Field and Laboratory Studies of the Effects of Polychlorinated Biphenyls and Other Persistent Organic Pollutants on Thyroid Function During Avian DevelopmentEPA Grant Number: R827400
Title: Field and Laboratory Studies of the Effects of Polychlorinated Biphenyls and Other Persistent Organic Pollutants on Thyroid Function During Avian Development
Investigators: McNabb, F.M. Anne
Institution: Virginia Polytechnic Institute and State University
EPA Project Officer: Carleton, James N
Project Period: August 1, 1999 through July 31, 2001 (Extended to December 31, 2003)
Project Amount: $256,587
RFA: Endocrine Disruptors (1999) RFA Text | Recipients Lists
Research Category: Economics and Decision Sciences , Health , Safer Chemicals , Endocrine Disruptors
The objectives of this study are (1) to evaluate the current status of thyroid function in developing Herring gulls (Larus argentatus) from Great Lakes sites with different chemical pollutant exposures and (2) to determine, using laboratory studies on developing chickens (Gallus domesticus), if the disruption of avian thyroid function by polychlorinated biphenyls (PCBs; key contaminants at many Great Lakes sites) is similar mechanistically to that in laboratory mammals. Herring gulls, a fish-eating, top-predator, have been used as a sentinel species to monitor the concentrations and biological effects of environmental contaminants in the Great Lakes for more than 25 years. Past research has focused on mortality, developmental abnormalities and reproductive effects of chemical pollutants in the lakes. Studies of thyroid histology and developmental effects suggest that thyroid function is disrupted in these gulls. This study examines the thyroid status of developing gulls in the Great Lakes and employs a laboratory model and specific PCB congeners (PCBs are key contaminants in the lakes) to examine the mechanisms whereby PCBs may disrupt thyroid function in birds (oviparous vertebrates) in comparison to their known mechanisms of disruption in mammals.
This study will assess a number of thyroid-related parameters in both developing Herring gulls from wild populations and chicken embryos and chicks from eggs treated with specific PCB congeners and combinations of those congeners in the laboratory. Field studies will utilize gull populations from the Great Lakes, sampled by Fox and Grasman, laboratory studies will utilize embryos and chicks from eggs treated in the laboratory by Grasman which will also be the subject of immunotoxicology assessments. We will assess thyroid function on the basis of measurements of plasma thyroid hormones, thyroid gland-thyroid hormone content, brain 5'D-II thyroid hormone activation, liver glucuronidation of thyroid hormones and alterations in the binding protein transport of thyroid hormones in the blood.
This work will determine if the thyroid function of Herring Gull embryos and mature chicks, from Great Lakes populations is altered at sites with heavy chemical pollutant exposure compared to those from sites with less pollution and will aid our understanding of the mechanisms of avian thyroid disruption by PCBs, which are key candidates for causing pollutant effects on thyroid function. These studies will provide fundamental information about the magnitude and nature of thyroid alterations in populations of Herring gulls in the Great Lakes and about the mechanisms of such disruption and the degree of adaptive responses to compensate for disruption that occur in some avian species of oviparous vertebrates. These studies are critical background to designing studies of the target organ effects on development of this type of endocrine disruption for use in risk assessments.