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Dietary exposure of three passerine species to PCDD/DFs from the Chippewa, Tittabawassee, and Saginaw River floodplains, Midland, Michigan, USA |
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| Authors: | Timothy B. Fredricks John P. Giesy Sarah J. Coefield Rita M. Seston Melissa M. Haswell Dustin L. Tazelaar Patrick W. Bradley Jeremy N. Moore Shaun A. Roark Matthew J. Zwiernik |
| Affiliation: | 1. Department of Zoology, Michigan State University, East Lansing, MI, 48824, USA 2. Bayer CropScience, Ecotoxicology, 17745 South Metcalf, Stilwell, KS, 66085, USA 3. Department of Veterinary Biomedical Sciences and Toxicology Centre, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7J 5B3 4. Department of Biology and Chemistry, City University of Hong Kong, Kowloon, Hong Kong SAR, China 5. College of Environment, Nanjing University of Technology, Nanjing, 210093, People??s Republic of China 6. Key Laboratory of Marine Environmental Science, College of Oceanography and Environmental Science, Xiamen University, Xiamen, People??s Republic of China 7. Science Department, Davenport University, Midland, MI, 48640, USA 8. Department of Animal Science, Michigan State University, East Lansing, MI, 48824, USA 9. ENTRIX, Inc., Okemos, MI, 48864, USA |
| Abstract: | Dietary exposure of house wrens (Troglodytes aedon), tree swallows (Tachycineta bicolor), and eastern bluebirds (Sialia sialis) to polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) near Midland, Michigan (USA) was evaluated based on site-specific data, including concentrations of residues in bolus samples and individual invertebrate orders and dietary compositions by study species. Site-specific dietary compositions for the three species were similar to those reported in the literature, but differed in their relative proportions of some dietary items. Oligocheata (non-depurated) and Brachycera (Diptera) contained the greatest average concentrations of ??PCDD/DFs of the major site-specific dietary items collected via food web-based sampling. Average ingestion values of ??PCDD/DFs from site-specific bolus-based and food web-based dietary concentrations for nestlings at study areas (SAs) were 6- to 20-fold and 2- to 9-fold greater than at proximally located reference areas (RAs), respectively. Average ingestion values of total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQWHO???Avian) from site-specific bolus-based and food web-based dietary concentrations for nestlings at SAs were 31- to 121-fold and 9- to 64-fold greater than at proximally located RAs, respectively. Estimates of ??PCDD/DFs and TEQWHO???Avian tissue concentrations based on nestling dietary exposures were greater than those measured. Plausible explanations include nestling metabolism of 2,3,7,8-tetrachlorodibenzofuran and assimilation rates of less than the 70% assumed to occur over the nestling growth period. Profiles of the relative concentrations of individual PCDD/DF congeners in samples of invertebrates and bolus at SAs on the Tittabawassee River downstream of the source of contamination were dominated by 1,2,3,4,6,7,8,9-octachlorodibenzo-p-dioxin (22% to 44%) and 2,3,7,8-tetrachlorodibenzofuran (18% to 50%). |
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