Multiple Lines of Evidence Risk Assessment of Terrestrial Passerines Exposed to PCDFs and PCDDs in the Tittabawassee River Floodplain,Midland, Michigan, USA

摘要

A site-specific multiple lines of evidence risk assessment was conducted for house wrens {Trogbdytesaedon) and eastern bluebirds (Sialiasialis) along the Tittabawassee River downstream of Midland, Michigan, where concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) in flood-plain soils and sediments are greater compared to upstream areas and some of the greatest anywhere in the world. Lines of evidence supporting the population-level assessment endpoints included site-specific dietary- and tissue-based exposure assessments and population productivity measurements during breeding seasons 2005-2007. While a hazard assessment based on site-specific diets suggested that populations residing in the downstream floodplain had the potential to be affected, concentrations in eggs compared to appropriate toxicity reference values (TRVs) did not predict a potential for population-level effects. There were no significant effects on reproductive success of either species. The most probable cause of the apparent difference between the dietary- and tissue-based exposure assessments was that the dietary-based TRVs were overly conservative based on intraperitoneal in-jections in the ring-necked pheasant.Agreement between the risk assessment based on concentrations of PCDFs and PCDDs in eggs and reproductive performance in both species supports the conclusion of a small potential for population-level effects at this site.