Does the addition of fluoride to drinking water cause significant harm to humans

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MEDICINE

Does the addition of fluoride to drinking water cause significant harm to humans?

Viewpoint: Yes, the evidence is clear that significant concentrations of fluoride in drinking water cause harm to humans.

Viewpoint: No, the addition of small amounts of fluoride to drinking water does not cause significant harm to humans and provides several benefits.

Throughout history, dental caries—that is, decay of the teeth—has been the principal problem of dentistry. During the 1880s, Willoughby D. Miller, a student of the great German bacteriologist Robert Koch, showed that microorganisms are involved in the development of dental caries. Miller's findings were published in his book Microorganisms of the Human Mouth (1890). Following the path established by Miller, J. Leon Williams then demonstrated that bacteria in dental plaque produce the acid that attacks tooth enamel. Williams believed that good dental hygiene would prevent decay. Although until the twentieth century dentists could do little but remove affected teeth, the concept of preventive dentistry had been promoted as early as the eighteenth century. Since the 1930s dentists have attempted to prevent caries by reducing the acid-forming microorganisms in the mouth, or by using chemicals to inhibit the formation of acid and make the teeth less susceptible to acid. Researchers have investigated various chemicals, including fluorides, ammonium compounds, and penicillin. The best known and most controversial is sodium fluoride, which has been added to the drinking water of many communities.

What Is Fluoride?

Fluorine, a member of the halogen family in the periodic table of elements, is a very reactive chemical element. In nature, fluorine is primarily found in the widely distributed mineral called fluorspar (calcium fluoride) and in combination with aluminum in cryolite. Fluoride, a binary compound of fluorine, is found in varying amounts in drinking water and in foods, but scientists estimated that the intake of fluoride by the average adult was between 0.7 and 3.4 mg per day. In areas where the concentration of fluoride was relatively high, characteristic signs usually appeared on the teeth. These include dull white patches, pitting, or brown stains and a mottled appearance. The addition of high levels of fluoride to the diet of experimental animals affects calcium and phosphorus metabolism and produces fragility of the teeth and bones. However, the addition of small amounts of fluoride seemed to strengthen tooth enamel and prevent the development of dental caries. No other element seemed to have such an effect on tooth enamel. Thus, animal studies suggested that appropriate levels of fluoride might prevent tooth decay either by making the structure of the tooth more resistant to decay, or by inhibiting the bacterial action on food particles that promotes decay.

The relationship between fluoride and mottling of the teeth was noted by Frederick Sumter McKay when he moved to Colorado Springs, Colorado, in 1901 to establish a dental practice. About 90% of the people who had grown up in the Colorado Springs region had strange brown stains on their teeth. Although area dentists had little interest in the condition, McKay found evidence that people with mottled brown teeth had fewer cavities. In the 1920s, McKay and collaborators found a correlation between the brown stains and fluorides in the water supply. Further studies of the relationship between fluoride concentration and staining were carried out by Henry Trendley Dean, chief of the Dental Hygiene Unit at the National Institute of Health. Dean and his associates found that when the level of fluorides exceeded 1 part per million (ppm), fluoride began to accumulate in tooth enamel.

In 1938 the United States Public Health Service (USPHS) conducted a study of fluorides and dental conditions in two communities in Illinois. The children in Galesburg, where tooth mottling was common and the water contained fluorides, had fewer cavities than those in Quincy. After extensive testing in animals to determine that the addition of fluorides to water was safe, the USPHS began testing the effect of adding sodium fluoride to the water systems in Newburgh, New York, and Grand Rapids, Michigan. Researchers concluded that the use of fluorides reduced dental caries by about 60%. Based on several comparative studies, the USPHS recommended that all communities add fluorides to their public water supply so that the level would be 1 ppm. In 1951 the American Dental Association (ADA) officially endorsed fluoridation.

The Opposition Speaks Out

Although the dental, public health, and medical communities strongly supported fluoridation, many groups were actively opposed. Some surveys indicated that about 30% of Americans objected to fluoridation of their water supply. Some people opposed the addition of "unnatural" chemicals to their water, arguing that fluorides were toxic and caused many different diseases. Among the reasons cited was the fact that there is little margin of safety between the level of fluoride that is supposed to prevent dental decay and the level that causes deleterious health effects. Now that fluoride has been added to other products, such as toothpaste and mouthwash, and is found in air and food contaminants, critics contend that total intake is unpredictable and excessive. Moreover, critics believe that dangerous amounts of fluoride can accumulate in the body because of long-term exposure to numerous sources of fluorides, including insecticides, Scotch-guard, and Teflon.

Opponents of fluoridation claim that fluorine is a toxic agent that causes serious health problems. People with diabetes and kidney disorders could be at special risk. High levels are said to cause mottling of the teeth, deformities of the spine, joint problems, muscle wasting, neurological defects, arthritis, osteoporosis (a decrease in bone mass), hip fractures, infertility, genetic mutations, Down's syndrome (a form of congenital mental retardation), and all forms of cancer. Lower levels are said to cause eczema, dermatitis, headache, chronic fatigue, muscular weakness, mouth ulcers, lower urinary tract infections, and the aggravation of existing allergies. In addition to associating fluoride with various disease conditions, critics also charge that fluoridation does not really reduce tooth decay. Certain studies are cited as proof that children who drank fluoridated water actually had more decay than did children residing in areas without fluoridated water.

Much of the debate about fluoridation has been political rather than medical. Indeed, during the 1950s, at the height of the Cold War (a period characterized by diplomatic tensions between the United States and the former Soviet Union), critics argued that the fluoridation of American water supplies was part of a Communist plot. Whether or not fluoridation causes significant harm or not, many people object to compulsory medication as an infringement on personal liberty.

Supporters Emphasize the Merits of Fluoridation

Public health workers, in contrast, consider fluoridation to be one of the greatest public health achievements of the twentieth century. Some authorities believe that fluoridation of public water supplies deserves to be ranked with pasteurization of milk, purification of water, and immunization against infectious diseases. All of these measures met with fierce opposition and triggered controversies that involved both scientific and political issues. Public health measures, by their very nature, must reach almost the whole population, and many such actions must be compulsory to achieve a public good. For example, immunizations are required before a child can enter public school, and people suffering from contagious diseases may be quarantined. People who object to adding chemicals to water ignore the fact that drinking water must be treated in order to make it safe. In part, such objections reflect the success of public health measures. By the beginning of the twenty-first century, few people remembered that contaminated drinking water caused deadly epidemics of typhoid fever and cholera, and unpasteurized milk was a source of tuberculosis.

Those who support the fluoridation of drinking water argue that many years of study have shown that the process is safe and effective in reducing tooth decay. They charge opponents with using safety issues as a screen for other kinds of objectives that are more political than medical. In answer to claims that fluoridation causes many serious diseases, public health officials argue that carefully controlled comparative studies have not revealed any significant difference in the health, growth, and development of those who drank fluoridated water and those who did not. The only statistically significant difference appeared to be a reduction in tooth decay. Statistical studies of large populations, however, cannot rule out the possibility that some individuals might be sensitive to fluoridation, just as some individuals are sensitive to strawberries, or peanuts, or penicillin.

According to the ADA, fluoridation of community water supplies and the use of fluoride-containing products constitute safe and effective approaches to preventing tooth decay. The ADA has continuously endorsed these measures for over 50 years. Nevertheless, the addition of fluoride to drinking water continues to provoke significant opposition. Despite reassurances by the medical, dental, and public health communities, opponents of fluoridation argue that the practice is neither safe nor effective.

—LOIS N. MAGNER

Viewpoint: Yes, the evidence is clear that significant concentrations of fluoride in drinking water cause harm to humans.

Fluoride has never received United States Food and Drug Administration (FDA) approval and is listed as a contaminant by the Environmental Protection Agency (EPA). Fluoride is the agent used by cities all over the world to fluoridate their municipal water supplies. According to the Centers for Disease Control and Prevention (CDC), today over 62% of United States cities fluoridate their water supplies. In 1944, the federal government instituted fluoridation of municipal water supplies as a public health measure to help prevent tooth decay. The "fluoride intake" standard for optimal benefit for teeth was set between 0.7 and 1.2 ppm (parts per million) or mg/L (milligrams per liter). At that time, fluoride was not available from other sources, such as toothpaste or mouth rinses, as it is today. In addition to fluoridated water and fluoride-enhanced dental products, fluoride can be found in food, beverages, fluoride-based pharmaceuticals (e.g., Prozac [fluoxetine]), air emissions, and the work place. The use of fluoride over the past 50 years has been linked in government and scientific reports to some very serious national health problems—dental fluorosis (irreversible mottling, staining, and pitting of teeth); crippling skeletal fluorosis (deformities of the spine and major joints, muscle wasting, and neurological defects); arthritis; osteoporosis (a decrease in bone mass); hip fractures; infertility; and all types of cancers.

Maximum Contaminant Levels (MCLs)

In 1986, the EPA set new maximum contaminant levels (MCLs) for fluoride in water. The agency specified that with fluoride levels greater than 2.0 mg/L children are likely to develop dental fluorosis, that with fluoride levels greater than 4.0 mg/L individuals are at risk of developing crippling skeletal fluorosis, and that it is against federal law to fluoridate water above 4.0 mg/L. Shortly thereafter, the EPA's union of professional employees who are responsible for setting standards attempted to file suit in federal court to overturn the new standard, charging that the EPA had ignored scientific evidence that revealed adverse health effects.

Fluoride is an acute toxin with a rating slightly higher than that of lead. This fact was presented in the fifth edition of Clinical Toxicology of Commercial Products, published in 1984, in which lead was given a toxicity rating of 3 to 4, while fluoride was rated at 4 (3 = moderately toxic, 4 = very toxic). In 1992, the new EPA maximum contaminant level (MCL) for lead was set at 0.015 ppm, with an ultimate goal of 0.0 ppm. The MCL for fluoride is currently set at 4.0 ppm—an MCL that is over 250 times greater than the permissible level for lead.

A 1998 survey showed that 30% of Americans were opposed to community water fluoridation. Opponents base their arguments on six major problems with fluoridation: uncontrolled random dosages, no margin for safety, excessive intake, carcinogenicity (cancer-producing), ineffective reduction of tooth decay, and dental and skeletal fluorosis.

Six Major Problems with Fluoridation of Drinking Water

One: Fluoridation Leads to Uncontrolled Random Dosages.

Because individuals are unique in their sensitivity to medication and in their body size and weight, consistently adding a substance such as fluoride to drinking water can lead to adverse health effects due to uncontrolled random dosages. Such compulsory mass fluoridation is poor medical practice because it does not allow tailoring of dosages to individuals' unique needs, and it does not consider the varying levels of water consumed. Factors that have a bearing on individuals' level of water consumption include general health, lifestyle, age, dietary habits, and climate. Athletes and physical laborers who drink large quantities of water are dosed with more fluoride than the sedentary elderly who drink considerably less water. Patients with diabetes insipidus, a rare disorder of the pituitary gland that causes the release of large amounts of urine, consume enormous amounts of water due to an excessive thirst precipitated by the disease. Infants fed with formula prepared with fluoridated water receive proportionately higher doses of fluoride than adults because of the smaller body weight of the former group and because of its total dependence on fluid nourishment. Individuals who live in warmer climates tend to consume more water than individuals who live in cooler climates.

Two: There Is No Margin for Safety for Fluoride Exposure.

Even supporters of fluoridation do not dispute the relatively narrow gap between the therapeutic dose—the level at which fluoride is supposed to benefit teeth—and the toxic dose—the level at which fluoride begins to do harm. Today, the optimum level set by the government and endorsed by dental authorities is 1.0 mg/L; the maximum contaminant level (MCL) as prescribed by the United States EPA is 4.0 mg/L. In a number of countries, severe skeletal fluorosis has been associated with a fluoride level of 0.7 mg/L—a level that is below both the recommended optimum and MCL levels. Several studies have noted a relationship between consumption of water with a 1.6 mg/L level of fluoride and inhibition of bone healing and with osteoporosis and osteosclerosis (abnormal and weak bone foundation). In 1992, a study in the Journal of the American Medical Association ( JAMA ) found that even low levels of fluoride may increase the risk of hip fracture in the elderly.

A margin of safety of zero—when toxicity due to fluoride occurs at or below claimed therapeutic levels of fluoride—is difficult to justify when the accepted margin of safety in medicine between therapeutic and toxic doses is often a factor of 100 or more.

Three: Total Fluoride Intake Is Excessive.

Besides fluoridated water and fluoride-enhanced dental products, intake of fluoride includes environmental sources such as petroleum refining, vehicle emissions, and household exposures, such as the use of Teflon or Tefal pans and fluorine-based products (e.g., Scotchguard products and insecticides). Also, some foods, such as grapes (due to production with fluoridated water or to pesticide application) and some fish contain fluoride. Grape juice has been found to contain 6.8 mg/L of fluoride, wine, 3.0 mg/L, and canned soup, 6.0 mg/L. Soy infant formula and tea also have been found to surpass the optimal dose of 1.0 mg/L. In 1997, the Academy of General Dentistry (AGD), representing 35 thousand dentists, admonished parents to limit their children's intake of juices because of the juices' high fluoride content. In 1991, the Physicians' Desk Reference, Forty-Fifth Edition warned of toxic reactions to prescription supplements with fluoride for infants and children.

In 1991, the U.S. Public Health Service reported that the range in total daily fluoride intake exceeded 6.5 mg/day. Recently, EPA data revealed that some individuals drink as much as 5.5 liters of 4.0 mg/L fluoridated water per day, which computes to a daily dose of fluoride of 22 mg/day. Such a dosage exceeds the crippling dosage of 10 to 20 mg/day published in 1993 by the National Research Council's Board on Environmental Studies and Toxicology in Health Effects of Ingested Fluoride . The 10 to 20 mg/day dosage was associated with crippling fluorosis when ingested over a period of 10 years.

Fluoride amounts as minimal as 0.04 mg/day have been shown to cause adverse health effects.

It is important to point out that the effects of fluoride depend not only on the total intake—ingestion (food, water, beverages), inhalation, absorption (via the skin)—but also on the duration of exposure (since the effects of fluoride are cumulative) and other factors, such as nutritional status and general health. Poorly nourished individuals and those suffering from kidney malfunction and diabetes tend to become affected after shorter exposures. Recently, a number of studies have suggested that the kidneys of adult males excrete more fluoride than the kidneys of adult females.

When fluoride intake and/or exposure periods become excessive, adverse health effects, such as dental and skeletal fluorosis, bone disorders and fractures, infertility, and cancer, tend to occur. With less excessive intake or exposure, individuals may experience eczema (a disease of the skin); dermatitis (another disease, or abnormality, of the skin); epigastric (or abdominal) distress; headaches; excessive thirst; chronic fatigue; muscular weakness; mouth ulcers; lower urinary tract infections; and the flare-up of old allergies—symptoms that tend to disappear relatively quickly when fluoride intake and exposure are decreased or eliminated.

Four: Fluoride Is a Carcinogen (a Cancer-Causing Substance).

Findings from the 1970s studies of Dr. Dean Burk, former head of the U.S. National Cancer Institute's cell chemistry section, and Dr. John Yiamouyiannis, biochemist and president of the Safe Water Foundation (SWF), suggested that water fluoridation is linked to about 10 thousand cancer deaths yearly. As a result of these findings, the United States Congress ordered studies to determine whether fluoride could be carcinogenic. The studies, which were conducted by the National Toxicology Program (NTP) under the auspices of the U.S. Public Health Service (PHS), confirmed what the Burk-Yiamouyiannis studies had suggested 13 years earlier—that fluoride is carcinogenic. The results of these studies were not made public for some time.

Studies at St. Louis University, the Nippon Dental College (Japan), and the University of Texas have consistently shown that fluoride has the ability to induce tumors and cancers and to stimulate tumor growth rate. In 1991, the SWF obtained studies in which Proctor and Gamble had examined the relationship between carcinogenicity and sodium fluoride. A close look at Proctor and Gamble's studies revealed that dose-dependent increases in carcinogenicity had been observed in every parameter tested. The results of these studies were not submitted to the PHS for four years. Further studies by the SWF found a five-percent increase in all types of cancers in fluoridated communities, while studies by the New Jersey Department of Health confirmed a 6.9-fold increase in bone cancer in young males.

Five: Fluoride Does Not Reduce Tooth Decay.

More and more research is showing that fluoridation is not effective in reducing tooth decay, but rather that fluoridation is associated with increased tooth decay. The most comprehensive United States review was carried out in 1994 by the National Institute of Dental Research on 39 thousand school children, ages five through 17. While the review showed no significant differences in terms of decayed, missing, and filled teeth, it showed that cities with high rates of tooth decay had 9.34% more decay in the children who drank fluoridated water. The review also showed that nine fluoridated cities with high rates of decay had 10% more decay than nine equivalent non-fluoridated cites. Observations also revealed a 5.4% increase in students with tooth decay when 1.0 mg/L fluoride was added to the water supply.

Other United States studies showing that increases in fluoride are accompanied by increases in tooth decay rates include one 1994 study of four hundred thousand students whose rate of tooth decay increased 27% with a 1.0-mg/L-fluoride increase in drinking water, and a second 1994 study of 29 thousand students whose rate of tooth decay increased 43% with a 1.0-mg/L-fluoride increase in drinking water. In a 1972 study in Japan, fluoridation was associated with decay increases of 7% in 22 thousand students. As has been the case for some time, the real route to reducing tooth decay remains to be regular dental hygiene and a nutritious diet.

Six: Excessive Intake of Fluoride Causes Dental and Skeletal Fluorosis.

Fluorosis, which in simple terms means fluoride poisoning, is the first visible sign that the body is being poisoned by excessive fluoride. Dental fluorosis is caused by the ingestion of toxic amounts of fluoride during the period of calcification of the teeth in infancy and early childhood (from birth to age six). Most often, permanent teeth are affected, while baby teeth usually are not. Mild dental fluorosis is characterized by erosion of the tooth enamel that leaves the teeth mottled and discolored with brown and opaque white spots that are insensitive to whitening treatments that use bleach. Severe dental fluorosis is characterized by more significant enamel erosion, tooth pain, and impairment of chewing ability. According to the CDC, at least 22% of all American children have dental fluorosis as a result of ingesting too much fluoride. That rate sometimes rises to as high as 69% in children from high socioeconomic-status families. Similar to the CDC statistic of 22%, the U.S. Public Health Service estimates that one in five children has dental fluorosis. That dental fluorosis is rarely seen in California has been related to the fact that California is the least fluoridated state, with less than 16% of the population drinking fluoridated water.

Skeletal fluorosis is caused by long-term exposure to fluoride at levels that are much higher than those to which average individuals are exposed. Skeletal fluorosis, most often found in the spine, pelvis, and forearm, is a progressive but not life-threatening condition in which the bones decrease in density and gradually become brittle. Because fluoride's effects are cumulative, the changes that take place during skeletal fluorosis range from pain and stiffness of the joints in the early stages to reduced mobility, skeletal deformities, and increased risk of bone fractures in the later stages. As noted earlier, fluoride's effects depend not only on total dosage and duration exposure, but also on other factors such as nutritional status and kidney function. In 1993, the National Research Council's Board on Environmental Studies and Toxicology issued a statement specifying the amount of fluoride and the duration of exposure that would be conducive to skeletal fluorosis to be 10 to 20 mg/day for 10 to 20 years. Applying these figures to a lifetime of 55 to 96 years reveals that just 1.0 mg/day (the amount of fluoride in one liter of water) for each 55 pounds of body weight could conceivably be a crippling dosage.

Conclusion: Fluoride Is Damaging

It is not debatable that some dosages of fluoride used to fluoridate water can cause significant harm to humans. The real question is whether the fluoride concentrations added to the drinking water consumed by the majority of Americans contribute to that significant harm. The answer is undoubtedly "yes" because factors such as variation in the amount of fluoridated water consumed; the amount of fluoride ingested, inhaled, and absorbed from other sources; duration of exposure period; and individual differences make it a statistical certainty that some of the millions of individuals consuming fluori-dated water will be harmed.

—ELAINE H. WACHOLTZ

Viewpoint: No, the addition of small amounts of fluoride to drinking water does not cause significant harm to humans and provides several benefits.

The addition of fluoride to drinking water is a highly beneficial process with no known harmful effects, as shown by numerous studies and years of public and scientific scrutiny. Opposition to fluoridation, which has existed since it was first introduced, is generally based on mistaken assumptions, incomplete data, and unwar-ranted fears. Those who oppose fluoridation on health grounds have little, if any, evidence and are often pursuing other agendas. Hundreds of trials and statistical surveys have shown time and again that the benefits of fluoridation to individuals and society are real, and that there are no health risks to the general population.

Fluoridation and Its History

Fluoridation is the process of adding small amounts of fluoride to public drinking water. The additive is usually in the form of either sodium fluoride (NaF) or hydrofluorosilic acid (H 2 F 6 Si), a direct byproduct of phosphate fertilizer production. Sodium fluoride is used largely as a basis for research on the risks of fluoridation, while hydrofluorosilic acid is used in the majority of municipal fluoridation procedures. Fluoridation occurs naturally in some areas; indeed, it was from observations of a community drinking naturally fluoridated water that the benefits of fluoride in dental health were first discovered.

The promotion of fluoride to prevent tooth decay began in Europe in the 1800s, but it was observations in the United States that led to the widespread acceptance and understanding of the utility of fluoridation. In the early 1900s a dentist, Frederick Sumter McKay, noticed a strange staining of teeth in many of his Colorado Springs patients. Eventually the cause was traced to the high levels of fluoride in the local water, but McKay was surprised to find that his patients' mottled teeth were very resistant to decay. Tests and trials were done to determine a level of fluoridation that would provide protection against tooth decay while avoiding the undesirable mottling effect. A level of 1 ppm was found to be ideal, and early trials showed a dramatic, and extremely rapid, reduction in dental decay in the trial areas. Fluoride is also used in toothpaste and in mouth rinses, and is often taken as a pill. Some foods are also a significant source of fluoride. Fluoride is added to public drinking water all over the world, and is supported and promoted by the vast majority of international and governmental health bodies, including the World Health Organization.

Opponents Cite Health Risks

However, opposition to fluoridation has occurred almost everywhere it has been introduced. Possible health risks are often cited as reasons to oppose fluoridation, but other more emotive issues are often involved as well. Public concern over the process of adding fluoride to drinking water has led to hundreds of trials and studies being carried out by government and independent groups in dozens of countries. In all of the laboratory and fieldwork carried out, however, no evidence linking the recommended levels of fluoridation to health risks has been shown.

Public concern with fluoridation has often focused on the toxic nature of the additives used. Indeed, large doses of sodium fluoride, the most commonly used additive for fluoridation, are fatal. However, fatal levels require consuming several grams in a short period of time, whereas the levels used in fluoridation are usually only 1 ppm or less. In order to ingest fatal levels of sodium fluoride in drinking water one would have to drink so much water he would actually drown long before the levels of sodium fluoride became a problem.

The most common medical charge made by opponents of fluoridation is that it can lead to skeletal fluorosis, causing problems in bone development and strength. It is well known that high levels of fluoride ingestion can cause skeletal problems. For example in India, where much of the drinking water is naturally fluoridated to high levels (often more than 10 ppm), the incidence of skeletal fluorosis is very high. However, the minimum levels of fluoride associated with skeletal fluorosis are an order of magnitude 10 times greater than the levels used in fluoridation. Studies have shown that there is no statistical increase in the incidence of skeletal fluorosis in populations consuming water fluoridated at 1 ppm compared with those drinking non-fluoridated water. It has also been shown that there has been no rise overall in the incidence of skeletal fluorosis in countries that have introduced fluoridation. Indeed, in the Western world, the causes of skeletal fluorosis are generally recognized as excessive thirst and kidney failure.

Another medical concern raised by opponents of fluoridation is the occasional discol-oration or mottling of teeth. Opponents argue that mottling of teeth is proof that fluoridation can cause bone problems. While no one denies that mottling of teeth occurs, and is a direct effect of fluoride, it is at worst a cosmetic problem and not a sign of bone damage. Again, a number of studies have shown no link between mottling of teeth and bone disorders or weakness, or any link between fluoridation and bone development or the incidence of bone fractures.

Some critics have claimed that fluoride can cause allergic or intolerance reactions. However, there is no conclusive evidence of such reactions to the levels associated with public water treatment. The major work on this topic was done by George L. Waldbott and is often used by critics of fluoridation. However, Waldbott did not consistently use double blind trials (experiments in which neither the tester nor the subjects are made aware of the factors involved—to ensure objectivity), and refused to make his unpublished data public, casting doubt on his overall findings. Major studies done since have not corroborated Waldbott's work, including trials done by allergy research organizations such as the American Academy of Allergy. Intolerance and allergenic reactions to fluoride have been noted in higher concentrations, but there is no evidence of such reaction from fluoridated water of 1 ppm.

Some of the most radical and potential worrying health claims made by anti-fluoridationists are those concerning genetic mutations and cancer. Work done with mice in the 1950s suggested that fluoridated water might speed up the development of cancer in those predisposed to it, and some opponents of fluoridation attempted to link fluoride with Down's syndrome. In the 1970s more claims were made concerning cancer and fluoride, with a statistical study seemingly showing a link between them. However, the statistical analysis of the 1970s has been severely criticized on mathematical grounds. Since then, many other studies have failed to find any link between cancer rates and fluoridation. While some more recent studies with mice and fluoride have shown higher rates of cancer, these were with very high levels of fluoride, well above the levels associated with public drinking water. To date, no evidence has been found for an association between public water fluoridation and cancer incidence or mortality in humans, including bone and joint cancers or thyroid cancers. Many comparative studies also have been done between populations drinking fluoridated water and others with unfluoridated water. The only statistically significant difference in health (or growth and development) that has been found is a reduction in the number of tooth cavities (caries).

Despite the overwhelming medical and statistical evidence for the safety of fluoridation, some doubt remains in the cases of isolated individuals who may have developed health problems due to fluoride. No medical treatment can be considered safe for all patients, and statistical analysis does not account for extremely small numbers of potential sufferers. So it is possible that a handful of people worldwide have suffered adverse effects from fluoridation. However, such cases have generally been minor in nature, and the presence of other factors cannot be ruled out. Scientific and medical standards are concerned with large populations, not every single individual, and so from a scientific and medical standpoint fluoridation has been shown time and time again to be not only completely safe, but positively beneficial to public health.

Opposition to fluoride is also justified on grounds other than potential health risks. Some critics have claimed that fluoridation is not an effective treatment. Philip R. N. Sutton, for example, attempted to show that the early trials of fluoridation were flawed, and that fluoridation did not necessarily reduce dental decay. However, while some of Sutton's claims regarding the trials done in the 1940s were substantiated, his work in no way proved that the addition of fluoride to drinking water was ineffective. Before and after Sutton's work, experiments have shown the mechanism by which fluoride strengthens teeth, and comparative studies have shown that tooth decay is reduced in fluoridated areas.

Social and Political Opposition to Fluoride

Political and ethical issues are also invoked as reasons for opposing fluoridation. Many politicians and political groups have used the fluoridation debate for their own ends. In the 1950s there were attempts to link fluoridation with communism. Pamphlets with headlines such as "Fluoridation is Communist Warfare," "Communism via the Water Tap" and "Fluoridation is MASS MURDER " appeared in many Western countries. The link was claimed so often that the Stanley Kubrick film Dr. Strangelove could parody the issue, with the insane Colonel Jack Ripper lecturing his second-in-command on the communist evils of fluoridation. Even today fluoridation is a popular political target for those hoping to capitalize on people's fears of an issue they do not fully understand. Invoking the possibility of cancer and genetic mutations is a very effective method of influencing the voting public, and no matter what the scientific evidence may be such fears are often lingering and all pervasive.

The major ethical issue that is raised by fluoridation is that of individual freedom and rights. This debate is particularly prevalent in the United States. Indeed, fluoridation is the only public health measure to be decided by public vote in the United States. Many health measures are compulsory in many countries, such as the isolation of individuals with highly contagious diseases, or immunization measures. There are even individuals who may experience negative outcomes from such measures, but such measures are justified on the grounds of the greater public good. The compulsory wearing of seat-belts, for example, causes a number of injuries every year; however, many more serious injuries are avoided, and many lives are saved, by wearing seat belts, and the small incidence of negative outcomes is far outweighed by the overwhelming positive effects. Indeed, there are no statistically significant negative impacts of fluoridation, unlike immunization or seat belts, yet it is opposed with more passion and vocal strength than many other compulsory health measures. The issue of fluoridation often suffers in the public arena, as the positive benefits it provides are not so obvious, or as graphic, as with other compulsory health and safety measures.

Another common criticism of fluoridation is that it is an unnatural additive to something that should be pure. However, water is treated in many other ways, such as chlorinating to kill harmful bacteria. Both processes are designed to help the end user. Also, some drinking water is naturally fluoridated; indeed, that was how the effect was first noticed. Some natural water is overly fluoridated, and must have the levels reduced to avoid widespread mottling of teeth, or more significant problems.

Fluoride Reduces Tooth Decay

While tooth decay is not life threatening, it is economically costly. Many recent studies have shown that fluoridation is still a cheap and effective method of lowering the incidence of tooth cavities. Therefore, the result of not fluoridating public drinking water is an increase in costs to the state and the individual. While there may be some strictly philosophical violation of individual rights, there are wider benefits to be gained for society as a whole, and for individuals within a society. People should have the right to good teeth because of fluoridation, and other approaches do not provide this as widely and as cost effectively.

One potentially valid criticism of fluoridation that has arisen in recent years is that the overall dental health in many western countries has been increasing to the point where fluoridation may no longer be necessary. General dental hygiene practices are more widely practiced, and fluoride is available from many other sources, such as toothpaste. However, cost-benefit analyses done since 1974 in a dozen countries have shown that there is still a significant difference in dental cavities between populations drinking fluoridated water and those not doing so. Also a number of recent studies have shown that the incidence of dental cavities increases in areas where fluoridation has been discontinued.

Fluoridation was recently named "One of the Ten Greatest Public Health Achievements in the Twentieth Century" by the U.S. Centers for Disease Control and Prevention. Its utility and cost-effectiveness, as well as its ability to offer dental protection across social and economic divides, has gained it support from dental associations across the world, by many governments, and from many international health bodies such as the World Health Organization. While potential health risks in any treatment should always be considered seriously, decades of research, and hundreds of studies and population analyses have shown no link between health problems and fluoridation. Indeed the only statistical difference noted between populations drinking fluoridated water and those not doing so is a reduction in dental decay. Fluoridation is not only a safe process, it is a cost-effective and beneficial method of improving dental health.

—DAVID TULLOCH

KEY TERMS

FLUORIDATION:

The process of adding fluoride to the water supply of a community to preserve the teeth of its inhabitants. Two fluoridating agents are sodium fluoride (NaF), a colorless crystalline salt, and hydrofluorosilic acid (H 2 F 6 Si), a direct byproduct of phosphate fertilizer production. Sodium fluoride is used largely as a basis for research on the risks of fluoridation, while hydrofluorosilic acid is used in the majority of municipal fluoridation procedures.

FLUOROSIS:

In simple terms, fluorosis means fluoride poisoning. Fluorosis is the first visible sign that the body is being poisoned by excessive fluoride. Dental fluorosis is caused by drinking water with a high fluoride content during the time of tooth formation (from birth to six years of age). Dental fluorosis is characterized by defective calcification that gives a white chalky appearance to the enamel, which gradually undergoes brown discol-oration. Skeletal fluorosis, like dental fluorosis, is caused by drinking water with a high fluoride content. It is the action of the fluoride on the bone that causes the bone to decrease in density and to become brittle. Because fluoride's effects are cumulative, the changes that take place during skeletal fluorosis range from pain and stiffness of joints in the early stages to reduced mobility, skeletal deformities, and increased risk of bone fracture in the later stages.

MARGIN OF SAFETY:

In industry, science, and medicine, the margin of safety is the range of dosage between the therapeutic and toxic levels of a substance. The accepted margin of safety in medicine between therapeutic and toxic doses is often a factor of 100 or more.

MAXIMUM CONTAMINANT LEVEL (MCL):

MCL is the highest level of a contaminate that is allowed in drinking water. MCLs are set as close to the maximum contaminant level goal (MCLG) as feasible using the best available treatment technology. The MCLG is the level of a contaminate in drinking water below which there is no known or expected risk to health. MCLGs allow for a margin of safety.

PARTS PER MILLION (PPM) OR MILLIGRAMS PER LITER (MG/L):

With regard to fluoridation, parts per million (ppm) means one part fluoride per million parts water—a ratio that corresponds to one minute in two years or a single penny in ten thousand dollars. One ppm equals one mg/L, or one milligram per liter.

THERAPEUTIC LEVEL:

Therapeutic level is the level at which a substance is supposed to provide benefit. With regard to fluoridation, the therapeutic level is the level at which fluoride is supposed to benefit teeth by minimizing tooth decay.

TOXIC LEVEL:

The level at which a substance begins to do harm to an organism. With regard to fluoridation, the toxic level is the level at which fluoride causes dental and skeletal fluorosis and is associated with other maladies, such as cancer and hip fractures.

POWER LINES, CANCER, AND THE MEDIA

The media scare that power lines cause cancer illustrates how science can have problems getting across information in the popular press. In 1989 the media widely reported fears that high-voltage power lines are a major source of cancers, in particular childhood leukemia. The media reports were based on research dating back a decade when a study in Denver, Colorado, suggested that children who live close to power lines have a greater chance of contracting leukemia from the high magnetic fields.

Serious concerns were raised regarding the methods used in the study, however, because it did not follow standard scientific methods, such as double-blind trials. But in 1988 another study in Denver, which did use double-blind studies, seemed to support the earlier findings.

What puzzled many scientists, however, was how power lines could possibly cause cancer. Cancer-inducing agents all damage DNA, such as the chemical carcinogens in tobacco smoke or ionizing radiation in x rays. The magnetic field from a power line is related to the amount of current flowing through it. High-voltage lines, which became the main target of media and public campaigns, use very little current. Every day our bodies are subjected to a much more powerful magnetic field than any power line emits: that of the earth itself.

In 1996 the American National Academy of Sciences released the results of a three-year review looking into the possible health risks from exposure to residential electromagnetic fields. They found none. The report found no evidence that power lines are a health risk. Seventeen years' worth of studies had been evaluated, over 500 individual studies, and none showed any link between power lines and health risks. In 1997 the American National Cancer Institute completed a large epidemiological study, and it also found no link between leukemia and power lines. In 1999 a Canadian epidemiological study was released, confirming the work of the 1997 report. These large studies, and many smaller ones, have all come to the same conclusions. From a scientific viewpoint, power lines do not cause cancer. There is no known health risk from high-voltage lines, except for climbing up and touching them.

Yet the popular belief still exists that there is a link between power lines and cancer. The media were quick to report the initial possibility of the health risks, and many special programs and feature articles were written about the issue. Yet the scientific reports denying the link were not given much attention at all. It is the nature of the media to focus on sensational and interesting events. Scientific reports denying the power lines-cancer link are not riveting news, whereas the original scare was just that.

—David Tulloch

Science in Dispute