Water fluoridation

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Water fluoridation is the controlled addition of fluoride to a public water supply in order to reduce tooth decay.^[1] Its use in the U.S. began in the 1940s, following studies of children in a region where water is naturally fluoridated; too much fluoridation causes dental fluorosis, which mottles or stains teeth, but U.S. researchers discovered that moderate fluoridation prevents cavities.^[2] Water fluoridation has been contentious for ethical, safety, and efficacy reasons, and only about 5.7% of people worldwide drink fluoridated water.^[3]

[edit] History

The history of water fluoridation can be divided into three periods. The first (c. 1901–33) was research into the cause of a form of mottled enamel called "Colorado brown stain", which later became known as fluorosis. The second (c. 1933–45) focused on the relationship between fluoride concentrations, fluorosis, and tooth decay. The third period, from 1945 on, focused on adding fluoride to community water supplies.^[2]

[edit] Colorado brown stain

Photograph of Dr. G.V. Black (left) and Drs. Isaac Burton and F. Y. Wilson, 1909, studying the "Colorado Brown Stain" (picture taken by McKay, printed in Douglas W.A.:"History of dentistry in Colorado, 1859-1959").

While the use of fluorides for prevention of dental caries (cavities) was discussed in the 19th century in Europe,^[4] community water fluoridation in the United States owes its origin in part to the research of Dr. Frederick McKay, who pressed the dental community for an investigation into what was then known as "Colorado Brown Stain."^[5] The condition, now known as dental fluorosis, when in its severe form is characterized by cracking and pitting of the teeth.^[6][7][8] Of 2,945 children examined in 1909 by Dr. McKay, 87.5% had some degree of stain or mottling. All the affected children were from the Pikes Peak region. Despite the negative impact on the physical appearance of their teeth, the children with stained, mottled and pitted teeth also had fewer cavities than other children. McKay brought the problem to the attention of Dr. G.V. Black, and Black's interest into the Colorado stain led to greater interest throughout the dental profession.

Initial hypotheses for the staining included poor nutrition, overconsumption of pork or milk, radium exposure, childhood diseases, or a calcium deficiency in the local drinking water.^[5] In 1931, researchers from the Aluminum Company of America (ALCOA) finally concluded that the cause of the Colorado stain was a high concentration of fluoride ions in the region's drinking water (ranging from 2 to 13.7 ppm) and areas with lower concentrations had no staining (1 ppm or less).^[9] Pikes Peak's rock formations contained the mineral cryolite, one of whose constituents is fluorine. As the rain and snow fell, the resulting runoff water dissolved fluoride which made its way into the water supply.

Dental and aluminum researchers then moved toward determining a relatively safe level of fluoride chemicals to be added to water supplies. The research had two goals: (1) to warn communities with a high concentration of fluoride of the danger, initiating a reduction of the fluoride levels in order to reduce incidences of fluorosis, and (2) to encourage communities with a low concentration of fluoride in drinking water to add fluoride chemicals in order to help prevent tooth decay. By 2006, 69.2% of the U.S. population on public water systems was receiving fluoridated water, amounting to 61.5% of the total U.S. population; 3.0% of the population on public water systems were receiving naturally occuring fluoride.^[10]

[edit] Early studies

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A study of varying amounts of fluoride in water was led by Dr. H. Trendley Dean, a dental officer of the U.S. Public Health Service.^[11][12] In 1936 and 1937, Dr. Dean and other dentists compared statistics from Amarillo, which had 2.8 - 3.9 ppm fluoride content, and low fluoride Wichita Falls. The data is alleged to show less cavities in Amarillo children, but the studies were never published.^[13] Dr. Dean's research on the fluoride-dental caries relationship, published in 1942, included 7,000 children from 21 cities in Colorado, Illinois, Indiana, and Ohio. The study concluded that the optimal amount of fluoride which minimized the risk of severe fluorosis but had positive benefits for tooth decay was 1 mg per day, per adult. Although fluoride is more abundant in the environment today, this was estimated to correlate with the concentration of 1 part per million (ppm).

In 1937, dentists Henry Klein and Carroll E. Palmer had considered the possibility of fluoridation to prevent cavities after their evaluation of data gathered by a Public Health Service team at dental examinations of Native American children.^[14] In a series of papers published afterwards (1937-1941), yet disregarded by his colleagues within the U.S.P.H.S., Klein summarized his findings on tooth development in children and related problems in epidemiological investigations on caries prevalence.^{[citation needed]}

In 1939, Dr. Gerald J. Cox^[15] conducted laboratory tests using rats that were fed aluminum and fluoride. Dr. Cox suggested adding fluoride to drinking water (or other media such as milk or bottled water) in order to improve oral health.^[16]

In the mid 1940s, four widely cited studies were conducted. The researchers investigated cities that had both fluoridated and unfluoridated water. The first pair was Muskegon, Michigan and Grand Rapids, Michigan, making Grand Rapids the first community in the world to add fluoride chemicals to its drinking water to try to benefit dental health on January 25, 1945.^[17] Kingston, New York was paired with Newburgh, New York.^[18] Oak Park, Illinois was paired with Evanston, Illinois. Sarnia, Ontario was paired with Brantford, Ontario, Canada.^[19]

In 1952 Nebraska Representative A.L. Miller complained that there had been no studies carried out to assess the potential adverse health risk to senior citizens, pregnant women or people with chronic diseases from exposure to the fluoridation chemicals.^[13] A decrease in the incidence of tooth decay was found in some of the cities which had added fluoride chemicals to water supplies. However, tooth decay was declining in similar rates in non-fluoridated cities.^[20] The early comparison studies would later be criticized as, "primitive," with a, "virtual absence of quantitative, statistical methods...nonrandom method of selecting data and...high sensitivity of the results to the way in which the study populations were grouped..." in the journal Nature.^[21]

[edit] Mechanism

Fluoride compounds are found naturally in the ground water in some regions, such as Colorado.^[22]. Fluoridation chemicals are typically added to potable water in the form of sodium hexafluorosilicate or hexafluorosilicic acid (also known as hydrofluorosilic acid or fluorosilic acid).^[23][24] This acid is largely a byproduct of phosporic acid plants which process phosphate rock.^[25] Since 2005, reduced phosphate processing has led to an increase in the price of fluorosilic acid, with one community seeing a 105% price increase in the past two years.^[26]

[edit] Efficacy, effects, and cost-benefit analysis

When used appropriately, fluoride use is a safe and effective way to prevent and control dental caries, and has contributed to dental health worldwide of both children and adults.^[1] The recommended dosage of fluoride for humans from the CDC is 0.7 ppm to 1.2 ppm depending on the average maximum daily air temperature of the area. Fluoridation is intended to reduce tooth decay, with its associated health problems, at a low cost. Fluoridation of the public water supply is the "most equitable, cost-effective, and cost-saving method of delivering fluoride to the community." ^[27] In 2001, the US Centers for Disease Control and Prevention stated, "Although solid data on the cost-effectiveness of fluoride modalities alone and in combination are needed, this information is scarce."^[1] A 1989 workshop on cost effectiveness of caries prevention concluded that water fluoridation is one of the few public health measures that saves more money than it costs to operate.^[1] A 2000 comprehensive systematic review of the evidence stated that "it is surprising to find that little high quality research has been undertaken". The review found that fluoridation was associated with a decreased proportion of children with cavities (the range of mean decreases was −5% to 64%, the median 14.6%), and with a decrease in decayed, missing, and filled primary teeth (the range of mean decreases was 0.5 to 4.4 teeth, the median 2.25 teeth). It also found that at a fluoride level of 1 ppm an estimated 12.5% (range 7% to 21.5%) of people would have fluorosis they would find aesthetically concerning, and that there was no clear evidence of other adverse effects.^[28]

[edit] Possible adverse health effects

Negative health effects are generally associated with fluoride intake levels above the commonly recommended dosage, which is accomplished by fluoridating the water at 0.7 – 1.2 mg/L (0.7 for hot climates, 1.2 in cool climates). This was based on the assumption that adults consumes 2 L of water per day,^[29]:345 but may have a daily fluoride intake of between 1 – 3 mg/day, as men are recommended to drink 3 litres/day and women 2.2 litres/day.^[30] In 1986 the United States Environmental Protection Agency (EPA) established a maximum contaminant level (MCL) for fluoride at a concentration of 4 milligrams per litre (mg/L), which is the legal limit of fluoride allowed in the water. In 2006, a 12-person committee of the US National Research Council (NRC) reviewed the health risks associated with fluoride consumption^[29] and unanimously concluded that the maximum contaminant level of 4 mg/L should be lowered. The EPA has yet to act on the NRC's recommendation.^[31][32] The limit was previously 1.4 – 2.4 mg/L, but it was raised to 4 mg/L in 1985.^[33]

A mild case of fluorosis, with faint white mottling.

The World Health Organization cautions that fluoride levels above 1.5 milligrams per litre leaves the risk for fluorosis.^[34] Consumption of water exceeding 10 ppm fluoride has been shown to lead to pathological changes in bone structure, and skeletal fluorosis.^{[35] [36]} 0.07 – 1.2 milligrams per litre of fluoride is considered to be the optimal level. A CDC evaluation concluded that prevalence of some level of fluorosis among children and adolescents in the United States had increased by from 22.8% in 1986 – 1987 to 32% in 1999 – 2002.^[37] Debilitating environmental fluorosis of a portion of the population is a problem in several developing countries, where it is complicated by malnutrition. The effects of skeletal fluorosis can be slowly reversed through a reduction of fluoride intake and improved diet.^[38] To protect against this health organizations in some high fluoride areas endorse providing alternative water sources, or removing fluoride from the water.^[39]

The National Research Council states that children have a higher daily average intake than adults per kg of bodyweight.^[29]:23 Those who work outside, or have urine problems also will drink more water. Osteosarcoma, a rare bone disease affecting male children, has been associated with fluoride intake^{[citation needed]}. The weight of the evidence, as assessed by independent committees of experts, comprehensive systematic reviews, and review of the findings of individual studies does not support an association between water fluoridated at levels optimal for oral health and the risk for cancer, including osteosarcoma, ^[40] although a study described as the most rigorous yet by the Washington Post found a relationship among young male boys. The authors' adviser faced an investigation based on his dismissal of the results and an apparent conflict of interest.^[41] An epidemiological connection between areas with high intake of silicofluorides and increased lead blood levels in children has been observed in areas fluoridated at the recommended dosage.^[42][43] A 2007 update on this study confirmed the result and noted that silicofluorides, fluosilicic acid and sodium fluosilicate are used to fluoridate over 90% of US fluoridated municipal water supplies.^[44]

Excess fluoride consumption has been studied as a factor in the following:

• A weakening of bones, leading to an increase in hip and wrist fracture.^[45] The National Research Council found the overall evidence "suggestive but inadequate for drawing firm conclusions about the risk or safety of exposures at [2 mg/L]", but states that fractures do seem to increase as fluoride is increased from 1 mg/L to 4 mg/L, suggesting a "continuous exposure-effect" dose-response relationship at these levels.^[29]:170

• Adverse effects on the kidney. Within the recommended dose, no effects are expected, but chronic ingestion in excess of 12 mg/day are expected to cause adverse effects, and an intake that high is possible when fluoride levels are around 4 mg/L.^[29]:281 Those with impaired kidney function are more susceptible to adverse effects.^[29]:292

• Little research has been done on possible liver damage, although some studies suggest negative effects at chronic ingestion of 23 mg/day.^[29]:292

• Chromosomal damage and interference with DNA repair.^[29]:304 Overall, the literature from in vitro and rodent studies does not indicate genotoxicity, but the in vivo human studies are inconsistent.^[29]:316

• Four epidemiological studies have noted a correlation between increased fluoride and low IQ.^[29]:205-223 The most rigorous of these compared an area with mean water concentration of 0.36 ± 0.15 mg/L (range 0.18-0.76 mg/L) to an area with 2.47 ± 0.79 mg/L (range 0.57-4.50 milligrams per litre [mg/L]). Most of these studies did not publish important details, making them difficult to evaluate. If these correlations are caused by fluoride, the mechanism is not known, but the National Research Council speculates that effects on the thyroid could lead to poor test results.^[29]:208

[edit] Endorsements

The American Dental Association states on their website that many prominent organizations endorse water fluoridation, including the World Health Organization, the Centers for Disease Control and Prevention, and the American Medical Association.^[46]

On April 2, 1999, the U.S. Centers for Disease Control and Prevention listed water fluoridation as one of the 10 greatest public health achievements of the 20th century.^[47]

[edit] Opposition

Main article: Water fluoridation opposition

Water fluoridation has been contentious for ethical, safety, and efficacy reasons.^[3] Concerns include the alleged lack of available data,^[28] evidence that extreme doses may cause serious health problems,^{[45][48][49][50][51][52][53][54][55][56][57][58][59][60]} and ethical issues.^{[61][62][63][64]} In the United States, it has been the subject of conspiracy theories alleging that fluoridation is part of a Neo-Con, "New World Order" plot to undermine the health and intelligence of the American public.^[65]

[edit] Fluoridation around the world

Main article: Fluoridation by country

About 5.7% of people worldwide drink fluoridated water;^[3] this includes 62.5% of the U.S. population.^[10] 12 million people in Western Europe have fluoridated water, mainly in England, Spain, and Ireland. France, Germany, and some other European countries use fluoridated salt instead; the Netherlands, Sweden, and a few other European countries rely on fluoride supplements and other measures.^[66] The justification for water fluoridation is analogous to the use of iodized salt for the prevention of goiters. China, Japan, the Philippines, and India do not fluoridate water.^[67]

[edit] Malfunctions in equipment

Main article: Fluoride poisoning

At least 17 incidences of fluoridation equipment malfunction, and their associated deaths and poisonings, have been documented in U.S. newspapers and medical journals.^[68] The largest incident occurred in Hooper Bay, Alaska in 1992. When fluoridation equipment failed, a large amount of fluoride was released into the drinking water supply and 296 people were poisoned; 1 person died.^[68] 3 dialysis patients died and 6 were sickened at the University of Chicago Hospitals when the water filtration system failed on July 16, 1993. A hospital spokesperson said that the deaths and reactions “were consistent with fluoride exposure.”^[68]

[edit] Alternative methods of fluoridation

[edit] Milk

Fluoridation of milk is being practiced by the Borrow Foundation in some parts of Bulgaria, Chile, Peru, the Russian Federation, Thailand and the United Kingdom^[69][70]. A pilot fluoridated milk program was in effect in the Haidian district of Beijing, China from 1994 through 1999 where laws forbidding fluoridation were passed, the University of Hong Kong and National Committee for Oral Health work with the Borrow Foundation and some Chinese dentists to re introduce fluoridated milk^[71].

[edit] Salt

Salt was first fluoridated in Switzerland in 1955 followed by France in 1986 and shortly after by Jamaica and Costa Rica. Costa Rica, Jamaica and Colombia today practice universal salt fluoridation, whereby all salt bound for human consumption is fluoridated, this includes salt that is added to ready prepared food, and where no fluoride free salt is available.^[72]

[edit] Bottled water

Some dental professionals are concerned that the growing use of bottled water may decrease the amount of fluoride exposure people will receive.^[73] Some bottlers such as Danone have begun adding fluoride to their water.^[74] On April 17, 2007, Medical News Today stated, "There is no correlation between the increased consumption of bottled water and an increase in cavities."^[75]

In October 2006, the United States Food and Drug Administration issued a health claim notification permitting water bottlers to claim that fluoridated bottled water can promote oral health. The claims are not allowed to be made on bottled water marketed to infants.^[76]

[edit] See also

• Fluoride
• Fluoride therapy
• Fluorine deficiency
• hexafluorosilicic acid
• Water fluoridation opposition

[edit] References

[edit] External links

• Fluoridation at the Open Directory Project