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Here we ask the big question all future mothers in the dental profession should ask themselves: Does mercury from amalgams threaten the health of my unborn child?

One Story of loss

"A thirty-year-old dental surgeon who worked until the 35th week of pregnancy in a surgery in which mercury vapour concentrations in excess of the threshold limit value (TLV) had been detected, gave birth at 42 weeks to a small-for-dates baby with severe brain damage." The baby died nine days later.[1]

The authors go on to disparage the level of education within the profession about these dangers: "In spite of discussion in the profession regarding mercury hazards little mention has been made of the foetotoxic effects of mercury vapour. Some 80% of inhaled mercury vapour is retained: Animal data show that such atomic mercury dissolved in blood rapidly crosses the placenta."[1]

The Vulnerable Brain

The cold, hard truth about all forms of mercury is that they damage developing fetuses, especially the brain.[2] In addition, it is well-known that the fetus is much more sensitive to mercury toxicity than the mother, since in outbreaks of mercury poisoning "mothers with no symptoms of nervous system damage gave birth to infants with severe disabilities."[3]

Methylmercury, which can form in the mouth when elemental mercury vapor is present due to dental amalgam or ambient mercury vapor, is even more toxic to the human embryo. (See our Chemistry page for details on how methylmercury forms in the mouth). The EPA states that methylmercury "can adversely affect a baby's growing brain and nervous system. Impacts on cognitive thinking, memory, attention, language, and fine motor and visual spatial skills have been seen in children exposed to methylmercury in the womb."[3]

An increasing number of researchers caution against the use of mercury around pregnant women: "As always, during pregnancy, female dental healthcare professionals may be exposed to unsafe levels of mercury , which are known to damage the developing fetal brain."[4]

From Mother to Child

Does exposure to mercury from dental amalgams really lead to fetal damage? We know that even a small amount of mercury in the womb, whether elemental, ionic, or organic, harms the developing child.[2,3] Now that it has been proven that the dental amalgam leaks mercury vapor into the body of its host, some pro-amalgamists have taken to claiming that elemental and ionic mercury does not pass through the placenta[5] (since methylmercury does, without a doubt[6]).

There are, however, numerous studies[7,8] proving that all forms of mercury find their way from the mother's body to the developing fetus. For example, one Swedish study specifically shows that inorganic mercury levels in the fetus correspond directly to the number of amalgam surfaces in the mother.[9]

In fact, several studies[10] show the link between the number of amalgam surfaces in a mother's mouth with the mercury in the blood, hair, and urine of the newborn child: "Placental, fetal, and infant mercury body burden correlates with the numbers of amalgam fillings of the mothers."[11] One study found the same correlation between maternal amalgams and the mercury in the kidneys, liver, and cerebral cortex of infants.[12]

Elemental mercury is transported freely across the placenta.[13,14] "Human placenta does not represent a real barrier to the transport of Hg(0); hence, fetal exposure occurs as a result of maternal exposure to Hg, with possible subsequent neurodevelopmental disabilities in infants."[15] In women with amalgam surfaces, mercury levels are also high in the umbilical cords.[15]

And even once the baby is born, the problems don't stop there. Breast milk from mothers with amalgams has also been shown to contain mercury in proportion to the number of amalgam fillings they have.[10,16,17] This German study sums it up:

"The higher Hg burden of infants' tissues from mothers with dental amalgam, as reported previously, must be explained (1) by a prenatal transfer of Hg from the mother's fillings through the placenta to the fetus, followed by a redistribution of this Hg in the body of the newborn, and (2) an additional burden via breast milk."[17]

Reproductive failure in Dental staff

So, there's sufficient evidence showing that fetuses and newborns receive mercury from maternal amalgams. What about pregnant women in the dental profession? Is exposure to ambient mercury vapor, even if within legal limits, an acceptable risk?

Several studies have noted the low fertility rates among female dental professionals. One study found that female dental assistants who prepared 30 or more amalgams per week were only 63% as likely to become pregnant as the control group (measured by the number of menstrual cycles it had taken them to become pregnant).[18] They also reported increased "abnormalities of the menstrual cycle including painful menstruation and changes in bleeding patterns and menstrual cycle duration among workers exposed to mercury."[18]

Sadly, another study reported a "significant, positive association between TMLs [Total Mercury Levels] in the hair of exposed women and the occurrence of reproductive failures in their history." They suggest that "dental work could be another occupational hazard with respect to reproductive processes."[19]

The fetotoxic effects of mercury vapor in the dental profession are becoming increasingly clear. Inhaled mercury vapor from the preparation and agitation of amalgams is absorbed by the lungs[1], enters the blood stream, and from there begins to wreak its havoc.[20] It may even be deposited in the saliva, where it is converted into methylmercury by oral bacteria, an extremely poisonous compound.[21,22]

Because of the rising number of experts who warn pregnant women against the dangers of mercury vapor, the dental profession in the U.S. may eventually be forced to change its policies: "The possibility of a relationship between occupational exposure during pregnancy and untoward effects on the foetus resulting in miscarriages, perinatal death and foetal abnormalities has been studied; although not conclusive, results indicated a higher incidence of adverse pregnancy outcome."[7]

These authors strongly suggest that pregnant women working in the dental office, "should not be occupationally exposed to air concentrations of mercury vapor greater than 0.01 mg. per cubic meter."[8] This is 20% of the current legal limit.

With all this evidence, and considering what is at stake, can we agree to take the right steps towards a future that prioritizes the health and welfare of our own families over the agenda of an entrenched and irresponsible professional community?

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REFERENCES - See our complete list of sources

1. Gelbier S, Ingram J. Public Health. Possible foetotoxic effects of mercury vapour: a case report. 1989 Jan;103(1):35-40.

2. Clarkson TW, Magos L. The toxicology of mercury and its chemical compounds. Crit Rev Toxicol. 2006 Sep;36(8):609-62.

3. EPA on Health Effects of Mercury:

4. Guzzi G, Pigatto PD, Ronchi A, Minoia C. Exposure to mercury among Norwegian dentists and dental healthcare personnel. Scand J Work Environ Health. 2010 Sep;36(5):430-1. Epub 2010 Feb 19.

5. Wannag A, Skjaeråsen J. Mercury accumulation in placenta and foetal membranes. A study of dental workers and their babies. Environ Physiol Biochem. 1975;5(5):348-52.

6. Yorifuji T, Kashima S, Tsuda T, Harada M. What has methylmercury in umbilical cords told us? - Minamata disease. Sci Total Environ. 2009 Dec 20;408(2):272-6. Epub 2009 Oct 29.

7. Elghany NA, Stopford W, Bunn WB, Fleming LE. Occupational exposure to inorganic mercury vapour and reproductive outcomes. Occup Med (Lond). 1997 Aug;47(6):333-6.

8. Koos BJ, Longo LD. Mercury toxicity in the pregnant woman, fetus, and newborn infant. A review. Am J Obstet Gynecol. 1976 Oct 1;126(3):390-409.

9. Ask K, Akesson A, Berglund M, Vahter M. Inorganic mercury and methylmercury in placentas of Swedish women. Environ Health Perspect. 2002 May;110(5):523-6.

10. Drexler H, Schaller KH. The mercury concentration in breast milk resulting from amalgam fillings and dietary habits. Environ Res. 1998 May;77(2):124-9.

11. Mutter J, Naumann J, Guethlin C. 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.

12. Drasch G, Schupp I, Höfl H, Reinke R, Roider G. Mercury burden of human fetal and infant tissues. Eur J Pediatr. 1994 Aug;153(8):607-10.

13. Lien DC, Todoruk DN, Rajani HR, Cook DA, Herbert FA. Accidental inhalation of mercury vapour: respiratory and toxicologic consequences. Can Med Assoc J. 1983 Sep 15;129(6):591-5.

14. Takahashi Y, Tsuruta S, Arimoto M, Tanaka H, Yoshida M. Placental transfer of mercury in pregnant rats which received dental amalgam restorations. Toxicology. 2003 Mar 14;185(1-2):23-33.

15. Palkovicova L, Ursinyova M, Masanova V, Yu Z, Hertz-Picciotto I. Maternal amalgam dental fillings as the source of mercury exposure in developing fetus and newborn. J Expo Sci Environ Epidemiol. 2008 May;18(3):326-31. Epub 2007 Sep 12.

16. Da Costa SL, Malm O, Dórea JG. Breast-milk mercury concentrations and amalgam surface in mothers from Brasília, Brazil. Biol Trace Elem Res. 2005 Aug;106(2):145-51.

17. Drasch G, Aigner S, Roider G, Staiger F, Lipowsky G. Mercury in human colostrum and early breast milk. Its dependence on dental amalgam and other factors. J Trace Elem Med Biol. 1998 Mar;12(1):23-7.

18. Rowland AS, Baird DD, Weinberg CR, Shore DL, Shy CM, Wilcox AJ. The effect of occupational exposure to mercury vapour on the fertility of female dental assistants. Occup Environ Med. 1994 Jan;51(1):28-34.

19. Sikorski R, Juszkiewicz T, Paszkowski T, Szprengier-Juszkiewicz T. Women in dental surgeries: reproductive hazards in occupational exposure to metallic mercury. Int Arch Occup Environ Health. 1987;59(6):551-7.

20. Lorscheider FL, Vimy MJ, Summers AO. Mercury exposure from "silver" tooth fillings: emerging evidence questions a traditional dental paradigm. FASEB J. 1995 Nov;9(14):1499-500.

21. Leistevuo J, Leistevuo T, Helenius H, Pyy L, Osterblad M, Huovinen P, Tenovuo J. Dental amalgam fillings and the amount of organic mercury in human saliva. Caries Res. 2001 May-Jun;35(3):163-6.

22. Pigatto PD, Guzzi G. Oral lichenoid lesions: more than mercury. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 2005 Oct;100(4):398-400.