Ecological Risk Assessment

Executive Summary August 1999

This document presents the baseline Ecological Risk Assessment (ERA) for the Hudson River, which is part of Phase 2 of the Reassessment Remedial Investigation/Feasibility Study (Reassessment RI/FS) for the Hudson River PCBs site in New York. The ERA quantitatively evaluates the current and future risks to the environment in the Upper Hudson River (Hudson Falls, New York to Federal Dam at Troy, New York) and the current risks to the environment in the Lower Hudson River (Federal Dam to the Battery in New York City) posed by polychlorinated biphenyls (PCBs) in the absence of remediation.(1) This report uses current U.S. Environmental Protection Agency (USEPA) policy and guidance as well as additional site data and analyses to follow up 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 indicates that PCBs in the Hudson River generally exceed levels that have been shown to cause adverse ecological effects, and that those levels will continue to be exceeded in the Upper Hudson through 2018 (the entire forecast period). The results of the ERA 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 to the Battery in New York City. As defined in the ERA, the Upper Hudson River is the 40 mile (64 km) stretch from Hudson Falls to the Federal Dam at Troy. The Lower Hudson River extends approximately 160 miles (258 km) from the Federal Dam to the Battery.

The Hudson River is home to a wide variety of ecosystems. These ecosystems differ between the Upper Hudson River and the Lower Hudson River. The Upper Hudson River is non-tidal, consists of a series of pools separated by dams, and is entirely freshwater. In contrast, 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. Both the Upper and Lower Hudson have deep water environments as well as shallow nearshore areas with aquatic vegetation.

PCBs were released from two General Electric Company 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 were selected to include direct exposure to PCBs in 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 Hudson River are:

Benthic community structure as a food source for local fish and wildlife
Protection and maintenance (survival, growth, and reproduction) of local fish (forage, omnivorous, and piscivorous)
Protection and maintenance (survival, growth, and reproduction) of local insectivorous birds
Protection and maintenance (survival, growth, and reproduction) of local waterfowl
Protection and maintenance (survival, growth, and reproduction) of local piscivorous birds
Protection and maintenance (survival, growth, and reproduction) of local wildlife
Protection of threatened and endangered species
Protection of significant habitats
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 generally include measured or 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 are:

1) benthic community indices, such as richness, abundance, diversity and biomass;

2) concentrations of PCBs in fish and invertebrates to evaluate food-chain exposure;

3) measured and modeled total PCB body burdens in receptors (including avian receptor eggs) to determine exceedance of effect-level thresholds based on toxicity reference values (TRVs);

4) measured and modeled TEQ-based PCB body burdens in receptors (including avian receptor eggs) to determine exceedance of effect-level thresholds based on TRVs;

5) exceedence of criteria for concentrations of PCBs in river water that are protective of fish and wildlife;

6) exceedence of guidelines for concentrations of PCBs in sediments that are protective of aquatic health; and

7) field observations.

Receptors of Concern

The 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 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:

Aquatic Invertebrates

Benthic macroinvertebrate community (e.g., aquatic worms, insect larvae, and isopods)
Fish Species

Pumpkinseed (Lepomis gibbosus)
Spottail shiner (Notropis hudsonius)
Brown bullhead (Ictalurus nebulosus)
White perch (Morone americana)
Yellow perch (Perca flavescens)
Largemouth bass (Micropterus salmoides)
Striped bass (Morone saxatilis) P/S
Shortnose sturgeon (Acipenser brevirostrum) O
Birds

Tree swallow (Tachycineta bicolor)
Mallard (Anas platyrhychos)
Belted kingfisher (Ceryle alcyon)
Great blue heron (Ardea herodias)
Bald eagle (Haliaeetus leucocephalus)
Mammals

Little brown bat (Myotis lucifugus)
Raccoon (Procyon lotor)
Mink (Mustela vison)
River otter (Lutra canadensis)

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 provide current and future (i.e., measured and modeled) concentrations of PCBs in fish, sediments and river water, and form the basis of the site data collection and analyses that were used in conducting the ERA. Exposure parameters were obtained from USEPA references, the scientific literature, and directly from researchers.

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, TRVs were selected 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 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 (measured or 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. Based on a comparison of modeled concentrations to measured values, the PCB concentrations in fish presented in the May 1999 Baseline Modeling Report are expected to be within an order of magnitude, but likely closer to a factor of two, of future measured values.

To integrate the various components of the ERA, 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 originating in the 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

Benthic community structure as a food source for local fish populations was assessed using three lines of evidence. All three suggest an adverse effect of PCBs on benthic invertebrate populations serving as a food source to local fish in the Upper Hudson River. Two lines of evidence 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 evaluated using seven lines of evidence. Collectively, they indicate that current (1993) and future PCB exposures are not expected to be of a sufficient magnitude to prevent reproduction or recruitment of common fish species in the Hudson River. However, current and future exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of resident fish in the Upper Hudson River, and current exposure to PCBs may have similar adverse effects on upper trophic level fish (such as largemouth bass and white perch) in the Lower Hudson River.

Current fish body burdens exceed most TRVs (i.e., TQ > 1) in the Upper Hudson River for all species, and body burdens consistently exceed TRVs for upper trophic level fish in both the Upper and Lower Hudson River. Future body burdens in fish are expected to exceed TRVs through 2018 (the entire forecast period) in the Upper Hudson River for several of the upper trophic level fish species. 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 dioxin-like PCBs, no uncertainty factors were needed). Given the magnitude of the TQs, they would have to decrease by an order of magnitude or more to fall below 1 for most fish species in the Upper Hudson River and for upper trophic level fish in the Lower Hudson River.

Measured and modeled concentrations of PCBs in river water in the Upper Hudson River and sediment show exceedences of their respective criteria and guidelines for protection of fish through 2018 (the entire forecast period). Measured concentrations of PCBs in river water and sediment in the Lower Hudson River typically exceed all but the least stringent criteria and guidelines for protection of fish at most locations.

Insectivorous Birds

Risks to insectivorous birds were evaluated using six lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of insectivorous birds. However, anomalous nesting behavior has been observed in tree swallows in the Upper Hudson River and these behaviors may adversely affect reproductive capability at the population level. There is a moderate degree of uncertainty in the calculated doses of PCBs in tree swallow diet and the concentrations of PCBs in eggs. There is a low degree of uncertainty associated with the tree swallow TRVs, which were derived from field studies of Hudson River tree swallows.

Waterfowl

Risks to waterfowl were evaluated using six lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of the waterfowl. However, current and future exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of waterfowl in the Upper Hudson River. To a lesser degree, current exposures may have similar adverse effects on waterfowl in the Lower Hudson River.

Calculated dietary doses of PCBs and concentrations of PCBs in eggs under current and future conditions typically exceed their respective TRVs. TQs for the dioxin-like PCBs consistently show greater exceedences than TQs for total PCBs. Exceedences of TRVs are expected to occur through 2018 (the entire forecast period). 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 1 for the mallard duck in the Upper Hudson River.

Piscivorous Birds

Risks to piscivorous birds were evaluated using six lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of these piscivorous species, which have been observed along the Hudson River. However, current and future exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of piscivorous birds in the Upper Hudson River, and current exposure to PCBs may have similar adverse effects on piscivorous birds in the Lower Hudson River. Calculated dietary doses of PCBs and concentrations of PCBs in eggs exceed all TRVs for the Upper Hudson River through 2018 (the entire forecast period) and current exposures exceed all TRVs in the Lower Hudson River. There is a moderate degree of uncertainty in the calculated dietary doses and concentrations in eggs. Given the magnitude of the majority of the TQs, they would have to decrease by an order of magnitude or more to fall below 1 for piscivorous birds in the Upper Hudson River.

Insectivorous Mammals

Risks to insectivorous mammals were evaluated using four lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of insectivorous mammals. However, current and future exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of mammals in the Upper Hudson River. To a lesser degree, current exposures may have similar adverse effects on insectivorous mammals in the Lower Hudson River. Modeled dietary doses for the little brown bat exceed TRVs under current and future conditions in the Upper Hudson River. Given the magnitude of the majority of the TQs, they would have to decrease by an order of magnitude or more to fall below 1. There is a moderate degree of uncertainty in the calculated dietary doses.

Omnivorous Mammals

Risks to omnivorous mammals were evaluated using four lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of omnivorous mammals. However, current and future exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of mammals in the Upper Hudson River. To a lesser degree, current exposures may have similar adverse effects on omnivorous mammals in the Lower Hudson River. Modeled dietary doses for the raccoon exceed TRVs under current and future conditions in the Upper Hudson River. Given the magnitude of the majority of the TQs, they would have to decrease by an order of magnitude or more to fall below 1. There is a moderate degree of uncertainty in the calculated dietary doses.

Piscivorous Mammals

Risks to piscivorous mammals were evaluated using four lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are not of a sufficient magnitude to prevent reproduction of piscivorous mammals. However, current exposures to the PCBs may reduce or impair the survival, growth, and reproductive capability of mammals in the Upper and Lower Hudson River.. Future exposures may have adverse effects on piscivorous mammals in the Upper Hudson River. Modeled dietary doses for the mink and river otter exceed TRVs under current and future conditions in the Upper Hudson River. Given the magnitude of the majority of the TQs, they would have to decrease by an order of magnitude or more to fall below 1. There is a moderate degree of uncertainty in the calculated dietary doses.

Threatened and Endangered Species

Risks to threatened and endangered species were evaluated using four lines of evidence. Collectively, they indicate that current and future concentrations of PCBs are of a sufficient magnitude to adversely affect the reproductive capability of these fragile populations.

TQs for the bald eagle exceed 1 through 2018 (the entire forecast period) in the Upper Hudson River and exceed 1 for all locations in the Lower Hudson River. TQs for the shortnose sturgeon exceed 1 through 2018 (the entire forecast period) for most TRVs developed on the basis of reproductive effects at all locations in the Upper Hudson River. TQs for the shortnose sturgeon exceed 1 for all locations in the Lower Hudson River. There is a moderate degree of uncertainty in the modeled fish body burdens and calculated dietary doses and egg concentrations of PCBs. Given the magnitude of the TQs for the bald eagle, they would have to decrease by two orders of magnitude or more to fall below 1 in the Upper Hudson River.

Measured and modeled concentrations of PCBs in Upper Hudson River water exceed criteria developed for the protection of wildlife through 2018 (the entire forecast period). Measured concentrations of PCBs in Lower Hudson River water exceed criteria developed for the protection of wildlife at most locations. Measured and modeled concentrations of PCBs in sediment in the Upper Hudson River exceed all but the least stringent guidelines at all locations through 2018 (the entire forecast period). Measured concentrations of PCBs in sediment in the Lower Hudson River exceed all but the least stringent guidelines at all locations.

Significant Habitats

Risks to significant habitats were evaluated using two lines of evidence. Together, they indicate that current and future concentrations of PCBs are of a sufficient magnitude to adversely affect the ability of particular habitats in the Hudson River to support sustainable, healthy wildlife populations.

Conclusions

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

Fish in the Hudson River are at risk from exposure to PCBs; fish that eat other fish (i.e., which are higher on the food chain), such as the largemouth bass and striped bass, are especially at risk. PCBs may adversely affect fish survival, growth, and reproduction.

Birds and mammals that feed on insects with an aquatic stage spent in the Hudson River, such as the tree swallow and little brown bat, are at risk from PCB exposure. PCBs may adversely affect the survival, growth, and reproduction of these species.

Waterfowl feeding on animals and plants in the Hudson River are at risk from PCB exposure. PCBs may adversely affect avian survival, growth, and reproduction.

Birds and mammals that eat PCB-contaminated fish from the Hudson River, such as the bald eagle, belted kingfisher, great blue heron, mink, and river otter, are at risk . PCBs may adversely affect the survival, growth, and reproduction of these species.
Omnivorous animals, such as the raccoon, that derive some of their food from the Hudson River are at risk from PCB exposure. PCBs may adversely affect the survival, growth, and reproduction of these species.

Fragile populations of threatened and endangered species, represented by the bald eagle and shortnose sturgeon, are particularly susceptible to adverse effects from PCB exposure.

PCB concentrations in water and sediments in the Hudson River generally exceed standards and criteria and guidelines established to be protective of the environment. Animals that use areas along the river designated as significant habitats may be adversely affected by the PCBs.

The risks to fish and wildlife are greatest in the Upper Hudson River (in particular the Thompson Island Pool) and decrease in relation to PCB concentrations down river. Based on modeled future PCB concentrations, many species are expected to be at considerable riskthrough 2018 (the entire forecast period).

1. A separate ecological risk assessment is being conducted to evaluate the future risks to the environment in the Lower Hudson River.

Ecological Risk Assessment

Executive Summary August 1999

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