Risk Assessment

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.

What is meant by risk?

EPA’s definition of “risk” is the chance of harmful effects to human health or to ecological systems resulting from exposure to an environmental stressor. A risk assessment is a formal procedure used to characterize the nature and magnitude of health risks to humans (e.g., residents, workers, recreational visitors) and ecological receptors (e.g., birds, fish, wildlife) from chemicals and other stressors that may be present in the environment. Risk managers at EPA use this information to help them decide how to protect humans and the environment from these stressors. The National Academy of Sciences (NAS) developed the framework for a standard risk assessment protocol for estimating the likelihood of adverse health effects from any type of exposure (NAS, 1983). This protocol was adopted and updated by the EPA, state regulatory agencies, and the risk assessment scientific community to serve as the framework for conducting risk assessments. The Grasse River 1993 risk assessment, the 2002 and 2010 human health updates, and 2010 ecological screening document were prepared using standard EPA risk assessment approaches.

To characterize the risk of harmful effects to the community, EPA uses information from studies on occupational exposures to humans and studies on laboratory animals to develop estimates of acceptable levels of exposure to chemicals found in the environment. Then, based on conditions at a particular location, calculations are made to determine if potential exposures exceed these levels.

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). It is important to understand that risk assessments are protective, not predictive. They are intended to ensure the public is protected, and cannot be used to predict the occurrence of any injury or disease.

Exceeding a minimal risk level cannot be taken as an indication that health effects will actually occur. EPA has explained this in regard to the cancer risk factors they publish on the Integrated Risk Information System (IRIS): "In general IRIS values cannot be validly used to accurately predict the incidence of human disease or the type of effects that chemical exposures have on humans." (EPA, 1998).

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.

Read more about the human health and ecological risk assessments.