An Approach for Evaluating Contaminants of Concern and Communicating Risk to the Public Using ETTP of Oak Ridge as a Case Study - 22315

The objective of this paper is to illustrate an approach for presenting complex risk information, particularly regarding contaminants of concern (COCs), in a way that makes the information readily accessible to the public. We start with DOE's Baseline Human Health Risk Assessment (published 2007) for groundwater plumes and Mitchell Branch, at the East Tennessee Technology Park (ETTP) at Oak Ridge, TN. Estimating risks is complicated and fraught with uncertainties. Assessments are often presented in voluminous reports with extensive data appendices that deserve a clear set of summary tables. We provide examples of such tables for the original data set and illustrate a role in clarifying a substantial change in the relative contribution of COCs to cancer risk. Protecting 'human health and the environment' while cleaning up former nuclear-production sites is a key goal of the U. S. Department of Energy's Office of Environmental Management (DOE-EM). Characterizing groundwater contamination remains an important environmental challenge at many DOE sites, including ETTP. Extensive field work and analyses are done to identify COCs and characterize plumes in four dimensions as they move from sources towards receptors or points of compliance. The DOE Oak Ridge Office of Environmental Management (OREM) asked the multi-university, multidisciplinary Consortium for Risk Evaluation with Stakeholder Participation (CRESP) to develop a coherent and consistent framework for assessing and treating legacy contaminated plumes at ETTP. This framework included a review of the available Baseline Human Health Risk Assessment (BHHRA) completed in ca 2005 and published in 2007, as well as incorporating new information on the COCs that might affect the remediation options. We present summary tables for the cancer and non-cancer risk assessments in the BHHRA and illustrate how these tables can accommodate and clarify new information for risk communication. A full human health risk assessment incorporates contaminant distributions and concentrations, potential pathways, and exposure scenarios influenced by various remediation options over various time frames. Over the years, human health risk assessments have become increasingly complex, with more human receptors and more exposure scenarios and focuses attention on a shorter list of contaminants of concern (COC)s in keeping with EPA guidance documents. The BHHRA relied extensively on EPA Guidance (1999), supplemented by EPA's Guidelines for Carcinogen Risk Assessment (2005). In the case of ETTP, the documents are data rich, with numerous tables of groundwater sampling results, quality controls, and estimates of the risk contributions of various COCs that are significant in making decisions for groundwater remediation. We suggest that DOE and its stakeholders are well served by summary tables identifying the risk contributions and exposure pathways. ETTP is an excellent example because it has the BHHRA that is comprehensive, carefully planned, well executed, and consistent with EPA guidance and the then current EPA Integrated Risk Information System data base (EPA IRIS). The work reported here was conducted with funding from DOE (DE-FC01-06EW07053) through the Consortium for Risk Evaluation with Stakeholder Participation (CRESP), Vanderbilt University and Rutgers University. (authors)