RP9 Terrestrial Ecotoxicology
Thursday, 17 November 2005: 8:00 AM - 6:30 PM in Exhibit Hall

(COE-1122-405963) PCDDs and PCDFs in Small Mammals Foraging in the Tittabawassee River Floodplain, Michigan.

Coefield, S¹, Zwiernik, M¹, Seston, R¹, Fredricks, T¹, Moore, J¹, Tazelaar, D¹, Kay, D², Jones, P², Bradley, P¹, Giesy, J¹, ¹ National Food Safety and Toxicology Center, Center for Integrative Toxicology, Zoology Department, Michigan State University, East Lansing, MI, USA² ENTRIX, Inc, Okemos, MI, USA

ABSTRACT- The Tittabawassee River located in central Michigan is known to contain elevated concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in sediments, floodplain soils, and fish downstream of Midland, MI. The Aquatic Toxicology Laboratory at Michigan State University is investigating the impact of this contamination on the terrestrial ecosystem, using the Great Horned Owl (GHO) and insectivorous shrews as indicator species. Mammals, including herbivorous small mammals (chipmunks, mice, voles, and flying squirrels) and insectivorous shrews were sampled at two locations upstream and four locations downstream of Midland from 2003-2004. The results from the mammal data will be used in part to extrapolate GHO dietary exposure to PCDF/DDs. Total concentrations of seventeen 2,3,7,8 PCDD/PCDF congeners, expressed as avian TEQs, ranged from 0.228-4.61 ng/kg, ww, for herbivorous small mammals and 0.38-25.3 ng/kg, ww, for insectivorous shrews at the reference area. Avian TEQs downstream of Midland ranged from 3.48-880 ng/kg, ww, for herbivorous small mammals and 22.9-8790, ww, ng/kg for shrews. The significant difference between the shrew and concentrations in other small mammals is due to their different diets and underlines the importance of dietary composition in determining contaminant exposure.

Key words: dioxin equivalents, PCDD/PCDF, dietary composition, contaminant exposure