Mercury is a multipotent cytotoxin that intervenes in the primary processes of the cell by bonding strongly with sulfhydryl and selenohydryl groups on albumen molecules in cell membranes, receptors and intracellular signal links, and by modifying the tertiary structure. The structure of albumen molecules is genetically determined, and this leaves ample scope for genetic polymorphism to manifest itself in varying sensitivity and types of reaction to mercury exposure. Mercury is toxic because it induces production of free oxygen radicals and modifies the redox potential of the cell.
Toxicity caused by excessive mercury exposure is now becoming recognized as a widespread environmental problem and is continuing to attract a great deal of public attention. A National Academy of Sciences study published in July, 2001 estimates that up to 60, 000 children born in the USA each year may be affected by mercury toxicity, and in March of 2002 an environmental group had charged the FDA of failing to warn the public of the dangers of mercury contamination from eating tuna, which contain high levels of mercury.
World Health Organization reports that the amount of mercury-absorbed daily by the average human body is 0.3 micrograms (mcg) from water and air, 2.61 mcg from fish, and 17 mcg from dental amalgams (silver fillings). Uptake of up to 100 µg daily has been observed in extreme cases. Research points out that mercury vapor is 80% absorbed into the blood, and that in animal studies, mercury vapor goes directly from the nose to the brain, following nasal nerve pathways. Amalgam fillings release mercury for as long as 70 years. Someone with 8 amalgams could release 120 mcg into the saliva per day.
The maximum allowable by the EPA is less than 0.1 mcg per kilogram of body weight per day, to be absorbed into the human body.
Elemental mercury is found in liquid form, which easily vaporizes at room temperature and is well absorbed through inhalation. Its lipid (fat)-soluble property allows for easy passage through the alveoli into the bloodstream and red blood cells. Once inhaled, elemental mercury is mostly converted to an inorganic divalent or mercuric form by catalase in the red blood cells. This inorganic form has similar properties to organic mercury. Small amounts of non-oxidized elemental mercury continue to persist and account for CNS toxicity. Elemental mercury, as a vapor, which escapes from fillings, penetrates the blood-brain-barrier and enters the CNS, where it’s ionized and trapped, attributing to its significant toxic effects. It is not well absorbed by the GI tract and, when ingested, is only mildly toxic. Inorganic mercury is highly toxic and corrosive and is the most destructive form, but its destruction is limited to where it’s located. It doesn’t have the ability to move through tissues like other forms. It gains access orally or dermally and is absorbed at a rate of 10% of that ingested. It has a nonuniform mode of distribution, secondary to poor fat solubility, and accumulates mostly in the kidney, causing renal damage.
Although poor lipid solubility characteristics limit CNS penetration, slow elimination and chronic exposure allow for significant CNS accumulation of mercuric ions and subsequent toxicity. Chronic dermal exposure to inorganic mercury also may lead to toxicity. Excretion of inorganic mercury, as with organic mercury, is mostly through feces. Renal excretion of mercury is considered insufficient and attributes to its chronic exposure and accumulation within the brain, causing CNS effects. Organic mercury can be found in 3 forms, aryl and short and long chain alkyl compounds. This is 100 times more toxic than the ionic or vapor forms. Bacteria in the mouth, stomach and intestines, or in the blood, through a process called methylation, converts mercury vapor and ionic mercury into deadly methylmercury.
Organic mercurials are absorbed more completely from the GI tract than inorganic salts are; this is because of intrinsic properties, such as lipid solubility and mild corrosiveness (although much less corrosive than inorganic mercury). Once absorbed, the aryl and long chain alkyl compounds are converted to their inorganic forms and possess similar toxic properties to inorganic mercury. The short chain alkyl mercurials are readily absorbed in the GI tract (90-95%) and remain stable in their initial forms. Alkyl organic mercury has high lipid solubility and is distributed uniformly through the body, accumulating in the brain, kidney, liver, hair, and skin. Organic mercurials also cross the blood brain barrier and placenta and penetrate red blood cells, attributing to neurological symptoms, teratogenic effects, and high blood-to-plasma ratios.
Confirmation of the escape of mercury vapor and ions from amalgam dental fillings is provided by The World Health Organization (WHO) Environmental Health Criteria 118 document (EHC 118) on inorganic mercury. It clearly states that the largest estimated average daily intake and retention of mercury and mercury compounds in the general population, is from dental amalgams, not from food or air. Mercury vapor inhaled into the lungs is absorbed almost 100 percent and immediately passes into the bloodstream. It takes approximately four minutes before mercury is converted or oxidized into an ionic state from its elemental vapor state. While in its elemental form, mercury vapor is lipid (fat) soluble and readily passes through the blood-brain barrier or the placental membrane.
It can also accumulate in other organs and tissues of the body. The estimated average daily intake of mercury from dental amalgams is 3.8 – 21 micrograms per day. Two-thirds of the body burden of mercury is derived from the mercury vapor released from amalgams. The static, unstimulated release of mercury vapor from amalgam fillings, which goes on 24 hours a day, 365 days a year, is a major contributor to total mercury body burden. Large amounts of mercury vapor are released during chewing. After only ten minutes of gum chewing, there is an average increase in mercury release of 15.6 times more than during the resting state in test subjects. That converts to a 1,560% increase in mercury release.
“The World Health Organization has calculated that the average human daily dose of mercury from various sources are: Dental amalgam = 3.0-17.0 mg/day (Hg vapor) Fish and Seafood = 2.3 mg/day (methylmercury) Other food = 0.3 mg/day(inorganic Hg) Air & Water = Negligible traces (NOTE mg = Micrograms)” (World Health Organization Figures, from Environmental Health Criteria 118: Inorganic Mercury, Geneva, 1991. These figures confirm Amalgam as #1 average source for Environmental Mercury exposure.)
“You wouldn’t take a leaky thermometer, put it in your mouth, and leave it there 24 hours a day, 365 days a year. Yet that’s exactly what happens when an amalgam filling is installed in your mouth.”–Dr Michael Ziff.
Mercury readily mixes with food and is swallowed with it. The body uptake from inorganic mercury, swallowed with saliva, can be as much as hundreds of micrograms per day for individuals with a large number of amalgam fillings. Urinary excretion is a common indicator of mercury toxicity, even though fecal excretion of mercury is twenty times greater than the corresponding urinary excretion. There is a statistical correlation between the mercury concentration in saliva and the number of amalgam fillings. The United States government has determined and ruled that the continual exposure to mercury from amalgam fillings is not without risk to patients. We are concerned over picograms and micrograms of mercury in apples and are looking the other way when milligrams, one million times more, are being implanted directly into a child’s mouth. There is a phenomenon that occurs in the mouth that can contribute to the release of mercury, and is called corrosion. Corrosion is similar to “rust” and means that surface particles of the filling material are being chemically broken down and released into the oral cavity.
Mercury vapor is released when you chew or grind. Additionally, minute rusted particles of the amalgam are being abraded and taken up by your food or saliva and swallowed. Intestinal enzymes and bacteria both produce methylmercury, an even more toxic form than elemental mercury, may act upon these minute particles of mercury filling. Although several sources contributing to the domestic mercury concentrations have been identified, human wastes (feces and urine) from individuals with dental amalgam fillings are believed to be the most significant source–greater than 80 percent. Conventional amalgam was routinely placed until 1976, when the new state-of-the-art amalgams (50% mercury and 30% copper) were introduced. They emit up to 50 times more mercury than the earlier, conventional amalgam fillings. That means that every new high-copper amalgam filling placed today has the effective toxic equivalent of fifty of the older amalgam fillings. If other fillings are in the mouth, such as gold crowns, nickel crowns, and removable bridges or braces, the mercury emission further increases from the amalgam. This is due to the electrical current generated by the presence of dissimilar metals in an electrolyte such as saliva. Heat will reliably increase the rate of escape of mercury vapor from amalgam fillings. Vapor detectors, held above amalgams, revealed an increase from 3 micrograms to over 500 micrograms ten seconds after a hot drink was swallowed.
“Worldwide there are over 4000 research papers indicating mercury is a highly toxic substance. How can dentists be so thoughtless as to place one of the deadliest toxins in existence *two* inches from our brain?”–Tom Warren
“The mercury uptake from amalgam is the dominating source for inorganic mercury in the central nervous system and is the major source of total mercury uptake in the population.”–Maths Berlin, a leading Swedish toxicologist