Dubious Mercury Testing

Robert Baratz, M.D., D.D.S., Ph.D.

Mercury is found in the earth's crust and is ubiquitous in the environment. Thus, even without amalgam fillings, everyone has small but measurable blood and urine levels. Amalgam fillings raise these levels slightly, but this has no clinical significance.

The legal limit of safe mercury exposure for industrial workers is 50 micrograms per cubic meter of air for 8 hours per day and 50 weeks per year. Exposure at this level will produce urine mercury levels of about 135 micrograms per liter. These levels are much higher than those in the general public but produce no symptoms and are considered safe.

Most people without fillings have a maximum of 5-10 micrograms per liter of urine. Most practicing dentists have levels below 10 micrograms per liter, even though they are exposed to mercury vapor when placing or removing amalgam filings and typically have amalgams in their own teeth. Thus, even with that exposure, the maximum levels found in dentists are only twice those of their patients—and most dentists are have the same levels as most patients. These are far below the levels known to affect health, even in a minor way.

Despite these facts, small percentages of dentists, physicians, and chiropractors are advising patients to have their amalgam fillings replaced with other materials. Their advice is typically accompanied by one or more tests that are either misinterpreted or completely bogus. These activities are the hallmarks of a scam.

Breath Testing

Breath testing is done by asking the patient to chew gum vigorously for several minutes and then probing the mouth with an industrial mercury detector. These instruments measure changes in electrical conductivity caused by absorption of mercury or other metals onto a gold foil film. In the hands of anti-amalgam dentists, several factors combine to produce falsely high readings.

Urine Testing

Because mercury is ubiquitous, the body reaches a steady state in which tiny amounts are absorbed and excreted. Thus, it is common to find mercury in people's urine. Mercury can also be found in the blood, because this is the major medium for transporting materials around the body. Large-scale population studies have shown that the general population has urine-mercury levels below 10 micrograms/liter. Industrial workers, and dentists, who have regular exposure to mercury vapor also have low values. Because urine-mercury levels represent the chronic, steady state, exposure to the body of mercury, they are fairly reliable indicators of past exposure, since they tend to even out the peaks and valleys of transient rises and falls in the blood level. Urine measurements should be performed on the first urine specimen of the day, which would be the most concentrated, or (preferably) on a 24-hour urine specimen.

Urine mercury levels can be artificially raised by administering a mercury scavenger (chelating agent) such as DMPS or DMSA, which collect the small amounts of mercury from the body, concentrate them, and then force them to be excreted. In other words, mercury that normally recirculates within the body is now bound and excreted. The urine level under such circumstances is artificially raised above the steady-state level. A study of urine mercury levels in people given DMSA or a placebo has found no association between the mercury levels and the number of dental amalgam surfaces [1]. The use of a chelating agent before testing—"provoked testing"—should be considered a scam. Anyone told that a urine-mercury level produced after taking DMPS represents a toxic state is being misled.

In February 2005, the State of Connecticut obtained a consent order barring psychiatrist Robban Sica, M.D., from using provoked testing to diagnose "heavy metal toxicity." [2] It would be good if all state licensing boards did the same.

Blood Testing

Mercury is excreted by the kidneys, which filter the blood. The mercury levels of blood are lower than those of urine and therefore more difficult to detect. For this reason, blood testing for mercury is not commonly done. Even at high levels of mercury exposure, industrial workers show blood concentrations in the parts-per-billion range, typically less than 5 parts per billion. These are close to the limits of detection. In this range, the amounts are too small to identify the type of mercury or its source. Urine mercury testing gives a more meaningful picture of exposure and is also more accurate because the mercury is more concentrated.

Skin Testing

Skin testing for allergies is both an art and a science. Correct concentrations of a suspected offender must be correctly applied and interpreted. To be valid, patch testing must be done by a qualified tester using appropriate controls. Mercury patch testing is usually done with corrosive mercury salts that cause the skin to redden and possibly swell. Even very dilute concentrations can cause redness [2]. Anti-amalgamists misinterpret these signs of irritation as allergy or toxicity. So-called "positive" tests indicate only that the body can detect the substance. True allergy to mercury is very rare. Its symptoms are like those of any other allergy and include itching, rashes, and swelling. Allergic responses do not include "brain fog," forgetfulness, or other nonspecific symptoms. Moreover, sensitivity to mercury might be the result of exposure to mercury from other sources, such as certain vaccine preparations, preservatives in cosmetics, or foods (most notably fish).

Stool Testing

No stool test for mercury has been standardized. Fecal mercury levels are not an accurate indicator of mercury exposure. The amount found in stool reflects the amount eaten and not absorbed plus anything excreted in the stool. Stool patterns (frequency, consistency, volume, and density) vary widely from person to person, and thus, the amount of mercury found in stool would be very hard to translate into to body burden, body stores, or excretion. Only about 5-10% of ionic mercury (the kind associated with most alleged poisonings) is absorbed from the gut. The main route of mercury excretion is through the kidneys into the urine, and not into the stool. Further, to make an analysis, ionic mercury must be separated from any organic mercury that occurs in foods, which is difficult to do. Thus, at best, a stool test might indicate that mercury entered the gastrointestinal tract, but it could not provide an accurate measurement of either exposure or what was absorbed into the body.

Hair Analysis

Hair mercury levels are not an accurate indicator of mercury exposure. Hair testing has never been standardized to provide meaningful information. In fact, it cannot be standardized because:

Thus it should be obvious that analyzing hair for mercury is a waste of time and money and cannot be used to diagnose mercury poisoning. A competent practitioner would easily know this. It is fraudulent to use hair analysis to diagnose "toxic levels" of mercury (or any other heavy metal) or to assess nutritional status (and claim someone is "deficient" and prescribe or sell them supplements). Dr. Stephen Barrett calls commercial hair analysis "the cardinal sign of quackery." [2]

Saliva Testing

Larry Clapp, a nonpracticing attorney who "coaches" people on how to deal with prostate cancer, prostate problems, and erectile problems, recommends that amalgam fillings be removed as part of his treatment system. In 2002 and 2003, he promoted an Immune Antibody Test," a saliva test that he claimed would help guide "detoxification" after the removal of the fillings. During that period, his mercurytestkits.com Web site claimed that the test measured antibodies created by the immune system to deal with mercury in the tissues and that high readings were associated with serious illness. I am not aware of any such processes. The Web site site that advertised the test is no longer posted; and the lab that was doing it no longer offers it.

Electrodermal Testing

Some practitioners use quack diagnostic devices that are said to detect "electromagnetic imbalances." One wire from the device goes to a brass cylinder covered by moist gauze, which the patient holds in one hand. A second wire is connected to a probe, which the operator touches to various points inside the mouth. This completes a low-voltage circuit, and the device registers the flow of current, which the operator misinterprets as abnormal.


  1. Frumkin H. Diagnostic chelation challenge with DMSA: A biomarker of long-term mercury exposure? Environmental Health Perspectives 109:167-171, 2001
  2. Consent agreement. In re: Robban Sica, M.D.. Petition No. 2002-0306-001-043, Feb 2005.
  3. Barrett S. Commercial hair analysis: A cardinal sign of quackery. Quackwatch, Jan 5, 2001.

Dr. Baratz, who practices in Braintree, Massachusetts. has extensive training and practical experience in internal medicine, emergency medicine, oral medicine, dentistry, material science, and research methodology. He also serves as a medical and dental consultant to many state licensing boards, federal agencies, insurance companies, and the legal profession.

This article was revised on February 19, 2005.

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