INSIGHTS ALONG THE PATH TO SUSTAINABILITY| November 30, 2005 The Effects of Brominated Flame Retardants (PBDEs) on Thyroid Hormone Status, Birthweight and Gestational Age LYNN R. GOLDMAN, MD, MPH, Professor, Department of Environmental Health Sciences, JHSPH
JULIE HERBSTMAN, ScM, Doctoral Candidate, Department of Epidemiology, JHSPH (Presenter) SUMMARY
Introduction Polybrominated diphenyl ethers (PBDEs) are commonly used as flame retardants on electronic equipment and textiles. Their propensity to leach off their base product has rendered them ubiquitous in the environment, wildlife, and human biota. PBDEs are similar to polychlorinated biphenyls (PCBs) in their chemical structure and ability to bioaccumulate. However, while environmental concentrations of other persistent organic pollutants (POPs) are falling, PBDE levels in the environment have been increasing exponentially since the 1970’s. The primary route of human exposure is through the diet. Following maternal dietary exposure, fetuses are exposed, as these chemicals can readily cross the placental barrier. Toxicological models have indicated that the most sensitive health endpoints associated with PBDE exposure are potential effects on thyroid function. In humans, thyroid hormone levels are especially important during the third trimester of pregnancy throughout the first two years of life, when rapid growth and development of the brain occurs. The proposed study focuses on the critical gap in our scientific understanding of the health effects associated with prenatal exposure to both PCBs and PBDEs. Methods This study is cross-sectional in design. Three hundred umbilical cord blood samples were collected from a sample of all singleton deliveries at the Johns Hopkins Hospital between November 26, 2004 and March 17, 2005. Cord blood from all mothers wishing to personally save and bank the blood was excluded from collection. The protocol for this study has been reviewed and approved by both the Johns Hopkins School of Medicine IRB as well as the Maternal and Fetal Research Committee. The cord samples were spun and the serum aliquotted into various storage vials to be sent to the Centers for Disease Control and Prevention for PCB and PBDE congener analyses and to Quest diagnostics for levels of thyroid hormone parameters. Results (to date) Umbilical cord blood samples have been collected from 300 infants. An examination of demographic and medical information indicates that our sample is representative of the deliveries at the Johns Hopkins Hospital. Thyroid levels in this population are quite variable, allowing for the detection of differences in thyroid parameters by PCB and PBDE concentration levels, should they exist. Preliminary PCB and PBDE analyses of 21 samples show that levels of these two compounds are not correlated in our sample, indicating that the routes of exposure may differ. Our sample has, on average, PBDE levels that are lower than those found in a small sample of cord blood collected in Indiana (n=12) in 2001 but over 10 times the levels found in Swedish cord blood collected in 2001. Discussion Early fetal growth and development has a profound effect on health throughout the lifespan. It is important not only to protect the food supply from contamination but also to assure that consumers are informed about the hazards of foods, including PBDEs. In the case of PBDEs, the continued lack of regulation in the US, along with the high consumption of animal products, is exposing the fetus and child to unknown risks. This research will contribute to the weight of the evidence that may be used to move towards regulating the production of PBDEs in the U.S. In the mean time, it is important to heed the example of the European Union in taking precautionary measures to reduce PBDE exposures to children.
PRESENTER BIOGRAPHY
Julie Herbstman received her undergraduate degree from Tufts University in 1998 in Comparative Religion and Civil Engineering. She then worked for at the Silent Spring Institute, a non-profit research organization focusing on the link between the environment and women’s health and also at the Nurses’ Health Study, a large prospective cohort study examining risk factors for major chronic diseases in women. In 2000, she began her masters of science in epidemiology at the Bloomberg School of Public Health. Her research focused on the respiratory health effects among trade workers at the World Trade Center disaster site. She matriculated into the doctoral program in epidemiology in 2002 where her dissertation is examining the health effects following prenatal exposure to polybrominated diphenyl ethers. |
