"I recollect that, when I had the great pleasure of seeing you at Southampton, now a 12 months since, we had some conversation on the bad effects of lead taken inwardly; and that at your request I promised to send you in writing a particular account of several facts I there mentioned to you, of which you thought some good use might be made. I now sit down to fulfill that promise."

So begins a letter written by Benjamin Franklin to Benjamin Vaughan on July 31, 1786. His recollection of lead's dangers begins in his boyhood Boston, where rum distilleries were prohibited from using leaden still-heads because they contaminated the rum with lead - causing people to lose the use of their hands.

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As the letter continues, Franklin recalls the time when he was working in a print shop in London and received advice from an old workman who may have saved Franklin's ability to write with a steady hand. The workman discouraged young Benjamin from warming the cases of leaden types before the fire. Although it made the cold metal easier to handle, others who followed the practice had met with disaster. Their hands would shake and they became so ill they could not work. Franklin writes:

"One of whom that used to earn his guinea a week, could not then make more than ten shillings, and the other, who had the dangles, but seven and sixpence. This, with a kind of obscure pain, that I had sometimes felt, as it were in the bones of my hand when working over the types made very hot, induced me to omit the practice."

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"But I have been told of a case in Europe, I forget the place, where a whole family was afflicted with what we call dry bellyache, or colica pictonum, by drinking rain water. It was at a country-seat, which being situated too high to have the advantage of a well, was supplied with water from a tank, which received the water from the leaded roofs."

"This had been drunk several years without mischief; but some young trees planted near the house growing up above the roof, and shedding the leaves upon it, it was supposed that an acid in those leaves had corroded the lead they covered and furnished the water of that with its baneful particles and qualities."

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"This, my dear friend, is all I can at present recollect on the subject. You will see by it, that the opinion of this mischievous effort from lead is at least above sixty years old;

and you will observe with concern how long a useful truth may be known and exist, before it is generally received and practised on."

I am, ever, yours most affectionately,

B. Franklin

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In ancient Italy magnificent aqueducts carried water from the mountains, supplying the people of Rome with 220 million gallons of water per day. Inside the city, water was distributed by lead pipes, supplying 150-200 gallons of water per person per day. The diameter of the pipe determined the cost of water, which flowed continuously. There were no faucets.

The Romans also used lead to halt the fermentation of wines and to preserve food.

Their drinking vessels and cookware were coated with lead glazes. (Ceramics are still a source of lead exposure in modern times.)

Today, we know that lead penetrates the protective blood-brain barrier and is proving to be a risk factor for Alzheimer's disease and senile dementia.

Segovia Aqueduct

Photograph courtesy of
Andrea Reischl and Klaus Johannes Rusch

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Throughout history lead has been intimately related to plumbing. On the periodic table of elements, the symbol for lead is Pb - short for "plumbum" - the Latin word for plumbing.

Plumbism means "lead poisoning." ( Plumbiferous means "containing lead.")

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In 1995, the American Academy of Pediatrics reviewed 18 scientific studies on the correlation between children's mental abilities and lead in their blood. "The relationship between lead levels and IQ deficits was found to be remarkably consistent," the Academy said.

"A number of studies have found that for every 10 ug/dL (microgram per deciliter) increase in blood lead levels, there was a lowering of mean IQ in children by 4 to 7 points." (That's less than a thousandth of a gram of lead.)

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Lead exposure is probably the most preventable cause of antisocial behavior, according to the leading expert on lead exposure and behavior. Herbert L. Needleman, M.D., a professor of child psychiatry and pediatrics at the University of Pittsburgh, has documented how low levels of lead in boys are associated with aggressive behavior, delinquency, and attention disorders - all predictors of criminal behavior later in life.

His groundbreaking studies were instrumental in nationwide government bans on lead from paint, gasoline and food and beverage cans. In 1979, using measurements of lead in children's teeth, Needleman concluded that children with high lead levels in their teeth (but no outward signs of lead poisoning), had lower IQ scores, shorter attention spans, and poorer language skills.

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Needleman's 1996 study published in the Journal of the American Medical Association examined 301 boys in Pittsburgh public schools. Behaviors reported by the boys' teachers and parents - and by the boys themselves - were correlated with the lead measured in their bones.

The boys' behavior was measured at age 7 and again at age 11. Those who had more lead in their bones consistently had more reports of aggressive and delinquent behavior, and problems paying attention.

They were more likely to engage in antisocial activities like bullying, vandalism, truancy, and shoplifting. Furthermore, their behavior got worse as they grew older. In contrast, behavior did not change among boys with less lead in their bones.

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A 2000 study examined the lead levels in 216 youths convicted in the Juvenile Court of Allegheny County, PA - and 201 non-delinquent controls from high schools in Pittsburgh. Convicted male juveniles were nearly twice as likely to have high bone-lead levels, compared to those with no convictions.

Delinquency was associated with higher lead levels even when sex, race, and education, and the neighborhood crime rate were taken into account. About 16% of juvenile delinquent behavior can be attributed to lead exposure.

"This study provides further evidence that delinquent behavior can be caused, in part, by childhood exposure to lead," said Needleman. "Of all the causes of juvenile delinquency, lead exposure is perhaps the most preventable." It is part of a growing body of evidence linking lead to cognitive and behavioral problems in children.¹

Some British doctors have called for routine blood screening of children with learning and behavioral problems. They found that problem youngsters had higher, sometimes toxic, levels of lead. "Our results suggest that children with developmental and/or behavioral problems are more likely to have higher blood concentrations than the general childhood population."²

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A U.S. study found that exposure to lead may be an important environmental link to one of the most dreaded forms of brain degeneration, Alzheimer's disease. Research presented at the May 2000 meeting of the American Academy of Neurology revealed a dramatic correlation between on-the-job lead exposure and the risk of developing Alzheimer's disease in later years.

The occupational histories of 185 people with Alzheimer's disease were compared to 303 people without the disease. Results showed that individuals were up to 3.4 times more likely to develop Alzheimer's if they had worked in jobs exposing them to high levels of lead - either by breathing lead dust or from direct skin contact.

Although most of us need not worry about being poisoned by lead from jobs that require smelting, welding, and the manufacture of lead products - like those represented in this study - we should still be cautious. "Lead exposure remains a major public concern because of its adverse effects on brain development and health in general, even with low exposure levels," says Elisabeth Koss, Ph.D., the study's lead author at Case Western Reserve University.

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This early exposure to lead may be setting the stage for later onset of Alzheimer's disease, according to a report published in the November 1998 issue of Epidemiology. According to Dr. Prince at the London School of Hygiene and Tropical Medicine and the Institute of Psychiatry, England:

"Few environmental risk factors for Alzheimer's disease have been identified. This lack of information may reflect the fact that salient factors affect most of the population in developed countries.

Furthermore, the critical period of exposure may be earlier than hitherto suspected, during the first years of life, as the brain differentiates and develops. Exposure to lead at levels lower than those associated with evident toxicity causes mild intellectual impairment in childhood. I hypothesize that this may be one of the childhood exposures that also confers an additional risk for the onset of Alzheimer's disease."

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Studies suggest that lead may be involved in senile dementia. Myelin-producing cells seem to be particularly vulnerable to lead, and myelin damage is associated with Alzheimer's disease.

Lead inhibits myelination, the formation of the white fatty myelin sheath that surrounds and protects nerve fibers. In animal studies, lead was also shown to interfere with the assembly of microtubules (the tiny pipe-like structures that transport brain chemicals within a neuron) and to form fibers in the brain - structural brain changes associated with dementia.

Early research observed that "the changes in myelin from humans with Alzheimer's disease are more pronounced than in normal aging. These changes might represent severe or accelerated aging."³

A Swedish study of the autopsied brains of people with Alzheimer's disease and vascular dementia determined that the altered fatty acid composition in white matter suggested that "the myelin sheath is the primary lesion site." The same researchers at the University of Goteborg later concluded that membrane lipids selectively diminished in Alzheimer's brains indicate that demyelination is a primary event in late-onset form Alzheimer's disease.⁴

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"We know there's a decline in brain power as we get older - generally we call this 'normal aging,'" said Brian Schwartz, MD, of Johns Hopkins School of Hygiene and Public Health in Baltimore. "Most of the research has been about how chemicals, like lead, affect kids. This is the first study to explore long-term problems caused by exposure to chemicals as adults. Some of what we have been calling 'normal aging' may in fact be due to past exposures to chemicals or other agents that can affect the central nervous system. This is potentially a very important health problem."⁵

A four-year study looked at 535 former chemical manufacturing employees, who had an average of eight years of occupational exposure to lead and an average of 16 years since last working with lead. Blood and bone levels of lead were measured, and neurological tests were given - and compared with 118 non-exposed people from the same neighborhoods.

The lead workers not only had greater declines in test scores, but also in normal age-related declines in brain functions. "The effects of the average level of bone lead found in former lead workers was like five more years of aging on the brain," said Dr. Schwartz.

Significant differences were discovered between the former workers and other participants in tests involved in visual construction, verbal memory and learning, visual memory, planning and organizational ability, and manual dexterity.

" The higher the peak level of lead determined in former lead workers, the greater the decline in brain functions," Schwartz said. "Since these declines were seen long after exposure to lead had stopped, it suggests that the effect of lead on the brain is progressive."

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Once in the brain, lead-induced damage occurs primarily in the prefrontal cortex , cerebellum, and hippocampus . It adversely affects many biological activities at the molecular, cellular, and intracellular levels.

Investigating lead's effects on the brains of children, Israeli researchers report that, lead disrupts the main structural components of the blood-brain barrier, by damaging its capillaries and by injuring the glial cells that protect neurons.⁶

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Exposure to lead alters the developmental processes of synapse formation, resulting in a less efficient brain and cognitive deficits. It blocks the action of calcium atoms in the synthesis of serotonin and dopamine, neurotransmitters essential to normal impulse control and suppression of violent behavior.

A vast amount of evidence accumulated over many years has shown that lead disrupts processes that are regulated by calcium. Researchers at the Kennedy Krieger Research Institute in Baltimore found that "many of the neurotoxic effects of lead appear related to the ability of lead to mimic or in some cases inhibit the action of calcium as a regulator of cell function."^7,8

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One of the mechanisms by which lead damages the brain involves myelin, the white fatty protective substance that insulates nerves and allows them to carry signals quickly and accurately. If the myelin sheath is structurally damaged, then a nerve's electrochemical impulse can become abnormal and uncoordinated. Consequently, the information being conveyed by this nerve is scrambled or cut off.

Myelin-producing cells seem to be particularly vulnerable to lead. Animal studies have shown that lead inhibits myelination (myelin formation), and prolonged lead toxicity causes significant changes in the structure of myelin cells.⁹

An overview of research concluded that the effect of lead poisoning is one of "hypomyelination as seen from the prominent reduction in the content of cerebral myelin. . . Furthermore, the toxin specifically hampers the process of myelin membrane assembly."¹⁰

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In short, the answer is no.

In 1991 the U.S. Centers for Disease Control and Prevention (CDC) established the safe lead levels in the blood at 10 micrograms per deciliter (ug/dL). This level was chosen as the threshold mainly because it was the lowest level that could be detected with an inexpensive test. According to the CDC, setting the standard lower would burden the country's healthcare system.

Actually, there is no safe dose of lead in children's blood. After summarizing recent research, in 1993 the National Research Council (NRC) concluded "there is growing evidence that there is no effective threshold for some of the adverse effects of lead. . . . Even very small exposures to lead can produce subtle effects in humans."

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In the largest study of its kind, data from 4,800 children and adolescents showed that those with blood lead concentrations as low as 5 ug/dL had learning problems. For every 1 ug/dL rise in blood lead levels, their reading scores dropped an average of 1%.

The more data we get, the more we must lower the toxicity threshold for lead. "There is no safe level of blood lead," says Dr. Bruce Lanphear, an associate professor of pediatrics at Children's Hospital Medical Center in Cincinnati. It's estimated that one in every 30 U.S. children suffers from the harmful effects of lead.

" Until the last decade, we couldn't find children with levels low enough to study them in this way," said he study's author Dr. Lanphear at a news briefing in March 2001, sponsored by the Alliance to End Childhood Lead Poisoning and the American Public Health Association.

His research team also measured blood lead levels in 276 New York children - twice a year, from six months to five years old. At age five, the kids were given an IQ test. Those with a lead concentration of less than 10 ug/dL scored on average more than 10 points lower on the Stanford-Binet IQ test, compared to children with concentrations of less than 1 ug/dL.

Levels as low as 2.5 ug/dL were associated with lower scores in tests of reading and mathematics. (The CDC's threshold of safety established in 1991 is still 10 ug/dL.) Lanphear said the study also found that for every additional 10 ug/dL increase in blood-lead concentration, IQ declined by an average of 5.5 points.

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Neurologists at Shaare Zedek Medical Center in Jerusalem found a direct link between low-level long-term exposure to lead and deficits in cognitive performance and behavior in childhood through adolescence.

They also concluded that "there is no threshold below which lead remains without effect on the central nervous system."¹²

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Researchers at the College of Human Ecology, Cornell University, released a new study in April of 2003 to examine low blood lead concentration and IQ. The results suggest that there may be more U.S children who are adversely affected by environmental lead than previously estimated. In the study, 172 children had their blood lead concentrations measured at 6, 12, 18, 24, 36, 48, and 60 months of age.

These same children were given the Stanford-Binet Intelligence Scale at the ages of 3 and 5 years. 101 of the 172 children whose blood lead concentrations measured below 10 µg per deciliter (the CDC's threshold of safety) showed a 7.4 point decline in IQ.¹³

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Lead is most devastating to unborn children, because the "placental barrier" has been shown to be of no effect in stopping the flow of lead from maternal blood to the developing fetus.

According to Walter J. Crinnion, N.D., a faculty member at Bastyr University in Seattle, where he teaches environmental toxicity and clinical ecology: "Studies have shown that the level of lead in the fetus is equal to that in the maternal blood.

This placental transfer of lead begins as early as the 12th week of gestation and continues throughout fetal development."¹⁴

For every increase of five micrograms of lead per deciliter of blood, the risk of spontaneous abortion nearly doubles, according to the results of a two-year Mexican study.¹⁵

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Lise Eliot, Ph.D., author of What's Going On In There? - How the Brain and Mind Develop in the First Five Years of Life, emphasizes that "of all the fetal organs, the central nervous system is probably the most sensitive to the wide range of prenatal influences, because its development is so protracted - from three weeks after conception all the way to adolescence."

In her 1999 book she stresses the danger of prenatal exposure to lead and how its effects are quite similar to malnutrition:

" Lead interferes with the function of many enzymes in the body. It is particularly troublesome during development because it blocks mineral absorption, energy utilization, and DNA synthesis - all steps that allow cells to grow and divide.

Consequently, women exposed to lead have higher rates of infertility, miscarriage, stillbirth, and premature birth, and are likelier to give birth to babies with minor defects.

" Of wider concern are the subtler effects on mental function seen among children exposed to lead before birth. Researchers have now documented small but significant mental deficits among children whose fetal lead level (measured in umbilical cord blood at birth) exceeded 10 ug/dL. . . . If the exposure ends at birth, the effect appears to be reversible and children recover normal IQ scores by four or five years of age. But if a child is also exposed to lead after birth (as is often the case) or is raised in an otherwise disadvantaged environment, his intelligence may be permanently compromised."

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Beginning in the prenatal ninth month, the protective myelin sheath around nerve fibers begins to form. This process is called myelination and continues into a person's mid-twenties. Myelination of the prefrontal cortex is especially slow.

Lead damages myelin and that is why lead-induced myelin damage at an early age can be most devastating.

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According to Ruth Ann Norton, executive director of the Baltimore-based Coalition to End Childhood Lead Poisoning, "lead kids" have very low levels of concentration, are very disruptive, and have violent tendencies.

The relationship between hair lead levels of children and their attention-deficit behaviors in the classroom was evaluated at the University of Massachusetts. Researchers found a "striking dose-response relationship between levels of lead and negative teacher ratings. . . An even stronger relationship existed between physician-diagnosed attention-deficit hyperactivity disorder and hair lead in the same children."¹⁶

A similar study done at Vrije Universiteit of Amsterdam found that children with relatively high concentrations of lead in their hair "were significantly less flexible in changing their focus of attention."¹⁷

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The greatest source of poisoning is leaded gasoline, one of last century's most infamous inventions - and one that from the beginning was known to be detrimental to human health, yet was promoted by industry for profit. In "The Story of Lead," veteran environmental reporter Peter Montague reports: The period of greatest lead use was 1945-1971, after which it began to decline. In those years, 165,000 to 275,000 tons of lead dust spewed from the exhaust pipes of American automobiles each year. Americans born during these years have 300 to 1000 times as much lead in their bodies as pre-Columbian indigenous people had.

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Each computer monitor and television contains four to eight pounds of lead. In Oregon alone, households and businesses junked nearly 50,000 tons of computers, televisions, and other electronic equipment during 2000. This electronic waste is polluting landfills with lead, mercury, and other regulated hazardous materials.

According to the State Department of Environmental Quality, 700,000 new computers are sold annually. An estimated 1.1 million old computers are stored in basements or closets, but only about 11% are recycled or reused.¹⁸

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For some reason, paint seems to be the delivery system of choice for brain damage. Will future archeologists be baffled by a society whose walls were more vibrant than its brain cells?

In the United States, paint is now the chief source of the lead that poisons children. Leaded paint is still very common in older houses. More than 80% of U.S. housing built before 1980 contain some lead-based paints. In particular, white paint used to be made with lead carbonate and yellow paint from lead chromate.

Although lead - and mercury, another toxic metal - are no longer allowed in paint, other chemicals threaten the brain. According to their labels, some paints contain solvents that "can cause permanent brain and nervous system damage."

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The EPA permits our drinking water to have 15 parts per billion of lead, but according to one of their own studies: "Drinking water supplied to 30 million people in 819 cities contains unhealthy levels of lead."¹⁹

Environmental lead exposure from industrial pollution and lead residues in soil further add to the accumulating burden of lead in the body and brain.

Today, acidic chemicals being added to drinking water are magnifying the uptake of lead into the bloodstream and the brain. Acidic chemical added to drinking water leaches lead from plumbing.

More than 98% of U.S. homes have lead in their plumbing systems. It comes from lead pipes and copper pipes connected by lead solder. Chrome-plated faucets are made of brass containing up to 8% lead.

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Water systems providing 91% of U.S. fluoridated water and serving 140 million people are fluoridated with 200,000 tons of industrial-grade silicofluorides (SiFs) each year - not with pharmaceutical-grade FDA-approved chemicals, as most people would expect for a substance they consume daily.

" Commercial SiFs are likely to be contaminated with arsenic, heavy metals, and radionuclides, since they are waste products from fertilizer manufacture and uranium extraction from phosphate rock."²⁰

The December 2000 edition of NeuroToxicology published research led by Roger D. Masters, Dartmouth College Research Professor and Nelson A. Rockefeller Professor of Government Emeritus. It showed that public drinking water treated with fluosilicic acid or sodium silicofluoride, known as silicofluorides (SiFs), is linked to higher uptake of lead in children.

Masters and his collaborator Myron J. Coplan, a consulting chemical engineer, have now studied the blood lead levels in more than 400,000 children in three different samples. In each case, they found a significant link between SiF-treated water and elevated blood lead levels.
Masters and Coplan note that their recent studies contain the most extensive empirical evidence of the health and behavioral costs of silicofluorides. "If further research confirms our findings," Masters says, "this may well be the worst environmental poison since leaded gasoline."

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To this day, the substitution of silicofluorides (SiFs) in public water treatment facilities has never been subjected to appropriate animal or human testing. The United States Environmental Protection Agency (EPA) admitted that they have no idea what the long-term consequences are to humans of ingesting silicofluorides in drinking water:

" To answer your first question on whether we have in our possession empirical scientific data on the effects of fluosilicic acid or sodium silicofluoride on health and behavior, our answer is no... With the exception of some acute toxicity data... unable to find any information on the effects of silicofluorides on health and behavior." - EPA letter to Rogers D. Masters, November 16, 2000

Roger D. Masters, President of the Foundation for Neuroscience & Society says, "Silicofluorides are largely untested. Virtually all research on fluoridation safety has focused on sodium fluoride, even though the studies in the 1930s showed important biological differences between these chemicals."

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Tacoma, Washington temporarily ceased water fluoridation during a 1992 drought, and lead levels dropped from 32 ppb (parts per billion) to 17 ppb. The EPA's Maximum Contaminant Level for lead is 15 ppb.²¹

In Thurmont, Maryland, "Lead levels in town water have decreased significantly since town officials stopped adding fluoride."²²

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Most vinyl mini-blinds imported to the United States are a source of lead, which is used as a vinyl stabilizing additive for rigidity and color retention. Tests by the Consumer Product Safety Commission has determined that these mini-blinds deteriorate and their dust contains high levels of lead that can end up on children's hands and in their mouths.

Burning candles with lead in their wicks can raise the concentration of lead in the air - as much as 36 times that allowed by the EPA - for many hours after the candle is no longer burning.

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A new 2003 study called the Trial to Assess Chelation Therapy (TACT) is being conducted by the National Institutes of Health (NIH) and sponsored by the National Center for Complementary and Alternative Medicine (NCCAM) National Heart, Lung, and Blood Institute (NHLBI). The study will compare 40 infusions of chelation solutions with placebo given to patients with coronary artery disease.

The researchers hope the results will determine significant positive results or a null result, either of which will help with clinical practice and health policy decisions. As of this writing patient recruitment for the study has yet to begin, but the results of this trial are sure to be big news.²⁴

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Produced by the University of Calgary Faculty of Medicine Research Team

http://commons.ucalgary.ca/mercury/
showcasetv/mercury

Researchers at the University of Calgary Faculty of Medicine experimented on neurons by introducing mercury and observing what happened. The results were startling.

Mercury ions attach to the neuron and cause the protective microtubules surrounding the neuron to break down. The unprotected neuron joins other unprotected neurons and they tangle together in clumps. These neurons are now damaged and do not function properly.

When the researchers tested other metals such as aluminum, lead, cadmium and manganese, they did not produce the same type of neuron degeneration.²⁵

To see the experiment in action, see The Effects of Mercury on Neurons movie.

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Some fish and shellfish can be contaminated with methylmercury. Usually larger and older fish have higher levels of mercury in their tissues.

Air from incinerators, burning coal and industries that burn certain fuels contain mercury.

Mercury is used in some dental and medical treatments. Mercury can be released within the patient’s body and workplace air can also be contaminated.²⁶

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Lead is not the only toxic metal that crosses the blood-brain barrier. In a surprising study with serious implications for human brain health, researchers have shown that mercury can enter into the brains of fish via sensory nerves – thus bypassing the blood-brain barrier.

Scientists at Canada's Maurice Lamontagne Institute and the Swedish University of Agricultural Sciences demonstrated that mercury dissolved in lake and river water can directly enter the water-exposed sensory receptors – for odor, taste, vibration, and touch – on nerves that go directly to the fishes' brains.

The scientists believe that "uptake of metals such as mercury and the subsequent transport along sensory nerves is a process common to all fish species, and in this respect, it is possible that other toxins (such as pesticides) also could reach fish brains in this way." Earlier studies with rodents showed that mercury, manganese, and cadmium can be transported to the brain through the olfactory nerves in the nasal passage.

"The fact that mercury is transported along fish nerves can be extrapolated to hum