Passerine exposure to primarily PCDFs and PCDDs in the river floodplains near Midland, Michigan, USA

Abstract

House wren (Troglodytes aedon), tree swallow (Tachycineta bicolor), and eastern bluebird (Sialia sialis) tissues collected in study areas (SAs) downstream of Midland, Michigan (USA) contained concentrations of polychlorinated dibenzofurans (PCDFs) and polychlorinated dibenzo-p-dioxins (PCDDs) greater than in upstream reference areas (RAs) in the region. The sum of concentrations of PCDD/DFs (SigmaPCDD/DFs) in eggs of house wrens and eastern bluebirds from SAs were 4- to 22-fold greater compared to those from RAs, whereas concentrations in tree swallow eggs were similar among areas. Mean concentrations of SigmaPCDD/DFs and sum 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (SigmaTEQs(WHO-Avian)), based on 1998 WHO avian toxic equivalency factors, in house wren and eastern bluebird eggs ranged from 860 (430) to 1500 (910) ng/kg wet weight (ww) and 470 (150) to 1100 (510) ng/kg ww, respectively, at the most contaminated study areas along the Tittabawassee River, whereas mean concentrations in tree swallow eggs ranged from 280 (100) to 760 (280) ng/kg ww among all locations. Concentrations of SigmaPCDD/DFs in nestlings of all studied species at SAs were 3- to 50-fold greater compared to RAs. Mean house wren, tree swallow, and eastern bluebird nestling concentrations of SigmaPCDD/DFs and SigmaTEQs(WHO-Avian) ranged from 350 (140) to 610 (300) ng/kg ww, 360 (240) to 1100 (860) ng/kg ww, and 330 (100) to 1200 (690) ng/kg ww, respectively, at SAs along the Tittabawassee River. Concentrations of SigmaTEQs(WHO-Avian) were positively correlated with SigmaPCDD/DF concentrations in both eggs and nestlings of all species studied. Profiles of relative concentrations of individual congeners were dominated by furan congeners (69-84%), primarily 2,3,7,8-tetrachlorodibenzofuran and 2,3,4,7,8-pentachlorodibenzofuran, for all species at SAs on the Tittabawassee and Saginaw rivers but were dominated by dioxin congeners at upstream RAs.

Fig. 1

Study site locations within the Chippewa River, Tittabawassee River, and Saginaw River floodplains, Michigan (USA) Reference areas (R-1 to R-2), Tittabawassee River study areas (T-3 to T-6), and Saginaw River study areas (S-7 and S-9) were monitored from 2005 to 2007. The direction of river flow is designated by arrows; suspected source of contamination is enclosed in the dashed oval

Fig. 2

Range and mean of ΣPCDD/DF concentrations in live and addled eggs of house wrens, tree swallows, and eastern bluebirds collected in 2005–2007 near Midland, Michigan. Sample size is indicated for each area with at least two samples collected. R-1 to R-2 = reference areas; T-3 to T-6 = Tittabawassee River study areas; S-7 and S-9 = Saginaw River study areas; *p < 0.05

Fig. 3

PCA of PCDD/DF concentration congener profiles in eggs and nestlings of house wrens (HW), tree swallows (TS), and eastern bluebirds (EB) collected in 2005–2007 near Midland, Michigan. Individual PCDD/DF congener loading scores for each principle component is depicted in the inset. R = reference area; T = Tittabawassee River study area; S = Saginaw River study area; TCDF = tetrachlorodibenzofuran; PeCDF = pentachlorodibenzofuran; HxCDF = hexachlorodibenzofuran; HpCDF = heptachlorodibenzofuran; OCDF = octachlorodibenzofuran; TCDD = tetrachlorodibenzo-p-dioxin; PeCDD = pentachlorodibenzo-p-dioxin; HxCDD = hexachlorodibenzo-p-dioxin; HpCDD = heptachlorodibenzo-p-dioxin; OCDD = octachlorodibenzo-p-dioxin

Fig. 4

Mean congener percent contributions in eggs and nestlings of house wrens, tree swallows, and eastern bluebirds collected in 2005–2007 near Midland, Michigan. R-1 to R-2 = reference area; T-3 to T-6 = Tittabawassee River study area; TCDF = tetrachlorodibenzofuran; PeCDF = pentachlorodibenzofuran; HxCDF = hexachlorodibenzofuran; HpCDF = heptachlorodibenzofuran; OCDF = octachlorodibenzofuran; TCDD = tetrachlorodibenzo-p-dioxin; PeCDD = pentachlorodibenzo-p-dioxin; HxCDD = hexachlorodibenzo-p-dioxin; HpCDD = heptachlorodibenzo-p-dioxin; OCDD = octachlorodibenzo-p-dioxin

Fig. 5

Correlation plots of ΣPCDD/DFs and TEQ_WHO-Avian for (a) house wrens eggs, (b) house wren nestlings, (c) tree swallow eggs, (d) tree swallow nestlings (note: axis breaks), (e) eastern bluebird eggs, and (f) eastern bluebird nestlings collected in 2005–2007 near Midland, Michigan with indications of R values, p-values and sample size. 1 = R-1; 2 = R-2; 3 = T-3; 4 = T-4; 5 = T-5; 6 = T-6; 7 = S-7; 9 = S-9