Concentrations and spatial patterns of organic contaminants in tree swallow (Tachycineta bicolor) eggs at United States and binational Great Lakes Areas of Concern, 2010–2015

Christine M. Custer, Thomas W. Custer, Paul M. Dummer, Diana Goldberg, J. Christian Franson

Tree swallows, Tachycineta bicolor, were sampled across the Great Lakes' basin in 2010-2015 to provide a system-wide assessment of current exposure to organic contaminants. These results provide information identified as critical by regulators to assess the 'Bird or Animal Deformity or Reproductive Problems' Beneficial Use Impairment. Eggs were collected from 69 sites across all five Great Lakes, including 27 Areas of Concern (AOCs), some with multiple sites, and ten sites not listed as an AOC. Concentrations of organic contaminants in eggs were quantified and compared to background and reproductive effect thresholds. Approximately 30% of AOCs had geometric mean concentrations of total polychlorinated biphenyls (PCBs) at or below average background exposure (0.34 μg/g wet wt.). Exposure to polybrominated diphenyl ethers (PBDEs) was minimal, and only three of 27 AOCs and one non-AOC had geometric mean concentrations that exceeded background for tree swallows (96 ng/g wet wt.). Concentrations of both PCBs and PBDEs were 10-20 times below the lower limit associated with impaired hatching success. In contrast, geometric mean concentrations of dioxin and furan (PCDD-F) toxic equivalents (TEQs) at Saginaw River and Bay AOC and Midland, MI, a non-AOC site, exceeded the lower limit for hatching effects (181 pg/g PCDD-F TEQs). The rest of the sites had geometric mean concentrations of PCDD-F TEQs below background levels (87 pg/g PCDD-F TEQs). Other organic contaminants, including p,p'-dichlorodiphenyl-dichloroethylene (DDE), mirex, heptachlor, and chlordane, were at or below background, or adverse effect concentrations. This article is protected by copyright. All rights reserved.