In 1995, contaminants biologists from the Bloomington Indiana Ecological Services Field Office and researchers from Indiana University began studying songbirds at several PCB contaminated sites, and at a reference site in Monroe and Lawrence Counties, Indiana.  Organ growth and development in passerines from PCB contaminated sites was altered in all species studied (eastern bluebirds, Carolina chickadees, house wrens, red-winged blackbirds, and tree swallows).  This study was our first to indicate that adverse impacts can occur to passerines at concentrations below those known to cause a reduction in hatching success, a more commonly studied endpoint.   In last month's Accomplishment Report, we shared the results of the more definitive follow up study concerning the PCB-induced cardiac teratogenicity in these five species exposed under field conditions.

This first of the series of articles was recently published in Ecotoxicology. This work is important for several reasons. According to the Natural Resource Damage Assessment regulations (43 CFR 11.64), soft tissue malformations are considered injury in animals.  Although this study by itself may not make an injury determination definitive in Court, it opens the door to the need to look in detail at what we know and don't know in the realm of avian risk assessment and ecotoxicology.  Certainly the more in-depth cardiotoxicity research in birds constitutes injury with regards to the existing regulations.  Without a doubt, effects can be seen in birds nesting in and adjacent to contaminated areas. However, even chronic exposures from migrating through contaminated areas can be enough for these effects to be observed in birds nesting many miles from the contamination.  This is because some of the most toxic PCB congeners (measured as toxic equivalents [TEQs] of dioxin) can bioaccumulate and persist to be deposited in eggs at a later date (and correlate significantly with TEQs).