Understanding the inherent flaws and methodology in Rodney Mackert’s mercury exposure claims

Boyd Haley PhD quantitatively measured mercury release from dental amalgams ranging from 4 – 22 micrograms/cm2 per day – “without galvanism, excess heat or pressure from chewing – all factors that increase mercury release from amalgams in the mouth”. This study was done using very small single-spill fillings in a sealed container.




When reporting on how much mercury is released from dental mercury amalgam fillings most journalists cite The American Dental Association’s spokesman Rodney Mackert’s “estimates” without understanding any of the inherant flaws in his methodology.  Read on to find out more about the debunking of his dubious claim that only “minute amounts of mercury are released by dental amalgam”.

Vas Aposhian (Aposhian, 1992 ) documented the fact, now universally accepted by the scientific community, that dental amalgam fillings contribute the majority of mercury body burden in the general population. These findings have been corroborated by other research including human cadaver studies. 

Vimy and Lorscheider derived an average absorbed mercury dose of 10 μg per day from amalgam fillings from their measurements of mouth air. Other groups have reported varying estimates. On the low end, Mackert and Berglund et. al., by applying assumptions and inferences concerning how much mouth air is actually inhaled, arrived at average daily doses for subjects with twelve or more amalgam surfaces, of 1.83 and 1.7 μg, respectively (not zero). The question of inhaling mouth air should be moot, though, because elemental mercury vapor is lipophilic, and is absorbed easily through cell membranes and mucosal barriers. On the high end, Patterson et. al. reported absorbed doses of as much as 27 μg per day. Skare and Engqvist, by metabolic methods, arrived at a figure of 12 μg per day for a group of subjects with an average of 47 amalgam surfaces.

The current best accepted reference on absorbed dose of mercury from amalgam fillings comes from the World Health Organization proceedings of 1991, which was the report of a meeting of toxicologists and environmental health specialists (few dentists and no industry lobbyists, the opposite of the 1997 WHO meeting!). The conclusion of that group was that the average person in the industrial world with an average number of amalgam fillings, and no occupational exposure to mercury would absorb between 3 – 17 μg per day, with an average of 10 μg, from the fillings; 2.3 μg from all dietary sources; and 0.3 μg from all other environmental sources.

Mark Richardson PhD (previously of Health Canada) presented a chart (below) summarizing eighteen separate estimates of mercury exposure due to amalgam in adults. The range of the estimates intersects with limits recommended for non-occupational exposure by  the US Environmental Protection Agency (EPA) and California’s Environmental Protection Agency (CalEPA), as shown by the vertical blue and red lines.


Published Estimates of Hg Exposure in Adults With Dental Amalgam (Mercury Fillings)


Rodney Mackert

These measurements showed that mercury release from amalgams vastly exceed the ʻestimatedʼ release reported by ADA ‘authority’ Rodney Mackert, DDS, who claimed that 7 fillings release only a single microgram of mercury per day – according to a Wall Street Journal article. It is important to note that Mackert, rather than directly measuring the actual quantity of mercury released by amalgams, instead “estimated” the amount of mercury released from amalgam fillings by looking at the mercury level in the urine of several test subjects. 

Mackert has no training in toxicology as he is a practicing dental materials expert. 

It is well established that less than 10% of mercury leaves the body by the kidney/urinary route (the vast majority leaving by the bilary transport/fecal route). As a result of this flawed methodology the ADA estimated level of mercury release by amalgam grossly understates the amount of the mercury released. 


Compilation of studies indicating mercury from amalgams are excreted fecally

Inorganic mercury (as from dental mercury fillings) is mainly execreted in the FECES !

There are only a few previous studies on fecal levels of mercury after amalgam placement. Borinski, 1931, measured a total excretion (feces + urine) of 10-100 micrograms/day in 50% and more than 100 in 50% of the children after amalgam therapy. The increased levels lased for some months and subsequently dropped considerably. The levels in feces were generally five (5) times higher than those in urine.

Frykholm, 1957, found somewhat increased urine mercury levels after amalgam placement in dogs and in humans but up to 87.000 micrograms/100g feces in dog and 1.900 micrograms/100 g in humans where a much smaller amount of amalgam was used. A second peak of mercury excreation occurred after removal of the fillings, irrespective of precautions (rubber dam) or extraction of teeth instead of drilling.

Minimal studies show that the distribution of the execretion between the different routes is dose dependent, Rothstein & Hayes, 1960

The influence of the size of the dose on the distribution and elimination of inorganic mercury Hg(NO3)2 in the rat, Ceber 1962.

Hg is excreted in both urine and feces. Chronic exposure to Hg0, as from dental amalgam, results in a steady state where daily uptake and total daily excretion (urine + faeces) of Hg are in equilibrium, Rothstein & Hayes, 1964

Cherian et al. 1978 exposed human volunteers to radioactively labelled Hg vapor, 79% of the excreted amount was in feces.

Kristensen & Hansen 1980 i.e. at decreasing doses the importance of fecal route increases, 85% was found in feces.

However, at exposure levels sufficient to produce the same urinary Hg concentrations associated with up to 128 amalgam-filled tooth surfaces (the reported maximum number of filled tooth surfaces in the US population; see Table 1), urinary excretion represents 40% of total daily excretion of Hg. This latter value can be determined from the data presented by Roels et al. (1987), assuming that adult working males inhale an average of 6.6 m3 of air in an 8 hour shift (U.S. EPA, 1989a), and that 80% of inhaled Hg is absorbed. From the data of Roels et al. (1987), the proportion of total Hg excretion which occurred via the urine was 39.8 ± 12.5 %.

1989 – 1990
More recent experiments on sheep, Hahn et al, 1989, and monkeys, Hahn et al 1990, clearly shows the major part of amalgam derived mercury to pass via the gastrointestinal tract where some of it is absorbed in tissues. These animal experiments also demonstrated a considerable absorption directly into the jaw bone an Hg accumulation in various tissues.

Skare, 1992, estimated that half of the gastrointestinal mercury might be swallowed material from corrosion and abrasion and half absorbed and execreted into the gastrointestinal tract. More accurate information is difficult to obtain when amalgam is still present in the teeth. Mercury vapor is generally considered to be the most toxic form of inorganic mercury but also swallowed mercury compounds with low solubility have caused serve poisonings after long exposure.

Skare & Engqvist, 1992, found fecal excretion of mercury from amalgam in the range 27-190 micrograms/day in persons having from 18-82 amalgam surfaces (crowns counted as 6 surfaces). Urine levels were “normal” with only one value over 8 micrograms/day.

In feces of amalgam bearers, Skare and Engqvist 1994

Hg is excreted in both urine and feces. Chronic exposure to Hg0, as from dental amalgam, results in a steady state where daily uptake and total daily excretion (urine + faeces) of Hg are in equilibrium, Weiner and Nylander 1995

In feces of amalgam bearers , Bjorkman et al. 1997

In feces of amalgam bearers, Engqvist et al. 1998



A study done by Dr. David Quig of Doctorʼs Data showed that an average of 60 micrograms are excreted daily in the feces of the average amalgam bearer. Therefore, if only 1 microgram were excreted by the required 7 amalgams, as suggested by Mackert and the ADA, to reach this average fecal excretion rate a person would have to have 420 amalgams.

It is important to note that the ADA spokespersons base their opinion on amalgam safety based totally on mercury levels in the blood, urine or hair. Recent science has shown that these are not measures of total exposure or body burden but likely represent a combination of exposure and the excretion ability of the individual.

iaomtRichard D. Fischer, D.D.S., FAGD, MIAOMT; IAOMT liaison to the IAOMT Scientific advisory board.                       

Vasken Aposhian, PhD, Professor Emeritus of Pharmacology and Professor Emeritus of Cellular and Molecular Biology, University of Arizona, College of Medicine.    

Maths Berlin, MD, PhD, (Advisor to the IAOMT Scientific Advisory Board) Professor Emeritus of Environmental Medicine, Medical Faculty  University of Lund, Sweden; Chairman of two World  Health  Organization conferences on mercury exposure in 1991.

Thomas Burbacher, PhD , Associate Professor of Environmental and Occupational Health Sciences; Research Affiliate, Center on Human Development and Disability; Director, Infant Primate Research Laboratory , University of Washington Center for Human Development and Disability.

Louis W. Chang, PhD, Emeritus Professor of Pathology, University of Arkansas School of Medical Sciences; Founding Director of the Taiwan Division of Environmental Health & Occupational Medicine. 

Boyd Haley, PhD, MIAOMT, (Chairman SAB IAOMT), Professor and former Chairman of the Department of Chemistry, University of Kentucky.Herb Needleman, MD, Professor of Child Psychiatry and Pediatrics, University of Pittsburgh School of Medicine.

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