Health Effects of Ingested Fluoride (1993) / Chapter Skim
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7 CARCINOGENICITY OF FLUORIDE
7 CARCINOGENICITY OF FLUORIDE
Pages 109-124
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From page 109... ...
The strengths and limitations of such ecological studies are addressed in Chapter 3. Because of the continuing importance of the question of fluoride in drinking water and human cancer, the relevant scientific literature has been exhaustively reviewed by several independent expert panels of epidemiologists.
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From page 110... ...
All the expert panels noted the relative strengths and weaknesses of the correlation studies. The expert pane} reviews generally agree that available data provide no credible evidence for an association between either naturally occurring fluoride or added fluoride in drinking water and risk of human cancer.
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From page 111... ...
The study was restricted! to the white population to avoid confounding by racial variations in cancer mortality rates.
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From page 112... ...
An ecological study in seven central New Jersey counties observed a higher rate of osteosarcoma in fluoridated communities than in nonfluoridated communities in 1979-1987 (a risk ratio of 3.4 among males under 20 years of age)
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From page 113... ...
Because bone cancer is rare, the cumulative risk among people 10-29 years of age or 0-74 years of age was used to examine time trends. Significant increases in the cumulative risk of bone cancer were noted primarily among young males in some registry areas in the United States; significant decreases in lifetime risk were noted among both sexes in Europe.
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From page 114... ...
female mice P&G study Male and Diet 4, 10, 25 Negative (Maurer et al., female rats mg/kg 1990) P&G study Male and Diet 4, 10, 25 Observation of (Maurer et al., female mice mg/kg osteomas in press)
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From page 115... ...
showed that low concentrations of sodium fluoride can increase the rate of growth of transplanted mammary adenocarcinomas in DBA mice. In the study, sodium fluoride was added to the tumor tissue suspension before transplantation, to the drinking water of the host animals after transplantation, or by subJermal injection after transplantation.
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From page 116... ...
exposed white Swiss mice of the Charles River strain (Card) to fluoride at 10 mg/L (administered as sodium fluoride)
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From page 117... ...
NTP considered those data "equivocal evidence of carcinogenic activity" in male rats, and "no evidence of carcinogenicity" in female rats or in male or female mice. The subcommittee felt that the study was generally well conducted in accordance with current bioassay standards ant]
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From page 118... ...
Under the exposure conditions imposed in both studies (continuous exposure to fluoride in water or feed) , fluoride concentration in bone represents the most reliable indicator of the total body burden of fluoride.
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From page 119... ...
in the NTP study. · It is important to evaluate the NTP tingling of equivocal evidence of carcinogenic activity in male rats in the context of other studies.
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From page 120... ...
The subcommittee believes that the most obvious explanation for the increased incidence of osteomas in mice is that the dose in the P&G study (based on bone fluoride concentrations) was more than twice as high as the dose in the NTP study (Table 7-4)
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From page 121... ...
Unfortunately, reliable plasma fluoride values are not available from the NTP study. Suppose that, on the basis of the results of the NTP study, fluoride induces osteosarcoma in male rats at concentrations of approximately 5,300 ppm in bone ash.
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From page 122... ...
That suggests that the male rat osteosarcomas observed in the NTP study were not related to fluoride exposure. The subcommittee concluded that the increased incidence of osteomas in male and female mice in the P&G study is most likely related to fluoride, although the presence of a contaminating retrovirus was considered a confounding factor.
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From page 123... ...
The subcommittee therefore recommends conducting one or more highly focused, carefully clesigned analytical studies (case control or cohort) of the cancer sites that are most highly suspect, based on data from animal studies and the few suggestions of a carcinogenic effect reported in the epidemiological literature.
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