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fluosilicic

Water fluoridation

Water fluoridation is the addition of a chemical to increase the concentration of fluoride ions in drinking water with the purpose of reducing the incidence of tooth decay. Fluoride compounds are found naturally in the ground water in some regions, such as Colorado.. Fluoridation chemicals are typically added to potable water in the form of sodium hexafluorosilicate or hexafluorosilicic acid (also known as hydrofluorosilic acid).

History

While the use of fluorides for prevention of dental caries (cavities) was discussed in the 19th century in Europe, 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." The condition, now known as dental fluorosis, when in its severe form is characterized by cracking and pitting of the teeth. 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. 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). 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.

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. 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. 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 1939, Dr. Gerald J. Cox conducted laboratory tests using rats that were fed aluminum and fluoride. The anti-carries data from his studies were described as, "inconclusive" and, "anything but convincing," by fluoride historian Peter Meiers. But Dr. Cox suggested adding fluoride to drinking water (or other media such as milk or bottled water) in order to improve oral health. 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. 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.

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. Kingston, New York was paired with Newburgh, New York. Oak Park, Illinois was paired with Evanston, Illinois. Sarnia, Ontario was paired with Brantford, Ontario, Canada.

In 1951, a member of the Newburgh - Kingston Fluoridation Committee, Katherine Bain, stated: "the technical committee set up to work with that study set itself a goal which it wasn´t able to achieve. It had hoped to keep the study under wraps for ten years, and at the end of ten years come out with a definitive answer about what fluoride did, what its harmful effects might be. As you know, that study and other studies began having such results that people became interested, and the pressure was such that people felt we must go ahead with these programs." The Newburgh-Kingston study has been sharply criticized by the Fluoride History website for its, "ludicrous inadequacy," and for engaging in, "obvious manipulations." 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. 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. 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.

Efficacy, effects, and cost-benefit analysis

Fluoride, while toxic at moderate to high doses, may be beneficial for dental health at low doses. 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." In 2001, the US Centers for Disease Control and Prevention stated that "solid data on the cost-effectiveness of fluoride modalities alone and in combination are needed...this information is scarce". In 1983, health economists concluded that "water fluoridation is one of the few public health measures that results in true cost savings." A comprehensive systematic review of the evidence by the University of York was "unable to discover any reliable good-quality evidence in the fluoridation literature world-wide." The review concluded that fluoridation was likely to have a beneficial effect on teeth, but that the effect ranged from a substantial benefit to a slight disbenefit with a median of 14.6% increase in caries free individuals. It is estimated that a median of 6 people drinking fluoridated water would result in one caries free person. According to the CDC, when used appropriately, fluoride is a safe and effective agent to prevent and control dental caries throughout the lifespan and that fluoride has contributed profoundly to the improved dental health of persons in the United States and other countries.

Dental fluorosis

Most cases of fluorosis are mild and will appear as tiny white specks or streaks that are often unnoticeable.

The damage in tooth development occurs between the ages of 6 months to 5 years, from the overexposure to fluoride. In its severe form it is characterized by black and brown stains, as well as cracking and pitting of the teeth.

The World Health Organization cautions that fluoride levels above 1.5 milligrams per liter leaves the risk for fluorosis. To protect against this health organizations in some high fluoride areas endorse providing alternative water sources, or removing fluoride from the water. 0.07 – 1.2 milligrams per liter 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.

Recommendations for Using Fluoride to Prevent and Control Dental Caries in the United States, Morbidity and Mortality Weekly Report, August 17, 2001, Centers for Disease Control and Prevention Many communities need to reduce fluoride exposure. Consumption of water exceeding 10 ppm fluoride has been shown to lead to pathological changes in bone structure, and skeletal fluorosis. 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.

Possible 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, but may have a daily fluoride intake of between 1 – 3 mg/day, as men are recommended to drink 3 liters/day and women 2.2 liters/day. In 1986 the United States Environmental Protection Agency (EPA) established a maximum contaminant level (MCL) for fluoride at a concentration of 4 milligrams per liter (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 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. The limit was previously 1.4 – 2.4 mg/L, but it was raised to 4 mg/L in 1985.

Those who question the cost-benefits of fluoridation express the greatest concern for vulnerable populations, and the National Research Council states that children have a higher daily average intake than adults per kg of bodyweight. 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. 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, 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. 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. 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.

A panel member of the NRC report, Kathleen M. Thiessen, writes that the report does seem relevant to the debate over the cost-benefits of fluoridation, and that the "margin of safety between 1 mg/L and 4 mg/L is very low" because of the uncontrolled nature of the dosage. In her opinion fluoride intake should be minimized. John Dull, the chair of the panel, stated that "the thyroid changes worry me ... we’ve gone with the status quo regarding fluoride for many years—for too long, really—and now we need to take a fresh look ... I think that’s why fluoridation is still being challenged so many years after it began. In the face of ignorance, controversy is rampant". Hardy Limeback, another panel member, stated "the evidence that fluoridation is more harmful than beneficial is now overwhelming and policy makers who avoid thoroughly reviewing recent data before introducing new fluoridation schemes do so at risk of future litigation". Another panel member, Robert Isaacson, stated that "this report should be a wake-up call" and said that the possible effects on the endocrine gland and hormones are "something that I wouldn’t want to happen to me if I had any say in the matter." But, Tom Maier, an assistant biosciences professor at the OHSU School of Dentistry, pointed out that the NAS panel besides saying the current EPA maximum on fluoride in water is unsafe mainly called for more definitive research and that policy change is not needed at this point.

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. 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.
  • Adverse effects on the kidney. Within the optimal 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. Those with impaired kidney function are more susceptible to adverse effects.
  • Little research has been done on possible liver damage, although some studies suggest negative effects at chronic ingestion of 23 mg/day.
  • Chromosomal damage and interference with DNA repair. Overall, the literature from in vitro and rodent studies does not indicate genotoxicity, but the in vivo human studies are inconsistent.
  • Four epidemiological studies have noted a correlation between increased fluoride and low IQ. 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 liter [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.
  • Inhibition of melatonin production and promotion of precocious puberty in animal studies. Fluoride may have an analogous inhibitory effect on human melatonin production, as fluoride accumulates readily in the human pineal gland, the brain organ responsible for melatonin synthesis.
  • A weakened immune system, leaving people vulnerable to the development of cancer and AIDS.
  • Damage to the male reproductive system in various species.
  • A disruption in endocrine function, especially in the thyroid.

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.

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.

Opposition

Water fluoridation opposition refers to activism against the addition of fluoride chemicals to public water supplies. Beyond the fact that the general public is involuntarily exposed to this chemical, concerns include the lack of quality research data available, evidence that it may cause serious health problems, and ethical issues. In the United States, it has been the subject of conspiracy theories alleging that fluoridation is part of a Neo-Con, "New World Order" socialist plot to undermine the health and intelligence of the American public.

Fluoridation around the world

Water fluoridation is most common in English-speaking countries, but it is also common in Brazil, Chile, Colombia, Israel and Malaysia. Continental Europe largely does not fluoridate water although a number of the countries in the region fluoridate salt. For example, in Colombia, Costa Rica, parts of Switzerland, Germany, and France, table salt is dosed with potassium fluoride. 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. Notable English-speaking countries which do not fluoridate water are Northern Ireland and Scotland.

Malfunctions in equipment

At least 17 incidences of fluoridation equipment malfunction, and their associated deaths and poisonings, have been documented in U.S. newspapers and medical journals. 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. 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.”

Alternative methods of fluoridation

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. 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.

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.

Bottled water

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

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.

See also

References

External links

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