Fluoride in your drinking
water: History, Science, and
Policy
ENV H 472 A - ENVIRONMENTAL RISK AND SOCIETY
Class 12
Steven G. Gilbert, PhD, DABT
www.toxipedia.org
SOT – Fluoride - History – 02/11/10
Issues




Should public water be fluoridated?
Benefits – reduced dental carries
Risks – dental fluorosis – bone disease
Dose - Response
Mild fluorosis
Severe fluorosis
SOT – Fluoride - History – 02/11/10
Fundamental Issue
Science meets Policy
 Ethical, legal, social, political,
scientific considerations
 Engage Public?
 Role of government agencies?
 Local – National – International?
SOT – Fluoride - History – 02/11/10
History of Fluoride
 1899 - Sodium Fluoride -- Herbert H
Baldwin reported symptoms of acute
toxicity (e.g. gastrointestinal upset) doses
as low as 0.1-0.3 mg/kg.
 1909 – “Colorado stain” (fluorosis) Frederick McKay, observed children in the
Pikes Peak region had of stain or mottling
on their teeth but fewer cavities
 1931 – G.V. Black (father of modern
dentistry) and others concluded fluoride
ion in the water was the cause
SOT – Fluoride - History – 02/11/10
History of Fluoride
 1939 – Gerald J. Cox first publication
recommending the addition of fluoride to
drinking water to improve oral health at 1
ppm level
 1940’s - several paired city studies conclude
fluoride in drinking water is beneficial
 1945, January 25 - Grand Rapids, Michigan first community in the world to add fluoride
to its drinking water to benefit dental health
 1940’s Fluorine used in bomb making
(University of Rochester – Harold Hodge)
SOT – Fluoride - History – 02/11/10
Stannous Fluoride
 1951, Joseph C. Muhler and Harry
G. Day of Indiana University
reported that stannous fluoride as
a tooth decay preventive and the
university first sold the technology
to Procter & Gamble to use in Crest
toothpaste.
SOT – Fluoride - History – 02/11/10
CDC’s Recommendation
“Nature's Way to Prevent Tooth Decay”
“...fluoride prevents dental caries
predominately after eruption of
the tooth into the mouth, and its
actions primarily are topical for
both adults and children…”
CDC (1999). Achievements in Public Health, 1900-1999: Fluoridation of
Drinking Water to Prevent Dental Caries. MMWR, 48(41); 933-940, October 22.
SOT – Fluoride - History – 02/11/10
How Fluoride Works
Teeth are generally composed of
hydroxyapatite and carbonated
hydroxyapatite; when fluoride is present,
fluorapatite is created. Fluorosis cannot
occur once the tooth has erupted into the
oral cavity. Topical fluoride encourages
fluorapatite which is beneficial because it
is more resistant to dissolution by acids
(demineralization).
SOT – Fluoride - History – 02/11/10
Dental Fluorosis with “Optimal” Fluoride
• 67% of US people exposed to fluoridated
water – most large cities
• 1997 - 29.9% of US children living in
fluoridated communities have dental
fluorosis on (Heller et al, 1997).
• 2005 - CDC dental fluorosis effects 1 in 3
American kids - up 9% since 1986-87.
• 2006 - ADA & CDC offers interim guidance
on infant formula and fluoride
SOT – Fluoride - History – 02/11/10
Ethical Issues
• Individual vs Public Health?
• Fluoridation of public water is
"compulsory mass medication"
• Individual Consent?
• Legal – human rights – choice?
• Improves dental care for low-income
people.
• Not mass medication because fluoride
is natural.
• Similar to fortifying foods with vitamins
SOT – Fluoride - History – 02/11/10
MCLG-MCL
•
MCLG – maximum contaminant level goal
- level of a contaminant in drinking water
below which there is no know or expected risk
to health
- non-enforceable public health goal
•
MCL – maximum contaminant level
- highest level of a contaminant allowed in
drinking water
- enforceable standard
- set as close as feasible to the MCLG;
technology and costs are considered
SOT – Fluoride - History – 02/11/10
SMCL
•
SMCL – secondary maximum contaminant
level
- non-enforceable guideline for managing
drinking water for aesthetic, cosmetic (e.g.,
tooth discoloration), or technical effects
SOT – Fluoride - History – 02/11/10
History
• 1986
– MCLG and MCL set at 4 mg/L to protect against
“crippling” skeletal fluorosis
– SMCL set at 2 mg/L to reduce occurrence and
severity of “objectionable” enamel fluorosis.
• 1993
– MCL reviewed by NRC in 1993
– 4 mg/L is appropriate as an interim MCL
– More research needed on fluoride intake, enamel
fluorosis, bone strength and fractures, and
carcinogenicity.
SOT – Fluoride - History – 02/11/10
National Academy of Sciences - Tasks
• Review toxicologic, epidemiologic, and
clinical data on fluoride, particularly data
conducted since 1993 NRC report
• Review exposure data on orally ingested
fluoride from drinking water and other
sources (e.g., food, toothpaste)
• Evaluate the scientific basis of the MCLG and
SMCL and their adequacy to protect children
and others from adverse health effects.
• Consider relative contribution of various
fluoride sources to total exposure.
• Identify data gaps and recommend research
relevant to setting the MCLG and SMCL.
SOT – Fluoride - History – 02/11/10
Exposure
Drinking Water Contribution to Total Exposure
• Drinking Water – Natural Sources
- 2.0-3.9 mg/L (1.4 million people exposed)
57% - 90% for average individual
86% - 96% for high-water intake individual
- ≥ 4mg/L (200,000 people exposed)
72% - 94% for average individual
92% - 98% for high-water intake individual
• Drinking Water – Artificial Sources
- PHS recommends 0.7-1.2 mg/L (162 million people exposed)
41% - 83% for average individual
75% - 91% for high-water intake individual
SOT – Fluoride - History – 02/11/10
Enamel fluorosis
• Enamel fluorosis is a dose-related mottling
of enamel ranging from mild discoloration to
severe dark stains and pitting in children (0
to 8 years). Permanent condition.
• Historically, condition considered cosmetic
because it is not associated with tooth loss,
loss of tooth function, or psychological,
behavioral, or social problems.
• Cause: receiving too much fluoride during
tooth development.
• Committee separated severe from moderate
fluorosis.
– Severe: mottling with enamel pitting and/or loss
– Moderate: mottling but no enamel pitting or loss
SOT – Fluoride - History – 02/11/10
Severe Enamel Fluorosis
SOT – Fluoride - History – 02/11/10
Severe Enamel Fluorosis
Severe Enamel Fluorosis in Children in the United States
Source: Selwitz et al. (1995, 1998)
SOT – Fluoride - History – 02/11/10
NAS Recommendations
• New risk assessment should be performed on
fluoride. The assessment should include new data
on health risks, better estimate of total exposure to
fluoride, and updated approaches to risk
assessment. Key end points for the risk
assessment are severe enamel fluorosis, bone
fracture, and stage II skeletal fluorosis.
• Committee’s conclusions about the adverse effects
at the MCLG and SMCL do not address the lower
concentrations of exposure that occur with water
fluoridation.
SOT – Fluoride - History – 02/11/10
ADVERSE EFFECTS OF 4ppm FLUORIDE
• Enamel damage with severe fluorosis
PROVEN
• Increased fractures in susceptible groups
PROBABLE
• Skeletal fluorosis (stage II)
POSSIBLE
SOT – Fluoride - History – 02/11/10
APPROPRIATE RESPONSE??
• Precautionary principle (Wingspread, 1998)
– 1. Take anticipatory action to prevent harm
– 2. Burden of proof on proponents, not public
– 3. Must examine all alternatives (do nothing)
– 4. Process transparent & stakeholders involved
• Evidence based risk assessment (Guzelian,
2005)
–
–
–
1. Research-based evidence vs expert opinion
2. Strength of evidence vs weight of evidence
3. Hazard, probability and causality. Hill criteria
SOT – Fluoride - History – 02/11/10
WHAT’S NEXT??
• A comprehensive analysis of all the
effects of fluoride (adverse, beneficial,
incidence, severity, reversibility etc.)
• Move from “reasonable assurance of
no harm to a risk/benefit analysis
(MOA and dose response).
SOT – Fluoride - History – 02/11/10
Effective versus Toxic Conc.
Severe Dental
Fluorosis
LOAEL=20mg/day (crippling skeletal fluorosis)
Intake = 2L/day
Safety factor=2.5X
4
MCL=4ppm
ppm in drinking water
2.5-4ppm IQ deficits in Chinese studies
?
2
1
2.5ppm=“threshold” for severe dental fluorosis
SCL=2ppm: 4-15% mod. dental fluorosis
?
1ppm=target level of water fluoridation
0
Prevalence
(%)
SOT – Fluoride
- History – 02/11/10
Effective versus Toxic Dose
0.20
4ppm (1L/d, 20 kg child)
0.15
1ppm child 10kg 1L/d
Dose (mg/kg/day)
4ppm (2L/d, 70kg adult)
Average
dietary intake
0.10
Crippling Skel. Flsis
at 40 yr (NRC 77)
EPA RfD
0.05
“Optimal” theraputic
dose range
Age 0-2 yrs
Fluoride 0.71.1 ppm
1ppm child 20 kg 1L/d
1ppm adult 2L/d
1ppm adult 1L/d
0
STANDARDS
THERAPUTIC/DIETARY RANGE
TOTAL INTAKES
SOT – Fluoride - History – 02/11/10
Fluoridated vs. Unfluoridated
Figure 2: Tooth Decay Trends for 12 Year Olds: Fluoridated Vs. Unfluoridated Countries. Data from World Health Organization. (Graph by Chris Neurath).
SOT – Fluoride - History – 02/11/10
More Findings from NAS
• The MCL should be lowered (EPA directed
to do a new risk assessment).
• Bone fluoride concs from lifetime exposure
at 2 ppm (SMCL) fall within or exceed levels
associated with stage II (mod.) or stage III
(sev.) skeletal fluorosis
• The SCML (2ppm) does not completely
protect against moderate enamel fluorosis.
(Moderate enamel fluorosis might have
psychological or social effects.)
SOT – Fluoride - History – 02/11/10
More Findings from NAS
• The possibility has been raised by the
studies conducted in China that fluoride
can lower intellectual abilities. (2.5-4 ppm)
• Fluoride affects normal endocrine function
or response; fluoride is an endocrine
disruptor in the broad sense of altering
normal endocrine function or response.
SOT – Fluoride - History – 02/11/10
Not for infants
• In November 2006, the American Dental
Association and CDC began
recommending to parents that infants
from 0 through 12 months of age
should have their formula prepared
with water that is fluoride-free, or
contains low levels of fluoride to
reduce the risk of fluorosis
SOT – Fluoride - History – 02/11/10
US vs Europe
• The U.S. Centers for Disease Control listed
water fluoridation as one of the ten great
public health achievements of the 20th
century.
• Most European countries have experienced
substantial declines in tooth decay without
its use, primarily due to the introduction of
fluoride toothpaste in the 1970s.
• Fluoridation may be more justified in the
U.S. because of socioeconomic inequalities
in dental health and dental care??
SOT – Fluoride - History – 02/11/10
More Information
 Web Sites
•
•
•
Toxipedia – Fluoride
http://www.toxipedia.org/display/toxipedia/Fluoride
Wikipedia - http://en.wikipedia.org/wiki/Fluoride
The Controversy - http://en.wikipedia.org/wiki/Water_fluoridation_controversy
•
•
Anti fluoridation groups -- Fluoride Action
Network - http://www.fluoridealert.org/ - www.fluorideACTION.net
Pro fluoridation -- CDC on Water Fluoridation
http://www.cdc.gov/fluoridation/
•
•
American Dental Association Fluoridation Facts
2005 - http://www.ada.org/public/topics/fluoride/facts/fluoridation_facts.pdf
American Dental Association Fluoridation http://www.ada.org/public/topics/fluoride/
SOT – Fluoride - History – 02/11/10