by Paul Connett
Hodge and Mullenix
In the late 1980s, many years after his animal experiment was turned down, Harold Hodge joined the staff of the Forsyth Dental Center and quietly watched Phyllis Mullenix as she found what he may have privately suspected to be the case. Fluoride did indeed alter animal behavior, but Hodge died before this finding was published and ruined Mullenix’s career.
Chris Bryson, in his book The Fluoride Deception, 3 gives the sordid details of the treatment meted out to Mullenix when her 1995 paper4 was accepted for publication. At the time, she was chairperson of the first toxicology department established in a dental school in the United States. Nevertheless, she was told that her work “was no longer relevant to dentistry, ”5 and she was fired. Contrary to previous assertions, 6 her paper showed that fluoride did accumulate in rat brains, and that the animals dosed before birth showed movement patterns associated with hyperactivity (i. e. , were overactive) and the animals exposed after birth showed hypoactive patterns (i. e. , were underactive).
Spittle
In the summer of 1994, a year before Mullenix’s paper was published, Spittle’s article “Psychopharmacology of Fluoride: A Review” appeared. In it, Spittle concluded that “chronic exposure to fluoride may be associated with cerebral impairment affecting particularly concentration and memory. ” While he admitted that the evidence was suggestive rather than conclusive, he listed several possible mechanisms whereby fluoride could affect brain functioning, including “influencing calcium currents, altering enzyme configurations, inhibiting adenyl cyclase activity and increasing phosphoinositide hydrolysis. ”7
When Spittle wrote his article, he was unaware of the Chinese studies (discussed next) but he had read Waldbott and colleagues’ book Fluoridation: The Great Dilemma8 and was aware of their reports of cognitive impairment from those who were hypersensitive to fluoride (see chapter 13).
Chinese Studies
One year after the publication of Spittle’s paper and shortly after Mullenix’s paper appeared, the first articles from China on lowered IQ appeared in the journal Fluoride. 9, 10 There have now been twenty-three studies from four different countries (Iran, India, Mexico, and China) demonstrating a possible association between fluoride exposure and lowered IQ in children; these are listed in appendix 1. Five of the Chinese studies have yet to be translated into English.
After Mullenix
There have now been over eighty animal studies confirming what Mullenix et al. reported in the published paper that got her fired. 11 These studies demonstrate that fluoride does accumulate in animal brains, causing damage in areas of the brain involved with memory and learning, and that fluoride can alter behavior. (All of the animal studies are listed in chronological order in appendix 1, including those that are identified individually below. )
Prior to Mullenix’s work, published in 1995, it was generally assumed that little fluoride entered or accumulated in the brain. 12 However, several researchers have now shown that fluoride can accumulate in the brain, some even specifying the areas of the brain where the fluoride is located. 13–19
In a critique of Mullenix’s work that was sent to an engineer at the CDC’s Oral Health Division but not to Mullenix herself, Dr. Gary Whitford intimates that the fluoride levels in the water she gave to the rats were high and suggested that they were sufficient to cause behavioral problems by indirect means. 20 Mullenix responded to that claim by pointing out that the levels she used were not high because one must use about twelve times more fluoride in water to reach the same plasma levels in rats as one would get with humans. Specifically, to achieve the same range of plasma levels, rats must drink water with 75–125 ppm fluoride, while humans require 5–10 ppm fluoride. 21 In a very recent publication, Sawan et al. stated that a fluoride level of 100 ppm in water fed to rats was necessary to reach the same plasma level as humans drinking water at 8 ppm—this again is a ratio of about 12 to 1. 22
Guan and colleagues have consistently found neurotoxic effects among rats drinking water with 30 ppm fluoride, which according to Mullenix and Sawan would be equivalent to humans drinking water with fluoride at 2. 5 ppm. 23–25 Several papers have shown that fluoride is concentrated in, or has an effect upon, the hippocampus. 26–38 Damage to the hippocampus usually results in difficulties in forming new memories and recalling events that occurred prior to the damage.
Varner et al. 1998
Julie A. Varner’s study was a continuation of the work of Robert Isaacson at the State University of New York at Binghamton. 39 In the Varner study, rats were fed for one year with 1 ppm fluoride in their water (which was doubly distilled and de-ionized), using either sodium fluoride or aluminum fluoride. In the rats treated with either fluoride compound, the authors discovered the following:
• Morphological changes in the kidney and the brain
• An increased uptake of aluminum into the brain
• The formation of beta-amyloid deposits usually associated with Alzheimer’s disease40
These findings prompted both the Environmental Protection Agency (EPA) and the National Institute of Environmental Health Sciences (NIEHS) to recommend the study of aluminum fluoride as a possible neurotoxin.
The National Research Council
In 2006, the National Research Council became the first government-appointed review body to examine the literature on fluoride’s impact on the brain in any depth. In chapter 7 of its report, the panel reviewed both animal and human studies. 41 The NRC panel had this to say about the studies on the brain:
On the basis of 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. . .
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. 42
The NRC panel recommended “additional animal studies designed to evaluate reasoning. ”43
The NRC panel also recommended that studies of populations “exposed to different concentrations of fluoride” be undertaken to “evaluate neurochemical changes that may be associated with dementia, ” adding that “consideration should be given to assessing effects from chronic exposure, effects that might be delayed or occur late-in-life, and individual susceptibility. ”44
In 2006, the NRC panel had access to five of the twenty-three IQ studies that have been published to date and concluded:
A few epidemiologic studies of Chinese populations have reported IQ deficits in children exposed to fluoride at 2. 5 to 4 mg/L in drinking water. Although the studies lacked sufficient detail for the committee to fully assess their quality and relevance to U. S. populations, the consistency of the results appears significant enough to warrant additional research on the effects of fluoride on intelligence. 45
The NRC panel recommended that future research “should include measurements of reasoning ability, problem solving, IQ, and short- and long-term memory. ”46
More on the IQ Studies
Contrary to fluoride proponents’ claims that an association between fluoride and lowered IQ has been demonstrated only at high fluoride levels, one of the IQ studies, which the NRC authors considered to have the “strongest study design, ” indicated that IQ in children could be lowered by exposure to concentrations as low as 1. 9 ppm. 47, 48 In the abstract of the first of two articles on that study, Xiang indicated that, from a regulatory point of view, it was significant that IQ could be affected at any level above 1 ppm. Another Chinese study indicated that even lower levels of fluoride exposure (e. g. , 0. 9 ppm in the water) could exacerbate the neurological effects of iodine deficiency. 49
In a trip to China in 2006, Paul Connett was able to visit the two villages that were the focus of the Xiang study. He noted that from an epidemiological point of view, the villages appeared to present an
ideal model for comparison. In both, the population was highly stable, most families having lived in the same area for many generations. Occupations, housing, diet, and education were the same. Xiang et al. controlled for both lead exposure50 and iodine intake, 51 two factors that could also cause lowered IQ. The obvious difference was the level of fluoride in the well water used by the two villages. The well water in one village contained fluoride at levels between 2. 5 and 4. 5 ppm; the fluoride in the well water of the other village was less than 0. 7 ppm. Across the age range of the children examined, the study showed an IQ difference between the two villages of between five to ten IQ points. There was also a clear shift in the IQ distribution curve, with more children in the mentally handicapped and fewer in the very bright category in the high-fluoride village. Howard Pollick has criticized some of the methodological aspects of the study, in a series of published exchanges of views on fluoridation with Paul Connett. 52–56 However, far more disturbing than any weakness in this study (or the other twenty-two IQ studies) is the fact that no fluoridating country (except for one small study in New Zealand57 ) has attempted to replicate this research.
Other Human Studies of Fluoride’s Impact on the Brain
In addition to the studies that have shown a possible link between fluoride exposure and lowered IQ in children, there have been other studies from China adding to the weight of evidence of fluoride’s ability to damage the human brain.
Three different Chinese research groups have shown that fluoride has damaged the brains of aborted fetuses in areas endemic for fluorosis. 58–60 For example, Du et al. examined the brains of fifteen aborted fetuses at five to eight months gestation from an area with endemic fluorosis and compared them with fetuses from an area where fluorosis was not endemic. Fetal brains from the endemic area revealed a significant reduction in the density of mitochondria (the parts of the cell that produce energy) and a reduction in the mean volume of neurons (brain cells). 61
Other human studies, using a batch of standard psychological tests, have revealed behavioral differences in adults exposed to high industrial levels of fluoride62 and behavioral differences in neonates in endemic fluorosis areas. 63
Pro-Fluoridation Governments
Despite the cumulative evidence emerging in Western scientific literature in the mid-1990s that fluoride could damage the brain, 64–68 there has been practically no research into the issue in fluoridated countries. In 2002, the UK Medical Research Council (MRC) even put a higher priority on more studies of dental fluorosis than on any investigation of fluoride’s potential to affect neurodevelopment. 69
Almost no studies have been undertaken in any fluoridated country to explore a possible relationship between fluoride exposure and lowered IQ. In the United States one small behavioral study found no apparent relationship between childhood behavior and the severity of dental fluorosis. 70 In New Zealand one small study compared eight- and nine-year-old children who had lived up to seven years in a fluoridated community (1 ppm) or a non-fluoridated community (0. 1 ppm). The authors reported no significant difference in IQ between the two communities. 71 These studies seem to represent the sum total of interest in this issue among countries practicing fluoridation.
Other Scientists’ Concern
While fluoridation promoters continue to ignore—or dismiss—the studies of fluoride’s impact on both animal and human brains, some scientists are taking the issue more seriously. In May 2000, Greater Boston Physicians for Social Responsibility published a report titled In Harm’s Way: Toxic Threats to Child Development. 72 The authors included a discussion of fluoride’s potential to damage the brain. After briefly reviewing two animal studies73, 74 and two IQ studies, 75, 76 they concluded:
Studies in animals and human populations suggest that fluoride exposure, at levels that are experienced by a significant proportion of the population whose drinking water is fluoridated, may have adverse impacts on the developing brain. Though no final conclusions may be reached from available data, the findings are provocative and of significant public health concern. Perhaps most surprising is the relative sparseness of data addressing the central question of whether or not this chemical, which is intentionally added to drinking water, may interfere with normal brain development and function. Focused research should address this important matter urgently. 77
In 2006, Philippe Grandjean and Philip Landrigan identified fluoride as a possible neurotoxicant in an article titled “Developmental Neurotoxicity of Industrial Chemicals, ” published in Lancet. In a section titled “Emerging Neurotoxic Substances, ” they wrote, “Three obvious candidate substances deserve particular attention, including two that have not seemed to cause neurotoxicity in adults. ” Fluoride was one of those candidate substances. 78
As discussed in chapter 3, the use of silicofluorides as water fluoridating agents has been associated with a greater uptake of lead into children’s blood. 79, 80 This association received some strong biological support from an animal study by Sawan et al. published in 2010. 81 The authors found that exposure of rats to a combination of fluoride and lead in their drinking water increased the uptake of lead into blood some threefold over exposure to lead alone. There is no argument that lead causes serious mental developmental problems for children; thus, should fluoride increase the uptake of lead into the blood, as these epidemiological and animal studies suggest it may, fluoride could enhance the brain damage caused by lead exposure.
Dismissal of the IQ Studies at Southampton
At the three public meetings organized by the UK’s South Central Strategic Health Authority (SHA) in Southampton in October and November 2008, mentioned earlier, Paul Connett drew attention to the IQ studies from China, India, Iran, and Mexico and provided copies of eighteen of the studies that are available in English to the SHA. This matter, too, was referred to the consultants Bazian Ltd. (see chapter 14).
By criticizing the methods used in some of the studies and claiming that the fluoride concentrations involved were generally higher than those planned for Southampton, Bazian felt able to conclude that “from these studies alone, it is uncertain how far fluoride is responsible for any impairment in intellectual development seen. The amount of naturally occurring fluoride in drinking water and from other sources and the socioeconomic characteristics in the areas studied is different from the UK and so these studies do not have direct application to the local population of Southampton”82 [emphasis added].
These conclusions are highly equivocal and fall far short of giving fluoride a clean bill of health, emphasizing uncertainty and dismissing the studies’ “direct” relevance to Southampton on relatively trivial pretexts. Anyone reading the details of Bazian’s report can see that there is indeed serious cause for concern. Had Bazian done a margin-of-safety analysis (described in chapter 20), as is normal in toxicological evaluations, the high relevance of the IQ data to any fluoridation program would have been even clearer. Which brings us once again to the issue of the crucial difference between dose and concentration. A child drinking 2 liters of water at 1. 0 ppm would get a higher dose of fluoride (dose = 2 mg) than a child drinking 1 liter of water at 1. 9 ppm (dose = 1. 9 mg), a level at which damage was estimated to occur by Xiang et al. 83
However, Southampton SHA either failed to notice Bazian’s implied reservations or chose to disregard them, stating baldly, “Their advice was that the studies are unreliable and do not constitute convincing evidence of harm. ”84 On this basis, the SHA ignored the IQ studies entirely when recommending fluoridation for Southampton.
One wonders how convincing the evidence has to be. Here we have a proposal to mass-medicate 100, 000 or more people. On the one hand, there is a putative modest benefit to the dental health of young children (which could be achieved by other means; see chapters 6–8). On the other hand, there are about twenty studies (albeit with questioned methodologies in some cases) suggesting potential damage to the brains of young children at levels quite close to the concentration of 1 ppm to be
used in Southampton. That medication does not sound like a very good deal; it is hard to believe that many parents would choose it for their own children. The SHA’s attitude is in fact a particularly glaring example of an irresponsible mind-set that seems to be common among fluoridation proponents: that it is okay to fluoridate the public water supply until incontrovertible proof is provided that it does some devastating harm. This attitude is all the more indefensible since fluoridating countries show more interest in belittling what evidence there is than in carrying out any investigations themselves.
Summary
In this chapter we have summarized the animal and human studies that show associations of fluoride with damages to the brain. Animal studies have indicated that fluoride can enter the brain and that the accumulation is dose-dependent. Animal studies have also shown biochemical changes and damage that can be viewed microscopically. Many of these studies have been carried out at relatively high doses, but one remarkable study by Varner et al. showed effects at a low level of exposure—1 ppm in rats’ drinking water over one year of exposure. At this level a greater uptake of aluminum into the brain was observed, as well as beta-amyloid deposits such as have been associated with Alzheimer’s disease. There have also been twenty-three studies indicating a lowered IQ in children associated with levels as low as 1. 9 ppm of fluoride in drinking water. We do not claim that these IQ studies add up to conclusive evidence that water fluoridation impairs cognitive development. However, when you have twenty or more reports consistently suggesting a problem, and these have been backed up by studies indicating possible brain damage in aborted fetuses in areas endemic for fluorosis in China, as well as animal data indicating brain damage and abnormal behavior, and very little to set in the balance against them, it is wise to sit up and pay attention. The health authorities and governments of fluoridating countries show little sign of doing that. We return to this failure to pursue important health studies in chapter 22. Meanwhile, we have to ask whether the saving of any amount of tooth decay, which we believe is slight at best (see chapters 6–8), could possibly justify taking the risk of interfering with the development of a child’s brain.