American Journal of Epidemiology Advance Access originally published online on June 10, 2008
American Journal of Epidemiology 2008 168(3):298-310; doi:10.1093/aje/kwn136
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ORIGINAL CONTRIBUTIONS |
Effects of Exposure to Polychlorinated Biphenyls and Organochlorine Pesticides on Thyroid Function during Pregnancy
1 Center for Children's Environmental Health Research, School of Public Health, University of California, Berkeley, Berkeley, CA
2 Division of Epidemiology, School of Public Health, University of California, Berkeley, Berkeley, CA
3 Division of Environmental Health Sciences, School of Public Health, University of California, Berkeley, Berkeley, CA
4 National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, GA
Correspondence to Dr. Brenda Eskenazi, Center for Children's Environmental Health Research, School of Public Health, University of California, Berkeley, 2150 Shattuck Avenue, Suite 600, Berkeley, CA 94704-7380 (e-mail: eskenazi{at}berkeley.edu).
Received for publication September 4, 2007. Accepted for publication April 28, 2008.
In this study, the authors' objective was to determine whether serum concentrations of polychlorinated biphenyls (PCBs), hexachlorobenzene, p,p'-dichlorodiphenyl trichloroethane (DDT), o,p'-DDT, and p,p'-dichlorodiphenyl dichloroethylene (DDE) are associated with thyroid function during pregnancy. These compounds, as well as thyroid-stimulating hormone, total thyroxine, and free thyroxine, were measured in serum samples collected between October 1999 and October 2000 from 334 pregnant women living in the Salinas Valley, California. Data were analyzed by multivariate linear regression. After adjustment for covariates, seven of the 19 PCB congeners detected in more than 75% of participants and the sum of those congeners were negatively associated with free thyroxine concentrations. PCBs 44, 52, and 183 remained significant after the exclusion of two outliers. Hexachlorobenzene concentrations were negatively associated with both free thyroxine and total thyroxine. PCB and hexachlorobenzene concentrations were strongly correlated, which hampered the authors' ability to identify their independent associations with thyroid function. None of the exposures under study were associated with thyroid-stimulating hormone. Results suggest that exposure to PCBs and/or hexachlorobenzene at background levels may affect thyroid function during pregnancy. These findings are of particular significance, since thyroid hormones of maternal origin may play an essential role in fetal neurodevelopment.
DDT; dichlorodiphenyl dichloroethylene; hexachlorobenzene; hydrocarbons, chlorinated; polychlorinated biphenyls; pregnancy; thyroid hormones
Abbreviations: CHAMACOS, Center for the Health Assessment of Mothers and Children of Salinas; CI, confidence interval; DDE, dichlorodiphenyl dichloroethylene; DDT, dichlorodiphenyl trichloroethane; NHANES III, Third National Health and Nutritional Examination Survey; PCB(s), polychlorinated biphenyl(s)