Health Effects of Fluoride: The Science

Written by Christy Prais on May 8, 2023. Posted in Current News

In this series, we explore the contentious findings surrounding fluoridation of the U.S. public water supply and answer the question of whether water fluoridation poses a risk and what we should do about it

Research has revealed fluoride has both beneficial and harmful effects in people and animals but many of the more critical findings of potential harm are strongly debated.

One of the more contentious findings linked water fluoridation to cancer, a claim that has been largely discounted, though others haven’t been so easily forgotten.

Fluoride has been shown to decrease the prevalence of dental caries, but fluoride critics argue that water fluoridation might not be the most effective way to protect the public from cavities.

It’s now recognized by dental researchers that fluoride’s primary benefit comes from topical application and that it doesn’t need to be swallowed to prevent tooth decay.

An October 1999 CDC report states that laboratory and epidemiologic research findings had dispelled the earlier belief that ingesting fluoride resulted in stronger teeth. It asserts that fluoride effects “primarily are topical for both adults and children.”

And while applying fluoride to teeth topically has been shown to be beneficial, there is a large growing body of scientific research conducted over decades that links ingesting fluoride with dental and skeletal fluorosis and a range of health effects including damage to the brain, disruption of the endocrine system (thyroid gland, pineal gland, and glucose metabolism), and types of cancers.

The Science

“When consumed in tap water, fluoridation chemicals find their way throughout the entire body. It is not only probable, it is inevitable that we will pay the price through unexplained diseases and increased medical costs,” Clint Griess, author of “Something in the Water,” wrote in an email to The Epoch Times.

The highly criticized research of Dr. Dean Burk (1904–1988), a former chief chemist at the National Cancer Institute, conducted in the 1970s and ’80s linked fluoridation of the public water supply to cancer.

Burk wrote in his last scientific paper, “It is concluded that artificial fluoridation appears to cause or induce about 20-30 excess cancer deaths for every 100,000 persons exposed per year after about 15-20 years,” cited the Berkeley Essig Museum of Entomology Collections.

In a Sept. 21, 1977, congressional hearing, Burk and his colleague John Yiamouyiannis discussed the findings of their studies on the link between water fluoridation and cancer.

One of the studies presented compared cancer death rates of 10 of the largest fluoridated cities to 10 of the largest un-fluoridated cities year by year. The tracking started in the cities before fluoridation began and found that the cancer death rate for both groups of cities prior to fluoridation was for the most part identical.

The study found that cancer death rates showed a drastic increase in fluoridated cities around the time the fluoridation program began, while the cancer death rate increase in the non-fluoridated cities didn’t significantly increase.

In an interview with NCRV, a Netherlands-based broadcasting company, Burk urged the government to bring a prompt end to the artificial fluoridation of public water supplies.

Burk’s work has been sharply criticized, and later studies challenged the link between fluoride and cancer. He was and still is targeted by fluoridation proponents who say he failed to correct for age, sex, race, and cancer site distribution in some of his studies. Despite this, Burk’s work was largely responsible for the termination of fluoridation in the Netherlands, the Berkeley Entomology Collections noted.

Prior to Burk’s work, a similar report in the 1955 New England Journal of Medicine showed a 400 percent increase in thyroid cancer in San Francisco during the period that the city had fluoridated drinking water, reported Gladys Caldwell and Dr. Philip Zanfagna in their 1974 book “Fluoridation and Truth Decay.”

The cancer link remains contentious and the CDC and others hold that other studies have disproven the link. That includes a research review published in 1983 in the Bulletin of the World Health Organization that claimed the assertion was erroneous.

Also, the CDC cites a review by Howard F. Pollick that states, “Studies in which humans received doses significantly higher than the optimum fluoride intake for long periods of time showed no negative impact on thyroid function.”

Unfortunately, there has been conflicting science around fluoride and contentious findings continue to emerge. That has been particularly true when it comes to fluoride’s potential neurological effects.

Fluoride and the Brain

In October 1996, Phyllis Mullenix spoke at a Fluoride Forum at Clark University in Worchester, Massachusetts, on her research and groundbreaking study on fluoride.

Mullenix has a doctorate in pharmacology with a specialty in neurotoxicology and completed a post-doctorate at Johns Hopkins School of Public Health in environmental medicine.

After a career at both the department of psychiatry at Children’s Hospital in Boston and the department of neuropathology at Harvard Medical School, she took a position at the toxicology department at the Forsyth Dental Research Institute, the first toxicology department established in any dental research institution in the world.

In her lecture, Mullenix recounts that Dr. Jack Hein, the director of the institute, was suspicious that many of the dental products were possibly causing neurological issues.

Mullenix was tasked with applying a new computer-based screening technology she developed to look at the environmental impact and the neurotoxicity of products that are used by dentists and the dental community. Fluoride was the first substance she studied.

In 1995, she published her groundbreaking study linking fluoride with damage to the central nervous system in the peer-reviewed journal Neurotoxicology and Teratology.

Her study on the effects of fluoride on rats found three basic conclusions, Mullenix recounted in the 1996 forum.

First, “there was no question that behavior was vulnerable to fluoride,” regardless of a very short exposure when young, prenatal, or early postnatal “all you needed was 2 or 3 days exposure to this [fluoride] and it caused a permanent change in behavior when the animals grew up,” she said.

If you took all the other exposures away except for that one exposure, it was enough to “permanently change the behavior,” Mullenix said.

The second major finding in the study was that the effects varied with age she said. If the rats were exposed prenatally, the behavior change observed was hyperactivity and when rats were exposed as weanlings or adults they displayed what the scientists called “couch potato syndrome,” or hypoactive behavior, similar to chronic fatigue.

The third major finding was that “fluoride accumulated in the brain, and this is very different than what the literature had said before.” The literature up to this point said that it didn’t get into the brain and it doesn’t bioaccumulate, “and we know that this is wrong,” concluded Mullenix.

In her study, the fluoride-exposed females had double or triple the amount of fluoride in the hippocampus regions of the brain compared to the control.

The brain’s hippocampus is part of the limbic system and plays important roles in short- and long-term memory, spatial memory that enables navigation, and emotional behavior.

There has been significant debate around the findings of Mullenix’s study in the scientific community although the 2006 NRC report concluded that “the committee agrees there are difficulties with interpreting the results of the study, but those difficulties do not warrant dismissal of the results.”

The CDC’s Stance

The Epoch Times reached out to the CDC with questions about safety and their support of the current water fluoridation program. The CDC pointed to the National Toxicology Program’s (NTP) “NTP Monograph on the State of the Science Concerning Fluoride Exposure and Neurodevelopmental and Cognitive Health Effects: A Systematic Review.”

The NTP Monograph was performed by an external review board and has been a source of controversy in the ongoing lawsuit against the EPA as internal CDC emails obtained through the Freedom of Information Act by plaintiff attorney Michael Connett showed government agencies interfered with its release.

The report was finally made public on March 15th under an agreement reached in the ongoing lawsuit and a public meeting is set for May 4th where the Board of Scientific Counselors will be presenting its conclusions and recommendations

“We support this process and look forward to seeing their final report, which is likely to help answer a number of your questions,” the CDC responded.

The 2006 NRC Report

The Safe Drinking Water Act requires periodic reassessment of regulations for drinking water contaminants. Because of this, the NRC committee on Fluoride in Drinking Water was previously charged by the Environmental Protection Agency (EPA) with reviewing toxicologic, epidemiologic, and clinical data on fluoride, as well as exposure data on orally ingested fluoride from drinking water and other sources (ie. food and dental-hygiene products).

This review resulted in the 2006 scientific report of the EPA’s standards of fluoride in drinking water by the National Research Council (NRC).

Their task was to independently evaluate the scientific basis of the EPA’s set drinking water standards, which were set at a maximum contaminant level goal (MCLG) of 4 mg/L and a secondary maximum contaminant level (SMCL) of 2 mg/L. The MCLG and the SMCL were set in 1986.

The CDC currently supports a water fluoridation level of 0.7mg/L, the concentration recommended by the Public Health Service.

The enforceable maximum (MCLG) is 4.0 mg/L. This maximum is meant to protect against skeletal fluorosis. The secondary maximum (SMCL) is 2.0 mg/L, which is meant to protect against moderate to severe dental fluorosis. The secondary standard isn’t enforceable but requires systems to notify the public if the average levels exceed it.

The NRC fluoride committee was asked to identify data gaps and to make recommendations for future research meant to better inform the MCLG and SMCL to protect children and others from adverse health effects.

In their research, the NRC committee found gaps in the information on fluoride that prevented the committee from making some judgments about the safety or the risks of fluoride at concentrations of 2 to 4 mg/L.

The committee urged the scientific community to carefully conduct more research on exposure to fluoride especially endocrine effects and brain function and recommended that the EPA should “update the risk assessment of fluoride to include new data on health risks and better estimates of total exposure (relative source contribution) for individuals.”

The committee also urged the EPA to consider susceptible subpopulations, uncertainties, and variability in their assessment.

The NRC review of neurotoxicity and neurobehavioral effects of fluoride stated that based on “information largely derived from histological, chemical, and molecular studies, it is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means.”

They noted that “fluorides also increase the production of free radicals in the brain through several different biological pathways. These changes have a bearing on the possibility that fluorides act to increase the risk of developing Alzheimer’s disease.”

The committee assessed studies that reported IQ deficits in children exposed to fluoride and said that despite the studies lacking sufficient detail, the committee felt that the consistency of the results appeared significant enough to warrant additional research on the effects of fluoride on intelligence.

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