A compilation of studies indicating inorganic mercury, as from dental mercury fillings, is mainly execreted in the feces


There is a widespread lack of knowledge from the medical profession about the main excretatory pathway of inorganic mercury. The following is a compilation of studies indicating inorganic mercury, as from dental mercury fillings, is execreted in the feces by a much higher percent than urine


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.


Human exposure to mercury and silver released from dental amalgam restorations.

Arch Environ Health. 1994 Sep-Oct;49(5):384-94.

Skare I, Engqvist A.

Source: National Institute of Occupational Health Stockholm, Sweden.


In 35 healthy individuals, the number of amalgam surfaces was related to the emission rate of mercury into the oral cavity and to the excretion rate of mercury by urine. Oral emission ranged up to 125 micrograms Hg/24 h, and urinary excretions ranged from 0.4 to 19 micrograms Hg/24 h. In 10 cases, urinary and fecal excretions of mercury and silver were also measured. Fecal excretions ranged from 1 to 190 micrograms Hg/24 h and from 4 to 97 micrograms Ag/24 h. Except for urinary silver excretion, a high interplay between the variables was exhibited. The worst-case individual showed a fecal mercury excretion amounting to 100 times the mean intake of total Hg from a normal Swedish diet. With regard to a Swedish middle-age individual, the systemic uptake of mercury from amalgam was, on average, predicted to be 12 micrograms Hg/24 h.

PMID: 7944571


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


Mercury in saliva and feces after removal of amalgam fillings.

Toxicol Appl Pharmacol. 1997 May;144(1):156-62.

Björkman L, Sandborgh-Englund G, Ekstrand J.

Source: Department of Basic Oral Sciences, Karolinska Institutet, Stockholm, Sweden.


The toxicological consequences of exposure to mercury (Hg) from dental amalgam fillings is a matter of debate in several countries. The purpose of this study was to obtain data on Hg concentrations in saliva and feces before and after removal of dental amalgam fillings. In addition Hg concentrations in urine, blood, and plasma were determined. Ten subjects had all amalgam fillings removed at one dental session. Before removal, the median Hg concentration in feces was more than 10 times higher than in samples from an amalgam free reference group consisting of 10 individuals (2.7 vs 0.23 mumol Hg/kg dry weight, p < 0.001). A considerable increase of the Hg concentration in feces 2 days after amalgam removal (median 280 mumol Hg/kg dry weight) was followed by a significant decrease. Sixty days after removal the median Hg concentration was still slightly higher than in samples from the reference group. In plasma, the median Hg concentration was 4 nmol/liter at baseline. Two days after removal the median Hg concentration in plasma was increased to 5 nmol/liter and declined subsequently to 1.3 nmol/liter by Day 60. In saliva, there was an exponential decline in the Hg concentration during the first 2 weeks after amalgam removal (t 1/2 = 1.8 days). It was concluded that amalgam fillings are a significant source of Hg in saliva and feces. Hg levels in all media decrease considerably after amalgam removal. The uptake of amalgam mercury in the GI tract in conjunction with removal of amalgam fillings seems to be low.

PMID: 9169079


Speciation of mercury excreted in feces from individuals with amalgam fillings.

Arch Environ Health. 1998 May-Jun;53(3):205-13.

Engqvist A, Colmsjö A, Skare I.

Source: Department of Toxicology and Chemistry, National Institute for Working Life, Solna, Sweden.


Investigators established methods for the analysis of total mercury (Hg-total), oxidized mercury and mercury bound to sulfhydryl groups (Hg-S), mercury vapor (Hg0), and mercury from amalgam particles (APs) in fecal samples. Two individuals consumed mercury as a mercury-cysteine complex mercury vapor, and mercury from amalgam particles, and the cumulative excretion of mercury in feces was followed. Investigators found that 80% of the mercury from amalgam particles and mercury bound to sulfhydryl groups was excreted, but only 40% of the mercury vapor was excreted. Speciation of mercury excreted in feces from 6 individuals with a moderate loading of amalgam fillings showed that most of the mercury originating from the fillings consisted of oxidized mercury, which was probably bound to sulfhydryl-containing compounds. The proportion of amalgam particles in fecal samples from these individuals was low, and it did not exceed 26% of the total amount of mercury excreted.

PMID: 9814717

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