Fluoride: The Deadly Legacy by Gary Null, Ph.D. Lead isn't the only metal that interacts with fluoride in a toxic combination. Aluminum is another.
In 1976, Dr. D. Allman and coworkers from Indiana University School of Medicine fed animals 1 part-per-million (ppm) fluoride and found that in the presence of aluminum, in a concentration as small as 20 parts per billion, fluoride is able to cause an even larger increase in cyclic AMP levels. Cyclic AMP inhibits the migration rate of white blood cells, as well as the ability of the white blood cell to destroy pathogenic (disease-causing) organisms. The fact that fluoride toothpastes and school based mouth rinses are packaged in aluminum accentuates the effect on the body.(170) 
    Research conducted by Mullenix and colleagues in 1995 indicated that rats treated with low doses of fluoride cause sex- and dose-specific behavioral aberrations with a common pattern.(171) Rats exposed prenatally became hyperactive, while those exposed post-natally became hypoactive. This effect was confirmed by a 2001 study in which administration of sodium fluoride with drinking water produced both behavioural and dental toxicities. A suppression of spontaneous motor activity, a shortening of rota-rod endurance time, a decreased body weight gain and food intake, a suppression of total cholinesterase and acetylcholinesterase activities and dental lesion were observed in test animals. Serum fluoride concentration was raised markedly and that of calcium was decreased in the animals.(172)
A 1998 study by Julie A. Varner and colleagues at the Psychology Department of Binghamton University (NY) shows that neurotoxic effects like these are enhanced by the synergetic action of fluoride and aluminum.(173) Varner describes "alterations in the nervous system resulting from chronic administration of the fluoroaluminum complex or equivalent levels of fluoride in the form of sodium-fluoride. The rats were given fluoride in drinking water at the same level deemed "optimal" by pro-fluoridation groups, namely 1 part per million (1 ppm). Most pronounced damage was seen in animals that got the fluoride in conjunction with aluminum. The pathological changes found in the brain tissue of the animals were similar to the alterations found in the brains of people with Alzheimer's disease and dementia. The authors speculate that fluoride enables aluminum to cross the blood-brain barrier. These results are especially disturbing because of the low dose level of fluoride that shows the toxic effect in rats - rats are more resistant to fluoride than humans."(174) 
    Another study done in Czechoslovakia adds force to the idea that aluminum may act synergetically with fluoride to trigger the mechanisms of Alzheimer's disease. The study shows that some of pathologic changes associated with AD are not induced by aluminum alone, but by the aluminofluoride complexes. These complexes may act as the initial signal stimulating impairment of homeostasis, degeneration and death of the cells. By influencing energy metabolism these complexes can accelerate the aging and impair the functions of the nervous system. "In respect to the etiology of AD, the long term action of aluminofluoride complexes may represent a serious and powerful risk factor for the development of AD," the authors conclude.(175)
    Incidentally, if you're thinking that fluoride and aluminum exist in separate worlds and are unlikely to find each other in the normal course of events, think again. Fluoride is a direct byproduct of aluminum production. Aluminum is often added to drinking water as a flocculating agent, by the same folks who add the fluoride-your local water authority. Aluminum and fluoride form a number of complexes, the most deadly of these being aluminum tetrafluoride.(176) Czech researchers have shown that the body reacts to aluminum tetrafluoride as if it were a phosphate ion capable of triggering G proteins. G-proteins are water-soluble substances (i.e. hormones, neurotransmitters, and growth factors) that transmit messages from the outside to the inside of a cell.(177) Aluminum tetrafluoride is capable of switching on G proteins without hormones, neurotransmitters, or growth factors present.(178) 'This, notes Paul Connett, 'is the most worrisome aspect of fluoride subtle biochemistry."

  A team of scientists have investigated a case of vaccine-associated chronic fatigue syndrome (CFS) and macrophagic myofasciitis in an individual demonstrating aluminium overload. .....a possible mechanism whereby vaccination involving aluminium-containing adjuvants could trigger the cascade of immunological events that are associated with autoimmune conditions, including chronic fatigue syndrome and macrophagic myofasciitis. [2008 Nov] Vaccine-related chronic fatigue syndrome in an individual demonstrating aluminium overload

A multitude of studies have shown that aluminum, especially if combined with fluoride, is a powerful brain toxin and that it accumulates in the brain. How Vaccines Can Damage Your Brain: Vaccines, Depression and Neurodegeneration After Age 50: Another Reason to Avoid the Recommended Vaccines By Russell L. Blaylock, M.D.

Polysorbate-80 is used in pharmacology to assist in the delivery of certain drugs or chemotherapeutic agents across the blood-brain-barrier. What viral, bacterial, yeast, heavy metal or other vaccine containing ingredient need to pass into the brains of our children? Do they belong in the brain? Is that part of the needed immune response to protect our children from disease? Do vaccine materials pass across the blood-brain barrier with the help of Polysorbate-80? If so, are there complications from being in the brains of our children? Is this another connection to help us get an understanding of why 1 in 150 children have autism, or 1 in 6 children has developmental/learning disabilities? Aluminum and Vaccine Ingredients: What Do We Know? What Don’t We Know? by Lawrence B. Palevsky, MD, FAAP

While mercury has gotten all the attention, aluminum (found in most vaccines) is also a major culprit in this shocking saga. Added to most vaccine are a number of substances either used during manufacturing or designed as an immune booster (adjuvant). These include albumin, aluminum (either as aluminum hydroxide, aluminum phosphate or alum also known as aluminum potassium sulfate), various amino acids, DNA residues, egg protein, gelatin, monosodium glutamate (MSG), MRC-5 cellular protein and various antibiotics. Not listed on official lists are bacterial and viral contaminants, which can include their particulate, fragmented matter.94-99
    The purpose of the aluminum compounds is to dramatically boost the immune reaction to the vaccine and make it prolonged, since some of the aluminum remains in the site of injection for years. Aluminum was first added to vaccines in 1926. Many of the other components added to the vaccines also boost immunity, especially that of undesirable components of the immune system, such as the B-cells.
    Because these vaccine adjuvants are designed to produce a prolonged immune stimulation, they pose a particular hazard to the developing nervous system. Studies have shown that immune activation can last as long as two years after vaccination. This means that the brain’s microglial cells are also primed for the same length of time, and possibly longer.
    A new emerging syndrome called macrophagic myofasciitishas been attributed to the aluminum adjuvant in vaccines and is especially associated with the hepatitis B vaccine and the tetanus vaccine.100 Victims of this syndrome suffer severe muscle and joint pains and severe weakness. Subsequent studies, since the syndrome was first described in France, indicate widespread, severe brain injury as well, as confirmed by MRI scanning.101,102 This brain syndrome has been described in American children as well.
    It is known that aluminum accumulates in the brain and results in neurodegeneration. The evidence for a link between aluminum neurotoxicity and Alzheimer’s disease continues to grow stronger. Aluminum, like mercury, activates microglia leading to chronic brain inflammation, which is a major event in both Alzheimer’s disease and Parkinson’s disease.103-110
    Flarend and co-workers studied the fate of vaccine injected aluminum in the dose approved by the FDA (0.85 mg per dose) using radiolabeled aluminum adjuvant –either aluminum hydroxide or aluminum phosphate, the two approved forms of adjuvants used in vaccines.111 They found that the aluminum was rapidly absorbed into the blood from both forms of aluminum, but that the aluminum phosphate was absorbed faster and produced tissue levels 2.9x higher than aluminum hydroxide. Blood levels of aluminum remained elevated for 28 days with both adjuvants. Elevated aluminum levels were found in the kidney, spleen, liver, heart, lymph nodes and brain.
    This indicates that aluminum from vaccines is redistributed to numerous organs including brain, where it accumulates. Each vaccine adds to this tissue level of aluminum. If we calculate the total aluminum dose from 36 vaccines, we see that the total dose is 30.6 mg and not the 0.85 mg considered safe by the FDA. Of course not all this aluminum ends up in the tissues, but they will accumulate substantial amounts, especially when added to the amount from foods and drinking water. When a number of aluminum-containing vaccines are given during a single office visit, aluminum blood levels rise rapidly and to much higher levels and this elevation persist for over a month, all the time infiltrating the tissues, including the brain with aluminum.
    It is also known that aluminum enhances the toxicity of mercury and that aluminum, even from other sources, increases inflammation in the body.106 The question no one seems to be asking is -does the aluminum act as a constant source of brain inflammation? Research, especially that showing aluminum-triggered microglial activation, seems to indicate it does.112 Dr. Anna, Strunecka, a professor of physiology, found that aluminum readily binds with fluoride to form fluoroaluminum and that this compound can active G-protein receptors, which controls a number of neurotransmitters, including glutamate receptors.46 Giving multiple aluminum-containing vaccines at once would raise blood and tissue levels much higher than when give separately, thus increasing brain levels as well. Fluoride in drinking water, foods and dental treatments would react with the brain aluminum, creating the neurotoxic fluoroaluminum combination. Studies have shown that fluoride also accumulates in the brain.  [March 2008] Vaccines, Neurodevelopment and Autism Spectrum Disorders by Russell L. Blaylock, M.D.

A 12-pound, two-month-old baby could safely receive at least 30 mcg of aluminum per day. A 22-pound one-year-old could receive at least 50 mcg safely.....
........a newborn who gets a Hepatitis B injection on day one of life would receive 250 mcg of aluminum. This would be repeated at one month with the next Hep B shot. When, at two months, a baby gets its first big round of shots, the total dose of aluminum could vary from 295 mcg (if a non-aluminum HIB and the lowest-aluminum brand of DTaP are used) to a whopping 1,225 mcg (if the Hep B vaccine is given along with the brands with the highest aluminum contents). If the Pentacel combo vaccine is given along with the Hep B and Pneumococcus vaccines, the total aluminum dose could be as high as 1,875 mcg. These doses are repeated at four and six months. With most subsequent rounds of shots, a child would continue to get some aluminum throughout the first two years.
    But the FDA recommends that premature babies, and anyone with impaired kidney function, receive no more than 10 to 25 mcg of injected aluminum at any one time.
    As a medical doctor, my first instinct was to worry that these aluminum levels far exceed what may be safe for babies. My second instinct was to assume that the issue had been properly researched, and that studies had been done on healthy infants to determine their ability to rapidly excrete aluminum. My third instinct was to search for these studies. So far, I have found none.......I can find no references in FDA documents that show that using aluminum in vaccines has been tested and found to be safe.
.........The toxic threshold of aluminum in the bloodstream may be lower than 100 mcg per liter. The buildup of aluminum in tissues has been seen even in patients with healthy kidneys who receive IV solutions containing aluminum over extended periods. [2008] Is Aluminum the New Thimerosal? By Robert W. Sears

Because a newborn's body contains about a liter (300 milliliters) of blood, more than 30 mcg of aluminum floating around in the bloodstream could be toxic if the baby's kidneys aren't working well. The body of a toddler or preschool-age child contains about 1 liter of blood, so more than 100 mcg in his system could be toxic—and, as we've seen, babies can receive more than 1,000 mcg of injected aluminum all at one time........ No one has measured the levels of aluminum absorption by the bloodstream when it is injected into the skin and muscle of infants, or the levels of excretion from the body via urination. All of the FDA and AAP documents that I've read state that aluminum might be a problem, but that they haven't studied it yet, so we should limit the amount of aluminum included in injectable solutions. But, again, no one is talking about the levels of aluminum in vaccines. [2008] Is Aluminum the New Thimerosal? By Robert W. Sears

Several years ago, some suspected cases of aluminum toxicity resulted in various neurologic and degenerative problems. The Cochrane Collaboration, a group that studies health-care issues around the world, wanted to look at a very large study group to see if there was a real correlation between neurologic problems and the aluminum in vaccines. They investigated all the reported side effects of one aluminum-containing vaccine, DTP (no longer used), and looked for any evidence that such vaccines caused more side effects than non-aluminum vaccines. Other than more redness, swelling, and pain at the injection site, they found no indication that an aluminum-containing vaccine caused any more problems, and concluded that no further research should be undertaken on this topic. That is a very bold statement. Most researchers will draw conclusions from the findings of their own research; it's unusual to say that no one else should do any more research into the matter.
    This is especially surprising because of the limitations of the Cochrane Collaboration's study. They looked at the effects of only one standard aluminum-containing vaccine, rather than the effects of all four being administered at once. They didn't study aluminum metabolism itself. They didn't test aluminum levels in children after vaccination, nor did they explore whether or not the amount of aluminum in vaccines builds up in the brain or bone tissues. They looked only for evidence of external symptoms of aluminum toxicity, not internal effects. Nor did they do their own research; instead, they reviewed all available studies conducted by other investigators. Despite all this, the Cochrane Collaboration study essentially closed the book on investigating aluminum toxicity from vaccines, without really having opened it in the first place.  [2008] Is Aluminum the New Thimerosal? By Robert W. Sears

Because no meaningful research has specifically been done on aluminum in vaccines, there is no existing evidence that the amount in vaccines is harmful to infants and children. However, no one has actually studied aluminum levels in healthy human infants after vaccination to make sure it is safe. [2008] Is Aluminum the New Thimerosal? By Robert W. Sears