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Ecological Risk Assessment Addendum

Future Risks in the Lower Hudson River Executive Summary December 1999

This document presents the baseline Ecological Risk Assessment for Future Risks in the Lower Hudson River (ERA Addendum), which is a companion volume to the baseline Ecological Risk Assessment (ERA) that was released by the U.S. Environmental Protection Agency (USEPA) in August 1999. Together, the two risk assessments comprise the ecological risk assessment for Phase 2 of the Reassessment Remedial Investigation/ Feasibility Study (Reassessment RI/FS) for the Hudson River PCBs site in New York. The ERA Addendum quantitatively evaluates the future risks to the environment in the Lower Hudson River (Federal Dam at Troy, New York to the Battery in New York City) posed by polychlorinated biphenyls (PCBs) from the Upper Hudson River (Hudson Falls, New York to the Federal Dam at Troy, New York), in the absence of remediation. This report uses current USEPA policy and guidance as well as additional site data and analyses to update USEPA's 1991 risk assessment. USEPA uses ecological risk assessments to evaluate the likelihood that adverse ecological effects are occurring or may occur as a result of exposure to one or more chemical or physical stressors. The Superfund ecological risk assessment process includes the following: 1) identification of contaminants of concern; 2) development of a conceptual model, which identifies complete exposure pathways for the ecosystem; 3) identification of assessment endpoints, which are ecological values to be protected; 4) development of measurement endpoints, which are the actual measurements used to assess risk to the assessment endpoints; 5) selection of receptors of concern; 6) the exposure assessment, which describes concentrations or dietary doses of contaminants of concern to which the selected receptors are or may be exposed; 7) the effects assessment, which describes toxicological effects due to chemical exposure and the methods used to characterize those effects to the receptors of concern; and 8) risk characterization, which compares the results of the exposure assessment with the effects assessment to evaluate the likelihood of adverse ecological effects associated with exposure to chemicals at a site.The ERA Addendum indicates that, for some species, future concentrations of PCBs in the Lower Hudson River generally exceed levels that have been shown to cause adverse ecological effects through 2018 (the entire forecast period). The results of the ERA Addendum will help establish acceptable exposure levels for use in developing remedial alternatives for PCB-contaminated sediments in the Upper Hudson River, which is Phase 3 (Feasibility Study) of the Reassessment RI/FS.

Contaminants of Concern

The contaminants of concern identified for the site are PCBs. PCBs are a group of synthetic organic compounds consisting of 209 individual chlorinated biphenyls called congeners. Some PCB congeners are considered to be structurally similar to dioxin and are called dioxin-like PCBs. Toxic equivalency (TEQ) factors, based on the toxicity of dioxin, have been developed for the dioxin-like PCB congeners. PCBs have been shown to cause adverse reproductive and developmental effects in animals. Ecological exposure to PCBs is primarily an issue of bioaccumulation rather than direct toxicity. PCBs bioaccumulate in the environment by both bioconcentrating (being absorbed from water and accumulated in tissue to levels greater than those found in surrounding water) and biomagnifying (increasing in tissue concentrations as they go up the food chain through two or more trophic levels).

Site Conceptual Model

The Hudson River PCBs site is the 200 miles (322 km) of river from Hudson Falls, New York to the Battery in New York City. As defined in the ERA and ERA Addendum, the Lower Hudson River extends approximately 160 miles (258 km) from the Federal Dam at Troy (River Mile 153) to the Battery. The Hudson River is home to a wide variety of ecosystems. The Lower Hudson River is tidal, does not have dams, and is freshwater in the vicinity of the Federal Dam, becoming brackish and increasingly more saline towards the Battery. Spring runoffs and major storms can push the salt front well below the Tappan Zee Bridge, and sometimes south to New York City. The Lower Hudson has deep water environments, shallow nearshore areas (shallows, mudflats, and shore communities), tidal marshes, and tidal swamps. PCBs were released from two General Electric Company capacitor manufacturing facilities located in the Upper Hudson River at Hudson Falls and Fort Edward, New York. Many of these PCBs adhered to river sediments. As PCBs in the river sediments are released slowly into the river water, these contaminated sediments serve as a continuing source of PCBs. During high flow events, the sediments may be deposited on the floodplain and PCBs may thereby enter the terrestrial food chain. High flow events may also increase the bioavailability of PCBs to organisms in the river water. Animals and plants living in or near the river, such as invertebrates, fish, amphibians, and water-dependent reptiles, birds, and mammals, may be directly exposed to the PCBs from contaminated sediments, river water, and air, and/or indirectly exposed through ingestion of food (e.g., prey) containing PCBs.

Assessment Endpoints

Assessment endpoints are explicit expressions of actual environmental values (i.e., ecological resources) that are to be protected. They focus a risk assessment on particular components of the ecosystem that could be adversely affected due to contaminants at the site. These endpoints are expressed in terms of individual organisms, populations, communities, ecosystems, or habitats with some common characteristics (e.g., feeding preferences, reproductive requirements). The assessment endpoints for the ERA Addendum were selected to include direct exposure to PCBs in Lower Hudson River sediments and river water through ingestion and indirect exposure to PCBs via the food chain. Because PCBs are known to bioaccumulate, an emphasis was placed on indirect exposure at various levels of the food chain to address PCB-related risks at higher trophic levels. The assessment endpoints that were selected for the Lower Hudson River are:

Measurement Endpoints

Measurement endpoints provide the actual measurements used to evaluate ecological risk and are selected to represent mechanisms of toxicity and exposure pathways. Measurement endpoints for future risk generally include modeled concentrations of chemicals in water, sediment, fish, birds, and/or mammals, laboratory toxicity studies, and field observations. The measurement endpoints identified for the ERA Addendum are:1) Modeled concentrations of PCBs in fish and invertebrates to evaluate food-chain exposure;2) Modeled total PCB body burdens in receptors (including avian receptor eggs) to determine exceedance of effect-level thresholds based on toxicity reference values (TRVs);3) Modeled TEQ-based PCB body burdens in receptors (including avian receptor eggs) to determine exceedance of effect-level thresholds based on TRVs;4) Modeled concentration of PCBs in river water to determine exceedence of criteria for concentrations of PCBs in river water that are protective of benthic invertebrates, fish and wildlife;5) Modeled concentrations of PCBs in sediment to determine exceedence of guidelines for concentrations of PCBs in sediments that are protective of aquatic health; and 6) Field observations.

Receptors of Concern

Risks to the environment were evaluated for individual receptors of concern that were selected to be representative of various feeding preferences, predatory levels, and habitats (aquatic, wetland, shoreline). The ERA Addendum does not characterize injury to, impact on, or threat to every species of plant or animal that lives in or adjacent to the Hudson River; such a characterization is beyond the scope of the Superfund ecological risk assessment. The following receptors of concern were selected for the ERA Addendum:

Aquatic Invertebrates

Fish Species Birds Mammals

Exposure Assessment

The Exposure Assessment describes complete exposure pathways and exposure parameters (e.g., body weight, prey ingestion rate, home range) used to calculate the concentrations or dietary doses to which the receptors of concern may be exposed due to chemical exposure. USEPA previously released reports on the nature and extent of contamination in the Hudson River as part of the Reassessment RI/FS (e.g., February 1997 Data Evaluation and Interpretation Report, July 1998 Low Resolution Sediment Coring Report, August 1998 Database for the Hudson River PCBs Reassessment RI/FS [Release 4.1], and May 1999 Baseline Modeling Report). The Reassessment RI/FS documents form the basis of the site data collection and analyses that were used in conducting the ERA Addendum. Future (i.e., modeled) concentrations of PCBs in fish, sediments and river water are provided in the ERA Addendum, based on fate and bioaccumulation models by Farley et al. (1999) and USEPA's Revised Baseline Modeling Report (USEPA, 2000). Exposure parameters were obtained from USEPA references, the scientific literature, and directly from researchers as reported in the ERA.

Effects Assessment

The Effects Assessment describes the methods used to characterize particular toxicological effects of PCBs on aquatic and terrestrial organisms due to chemical exposure. These measures of toxicological effects, called TRVs, provide a basis for estimating whether the chemical exposure at a site is likely to result in adverse ecological effects.In conducting the ERA Addendum, USEPA used the TRVs selected in the ERA based on Lowest Observed Adverse Effects Levels (LOAELs) and/or No Observed Adverse Effects Levels (NOAELs) from laboratory and/or field-based studies reported in the scientific literature. These TRVs examine the effects of PCBs and dioxin-like PCB congeners on the survival, growth, and reproduction of fish and wildlife species in the Lower Hudson River. Reproductive effects (e.g., egg maturation, egg hatchability, and survival of juveniles) were generally the most sensitive endpoints for animals exposed to PCBs.

Risk Characterization

Risk Characterization examines the likelihood of adverse ecological effects occurring as a result of exposure to chemicals and discusses the qualitative and quantitative assessment of risks to ecological receptors with regard to toxic effects. Risks are estimated by comparing the results of the Exposure Assessment (e.g., modeled concentrations of chemicals in receptors of concern) to the TRVs developed in the Effects Assessment. The ratio of these two numbers is called a Toxicity Quotient, or TQ.TQs equal to or greater than one (TQ > 1) are typically considered to indicate potential risk to ecological receptors, for example reduced or impaired reproduction or recruitment of new individuals. The TQs provide insight into the potential for adverse effects upon individual animals in the local population resulting from chemical exposure. If a TQ suggests that effects are not expected to occur for the average individual, then they are probably insignificant at the population level. However, if a TQ indicates risks are present for the average individual, then risks may be present for the local population.At each step of the risk assessment process there are sources of uncertainty. Measures were taken in the ERA to address and characterize the uncertainty. For example, in some cases uncertainty factors were applied in developing TRVs. The purpose of these uncertainty factors is to ensure that the calculated TRVs are protective of the receptor species of concern. Another source of uncertainty is associated with the future PCB concentrations in fish. The PCB concentrations in fish presented in the ERA Addendum (forecast from models in Farley et al. (1999) and the Revised Baseline Modeling Report (USEPA, 2000) may be significantly underestimated, which may underestimate risks to fish species. However, based on a comparison of measured concentrations of PCBs in fish to modeled concentrations, the forecasts presented in the ERA Addendum are not expected to overestimate future PCB concentration in fish, so that the risks to fish are not expected to be overestimated.To integrate the various components of the ERA Addendum, the results of the risk characterization and associated uncertainties were evaluated using a weight-of-evidence approach to assess the risk of adverse effects in the receptors of concern as a result of exposure to PCBs in the Lower Hudson River. The weight-of-evidence approach considers both the results of the TQ analysis and field observations for each assessment endpoint. For the mammals and most birds, TQs for the dioxin-like PCBs were greater than the TQs for total PCBs.

Benthic Community Structure

Risks to local benthic invertebrate communities were examined using two lines of evidence. These lines of evidence are: 1) comparison of modeled water column concentrations of PCBs to criteria and 2) comparisons of modeled sediment concentrations to guidelines. Both suggest an adverse effect of PCBs on benthic invertebrate populations serving as a food source to local fish in the Lower Hudson River. Uncertainty in this analysis is considered low.

Local Fish (Forage, Omnivorous, Piscivorous and Semi-piscivorous

)Risks to local fish populations were examined using five lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB fish body burdens to TRVs; 2) comparison of modeled TEQ fish body burdens to TRVs; 3) comparison of modeled water column concentrations of PCBs to criteria; 4) comparison of modeled sediment concentrations to guidelines; and 5) field-based observations. Multiple receptors were evaluated for forage and semi-piscivorous/piscivorous fish.Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common fish species in the Lower Hudson River. However, based upon toxicity quotients, future exposure to PCBs may reduce or impair the survival, growth, and reproductive capability of some forage species (e.g., pumpkinseed) and semi-piscivorous/piscivorus fish (e.g., white perch, yellow perch, largemouth bass, and striped bass), particularly in the upper reaches of the Lower Hudson River.There is a moderate degree of uncertainty in the modeled body burdens used to evaluate exposure, and at most an order of magnitude uncertainty in the TRVs (for the TEQ-based TRVs, no uncertainty factors were needed). Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for protection of fish and wildlife through the duration of the forecast period (1993 - 2018).

Insectivorous Birds

Risks to local insectivorous bird populations were examined using six lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled total PCB egg concentrations to TRVs; 4) comparison of modeled TEQ egg concentrations to TRVs; 5) comparison of modeled water column concentrations of PCBs to criteria; and 6) field-based observations. The tree swallow was selected to represent insectivorous bird species. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common insectivorous bird species in the Lower Hudson River Valley. TQs are all below one for all locations for the entire forecast period (1993 to 2018). However, given that U.S. Fish and Wildlife Service field studies suggest PCBs may cause abnormal nest construction of Upper Hudson River tree swallows, it is possible that future exposure to PCBs in the Lower Hudson River may reduce or impair the reproductive capability of tree swallows, particularly in the upper reaches of the Lower Hudson River.There is a moderate degree of uncertainty in the calculated modeled concentrations of PCBs in tree swallow diets and the concentrations of PCBs in eggs. There is a low degree of uncertainty associated with tree swallow TRVs, which were derived from field studies of Hudson River tree swallows. Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993-2018).

Waterfowl

Risks to local waterfowl populations were examined using six lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled total PCB egg concentrations to TRVs; 4) comparison of modeled TEQ egg concentrations to TRVs; 5) comparison of modeled water column concentrations of PCBs to criteria; and 6) field-based observations. The mallard was selected to represent waterfowl. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common waterfowl in the Lower Hudson River Valley. However, based upon toxicity quotients, future exposure to PCBs may reduce or impair the survival, growth, and reproductive capability of some waterfowl, particularly in the upper reaches of the lower river.Calculated dietary doses of PCBs and concentrations of PCBs in eggs typically exceed their respective TRVs throughout the modeling period. Toxicity quotients for the TEQ-based (i.e., dioxin-like) PCBs consistently show greater exceedances than for total (Tri+) PCBs. There is a moderate degree of uncertainty in the dietary dose and egg concentration estimates. Given the magnitude of the TEQ-based TQs, they would have to decrease by an order of magnitude or more to fall below one for waterfowl in the Lower Hudson River.Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993-2018).

Piscivorous Birds

Risks to local semi-piscivorous/piscivorous bird populations were examined using six lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled total PCB egg concentrations to TRVs; 4) comparison of modeled TEQ egg concentrations to TRVs; 5) comparison of modeled water column concentrations of PCBs to criteria; and 6) field-based observations. The belted kingfisher, great blue heron, and bald eagle were selected to represent piscivorous birds. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of these piscivorous species. However, based upon toxicity quotients, future exposure to PCBs may reduce or impair the survival, growth, and reproductive capability of some piscivorous birds, particularly in the upper reaches of the Lower Hudson Rver. Calculated dietary doses of PCBs and concentrations of PCBs in eggs exceed all TRVs (i.e., NOAELs and LOAELs) for the belted kingfisher and bald eagle throughout the modeling period, and exceed NOAELs for the great blue heron. Toxicity quotients for egg concentrations are generally higher than body burden TQs. There is a moderate degree of uncertainty in the dietary dose and egg concentration estimates. Given the magnitude of the TQs, they would have to decrease by an order of magnitude or more to fall below one for piscivorous birds in the Lower Hudson River. In particular, the bald eagle TQs exceeded one by up to three orders of magnitude. Therefore, even if the factor of 2.5 to adjust from largemouth bass fillets to whole body burden and the subchronic-to-chronic uncertainty factor of 10 used for the body burden TRV are removed, the TQs would remain well over one. These results coupled with the lack of breeding success in Lower Hudson River bald eagles (USGS, 1999) indicate that reproductive effects may be present.Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993-2018).

Insectivorous Mammals

Risks to local insectivorous mammal populations were examined using four lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled water column concentrations of PCBs to criteria; and 4) field-based observations. The little brown bat was selected to represent insectivorous mammals. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common insectivorous mammals in the Lower Hudson River Valley. However, exposure to PCBs may reduce or impair the survival, growth, or reproductive capability of insectivorous mammals in the Lower Hudson River. Modeled dietary doses for the little brown bat exceed TRVs by up to two orders of magnitude at all locations modeled. There is a moderate degree of uncertainty in the calculated dietary doses.Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993-2018).

Omnivorous Mammals

Risks to local omnivorous mammal populations were examined using four lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled water column concentrations of PCBs to criteria; and 4) field-based observations. The raccoon was selected to represent omnivorous mammals. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common omnivorous mammals in the Lower Hudson River Valley. However, exposure to PCBs may reduce or impair the survival, growth, or reproductive capability of omnivorous mammals in the Lower Hudson River. Modeled dietary doses for the raccoon exceed dietary dose NOAELs on a total PCB (Tri+) basis and all TRVs on a TEQ-basis. There is a moderate degree of uncertainty in the calculated dietary doses.Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993 - 2018).

Piscivorous Mammals

Risks to local semi-piscivorous/piscivorous mammal populations were examined using four lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses to TRVs; 2) comparison of modeled TEQ dietary doses to TRVs; 3) comparison of modeled water column concentrations of PCBs to criteria; and 4) field-based observations. The mink and river otter were selected to represent piscivorous mammals. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of these piscivorous species. However, based upon toxicity quotients, future exposure to PCBs may reduce or impair the survival, growth, and reproductive capability of piscivorous mammals, particularly in the upper reaches of the Lower Hudson River. Calculated dietary doses of PCBs exceed the NOAEL on a total PCB basis for both the mink and river otter and exceed all TEQ-based TRVs by up to three orders of magnitude. There is a moderate degree of uncertainty in the dietary dose estimates. However, given the magnitude of the TQs, they would have to decrease at least an order of magnitude to fall below one. In particular, the river otter TQs exceeded one by up to three orders of magnitude. Therefore, even if the factor of 2.5 to adjust from largemouth bass fillets to whole body burden is removed, the TQs would remain well over one. Modeled concentrations of PCBs in river water in the Lower Hudson River show exceedances of criteria developed for the protection of wildlife through the duration of the forecast period (1993-2018). In addition, preliminary results from a NYSDEC study indicate that PCBs may have an adverse effect on the litter size and possibly kit survival of river otter in the Hudson River (Mayack, 1999b).

Threatened and Endangered SpeciesRisks to threatened and endangered species were examined using five lines of evidence. These lines of evidence are: 1) comparison of modeled total PCB dietary doses/egg concentrations to TRVs; 2) comparison of modeled TEQ dietary doses/egg concentrations to TRVs; 3) comparison of predicted modeled water column concentrations of PCBs to criteria; 4) comparison of modeled sediment concentrations of PCBs to guidelines; and 5) field-based observations. The shortnose sturgeon and bald eagle were selected to represent threatened and endangered species. Collectively, the evidence indicates that future PCB exposures (predicted from 1993 to 2018) are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of threatened or endangered species. However, using the TEQ-based toxicity quotients, potential for adverse reproductive effects in shortnose sturgeon exists, particularly when considering the long life expectancy of the sturgeon. Almost all TQs calculated for the bald eagle (across all locations) exceeded one, in some instances by more than three orders of magnitude. Both the dietary dose and egg-based results were consistent in this regard. Other threatened or endangered raptors, such as the peregrine falcon, osprey, northern harrier, and red-shouldered hawk may experience similar exposures. There is a moderate degree of uncertainty in the dietary dose estimates. However, the bald eagle TQs exceeded one by up to three orders of magnitude. Therefore, even if the factor of 2.5 to adjust from largemouth bass fillets to whole body burden and the subchronic-to-chronic uncertainty factor of 10 used for the body burden TRV are removed, the TQs would remain well over one. These results coupled with the lack of breeding success in Lower Hudson River bald eagles (USGS, 1999) indicate that reproductive effects may be present.Modeled concentrations of PCBs in river water and sediment in the Lower Hudson River show exceedances of the majority of their respective criteria and guidelines through the duration of the forecast period (1993-2018).

Significant Habitats

Risks to significant habitats were examined using four lines of evidence. These lines of evidence are: 1) toxicity quotients calculated for receptors in this assessment; 2) comparison of modeled water column concentrations of PCBs to criteria; 3) comparison of modeled sediment concentrations of PCBs to guidelines; and 4) field-based observations. Based on the toxicity quotients for receptors of concern, future PCB concentrations modeled for the Lower Hudson River exceed toxicity reference values for some fish, avian, and mammalian receptors. These comparisons indicate that animals feeding on Hudson River-based prey may be affected by the concentrations of PCBs found in the river on both a total PCB and TEQ basis. In addition, based on the ratios obtained in this evaluation, other taxononic groups not directly addressed in this evaluation (e.g., amphibians and reptiles) may also be affected by PCBs in the Lower Hudson River. Many year-round and migrant species use the significant habitats along the Lower Hudson River for breeding or rearing their young. Therefore, exposure to PCBs may occur at a sensitive time in the life cycle (i.e., reproductive and development) and have a greater effect on populations than at other times of the year. Modeled concentrations of PCBs in river water and sediment in the Lower Hudson River show exceedances of the majority of their respective criteria and guidelines through the duration of the forecast period (1993-2018).

Major Findings of the ERA Addendum

The results of the risk assessment indicate that receptors in close contact with the Lower Hudson River are at an increased ecological risk as a result of future exposure to PCBs in sediments, water, and/or prey. This conclusion is based on a TQ approach, in which modeled body burdens, dietary doses, and egg concentrations of PCBs were compared to TRVs, and on field observations. On the basis of these comparisons, all receptors of concern except the tree swallow are at risk. In summary, the major findings of the report are:

For information about this page, contact: kluesner.dave@epa.gov

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