MERCURY TOXICITY

Mercury is a toxic heavy metal, metallic mercury or elemental mercury is the pure form of Mercury.  It is a shiny silver white metal that is liquid at room temperature. At room temperature some of the metallic mercury will form a colorless, odorless vapor. If you breathe in mercury vapor you can have a metallic taste in your mouth and not be aware of its origin. It can be found in a multitude of forms, which ultimately get into the human organism.  Several forms occur naturally in the environment. The most common are metallic (elemental) mercury, mercuric sulfide (cinnabar), mercuric chloride, and methylmercury. Inorganic mercury compounds are those that occur when mercury combines with other elements like chlorine to form mercuric chloride, 

a common type of antiseptic.  These mercury salts are usually white powders or crystals. When mercury combines with carbon the compounds that develop are called organic. Some organisms in the environment can even change one form of mercury to another. It is these microorganisms in the waterways that convert the inorganic to the organic form of methylmercury. The methylmercury can then enter the soil or water and remain there for a long time, slowly becoming part of the food chain. When small fish eat the methyl mercury in their food supply it gets into their tissues. The larger fish then consume these and we consume the larger fish and thus we become contaminated with methylmercury. The longer the fish lives the more mercury it accumulates in its tissues. The swordfish and the shark have the highest concentrations of methylmercury.  

Mercury is a ubiquitous environmental pollutant.  It enters the environment as a result of the breakdown of minerals in rocks and soil from wind, water, volcanic activity and the natural degassing of the earth's crust.  The rise in this mercury burden has been constant down through the millennia and this has led to a massive rise in the total exposure of humans to this toxin.  Since the beginning of the industrial revolution there has been a continued increase in production for industry through mining and the burning of fossil fuel. The air now has three to six times the mercury it had prior to 1800. Approximately 80% of the mercury released from human activities is elemental mercury, which comes from fossil fuel combustion, mining, smelting, from solid waste incineration, and from the vaporization from amalgam fillings in the teeth of humans. The other 20% comes from fertilizers, fungicides, and municipal solid waste (like waste from discarded batteries, electrical switches, and thermometers). Other areas of contamination come from industrial discharge from industries like paper mills, and the use in the dental profession to repair damaged teeth using mercury based compounds. Of course there are a multitude of industries that are involved in the use of mercury. These include: flour manufacture, paints and solvents, jewelry (cinnabar), laxatives, antiseptics, pharmaceuticals, cosmetics, thermometers, plumbing, floor waxes and polishes, battery manufacture, vaccines, tattoo industry, automobile exhaust, pesticides, fertilizers, tanning industry, food processing, hemorrhoidal suppositories, wood preservatives, air conditioning filters, adhesives and fabric softeners. Other contributors of mercury are contaminated fish, such as tuna, latex wall paint (the ban on mercury in paints took place in 1991) and polluted water. The EPA advises it is safe to drink tap water because the amount of mercury found there is quite small and can't harm you. But what are the cumulative effects over decades? Until the 1970's ethyl and methylmercury were used to protect seed grains from fungal infections, and of course this contaminated our food supply.  In the past the use of mercuric chloride was widespread in everyday antiseptics like Mercurochrome until safer products replaced it.   

A recent presentation to a congressional panel addressed the concern of the U.S. government to the presence of a form of mercury in vaccines. The questionable substance is thimerosal, an antibacterial substance used to prevent contamination 

of the vaccine. Researchers at Columbia University Medical Center voiced their concern, that some children receive several vaccines in one visit, which could conceivably add up to the precautionary limit of mercury determined by the Environmental Protection Agency (EPA), the presentation further stated that the mercury toxicity could lead to brain damage. The harmful mercury-containing substance, thimerosal is not in all vaccines, but is currently in the hepatitis B 

and DPT vaccines.  

Dentistry - Probably the most controversial issue concerning mercury toxicity is in the world of dentistry. Although in the mid 1800’s the American Dental Association opposed the use of amalgam/ mercury fillings as bad practice and itself coined the term “quack” referring to dentists who used such European style fillings (qwecksilber = quicksilver = mercury, hence the name “quack”), they now vigorously support the continued use of this toxic material. Most dental amalgams still contain mercury.

About 98 percent of the North American population develops cavities and mercury amalgams are packed into 80% of them. Unexplained, poorly defined and unclear conditions, often attributed to allergies, frequently clear up after the mercury amalgams are removed from the mouth. Although mainstream dentistry does not agree that the mercury amalgams cause so many problems, there are some dentists who believe that the best thing to do is to remove the amalgams. This must be done very precisely by someone who knows and understands this process, because mercury can slip into the body when the amalgams are being removed. Most dentists who do this procedure recommend nutritional programs containing antioxidant supplements, immune builders, liver detoxifiers, and bowel cleansers to enhance detoxification of this harmful metal.  

The evidence is clear that the relationship between the number of amalgams and the amount of accumulated mercury in the human brain and kidney is significant. The presence of amalgams in the mouth results in a long-term chronic exposure to the toxic effects of mercury.  There are story after story of how the chronic illnesses described above have disappeared or been significantly reduced by removing both the amalgams from the mouth and removing the mercury from the deep tissues of the body. The newer amalgams are made with much more copper and less silver, which consist of 50% mercury.  The other metals are: silver=35%, tin=9%, copper=6% and a trace amount of zinc.  The amalgam is a soft paste when first inserted but hardens in 30 minutes.  Over time with chewing, brushing of the teeth and from wear and tear, the mercury slowly is released from the tooth's surface.  Part of the mercury can become a vapor and be breathed into the lungs.  It can also become dissolved into the saliva and swallowed.  The total amount of mercury involved in the burden to the individual depends on the number of surfaces of amalgam and the total quantity of amalgam in the mouth. Exposure from these fillings can amount to between 50% and 90% of the total exposure of the individual.  These amalgams are unstable because of mercury's low vapor pressure and galvanic action, which leads to the continuous leaking of mercury vapor into the lungs and saliva. Mercury exposure through this routine has been found to exceed government health standards (0.014 micrograms/ kilogram of body weight per day).  For the average adult we are talking about 

1 microgram per day. The World Health Organization (WHO) has found that the exposure from amalgams was 3 to 70 micrograms per day.  In other medical studies they found as high as 500 micrograms per day as the exposure level is gum chewers and people who grind their teeth. Across the board the average amount of mercury that an individual is exposed to from amalgam fillings was 10 mcg. per day (Canadian Health Organization).  

In a large German study with 20,000 people tested at a University Medical Center the average exposure was 10mcg. per day per individual and over 50% of those with 6 or mover fillings had mercury exposure levels that exceeded the EPA health guidelines. In recent years with the high copper amalgams, there is a greater release of mercury than in the old type amalgam.  Thus people with amalgam fillings have levels of intraoral mercury vapor and body exposure levels higher than the level considered to be a significant health risk.  In addition neither the WHO nor any other scientific body has ever found a mercury exposure that was without adverse effects

Another very important consideration related to the amalgam issue is that concerning the galvanic action in the mouth and its effect on the release of mercury vapor.  Having dissimilar metals like gold, mercury, tin, and silver causes galvanic electric currents to be distributed such that the mercury vaporizes more rapidly. Mercury concentrations of in the oral lining in people with amalgam fillings were 20 times greater than to those without.  Some of the local effects can be gingivitis, oral lesions, lichen planus, metallic taste, burning mouth, or even oral cancer.  Amalgam tattoos can be seen next to an amalgam filling.  This is the result of mercury accumulation in the cellular structures of the oral lining.  In the area of a gold cap on an amalgam filling the amount of mercury vapor that can be measured is about 1200 ppm.  Considering the EPA action level for mercury in fish is 1 ppm one should be quite concerned about these massive levels in the mouth. Most people with several amalgam fillings have daily exposure exceeding the U.S. government health guideline for mercury.   

Another important fact is that the amount of mercury released from high copper new amalgams is 50 times that of the original amalgam combination of metals.  They developed these new amalgams to be less corrosive and to have less of an incidence of marginal fractures than the standard amalgam (higher is silver) but they have been found to be unstable during wear and tear and have been found to form droplets of mercury on the surface of the amalgam. A large percentage of the population is sensitive to mercury (36% in a population of 3000 tested). Once it is removed from the mouth there was a dramatic decrease in the sensitivity to mercury. 

Developmental Damage - The human brain develops over a long period of time compared to other organs. There is neuron proliferation and migration that continues into the postnatal period and the blood-brain barrier is not fully developed until the middle of the first year of life. The fetus has been found to develop significant exposure from the toxins that are being carried in the maternal blood and during the period of breast-feeding.  It is often found that the levels of mercury are higher in the fetus than in the mother. Areas of involvement are: cognitive development, calcium dependent neurotransmitter release which results in the depression of levels of the neurotransmitters, abnormalities in the calcium - ATP pump processes that affect cellular nutrition and energy production. Studies have found that mercury can deplete the glutathione and the protein bound sulfhydryl groups. There is thus an inhibition of the -SH containing enzymes with the production of reactive oxygen species (free radicals). This has been a major factor in the etiology of the damage to the immune system and the brain in which there is mitochondrial injury as well as DNA injury.

Some individuals have been found to be more genetically sensitive to the effects of heavy metals. According to various studies over 20% of the children in the U.S. have had their health or learning ability significantly affected by toxic metals such as mercury. There are also various behavioral effects involved as well.  In the work done at the Edelson Center in Atlanta over the last several years it was found that the three most common neurotoxic metals have been tin, mercury, and lead as the root cause or one of the root causes of both ADD syndromes and the Autistic Spectrum Disorders. Many epidemiologists believe that the evidence demonstrates that about 50% of the children in our country have had their learning ability or mental state affected by prenatal or postnatal exposure to toxic substances including both the heavy metals and the toxic chemicals.  It has been proven that the neurotoxic metals, such as mercury, have contributed to, or been the cause of birth defects, developmental delays, learning disabilities, depression, and other varied behavior abnormalities. In addition there is a synergistic effect of these neurotoxic metals and possibly even the chemicals that lead to these neurological areas of damage. When comparing a group of mentally retarded children to controls, it was found that the group of retarded individuals had much higher levels of toxic metals in their bodies. Similar findings have been found in other groups like autistic, dyslexic, and ADD children.  

The number one source of exposure of mercury to infants and children is from the placental transfer of mercury from the mother's body to the babies and from the transmissions of the mercury during breast-feeding.  There are significant amounts of organic mercury that can be found in the mouth as part of root canals and gold crowns over amalgam base.  Mercury vapor from the surface of amalgams is the usual form to cross cell membranes including the blood brain barrier and the placenta. In the most critical periods of development in the fetus and in the early months after birth, children and fetuses are particularly sensitive to the harmful effects of metallic mercury and methylmercury on the nervous system. Methylmercury is the form that is most likely to be associated with the risk for developmental effects.  The effects on the infant may be very subtle or more pronounced, it all depends on the degree of exposure.  In cases where the exposure may be minimal there may not even be anything detected, like a small decrease in I.Q.  It might be necessary to use sophisticated neuropsychological testing tools to determine the minor effects that mercury has had on the developing brain.  In cases of more severe exposure the effects may be very serious, but they may be delayed.  The infant, as in many cases of the autistic spectrum, may be born normal, only to show significant changes at a later time. The delays may not come until one notices delays in the milestones of development like walking, talking, etc. The very serious effects such as blindness, deafness, inability to walk or speak and seizures are usually associated with very severe toxic exposures

Symptoms - Everyone is exposed to mercury.  Some of us are exposed to a great amount and others only little.  Some of us have a great ability to detoxify the mercury and some don't.  The only way to know how the environmental burdens of mercury have affected any individual is to measure the body burden of mercury.  Acute, intermediate and chronic exposures seem to elicit similar neurological effects.  These symptoms become irreversible as the exposure and duration lead to higher concentrations.  The most prominent symptoms that one experiences are: 1) tremors 2) emotional lability (characterized by irritability, shyness, loss of confidence, and nervousness) 3) insomnia 4) memory impairment 5) neuromuscular changes (weakness, muscle atrophy, muscle twitching) 6) headaches 7) polyneuropathy (parasthesias, stocking glove sensory loss, hyperactive tendon reflexes, slowed sensory and motor conduction) 8) cognitive defects with performance problem tests 9) hearing deficits 10) visual field deficits 11) rarely hallucinations. Mercury toxicity may cause decreased attention span, resulting in learning disorders. Other common symptoms of mercury poisoning are arthritis and inflammation, cardiovascular disease, digestive problems, dementia, and allergies.  

The most important organ systems that are affected by mercury are the brain and the rest of the central and peripheral nervous systems, the immune system, the kidney, and the liver.  

The Nervous System - The central nervous system is the most sensitive to the effects of metallic (elemental mercury) the type that comes off the surface of amalgams. Exposure of rats to mercury during the neonatal period resulted in definitive though subtle behavioral changes. In learning tasks the exposed rats showed definite decreases in the ability to learn. Generally the results showed clear-cut evidence for alterations in spontaneous and learned behavior. In some studies there is evidence that there are signs of genotoxic damage to the chromosomes with breaks occurring. In some of the studies there were no signs of damage, so the evidence is still inconclusive but enough to make us aware that the possibility exists for that type of damage.  

Metallic mercury gets into the bloodstream and then right into the brain. Mercury damages the blood-brain barrier. It is directly neurotoxic and damages nerve cells.  Mercury also generates free radicals that directly damage nerve cells. There is an excess of oxidative stress and the depletion of glutathione and other thiols causing increased neurotoxicity from interactions of reactive oxygen species (free radicals), glutamate and dopamine. It destroys the tubulin protein structure of the neuron and also inhibits the production of neruotransmitters.  

Immunologic Effects - The immune reaction in humans to mercury exposure is varied. There can be increased activity of the immune system leading to an activated system with the development of autoimmunity or sensitivities to the environment.  Another manifestation could be immune suppression with decreases in immune defenses.  In a mercury producing plant it was found that workers had deficiencies in the production of cellular components of the immune system. There have been tens of thousands people who have reported finding high levels of mercury in their bodies and experiencing a variety of problems like: fatigue, dizziness, insomnia, frequency of urination, headaches, chronic skin problems, metallic taste, gastrointestinal problems, asthma, allergic upper respiratory problems, ear ringing, hearing loss, chest pain, hyperventilation, spacey feeling, immune and autoimmune diseases, cardiovascular and chronic neurological problems.  

From animal studies it has been shown that mercury damages T cells.  This happens by the generation of free radicals, by depleting the thiol reserves, damaging the mitochondria, causing destruction of cytoplasmic organelles, a loss of membrane integrity, an inhibition of the ability to secrete IL-1 and IL-2, and by inactivating or inhibiting enzyme systems involving the sulfhydryl protein groups.  Once there is depletion of thiol protection there is a clear set up for T cell apoptosis (death) and adverse effects of the production of other cellular components of the immune defense system. Exposure of genetically susceptible mice to mercury resulted in an autoimmune response similar to that seen in mice that were injected with mercuric chloride. The syndrome included a general stimulation of the immune system, hyperimmunoglobulenemia, anti-nuclear antibodies, glomerular disease with immune complex formation. The production of interferon was also suppressed in mercury toxic animals.  

Mercury induced autoimmunity in animals and humans has been found to be associated with the expression of major histocompatability complex (MHC class 2 genes).  There is also a reduction in B cell formation.  It is interesting that the changes in immune function do not take massive levels of mercury to cause the changes in the immune system. All types of cells showed a dose dependent reduction in glutathione levels when exposed to mercury.  Mercury from amalgams has been shown to interfere with the production of cytokines, disabling early control of viruses and leading to enhanced infection. Mercury by its effect of weakening of the immune system has show that it contributes to the increased incidence of chronic diseases including cancer.  Accompanying the increases in mercury burden there are decreased levels of zinc, and methionine availability, as well as depressed rates of methylation, which is very important in the healing of damaged DNA. There are increased productions of free radicals.  All of the previous findings lead to an increase in the susceptibility to cancer.  In addition to the above, mercury interferes with the cytochrome oxidase system and thus blocking the energy production system.  These changes lead to the production of fatigue and reduced energy.

Of 50 patients who had chronic fatigue and were referred for mercury sensitivity testing there was a 70% positive response. Mercury has also been found to impair the conversion of thyroid T-4 to the active T-3 hormone.  In addition, it has been linked to the development of autoimmune thyroiditis.  In general, immune activation from toxics like mercury results in cytokine release and the dysfunction of the hypothalamic-pituitary-adrenal axis.  This can lead to the development of profound fatigue, musculoskeletal pain, sleep disturbance, gastrointestinal problems (like Crohn's disease, IBS), neurological problems, fibromyalgia, and autoimmune thyroiditis.  There is a definite genetic predisposition to these problems in those with an associated mercury burden. Mercury was found in the cerebrospinal fluid of multiple sclerosis (MS) patients, at levels eight times higher than in the neurologically healthy controls, according to one scientific study. When the mercury is detoxified from the body, many people regain their muscle control and strength.  

Renal Effects (Kidney) - Both acute renal failure and chronic kidney disease has been found to be related to mercury toxicity.  An increase in the incidence of kidney disease has been observed over the last 20 years. Various toxins contribute to the renal injury including chemicals, lead and mercury.  The kidney eventually becomes one of the most important sites for the accumulation of mercury. Utilizing a whole body scanner and tissue analysis a radioactive tracer of mercury was used to follow the mercury from the amalgams to the tissues of the body. The kidneys were one of the first organs to demonstrate accumulation and localization of mercury at first in sheep and then in primates. Subsequent research has demonstrated that pregnant sheep accumulate mercury in the material and fetal tissues. This occurred in a matter of a few days in a time dependent, progressive manner. The National Institute of Occupational Safety and Health document states: Kidney damage may result from excessive exposure to mercury as manifested by the nephrotic syndrome (edema, proteinuria, abnormal cells urine). Such damage may be occult and slow to develop over time and may not show up with elevated levels of mercury in the urine unless one does a challenge test.  

The WHO also has stated that there is no level of mercury that is safe. In other words there is no "lowest observed adverse effect level" (LOAEL) for mercury. There is also evidence that there is a reduced blood flow to the glomerulus of the kidney in patients with mercury burdens. Another major route of renal injury is the immunotoxic effect of mercury, which has been shown to cause an autoimmune type of glomerulonephritis.  The dosage of mercury reported to lead to an autoimmune process is about one-tenth of the nephrotoxic dose. The information included in the government's Material Safety Data Sheets show that chronic exposure to mercury vapor can lead to proteinuria, albuminuria, and other signs of renal injury.  Another important issue concerning nephropathy relates to the depletion of glutathione and other antioxidants.  Since mercury is a potent initiator of free radicals there is a secondary inhibition of various enzymes that are normally protective against renal injury. The potentiation of oxidant stress becomes a very real problem both for the kidney tissue and many other organ systems in the body.

1. Jones DW. The enigma of amalgam in dentistry.  British Dental Journal 1994; 177: 159-70.

2. Vimy MJ, Lorscheider FL. Intra-oral air mercury released from dental amalgam. J Dent Res 1985; 64: 1069-781.

3. Ferstner HB, Huff JE. Clinical toxicology of mercury. J Toxicol Envir Hlth. 1977; 2: 491-526

4. Sugita M. The biological half-time of heavy metals.  The presence of a third "slowest" component. Int Arch Occup Environ Hlth 1978; 41: 25-40.

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