RESUMO
We studied tree swallows (Tachycineta bicolor) at the Sangamo National Priorities List (NPL) site and a reference area (Little Grassy) within Crab Orchard National Wildlife Refuge, Illinois, USA, to evaluate the bioavailability of polychlorinated biphenyls (PCBs) at the NPL site following remediation. Tree swallow eggs and 12- to 17-d-old chicks were collected from April to June 2004 and 2005. Total egg PCB concentrations in eggs did not differ between years at Sangamo; mean concentrations at Sangamo in 2004 to 2005 (4,452 ng/g) were higher than those from Little Grassy in 2004 (351 ng/g; p = 0.002) and 2005 (705 ng/g; p = 0.007). A positive PCB dilution in chicks is equivalent to relatively large amounts of exposure and absorption. Total PCB daily dilution in chicks in 2004 and 2005 averaged 92.4 and -203 ng/g/d at Sangamo and -21.8 and -42.7 ng/g/d at Little Grassy. Dioxin toxic equivalents (TEQs) in eggs in 2004 and 2005 were 1,844 and 676 pg/g at Sangamo and 165 and 128 pg/g at Little Grassy. Mean TEQs in chicks in 2004 and 2005 were 117 and 23.8 pg/g body weight at Sangamo and 0.8 and 0.7 pg/g body weight at Little Grassy. Total PCB concentrations in eggs and chicks at Sangamo and Little Grassy appeared to be comparable to other PCB-contaminated and reference sites. Our data demonstrate that tree swallows using the Sangamo site continue to accumulate significant quantities of PCBs seven years after remedial actions. These findings prompted a reevaluation of remediation at the site and underscore the importance of postremediation monitoring of ecological receptors, particularly in cases involving persistent environmental contaminants.
