Patrick W. Bradley

Tree swallow (Tachycineta bicolor) exposure to polychlorinated biphenyls at the Kalamazoo River superfund site, Michigan, USA

In 1990, a portion of the Kalamazoo River in Michigan, USA, was designated a Superfund site because of the presence of polychlorinated biphenyls (PCBs) in the sediment and floodplain soils. During a four-year period from 2000 to 2003, several avian species were monitored for reproductive effects and concentrations of PCBs in tissues attributed to food chain transfer from contaminated sediments. The tree swallow (Tachycineta bicolor) was chosen as a model receptor for contamination of passerine species. A top-down methodology was used to evaluate the bioaccumulation of PCBs, including non-ortho and mono-ortho congeners, in tree swallow eggs, nestlings, and adults at the Kalamazoo River area of concern (KRAOC) and at an upstream reference site. Generally, a sixfold difference in tissue concentrations of total PCBs was observed between the two sites with concentrations in eggs and nestlings at the KRAOC ranging from 0.95 to 15 microg PCB/g wet weight. Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQsWHO Avian) for PCBs, based on bird-specific World Health Organization toxic equivalence factors, were 10- to 30-fold greater in the KRAOC than at the reference location. Egg and nestling TEQsWHO-Avian ranged from 0.21 to 2.4 ng TEQ/g wet weight at the KRAOC. Hazard quotients calculated from literature-derived toxicity reference values were below 1.0 at both the target and the reference site based on the no-observed-adverse-effect level and the lowest-observed-adverse-effect level.

PBDEs and methoxylated analogues in sediment cores from two Michigan, USA, inland lakes

Polybrominated diphenyl ethers (PBDEs) have been widely studied in sediments from the North American Great Lakes; however, no studies have been conducted of occurrences of methoxylated (MeO-) PBDEs in abiotic compartments in this region. In the present study, 23 tri- to hepta-PBDEs and 12 MeO-PBDEs were analyzed in dated sediment cores collected from two inland lakes (White Lake and Muskegon Lake) in Michigan, USA. Concentrations of Σ(23) PBDEs ranged from 3.9 × 10(-1) to 2.4 × 10(0) and from 9.8 × 10(-1) to 3.9 × 10(0) ng/g dry weight in White Lake and Muskegon Lake, respectively. The historical trends of tri- to hepta-PBDEs in the two lakes were different, possibly because of different input and remediation histories. The tri- to hepta-PBDE profiles were similar in the two lakes, with BDE-47 as the predominant congener, followed by BDE-99 and BDE-183. A different temporal trend for BDE-183 was found compared with other PBDEs, which is consistent with debromination of high-brominated PBDEs during sedimentation and aging. Methoxylated-PBDEs were detected only in Muskegon Lake (3.6 × 10(-3) to 1.2 × 10(-1) ng/g dry wt). Methoxylated PBDEs showed different temporal trends compared with tri- to hepta-PBDEs. The differences in patterns of concentrations of MeO-PBDEs in the two lakes might be due to different aquatic communities in each lake. The occurrences of MeO-PBDEs could be the major source of hydroxylated-polybrominated diphenyl ethers (OH-PBDEs) observed in organisms collected in these freshwater systems.

Passerine Exposure to Primarily PCDFs and PCDDs in the River Floodplains Near Midland, Michigan, USA

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 (ΣPCDD/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 ΣPCDD/DFs and sum 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (ΣTEQsWHO-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 ΣPCDD/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 ΣPCDD/DFs and ΣTEQsWHO-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 ΣTEQsWHO-Avian were positively correlated with ΣPCDD/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.

Dietary exposure of three passerine species to PCDD/DFs from the Chippewa, Tittabawassee, and Saginaw River floodplains, Midland, Michigan, USA

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 ΣPCDD/DFs of the major site-specific dietary items collected via food web-based sampling. Average ingestion values of ΣPCDD/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 ΣPCDD/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%).

Accumulation of polychlorinated biphenyls from floodplain soils by passerine birds

Eggs, nestlings, and adults of the eastern bluebird (Sialia sialis) and house wren (Troglodytes aedon) were collected at a polychlorinated biphenyl (PCB)-contaminated site and a reference location on the Kalamazoo River (MI, USA). Eggs and nestlings of eastern bluebirds at the more contaminated location contained concentrations of 8.3 and 1.3 mg/kg, respectively, of total PCBs and 77 and 6.3 ng/kg, respectively, of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs). Eggs, nestlings, and adults of house wrens from the contaminated location contained 6.3, 0.77, and 3.2 mg/kg, respectively, of PCBs and 400, 63, and 110 ng/kg, respectively, of TEQs. Concentrations of total PCBs and TEQs in tissues at the more contaminated location were significantly greater than concentrations in tissues at the reference site for all tissue types of both species. Exposures of the two species studied were different, which suggests that terrestrial-based insectivorous passerine species, foraging in the same area, may have differential exposure to PCBs depending on specific foraging techniques and the insect orders that are targeted. Despite the greater accumulation of PCBs at the more contaminated location, the risk of exposure to PCBs did not exceed the threshold for adverse effects at either location.

Exposure and Multiple Lines of Evidence Assessment of Risk for PCBs Found in the Diets of Passerine Birds at the Kalamazoo River Superfund Site, Michigan

ABSTRACT Dietary exposures of passerine birds at the Kalamazoo River, Michigan, were examined due to the presence of polychlorinated biphenyls (PCBs) in the terrestrial and aquatic food webs. Average potential daily doses in diets were 6- to 29-fold and 16- to 35-fold greater at a contaminated location than at a reference location for PCB exposures quantified as total PCBs and 2,3,7,8–tetrachlorodibenzo-p-dioxin equivalents (TEQs), respectively. Birds with diets comprised of primarily aquatic insects had greater dietary exposure than birds with diets of primarily terrestrial insects. Risk associated with dietary exposure varied with the selection of the threshold for effects including hazard quotients, which exceeded 1 in instances where the most conservative toxicity reference values were utilized. Risk based on concentrations of PCBs in the tissues indicated little risk to avian species, and co-located studies evaluating reproductive health did not suggest that observed incidences of diminished reproductive success were related to PCB exposure. Measures of risk based on comparison to toxicity reference values (TRVs) were consistent with direct measures of ecologically relevant endpoints of reproductive fitness, but uncertainty exists in the selection of threshold values for effects in these species especially based on TEQs. This is largely due to the absence of species-specific, dose-response relationships. Therefore, the best estimate of risk is through the application of multiple lines of evidence.

Dietary‐ and tissue‐based exposure of belted kingfisher to PCDFs and PCDDs in the Tittabawassee River floodplain, Midland, MI, USA

Concentrations of polychlorinated dibenzofurans (PCDFs) and other dioxin-like compounds in soils and sediments of the Tittabawassee River and associated floodplains downstream of Midland, Michigan, USA, are greater than upstream sites. As a result of these concentrations, which are some of the greatest ever reported, a site-specific exposure assessment of belted kingfisher breeding in the assessment area was conducted. To reduce the uncertainty associated with predicting exposure from abiotic matrices, concentrations of residues were quantified in site-specific prey items and in eggs and nestlings of belted kingfisher. Dietary exposure, expressed as the potential average daily dose, based on site-specific concentrations of PCDFs, polychlorinated dibenzo-p-dioxins (PCDDs), and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ(WHO-Avian)) in prey items was consistently greater along the Tittabawassee River than in associated reference areas and further downstream sites in the Saginaw River. Concentrations of PCDD/DFs in eggs and nestlings of belted kingfisher varied among sampling areas, being greater in both eggs and nestlings nesting along the Tittabawassee River compared to those of belted kingfisher from upstream reference areas. Geometric mean concentrations of PCDD/DFs were 130 and 200 ng/kg wet weight in eggs and nestlings of belted kingfisher, respectively. These concentrations are the equivalent of 84 and 95 ng TEQ(WHO-Avian)/kg. Site-specific biomagnification factors for select PCDD/DF congeners ranged from <1.0 to 1.8 in belted kingfisher.

TISSUE-BASED RISK ASSESSMENT OF GREAT BLUE HERON (ARDEA HERODIAS) EXPOSED TO PCDD/DF IN THE TITTABAWASSEE RIVER FLOODPLAIN, MICHIGAN, USA

Concentrations of dioxin-like compounds, primarily polychlorinated dibenzofurans (PCDFs), in soils and sediments of the Tittabawassee River (TR) and associated floodplains downstream of Midland, Michigan, USA, were greater than upstream sites and prompted a site-specific risk assessment of great blue herons (GBH). Tissue exposure of PCDF and polychlorinated dibenzo-p-dioxins (PCDDs) was assessed in multiple GBH tissue types, including blood plasma of adults and eggs, as well as blood plasma, adipose, liver, and muscle of nestlings. Adult GBH exposure was associated with foraging area and age class, with concentrations of PCDD/DF being greater in blood plasma of adult GBH foraging in the TR compared with those foraging in upstream reference areas and in older birds as compared with their younger cohorts. Concentrations of PCDD/DFs and dioxin-like polychlorinated biphenyls (PCBs) in eggs and nestling tissues of GBH collected from rookeries within the TR floodplain were generally similar among rookeries. Mean concentrations of PCDD/DFs in eggs of GBH ranged from 45 to 67 ng/kg, wet weight for the rookeries studied, with a maximum concentration of 210 ng/kg, wet weight observed. Adipose consistently had the greatest concentration of PCDD/DFs of all tissues collected from nestlings of GBH, ranging from 98 to 430 ng/kg, wet weight. Potential for adverse population-level effects from site-specific contaminant exposures were evaluated by comparison with selected toxicity reference values (TRVs). Minimal risk of adverse population-level effects were predicted when exposures measured in tissues of GBH collected from rookeries within the TR were compared with appropriate TRVs. This prediction is consistent with site-specific measures of population condition, which included clutch size and number of nestlings per successful nest.

Risk assessment methodologies for exposure of great Horned Owls (Bubo virginianus) to PCBs on the Kalamazoo River, Michigan

ABSTRACT Dietary exposures of great horned owls (GHO; Bubo virginianus) to polychlorinated biphenyls (PCBs) in the terrestrial food web at the Kalamazoo River, Michigan, USA, were examined. Average potential daily doses (APDD) in GHO diets were 7- to 10-fold and 3-fold greater at the more contaminated location versus a reference location for site-specific exposures quantified as total PCBs and 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQWHO-Avian), respectively. Wetland/aquatic prey contributed significantly to PCB exposure and APDD. Estimates of risk based on comparison of modeled dietary intake (e.g., APDD) to toxicity reference values (TRVs), using a hazard quotient (HQ) methodology, varied between diet composition methods (mass basis vs numeric basis). Mass-basis compositions yielded greater HQs at all sites. Potential risks associated with dietary exposures (“bottom-up” risk assessment methodology) were less than (HQ < 1) benchmarks for effects,. This result is consistent with risk estimates based on concentrations in tissues (“top-down” risk assessment methodology), and indicated PCBs posed no significant risk to terrestrial raptor species. Colocated and concurrent studies that evaluated GHO reproductive performance (nestling productivity) and relative abundance were consistent with results of the risk assessment. Measures of risk based on HQs were consistent with direct measures of ecologically relevant endpoints (reproductive fitness). Uncertainty in risk estimates is contributed during the selection of TRVs for effects in GHO based on TEQWHO-Avian because of the absence of species-specific, dose-response thresholds. This evaluation indicated that a multiple-lines-of-evidence approach provided the best estimate of risk.

Effects of dietary exposure of mink (Mustela vison) to 2,3,7,8-tetrachlorodibenzo-p-dioxin, 2,3,4,7,8-pentachlorodibenzofuran, and 2,3,7,8-tetrachlorodibenzofuran on reproduction and offspring viability and growth

This study assessed the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), 2,3,4,7,8-pentachlorodibenzofuran (PeCDF), and 2,3,7,8-tetrachlorodibenzofuran (TCDF) on the reproductive performance of female mink (Mustela vison) and the viability and growth of their offspring. Nine adult female mink were randomly assigned to one of 13 dietary treatments (one control and four doses each of TCDD, PeCDF, and TCDF [2.1-8.4, 4.0-15 and 5.2-25 ng TCDD toxic equivalents (TEQ)/kg body wt/d]). Diets were fed from two months prior to breeding through weaning of offspring at six weeks of age. At least nine kits per treatment group were maintained on their diets through 27 weeks of age. There were no effects on litter size or viability of offspring. No consistent effects were observed on body mass or relative organ masses of animals at any age. 2,3,7,8-Tetrachlorodibenzo-p-dioxin and PeCDF accumulated in the liver and adipose tissue, but TCDF cleared rapidly. The lack of significant effects on reproduction and offspring viability contrasts with effects reported for mink exposed to environmentally derived PCB mixtures with equivalent TCDD potencies. This suggests that it may be inappropriate to apply toxicity reference values associated with PCB mixtures to animals also exposed to TCDD, PeCDF, or TCDF, and the World Health Organization TCDD toxic equivalency factors for some congeners may not be appropriate for mink.