Dental Amalgam and Mercury page

Dental Amalgam and Mercury pages 12345678

A Definitive Study on Mercury Blood Levels

The following is my own “book report” of an extremely well done and definitive study pertaining to the safety of dental amalgam.  It is written for the benefit of the general public in the form of a simple translation of the original publication.  I have avoided using specific statistical information and substituted a less confusing overview style in order to avoid confusion on the part of readers without a background in statistics.  (Note: The ads on this site are placed by Google bots and help to defray the cost of web hosting.)

I have also avoided confusing terminology and have tried to define and explain medical concepts.  While this discussion excludes some information contained in the original study, the excluded material does not detract from the overall sense and tone of the original.   This is a reasonably faithful translation of a scientific paper for the interested lay public.  For those interested in obtaining the original study, the information is as follows:

Serum mercury concentration in relation to survival, symptoms, and diseases: results from the prospective population study of women in Gothenburg, Sweden

Margareta Ahlqwist, Calle Bengtsson, Leif Lapidus, Ingvar A: Bergdahl and
Andrejs Schutz

Departments of Oral Diagnostic Radiology, Primary Health Care and Medicine, Goteborg
University, Gothenburg, Sweden; Department of Public Health and Clinical Medicine, Section of
Occupational Medicine, Umeâ University, Umeâ, Sweden; Department of Occupational and
Environmental Medicine, Lund University, Lund, Sweden

Acta Odontol Scand 1999,57:168-174.  oslo ISSN 0001-6357

Purpose of study

“Because of their release of mercury, dental amalgam restorations have been highlighted as a possible source of different health disturbances and have been the root of vigorous debate.  The purpose of this study is to analyze potential associations between symptoms and diseases on the one hand, and Serum Mercury levels on the other”.

Note that this study deals primarily with correlations between serum levels of mercury on the one hand, and signs, symptoms, complaints and physiological factors exhibited by the study subjects on the other.  The serum levels of mercury result from a combination of the number of amalgam fillings in the patients’ mouths and the amount of mercury derived from the food, water and air consumed by the patient.

How the study was done

This study, done in Sweden, involved a sample of 1462 women between 38 and 60 years old when the study began in 1968.  These women were followed over the course of 24 years until the study’s end in 1993.  The women were given dental and medical examinations at the beginning of the study and periodically reexamined at intervals throughout the study period.  The number of teeth filled with amalgam was recorded, as well as each woman’s objective and subjective health status.  Blood work, including serum mercury levels were also taken as a routine part of the medical examinations.

During the 1974-75 and 1980-81 phase of the study, and again at the end of the study in 1992-93, the women answered a standardized, self administered questionnaire which included 3o questions about different symptoms or complaints .  They included the following:


symptomsAlong with serum levels of mercury, the following blood and serum variables were recorded at intervals during the study.


Hemoglobin, Hematocrit, Leukocytes, Platelets, Glucose, ESR (sedimentation rate)


TIBC (total iron binding capacity), Creatinine, Iron, Chloride, Potassium, Sodium, Calcium, Cholesterol, Triglycerides, Uric acid, Alkaline phosphatase, Bilirubin, Protein, B 12, IgA, IgD, IgG, 1gM, IgE
(note: The last six variables above represent serum levels of antibodies and measure the immune response of the body.)


Concentration capacity Protein

In addition to the information noted above, statistics were kept during the course of the study concerning the occurrence of disease states including the following:

Myocardial Infarction (heart attack)
Mortality (death)

What the researchers were looking for in this study

The point of this study was to look at a normal population and measure the correlations between the amount of mercury they consume and the various signs, symptoms, complaints and disease states mentioned above.  This relates to dental amalgam since the presence of these dental restorations contributes to the total serum mercury level in any study participant who has them.

The controversy over the damage caused by ingested mercury from amalgam fillings had been raging since the early nineteenth century.  A large percentage of the population of the industrialized world now had at least a few teeth repaired using dental amalgam.  Previous studies had established that dental amalgams do contribute to the patient’s overall serum mercury levels.

The big question was; does the level of serum mercury contributed by dental amalgam cause disease or even subtle symptoms in any percentage of the population?   This study sets out to answer this major question by answering the following three questions:

1. Do higher serum levels of mercury correlate with an increase in patients’ symptoms and complaints, or in the presence of subtle disease states?

2.  Do higher serum levels of mercury correlate with measurable physiologic changes in blood values?

3. Do higher serum levels of mercury correlate with higher morbidity (suffering) and mortality (death) by increasing the rate of heart attack, stroke, diabetes, cancer, or death?

More succinctly, “In a normal population of persons, most with amalgam fillings in their teeth, does a higher level of serum mercury (some of which is contributed by the amalgam fillings) actually correlate with an increase in patient disease, discomfort or early death?”

To understand this study, it is also necessary to reiterate that dental amalgams do contribute to the serum mercury blood level.  It is also necessary to understand just how the levels of mercury contributed by dental amalgam relate to mercury from other sources (ordinary food, water and air).

Previous studies had already established that there IS a correlation between the number of amalgam fillings in a patient’s mouth and the level of serum mercury.  The more amalgam fillings a particular group of patients had, the higher the average serum level of mercury in their blood.  This does not mean that amalgam fillings were the sole source of mercury in the study subjects’ blood.  This study was, after all, done in Sweden where the population tends to eat more fish than many other nations.  A study subject who habitually eats large quantities of fish would have a much higher serum mercury level than one who eats little fish, regardless of the presence or absence of amalgam fillings in either subject’s mouths.

Mercury blood levels measured in another study (not this one) indicated that the average level in patients with amalgam was 0.7 ng/mL compared with a value of 0.3 ng/mL for subjects with no amalgam. This difference was also found to be statistically significant (P 0.01). However, one should be aware of another study in Sweden that demonstrated that one saltwater seafood meal per week raised average blood levels of mercury from 2.3 to 5.1 ng/mL, a sevenfold increase (2.8 ng/mL) compared with that (0.4 ng/mL) associated with amalgam restorations.  In other words, the actual serum level of mercury contributed by the presence of amalgam fillings was so small that on any given day, it could be completely overwhelmed by the mercury contained in normal food and water.

Clarification: The term “ng” refers to nanograms, or billionths of a gram.  It almost always refers to the level of mercury found in a milliliter of blood or serum.The term “μg” refers to micrograms, or millionths of a gram.  It generally refers to the level of mercury inhaled or ingested into the body.

Results of the study

1. Symptoms and complaints

In 1975, the following symptoms and complaints showed NO statistical increase or decrease in occurrence since the study began in 1968, and no statistical correlation with the level of mercury measured in the study participant’s blood:


The following symptoms and complaints did show a statistical negative correlation in occurrence”.

Readiness to cry

A negative correlation means that these symptoms were actually lesslikely to occur with higher serum concentrations of mercury.  This should not be taken to mean that mercury should be used to “cure” these symptoms.  Even though the correlation was considered significant, the actual correlation was still very small (p=0.004 and p-0.016 respectively).  These correlations disappeared when the patient’s age and education level were included in the analysis.

In 1980-81, the same correlation analyses were carried out with similar results.  The following symptoms and complaints showed no statistical increase or decrease in occurrence since the study began in 1968:


The following statistical complaints did show another negativecorrelation in occurrence:

Poor appetite

Once again, a negative correlation means that these symptoms are less likely to occur in a population with a higher serum mercury.  Unlike the negative correlations seen in 1975, these correlations did not disappear when the patient’s age and education level were included in the analysis.  Even so, this should not be taken to mean that mercury should be used to “cure” these symptoms.

2. Blood serum and urine variables in relation to serum mercury levels

In the 1968-69 study, several blood related variables showed statistically significant differences that varied with the serum mercury levels, while the 1980-81 study showed the following:

Blood hemoglobin concentration showed a positive correlation in 1968-69, and a negative correlation in 1980-81.  Hemoglobin is essentially a measure of iron in the blood, and a positive correlation means that the presence of higher levels of mercury in the serum of these study subjects tended to be correlated with MORE iron in the blood.  In other words, these patients with higher serum levels of mercury were were less likely to be anemic than those with lower levels.  Once again, mercury does NOT cure anemia.  This correlation, while significant, was still relatively small.  In the 1981 study, this correlation reversed itself and became a negative correlation.  The meaning of these contradictory results is not apparent.

Erythrocyte Sedimentation Rate (ESR) was negativelycorrelated with serum mercury levels in 1968-69,but not correlated in 1980-81.  Sedimentation rate is a clinical laboratory test that is roughly correlated with the level of inflammation found in various disease processes (especially autoimmune diseases).  This test is non specific in nature, and is used in conjunction with other tests to measure the severity of inflammatory diseases.  Negative correlation suggests that higher levels of mercury tend to reduce the level of non specific inflammation.  Once again this result does not suggest that mercury acts as an anti-inflammatory drug.  since the correlation disappeared in the later study, the meaning of the earlier correlation is not apparent.

Serum levels of potassium were negatively correlated with serum mercury levels in the 1968-69 study, but not correlated in the 1980-81 study.  The actual decrease in in potassium levels caused by higher serum mercury levels is extremely small and the practical significance of this finding is uncertain.

Serum levels of triglycerides were negatively correlated with higher levels of serum mercury in the 1968-69 study, but not correlated in the 1980-81 study.  Triglycerides are a measure of lipids (soluble fats) in the serum.  Triglycerides are medically associated with cholesterol, which is also a form of soluble fat.  A negative correlation suggests that the levels of triglycerides decreases with increasing levels of serum mercury.  Once again, the decrease in the earlier study is of little practical significance, especially since the correlation disappeared in the later study.

Serum levels of vitamin B-12 were positively correlated with the level of serum mercury.  This factor was measured only in the 1968-69 study.  Vitamin B-12 is actively involved in the metabolism of mercury, and the authors assumed that this fact accounts for this correlation.

Serum levels of IgE and IgA showed positive statistical correlation with the level of serum mercury, however, this correlation was somewhat confused disappearing in one case when background variables were included in the analysis, and appearing in the other case only when  background variables were included.  IgE and IgA are different types of antibodies and as such are an indication of the function of the immune system.  The correlations are small, and judging by the lack of consistent correlation between serum levels of mercury versus the list of symptoms and complaints above, they do not appear to have a measurable practical effect on the general health of the subjects.

3. Endpoints (disease states developed) during the follow-up period

A total of 253 women (out of the original 1462) died during the 24 year study and follow-up. 87 women developed myocardial infarction (heart attack) and of those, 39 died.  new signs of stroke were observed in 77 women, 77 developed diabetes, and 208 were diagnosed with cancer.

There was no statistically significant correlation between serum mercury levels and the different diseases (heart attack, stroke, diabetes and cancer).  On the other hand there was a statistically significant negativecorrelation between mortality (death) and serum mercury levels when background factors were included in the analysis.  This means that higher serum levels of mercury were correlated with a lesser likelihood of death during the study period.  Again, we are talking relatively weak correlations and readers should not infer that mercury somehow prolongs life or immunizes against death!


The following discussion is composed of quotes from the original paper:

The present study does not indicate any unfavorable influence of serum mercury on symptoms experienced, incidence of disease, or mortality in the general population.

In three previous reports, the authors have related the number of amalgam fillings to different symptoms, incidence of early death and certain diseases, and to laboratory variables without finding any adverse effects of amalgam fillings as far as these variables are concerned.

The only positive statistically significant correlations with symptoms and complaints were those observed between over-exertion and poor appetite, on the one hand, and serum mercury on the other, both being negative, thus indicating a lower prevalence of the symptom with higher serum mercury.

One possible reason for the correlation between higher serum mercury and lower mortality may be the result of the protective effect from fish consumption.

The positive correlation between increased serum levels of mercury and increased levels of serum vitamin B-12 could be a result of vitamin B-12’s roll in the metabolism of mercury, or it may reflect the fact that fish is a dietary source of both mercury and vitamin B-12.

IgA is responsible for mucosal immunity and is thus the first line of defense for the majority of infections.  The fairly weak association between serum IgA concentration and serum mercury levels in the present study may be a chance finding, but it could also indicate an immunological response to mercury from amalgam fillings.  However, from the authors’ data, they cannot reveal any impact of clinical significance of mercury uptake from amalgam fillings as reflected by serum mercury or number of fillings.

We conclude that there were some associations between biological variables (serum concentrations of IgA and B-12) and serum mercury levels.  Our main conclusion from our prospective population study, however, is that it gives no support for an unfavorable influence of the serum mercury levels on experienced symptoms, mortality, or incidence of diseases in a general population of middle-aged or older women.

Dental Amalgam and Mercury pages 12345678