Nutrition Column – Weighing the Benefits and Risks of Water Fluoridation

Fluoridation of community water supplies is one of the most widespread preventative health measures in the United States and other economically developed countries today. Although community fluoridation is not without controversy, nearly two-thirds of the U.S. population is currently served by drinking water that contains either natural or added fluoride.

Fluoride, a mineral, helps harden developing tooth enamel, which in turn protects teeth from decay. Dental scientists discovered fluoride’s benefits for teeth in the 1930s when very low tooth decay rates were observed among people whose water supply contained significant amounts of natural fluoride. Subsequent studies in the 1940s and 1950s led to the conclusion that the addition of fluoride to community water supplies resulted in decreased decay rates among residents. This process, known as water fluoridation, adjusts the level of fluoride in a community’s water supply to the level necessary to prevent dental decay – approximately one part fluoride per million parts water.

Multiple professional health organizations, including the American Dental Association, the American Academy of Pediatrics, the American Dietetic Association and the World Health Organization, recognize water fluoridation as the most effective dental public health measure in existence. The general consensus among these organizations is that water fluoridation is a cost-effective approach (approximately 50 cents per person per year) for providing protection from tooth decay that reaches all population segments, regardless of age or socioeconomic status. These organizations cite countless studies that have demonstrated a reduction in tooth decay among people who consume water fluoridated to the recommended levels.

However, it is also true that tooth decay has been declining in recent years in areas and countries were water has not routinely been fluoridated. This decline has been due in part to improved diets (more fruits and vegetables and calcium-rich foods) and to the use of fluoridated toothpaste, dental sealants and better oral hygiene practices. For example, a 1998 study in the Journal of Public Health Dentistry on dental caries, or tooth decay, in Wisconsin reported that the incidence of caries was only 30 percent lower among people in towns with fluoridated water versus those in non-fluoridated towns. This is compared to five-fold differences that were often being seen back in the 1960s.

Today, the incidence of dental caries, like many other diseases, is directly related to low socioeconomic status. Those children without good diets and without good dental health care are the ones most likely to suffer dental caries. So, while the caries experienced in some communities has diminished to the point where some water boards are beginning to question the need for fluoridation, most professionals in the public health field argue that water fluoridation is still the most effective and practical method for minimizing the incidence of dental caries in children from low-income families and thereby minimizing the associated burden of health care on society.

The benefits of fluoride do need to be weighed against the potential for any adverse health effects. Young children who habitually swallow fluoridated toothpaste and mouthwashes rather than spitting them out may be at risk for dental fluorosis – a condition in which the teeth become mottled or marked with brown spots – even though they are healthy and may be extra resistant to decay. Children only need a pea-sized amount of toothpaste on their toothbrushes and should be encouraged not to swallow toothpaste or mouth rinses. Also, there have been a few cases of skeletal fluorosis, a crippling disease that causes denser bones, joint pain and limited range of motion, reported in the U.S. among people exposed for many years to eight times the fluoride concentration recommended by the Public Health Service.

In addition, at least one epidemiological study has shown a positive correlation between incidence of some cancers and use of fluoridated water. In contrast, other studies have shown that areas with higher concentrations of naturally occurring fluoride have lower incidences of cancer. Overall, studies examining the benefits and risks of drinking water that has been fluoridated to the "optimum level" have not conclusively linked fluoride to increases in bone fractures, increases in cancer risk, kidney disease, gastrointestinal disease, birth defects or infertility.

The city of Fort Collins currently is examining whether to continue fluoridating its community water supply. A technical study group was established last year to address the issue and draft a report summarizing the potential benefits and risks of water fluoridation for review by the Fort Collins Water Board and the Larimer County Board of Health. Information about the technical study group and a copy of its final report can be obtained on the Web at: