Human Placenta and Markers of Heavy Metals Exposure: Esteban-Vasallo et al. Respond

María D. Esteban-Vasallo,¹ Nuria Aragonés,² Marina Pollan,² Gonzalo López-Abente,² Beatriz Perez-Gomez²

¹Subdirectorate for Health Promotion and Prevention, Madrid Regional Health Authority, Madrid, Spain; ²National Center for Epidemiology/CIBERESP, Carlos III Institute of Health, Madrid, Spain, E-mail: bperez@isciii.es

Environ Health Perspect 121:a10–a11 (2013). http://dx.doi.org/10.1289/ehp.1206061R [Online 1 January 2013]


The authors declare they have no actual or potential competing financial interests.

We appreciate the interest of Pigatto et al. in our review (Esteban-Vasallo et al. 2012). We understand their concern regarding mercury amalgams; however, the purpose of our review was to summarize the available information on total mercury, cadmium, and lead levels in human placental tissue, obtained from studies that reported original quantitative data. Published evidence suggests a possible association between mercury released from mercury-containing dental amalgam fillings and levels of this metal in diverse fetal tissues (kidney, brain, and cord blood) (Drasch et al. 1994). In contrast, studies focusing on human placenta and amalgams are scarce and their results inconsistent. The only two studies included in our review that assessed a possible relationship between dental fillings and total mercury—a small study in Taiwan (46 women) (Hsu et al. 2007) and another in Jamaica (52 women) (Grant et al. 2010)—found no association. Only Ask et al. (2002) reported higher mercury levels in mothers with a higher number of fillings, but they studied inorganic mercury and not total mercury.

None of the studies mentioned by Pigatto et al. in their letter (Clarkson and Magos 2006; Gundacker and Hengstschlager 2012; Richardson et al. 2011) includes original data, although we did identify an additional reference from those articles that might provide more data on this issue, a symposium abstract by Ursinyova et al. (2006). In this abstract, the authors described a significant correlation between the number of amalgams and placental mercury levels in 409 women; however, these findings have not yet been published in a full report that would allow us to better evaluate the results. In addition, Wannag and Skjaeråsen (1975) seemed to provide original information, but we were unable to find this paper for our review. In this context, we have to disagree with Pigatto et al.; in our opinion, the association between mercury exposure from dental amalgam fillings and levels of this metal in human placenta cannot yet be considered as well-established.

References

Ask K, Åkesson A, Berglund M, Vahter M. 2002. Inorganic mercury and methylmercury in placentas of Swedish women. Environ Health Perspect 110:523–526.

Clarkson TW, Magos L. 2006. The toxicology of mercury and its chemical compounds. Crit Rev Toxicol 36(8):609–662.

Drasch G, Schupp I, Höfl H, Reinke R, Roider G. 1994. Mercury burden of human fetal and infant tissues. Eur J Pediatr 153:607–610.

Esteban-Vasallo MD, Aragonés N, Pollan M, López-Abente G, Perez-Gomez B. 2012. Mercury, cadmium and lead levels in human placenta: a systematic review. Environ Health Perspect 120:1369–1377.

Grant C, Lalor G, Fletcher H, Potter T, Vutchkov M, Reid M. 2010. Elements in human placentae in Jamaica. West Indian Med J 59:479–485.

Gundacker C, Hengstschläger M. 2012. The role of the placenta in fetal exposure to heavy metals. Wien Med Wochenschr 162:201–206.

Hsu CS, Liu PL, Chien LC, Chou SY, Han BC. 2007. Mercury concentration and fish consumption in Taiwanese pregnant women. BJOG 114:81–85.

Richardson GM, Wilson R, Allard D, Purtill C, Douma S, Graviere J. 2011. Mercury exposure and risks from dental amalgam in the US population, post-2000. Sci Total Environ 409:4257–4268.

Ursinyova M, Masanova V, Palkovicova L, Wsolova L. 2006. The influence of mother’s dental amalgam fillings on prenatal and postnatal exposure of children to mercury [Abstract]. Epidemiology 17:S494–S495.

Wannag A, Skjaeråsen J. 1975. Mercury accumulation in placenta and foetal membranes. A study of dental workers and their babies. Environ Physiol Biochem 5:348–352.