Screening Risk Assessment for Possible Radionuclides in the Amchitka Marine Environment

Abstract

As part of its environmental stewardship program the U.S. Department of Energy (DOE) is reevaluating three sites where underground nuclear tests were conducted in the deep subsurface of Amchitka Island, Alaska. The tests (i.e., Long Shot, Milrow, and Cannikin) were conducted in 1965, 1969, and 1971, respectively. Extensive investigations were conducted on these tests and their effect on the environment. Evaluations at the time of testing indicated limited release of radionuclides and absence of risk related to the testing; however, these are being reevaluated under the current DOE environmental stewardship program. A screening risk assessment of potential radionuclide release into the marine environment is an important part of this reevaluation. The risk assessment is one of three interrelated activities: a groundwater model and this screening risk assessment, both of which guide the decisions in the third activity, the site closure plan. Thus, the overall objective of the work is to understand, and subsequently manage, any risk to humans and the environment through a closure and long-term stewardship plan. The objective of this screening risk assessment is to predict whether possible releases of radionuclides at the ocean floor would represent potential risks to Native Alaskans by consumption of marine subsistence species.more » In addition, risks were predicted for consumers of commercial catches of marine organisms. These risks were calculated beginning with estimates of possible radionuclide release at the seafloor (from a groundwater modeling study), into the seawater, through possible uptake by marine organisms, and finally possible consumption by humans. The risk assessment model has 11 elements, progressing from potential release at the seafloor through water and food chains to human intake. Data for each of these elements were systematically found and synthesized from many sources, and represent the best available knowledge. Whenever precise data were lacking, the most conservative data were selected. Conservative assumptions and values were used for radionuclide uptake factors and for marine food ingestion rates by human receptors. The dispersion of material in the marine environment utilized a U.S. Environmental Protection Agency (EPA)-approved model (CORMIX). In addition, the screening level of 1 x 10{sup -6} or 1 excess cancer in 1 million is considered by the EPA to be below the level of concern. The end result, as presented in this report, is a highly conservative estimate of potential risks that are well below the EPA's most conservative risk threshold for both subsistence users and commercial-catch consumers.« less