CONCLUSIONS
- Extensive studies over the past 50 years have established that individuals whose
drinking water is fluoridated show a reduction in dental caries. Although the comparative
degree of measurable benefit has been reduced recently as other fluoride sources have
become available in non-fluoridated areas, the benefits of water fluoridation are still
clearly evident. Fewer caries are associated with fewer abscesses and extractions of teeth
and with improved health. The health and economic benefits of water fluoridation accrue to
individuals of all ages and socioeconomic groups, especially to poor children.
- Since the addition of fluoride to drinking water in the 1940's, other sources of fluoride
have become available, including toothpastes, mouth rinses, and fluoride dietary
supplements. These sources of fluoride also have proven to be effective in preventing
dental caries.
- Estimates developed for this report show that fluoride exposure is generally greater in
fluoridated areas; however, there is fluoride exposure in both fluoridated and
non-fluoridated areas because of the variety of fluoride sources besides drinking water.
Beverages and foods are sources of fluoride, especially if they have been prepared with
fluoridated drinking water.
- Optimal fluoridation of drinking water does not pose a detectable cancer risk to humans
as evidenced by extensive human epidemiological data available to date, including the new
studies prepared for this report. While the presence of fluoride in sources other than
drinking water reduces the ability to discriminate between exposure in fluoridated as
compared to non-fluoridated communizes, no trends in cancer risk, including the risk of
osteosarcoma, were attributed to the introduction of fluoride into drinking water in these
new studies. During two time periods, 1973-1980 and 1981-1987, there was an unexplained
increase of osteosarcoma in males under age 20. The reason for this increase remains to be
clarified, but an extensive analysis reveals that it is unrelated to the introduction and
duration of fluoridation.
- There are two methodologically acceptable studies of the carcinogenicity of fluoride in
experimental animals. The Procter and Gamble study did not find any significant evidence
of carcinogenicity in rats and mice of either sex. In the NTP study there was no evidence
of carcinogenicity in mice and in female rats. Male rats showed "equivocal"
evidence of carcinogenicity based on the finding of a small number of osteosarcomas.
"Equivocal" evidence is defined by NTP as "...interpreted as showing a
marginal increase in neoplasms that may be chemically related" (HHS, 1990). Taken
together, the data available at this time from these two animal studies fail to establish
an association between fluoride and cancer.
- By comparison with the 1940's, the total prevalence of dental fluorosis has increased in
non-fluoridated areas and may have increased in optimally fluoridated areas. Such
increases in dental fluorosis in a population signify that total fluoride exposures have
increased and may be more than are necessary to prevent dental caries. For this reason,
prudent public health practice dictates the reduction of unnecessary and inappropriate
fluoride exposure.
- In the 1940s, drinking water and food were the major sources of fluoride exposure. Since
then, additional sources of fluoride have become available through the introduction of
fluoride containing dental products. Although the use of these products is likely
responsible for some of the declines in caries scores, the inappropriate use of these
products has also likely contributed to the observed increases in the prevalence of very
mild and mild forms of dental fluorosis.
- Further epidemiological studies are required to determine whether or not an association
exists between various levels of fluoride in drinking water and bone fractures.
- Crippling skeletal fluorosis is not a public health problem in the United States, as
evidenced by the reports of only five cases in 30 years. Crippling skeletal fluorosis, a
chronic bone and joint disease associated with extended exposure to high levels of
fluoride, has been more prevalent in some regions outside the United States.
- Well-controlled studies have not demonstrated a beneficial effect of the use of high
doses of fluoride in reducing osteoporosis and related bone fractures.
- Genotoxicity studies of fluoride, which are highly dependent on the methods used, often
show contradictory findings. The most consistent finding is that fluoride has not been
shown to be mutagenic in standard tests in bacteria (Ames Test). In some studies with
different methodologies, fluoride has been reported to induce mutations and chromosome
aberrations in cultured rodent and human cells. The genotoxicity of fluoride in humans and
animals is unresolved despite numerous studies.
- Chronic low level fluoride exposure is nor associated with birth defects. Studies also
fail to establish an association between fluoride and Down Syndrome.
- There is no indication that chronic low level fluoride exposure of normal individuals
presents a problem in other organ systems, such as the gastrointestinal, the
genitourinary, and the respiratory systems. The effects of fluoride on the reproductive
system merit further investigation in animal and human studies.
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