohol for at least 48 to 96 hrs. Even longer fixation is desirable. Then place in a 1% solution of KOH until the bones are clearly visible through the surrounding tissues. Transfer directly to a dilute solution of alizarin in KOH, one part alizarin to 10,000 parts of 1% KOH. Allow the stain to act until the desired intensity is attained. Fresh stain may be added if necessary. Complete the clearing process, (1) in Mall's solution, water 79 parts, glycerine 20 parts and KOH 1 part; (2) in increased concentrations of glycerine. Store in pure glycerine. The success of the method depends on obtaining the proper degree of clearing before staining. If the specimen is insufficiently cleared, a general staining of all tissues usually occurs.
The use of transformations to stabilize the variance of binomial or Poisson data is familiar(Anscombe [1], Bartlett [2, 3], Curtiss [4], Eisenhart [5]). The comparison of transformed binomial or Poisson data with percentage points of the normal distribution to make approximate significance tests or to set approximate confidence intervals is less familiar. Mosteller and Tukey [6] have recently made a graphical application of a transformation related to the square-root transformation for such purposes, where the use of "binomial probability paper" avoids all computation. We report here on an empirical study of a number of approximations, some intended for significance and confidence work and others for variance stabilization. For significance testing and the setting of confidence limits, we should like to use the normal deviate $K$ exceeded with the same probability as the number of successes $x$ from $n$ in a binomial distribution with expectation $np$, which is defined by $\frac{1}{2\pi} \int^K_{-\infty} e^{-\frac{1}{2}t^2} dt = \operatorname{Prob} \{x \leq k |mid \operatorname{binomial}, n, p\}.$ The most useful approximations to $K$ that we can propose here are $N$ (very simple), $N^+$ (accurate near the usual percentage points), and $N^{\ast\ast}$ (quite accurate generally), where $N = 2 (\sqrt{(k + 1)q} - \sqrt{(n - k)p)}.$ (This is the approximation used with binomial probability paper.) $N^+ = N + \frac{N + 2p - 1}{12\sqrt{E}},\quad E = \text{lesser of} np \text{and} nq, N^\ast = N + \frac{(N - 2)(N + 2)}{12} \big(\frac{1}{\sqrt{np + 1}} - \frac{1}{\sqrt{nq + 1}}\big), N^{\ast\ast} = N^\ast + \frac{N^\ast + 2p - 1}{12 \sqrt{E}}\cdot\quad E = \text{lesser of} np \text{and} nq.$ For variance stabilization, the averaged angular transformation $\sin^{-1}\sqrt{\frac{x}{n + 1}} + \sin^{-1} \sqrt{\frac{x + 1}{n+1}}$ has variance within $\pm 6%$ of $\frac{1}{n + \frac{1}{2}} \text{(angles in radians)}, \frac{821}{n + \frac{1}{2}} \text{(angles in degrees)},$ for almost all cases where $np \geq 1$. In the Poisson case, this simplifies to using $\sqrt{x} + \sqrt{x + 1}$ as having variance 1.
Until now, transplacental passage of fluoride could only be checked during delivery. Recent developments in fetal blood sampling techniques in utero have made it possible to study its passage in pregnancy. Two tablets of 2.212 mg of sodium fluoride (Zymafluor) were given to 11 women with an average age of 27 1/2 years whose pregnancies on an average had lasted 22 weeks. They were having prenatal diagnosis by ultrasound guided fetal blood sampling in any case. The levels of fluoride were measured by the use of a specific electrode before the mother took fluoride and 40 minutes after she had taken it in both maternal and fetal blood samples. The results were compared with a controlled group of 11 pregnant women with similar characteristics: maternal age, duration of pregnancy and basal maternal fluoride levels. Fetal blood levels of fluorides in mothers who had taken sodium fluoride was statistically higher than in the controlled group (2.6 mumol/l and less than 1 mumol/l); this demonstrates in a statistically significant way that fluoride passes across the placenta in the fifth and sixth months of pregnancy which is the time when the milk teeth start to develop in the uterus.
Fluoride concentrations were determined in plasma of 50 pregnant women, 44 samples of amniotic fluid and fetal cord blood of 29 fetuses at various stages of normal pregnancies, from an area with a relatively low water fluoride (less than 0.5 ppm) content. The mean concentrations of fluoride from maternal plasma, cord plasma and amniotic fluid (+/- S.D.) were 0.033 +/- 0.003, 0.028 +/- 0.005 and 0.017 +/- 0.003 ppm, respectively. Maternal and fetal plasma fluoride concentrations did not differ significantly. In the older age group fetal cord plasma fluoride concentration was significantly lower than maternal plasma levels (0.012 +/- 0.08 ppm vs. 0.023 +/- 0.001, respectively; p less than 0.05). Amniotic fluid fluoride levels were significantly higher at term than in midtrimester pregnancy, 0.017 +/- 0.0018 vs. 0.010 +/- 0.009 ppm (P less than 0.05), respectively. This higher concentration may imply higher fetal urinary excretion of fluoride at term due to the lower sequestration of fluoride as the process of bone calcification is more complete.
Fluoride passes the placenta in limited amounts and may bestow caries resistance upon developing teeth. In a recent report, offspring of rats fed a diet containing sodium pentafluorostannite during gestation were found to have reduced caries incidence compared to offspring of rats fed sodium fluoride. In order to determine whether this observation was related to increased placental transfer of fluoride, pregnant rats were fed diets containing 50, 100, and 200 ppm fluoride or equivalent, from the following salts: sodium pentafluorostannite, so dium pentachlorostannite, sodium fluoride, stannous fluoride, or a mixture of sodium and stannous fluorides. On day 20 of gestation, fetuses and placentas were obtained for analyses. The average fluoride levels of the fetuses from rats fed 50, 100, and 200 ppm fluoride diets ranged from 0.6 to 0.9 ppm, 1.1 to 2.0 ppm, and 3.0 to 4.0 ppm fluoride, respectively. None of the salts appeared to have a significantly different efficiency of placental transfer of fluoride. Fetal tin values were elevated when the maternal diet contained tin salts, but without apparent relation to dietary tin level. J. Nutr. 101: 525-532, 1971.
Despite the chronic exposure of the US population to fluoridated drinking water since the 1940s, existing studies have been judged inadequate to determine any potential reproductive or developmental hazard. This study was conducted to determine the effects of sodium fluoride (NaF) on foetal development. Sperm-positive female rats were given 0, 10, 25, 100, 175 or 250 ppm NaF daily throughout gestation. They were dosed by drinking water to mimic human exposure to fluoridated water. No dose-related behavioural changes or maternal clinical signs were noted. Fluid consumption by females in the 175- and 250-ppm groups was significantly less than that of the control females. Because of this decreased fluid consumption, the daily amount of NaF ingested (0, 1.4, 3.9, 15.6, 24.7 and 25.1 mg/kg body weight) was less than expected at the two high levels. Feed consumption decreased significantly at 250 ppm, and body weights of pregnant females reflected feed consumption trends. The mean number of viable foetuses per female in all treated groups was similar to that of the control group. The significant decrease in the mean number of implants per litter in the 250-ppm group is probably linked to the lower mean number of corpora lutea in this group. The occurrence of in utero deaths was similar in the control and treated groups. Foetal growth (in terms of foetal body weight and crown-rump length) was not affected by NaF, despite the fact that the dams in the 250-ppm group ate significantly less feed and drank significantly less fluid. There was no dose-related increase in the number of external anomalies in foetuses due to NaF ingestion. At the doses given, NaF had no effect on the development of specific bones, including sternebrae. A significant increase was seen in the average number of foetuses with three or more skeletal variations in the 250-ppm group; the number of litters with foetuses with three or more skeletal variations was increased in the 250-ppm group also, but the increase was not significant. There was no dose-related effect of NaF on the incidence of soft tissue variations.
The potential of sodium fluoride (NaF) to affect spermatogenesis and endocrine function was assessed in P and F1 generation male rats. Male and female experimental rats received sodium fluoride in their drinking water at one of four concentrations (25, 100, 175, 250 ppm). P generation male and female rats were exposed to sodium fluoride in their drinking water for 10 wk and then males were mated to females within the same treatment groups. Reproductive tissues were collected from P generation male rats after approximately 14 wk of treatment. Pregnant females (P) were exposed to sodium fluoride via their drinking water through gestation and lactation. F1 generation weanling male rats remained within the same treatment groups as their parents. F1 generation male rats were exposed to sodium fluoride in their drinking water for 14 wk, at which time reproductive tissues were collected. Dose-related effects were not observed within the P and F1 treatment groups in testis weights, prostate/seminal vesicle weights, non-reproductive organ weights, testicular spermatid counts, sperm production per gram of testis per day, sperm production per gram of testis, LH, FSH or serum testosterone concentrations. Histological changes were not observed in testicular tissues from either the P or F1 generation. We conclude that prolonged exposure to sodium fluoride in drinking water at the doses administered in this study does not adversely affect spermatogenesis or endocrine function in the P and F1 generation male rats.
This study provides quantitative information on the effect of sodium fluoride (NaF) on the testes of F1 generation male rats exposed in utero and during lactation to NaF at one of four concentrations (25, 100, 175, 250 ppm). At weaning, the F1 generation males were exposed to NaF in their drinking water for 14 weeks, after which time testicular tissues were perfusion-fixed with glutaraldehyde and observed after being embedded in plastic. The seminiferous tubules comprised 89%, 87%, 88%, 88% and 88% of the total testis volume while the interstitial space occupied 9.3%, 11.2%, 10.2%, 9.8% and 9.9% of the total testis volume for the 0, 25, 100, 175 and 250 ppm NaF treatment groups, respectively. Statistically significant differences between control and NaF-treated rats were not observed with respect to absolute volume of the seminiferous tubules, interstitial space, Leydig cells, blood vessels boundary layer, lymphatic space, macrophages, tubular lumen or absolute tubular length and absolute tubular surface area, mean Sertoli cell nucleoli number per tubular cross-section, mean seminiferous tubule diameter and the mean height of the seminiferous epithelium. A statistically significant decrease in the absolute volume and volume percent of the lymphatic endothelium was observed in the 175 and 250 ppm NaF-treated groups and in the testicular capsule in the 100 ppm NaF-treated groups. The significance of this finding is unknown at the present time. Overall, the quantitative information obtained suggests that exposure to NaF at the doses used in the present study does not adversely affect testis structure or spermatogenesis in the rat.
Since the mid 1940s, fluoride has been added to tap water in American communities in an effort to reduce the incidence of dental caries in the population. When the levels of fluoride in drinking water were tested and set, water was the only measurable source of fluoride for most communities. Now, adults and children ingest fluoride with foods and beverages prepared with fluoridated water, and they are exposed to fluoride-containing dental products. As a result, exposure to fluoride is greater than had been anticipated. In the early 1990s, the existing reproductive studies were reviewed in several reports and were considered to be inadequate to determine potential reproductive or developmental hazards. The effects of sodium fluoride ingestion at 0, 25, 100, 175 or 250 ppm in drinking water measured in rats throughout three generations are reported here. Feed and fluid consumption, body weights and clinical signs were recorded at regular intervals. Decreased fluid consumption observed at 175 and 250 ppm was attributed to decreased palatability and did not affect reproduction. No cumulative effects were observed in the three generations. Mating, fertility and survival indices were not affected. Organ-to-body-weight ratios and organ-to-brain weight ratios were not affected. Sodium fluoride up to 250 ppm did not affect reproduction in rats.
Passage transplacentaire du fluor; Etude in utero
- Forestier