Comments on Children’s Amalgam Study one:

"Neurological and Renal Effects of Dental Amalgam in Children", D.C. Bellinger et al, JAMA, April 10, 2006


Comments compiled by the IAOMT dental association pointed out that these studies were flawed in a myriad of ways, both scientifically and ethically.  In the attached articles, Sandy Duffy, JD, finds that the process of informed consent in both studies fell far below recognized ethical standards.  Boyd Haley , PhD Chemist, finds major scientific flaws in the study designs and conclusions, which was also supported by other comments.  An editorial by Herbert Needleman, MD, cautioning readers not to draw "unwarranted conclusions from these limited studies," was published in the JAMA along with the two articles and Dr. Gianpaulo Guzzi wrote a letter following up a significant problem with the study noted by one of the study athors.   There have been thousands of peer-review studies that document that mercury from amalgam is the largest source of mercury in most people who have amalgam fillings and commonly causes adverse health conditions.


Further comments by B. Windham, Research Director and President,   DAMS, Intl.


The study design was not a serious effort to determine amalgam safety. The study was an unethical use of a known highly toxic substance on children who were not fully informed or in a position to understand the implications.  But the author’s interpretation of results is also questionable. The Chief of the Harvard School of Dental Medicine, Dr. Ng, noted that a major flaw in the study design was that only older, healthy kids could participate (14), and the study was for a limited time, not measuring long term effects that are documented in the medical literature to occur commonly.


It is known from thousands of studies and millions of tests by medical labs that those with amalgam get significantly higher mercury exposure than those without, that mercury accumulates in the brain and major organs proportionately to the number of amalgam fillings, and commonly causes chronic degenerative neurological conditions later in life.

Thus the ethics in the exposure to a group of children to higher levels of a very neurotoxic substance such as mercury is highly questionable.


This study was not a serious test of the safety of amalgam since the exposure was to children with no previous amalgam fillings at relatively low levels of exposure for a very limited period of time.  The mean number of restored amalgam surfaces in the mouth of the amalgam group at the end of the study was only 4 amalgam surfaces.   And while the urine mercury level in the amalgam group was 50% higher than the non-amalgam group, this is a much lower differential than most studies of groups or either children or adults with and without amalgams.


However, even with the low exposure levels, it is not clear from the study results that there were no significant adverse effects of amalgam shown as claimed by the authors.


For example, it is well documented that mercury from amalgam commonly causes chronic neurological conditions in adults.    So it might be useful to compare diagnosed neurological conditions between amalgam and non-amalgam group.   The comparison is as follows:


Condition                      amalgam group     non-amalgam group    percent difference

migraines                              18                        14                           28.5%

neurological illness                   4                          1                         300%

psychological disorders           24                        18                           33%

sensory disorders                   36                        28                          28.5%


Total                                     82                        51                           60%


Amalgam is also known to cause respiratory problems- the study found the following

Asthma                                19                         17                         13%

Respiratory disorders          13                          7                          86%


Total                                    32                         24                         33%


Similarly while the authors state that there were no significant renal effects observed,  it could be noted that

the unadjusted mean albumin level at year 5 for the amalgam group was 38% higher than for the non-amalgam group.   I would be very concerned about the future of some at the high end of the amalgam group albumin levels.


Children’s Amalgam Study 2:

Preliminary Comments on   “Neurobehavioral Effects of Dental Amalgam in Children”,   T. A. De Rouen, et al,   JAMA, April 19, 2006


In justifying the study design the author’s state on page 1 that “there is little or no evidence concerning health effects of low level mercury exposure from amalgam, especially in children”.   In fact, there are over 3,000 peer-reviewed studies in the medical literature(3) that were submitted by parties in the FDA amalgam docket to the FDA (4), that document the mechanisms by which mercury(from amalgam) commonly causes over 30 chronic health conditions.  And there are hundreds are peer-reviewed studies and clinical studies that document that many thousands of patients with  these conditions have improved after amalgam replacement(2). While it is clear that hundreds of thousands (or millions) of children have had their health adversely affected by mercury, since there are multiple exposure mechanisms it’s not clear the extent to which dental amalgam is responsible (7).


But the main problem with the study design appears to be the choice of what conditions were tested for and the kinds of tests that were used.   In describing why the chosen conditions were tested for and in what manner, the authors stated on page 2 of the study that the target organs for elemental mercury exposure from amalgam were identified to be the renal system and neurological functions(memory, attention/concentration, and motor/visuomotor).  Actually, while there is documentation in the medical literature of many other types of health effects, there is little evidence in the literature on common renal effects.(1,2,3). And there are other types of health effects that have been well documented in the literature to be more commonly caused by mercury than attention or memory(though these also have been documented to be commonly caused by mercury exposure).


The following analysis shows that the basic assumptions that the authors say they based their study design on were not valid, and the study does not demonstrate what it has been suggested to demonstrate.  In fact, due to the poor study design the study is not very useful.  It had been documented by millions of medical lab tests that those with amalgam fillings commonly have mercury exposures between 5 and 10 times that of the average person with no amalgams (5), and that mercury accumulates in the brain and major organs in direct proportion to the number of amalgam surfaces.  It has likewise been documented in the medical literature by thousands of studies that mercury and other toxic metals exposures are synergistic and cumulative, and commonly cause chronic autoimmune, neurological, hormonal, and reproductive problems later in life(3), depending on individual susceptibility(6). As Dr. Ng. testified at the FDA hearing(14), this study design deliberately excluded a group more susceptible to effects.

Thus it was clear that the study design exposing children to a known highly neurotoxic and immunotoxic substance that commonly causes adverse effects was highly unethical.  And also, the effects that might happen in the early years of exposure has little relevance to whether amalgam is safe as a filling material.  The study was not designed to determine anything about the long term health or safety effects on this population of children.  Or even on the most common types of conditions known to be commonly caused by dental amalgam or the types of cardiovascular effects found in a similar test of children from the Faeroe Islands.


Questionnaire results of 1569 patients (1) regarding health problems that have been documented to be commonly caused by mercury toxicity found the following distribution:


Condition                    % with Condition          %  improved after Amalgam Replacement


Fatigue/lack of energy (12)    51%                                        86%

Headaches/migraines (8)      37%                                         87%

Allergy/skin conditions (10)  34%                                        84%

Vision Problems                    29%                                        63%

Cardiovascular problems(9)   27%                                        70% 

(tachycardia/irregular heartbeat/

  high blood pressure/chest pain)

Depression/anxiety    (11)    27%                                        90%

Dizzyness(could be cardio)   22%                                        88%

Oral conditions         (13)     20%                                        85%

ADD/lack of concentration    17%                                        80%

Memory Loss            (8)       17%                                        73%

MS/Parkinson’s/tremor  (10) 15%                                        78%


Similar patterns and recovery results after amalgam filling replacement have also been documented in a larger group of over 60,000 patients(2).   Thousands of peer-reviewed studies documenting the mechanism by which mercury commonly causes these conditions are in the literature(3).   It is seen that there are 8 major types of health conditions known to be caused by mercury that are more commonly seen in the population than the  types of conditions that these studies chose to attempt to test for.


And in all of those types of conditions, peer-reviewed studies and clinical studies have found that the majority of those who had amalgam fillings replaced properly had health improvement after replacement.    There are few studies documenting significant renal effects from dental amalgam exposure, so it’s not clear why the authors chose to test for renal effects.  There is some question as to what the study being reviewed actually measured regarding neurological effects, since other studies have documented that mercury from amalgam and other toxic metals commonly cause ADD/attention deficit(7), as well as memory problems(perhaps more later in life)(8) and that the majority with such conditions usually improve after amalgam replacement.

        It should also be noted that since the effects of toxic exposures are known to be synergistic and cumulative, the results of a study in one country or population do not necessarily apply to another country or population- that has significantly different patterns of toxic exposures, such as the extremely high mercury thimerosal exposures to children in the U.S. in the 1990s which are documented to have significantly impacted that population(7).


(1)  Patterns of chronic conditions in 1569 patients and percent recovery after amalgam filling replacement,

(2) Results of amalgam filling replacement in over 60,000 patients monitored by peer-reviewed or clinical studies,

(3) Mechanisms by which mercury(from dental amalgam) commonly causes over 30 chronic health conditions (over 4,000 peer-reviewed & Gov’t studies cited),

(4) Listing and abstracts and compilation of medical studies submitted to the FDA dental amalgam safety docket,

(5) Dental amalgam is the largest source of both inorganic and methyl mercury in most people with dental amalgams,



(8) Mechanisms by which mercury is documented to cause neurological conditions, B Windham(Ed) –over 150 cites,

(9) Mechanisms by which mercury is documented to cause cardiovascular conditions, - over 150 cites,

(10) Mechanisms by which mercury is documented to cause

autoimmune/immune conditions, over 150 cites,

(11) Mechanisms by which mercury is documented to cause depression/mood disorders, over 100 cites,

(12) Mechanisms by which mercury is documented to cause

fatigue/CFS/FMS, over 150 cites,


(13) Mechanisms by which mercury is documented to cause oral conditions,  over 100 cites,

(14) Dr. Man Wai Ng, Chief of the Department of Dentistry at the Children's Hospital Boston, Harvard School of Dental Medicine, FDA testimony in Dental Amalgam Docket, 2006.


          According to Dr. Haley's critique, the major scientific problems with the studies are that they: 

  1. Ignored measuring the amount of mercury exposure to children by first determining the amount of mercury emitted from an average sized amalgam outside of the mouth.  No in vitro data is given to establish a possible dose.
  2. Used urine and blood mercury levels, when 90% -plus of mercury is excreted in the feces.  This obviates any conclusions they make, as urine mercury levels are unreliable with regards to exposure, which is exactly what their own data shows.  
  3. Did not select the most sensitive clinical testing parameters for detecting mercury toxicity but instead used testing parameters that are known to fluctuate without known cause, or parameters that require much longer-term low level exposure to show an affect.
  4. Did not state that their conclusions of amalgam safety should not include children with any prior neurodevelopmental or systemic illness, because that sensitive sub-population was excluded from the trials..
  5. Ignored the drop in mercury excretion in the urine after year 2 even though the mercury exposure from amalgams remained the same or increased.  This is a sure sign of the subjects losing their ability to excrete mercury with continued exposure to this toxic metal.
  6. Suppressed their porphyrin profile data, which was collected but not published, and dismissed with an offhand comment.

These studies were poorly designed and tell us one thing of good value – that children with amalgams most likely slowly lose their ability to excrete mercury after about two years of amalgam exposure.  This experiment should have been done on primates, not humans and present a serious question of ethics in medicine.  

In fact, one of the study authors, James Woods, and others, published an analysis of the data in 2007, that showed evidence of renal damage and differences between boys and girls in the abiity to excrete mercury in the urine.   (Woods JS, Martin MD, Leroux BG, DeRouen TA, Leitao JG, Bernardo MF, et al. 2007. The contribution of dental amalgam to urinary mercury excretion in children Environ Health Perspect 115:1527Đ1531).  The study data demonstrate a declining ability for the male children's kidneys to excrete mercury via the urine after the 2nd year of continued mercury exposure from their amalgam fillings.

Barregard (Barregard L, Trachtenberg F, McKinlay S.0, Renal effects of dental amalgam in children: the New England children's amalgam trial.  Environ Health Perspect. 2008 Mar;116(3):394-9) showed a "significantly increased prevalence of microalbuminuria in the children in the amalgam group (CAT study) in the years 3-5."  This is consistent with increased kidney damage and not consistent with a conclusion of safety for dental amalgams as previously stated by the authors of the CAT studies.

More recently, Gianpaolo Guzzi and Paolo Pigatto, leading metal toxicology researchers in Italy, critiqued and amplified the Woods article in a letter, linked above.