NIEHS Superfund Basic
Research Program (1994)

Research Program - Biomedical Highlights

NOTE: Some of the information in this file was downloaded from the NIEHS Superfund WWW Site. Headers were inserted to make it easier to scan the biomedical highlights.

PCB Levels in Human milk study from the Netherlands

Levels of PCBs, PCDDs and PCDFs in Human milk. Results from the Second Round of a WHO-coordinated Exposure Study. A.K.D. Liem et al.

WHO European Centre for Environment and Health
PO Box 10
NL-3730 AA De Bilt, Netherlands
email : eceh@who.nl

Source : WHO - 16th Symposium on Chlorinated Dioxins and Related Compounds - Amsterdam,

Exposure of Neutrophils to PCB

Researchers are studying the ability of selected chemicals to alter the function of neutrophils in the tissue inflammatory response. Initial experiments indicated that napthalene and phenanthrene were not capable of altering neutrophil function. Recent studies indicate that exposure of neutrophils to PCBs can alter the normal response of these cells. Neutrophil response to other activating compounds was found to be less in the presence of PCBs. These results suggest that exposure to PCBs may alter the response of animals to other toxicants. Because neutrophils can be involved in a beneficial immune response and conversely a tissue injuring inflammatory response, the ability of PCBs to alter the function of these important cells bears further investigation. (P42 ES04911 - Roth)

PCB and Neurotoxicity

In a study comparing effects of perinatal as compared to adult exposure to PCBs, researchers have found that neurotoxicity is expressed in diametrically opposite ways. In adults, ortho-PCBs reduce brain dopamine levels while dioxin-like coplanars are inactive. However, following perinatal exposure, dioxin-like PCBs elevate brain dopamine concentrations and alter the behavior of exposed female offspring while ortho-PCBs reduce brain dopamine concentrations. Thus, important variables include the age at exposure and the class of congeners to which the organism is exposed. These results suggest that PCBs may not only directly affect neurotransmitter function, but may also alter steroid hormone function during development. (P42 ES04913 - Seegal)

Immunotoxicologic Responses of Dogs to PCB Exposure

Researchers have demonstrated a high degree of correspondence between laboratory and field outcomes in immunotoxicologic responses of dogs to PCB exposure. Not only have these studies elucidated effects of PCBs on the immune functions, but they have sparked a number of spin-off studies involving the thyroid, control of lymphocyte (white blood cell) development, and brain function. These responses may show how PCBs affect behavior, physiology, and response to infectious disease and environmentally induced threats such as concer. Efforts to date are a key step in validating laboratory immunotoxicologic observations with field studies of companion animal health. (P42 ES05950 - Quimby)

Toxic Halogenated Aromatic Compounds - Mechanism of Action

Investigators have confirmed the receptor-mediated mechanism of action of toxic halogenated aromatic compounds (HAHs) and, based on their common mechanism of action, toxic equivalency factors (TEFs) relative to 2,3,7,8-TCDD have been developed and used for risk management of these compounds. Structure-toxicity studies for PCBs, higher chlorinated PCDFs and polychlorinated diphenylethers (PCDEs) have been completed and TEF values have been assigned to the relevant congeners. The TEF approach has been adopted worldwide by numerous regulatory agencies for hazard and risk assessment of PCDDs, PCDFs, PCBs and related compounds. Research on the validation and limitations of this approach to the risk management of HAH mixtures is ongoing. (P42 ES04917 - Safe)

ATSDR: Public Health Actions and Findings

Congressional Testimony

by
Barry L. Johnson, Ph.D.
Assistant Surgeon General
Assistant Administrator
Agency for Toxic Substances and Disease Registry

Levels from the National Human Adipose Tissue Survey1 of various dioxins (e.g., 2,3,7,8-tetrachlorodibenzo-dioxin), dibenzofurans, DDT and metabolites, and PCBs indicate considerable body burdens. These levels may now be in a range that raises concern about health endpoints such as neurologic, neuroendocrine, and immunologic effects. We belatedly decided to control the source of production for some of these chemicals. Unfortunately, for many decades to come, we will be dealing with the literal residues of these chemicals in the environment, in such vectors as fish, and in our own tissues (Silbergeld and deFur, in press).

A study of the Mohawk Tribe at a NPL site in New York documented that women who consumed local fish from polychlorinated biphenyl (PCB)-contaminated waters had significantly higher concentrations of PCBs in their breast milk. Effect on Exposure Assessment of Variability in Estimated Half-Lives of PCBs in Humans ATSDRs