SOT – Fluoride - History – 02/11/10 Fluoride in your drinking water: History, Science, and Policy ENV H 472 A - ENVIRONMENTAL RISK AND SOCIETY Class 12

SOT – Fluoride - History – 02/11/10

Fluoride in your drinking water: History, Science, and

Policy

ENV H 472 A - ENVIRONMENTAL RISK AND SOCIETYClass 12

Steven G. Gilbert, PhD, DABTwww.toxipedia.org


Mild fluorosis

Issues

Severe fluorosis

Should public water be fluoridated? Benefits – reduced dental carries Risks – dental fluorosis – bone disease Dose - Response


Fundamental Issue

Science meets Policy Ethical, legal, social, political,

scientific considerations Engage Public? Role of government agencies? Local – National – International?


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


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)

History of 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.

Stannous Fluoride


CDC’s Recommendation

“...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.

“Nature's Way to Prevent Tooth Decay”


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).


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


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


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


SMCL

• SMCL – secondary maximum contaminant level

- non-enforceable guideline for managing drinking water for aesthetic, cosmetic (e.g., tooth discoloration), or technical effects


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.


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.


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)



• Drinking Water – Artificial Sources

- PHS recommends 0.7-1.2 mg/L (162 million people exposed)




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


Severe Enamel Fluorosis


Severe Enamel Fluorosis

Severe Enamel Fluorosis in Children in the United States

Source: Selwitz et al. (1995, 1998)


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.


ADVERSE EFFECTS OF 4ppm FLUORIDE

• Enamel damage with severe fluorosis

PROVEN

• Increased fractures in susceptible groups

PROBABLE

• Skeletal fluorosis (stage II)

POSSIBLE


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


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).


Effective versus Toxic Conc.

Intake = 2L/day

Safety factor=2.5X

MCL=4ppm

0

1

2

4

?

?

2.5ppm=“threshold” for severe dental fluorosis

1ppm=target level of water fluoridation

LOAEL=20mg/day (crippling skeletal fluorosis)

SCL=2ppm: 4-15% mod. dental fluorosis

Prevalence (%)

Severe Dental Fluorosis

ppm

in d

rinki

ng w

ater

2.5-4ppm IQ deficits in Chinese studies


Effective versus Toxic Dose4ppm (1L/d, 20 kg child)

0

0.05

0.10

0.20

4ppm (2L/d, 70kg adult)

“Optimal” theraputic dose range

EPA RfD

Dos

e (m

g/kg

/day

)

0.15

Average dietary intake

Age 0-2 yrs

Fluoride 0.7-1.1 ppm

1ppm adult 1L/d

1ppm adult 2L/d

1ppm child 20 kg 1L/d

1ppm child 10kg 1L/d

STANDARDS THERAPUTIC/DIETARY RANGE TOTAL INTAKES

Crippling Skel. Flsis at 40 yr (NRC 77)


Figure 2: Tooth Decay Trends for 12 Year Olds: Fluoridated Vs. Unfluoridated Countries. Data from World Health Organization. (Graph by Chris Neurath).

Fluoridated vs. Unfluoridated


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.)


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.


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


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??


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/

Documents

SOT – Fluoride - History – 02/11/10 Fluoride in your drinking water: History, Science, and Policy ENV H 472 A - ENVIRONMENTAL RISK AND SOCIETY Class 12