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There are different types of mercury, depending on the structure of the mercury molecule. Every type has its different properties and is therefore utilized in different ways in dentistry, medicine and industries. Interestingly enough, allergy to mercury is specific, meaning that an individual can be allergic to one specific type of mercury and not another. This is because the cells involved in the so called Type IV allergic reaction, the memory cells, depend on the exact structure of the molecule to be activated. Naturally, it is possible that an individual can be allergic to all four types of mercury. In many cases it is important to locate the source of exposure that causes and inflammation in the body due to mercury allergy, so exposure can be stopped. The MELISA test can differentiate between allergy to four types of mercury.
The main distinction is between organic mercury and inorganic mercury. The former is more toxic as it easily passes through the blood-brain barrier, which protects the brain from toxins.
Inorganic mercury, or 'metallic mercury', is a frequent source of metal allergy. Although extremely toxic in its own right, it makes 50% of dental amalgam fillings. Dental authorities accept that mercury vapour constantly evaporates from the fillings, but argue this is below a safe limit. However, for hypersensitive patients, there is no safe limit. Replacing amalgam fillings to ceramic substances has delivered radical improvements in patients who tested MELISA®-positive for mercury. In the body, bacteria can transform inorganic mercury into the organic form methylmercury.
Methylmercury is found naturally in fish which is why doctors advise pregnant women to avoid excessive amounts of fish to avoid exposing the baby. Infants and children are also at high risk from methylmercury-contaminated fish and breast milk contaminated by the mother. Like all forms of mercury, it is exceptionally toxic. It survives up the food chain, so the large fish at the top of the food chain such as shark, swordfish, and large mouth bass have the highest concentrations. It is distributed evenly across fish, and is not affected by cooking. This form of mercury is also found in contaminated soil and grain. Bacteria in the body can transform inorganic mercury into methylmercury.
Phenylmercury is the organic mercury most commonly found in dental root fillings. While it has been phased out in many countries, it is also used as a preservative in eye drops and nose drops. It is less toxic than methylmercury and ethylmercury, because it is rapidly metabolised. Phenylmercury is used to control the growth of fungus in some interior latex paints manufactured before 1991, some exterior and oil base paints, some caulks, some eye-area cosmetics, toiletries, and other products. When these products are used, mercury metal vapour gets into the air and can be inhaled.
Ethylmercury is a form of organic mercury. It is used in Thimerosal, a controversial substance used as a preservative in vaccines, eye drops and nasal sprays. Highly toxic in its own right, it is administered frequently to infants in countries such as the UK, where it is in the triple Diptheria, Typhoid and Pertussis (whooping cough) vaccine. The DTP jab used in the UK, for example, has enough thimerosal to deliver 25 micrograms of ethyl mercury in every shot of vaccine. It is also present in many flu vaccinations.
Thimerosal is one of the most controversial substances is modern medicine. Its main component is ethyl mercury (49.6% by weight), yet it is still used as a preservative in many child vaccines, flu vaccines and other health substances such as eye drops and contact lens solution. It is slowly being withdrawn from vaccines in some countries. It is the subject of a $3 billion lawsuit in the US filed by parents of autistic children who believe it to be responsible for neurologically harming their child. Its use is defended on the ground that the mercury amount is too small to pose danger. But to those who are hypersensitive, even trace amounts can be dangerous.
Full body autoradiography
To demonstrate that mercury binds to the body proteins, we can use a special form of mercury whose distribution in various organs of the body can be traced by sensitive photographic emulsion. Below are four pictures of mice, which were injected with mercury which was labeled with a radioactive isotope. Then, using autoradiography, a special picture is produced. The areas where the mercury was deposited are shown in white.
The pictures demonstrate widespread distribution of mercury in the body of the mice. Organs rich in fat - such as brain and collagen - are very prone to mercury binding. One of the reasons for this is that mercury is particularly keen to bind to two amino acids; methionine and cysteine. Both amino acids contain sulphur hydrogen (SH)-groups. This is a particularly attractive target for mercury. Fat tissues and collagen tissues are rich in SH-groups.
Figure 1. Distribution of radioactivity in male mouse 6 hours after intravenous injection of 203HgCl2. Magnification 2x.
Figure 2. Distribution of radioactivity in male mouse 24 hours after intravenous injection of 203HgCl2. Magnification 2x.
Figure 3 and 4. Distribution of radioactivity in male mouse 2 days after intravenous injection of 203HgCl2. Magnification 2x and 9x (right).
Pictures are from "Explorative study of tissue distribution of 203Hg2+ in mouse after oral administration of some chelating substances with and without vitamin C", by Anette Seo, Safety Assessment, Astra AB, Södertälje and Institute for Pharmaceutic Bioscience, Department of Toxicology, Uppsala University, 1994. Thanks to Dr Anette Seo for permission use the material.
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