Mercury makes up about half a gram, i.e.. 500 mg or 500,000 mcg, per ton (about 1000 Kg) of the Earth's crust, mostly as a reddish mercuric sulfide, known as cinnabar. Thus mercury is naturally present in our food, ranging up to 50 ppb in fruits, vegetables and grains, 200 ppb for meats and 600 ppb for fish. This translates as 600 ng (i.e. 0.6 mcg) per gram. When mercury concentrations are higher than this it is certainly due to agricultural chemicals, such as mercury fungicides.
The daily intake of mercury in our food is said to average 12 mcg. This is 40,000 to 100,000 times less than the dose of elemental mercury sufficient to cause acute symptoms, 500 mg, or death, about 1000 mg. And so it is not something that we have to worry about. Or is it? Bio-accumulation is the surprise: even small doses can build up internally over the years until toxic levels are reached. Most authorities now agree that a daily intake of 100 mcg of mercury should not be exceeded. As you will see, many is the day that any of us do exceed that.
Another worry: when poisoning does occur, the effects are so vague and variable that the diagnosis is usually missed! The ancient Chinese mistakenly believed mercury was a key to long life. This cost the lives of several Emperors! But lest we be smug, in our own time large outbreaks of mercury poisoning still can be confusing to our best doctors and health officers as Goodman and Gilman acknowledge in their classic textbook of pharmacology: "with very few exceptions and for numerous reasons, such outbreaks were misdiagnosed for months or even years. Factors in these tragic delays included the insidious onset of the affliction, vagueness of early clinical signs and the medical profession's unfamiliarity with the disease."
That last part is particularly disturbing because the medical profession has had the advantage of scientific observations about mercury since ancient times. The effects of mercury toxicity on industrial workmen, craftsmen and physicians of the day were catalogued by Bernadino Ramazzini in his fascinating book, Diseases of Workers, published in 1713. He described the plight of mercury miners: "within four months they become subject to palsy of the limbs, paralytic, and suffer from vertigo." Goldsmiths, tinsmiths and mirror makers also were afflicted. "Those who make mirrors become palsied and asthmatic from handling mercury."
Nevertheless, mercury compounds have been used as medical therapies since antiquity, particularly as laxatives and diuretics and more recently as antiseptics. Ramazzini referred to mercury in treating scabies and lice infestations as well as being the only cure for intestinal worms. In the 16th Century mercury compounds were a favorite treatment for Syphilis--even though the results were often worse than the original illness. Then in 1572 Nicholas Monardes, a French physician, introduced a new treatment, the herb, sarsaparilla. Though this seemed to work better it fell out of favor, seemingly due to the fact that Monardes also prescribed a month without wine or sexual activity and confined the patient to a warm room.
It was over 200 years later when the British observed that syphilitic Portuguese soldiers treated with sarsaparilla recovered much better and faster than the British, who continued to use mercury. Recent research in China confirms that sarsaparilla actually clears the blood of the spirochete of syphilis in 90 % of acute and 50% of chronic patients.
Why then did mercury compounds remain in use against syphilis well into the 20th Century? Why did mercurous chloride, Calomel, remain a popular laxative until only 30 years ago? In fact, why are a number of mercury salts still in use: mercuric sulfide, cinnabar, in tattooing and mercury nitrate in curing felt for hats.? The literary portrait of the "Mad Hatter" in Alice in Wonderland was drawn from the brain damaged behavior common amongst workers who once were required to chew the felt during manufacture, thus taking in a toxic dose of mercury. While this hazard no longer occurs, mercury salts are still to be found as red and yellow oxides of mercury in paints and in electric batteries. Ammoniated mercury and phenyl mercuric nitrate are still found as antiseptics and preservatives in ointments.
The two most used mercury chloride salts are known as Calomel and Corrosive sublimate. These are not very soluble and only about 10 % absorbs; however they do react with sulfur in the cells and enzymes. The corrosive form causes cell damage and severe irritation to the mucous membranes with burning pain, nausea, vomiting and diarrhea to give notice of exposure. Calomel is less caustic and makes its presence known by causing a watery diarrhea. While these compounds do not enter the brain they can accumulate in the kidney and heart, causing diuresis and irregular heart rhythm.
Elemental mercury, the familiar silvery liquid in thermometers, is much less toxic when ingested because it is almost non-absorbable by mouth. On the other hand almost all of the vapor absorbs if inhaled and this heads directly for the brain! Injury to the lung tissue also occurs because of oxidation once the metal enters the blood. Thus heavy exposure to mercury vapor causes acute irritation, edema, obstruction of the bronchioles and ruptured membranes. Chronic inflammation and asthma can occur in the lung due to mercury deposits even after recovery from the acute symptoms and the ongoing fibrosis can lead to the insidious onset of emphysema decades later!
Organic mercury compounds, particularly methyl mercury, are the most toxic form of mercury because they absorb almost completely from the gut into the blood. Some bacteria are able to "eat" elemental mercury, and inorganic mercury salts and change them into the more dangerous organic methyl and phenyl-mercury forms that are able to pass easily through cell membranes and cross into the central nervous system. Thus the symptoms of methylmercury are due to nerve damage: pain, tingling and numbness of the extremities, clumsiness, shakiness, muscle spasms and emotional over-reactivity. This syndrome can go on to mimic Lou Gehrig's Disease (ALS or amyotrophic lateral sclerosis).
Methylmercury also crosses the placenta in pregnancy and accumulates in the developing fetus so that at birth the infant has mercury a third more concentrated than the mother! Worse yet is the recent discovery by Dr. Ehman and his team at the University of Kentucky that fetal mercury localizes in the Nucleus Basalis of Meynert, which is the specific area of damage in Alzheimer's Disease. This is the largest trace-element imbalance so far observed in the Alzheimer's disease brain and it may be the reason that even low level mercury exposure can cause significant impairment of memory and learning. Might it also act as a time bomb, adding to the effects of other damaging events over a lifetime to culminate in damage to the memory centers of the brain at an early age?
With these dangers in mind it seems incredible that mercury salts have been a traditional part of medical therapy for hundreds of years and are still in use as a diuretic agent according to the 1983 edition of "Harrison's Principles of Internal Medicine." Mercury combines with sulfur-containing enzymes in the kidney, thus defeating the ability of the tubular cells to reabsorb sodium. As the sodium goes on out the kidney it takes water with it--but at risk of damage to the kidney cells.
Closer to home, mercury compounds are still in use as preservatives and bleaching agents in dermatologic and cosmetic lotions, ointments and creams. Organic phenylmercuric nitrate, for example is present at 1:10,000 concentration in Preparation H suppositories (as of 1992, since then the amount of mercury has decreased). Since each suppository weighs about 1 gram, the mercury content is about 100 mcg and this type of organic mercury is almost completely absorbed! While this may not be sufficient to cause acute symptoms, regular use could accumulate enough to reach toxicity, especially if there are other sources of mercury as well.
I recall one of my patients, a very distressed 60 year old woman, who came to me when five years of psychotherapy for anxiety and agarophobia had failed to relieve her symptoms. Dependence on tranquilizers had merely traded off anxiety for depression. Hair analysis found 35 ppm of mercury, the highest level I have seen in 25 years! This was a pubic hair sample so it is unlikely that the mercury was from an external source, such as a preservative in a 'natural' shampoo. However, she had been bleaching the aging spots on her hands and arms with a mercury containing cream for the preceding 8 years and mercury does absorb through the skin. She gradually improved when the cream was discontinued and she followed a high protein diet with methionine to increase mercury excretion. In addition she took extra vitamin C and physiologic minerals, such as magnesium, zinc and manganese, to compete more effectively against mercury in the cells.
Even though the amount of mercury in the bleaching solution was not very great, the excretion of mercury is so slow that over two months is required to remove half of a given load. Thus, continued exposure leads to accumulation and chronic poisoning can occur in the face of relatively low levels of exposure.
Mercury is excreted via both urine and feces, about 90 percent via the bile into the feces. However, reabsorption takes place in the intestine and thus accumulates to higher levels in the body. A digest of horsehair, which is made of keratin, a high sulfur collagen, is a clever antidote. It binds mercury but is itself indigestible and not absorbed. Thus it carries more mercury out with the stools. By combining this therapy with absorbable sulfur substances, such as D-penicillamine or N-Acetyl cysteine, the circulating mercury can be chelated to the sulfur and removed from the tissues.
Here are a couple of other cases of mercury poisoning from the pages of Dr. Jay Arena's text on Poisoning. One tragic death was caused by the use of merthiolate for a month to clear an ear infection. In another instance, mercury vapor from a freshly painted gas heater caused the death of 3 children. Vapor also escapes when marine paint is scraped from boat bottoms, a not infrequent event amongst boat owners. In fact, I identified two of my own patients with neurologic symptoms that way. Dizziness was a prominent symptom in one of the patients and was diagnosed as "vestibulititis" by a consultant, who did not consider the possibility of heavy metal poisoning.
Acrodynia, was a common disease of infants due to the use of Calomel for teething and mercuric bichloride as a diaper rinse from the 1850 period and after. Ammoniated mercury ointment was also associated with a similar rash plus enlargement of spleen and lymph nodes. Acrodynia was still a common illness amongst children, even after 1948 when Drs. Warkany and Hubbard identified the connection to mercury. It was also called "pink disease" because of a distinctive pink rash on fingers, toes, nose, cheeks and buttocks. Recently it has been linked to water-based paint, especially outdoor types, which contains phenyl mercuric propionate to prevent mold and mildew. While this possibility has been known for years, it wasn't until 1991 that the Environmental Protection Agency (EPA) announced a total ban on the use of mercury in house paint after a case of acrodynia in a 5 year old child exposed to fumes in his newly painted room.
This struck home with me personally because 20 years earlier my infant son was poisoned by paint, which he ingested by teething on his favorite toy. The paint in this toy contained 6000 mcg of lead per gram of paint. It was an illegal paint in this country but had made it through customs just the same and this probably still occurs once in a while. My son's life was saved because I made the diagnosis by means of hair analysis when he was scarcely a year old! But I failed to deal with the public health channels, i.e. I didn't report the case because I didn't know then that lead intoxication is a reportable disease. It never came up in my medical school, internship or residency. Our family pediatrician flunked-out even worse, i.e. he denied the diagnosis even in the face of positive results from the tests that I had ordered of blood, hair and the chewed upon yellow paint from one of my son's toys. Of course, he didn't report it either.
It was a classic case of a competent physician caught off guard and whistling in the dark in an unfamiliar situation. This is not unusual in medical practice. For example, it is the rule that doctors assume vitamins and minerals are normal in almost every case and hence laboratory testing of these life-giving substances is put aside. Where nutrition is concerned medical practice operates with eyes closed. And even if the test results indicated low or borderline levels, most doctors have a hard time prescribing specific nutrient therapy. It is still considered controversial, even quackish, a 'no-no' in the medical world.
However the danger of heavy metal poisoning, i.e.. exposure to lead, mercury, arsenic, cadmium and aluminum is universally recognized and there is no longer any excuse for medical incompetence in diagnosing and treating any of these toxic elements, especially since hair analysis makes diagnosis so much easier and less expensive. Nevertheless, the Goodman and Gilman description of the situation still holds true and mercury toxicity is: "misdiagnosed for months or even years (due to) the medical profession's unfamiliarity with the disease."
To be fair, let me say that lead poisoning is now widely recognized as a major public health problem, particularly for children, who are more vulnerable to exposure from paint chips and contaminated dirt and more susceptible to the damaging effects on the nervous system than are adults. Major progress was made in 1974 when Congress passed the Lead Paint Control Act, which legally removed lead from most gasoline and all indoor paints. The results are apparent in my medical practice: hair test results have shown a big drop in lead, from an average range of 15 to 25 ppm in 1980 to 4 to 7 ppm now. Of course, for the best of health one's lead level should be zero so we have a way to go.
Mercury is equally as poisonous as lead and I mistakenly assumed that our public health laws assured that it was not permitted in dangerous amounts. Thus, though I knew about the presence of mercury preservatives in latex paints, I thought that since lead was removed then mercury was also. Wrong! In fact, when lead was removed from indoor paints, the marketplace adjusted by selling more water-based "latex" paints.
That is changed now due to the increased reports of mercury poisoning from paints. These cases have confirmed our previous suspicions about the danger of poisons in general, a by-product of the mushrooming problem of pollution that has spawned a powerful environmental consciousness in all of us.
So we are ready to listen with intelligence when a few research scientists brave the heat of the medical and scientific world to present their findings that dental amalgam, which we have all accepted as safe, is actually the leading cause of mercury poisoning in Western civilization today.
Getting at the truth about mercury is like pulling teeth: the diagnosis comes out easily in the bad cases; but in the milder ones, truth is harder to extract. The potential danger of mercury in silver fillings is a case in point. Fastidious research in Sweden by Dr. Jaro Pleva demonstrates that the amount of mercury that enters our body each day from a mouthful of "silver" amalgam (50 % mercury!) is at least 10 mcg per cm of surface, i.e.a single full surface filling. In a mouth with 12 fillings as much as 200 mcg of mercury is released per day and if there is contact to a gold crown, an additional 250 mcg of mercury is released. Is that worth worrying about? You bet.
to be continued...
© Richard A. Kunin, M.D. 2010