Human Health Risk | Ecological Risk | Assessing Health Risks

Overview

In 1993 EPA prepared a baseline risk assessment for the Grasse River. The 1993 document identified PCBs as the primary chemical of concern for the Grasse River, and eating fish containing PCBs as posing the greatest potential risk. In 2002, Alcoa updated the human health portion of EPA's baseline risk assessment to incorporate the significant amount of Grasse River data that had been collected since 1993 along with the most current scientific and regulatory policy on risk evaluation. The 2002 update was conducted with input from EPA personnel and in accordance with EPA-approved methods, and was reviewed and approved by EPA. Updates were also prepared in 2010 and 2011 to complete the risk assessment work.

To learn more about the risk assessment process, read Assessing Health Risks.

Human Health

The human health risk assessment consists of four steps:

1. Using data to identify chemicals of interest (in this case PCBs);
2. Exposure assessment to determine potential exposure pathways and quantify the potential exposure;
3. Toxicity assessment to determine the effects from potential exposure; and
4. Risk characterization to quantify cancer risks and non-cancer health hazards associated with specific exposures at the site.

The risk assessment methodology developed by EPA and used in the update incorporates conservative assumptions in each step of the process; these conservative assumptions can result in a hypothetical risk which is an overestimate of the actual risk at a particular site. The risks calculated by regulatory agencies are based on assumptions, policies, and margins of safety that are deemed protective of public health and such risk results should be viewed as "upper-bound" limits on risks of developing disease from the exposure in question (see box).

Fish, sediment, and water column data collected from the river were considered in the evaluation of risk. Different population groups were also considered in the evaluation based on the amount of time they could potentially be exposed to PCBs in the fish, sediment, and water column. These groups included Mohawk anglers, local anglers, and recreational users of the river. In addition, a range of age groups was considered (adults, youths, and children) along with different means of exposure, including ingestion (e.g., eating or consuming) and dermal contact (e.g., contacting with skin).

For all of the scenarios evaluated, the results of the 2002 update indicate that consumption of fish is the only exposure pathway associated with elevated potential human health risks at the site. There is currently a New York State Department of Health (NYSDOH) fish consumption advisory in place recommending that people eat no fish from the lower Grasse River. The details associated with this evaluation are presented in the July 2002 Human Health Risk Assessment Update.

Data collection efforts continued from 2002 through 2011 for resident fish, water column, and sediment. Overall, this monitoring indicates that PCB levels continued to decline river-wide since the 2002 update was completed – see water column and resident fish PCB concentrations trend results.

In 2011, EPA requested that Alcoa recalculate risks and hazards associated with non-PCB chemicals of concern in the Study Area that were identified in USEPA’s (1993) BLRA to incorporate the most current regulatory policy on risk evaluation. Risks and hazards for non-PCB chemicals of concern for surface water and sediments are within USEPA’s target risk range. The 2011 assessment for non-PCBs risks and hazards for local anglers support the conclusion from the two previous risk assessments (1993 and 2002) that PCBs are the primary driver of risks in the Grasse River.

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Ecological

Ecological risks (e.g., potential risks to birds, mammals, fish, etc. that inhabit the Grasse River) were also evaluated in EPA's 1993 baseline risk assessment. The 1993 document identified potential ecological risks to the sediment dwelling organisms of the lower Grasse River, birds foraging in the Grasse River, bats foraging above the lower Grasse River, and mink. PCBs are the primary chemical of concern with respect to ecological risks. The potential risk to higher level organisms such as birds and mink is associated with the consumption of prey that accumulate PCBs in their tissue (e.g., fish). As is the case with human health risks, the principal concern with respect to ecological risks involves consumption of fish containing PCBs. EPA revisited the ecological baseline risk assessment in 2010 to incorporate the additional Grasse River data along with the most current scientific and regulatory policy on risk evaluation.

The 2010 update was developed using EPA's prescribed methodology for ecological risk assessments that calculated risk to aquatic organisms from exposure to chemical compounds in sediment and surface water. EPA performed this evaluation by determining the following:

• Risk to aquatic organisms was estimated by comparing maximum and mean sediment and surface water exposure concentrations with benchmark values to calculate hazard quotients.
• Risk to fish was evaluated by comparing measured concentrations of chemicals in fish tissue with concentrations cited in published studies that identified adverse effects in fish and concentrations at which adverse effects were observed.
• Food chain models were used to calculate risk to upper trophic level fish-eating birds and mammals and insect-eating mammals from consumption of fish and aquatic invertebrates.
• Risk was estimated by comparing maximum and mean calculated dietary PCB intake with toxicity reference values for birds and mammals.

The 2010 update concludes there is potential risk to fish-eating birds and mammals and insect-eating mammals. The potential risk to higher level organisms such as birds and mink is associated with the consumption of prey that accumulate PCBs in their tissue (e.g., fish). As is the case with human health risks, the principal concern with respect to ecological risks involves consumption of fish containing PCBs.

Arconic (formerly Alcoa) provided comments to EPA expressing concern that a number of the assumptions adopted in the analysis are overly conservative and that the most recent data available should be used as the basis for the assessment. Based on these considerations, the company believes that the analysis provides an overstatement of the current potential ecological risk associated with the Grasse River site.

Summary

Because fish are the main driver of potential human health and ecological risks in the lower Grasse River, reducing PCBs in fish is a primary goal of remediation within the lower Grasse River. The source of PCBs to the fish is the PCBs contained in the surface sediments of the lower Grasse River. As such, reducing PCBs in lower Grasse River fish is directly related to reducing the PCBs levels in the surface sediments of the river, which is where they can enter the food chain and ultimately be taken up by the fish.

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Assessing Health Risks

In 1993, EPA prepared a baseline risk assessment for the Grasse River. In 2002, at the request of EPA, Arconic (formerly Alcoa) updated the human heath portion of the EPA's baseline risk assessment to incorporate the significant amount of Grasse River data that had been collected since 1993 along with the most current scientific and regulatory policy on risk evaluation. The 2002 update was conducted with input from EPA personnel and in accordance with EPA-approved methods, and was reviewed and approved by EPA.

The results of the 2002 human health risk assessment update indicate that consumption of fish is the only exposure pathway associated with elevated potential human health risks at the site. There is currently a New York State Department of Health (NYSDOH) fish consumption advisory in place recommending that people eat no fish from the lower Grasse River. The details associated with this evaluation are presented in the July 2002 Human Health Risk Assessment Update.

In 2011, EPA requested that the company recalculate risks and hazards associated with non-PCB chemicals of concern in the Study Area that were identified in USEPA’s (1993) BLRA to incorporate the most current regulatory policy on risk evaluation. Risks and hazards for non-PCB chemicals of concern for surface water and sediments are within USEPA’s target risk range. The 2011 assessment for non-PCBs risks and hazards for local anglers support the conclusion from the two previous risk assessments (1993 and 2002) that PCBs are the primary driver of risks in the Grasse River.

In 2010, EPA prepared an ecological risk analysis update to revisit the ecological portion of the 1993 baseline risk assessment to reflect current information. The 2010 document concluded there is potential risk to fish-eating birds and mammals and insect-eating mammals. The potential risk to higher level organisms such as birds and mink is associated with the consumption of prey that accumulate PCBs in their tissue (e.g., fish). It is believed that the use of conservative exposure assumptions in both the human health and ecological risk assessments may overestimate the actual risk to the potential receptors. Also, the continued decline in PCB concentrations observed in lower Grasse River fish, sediments, and surface water since the updates were completed indicates that current potential risks to human and wildlife receptors are lower than those estimated within these risk assessment documents.

In order to ensure that even sensitive individuals are protected, EPA adopts a conservative approach to these assessments to ensure that the risks are never underestimated (NRC, 2009). Based on this consideration, the use of conservative exposure assumptions in both the human health and ecological risk assessments can overestimate the actual risk to the potential receptors. Additionally, the continued decline in PCB concentrations observed in lower Grasse River fish, sediments, and surface water since the risk assessment updates were completed indicates that current potential risks to human and wildlife receptors are lower than those estimated in the risk assessment documents.

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