Early Exposure to a Brominated Flame Retardant (BDE-99): An Assessment of Long-term Effects Using an Integrated Laboratory and Field Avian Model System

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Polybrominated diphenyl ethers
Passerine birds
Developmental effects
Maternal transfer

Polybrominated diphenyl ethers (PBDEs) are a group of hydrophobic and bioaccumulative chemicals that have been widely used as additive flame retardants(Hites 2004). 2,2’,4,4’,5-Pentabromodiphenyl ether (BDE-99) is one of the major constituents of the commercial penta-BDE flame retardant mixture, and is consistently found in avian tissue and egg samples throughout the world. It is known to cause a wide range of adverse effects in mammals, yet its effects in birds are not well known due to a lack of toxicological literature. Developmental life stages tend to be the most sensitive to environmental contaminants, and effects of early exposure may not be evident until reproductive maturity, necessitating long term studies to assess fitness implications of contaminant exposure. The objectives of this project were to develop an integrated field and lab avian monitoring system to assess the long-term effect of early exposure to BDE-99, using the zebra finch (Taeniopygia guttata) in the lab and the European starling (Sturnus vulgaris) in the field as model passerine species. I exposed nestlings to sub-lethal BDE-99 concentrations, and birds were raised to reproductive maturity to assess a range of endpoints, including neuroanatomy, behavior, physiology, growth, survival, reproductive development, and reproductive success. I also measured concentrations of persistent organic pollutants in free-living starling eggs and related concentrations to adult and nest conditions. In addition, I characterized the maternal transfer of BDE-99 from mothers to eggs in the zebra finch. Behavior was the most sensitive BDE-99 exposure, with the number of males that participated in courtship or singing behaviour being significantly reduced in the highest dose groups. There were few other overt effects of BDE-99 exposure in either zebra finches or starlings. PBDE concentrations in free-living starlings were highly variable, but at the observed concentrations there was no relationship between PBDEs and nest condition or reproductive success. Maternal transfer of BDE-99 is related to individual variation in BDE-99 plasma burden and lipid status, and involves a saturable transport process. Overall, these studies provide insight into the long-term effects of nestling exposure to BDE-99 in passerine birds, the concentrations and effects in free-living terrestrial passerines, and the maternal transfer process.

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Tony D. Williams
Science: Biological Sciences Department
Thesis type: 
(Thesis) Ph.D.