Order Code RL33280
CRS Report for Congress
Received through the CRS Web
Fluoride in Drinking Water: A Review of
Fluoridation and Regulation Issues
February 22, 2006
Mary Tiemann
Specialist in Environmental Policy
Resources, Science, and Industry Division
Congressional Research Service ˜ The Library of Congress

---

Fluoride in Drinking Water: A Review of Fluoridation
and Regulation Issues
Summary
According to the Centers for Disease Control and Prevention (CDC), 67% of the
246 million people in the United States who receive their water from a public water
system received fluoridated water in 2000. One of the CDC’s national health goals
is to increase the proportion of the U.S. population served by community water
systems with “optimally” fluoridated drinking water to 75% by 2010. The decision
to add fluoride to a water supply is made by local or state governments. The U.S.
Public Health Service (PHS) has recommended an optimal fluoridation level in the
range of 0.7 to 1.2 milligrams per liter (mg/L) for the prevention of tooth decay.
The fluoridation of drinking water often generates both strong support and
opposition within communities. This practice is controversial because fluoride has
been found to have beneficial effects at low levels and is intentionally added to many
public water supplies; however, at higher concentrations, it is known to have toxic
effects. Fluoridation opponents have expressed concern regarding potential adverse
health effects of exposure to fluoride, and some view the practice as an undemocratic
infringement on individual freedom. The medical and public health communities
generally have recommended water fluoridation, citing it as a safe, effective, and
equitable way to provide dental health protection community-wide.
The use of dental products containing fluoride (such as toothpaste and rinses)
has increased significantly since the PHS recommended optimal levels for water
fluoridation, and many people now may be exposed to more fluoride than had been
anticipated. Consequently, questions have emerged as to whether current water
fluoridation practices and levels offer the most appropriate ways to provide the
expected beneficial effects of fluoride while avoiding adverse effects (primarily tooth
mottling or dental fluorosis) that may result from exposure to too much fluoride.
Moreover, research gaps and scientific uncertainty regarding the health effects of
long-term exposure to higher levels of fluoride add controversy to decisions
regarding drinking water fluoridation.
Although fluoride is added to water to strengthen teeth, some communities must
treat their water to remove excess amounts of naturally occurring fluoride. The
Environmental Protection Agency (EPA) regulates the amount of fluoride that may
be present in public drinking water supplies to protect against fluoride’s adverse
health effects. In 1986, EPA issued a drinking water regulation for fluoride that
includes an enforceable standard of 4 mg/L to protect against adverse effects on bone
structure (skeletal fluorosis). EPA acknowledged that the standard did not protect
infants and young children against mild or moderate dental fluorosis, which is
considered a cosmetic effect rather than a health effect. To address concerns, EPA
included in the regulation a secondary (advisory) standard of 2 mg/L to protect
children against dental fluorosis and adverse health effects. Currently, EPA is
reviewing the fluoride regulation and has asked the National Academy of Sciences
(NAS) to assess the currently available health and toxicity data for fluoride. The NAS
study may resolve some of the questions regarding the risks and benefits of exposure
to fluoride in drinking water. This report will be updated as warranted.

---

Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Questions About the Safety and Benefits of Fluoridation . . . . . . . . . . . . . . . 4
Dental Fluorosis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Health Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Efficacy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Other Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Regulation of Fluoride in Drinking Water . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

---

Fluoride in Drinking Water: Fluoridation and
Regulation Issues
Introduction
The fluoridation of drinking water often generates both strong support and
opposition within communities. The decision to fluoridate a water supply is made by
the state or local municipality and is not mandated by any federal agency. Opponents
have expressed concern regarding potential adverse health effects of exposure to
fluoride, and some view the practice as an undemocratic infringement on individual
freedom. The medical and public health communities generally recommend water
fluoridation, citing it as a safe, effective, and equitable way to provide dental health
protection community-wide.
With the increased use of products containing fluoride, such as toothpaste and
rinses, questions have emerged as to whether current fluoridation practices and levels
offer the most appropriate way to provide the beneficial effects of fluoride while
avoiding adverse effects (such as tooth mottling or dental fluorosis) that can result
from exposure to too much fluoride. Moreover, research gaps regarding the potential
health effects of long-term exposure to higher levels of fluoride add controversy to
decisions regarding water fluoridation.
Although many communities add fluoride to drinking water to strengthen teeth,
some communities must treat their water to remove excess amounts of fluoride,
which is often present naturally in water. The Environmental Protection Agency
(EPA) regulates the amount of fluoride that may be present in public drinking water
supplies to protect against fluoride’s adverse health effects.
This report discusses the documented benefits and potential adverse effects
associated with the fluoridation of drinking water supplies. It also discusses the
regulation of fluoride in drinking water to protect against adverse health effects from
exposure to higher levels of fluoride, and it reviews the status of federal efforts to
update the health risk assessment for fluoride. The following review of issues related
to fluoride in drinking water presents information from research published in peer-
reviewed scientific journals, reports and statements of federal agencies (including the
Centers for Disease Control and Prevention [CDC] and the U.S. Public Health
Service [PHS]) and the World Health Organization, studies by the National Research
Council of the National Academy of Sciences, and other sources.
Background
Fluoride is a naturally occurring substance and is present in virtually all water,
usually at very low levels. Higher concentrations of naturally occurring fluoride often

---

CRS-2
are associated with well water, where fluoride has dissolved from the rock formations
into the groundwater.1 Communities began fluoridating water supplies in the 1940s,
after scientists discovered that higher levels of fluoride in a community water supply
were associated with fewer dental caries (cavities) among the residents.2
In 2004, the Surgeon General reported that more than 170 million (67%) of the
people in the United States who received their water from a public water system
received fluoridated water.3 This represented a 5% increase from 1992, when 62%
of individuals served by public water systems were provided with fluoridated water.4
Many public health agencies and professional health organizations advocate the
addition of a small amount of fluoride to drinking water to help strengthen teeth and
prevent dental caries. Although this practice has been controversial in some
communities, the CDC, the American Medical Association, the American Dental
Association (ADA), the American Academy of Pediatric Dentistry, and others
recommend fluoridation of public water supplies as an effective way to protect dental
health. This approach is advocated for its ability to provide community-wide
benefits, particularly in poorer communities where children may be less likely to
receive adequate dental care.5
The CDC considers the reduction in tooth decay from fluoridation one of the top
public health achievements of the 20th Century.6 In 2002, the CDC reported that
[d]uring the second half of the 20th century, a major decline in the prevalence and
severity of dental caries resulted from the identification of fluoride as an
effective method of preventing caries. Fluoridation of the public water supply is
the most equitable, cost-effective, and cost-saving method of delivering fluoride
to the community.7
1 Fluoride also occurs in many foods, including meat, potatoes, fish, sugar, milk, and
legumes. The amount in brewed tea ranges from 1 to 6 milligrams per liter (mg/L),
depending on brewing strength and time. Also, fluorides are used industrially and may be
present in the environment as a result of inadequate pollution control.
2 National Cancer Institute, Cancer Facts: Fluoridated Water, National Institutes of Health.
3 Dr. Richard Carmona, U.S. Surgeon General, Surgeon General’s Statement on Community
Water Fluoridation, Department of Health and Human Services, 2004.
4 Centers for Disease Control and Prevention, “Populations Receiving Optimally Fluoridated
Public Drinking Water — United States, 2000,” Morbidity and Mortality Weekly Report,
vol. 51, no. 7, Feb. 21, 2002, pp. 144-147.
5 Centers for Disease Control and Prevention, “Achievements in Pubic Health, 1900-1999:
Fluoridation of Drinking Water to Prevent Dental Caries,” Morbidity and Mortality Weekly
Report, vol. 48, no. 41, Oct. 22, 1999, pp. 933-940. Available online at [http://www.cdc.gov/
mmwr/preview/mmwrhtml/mm4841a1.htm]; visited Feb. 3, 2006.
6 Centers for Disease Control and Prevention, “Ten Great Public Health Achievements —
United States, 1900-1999,” Morbidity and Mortality Weekly Report, vol. 48, no. 12, Apr.
2, 1999, pp. 241-243. See [http://www.cdc.gov/mmwr/preview/mmwrhtml/00056796.htm].
7 Centers for Disease Control and Prevention, Populations Receiving Optimally Fluoridated
(continued...)

---

CRS-3
One of the CDC’s national health goals for 2010 is to increase the proportion
of the U.S. population served by community water systems with “optimally”
fluoridated drinking water to 75%.8 The optimal fluoridation level recommended by
the U.S. Public Health Service for decay prevention is in the range of 0.7 to 1.2
milligrams per liter (mg/L).
The World Health Organization (WHO) has identified dental caries (cavities)
as a worldwide epidemic and recommends adding fluoride to drinking water where
naturally occurring levels of fluoride are below optimal levels.9 The WHO states that
the goal of community-based public health programs “should be to implement the
most appropriate means of maintaining a constant low level of fluoride in as many
mouths as possible.”10 According to the WHO,
[w]ater fluoridation in low fluoride-containing water supplies helps to maintain
optimal dental tissue development and dental enamel resistance against caries
attack during the entire life span.... People of all ages, including the elderly,
benefit from community water fluoridation. For example, the prevalence of
caries on root surfaces of teeth is inversely related to fluoride levels in the
drinking water: in other words, within the non-toxic range for fluoride, the higher
the level of fluoride in water, the lower the level of dental decay. This finding
is important because with increasing tooth retention and an aging population, the
prevalence of dental root caries would be expected to be higher in the absence
of fluoridation.11
The recommended beneficial amount of fluoride can be obtained from a variety
of sources other than water (e.g., fluoride toothpastes, rinses, and supplements).
However, health officials generally have recommended fluoridation of community
water supplies, citing socioeconomic reasons that may vary among countries and
communities. The WHO explains this preference as follows:
The consensus among dental experts is that fluoridation is the single most
important intervention to reduce dental caries, not least because water is an
essential part of the diet for everyone in the community, regardless of their
motivation to maintain oral hygiene or their willingness to attend or pay for
dental treatment. In some developed countries, the health and economic benefits
7 (...continued)
Public Drinking Water, pp. 144.
8 U.S. Department of Health and Human Services, Healthy People 2010 — Understanding
and Improving Health, 2nd ed., Washington, DC, U.S. Government Printing Office,
November 2000, pp. 21-28.
9 World Health Organization, Water Sanitation and Health, World Water Day 2001: Oral
Health: Dental Caries, a Worldwide Epidemic, Health and Sanitation Unit and Oral Health
Program. Available online at [http://www.who.int/water_sanitation_health/oralhealth/
en/index1.html]; visited Feb. 3, 2006.
10 World Health Organization, Risks to Oral Health and Intervention: Fluoride. See
[http://www.who.int/oral_health/action/risks/en/index1.html]; visited Feb. 3, 2006.
11 Ibid.

---

CRS-4
of fluoridation may be small, but particularly important in deprived areas, where
water fluoridation may be a key factor in reducing inequalities in dental health.12
Despite such recommendations, fluoridation is far from universally practiced.
Worldwide, an estimated 350 million people receive artificially fluoridated water,
and another 50 million drink water that is naturally fluoridated at or near the optimal
level.13 Australia, Canada, Chile, Columbia, Israel, Malaysia, and Singapore are
among the countries where water is fluoridated. Of the Western European countries,
Ireland, Spain, and the United Kingdom fluoridate drinking water. Most other
Western European countries have ceased, or never practiced, water fluoridation for
various reasons, including the availability of other sources of fluoride (especially
toothpaste), the availability of free school-based dental care programs in some
countries, broader public skepticism about the safety and efficacy of fluoridation, and
greater political opposition. In several Latin American countries, where centralized
water supplies are often lacking, fluoridated salt is the chosen method of providing
dental protection across disparate communities. Fluoridated salt also is available in
some European countries, including Austria, France, Germany, Hungary, and
Switzerland.14
Questions About the Safety and Benefits of Fluoridation
Water fluoridation has generated less opposition in the United States than in
Europe. However, notwithstanding recommendations from many governmental and
professional health organizations, this practice continues to generate controversy in
some communities. Research gaps concerning the effects of long-term exposure to
increased levels of fluoride fuel this debate, and decades into this practice, the safety
and efficacy of water fluoridation continues to be questioned, debated, and studied.
Dental Fluorosis. Some oppose water fluoridation because of a concern that
even recommended “optimal” levels of fluoridation may cause dental fluorosis in
children. Dental fluorosis is caused by excessive fluoride intake while teeth are
developing, and it is during this period before teeth erupt that dental tissues are very
sensitive to fluoride (typically during a child’s first eight years).15 Mild dental
fluorosis is characterized by opaque white or stained patches in the dental enamel.
More severe fluorosis is characterized by pitting of tooth enamel. Since the 1960s,
the U.S. Public Health Service has recommended an “optimal” fluoride concentration
12 World Health Organization, Naturally Occurring Hazards. Available online at
[http://www.who.int/water_sanitation_health/naturalhazards.html#fluoride]; visited Feb. 3,
2006.
13 British Fluoridation Society and the UK Public Health Association, One in a Million: The
Facts about Water Fluoridation, 2nd ed., 2004, p. 71.
14 Marthaler, T. M. Salt Fluoridation in Europe, Comparisons with Latin America,
Department of Preventive Dentistry, Periodontology and Cariology, University of Zurich,
available at [http://www.sph.emory.edu/PAMM/SALT2000/marthaler.pdf]; visited Feb. 7,
2006.
15 Institute of Medicine. Dietary reference Intakes for Calcium, Phosphorus, Magnesium,
Vitamin D, and Fluoride, Standing Committee on the Scientific Evaluation of Dietary
Reference Intakes, Food and Nutrition Board, National Academy Press, 1997, p. 298.

---

CRS-5
in water of 0.7 to 1.2 mg/L. This level was designed to “maximize prevention of
caries while limiting the prevalence of dental fluorosis to about 10% of the
population, virtually all of it mild to very mild.”16
Because of the increased use of fluoridated dental products and the tendency for
young children to swallow these products, concern over dental fluorosis and other
potential effects of fluoride exposure has increased. Questions have arisen as to
whether current fluoridation practices and levels offer the most appropriate ways to
provide the beneficial effects of fluoride while avoiding adverse effects that can
result from ingesting too much fluoride. As noted by the National Research Council
(NRC) of the National Academy of Sciences,
In addition to fluoride in drinking water, people also can ingest fluoride in
toothpaste, mouth rinse, and dietary fluoride supplements or in beverages and
foods prepared with fluoridated water. As a result, many Americans might ingest
more “incidental” fluoride than was anticipated by the PHS [Public Health
Service] and by EPA in recommending standards for drinking water.17
A 2002 study reported that estimates of fluorosis prevalence among
schoolchildren in the 1980s were 18% or 26%, depending on the analytical index
used. The authors further estimated that based on these findings and further studies,
approximately 2% of U.S. schoolchildren may experience “perceived esthetic
problems” that could be attributable to currently recommended levels of fluoride in
drinking water combined with fluoride toothpaste consumption.18 The authors
reported that data were not available for fluoridated toothpaste and diluted infant
formula consumption and that, consequently, the risk of fluorosis attributable to
fluoridation of public water supplies may be overestimated if fluoride consumption
was higher in fluoridated areas.19 The researchers concluded that in determining the
optimal fluoridation policy, the prevalence of dental fluorosis
should be weighed against fluoridation’s lifetime benefits and the feasibility and
associated costs of alternative solutions such as educating parents of preschoolers
about appropriate toothpaste use and lowering the current fluoride content of
children’s toothpaste. Given that fluorosis results from fluoride exposure during
a narrow age range and that the benefits accrue over the entire life span,
educating parents as to the appropriate use of fluoride toothpaste or reducing the
16 National Research Council, Health Effects of Ingested Fluoride, Subcommittee on Health
Effects of Ingested Fluoride, Committee on Toxicology, Board on Environmental Studies
and Toxicology, Commission on Life Sciences, National Academy Press, 1993, p. 5.
Note: Researchers have found dental fluorosis to have a clear dose-response relationship —
increasing in severity and prevalence at higher concentrations — with effects generally
ranging from mild or very mild at roughly 0.7 to 1.0 mg/L, to pronounced discoloration and
pitting of teeth occurring at 5 to 7 mg/L and higher.
17 Ibid.
18 Griffin, Susan O., Eugenio D. Beltran, Stuart A. Lockwood, and Laurie K. Barker,
Esthetically Objectionable Fluorosis Attributable to Water Fluoridation, Community Dental
Oral Epidemiology, 2002, vol. 30, pp. 199-209. The prevalence of “perceived esthetic
problems” was assessed by evaluating fluorosis in the teeth at the front of the mouth.
19 Ibid. pp. 199, 208-209.

---

CRS-6
fluoride content of children’s toothpaste as some have suggested may be more
efficient than altering current fluoridation policy.20
The NRC agreed with this conclusion in principal; however, it determined that
this approach may not be feasible in practice:
The most effective approach to stabilizing the prevalence and severity of dental
fluorosis, without jeopardizing the benefits to oral health, is likely to come from
more judicious control of fluoride in foods, processed beverages, and dental
products, rather than a reduction in the recommended concentrations of fluoride
in drinking water. But applying such a policy would be formidable; reduction of
fluoride concentrations in drinking water would be easier to administer, monitor,
and evaluate.21
Although dental fluorosis is considered to be a cosmetic effect, not a health effect,
it may be objectionable to many and, therefore, does factor in the fluoridation
debate.22
Health Effects. Researchers continue to study the potential adverse health
effects associated with exposure to low levels of fluoride. Many studies have
examined the potential toxic effects of long-term ingestion of fluoride in drinking
water. These studies generally show that fluoride ingestion primarily produces effects
on skeletal tissues (skeletal fluorosis) and that these effects are more severe as
exposure to fluoride increases above a threshold. Very mild skeletal fluorosis is
characterized by slight increases in bone mass. The most severe form of this
condition, “crippling skeletal fluorosis,” involves bone deformities, calcification of
ligaments, and immobility. Epidemiological data suggest that crippling skeletal
fluorosis might occur in humans who drink water containing more than 10 mg/L of
fluoride for 10 to 20 years.23 This condition is extremely rare in the United States
and is not considered a public health concern.
Bone Fracture Incidence. A related question that has been the subject of
scientific debate and research concerns whether water fluoridation increases the risk
of bone fracture in older women. A number of ecological studies conducted in the
1980s and 1990s compared rates of fracture, specific for age and gender, between
20 Ibid. p. 209.
21 National Research Council, Health Effects of Ingested Fluoride, pp. 47-48.
22 In setting a standard for fluoride in drinking water, the U.S. Environmental Protection
Agency (EPA) considered dental fluorosis to be a cosmetic effect, not an adverse health
effect, and set the standard at a level that was not intended to protect against mild dental
fluorosis. This issue is discussed below in the section on the federal regulation of fluoride
in drinking water.
23 National Research Council, Health Effects of Ingested Fluoride, p. 59. The severity of
fluorosis varies among individuals and is complicated by factors such as malnutrition,
calcium deficiency, and impaired kidney function (the kidneys clear much of the fluoride
that is ingested). India has a high incidence of fluorosis because water supplies in large
areas of the country contain high levels of naturally occurring fluoride. Fluorosis is also
widely prevalent in China, the Middle East, North Africa, and other parts of Africa.

---

CRS-7
fluoridated and nonfluoridated communities. Several of these studies found that
exposure to fluoridated water increased the risk of fracture, a few studies showed that
water fluoridation reduced the risk of fracture, and several studies found no effect.24
However, a weakness of these studies is that they were based on community-level
data and lacked data on individuals.
To improve understanding of this issue, a 2000 study published in the British
Medical Journal looked at fluoride exposure and fractures in individual women. The
results of this study suggested that water fluoridation may reduce the risk of fractures
of the hip and vertebrae in older white women (the subjects of the study).25 The
authors noted the potential public health importance of this finding, stating that “[i]f
fluoridation does reduce the incidence of hip fracture, it may be one of the most cost
effective methods of reducing the incidence of fractures related to osteoporosis.”26
Cancer: Human Epidemiology. A possible link asserted in the 1970s
between water fluoridation and increased cancer mortality raised health concerns and
heightened controversy over the practice of fluoridation. Some researchers had
reported that cancer mortality was higher in areas with fluoridated drinking water
than in nonfluoridated areas.27 These findings were refuted subsequently by other
investigators who identified problems with the study’s research methodology.28
However, because of the importance of this question, researchers have continued to
examine the possibility of an association between fluoridated water and cancer in
humans.
Independent expert panels performed extensive reviews of the available
scientific studies in 1982 and 1985. The panels agreed that the studies provided “no
credible evidence for an association between fluoride in drinking water and risk of
cancer.”29 According to the National Research Council, all but one of these studies
were ecological studies; that is, they were either geographic correlation or time-line
studies that looked at exposures at the community level rather than individual
exposures.30 Consequently, the interpretation of the data was complicated by an
inability to measure individual fluoride exposures over long periods of time, or to
24 National Research Council, Health Effects of Ingested Fluoride, pp. 60-61.
25 Phipps, Kathy R., Eric S. Orwoll, Jill D. Mason, Jane A. Cauley, “Community Water
Fluoridation, Bone Mineral Density, and Fractures: Prospective Study of Effects in Older
Women,” British Medical Journal, Oct. 7, 2000, vol. 321, pp. 860-864.
26 Ibid. p. 863.
27 Yiamouyannis, J. and D. Burk, “Fluoridation and Cancer: Age Dependence of Cancer
Mortality Related to Artificial Fluoridation,” Fluoride, no. 10, 1977, pp. 102-123.
28 National Research Council, Health Effects of Ingested Fluoride, p. 16.
29 Ibid. p. 110.
30 Epidemiological studies look for associations between the occurrence of disease and
exposure to known or suspected causes. In ecological studies, the unit of observation is the
population or community; the specific exposures of individuals are not assessed.

---

CRS-8
measure exposure to other known risk factors such as smoking or other cancer-
causing substances.31
In another examination of this issue, scientists at the National Cancer Institute
(NCI) evaluated the relationship between drinking water fluoridation and the number
of cancer deaths in the United States by county. After examining more than 2.2
million cancer death records, NCI researchers concluded that “there was no
indication of increased cancer risk associated with fluoridated drinking water.”32 The
NRC concluded in 1993 that “[t]he large number of epidemiological studies [more
than 50] combined with their lack of positive finding implies that if any link exists,
it must be very weak.”33
Cancer: Animal Studies. In 1990, the National Toxicology Program (NTP)
published the results of studies on the potential carcinogenicity of fluoride in rats and
mice.34 The studies found no evidence of carcinogenic activity in female rats or mice
at very high concentrations (100-175 mg/L) but found “equivocal evidence” of
carcinogenicity in male rats. Osteosarcomas (bone cancers) were observed in 1 of
50 male rats receiving 100 mg/L sodium fluoride and 3 of 50 rats receiving 175
mg/L.35 From this study, NTP researchers concluded that levels of sodium fluoride
below 175 mg/L in drinking water over a two-year period would not be expected to
cause any bone cancers in rats or mice. Although extrapolation of data from animals
to humans is controversial in the scientific community, it is generally thought that
optimally fluoridated drinking water (roughly 1 mg/L) would not be expected to
cause cancer in humans. The result of the NTP study (i.e., equivocal evidence of
carcinogenicity) was not substantiated in a subsequent study of rats using higher
fluoride doses.
In response to the concerns raised by the NTP research, EPA requested that the
National Research Council (NRC) review the available toxicological and exposure
data on fluoride and determine whether the current drinking water standard of 4 mg/L
was sufficient to protect public health. In 1993, the National Research Council
(NRC) completed an extensive literature review concerning the association between
fluoridated drinking water and increased cancer risk. Although the NRC concluded
31 U.S. Department of Health and Human Services, Public Health Service, Ad-hoc
Subcommittee on Fluoride, Committee to Coordinate Environmental Health and Related
Programs, Review of Fluoride: Benefits and Risks, Executive Summary, Febrary 1991, p.
9.
32 National Cancer Institute, Cancer Facts: Fluoridated Water, 2000. Details discussed in
National Research Council, Health Effects of Ingested Fluoride, Carcinogenicity of
Fluoride. pp. 109-112.
33 Ibid. p. 121.
34 National Toxicology Program, Toxicology and Carcinogenesis Studies of Sodium Fluoride
in 344/N Rats and B6C3F1 Mice, Department of Health and Human Services, National
Institutes of Health, Technical Report 393, NIH Publ. No. 91-2848, 1990, p. 447.
35 By NTP definition, equivocal evidence of carcinogenic activity is a category for uncertain
findings by studies that are interpreted as showing a marginal increase in cancers that may
be related to the administration of a chemical.

---

CRS-9
that the data did not demonstrate an association between fluoridated drinking water
and cancer, it did suggest that more research should be undertaken.36
In 2002, EPA noted that new studies regarding the effects of fluoride on bone
had been published since the fluoride standard was promulgated and that a new
analysis of the data was warranted. EPA again requested the NRC to review the
toxicological and epidemiological data on fluoride, to update the fluoride risk
assessment, and to evaluate the scientific basis and adequacy of EPA’s drinking
water standards for fluoride.37 The NRC study is pending. (See the section below on
the regulation of fluoride.)
Efficacy. The benefits of water fluoridation to oral health also has received
scrutiny. An overall reduction in caries has been observed in both fluoridated and
nonfluoridated communities in the United States, and some more recent studies have
suggested that water fluoridation has become less important and effective in
preventing caries when compared with the findings of earlier studies. Some of this
research has attributed the smaller differences in caries prevalence between
fluoridated and nonfluoridated communities to the widespread use of fluoride
toothpaste and other preventive dental care, and to better nutrition.38
Several studies have suggested that the traditional measure of the benefits of
water fluoridation may understate its total effectiveness. The authors of a 2001 study
determined that the benefit of caries reduction from fluoridation is diffused to
adjacent nonfluoridated communities through the export of bottled beverages and
processed foods to those communities.39 When this effect was accounted for, the
authors found a beneficial effect from water fluoridation that was closer to the
findings of studies conducted in the 1970s and earlier.40 The results of a 1979-1980
national survey found a 33% difference in the prevalence of dental caries among
children in fluoridated and nonfluoridated regions in the United States, whereas a
1986-1987 national survey identified an overall 18% difference in caries prevalence.
The National Institutes of Health analyzed the 1986-1987 results and reported that
when the effect of topical fluoride was controlled, the difference between fluoridated
and nonfluoridated areas increased to 25%. The authors concluded that the results
36 National Research Council, Health Effects of Ingested Fluoride, pp. 121-123.
37 U.S. Environmental Protection Agency, “National Primary Drinking Water Regulations:
EPA’s Review of Existing Drinking Water Standards and Request for Public Comment,” 67
Federal Register 19069, Apr. 17, 2002.
38 See, for example, Seppa, L., et al. “Caries Occurrence in a Fluoridated and a
Nonfluoridated Town in Finland: A Retrospective Study Using Longitudinal Data from
Public Dental Records,” Caries Research, 2002, vol. 36, no. 5, pp. 308-314.
39 Griffin, Susan O., Barbara F. Gooch, Stuart A. Lockwood, and Scott Tomar. “Quantifying
the Diffused Benefit from Water Fluoridation in the United States,” Community Dentistry
and Oral Epidemiology, 2001, vol. 29, pp. 120-129.
40 Ibid. p. 128.

---

CRS-10
suggested that water fluoridation continued to play a dominant role in the decline in
caries.41
In 2000, British researchers published the results of their systematic review of
214 studies on the safety and efficacy of water fluoridation. The researchers found
that water fluoridation was associated with an increased proportion of children
without caries and a reduction in the number of teeth with caries, but the overall
reductions were smaller than had been reported in earlier studies.42 The review also
concluded that at a fluoride level of 1 mg/L, an estimated 12.5% of exposed
individuals would have fluorosis that could be considered aesthetically concerning.43
In reviewing the 214 studies, the authors found no other adverse effects associated
with the fluoridation of drinking water. However, they noted that, overall, the studies
were of low to moderate quality and recommended better research.44
Other Considerations. Aside from questions of safety and efficacy, social
and political concerns may influence decisions about water fluoridation. A central
issue for some who oppose fluoridation of the public water supply is lack of choice.
Consumers who prefer not to drink fluoridated water are unable to exercise that
choice without treating their tap water or buying bottled water. Some view a state
or community fluoridation requirement as intrusive and object to receiving water that
is not free of additives, other than those needed to make water safe. (In contrast,
disinfectants, such as chlorine, generally have been accepted as necessary to protect
public health by eliminating pathogens). In this view, decisions regarding dental
health-care practices should be made by individuals and families and not imposed by
the government. To the extent that research gaps exist regarding potential adverse
effects of increased exposures to fluoride because of its presence in multiple sources
(e.g., water, beverages, toothpaste and rinses), the conflict between individual choice
and public policy is likely to continue.
Regulation of Fluoride in Drinking Water
This section discusses the regulation of fluoride in drinking water to protect
against adverse health effects associated with exposure to higher, typically naturally
occurring levels of fluoride (compared with the recommended levels used in artificial
fluoridation to protect dental health). It reviews the current federal standards for
fluoride in drinking water, EPA’s steps to review the standards, and related efforts
to update the assessment of health risks associated with fluoride ingestion.
Fluoride poses challenges to regulators because it is intentionally added to water
supplies for its beneficial effects at low levels, whreas at higher concentrations, it has
41 Brunelle, J.A. and J.P. Carlos, “Recent Trends in Dental Caries in U.S. Children and the
Effect of Water Fluoridation,” National Institute of Dental Research National Institutes of
Health, Journal of Dental Research, February 1990, vol. 69, pp. 723-727.
42 McDonagh, Marian S., Penny F. Whiting, et al., “Systematic Review of Water
Fluoridation,” British Medical Journal, Oct. 7, 2000, vol. 321, pp. 855-864.
43 Ibid. p. 855.
44 Ibid. p. 859.

---

CRS-11
toxic effects and is regulated as a drinking water contaminant. Moreover, the range
between the amounts that are considered beneficial and excessive is narrower for
fluoride than for many trace minerals.45
Under the authority of the Safe Drinking Water Act (SDWA), the
Environmental Protection Agency (EPA) regulates the amount of fluoride that may
be present in public water supplies to protect against fluoride’s adverse health effects.
In 1986, EPA issued the current national primary drinking water regulation for
fluoride. This regulation includes an enforceable maximum contaminant level for
fluoride of 4 mg/L, specifically to protect against effects on the bone (skeletal
fluorosis).46 This standard was controversial, as it replaced an interim standard of
1.4 to 2.4 mg/L that was established to protect against moderate dental fluorosis.47
The SDWA requires EPA to conduct periodic reviews of existing drinking water
regulations, and EPA has initiated a review of the fluoride standard to determine
whether it needs revision.48
When setting the fluoride standard, EPA acknowledged that the standard does
not protect infants and young children against moderate dental fluorosis, which EPA
considers a cosmetic effect, rather than an adverse health effect. The Agency set a
secondary standard for fluoride at 2 mg/L that is intended to protect children against
dental fluorosis and adverse health effects.49 Because of concerns regarding dental
fluorosis, EPA does not recommend that infants consume water containing 4 mg/L
fluoride and requires that all families who receive water from a public water system
with more than 2 mg/L receive a public notification recommending that alternate
sources of water be used for infants and children (40 CFR 143.5).
45 Many trace minerals share the property of having a health benefit at low levels but toxicity
at higher levels (e.g., copper, chromium, manganese, selenium, and zinc). Although certain
amounts of fluoride help make tooth enamel resistant to caries, fluoride has not been
classified as an essential nutrient. In 1997, the National Academy of Science established
Dietary Reference Intakes (DRI) for fluoride as a nutrient. The DRI included age- and
gender-specific tolerable upper intake levels (UL) to indicate the highest average daily
intake level likely to pose no risk of adverse effect to most individuals. The NAS also
established Adequate Intake (AI) values for fluoride. AI values are set when the data do
not permit determination of a Recommended Dietary Allowance (RDA).
46 51 Federal Register 11396, Apr. 2, 1986.
47 51 Federal Register 11410, Apr. 2, 1986.
48 SDWA §1412(b)(9) requires the EPA Administrator, not less often than every six years,
to review and revise, as appropriate, each national primary drinking water regulation. Since
1996, the law has specified that any revision must maintain or provide for greater protection
of human health.
49 Under the Safe Drinking Water Act, EPA sets national primary drinking water regulations
that include enforceable, health-based standards (maximum contaminant levels) that limit
the amount of a regulated substance that may be present in water provided by public water
systems. EPA also sets national secondary standards that establish nonmandatory water
quality standards for substances. Secondary standards are established as guidelines to help
public water systems manage drinking water for aesthetic (e.g., taste and odor), cosmetic
(e.g., tooth discoloration), and technical (e.g., corrosivity) effects.

---

CRS-12
Following increased concern regarding the potential carcinogenicity of fluoride
related to the results of the 1990 NTP animal study, EPA requested the National
Research Council (NRC) to review the available toxicological and exposure data on
fluoride and to assess the sufficiency of the current drinking water standard. The
NRC concluded that the national primary drinking water standard for fluoride (4
mg/L) was “appropriate as an interim standard” to protect public health. However,
the NRC noted that because EPA had promulgated the drinking water regulation for
fluoride in 1986, the use of fluoride in dental products had increased and, as a result,
many Americans might ingest more “incidental” fluoride than was anticipated by the
Public Health Service and by EPA when recommending standards for drinking
water.50 Moreover, the NRC found inconsistencies in the fluoride toxicity data base
and gaps in knowledge, and it recommended further research in the areas of fluoride
intake, dental fluorosis, bone strength, and carcinogenicity. The NRC further
recommended that EPA’s fluoride standard should be reviewed and, if necessary,
revised when results of new research become available.51
Toward that end, in 1998, EPA commissioned an evaluation of the exposure
data for fluoride, including data on amounts in water, foods, and dental products. In
2002, EPA published the results of its review of existing drinking water standards,
including the fluoride standard.52 The Agency noted that new studies on fluoride’s
effects on bone had been published since EPA issued the fluoride standard in 1986.
EPA had conducted a literature search to identify reports of the clinical,
toxicological, and epidemiological data on fluoride and the skeletal system. The
results of that search indicated that a review of the new data was justified as part of
the regulatory review process. Consequently, EPA requested the NRC to conduct a
review of the data and to update the fluoride health risk assessment and to review
EPA’s relative source contribution assumptions.53 The NRC agreed to evaluate the
scientific basis for EPA’s primary and secondary fluoride standards and to advise
EPA on the adequacy of its secondary standard to protect to protect children and
others from adverse effects.
The NRC is nearing publication of its assessment of the toxicologic risk of
fluoride in drinking water. The results of the NRC assessment are expected to help
EPA determine whether the primary and secondary fluoride standards need to be
revised. Even if the NRC confirms EPA’s earlier assessment of fluoride toxicity and
health effects, the Agency still might revise the standard. One reason for potential
revision is that when EPA developed the current standards, the Agency considered
drinking water to be the only source of exposure for fluoride. Since then, sources of
fluoride exposure have increased, and EPA would consider fluoride intake from
50 Ibid.
51 Ibid. p. 11.
52 U.S. Environmental Protection Agency, “National Primary Drinking Water Regulations:
Announcement of the Results of EPA’s Review of Existing Drinking Water Standards and
Request for Public Comment,” 67 Federal Register 19030, Apr. 17, 2002.
53 EPA based the current standard on the assumption that drinking water was the only source
of fluoride exposure; thus, water’s relative source contribution was considered to be 100%.
In revising the standard, EPA would consider other sources of exposure also.

---

CRS-13
sources other than drinking water. This consideration alone may lead to a lowering
of the health-based primary standard and the esthetics-based secondary standard for
fluoride. EPA’s position on this issue is not yet known, and it may take some time
for EPA to evaluate and respond to the NRC study.
Conclusion
The use of dental products containing fluoride (such as toothpaste and rinses)
has increased significantly in recent years. As a result, many people now may be
taking in more fluoride than was anticipated when the Public Health Service
recommended optimal levels for water fluoridation and when EPA issued its
regulation establishing limits for fluoride in drinking water. Consequently, questions
have emerged as to whether current water fluoridation practices offer the most
appropriate ways to provide the expected beneficial effects of fluoride while avoiding
potential adverse effects that may result from exposure to too much fluoride.
Moreover, research gaps and scientific uncertainty regarding the health effects of
long-term exposure to higher levels of fluoride add controversy to decisions
regarding drinking water fluoridation.
Although the purpose of the National Research Council study is to advise EPA
on the adequacy of its primary and secondary drinking water standards for fluoride,
the assessment of the available science is likely to also be valuable to those who are
interested in evaluating the currently recommended levels for water fluoridation and
to communities that are assessing whether or not to fluoridate their public water
supplies.
Opposition to water fluoridation often has been driven by concerns about the
health risks of exposure to fluoride in drinking water; however, social and political
concerns also influence decisions about water fluoridation. A central issue for some
fluoridation opponents is lack of choice, and they oppose the addition of any
chemicals to the water supply other than those needed to make water safe. In contrast,
many public health professionals and government officials believe that water
fluoridation offers the most equitable and cost-effective way to protect dental health
across socially and economically diverse communities. The conflict between
individual liberty and social policy is one that is unlikely to be fully resolved by more
research. Additional scientific evidence can help inform the decision to fluoridate a
community’s water, but such choices often are not made purely on the basis of
science.
Congress has expressed interest in water fluoridation issues in the past,
particularly as questions have arisen regarding the benefits and risks of this practice.
However, because fluoridation decisions are made at the state and local level, and
perhaps also because of the documented benefits of fluoridation, Congress has not
been at the forefront of the water fluoridation debate. In contrast, Congress does
have a key role pursuant to EPA’s regulation of fluoride in public drinking water
supplies under the Safe Drinking Water Act. The findings of the NRC study of the
toxicological risk of fluoride and the appropriateness of the EPA’s drinking water
standards for fluoride may generate new congressional oversight and legislative
attention

---