Risk Assessment

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.