The ongoing debate on fluoridation –the practice of adding fluoride to our tap water to prevent tooth decay– re-ignited as the City of Portland, Oregon,  voted on this measure (the proposal failed by outstanding majority).

While most of us take it for granted and it is recognized by the Centers for Disease Control and Prevention (CDC) as one of the 10 great public health achievements of the 20th century, fluoridation faces mounting opposition over concerns about negative health effects.

The origins of fluoridation

The effects of fluoride on our teeth were first discovered by chance during the early 20th century in different states of the U.S., where this component is naturally high in drinking water. Specifically, dentists noticed the effect of excessive intake of fluoride on teeth, what today is referred to as fluorosis: from white spots in mild cases to brown stains and a corroded aspect when this condition is severe. Also an inverse relation was found with tooth decay: those affected by fluorosis had lower rates of dental caries.

The hypothesis that tooth decay could be prevented manipulating fluoride levels in drinking water was tested in 1945 by the National Institutes of Health and led, after years of study, to the recommendation of an optimum range of concentration of 0.7-1.2 ppm. Cities throughout the United States quickly adopted this public health measure and the prevalence of dental caries began a rapid decline. Fluoride was also added to tooth paste, mouth rinse and other dental products.

Dental benefits of fluoridation disputed

According to CDC statistics, almost 74 percent of Americans were served by fluoridated water systems in 2010. However, statistics in communities without fluoridation have shown a similar drop in tooth decay, as a result of improved dental care, prompting the question of this measures’ effectiveness.

“Fluoridating water appears neither necessary nor effective,” states Harvard Medical School professor Dan Merfeld, who took a personal stance when this issue was voted in Lincoln, Massachusetts, where he resides. Fluoride benefits, explains this Harvard professor, arise from topical application, that is, by using toothpaste that contains fluoride, not by ingesting it.

“Fluoridating water does not appear to be safe,” continues Professor Merfeld, with a reminder that water with added fluoride should be avoided by kidney patients and in the preparation of infant formula. Fluoride is not an essential nutrient, but a drug regulated by the FDA, he explains, concluding his arguments against this form of mass medication: “Fluoridating water provides uncontrolled drug delivery.”

Young children and the elderly are disproportionately affected by its adverse effects, warns Dr. Mercola, firm opponent of fluoridation, who believes this public health measure is based on politics and not on science. Incidentally, most developed countries, including the majority of Western Europe do not add fluoride to drinking water.

Adverse health effects of fluoridation

Children seem to be at a higher risk of fluoride overdose, with growing evidence of a possible link to reduced IQ, finds a recent study by Professor Merfeld’s colleagues at Harvard School of Public Health (HSPH).

Researchers from HSPH and China Medical University of Shenyang reviewed 27 studies conducted in China –where fluoride is a naturally occurring substance in groundwater— that include over 8,000 children. All but one suggested high levels of fluoride can negatively impact cognitive development.

“Fluoride seems to fit in with lead, mercury and other poisons that cause chemical brain drain,” lead author Philippe Grandjean told HSPH News.

The potential harm to our health associated to fluoride ingestion does not stop here, the Fluoride Action Network reminds us.

Other health effects of fluoridation include:

• Arthritis: Joint pain and stiffness are well-known symptoms of fluoride overdose.
• Bone fractures: Tested to treat osteoporosis, it was found to increase the rate of bone fractures, instead of having the opposite desired effect.
• Cancer: Studies suggest a link between fluoride and osteosarcoma, a rare form of bone cancer, while some researchers point to this substance as a cause of bladder and lung cancer.
• Cardiovascular disease: Research has found that patients who suffered from heart failure had considerably elevated levels of fluoride in blood.
• Diabetes: Fluoride has been shown to impair glucose metabolism.
• Thyroid disease: There is no question fluoride can impact thyroid function, since it has been used in low doses to treat hyperthyroidism.
• Skeletal fluorosis: Caused by prolonged, excessive intake of fluoride, it is easily mistaken with other bone diseases.
• Male infertility: US studies show exposure to fluoride may harm the male reproductive system.

Current fluoridation standards

The Environmental Protection Agency (EPA) is required by law to review –and revise if necessary– drinking water regulations in what is called the Six-Year Review.

Fluoride benefits, explain experts, arise from topical application, not by ingesting it. (Shutterstock)

Based on recommendations by the National Research Council (NRC) after the second Six-Year Review, the EPA revised the maximum level of fluoride in water, in 2011, down to 0.7 milligrams per liter, from the previous range of 1.2-0.7.

According to the agency, this measure would ensure that “people benefit from tooth decay prevention while at the same time avoiding the unwanted health effects from too much fluoride.”

Under the title “Fluoride in Drinking Water: A Scientific Review of EPA’s Standards”, the NRC conducted a comprehensive review of current studies focusing on the potential health effects of fluoride ingestion. More research is needed to determine possible reproductive and developmental effects, neurotoxicity, carcinogenicity, as well as effects on the endocrine, gastrointestinal, renal, hepatic and immune systems, concludes this report, while not dismissing the available studies.

According to CDC statistics, almost 74 percent of Americans were served by fluoridated water systems in 2010. This same source reveals dental fluorosis, caused by long term ingestion of fluoride during teeth formation –up to 8 years of age– has the highest prevalence in teenagers aged 12 to 15, with 41 percent, and is on the rise in this age group.

My Water’s Fluoride, on the CDC’s webpage, allows consumers who are interested to learn about fluoridation in their water system.

Print PDF