These risk assessments and the reviews focus on the specific impacts of PCBs in the river. Although some comments are directed toward other contaminants, that was not the charge to the review panel. The panel consists of academic experts in the area of chemical effects on health and environment. Three panel members evaluated the human health risk assessments; three panel members evaluated the ecological risk assessments. Panel members visited the site, engaged in meetings regarding the site, met with members of the Wisconsin Department of Natural Resources & the US Environmental Protection Agency, wrote critiques of the Exponent and ThermoRetec assessments, discussed items of concern, and, with this report, provide a written commentary on their views of the assessments.
The review panel found that the consultants used different datasets and different approaches in their calculations. For example, Exponent relied on concentrations from sediment and biota samples collected in 1998 and 1999 for ecological evaluation; ThermoRetec utilized a more extensive dataset collected over the previous ten years. Exponent used a Monte Carlo analysis for human health assessment resulting in a range of risk; ThermoRetec 's assessment resulted in a single point estimate.
Human health risk assessment reviews by the panel are evaluated separately and then compared with each other. The ecological assessments are evaluated separately. Comments provide a critical assessment of strengths and limitations.
Briefly, the panel found both strengths and weaknesses in each risk assessment.