Prenatal Fluoride and Autism


by John D. MacArthur

It is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means.

National Research Council (2006)
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Increasing evidence reveals that prenatal exposures to some widely used chemicals are implicated in the growing pandemic of developmental neurotoxicity.1,2 Fluoride is the most controversial of these chemicals, because it is the only one intentionally added to the drinking water of more than 200 million men, women, and children in the US.
     
Topical fluoride in toothpaste has been used since the 1950s to reduce tooth decay. A primary mechanism of fluoride’s ability to prevent dental caries is its strong antimicrobial effects. It is well established that fluoride can inhibit the growth of bacteria, says Robert Breaker, PhD, a National Academy of Sciences award-winning molecular biologist. He admits, however, “There has been little understanding of its precise effects on cells.”3

Fluoride Weakens Bacterial Adhesion Forces

In 2013, a key antimicrobial mechanism of fluoride was identified by researchers in experimental physics at Saarland University in Germany. Using artificial tooth surfaces (hydroxyapatite pellets), they tested fluoride’s effect on the adhesion forces of cariogenic bacteria (Streptococcus mutans and Streptococcus oralis) and a nonpathogenic bacterium (Staphylococcus carnosus).

After they were exposed to fluoride, atomic force microscopy revealed that all three bacteria species exhibited lower adhesion forces. Because fluoride makes bacteria less able to stick to teeth, decay-causing microorganisms are more easily washed away by saliva or brushing. The researchers said, “Fluoride appears to weaken bacterial adhesion forces in general.”4,5
     
This raises the question, how do weakened bacterial adhesion forces affect the developing gastrointestinal tract, whose vast and complex ecosystem – collectively called the gut microbiota or microbiome – plays an essential role in neurological and immunological development and health?

Adhesion Forces and Bacterial Colonization of the GI Tract

The process of surface adhesion is a survival strategy employed by virtually all bacteria and refined over millions of years.6 Adhesion of bacteria to intestinal mucosa is often recognized as a prerequisite for microbial colonization of the human gastrointestinal (GI) tract.7 Emerging research shows that this colonization begins in the womb.8,9
     
Distinct microbial populations have recently been discovered at maternal sites that were previously thought to be sterile, including the amniotic cavity and meconium (first feces of a newborn infant). Our understanding of the impact of fetal microbial contact on health outcomes is still rudimentary.10
     
Of the many potential sources for a prenatal microbiome, amniotic fluid flora accounted for greater relative abundance of bacteria found in meconium than either the oral or vaginal cavities of pregnant women.11,12 When pregnant women consumed specific probiotics, microbial DNA in their amniotic fluid was associated with changes in gene expression in the fetal intestine.13

Fluoridated Amniotic Fluid

Amniotic fluid is arguably our most precious bodily fluid. Early in the second trimester, a fetus begins swallowing amniotic fluid, which passes through its digestive system and kidneys, is excreted as urine, then swallowed again – recycling the full volume of amniotic fluid every few hours. By the time the child is born, up to 15 ounces of amniotic fluid are consumed per day.
     
Fetal swallowing contributes importantly to gastrointestinal development as a result of the large volume of ingested fluid. Nutrients, hormones, and growth factors in amniotic fluid bathing the fetal intestine during the third trimester are needed to produce a profound maturational effect on the intestine’s ability to appropriately respond to colonizing bacteria.14

Fluoride concentrations in human amniotic fluid are about 50% of maternal serum levels and are considerably higher at term than earlier in pregnancy.15,16 Women who consumed 1.25 mg of fluoride per day had a significantly higher fluoride concentration in their amniotic fluid than women who consumed 0.25 to 1.0 mg per day.17 Note: the US Institute of Medicine says that the recommended “adequate intake” level of fluoride for pregnant women is 3 mg per day.18

Ron et al. (1986) found that the fluoride concentration in women’s amniotic fluid was 0.017 mg/l, when their drinking water contained <0.5 mg/l of fluoride.16 A similar fluoride concentration is secreted by salivary glands into the ductal saliva of children who drink fluoridated water.19 This very low level of fluoride provides the “systemic” benefit, the primary rationale for swallowing fluoride in water.
     
A low concentration of fluoride – continually swallowed and recycled in amniotic fluid – must also be bioactive in the fetal GI tract. In fact, a primary reason why pregnant women are encouraged to consume fluoridated water is to help “delay colonization of the infant oral cavity by cariogenic bacteria.”20

Gut Bacteria and Autism

Antimicrobials, including low-dose antimicrobials in food and water supplies, indiscriminately affect all members of the gut microbial ecosystem, especially decreasing the levels of beneficial bifidobacteria and increasing the levels of potentially harmful clostridia, as seen in the microbiota of autistic children.21,22
     
Autism is closely associated with a distinct gut microflora that can be characterized by reduced richness and diversity as well as by altered composition and structure of the microbial community; specifically, lower levels of important groups of carbohydrate-degrading or fermenting microbes.22-26
     
In a rodent model for autism spectrum disorder, autism-like behavior is associated with altered microbial colonization and activity.27 These mice have abnormally low levels of Bacteroides fragilis, a bacterium that modulates levels of several metabolites and is one of the earliest-colonizing and most abundant microbes in a healthy human intestinal tract.28 Feeding B. fragilis to these mice ameliorates defects in communicative, repetitive, and anxiety-like behaviors.29

Gut Bacteria, Immune System, Autism, and Fluoride

Increasing evidence indicates that gut microbiota also influences the immune systems and vice versa.30Microbial contact in utero is associated with changes in fetal intestinal innate immune gene expression profile.13

The GI tract has 70% to 80% of the body’s immune cells and is the primary site of interaction between the immune system and microorganisms, both symbiotic and pathogenic.31 Proper microbial colonization and composition of the GI tract are essential for the maturation of the immune system.8,21,32,33 Different bacteria have clearly defined adherence sites and immunological effects.34
     
Immune system dysregulation in autism spectrum disorders has been reported in several studies.35

During colonization of the gut with B. fragilis, the cellular and physical maturation of the developing immune system is directed by a bacterial polysaccharide.28 Ochoa-Repáraz et al. (2010) found that a polysaccharide of B. fragilis can protect against central nervous system demyelinating disease.36 Human and animal studies implicate impairments of myelination in autism spectrum disorder.37,38
     
Sodium fluoride has been shown to reduce bacterial polysaccharide production by inhibiting bacterial attachment.39
     
A mechanism of action for fluoride’s ability to reduce bacterial adhesion forces is its inhibitory effect on the activity of glucan-binding proteins.40 In the GI tract, glucans represent a significant potential in the suppression or treatment of several gastrointestinal problems.41

Adhesion Molecules, Autism, and Fluoride

In its comprehensive 2006 report Fluoride in Drinking Water: A Scientific Review of EPA’s Standards, the US National Research Council concluded, “It is apparent that fluorides have the ability to interfere with the functions of the brain and the body by direct and indirect means.”42
     
Fluoride’s indirect effects on neurodevelopment via the fetal microbiome have yet to be researched. There is, however, growing evidence of fluoride’s direct effects on the fetal brain, which is exposed to the fluoride circulating in maternal blood.43
     
Autism involves early brain overgrowth and dysfunction, an excess of neurons in the prefrontal cortex caused by a prenatal disruption of developing brain architecture as early as the second trimester.44 Research by Lahiri et al. (2013) suggests that brain enlargement in autism is likely due to cell adhesion dysfunction.45

Neural cell adhesion molecules (NCAM) are widely expressed in the nervous system, where they are involved in axon growth and guidance – fundamental processes that underlie formation of the synaptic connections and myelinated nerve structure crucial to brain development.
     
Significantly lower serum levels of several types of adhesion molecules, including NCAM, have been found in persons with autism.46,47 Neural pathways involving synaptic cell adhesion are disrupted in some people with autism, including alterations in the structure and expression of NCAM.48,49
     
Fluoride exposure has been shown to cause a dose-dependent decrease in NCAM expression levels in rat hippocampal neurons. In particular, the NCAM-140 protein expression level was significantly lower in response to the lowest dose of fluoride used.50,51 NCAM-140 is found in migrating growth cones that are crucial to the formation of synaptic connections.52

Fluoride Adversely Affects Synaptic Development

Diseases such as autism and Alzheimer’s are increasingly linked to defects in the organization and number of synapses, the tens of trillions of tiny yet complex structures that link neurons so they can communicate with each other. A molecule that helps create and maintain the scaffolding around which a synapse is built is postsynaptic density protein-95 (PSD-95). Neuronal synapses with less PSD-95 are likely to be weakened or lost.53
     
PSD-95 is a membrane-associated kinase concentrated at glutamatergic synapses. It regulates adhesion and enhances maturation of the presynaptic terminal. Research demonstrates that PSD-95 orchestrates synaptic development and plays an important role in synapse stabilization and plasticity.54
     
In rats that drank water with added fluoride for several months, the fluidity of brain synaptic membranes and the expression level of PSD-95 decreased in a dose-dependent manner.55,56
     
Rats anesthetized for 4 hours with 2.5% sevoflurane, a fluoride-based anesthetic, showed long-term deficits in hippocampal function and decreased hippocampal PSD-95 expression. Seven weeks after exposure, they had significant spatial learning and memory impairment.54
     
In humans, exposure to 2.4% sevoflurane significantly increases serum fluoride levels.57 (Sevoflurane is the most prevalent volatile anesthetic in pediatric anesthesia.)

US Fetuses Overdosed with a ‘Developmental Neurotoxicant’

In 2009, researchers at the EPA’s Neurotoxicology Division found “substantial evidence” that fluoride is “toxic to the developing mammalian nervous system.”58 Pregnant women already minimize or avoid other “developmental neurotoxicants” in the same category with fluoride: ethanol (alcohol), nicotine, diazepam (Valium), caffeine, lead, arsenic, amphetamine. They’re also advised to avoid tetracycline, even though the EPA has only “minimal evidence” of its developmental neurotoxicity.
     
Fluoridation promoters say not to worry because “dose makes the poison, and the recommended level of fluoride in US drinking water is only 0.7 mg/l” (a concentration, not a dose). When it comes to neurodevelopment, however, a toxic substance’s capacity to disrupt the developing brain does not simply depend upon dose. It also depends upon the “duration of exposure, and most important, on the timing during the developmental process,” says the National Scientific Council on the Developing Child.59
     
In 1997, the Institute of Medicine (IOM) established 0.7 mg of fluoride per day as a Tolerable Upper Intake Level (UL) for infants 0 to 6 months old (based on US research from the 1930s and 1940s).60 A UL is the maximum level of total chronic daily intake that is unlikely to pose risks of adverse effects to the most sensitive members of the healthy population.61 A fetal UL was not determined but would be significantly lower, because in the unborn fetus, “sensitivity increases due to active placental transfer, accumulation of certain nutrients in the amniotic fluid, rapid development of the brain.”62

Fetal blood levels of fluoride can vary widely, but they average about two-thirds of maternal levels. Therefore, when a pregnant woman consumes 3 mg of fluoride, her fetus is exposed to the equivalent of consuming about 2 mg of fluoride – an amount nearly three times the Tolerable Upper Intake Level of a 6-month-old infant.
     
“As intake increases above the UL,” the IOM says “the risk of adverse effects increases.”63 Again, fluoridation promoters say not to worry, because the only adverse developmental effect from a chronic intake of fluoride above its UL is dental fluorosis, a cosmetic not a health issue. “Because the cosmetic effects of the milder forms of enamel fluorosis are not readily apparent,” the IOM selected moderate enamel fluorosis as the critical adverse effect for infants and children.64
     
The IOM did not consider adverse neurological effects, only dental fluorosis. There is, however, a connection between tooth development and brain development.

Developmental Defects Increase with Fluoride Levels in Drinking Water

All enamel defects are indications of severe stress, because they result from systemic cellular disruption during prenatal and early postnatal life that can affect other ectodermally derived structures, including the brain. Chronologically distributed enamel defects are a valuable aid in neurologic diagnosis, since they occur commonly in brain-damaged children. Developmental enamel defects in primary teeth have been found at least twice as frequently in children with mental retardation as in control children.65,66
     
Some enamel defects are essentially birth defects resulting from a pregnant woman’s consumption of fluoride. Similarly, a thin upper lip and flattened philtrum (the groove in the middle of the upper lip) are birth defects resulting from consumption of alcohol during pregnancy. They certainly signify more than a cosmetic effect, as does the gray-blue line on the gums of people with lead poisoning.

Dental studies show that the prevalence and severity of developmental defects of enamel in children increase significantly as fluoride levels in drinking water increase from less than 0.2 mg/l to more than 0.7 mg/l.67-70 Fluoride supplements (0.25 to 0.75 mg/day) are also associated with developmental defects of enamel.71 Note: research shows that the use of fluoride supplements (1.5 mg/day) during pregnancy doubles fetal blood concentrations of fluoride.72
     
Fluoride levels in amniotic fluid have been positively correlated in a dose-response relationship with fluoride content and pathology of fetal bones – with significantly greater fluoride levels in fetuses born to mothers with dental fluorosis.73
     
British researchers estimate the prevalence of dental fluorosis of all levels of severity to be 15% in nonfluoridated areas and 48% in fluoridated areas.74
     
Choi et al. (2015) found that developmental neurotoxicity was associated with dental fluorosis. Children with fluoride-induced mottling of their teeth – even the mildest form that appears as whitish specks on the enamel – showed lower performance on some neuropsychological tests.75,76

Genetic Susceptibility to Fluoride’s Adverse Effects

Fluorosis severity does not depend just on the amount of fluoride that one consumes. There are individual genetic and metabolic factors involved (as there are in autism spectrum disorders). Animal studies reveal a genetic component in the pathogenesis of dental fluorosis and in bone response to fluoride exposure.77 In humans, severity of dental fluorosis varies individually at the same level of intake.72
     
Genetic sensitivity to fluoride’s adverse neurological effects was confirmed by Zhang et al. (2015), who found that children with a variation of the COMT gene, which is associated with cognitive performance, had steeper cognitive decline from exposure to fluoride. Also, poor IQ scores were observed in the high fluoride exposure group (1.4 mg/l) compared with controls (0.63 mg/l).78 Note: for generations, the recommended fluoride level in US public drinking water was allowed to range up to 1.7 mg/l.

SSRIs and Autism

In genetically susceptible individuals, autism may result from maternal exposure of a fetus to minute concentrations of pharmaceuticals, such as Prozac, a selective serotonin reuptake inhibitor (SSRI).79 Because serotonin is critical to fetal brain development, concerns have arisen regarding prenatal exposure to SSRIs that manipulate serotonin levels 80 Serotonin elevation in the blood is one of the better-documented and consistent findings in autism and is probably gastrointestinal in origin 81 Note: 95% of the serotonin in the body is located in the gut.
     
Research shows that prenatal exposure to SSRIs is associated with an increased risk of autism.82 A major study published in December 2015 looked at outcomes of 145,456 pregnancies over 12 years. The University of Montreal researchers found that taking SSRIs during the second or third trimester of pregnancy more than doubled a child’s risk of being diagnosed with autism by age seven.83
     
Two of the most commonly prescribed SSRIs, Prozac (fluoxetine) and Paxil, contain fluorinated compounds. According to Gary M. Whitford, PhD, DMD, an expert on fluoride metabolism, a 20 mg dose of fluoxetine can provide up to 3.3 mg of fluoride, “depending on how much fluoride ion is released during the drug’s metabolism.”84 Note: Whitford was a key member of the Institute of Medicine panel that determined dietary reference intakes for fluoride.

Preeclampsia, Autism, and Fluoride

Taking SSRIs during pregnancy is also associated with preeclampsia, the dangerous pregnancy complication with immediate and lifelong consequences for mother and child. In a study involving 5731 pregnant women, the incidence of preeclampsia was 15.2% among those who continued SSRIs beyond the first trimester, compared with 2.4% among nonusers.85
     
Preeclampsia also increases the risk of having a child with autism spectrum disorder, and risk increases with greater preeclampsia severity.86,87 Preeclampsia has the same key subcellular mechanism of pathogenesis as dental and skeletal fluorosis, endoplasmic reticulum (ER) stress. In fluorosis, fluoride causes the ER stress. In preeclampsia, the cause is still unknown (as discussed by the author).88
     
Fujita et al. (2010) found that autism spectrum disorder is related to ER stress induced by mutations in the genes encoding synaptic cell adhesion molecules, and that PSD-95 is involved.89,90 As discussed above, fluoride decreases the expression level of PSD-95 in the brain.

Fluoride, Premature Birth, and Autism

Substantial laboratory and clinical evidence suggests that maternal fluoride consumption is a risk factor for premature birth, a leading cause of long-term neurological disabilities in children (as discussed by the author).91 Premature birth is also significantly associated with autism. Large-scale population-based studies show that the prevalence of autism is 2 to 4 times higher in preterm children than in children born at full term.92,93
     
The preterm gut experiences abnormal bacterial colonization with a decreased rate of diversification and altered microbiome composition. It also has an increased number of pathogenic bacteria.12 Placentas collected after preterm births have significantly lower levels of bacteria that act a bit like natural versions of medications used to stop preterm contractions.94
     
A December 2015 review concluded, “The maternal oral, vaginal, and gut microbiome influence the risk of pregnancy outcomes that have profound impacts upon the health of the neonate and infant, including preterm birth, preeclampsia, gestational diabetes, and excessive gestational weight gain.”95

Hypothyroidism, Autism, ADHD, and Fluoridated Water

Fluoride effects on thyroid function are well documented. Thyroid hormones are essential for fetal and neonatal brain development, and even slight alterations during critical periods of development can have severe consequences on the development of the child.96 Andersen et al. (2015) observed that children born to mothers with thyroid dysfunction had an increased risk of developing autism spectrum disorders, attention deficit/hyperactivity disorders (ADHD), and psychiatric disease in adolescence and young adulthood.97 Klein et al. (2001) found an inverse correlation between severity of women’s hypothyroidism and the IQ of their children.98
     
In 2015, a major population-level study that analyzed data from 99% of England’s 8020 general medical practices showed a positive association between patients diagnosed with hypo-thyroidism and fluoride levels in their drinking water. High hypothyroidism prevalence was 30% more likely in practices located in areas with fluoride levels in drinking water in excess of 0.3 mg/l. Practices located in the West Midlands (a wholly fluoridated area) were nearly twice as likely to report high hypothyroidism prevalence in comparison to Greater Manchester (nonfluoridated area).99

The study did not include undiagnosed subclinical hypo-thyroidism. The National Research Council (2006) said that in pregnant women, subclinical hypothyroidism is associated with “decreased IQ of their offspring.”100
     
The most common neuro-developmental disorder of childhood is ADHD. Another large-scale population-based study published in 2015 revealed that artificial water fluoridation prevalence was significantly positively associated with ADHD prevalence in the US. After controlling for socioeconomic status, each 1% increase in artificial fluoridation prevalence in 1992 was associated with approximately 67,000 to 131,000 additional ADHD diagnoses from 2003 to 2011.101

More Fluoride Absorbed from Artificially Fluoridated Water

Fluoridation promoters claim that because fluoride compounds have always been naturally present in drinking water, fluoride cannot be a factor in the increasing prevalence of developmental neurotoxicity. However, they overlook the fact that the degree of absorption of any fluoride compound after ingestion is correlated with its solubility. The readily water-soluble industrial fluorides (sodium fluoride, sodium silicofluoride, fluorosilicic acid) used to artificially fluoridate drinking water are rapidly and almost completely absorbed, in contrast to low-soluble natural compounds such as calcium fluoride. The solubility of fluoride correlates generally with the degree of toxicity.72,102
     
Industrial fluorides are added to nearly three-fourths of US public water supplies; therefore substantial amounts of fluoride are also ingested from foods and beverages processed in fluoridated cities. Note: women are advised to drink more water when pregnant.

Fluoride, Copper, and Autism

Water fluoridation chemicals have been shown to increase the leaching of lead and copper from brass plumbing fixtures into tap water (as discussed by the author).103 Copper has an antagonistic relationship with zinc. Excess copper levels and zinc deficiency are common in children diagnosed with an autism spectrum disorder.104
     
Due to the multifaceted effect of zinc on gut development, it is likely that insufficient zinc supply will affect development of the fetal GI tract, contributing to many of the reported GI problems associated with autism.105

Prenatal Fluoride: All Risk and No Benefit

The US Food and Drug Administration (FDA) has classified fluoride as a Pregnancy Category C drug, which “may pose risks similar to a drug in Category X.”106 The risks of a Category X drug clearly outweigh potential benefits.
     
What are the potential benefits of ingesting fluoride during pregnancy? For the child, none. The FDA has long prohibited claims that prenatal fluoride supplements benefit the teeth of children.107 For the mother: “No published studies confirm the effectiveness of fluoride supplements in controlling dental caries among persons ages >16 years.”108 A 2015 Cochrane Review could not identify any evidence determining the effectiveness of water fluoridation for preventing caries in adults.109

Lack of Fluoride-Pregnancy Research

As the National Scientific Council on the Developing Child points out, “There is no credible way to determine a safe level of exposure to a potentially toxic substance without explicit research that differentiates its impact on adults from the greater likelihood of its adverse influences on the developing brain during pregnancy and early childhood.”59
     
“Overall, the available studies of fluoride effects on human development are few and have some significant shortcomings,” concluded the National Research Council in 2006. “To determine the possible adverse effects of fluoride, additional data from both the experimental and the clinical sciences are needed.”110

A decade later, explicit research into fluoride’s ability to interfere with fetal brain development has yet to be done, despite the reality that US fetuses are routinely overexposed to the developmental neurotoxicant fluoride and that autism is becoming epidemic. A PubMed title search for “autism” shows that 2190 scientific papers were published in 2015. For “fluoride,” 627 were published that year. A title search for “autism and fluoride” shows that no studies have ever been published.
     
In the Saarland University study discussed above, when Loskill et al. (2013) exposed artificial teeth to a solution of 1000 mg/l fluoride ion (the concentration in toothpaste) for 5 minutes, all bacteria species tested exhibited lower adhesion forces by a factor of 2. Since then, no further research into fluoride and adhesion forces has been published, even though much attention has recently been given to the gut–brain connection. It is not known how lower concentrations and longer durations of fluoride exposure affect bacterial adhesion forces and health in the developing GI tract. Note: when pregnant women used a daily mouth rinse that contained 225 mg/l of fluoride ion, colonization of their infants by cariogenic bacteria was delayed by 4 months.111

Pregnancy and Fluoride Do Not Mix

Fluoride’s role in the growing pandemic of developmental neurotoxicity requires urgent and thorough investigation. We cannot afford further delay, because it may turn out that, as with lead and alcohol, no amount of fluoride should be considered safe during pregnancy.

The good news is that on November 19, 2015, the US National Toxicology Program announced plans to conduct new laboratory studies to evaluate the effects of fluoridated water on “developmental neurobehavioral toxicity.”112 The bad news is that this could take many years.
     
In the meantime, based on the government’s own research and recommendations discussed in this report, women who are pregnant (or intend to be) should avoid consumption of fluoride in tap water, bottled water, and supplements – especially if they have dental fluorosis, the visible evidence of their genetic susceptibility to fluoride’s toxicity. Also avoid beverages made in fluoridated cities, as well as exposure to fluoride from dental products and procedures.

When a pregnant woman consumes fluoride, so does her baby. Why take the risk? Not ingesting fluoride has no downside for the fetus; however, its consumption may increase the risk of neurological deficits.
     
A worthy community endeavor would be to ensure that families and health organizations are aware of this pregnancy warning for fluoride.

For centuries, humankind considered the womb environment sacred, free of violence and trespass. In that prenatal environment, with unbelievable precision, cells replicate, move about, and form buds and limbs and brains and sensory and reproductive organs, contributing to the most miraculous phenomenon on earth. … Unfortunately, when development is violated in the womb … the social and economic impacts are incalculable.
– Theo Colborn, author of Our Stolen Future

John D. MacArthur’s previous contributions to the Townsend Letter
include five reports: “Too Much Copper, Too Little Zinc, and Cognitive
Deterioration in Alzheimer’s Disease
” (with George J. Brewer, MD), and
“Overdosed: Fluoride, Copper, and Alzheimer’s Disease” (October 2013);
“Fluoride and Preterm Birth” (November 2013); “Placental Fluorosis:
Fluoride and Preeclampsia
” (May 2015); and “Fluoride and Mental Decay: Causation and Correlation” (October 2019).
Links to his other writings are at johndmacarthur.com.

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The Townsend Letter has published five other reports by John D. MacArthur: “Placental Fluorosis: Fluoride and Preeclampsia” (May 2015); “Fluoride and Preterm Birth” (November 2013); “Too Much Copper, Too Little Zinc, and Cognitive Deterioration in Alzheimer’s Disease” (with George J. Brewer, MD) and “Overdosed: Fluoride, Copper, and Alzheimer’s Disease” (October 2013); “Cell Phones and the Brain” (July 2002).