Environmental Toxicology RISK ASSESSMENT OF GREAT HORNED OWLS (BUBO VIRGINIANUS) EXPOSED TO POLYCHLORINATED BIPHENYLS AND DDT ALONG THE KALAMAZOO RIVER, MICHIGAN, USA

Abstract-The great horned owl (GHO; Bubo virginianus) was used in a multiple lines of evidence study of polychlorinated biphenyls (PCBs) and p,pЈ-dichlorodiphenyltrichloroethane (DDT) exposures at the Kalamazoo River Superfund Site (KRSS), Kalamazoo, Michigan, USA. The study examined risks from total PCBs, including 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ World Health Organization [WHO]-Avian Toxicity Equivalency Factor [TEF] ), and total DDTs (sum of DDT, dichlorodiphenyldichloroethylene [DDE], and dichlorodiphenyldichloroethane [DDD]; ⌺DDT) by measuring concentrations in eggs and nestling blood plasma in two regions of the KRSS (upper, lower) and an upstream reference area (RA). An ecological risk assessment compared concentrations of the contaminants of concern (COCs) in eggs or plasma to toxicity reference values. Productivity and relative abundance measures for KRSS GHOs were compared with other GHO populations. Egg shell thickness was measured to assess effects of p,pЈ-DDE. The concentrations of PCBs in eggs were as great as 4.7 ϫ 10 2 and 4.0 ϫ 10 4 ng PCB/g, wet weight at the RA and combined KRSS sites, respectively. Egg TEQ WHO-Avian calculated from aryl hydrocarbon receptor-active PCB congeners and WHO TEFs ranged to 8.0 and 1.9 ϫ 10 2 pg TEQ WHO-Avian /g, (wet wt) at the RA and combined KRSS, respectively. Egg ⌺DDT concentrations were as great as 4.2 ϫ 10 2 and 5.0 ϫ 10 3 ng ⌺DDT/g (wet wt) at the RA and combined KRSS, respectively. Hazard quotients (HQs) for the upper 95% confidence interval (UCI) (geometric mean) and least observable adverse effect concentration (LOAEC) for COCs in eggs were Յ1.0 for all sites. Hazard quotient values based on the no observable adverse effect concentration (NOAEC) 95% UCI in eggs were Յ1.0, except at the LKRSS (PCB HQ ϭ 3.1; TEQ WHO-Avian HQ ϭ 1.3). Productivity and relative abundance measures indicated no population level effects in the UKRSS

Environmental Toxicology RISK ASSESSMENT OF GREAT HORNED OWLS (BUBO VIRGINIANUS) EXPOSED TO POLYCHLORINATED BIPHENYLS AND DDT ALONG THE KALAMAZOO RIVER, MICHIGAN, USA

Abstract-The great horned owl (GHO; Bubo virginianus) was used in a multiple lines of evidence study of polychlorinated biphenyls (PCBs) and p,pЈ-dichlorodiphenyltrichloroethane (DDT) exposures at the Kalamazoo River Superfund Site (KRSS), Kalamazoo, Michigan, USA. The study examined risks from total PCBs, including 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ World Health Organization [WHO]-Avian Toxicity Equivalency Factor [TEF] ), and total DDTs (sum of DDT, dichlorodiphenyldichloroethylene [DDE], and dichlorodiphenyldichloroethane [DDD]; ⌺DDT) by measuring concentrations in eggs and nestling blood plasma in two regions of the KRSS (upper, lower) and an upstream reference area (RA). An ecological risk assessment compared concentrations of the contaminants of concern (COCs) in eggs or plasma to toxicity reference values. Productivity and relative abundance measures for KRSS GHOs were compared with other GHO populations. Egg shell thickness was measured to assess effects of p,pЈ-DDE. The concentrations of PCBs in eggs were as great as 4.7 ϫ 10 2 and 4.0 ϫ 10 4 ng PCB/g, wet weight at the RA and combined KRSS sites, respectively. Egg TEQ WHO-Avian calculated from aryl hydrocarbon receptor-active PCB congeners and WHO TEFs ranged to 8.0 and 1.9 ϫ 10 2 pg TEQ WHO-Avian /g, (wet wt) at the RA and combined KRSS, respectively. Egg ⌺DDT concentrations were as great as 4.2 ϫ 10 2 and 5.0 ϫ 10 3 ng ⌺DDT/g (wet wt) at the RA and combined KRSS, respectively. Hazard quotients (HQs) for the upper 95% confidence interval (UCI) (geometric mean) and least observable adverse effect concentration (LOAEC) for COCs in eggs were Յ1.0 for all sites. Hazard quotient values based on the no observable adverse effect concentration (NOAEC) 95% UCI in eggs were Յ1.0, except at the LKRSS (PCB HQ ϭ 3.1; TEQ WHO-Avian HQ ϭ 1.3). Productivity and relative abundance measures indicated no population level effects in the UKRSS

Differential Accumulation of Polychlorinated Biphenyl Congeners in the Aquatic Food Web at the Kalamazoo River Superfund Site, Michigan

A series of field studies were conducted to gain a better understanding of the bioaccumulation and dynamics of polychlorinated biphenyl (PCB) congeners in the aquatic food web of the Kalamazoo River flood plain. Representative species of passerine birds, mammals, fish, aquatic plants, invertebrates, and colocated sediments were collected from areas located within submerged portions of the former Trowbridge impoundment and also from areas located at an upstream reference location. In most matrixes, total concentrations of PCBs were significantly greater in the downstream study area compared to the upstream reference location. Patterns of PCB congeners varied among trophic levels due to selective bioaccumulation of more chlorinated congeners in upper trophic level organisms. There were no statistically significant differences in total PCB concentrations among sampling grids within either site or temporally among three sampling seasons between May and September. The greatest total PCB concentrations were detected in adult tree swallows (mean = 8.7 mg/kg wet weight (ww)) and fish (mean = 4.4 mg/kg ww) collected from the former Trowbridge impoundment. Concentrations of total 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) were greatest in egg, nestling, and adult tree swallows collected from the former Trowbridge impoundment. There was not a significant correlation between concentrations of total PCBs and TEQs at either site in the mammalian or avian food webs. The relative potency of the mixture of PCBs, expressed as the ratio of TEQs to total PCBs, increased with trophic position in the avian and mammalian aquatic food webs located within the former Trowbridge impoundment

Differential Accumulation of Polychlorinated Biphenyl Congeners in the Terrestrial Food Web of the Kalamazoo River Superfund Site, Michigan

A series of field studies was conducted to determine the bioaccumulation of polychlorinated biphenyl (PCB) congeners in the terrestrial food web of the Kalamazoo River flood plain. Samples included colocated soils, native plants likely to be consumed by wildlife, several taxa of terrestrial invertebrates, small mammals, passerine bird eggs, nestlings, and adults, and great horned owl plasma and eggs. Mean concentrations of total PCBs in samples from the former Trowbridge impoundment were 6.5 mg/kg dry weight for soils and 0.023, 0.13, 1.3, 1.3, 1.6, and 8.2 mg/kg wet weight for plants, small herbivorous mammals, depurated earthworms, shrews, great horned owl eggs, and house wren eggs, respectively. Historical data from the Kalamazoo River have reported Aroclor-equivalent total PCB concentrations in the terrestrial food web; however, the degree of environmental weathering of the parent PCB mixtures was unknown. In this study, earthworms and composite samples of coleoptera exhibited PCB congener patterns that were similar to patterns in colocated soils. However, in plants, less chlorinated PCBs (e.g., mono-, di-, tri-, and tetrachlorinated biphenyls) were predominant, and in small mammals, there was a notable enrichment of PCBs 153, 180, 138, 118, and 99. In general, concentrations of PCBs were lower in most biota than in soil from the Kalamazoo River Area of Concern (KRAOC) although there was a modest biomagnification of PCBs from lower trophic level biota to higher trophic levels. As a consequence of environmental weathering of PCBs in the terrestrial food web of the KRAOC, the relative potency of the PCBs (expressed as mg TEQs/kg PCBs) decreased from soil to most biota. While there was a general trend, as expected, in which concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQs) increased with total PCBs, this relationship was rather poor (R2 = 0.13). Taken together, these data suggest that the differential accumulation of PCB congeners in the terrestrial food web can be explained by congener-specific differences in bioavailability from soil, exposure pathways, and metabolic potential of each of the food web components