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Heart Defects Discovered in Songbirds from Polluted Areas
Date Posted: March 13, 2006In 1995, contaminants biologists from the Bloomington, Indiana, Field Office (BFO) and researchers from Indiana University began studying songbirds at several Polychlorinated Biphenyl (PCBs) contaminated sites and at a reference site in Monroe and Lawrence Counties, Indiana. Our preliminary evaluations of heart development in passerines from these PCB contaminated sites summarized in 1997 indicated that virtually all species studied (eastern bluebirds, Carolina chickadees, house wrens, red-winged blackbirds, and tree swallows) were sensitive to the cardiotoxic effects of PCBs. This study was conducted to quantify and provide a detailed evaluation of the PCB-induced cardiac teratogenicity (defects in a developing young) in the five passerine species exposed under field conditions. Our goals were to methodically describe a suite of observable cardiac deformities and changes in heart shape and size in birds; and to show a relationship between each deformity and change and total PCBs and dioxin-like compounds by species, establishing the relative sensitivity of each passerine species.
The BFO work has just been published in the February edition of Environmental Toxicology and Chemistry, a publication of the Society of Environmental Toxicology and Chemistry. This work is important for two reasons. It was documented in the 1970s that these types of cardiac effects occurred in chickens fed PCB contaminated feed. Laboratory chicken studies evaluating the effects of PCBs and dioxin also produced these types of cardiac deformities. It has been widely accepted (and perhaps in error) that chickens must be more sensitive to these type of cardiac effects than other birds. Prior to this study, no one had looked for these cardiac effects in passerine field studies. Secondly, this study confirms that significant adverse impacts can occur to passerines at concentrations below those known to cause a reduction in hatching success.