Abstract
In an effort to examine the effect of exposure to sodium fluoride on the incidence of bone tumors induced by ionizing radiation, the femoral-tibial joint of the left hind limb of 100 male F344 rats was irradiated with 3000 R from a 137Cs source and the animals divided into two groups of 50. One group was then administered drinking water containing 250 ppm sodium fluoride for two years while the other group received plain deionized water. Two additional groups of 50 male F344 rats (not exposed to radiation) received drinking water containing 250 ppm sodium fluoride (113 ppm fluoride ion), or plain deionized water for two years. Survival, mean body weights, food and water consumption of all groups was comparable throughout the two year study duration. Bone fluoride analysis conducted at the end of the study revealed significant accumulation of fluoride in the bones of groups of rats exposed to sodium fluoride. Exposure to irradiation, sodium fluoride, or both irradiation and sodium fluoride was not associated with an increase in bone tumors or other neoplastic lesions. Non-neoplastic lesions of incisor teeth including ameloblast and odontoblast degeneration and malformation of enamel and dentine, were increased in groups exposed to sodium fluoride.
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Results and conclusions of the National Toxicology Program's rodent carcinogenicity studies with sodium fluoride.
The US National Toxicology Program (NTP) has conducted toxicity and carcinogenicity studies with sodium fluoride administered in the drinking water to F344/N rats and B6C3F1 mice. The drinking water concentrations used in the 2-year studies were 0, 25, 100, or 175 ppm sodium fluoride (equivalent to 0, 11, 45 or
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Clastogenic activity of sodium fluoride to rat vertebral body-derived cells in culture
The US National Toxicology Program has shown equivocal evidence of carcinogenic activity of sodium fluoride (NaF) in male F344/N rats based on the occurrence of five osteosarcomas in treated animals. In the study the osteosarcomas developed mainly in the rat vertebrae. To provide a possible mechanistic basis for the observed
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Drinking water fluoridation and osteosarcoma incidence on the island of Ireland
The incidence of osteosarcoma in Northern Ireland was compared with that in the Republic of Ireland to establish if differences in incidence between the two regions could be related to their different drinking water fluoridation policies. Data from the Northern Ireland Cancer Registry (NICR) and the National Cancer Registry of
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International trends in the incidence of bone cancer are not related to drinking water fluoridation
BACKGROUND: Because osteosarcomas may develop in rats exposed to fluoridated water, water fluoridation might pose a cancer risk to humans. METHODS: A time trend analysis of the cumulative risk (CR) of bone cancer for the period 1958-1987 for 40 cancer registry areas showed an increased risk for young males in
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Revisiting the fluoride-osteosarcoma connection in the context of Elise Bassin's findings: part 2
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Fluoride & Osteosarcoma: A Timeline
Several human epidemiological studies have found an association between fluoride in drinking water and the occurrence of osteosarcoma (bone cancer) in young males. These studies are consistent with the National Toxicology Program's (NTP) cancer bioassay which found that fluoride-treated male rats had an dose-dependent increase in osteosarcoma. Although a number of studies have failed to detect an association between fluoride and osteosarcoma, none of these studies have measured the risk of fluoride at specific windows in time, which based on recent results, is the critical question with respect to fluoride and osteosarcoma.
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Fluoride's Mutagenicity: In vitro Studies
According to the National Toxicology Program, "the preponderance of evidence" from laboratory "in vitro" studies indicate that fluoride is a mutagenic compound. Many substances which are mutagens, are also carcinogens (i.e. they can cause cancer). As is typical for in vitro studies, the concentrations of fluoride that have generally been tested
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Fluoride/Osteosarcoma Link Is Biologically Plausible
The "biological plausiblility" of a fluoride-osteosarcoma link is widely acknowledged in the scientific literature. The biological plausibility centers around three facts: 1) Bone is the principal site of fluoride accumulation, particularly during the growth spurts of childhood; 2) Fluoride is a mutagen when present at sufficient concentrations, and 3) Fluoride can stimulate the proliferation of osteoblasts (bone-forming cells).
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NTP Bioassay on Fluoride/Cancer (1990)
In 1977, the U.S. Congress requested that animal studies be conducted to determine if fluoride can cause cancer. The result of the Congressional request was an extensive animal study conducted in the 1980s by the National Toxicology Program (NTP) and published in 1990. The main finding of NTP's study was a dose-dependent increase in osteosarcoma (bone cancer) among the fluoride-treated male rats.
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Fluoride's Mutagenicity: In vivo Studies
Consistent with dozens of in vitro studies, a number of in vivo studies, in both humans and animals, have found evidence of fluoride-induced genetic damage. In particular, research on humans exposed to high levels of fluoride have found increased levels of "sister chromatid exchange" (SCE). As noted in one study: "In
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