Information » Health Risks » Mercury
The Ancient Greeks called it hydrargyros, meaning silver water. It comes from cinnabar, an elemental part of the Earth’s crust that was used to adorn the tombs of Egyptian Pharaohs in 2000 B.C. – and in cave paintings for thousands of years before that. The healing traditions of India and China used it as a potent medicine for infections, skin wounds and many other illnesses. The idea that mercury could be dangerous is relatively new.
Mercury is indeed dangerous. All scientists agree that it is one of the most toxic metals in the modern world. It is unequivocally related to heart disease, fetal development and overall mortality. But some aspects of the mercury issue are still being hotly debated. One of these is the risk of mercury exposure from dental amalgam fillings. Another is the link between mercury and certain problems of the nervous system, such as autism and attention deficit disorder, Parkinson’s and Alzheimer’s disease and multiple sclerosis.
Although the link between amalgam, mercury toxicity and disease is still controversial, the evidence of harm is growing. If you are considering pregnancy, if you are exploring detoxification of your body or if you feel you are at risk of brain problems, you should consider mercury testing and detoxification. This is particularly important if you have symptoms of mercury toxicity, such as ‘brain fog’, irritable mood, memory problems, anxiety or depression, hand tremors, muscle cramps or twitching, ringing ears or dizziness,
There has been concern about amalgam fillings since they were introduced in 1830. In the 19th century, the American Society of Dental Surgeons asked its members to take an oath that they would never use amalgam. Although this is obviously no longer the case, the Swedish Dental Material Commission recently recommended that they be banned.1
The ‘silver’ used for dental fillings is 50% elemental mercury, and an average filling contains half a gram of it, enough to make a one-acre lake too toxic for human use. Research shows that this mercury finds its way into the body, by contaminating the air we breathe.
Amalgam fillings release small amounts of mercury vapor into the mouth. This vapor is inhaled into the lungs, where eighty percent of it enters the bloodstream. An enzyme named catalase quickly alters the mercury so that it can bind to the hemoglobin in red blood cells. These cells carry it to the kidney, where it can take months to be eliminated. If there is too much mercury in the bloodstream for catalase to handle, it can find its way into the brain, where it remains for up to 20 years.
The exact amount of mercury vapor that is released is important to know, but research estimates vary greatly. Some studies have found minimal vapor release, but others suggest it is much higher – more vapor is released when chewing, or with exposure to hot foods or liquids. Someone with several fillings may be exposed to over 100 micrograms per day.2 This is considered a toxic exposure, and it takes place every single day.
There is evidence that people with fillings have much higher levels of mercury in their hair and urine.3 In one review, five of seven studies found that women with more amalgam fillings have higher mercury levels in their breast milk.4 Allthough most of the research on mercury has been measuring it incorrectly (see below), one US study properly measured total body levels. When compared to non-dental subjects, mercury levels were six times higher in dentists and fifteen times higher in dental hygienists.5
Heart researchers agree that the answer to this question is a resounding yes. This has been blamed on methylmercury, a highly toxic form of mercury that comes from fish. In one study published in the New England Journal of Medicine, researchers compared toenail clippings of 684 men who had suffered a heart attack with those of 724 healthy controls. High mercury levels were 2.16 times more common in heart attack patients.6 Another study of 1871 Finnish men found that those with the highest mercury levels were 60% more likely to have a heart attack and 38% more likely to die of any cause.7
The risk of mercury to the brain is still a bit unclear, but the evidence is growing. The largest study of multiple sclerosis was based on the medical and dental records of 20,000 members of the New Zealand Defence Force over a twenty-year period. Mercury fillings increased the risk of developing MS by 24% for every ‘100 amalgam surface-years’. This translated into a 400% increased risk of MS for the average person with fillings, as compared to those without fillings.8
The link between mercury and Parkinson’s has been suspected because they both cause a fine tremor of the hands. The tremor was seen in the 19th century in workers who made felt hats using a process that exposed them to mercury. These people had many other brain problems, which led to the expression ‘mad as a hatter’. The largest population study of mercury and Parkinson’s disease involved 380 Germans with the disease who were compared with 775 people living in the same neighborhood who did not have the disease. The people with Parkinson’s had an average of 7.8 fillings, and those without it had 6.3. The likelihood that this was a coincidence was calculated to be one in a million.9
The link between autism and thimerosal, a mercury-based preservative in vaccines, generated a lot of controversy in the 1990s. Some studies found that there was a link, while others did not. To end the debate, thimerosal was removed from all vaccines except for hepatitis B.
Some studies have been done to see if people with fillings had subtle changes in personality or brain function. Most have shown no additional risk from fillings, but their findings are very questionable because the methods used to measure these changes were very crude. Some even included elderly toothless people in the no-filling group, even though these people likely had fillings before their teeth fell out.
The scientific research on mercury toxicity is mostly flawed for two other important reasons. The first is that researchers have been measuring mercury levels in the blood, urine or hair. These are excellent for an acute poisoning – like a child who is found playing with a broken thermometer, for example. They are not very good at evaluating chronic toxicity, because they only reflect mercury exposure over the previous 2-3 months.
The best way to estimate mercury in the body in clinical medicine is to give an intravenous dose of 2,3-dimercaptopropane-1-sulfonic acid (DMPS), which chelates (binds) mercury in tissues. The DMPS-mercury complex is excreted in the urine, where it is measured. This is how we test for toxic metals in our clinic.
The second reason that the research is flawed is the recent discovery that some people are more vulnerable to mercury than others. There are two different genetic traits that make this so. One makes a protein called apolipoprotein E, which is found in tubulin, the scaffolding that provides structure to brain cells. When mercury is given to mice, it causes clumping of tubulin, leading to the same neurofibrillary tangles found in Alzheimer’s disease.
It is possible to find out if you are at risk with a genetic test that is available through commercial laboratories. The normal versions of apolipoprotein E are called apoE2 and apoE3. If you have the apoE4 gene, you are at increased risk of Alzheimer’s, and research suggests that this is mediated by mercury.
The other genetic factor is called coproporphyrin oxidase or CPOX4, and it is involved in excretion of mercury in the urine. The process is complicated, but it may explain the accumulating evidence that some people simply cannot get rid of the mercury they are exposed to.
One important study examined the hair from autistic children’s first haircut in the United Kingdom. Parents often keep this hair as a memento, so researchers measured the mercury levels in 94 autistic children and compared them with first haircut samples from 45 healthy children. The autistic children had mercury levels of 0.47 parts per million (ppm), and the healthy children had mercury levels of 3.63 ppm.10 This is one of several studies suggesting that these people are not exposed to more mercury – but more of it gets into the brain because less is eliminated in other tissues.
Before considering mercury detoxification in the body, it is important to eliminate the source – your mercury fillings. This should be done by someone with specialized training and protective equipment. If not, you may be exposed to toxic levels of mercury during the procedure. It is important to know that these fillings are replaced with composite plastics, which may be associated with an increase in long-term cancer risk. Very few materials are completely risk-free.
Removing mercury from the body begins with intravenous DMPS. This substance has been used to treat acute mercury poisoning around the world for over 20 years, and has been found to be safe and effective. It will remove the bulk of the mercury in tissue – mostly from the kidney. The next step is oral treatment with DMSA, another drug that works in a similar way. This is done in a series of cycles to get the best results without side-effects.
The way that mercury poisons the body is by locking onto sulfur atoms in enzymes and other important cell structures. For this reason, it has been recommended that you modify your diet to include foods that are rich in sulfur. These include eggs, cabbage, garlic and onions. Chlorella is a green algae that can absorb heavy metals, so it has been recommended by some. Another popular remedy is cilantro; this is safe and nutritious, but its use in mercury toxicity is based on a single case report from a Chinese physician.
This is clearly a complex subject and many questions remain unanswered. The toxicity of mercury is universally accepted, but the risk of the mercury in your mouth is still not definitively proven. It has also not yet been proven that removing mercury can prevent or treat these problems.
After careful consideration of the evidence, we believe that individuals at risk should consider a supervised program of mercury detoxification. Those who reject this idea say that there is not enough proof that this mercury is dangerous. It seems more reasonable, when considering an extremely toxic metal in the mouths of hundreds of millions of people, to ask for more proof that it is safe.