Abstract
ABSTRACT
In recent years, endocrine-disrupting activities by chemical emissions from combustion sources have generated considerable interest in the scientific community. Polychlorinated dibenzodioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) emitted from combustion sources form a big group of extremely persistent and widely distributed toxic chemicals in the environment. Exposures to these chemicals occur through the food web. The residues of these chemicals have been detected in air, soil, sediment, fish, meat, dairy products, human adipose tissue, and mother's milk. The residues of PCBs and their metabolites are widely distributed in breast milk of mothers from industrial countries at concentrations that are about 10,000 times greater than the total levels of PCDDs/PCDFs. Ortho-substituted nonplanar PCBs are the primary PCB congeners that tend of-bioaccumulate more in human milk than coplanar PCBs. In general, these chemicals are characterized by their high lipophilicity and long elimination half-lives. Disruption of the normal homeostasis of the endocrine functions can result in developmental, reproductive, neurotoxic, carcinogenic, immunotoxic, and other adverse health effects. The mechanisms of endocrine disruptive actions of these chemicals are not well understood. It is not known as to whether these chemicals act directly as hormones or modify the endocrine systems by binding to endocrine receptor sites. Disruption of normal endocrine-regulated functions by these chemicals represents an important consideration in risk assessment. An attempt has been made in this paper to examine direct or indirect impact of endocrine disrupting activities of ortho-substituted nonplanar PCBs and present a rationale for risk assessment.
Key words:
Endocrine-disrupting chemicals; PCBs; breast milk; risk assessment
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