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Larissa Takser,^1,2 Donna Mergler,³ Mary Baldwin,³ Sylvie de Grosbois,³ Audrey Smargiassi,³ and Julie Lafond^1,2

¹Laboratoire de Physiologie Materno-fœtale, ²Centre de Recherche BioMed, and ³CINBIOSE (Centre d'étude des interactions biologiques entre la santé et l'environnement), Université du Quebec à Montréal, Montréal, Quebec, Canada

Abstract
Polychlorinated biphenyls (PCBs) , chlorinated pesticides, and mercury are global environmental contaminants that can disrupt the endocrine system in animals and humans. However, there is little evidence that they can interfere with endocrine status in pregnant women and neonates at low levels of exposure. The aim of this study was to examine thyroid hormone levels during pregnancy and in cord blood in relation to blood concentrations of organochlorine compounds (OCs) and Hg in healthy women recruited during pregnancy. We found a significant negative correlation between maternal total triiodothyronine levels and three non-coplanar congeners (PCB-138, PCB-153, and PCB-180) , three pesticides (p,p´-DDE, cis-nanochlor, and hexachlorobenzene) , and inorganic Hg independently, without any other changes in thyroid status. No significant relationships were observed between OCs and cord serum thyroid hormones. Cord serum free thyroxin was negatively correlated with inorganic Hg. These results suggest that at even low levels of exposure, persistent environmental contaminants can interfere with thyroid status during pregnancy. Key words: cord blood, environment, mercury, pesticide, polychlorinated biphenyls, pregnancy, thyroid. Environ Health Perspect 113:1039-1045 (2005) . doi:10.1289/ehp.7685 available via http://dx.doi.org/ [Online 24 May 2005]

Address correspondence to J. Lafond, Centre de Recherches Biomédicales, Département des Sciences Biologiques, Université du Québec à Montréal C.P. 8888, Succursale Centre-ville, Montréal, Québec, Canada, H3C 3P8. Telephone: (514) 987-3000 ext. 7857. Fax: (514) 987-4647. E-mail: lafond.julie@uqam.ca

This study was funded by the Toxic Substances Research Initiative, Health Canada, and the Collaborative Mercury Research Network of the National Sciences and Engineering Research Council of Canada.

The authors declare they have no competing financial interests.

Received 21 October 2004 ; accepted 23 May 2005.