Review of: The Toxicology of Mercury Current Exposures and Clinical Manifestations Thomas W. Clarkson, Ph.D., Laszlo Magos, M.D., and Gary J. Myers, M.D. NEJM, Oct 30, 2003

By B. Windham, DAMS Intl Research Director


The Clarkson, Magos, Myers mercury article in NEJM, Oct 30, 2003 is very poorly done with a lot of inaccuracies, misstatements, poor research. The following provides documentation for some examples of such affecting important issues. Summary fact sheets(with URLs) citing peer-reviewed studies and clinical results are used along with peer-reviewed study references in this regard, because listing all the references here would make this review extremely long. There are over 1000 peer-reviewed studies referenced, supporting the premise of the fact sheets, which are contrary to the statements in the author's paper.

On page 1731 the authors write: "Fish are the main if not the only source of methyl mercury" and

on page 1733 that "among humans, the sole source of exposure to methyl mercury is the consumption of fish and sea mammals."

This is wrong and contrary to published research and clinical experience. People with no exposure to fish or sea mammals can easily be found by test to have significant levels of methyl mercury in the blood, saliva, and brain,. if they have exposure to other forms of mercury. Dental amalgam is documented to be the largest source of mercury in most people who have several amalgam fillings; and other forms of mercury are methylated in the body by bacteria, yeast, and other methyl donors- making amalgam the largest source of methyl mercury in many. There is a lot of documentation in the medical literature :

[ Leistevuo J et al, Dental amalgam fillings and the amount of organic mercury in human saliva. Caries Res 2001 May-Jun;35(3):163-6; &

Sellars WA, Sellars R. Univ. Of Texas Southwestern Medical School "Methyl mercury in dental amalgams in the human mouth", Journal of Nutritional & Environmental Medicine 1996; 6(1): 33-37; & ]


Table 1:

Under mercury vapor they don't point out that dental amalgam is the largest source of mercury vapor in most; and that the studies that they show aren't relevant to this exposure;

[ ]

There is a huge amount of documentation in the medical literature regarding the common adverse health effects from exposure due to dental amalgam that is disregarded by the authors:


including over 60,000 clinical cases of recovery from over 30 chronic conditions after amalgam replacement: documentation at:

The authors don't mention that thimerosal/ethyl mercury are documented to be a major factor in autism, ADHD, eczema, etc. or discuss the evidence - documentation at:


Metal-Metabolism and Autism: Defective Functioning of Metallothionein Protein, Amy Holmes, MD;


The authors state that chelation is not effective for methyl mercury and ethyl mercury poisoning; which is contrary to evidence and experience:

For ethyl mercury:

and extensive other clinical experience and studies from NIH Medline for methyl mercury

along with:

(where many of the studies cited included use of chelation as part of the recovery)

The fact that some people with acute exposures are irreparably harmed doesn't warrant blanket statements that chelation isn't effective in general. Thousands are treated with positive results by doctors throughout the country each year by many variations of what would be called chelation or detoxification. Since the mercury forms: vapor, inorganic, organic are being converted back and forth continuously in the body, one can't neatly split exposure and treatment results between forms- though there are known differences in general effects and mechanisms of actions of the different forms.


page 1732; the authors state wrongly regarding mercury exposure from amalgam that:

"it was realized that the actual inhaled dose was small, due to the small volume of the oral cavity"

This statement is strange since they go on to say dental amalgam is the chief source of exposure to mercury vapor for most. But the fact that the exposure isn't small but rather very large and more than the federal health guideline level is well documented in the medical literature from the many studies of mercury excretion in those with amalgam(some of which they later quote). Perhaps the problem is that these researchers do not have experience diagnosing and treating mercury toxicity and are not aware of what it means to talk of a small exposure in something so extremely toxic as mercury.


And the fact that all sewers and sewer sludge have high(and dangerous levels of mercury) with the largest source being from dental amalgam(dental offices and excretion of those with amalgam into sewers) is also disregarded:


There is a typo in the reference they quote on level of exposure to mercury from amalgam

on page 1732 (should be 5 rather than 8)


On page 1733 the authores state:

"Today's occupational exposures, such as in the dental office are lower and may lead to mild, reversible effect on the kidney or mild cognitive changes and memory loss"

They site only one fairly old reference that didn't focus on this issue(though it was a good review), even though there are hundreds of studies and clinical investigations that document significant neurological, reproductive, cognitive, and immune effects of dental office exposures.

[Richardson(Health Canada) has estimated that about 20% of the population suffers a subclinical impairment of kidney or CNS function related to amalgam mercury.

Mark Richardson, Environmental Health Directorate,Health Canada, Assessment of Mercury Exposure and Risks from Dental Amalgam, 1995, Final Report; & Richardson M, in: Swedish Council for Coordinating and Planning Research, Amalgam and Health, FRN,1999]

There is substantive documentation that those with dental office exposures have exposures and body burdens much higher than than the general population and higher than those patients with amalgam fillings on average, and that in the long term adverse effects are common:

[ ]


On page 1733 they state that "current evidence shows no connection"for a link between chronic mercury exposure and chronic neurological or autoimmune conditions such as Alzheimer's, multiple sclerosis, Parkinson's, etc. In fact there is substantive documentation in the literature that their statement is not true; they don't fully review the literature and clinical experience, which is extensive, and cite only 3 studies which they say agree with their position. The main study they cite, the nun study, is known to have serious methodological flaws including no valid control population or measurements of body burden which caused it to not be published by a scientifically peer reviewed journal. Another study used serum blood mercury level to judge body burden, which is well documented to not be reliable for this purpose. []

None of the studies used reliable measures of body burden, nor did they bother to measure any of the known susceptibility factors such as ability to excrete mercury or immune reactivity, which are documented in the literature to be the major factors in who is adversely affected my mercury exposure. [ and]

The authors didn't bother to review the many hundreds of studies which document the mechanisms by which mercury causes the conditions seen in Alzheimer's, Parkinson's, multiple sclerosis, chronic fatigue, fibromyalgia, lupus, Lou Gehrig's Disease, etc. or the thousands of cases of recovery or significant improvement from these conditions after treatment for mercury toxicity:





other conditions and


Regarding the authors statements on page 1733 discouraging replacement of amalgam fillings, they don't bother to point out that when amalgam fillings are replaced the increased exposure is temporary and limited where properly done(as documented in the literature) and that daily exposure levels are reduced 60 to 90 percent in the long run(as documented in the literature) which has obvious benefits:

[L.Bjorkman et al, "Mercury in Saliva and Feces after Removal of Amalgam Fillings", Toxicology and Applied Pharmacology, 1997, 144(1), p156-62 &

G. Sandborgh-Englund et al, Mercury in biological fluids after amalgam removal. J Dental Res, 1998, 77(4): 615-24;]

or that peer reviewed studies and clinical studies document that thousands have recovered or had significant improvement from serious chronic conditions after amalgam filling replacement.

The authors statement that "there is no clear evidence supporting the removal of amalgams" is obviously wrong and irresponsible, since large numbers of peer-reviewed studies have documented conditions where most who have amalgams replaced recover, and thousands are documented to have recovered from over 30 chronic conditions.


On page 1735 the authors in dealing with prenatal exposure focus attention and limit discussion to methyl mercury. But it is well documented in the literature that adverse developmental effects are more common and occur at lower levels for mercury vapor exposure(as from dental amalgam) than for methyl mercury.


For example it is well documented that prenatal exposure to thimerosal(rhogam shots) and

dental amalgam from mothers are major factors in causation of autism and other children's neurological developmental conditions.

[ A.S. Holmes, M.F. Blaxill and B.E. Haley, Reduced Levels of Mercury in First Baby Haircuts of Autistic Children; International Journal of Toxicology, 2003; &

Metal-Metabolism and Autism: Defective Functioning of Metallothionein Protein, Amy Holmes, MD; & ]



on page 1735 the authors state that "it is reassuring that the only clinical reports of mercury poisoning from fish consumption are those from Japan in the 1950s and 1960s", and "the risk posed by exposure to mercury is currently speculative".

The authors appear to either not be very knowledgeable about the medical literature regarding health effects from mercury or choose for unknown reasons to ignore the overwhelming evidence since there are extensive and well publicized studies and reports as well as Government panel conclusions of adverse effects all over the world from mercury exposure through eating fish and marine mammals that eat fish:

[(a)J.T. Salonen et al, "Intake of mercury from fish and the risk of myocardial infarction and cardiovascular disease in eastern Finnish men", Circulation, 1995; 91(3):645-55; &(

b) Wisconsin Bureau of Public Health, Imported seabass as a source of mercury exposure: a Wisconsin Case Study, Environ Health Perspect 1995, 103(6): 604-6; &

(c) Watanabe KH, Desimone FW, Thiyagarajah A, Hartley WR, Hindrichs AE. Fish tissue quality in the lower Mississippi River and health risks from fish consumption. Sci Total Environ. 2003 Jan 20;302(1-3):109-26.; &

(d) J. Hightower, "Methylmercury Contaminmation in Fish: Human Exposures and Case Reports," Environmental Health Perspectives; Nov 1, 2002; &

(e) A Oskarsson et al, Swedish National Food Administration, Mercury levels in hair from people eating large quantities of Swedish freshwater fish. Food Addit Contam 1990; 7(4):555-62; &

(f) Preventive Medicine February 2002;34:221-225; &

(g) Dickman MD; Leung KM, "Hong Kong subfertility links to mercury in human hair and fish", Sci Total Environ, 1998,214:165-74; &

(h)Mercury and organochlorine exposure from fish consumption in Hong Kong. Chemosphere 1998 Aug;37(5):991-1015; &

(i) Y.Kinjo et al, "Cancer mortality in patients exposed to methyl mercury through fish diet", J Epidemiol, 1996, 6(3):134-8; &

(j) Choy C et al, Seafood consumption linked to infertility, BJOG: An International Journal of Obstetrics & Gynaecology 2002 109:1121-5; & etc. & ( &



On page 1735 the authors quote the Seychelles study as an example of study that found no adverse effects from eating seafood. However they don't point out that it is well documented that the main assumptions in that study were faulty and incorrect. They did not control for other significant mercury and neurotoxic exposures and excluded from the study those who experienced conditions like epilepsy that are known to be often be caused by mercury toxicity and did not control for or take into account known susceptibility factors:

Their main measure of mercury toxicity or exposure was hair level, which is known for those who are affected most by mercury exposure/toxicity to be inversely proportional to body burden and health effects- the opposite from the authors assumptions- and which led to seemingly strange results:

A.S. Holmes, M.F. Blaxill and B.E. Haley, Reduced Levels of Mercury in First Baby Haircuts of Autistic Children; International Journal of Toxicology, 2003, & Baby hair, mercury toxicity and autism. Int J Toxicol. 2004 Jul-Aug;23(4):275-6. Grether J, Croen L, Theis C, Blaxill M, Haley B, Holmes A.


Andrew Hall Cutler, PhD, PE; Amalgam Illness:Diagnosis and Treatment; 1996 ,

More details snipped from which has the references:)

A recent study found that prenatal mercury exposures and susceptibility factors such as ability to excrete mercury appear to be a major factors in those with chronic neurological conditions like autism(86). Infants whose mothers received prenatal Rho D immunoglobulin injections containing mercury thimerosal or whose mother's had high levels of amalgam fillings had a much higher incidence of autism. While the hair test levels of mercury of infants without chronic health conditions like autism were positively correlated with the number of the mother's amalgam fillings, vaccination thimerosal exposure, and mercury from fish, the hair test levels of those with chronic neurological conditions such as autism were much lower than the levels of controls and those with the most severe effects had the lowest hair test levels, even though they had high body mercury levels. This is consistent with past experience of those treating children with autism and other chronic neurological conditions(23). Very low levels of exposure have been found to seriously affect relatively large groups of individuals who are immune sensitive to toxic metals(11,35), or have an inability to detoxify metals due to such as deficient sulfoxidation or metallothionein function(18,36,51) or other inhibited enzymatic processes related to detoxification(15-24,30) or excretion of metals(87). Those with the genetic allele ApoE4 protein in the blood have been found to detox metals poorly and to be much more susceptible to chronic neurological conditions than those with types ApoE2 or E3(87). ]

(Note that while hair test mercury level is not a reliable indicator of mercury body burden or mercury toxicity effects in those susceptible to mercury toxicity effects, the hair test results are useful in indicating those with mercury toxicity(23e). Since mercury toxicity affects cell membrane permeability and essential mineral absorption and cellular balance, a pattern of essential mineral imbalances in those with normal diets is an indicator of mercury toxicity)

Andrew Hall Cutler, PhD, PE; Amalgam Illness:Diagnosis and Treatment; 1996 ,

Amy Holmes, MD, Baton Rouge Autism Treatment Clinic,


The last section of the paper on thimerosal effects is poorly researched.

They state again that "methyl mercury is more potent" than other forms, which is not supported by scientific evidence, as previously seen. All of the forms are extremely toxic and are converted to other forms in the body and no categorical statement can be supported of this nature.

Studies in the previously referenced papers on thimerosal/vaccine effects document that ethyl mercury has toxicity effects of similar magnitude as methyl mercury, and that mercury vapor exposure has developmental effects at lower levels of exposure than methyl mercury. The authors state that since the half life of ethyl mercury in the blood is less than that of methyl mercury, "risks of its damaging either the brain or kidneys would seem remote". However there is no scientific evidence supporting this conclusion and no plausible explanation of why they would think so. Besides the fact that the conclusion of shorter half life in the blood does not imply that body burden is less or decreased, as seen in the previously referenced paper by Haley, Holmes, Blaxill; having a shorter half life in the blood has no proven significance in the degree of developmental damage by a highly toxic neurologic substance. Mercury vapor, which has a far shorter half life in the blood, than the other 2 forms, has the most developmental effects at lower levels of exposure as has been documented here.


Thomas W. Clarkson, Ph.D., Environmental Health Science Center, University of Rochester, Rochester, NY. Research on genetic aspects of nutrition and toxicology supported in part by the Heinz Institute of Nutritional Sciences and CanTox. (J. Amer. Coll. Nutr. 2001;20:119-28) Research on methylmercury and children supported in part by the Electric Power Research Institute. (Environ. Health Perspect. 2000;108:257-63)

Funding for mercury in the Seychelles Islands project provided by the FDA (through

a supplement to the JIFSAN Cooperative Agreement), with the Electric Power Research

Institute funding $486,000, the National Tuna Foundation funding $10,000, and the

National Fisheries Institute funding $5,000. (;

accessed 7/24/03)


published comment on article :


Comments on the article "the toxicology of mercury and its chemical compounds" by Clarkson and Magos (2006). Crit Rev Toxicol. 2007;37(6):537-49; discussion 551-2

Mutter J, Naumann J, Guethlin C.

University Hospital, Institute for Environmental Medicine and Hospital Epidemiology, Freiburg, Germany.

Clarkson and Magos (2006) provide their perspectives on the toxicology of mercury vapor and dental amalgam. As scientists who are involved in preparing a German federal guideline regarding dental amalgam, we welcome additional scientific data on this issue. However, Clarkson and Magos do not present all the relevant studies in their review. The additional data provided here show that: (a) Dental amalgam is the main source of human total mercury body burden, because individuals with amalgam have 2-12 times more mercury in their body tissues compared to individuals without amalgam; (b) there is not necessarily a correlation between mercury levels in blood, urine, or hair and in body tissues, and none of the parameters correlate with severity of symptoms; (c) the half-life of mercury deposits in brain and bone tissues could last from several years to decades, and thus mercury accumulates over time of exposure; (d) mercury, in particular mercury vapor, is known to be the most toxic nonradioactive element, and is toxic even in very low doses, and (e) some studies which conclude that amalgam fillings are safe for human beings have important methodogical flaws. Therefore, they have no value for assessing the safety of amalgam