COMMENTARY -- ADDING FLUORIDE TO DRINKING WATER: A GOOD IDEA?

[Guest guest]

Rachel's Democracy & Health News #918, August 2, 2007

 

*COMMENTARY -- ADDING FLUORIDE TO DRINKING WATER: A GOOD IDEA?*

 

[Rachel's introduction: This carefully-researched article raises important

scientific, medical, and ethical questions about the advisability of

medicating entire communities by fluoridating the local water supply. Even

if fluoridation seemed appropriate at one time, does it still seem

appropriate today? Recently hundreds of professionals have been signing a

statement opposing fluoridation of drinking

water<http://www.precaution.org/lib/professionals_statement.070802.htm>

supplies <http://www.precaution.org/lib/professionals_statement.070802.htm>

..]

 

By Ted Schettler MD, MPH

 

[Dr. Ted Schettler is science director of the Science and Environmental

Health Network <http://www.sehn.org/>. He has co-authored two books on

children's health, In Harm's Way<http://psr.igc.org/ihw-download-report.htm>,

and Generations at Risk <http://www.powells.com/biblio/16-9780262194136-1>,

as well as numerous articles.]

 

Seeking to prevent tooth decay, many U.S. communities add fluoride to public

drinking water, usually in the form of hydrofluorosilicic acid, which is a

waste product of the phosphate fertilizer industry.

 

From the beginning, the practice was controversial, but the Centers for

Disease Control and Prevention (CDC) and American Dental Association (ADA)

have vigorously supported it. The CDC claims that fluoridating public

drinking water is one of the ten great public health achievements of the

20th century, giving it primary credit for the decline in tooth decay in the

U.S. Despite their enthusiasm, abundant evidence raises serious concerns

about the safety and efficacy of adding fluoride to drinking water today.

 

Since 1945, when the public health intervention began, much has changed with

regard to dental health. Several trends are worth mentioning:

 

* Tooth decay has markedly declined in countries and communities that do not

fluoridate drinking water as well as in those that do. Dramatic increases in

the use of topically-applied fluoride-containing oral hygiene products are

likely to have played a role, along with other changes.

 

* Today people are exposed to fluoride from bottled drinks, toothpaste,

fluoride drops and treatments, pesticides, pharmaceuticals, and industrial

discharges. As a result, dental fluorosis, a condition entirely attributable

to excessive fluoride intake, is increasing in a substantial portion of the

U.S. population.[1]

 

* A somewhat surprising trend that may increase risks associated with

fluoride ingestion involves dietary iodine. In recent years, inadequate

iodine intake has become common in the U.S. According to the CDC, the

average urinary iodine level today is half what it was in 1971.[2] The

agency estimates that 36% of U.S. women now have sub- optimal iodine intake.

Adequate dietary iodine is essential for producing normal amounts of thyroid

hormone. Excessive dietary fluoride can also lower thyroid hormone

production. Excess fluoride and inadequate iodine intake combined increase

risks of hypothyroidism.

 

Much research addresses the potential benefits and adverse impacts of

fluoride ingestion. Yet, many data gaps remain. We know that:

 

* Tooth decay is an infectious process and its origins are multifactorial.

General dietary practices, nutrition, oral hygiene, socioeconomic status,

and access to dental care play direct and indirect roles. The relative

contribution of each depends on the context.

 

* To the extent that fluoride helps to prevent tooth decay or slow its

progression, the predominant advantage is from topical application rather

than through ingestion.[3] Topical application includes fluoride in

toothpaste, drops, mouth rinses, and fluoride treatments in a dental office,

as well as from drinking fluoride-containing beverages.

 

* There is little disagreement that ingested fluoride has adverse effects as

exposures increase beyond some amount.[4] The question is, at what level of

exposure do adverse effects begin and when do they begin to outweigh any

potential benefits?

 

* Individuals drinking water with " optimal " fluoride[5] have, on average,

less than one fewer missing, decayed, or filled tooth surface than

individuals whose drinking water does not have added fluoride.[6] With

respect to prevention of tooth decay, therefore, the benefits of fluoride in

drinking water are relatively minor. That is not to say that tooth decay has

not declined during the last 50 years (it has), or that fluoride has not

contributed (it has, but primarily through topical application from many

sources), but rather that putting fluoride in drinking water today plays a

relatively minor role when compared to other variables.

 

* Excessive fluoride ingestion from all sources causes dental fluorosis.

This is not " just " a cosmetic effect. Dental fluorosis interferes with the

integrity of tooth enamel. Many experts conclude that moderate and severe

fluorosis can increase the risk of tooth decay. Severe dental fluorosis

rises sharply when drinking water levels of fluoride exceed 2 ppm [parts per

million].

 

Depending on the level of exposure, a number of adverse health effects may

be linked to fluoride ingestion. In humans, they include bone cancer, bone

fracture, skeletal fluorosis, arthritis, impaired thyroid hormone status,

impaired neurodevelopment of children, and calcification of the pineal

gland. Data are often inconsistent and important information gaps remain. In

general, the threshold exposure level at which the risks of various health

effects significantly increase is not well understood.

 

In 2006, an expert committee convened by the National Academy of Sciences

issued a report

<http://books.nap.edu/openbook.php?record_id=11571 & page=R1>reviewing

the appropriateness of the

U.S. Environmental Protection Agency's current maximum contaminant level for

fluoride in drinking water. The NAS committee concluded:

 

1) " under certain conditions fluoride can weaken bone and increase the risk

of fracture; "

 

2) " high concentrations of fluoride exposure might be associated with

alterations in reproductive hormones, effects on fertility, and

developmental outcomes, but [study] design limitations make those studies

insufficient for risk evaluation, "

 

3) " the consistency of results [in a few epidemiologic studies in China]

appears significant enough to warrant additional research on the effects of

fluoride on intelligence "

 

4) " the chief endocrine effects of fluoride exposures in experimental

animals and in humans include decreased thyroid function, increased

calcitonin activity, increased parathyroid hormone activity, secondary

hyperparathyroidism, impaired glucose tolerance, and possible effects on

timing of sexual maturity. Some of these effects are associated with

fluoride intake that is achievable at fluoride concentrations in drinking

water of 4 mg/L [milligrams per liter] or less, especially for young

children or for individuals with high water intake. "

 

5) " the evidence on the potential of fluoride to initiate or promote

cancers, particularly of the bone, is tentative and mixed. Assessing whether

fluoride constitutes a risk factor for osteosarcoma is complicated by the

rarity of the disease and the difficulty of characterizing biologic dose

because of the ubiquity of population exposure to fluoride and the

difficulty of acquiring bone samples in non-affected individuals. " The

committee said that a soon-to-be published study " will be an important

addition to the fluoride database, because it will have exposure information

on residence histories, water consumption, and assays of bone and toenails.

The results of that study should help to identify what future research will

be most useful in elucidating fluoride's carcinogenic potential. "

 

That study has now been published. It reports a significant association

between exposure to fluoride in drinking water in childhood and the

incidence of osteosarcoma among males.[7]

 

Risks are not limited to humans. Fluoride added to drinking water ultimately

ends up in surface water where levels can be high enough to threaten

survival and reproduction of aquatic organisms, particularly near the point

of discharge.[8]

 

One health endpoint, the potential impact of fluoride on brain development,

illustrates the importance of considering the context of public health

interventions:

 

* We know that adequate thyroid hormone levels are essential during

pregnancy (fetal requirement), infancy, and childhood for normal brain

development. Even relatively minor deficits in maternal thyroid hormone

levels during pregnancy can have long lasting impacts on the function of

children's brains.[9]

 

* Excessive fluoride ingestion lowers thyroid hormone levels.[10] The

threshold at which that effect becomes biologically or clinically important

is uncertain. But we know that it happens in areas with high

naturally-occurring fluoride in drinking water, and it may also be true in

areas with fluoride in drinking water in the range of 1-2 ppm, particularly

when iodine intake is inadequate.

 

* Several studies of children in Chinese communities with fluoride drinking

water levels of 2.5-4 ppm consistently show significantly lower IQ levels

compared to children in communities with minimal fluoride in drinking

water.[11] These studies were controlled for other contributory factors.

 

* Based on biomonitoring studies, the CDC estimates that 36% of women in the

U.S. have inadequate iodine intake. Moreover, approximately 6-7% of women

(the prevalence increases as women age) have sub- clinical hypothyroidism.

Sub-clinical hypothyroidism is characterized by elevated thyroid stimulating

hormone (TSH) and normal thyrotropin (the thyroid hormone T4). Without blood

tests, sub-clinical hypothyroidism is usually unrecognized because it does

not cause symptoms. Sub-clinical hypothyroidism during pregnancy is

associated with decreased IQ in children when measured years later.[12]

 

* Biomonitoring studies conducted by the CDC (NHANES) and other institutions

show virtually ubiquitous human exposure to other environmental contaminants

that also interfere with thyroid hormone levels or function. They include

polychlorinated biphenyls (PCBs), brominated flame retardants,

perfluorinated compounds, and perchlorate (a common drinking water and food

contaminant from rocket fuel, explosives, and imported nitrate fertilizer).

In 2006 CDC scientists reported that ANY amount of perchlorate exposure

significantly lowered thyroid hormone levels in women with inadequate iodine

intake.[13]

 

* Few, if any, communities choosing to add fluoride to drinking water are

likely to have looked into the iodine status of local residents as well as

aggregate exposures to thyroid disrupting compounds, including fluoride,

from all sources combined. Yet, collectively, these factors are undeniably

relevant to brain development of children born in those communities.

Regrettably, the CDC's discussion of the safety of fluoride in drinking

water does not even mention potential impacts on the developing brain.[14]

 

With respect to current and historical perspectives, the NAS committee noted

that, on average, fluoride exposure from drinking water in fluoridated

communities is near or exceeds the level that raises health concerns.[15]

That is, virtually no " margin of safety " exists between levels of fluoride

intended to be beneficial and those that may be harmful. This is in sharp

distinction from the margin of safety when essential nutrients such as

iodine, vitamin D, or vitamin C are added to food. In those cases, maximum

potential intake is orders of magnitude lower than exposures that may have

toxic effects. Population-wide monitoring of fluoride exposures in the U.S.

is surprisingly inadequate. This is particularly disturbing since, despite

vigorously recommending putting fluoride into drinking water, the CDC has

failed to monitor systematically the levels of fluoride in the population --

despite steadily increasingly sources of fluoride, increasing dental

fluorosis, and their well-known and highly useful population-wide monitoring

program for a number of other environmental agents (NHANES). Why not

fluoride? The NAS review said, " Fluoride should be included in nationwide

biomonitoring surveys and nutritional studies... In particular, analysis of

fluoride in blood and urine samples taken in these surveys would be

valuable. "

 

Conclusions:

 

Because of

 

a) uncertainties surrounding fluoride exposure levels from all sources,[16]

 

b) concurrent exposures to other environmental agents that interact with

fluoride or add to the impacts of fluoride,

 

c) estimates of efficacy and benefits of adding fluoride to drinking water

compared with alternative interventions, and

 

d) potential adverse health effects at current and anticipated exposure

levels,

 

** intentionally fluoridating community drinking water is no longer

justified. Adding fluoride to drinking water for the purpose of preventing

tooth decay provides virtually no population-wide margin of safety. Under

current circumstances, people should not be essentially forced to drink

water treated with fluoride when dental benefits can be achieved through

topical application and other means.

 

** An immediate moratorium on the practice of adding fluoride to community

drinking water is justified. Risks, benefits, efficacy, and alternatives

must be fully, impartially, and transparently re- evaluated, based on

current information and data gaps. Moreover, an ethical review of the

practice is warranted.

 

Public health interventions can take many directions. Few, however, are as

intrusive as intentionally putting a biologically active chemical into

drinking water. Everyone in the community, without exception, is exposed

without any opportunity to " opt out " based on individual circumstances.

Promoters of this kind of intervention, therefore, have a special

responsibility and should at least:

 

1) Regularly, comprehensively, and transparently re-evaluate benefits and

risks of the intervention, based on current science and available

alternatives,

 

2) Regularly monitor and disclose exposure levels in current

contexts/circumstances (in humans and wildlife),

 

3) Ensure an adequate margin of safety, including for the most vulnerable,

and

 

4) Consider the ethical dimensions of intentionally adding a biologically

active chemical to public drinking water.

 

In 2006, the American Dental Association issued an interim guidance advising

parents not to reconstitute infant formula with fluoridated water because of

the risk of causing dental fluorosis. In general, however, public health

agencies and professional associations that advocate putting fluoride into

drinking water have failed to provide up-to-date, regular, comprehensive,

and transparent re-evaluations of benefits and risks of fluoridating

drinking water, based on the most current science and available

alternatives. They have not systematically monitored fluoride levels in

people and wildlife, adjusting recommendations according to their findings.

Rather, they have continued to stress, and often exaggerate, benefits of

ingested fluoride while downplaying the risks. Hopefully, the NAS review

will prompt an impartial re-evaluation of the justification, safety, and

appropriateness of this 50-year-old practice.

 

[1] http://www.cdc.gov/mmwr/preview/mmwrhtml/ss5403a1.htm

 

[2] http://www.cdc.gov/nchs/products/pubs/pubd/hestats/iodine.htm

 

[3] Discussed in a recent National Academy of Sciences report, " Fluoride in

Drinking Water: A Scientific Review of EPA's

Standards<http://books.nap.edu/openbook.php?record_id=11571 & page=R1> "

(2006) This is a review of the appropriateness of EPA's 4 ppm maximal

contaminant level goal for fluoride in drinking water. The committee was not

charged with considering the risks and benefits of adding fluoride to

drinking water for preventing tooth decay.

 

The CDC agrees that the benefits of fluoride are primarily from topical

application in children and adults. See

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm4841a1.htm

 

[4] NAS review http://books.nap.edu/openbook.php?record_id=11571 & page=R1

 

[5] The CDC considers 0.7-1.2 ppm fluoride in drinking water to be optimal

 

[6] Brunelle J, Carlos J. Recent trends in dental caries in US children and

the effect of water fluoridation. Journal of Dental Research. Vol 69,

special issue. 723-727, 1990.

 

[7] Bassin E, Wypij D, Davis R, Mittleman M. Age-specific fluoride exposure

in drinking water and osteosarcoma (United States). Cancer Causes Control.

17(4):421-428, 2006.

 

[8] Camago J. Fluoride toxicity to aquatic organisms: a review. Chemosphere.

50(3):251-64, 2003.

 

[9] LaFranchi S, Haddow J, Hollowell J. Is thyroid inadequacy during

gestation a risk factor for adverse pregnancy and developmental outcomes?

Thyroid. 15(1):60-71, 2005.

 

[10] Discussed in the NAS review. See

http://books.nap.edu/openbook.php?record_id=11571 & page=224.

 

[11] Discussed in the NAS review. See

http://books.nap.edu/openbook.php?record_id=11571 & page=205.

 

[12] LaFranchi S, Haddow J, Hollowell J. Is thyroid inadequacy during

gestation a risk factor for adverse pregnancy and developmental outcomes?

Thyroid. 15(1):60-71, 2005.

 

[13] Blount B, Pirkle, J, Osterloh J, et al. Urinary perchlorate and thyroid

hormone levels in adolescent and adult men and women living in the United

States. Environ Health Perspect 114(2):1865-71, 2006.

 

[14] http://www.cdc.gov/fluoridation/safety.htm

 

[15] See http://books.nap.edu/openbook.php?record_id=11571 & page=83. For

example, in 2005 the American Dental Association

declared<http://www.ada.org/public/topics/fluoride/facts/fluoridation_facts.pdf>\

that

the " tolerable upper intake " of fluoride for children 0-8 years of age

is 0.10 mg/kg/day. In 1997, the Institute of Medicine found that the average

intake of fluoride from drinking water for children living in fluoridated

communities was 0.05-0.13 mg/kg/day.

 

[16] See page 87 of the NAS

review<http://books.nap.edu/openbook.php?record_id=11571 & page=87>for

recommendations regarding exposure data gaps.

 

http://www.precaution.org/lib/07/prn_commentary_on_fluoride.070801.htm