Academic journal article Environmental Health Perspectives

A Reason to Rethink Groups: New Approach Links PCBs, Thyroid Disruption

Academic journal article Environmental Health Perspectives

A Reason to Rethink Groups: New Approach Links PCBs, Thyroid Disruption

Article excerpt

The production of polychlorinated biphenyls (PCBs), once widely used in electrical transformers, plastics, and other products, has been banned in the United States since the 1970s. Nevertheless, most Americans carry measurable levels of PCBs because the compounds persist in the environment and bioaccumulate. Epidemiologic studies have linked prenatal PCB exposure with impaired neurodevelopment in infants and young children, and in animal studies, prenatal exposure caused decreased levels of the thyroid hormone thyroxine ([T.sub.4]). Given that thyroid hormones are essential for proper neurodevelopment, disruption of the thyroid system may be a pathway by which PCBs cause damage. New research using a novel method of grouping the chemicals now provides additional support for PCBrelated thyroid disruption [EHP 115:1490-1496; Chevrier et al.].

PCBs include 209 congeners that vary based on the number and positions of chlorine atoms. These congeners have been grouped according to their potential mechanism of action (e.g., estrogenicity, antiestrogenicity, or microsomal enzyme induction). In the current study, researchers grouped congeners on the basis of their reported abilities to induce the enzymes UDP-GT, CYP1A, and CYP2B. UDP-GT has a role in [T.sub.4] elimination, and compounds that induce CYP1A and CYP2A are also likely to induce UDP-GT.

Thirty-four PCB congeners, in addition to other environmental chemicals, were measured in blood samples drawn from 285 pregnant women through the Center for the Health Assessment of Mothers and Children of Salinas, a longitudinal birth cohort study in the Salinas Valley, California. …

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