Chernobyl: 20 Years Later Chernobyl: 20 Years Later Use of Bioavailability “High Level Radionuclide-contaminated” Soil from Savannah River Site: A Tool for Estimating Effective Ingested Dose at Chernobyl Chang Ho Yu Exposure Science Division, Environmental and Occupational Health Sciences Institute, NJ, USA Kristie M. Ellickson Environmental Chemistry and Technology Program, University of Wisconsin at Madison, WI, USA Paul J. Lioy 1 Exposure Science Division, Environmental and Occupational Health Sciences Institute, NJ, USA Abstract An approach for the estimation of oral bioavailability for high-level radionuclide-contaminated soils has been developed, and measurements were made of 137 Cs and 90 Sr bioaccessibility. The bio- accessibility of these radionuclides ( 137 Cs and 90 Sr) found in SRS (Savannah River Site; SC, USA) soils were measured in both simulated gastric and intestinal fluids. The bioaccessibility of cesium- 137 ranged from 8.9 ~ 22.4 % and 8.3 ~ 38.8 % after extraction by gastric and gastric-intestinal flu- ids, respectively. The bioaccessibility of strontium-90 was higher than the cesium-137, ranging from 29.7 ~ 97.1 % and 17.8 ~ 60.5 % in gastric and intestinal fluids, respectively. The effective ra- diation doses potentially received by humans were estimated using Monte Carlo simulations that used age-specific exposure factors, total 137 Cs and 90 Sr radionuclide concentrations, and site- specific bioaccessibility of each radionuclide. It was not realistic to make long-term exposure/dose estimates for SRS situations considering the current land use at the Department of Energy (DOE) site and the very high-levels of radionuclides in soils. However, the method and associated dose esti- mates were used to calculate the potential risk to people living in or around the Exclusion Zone of the Chernobyl Nuclear Power Plant (ChNPP) when similar high concentration of 137 Cs and 90 Sr in the soil. This Exclusion Zone was created after the ChNPP explosion which resulted in highly radionuclide-contaminated soils downwind of the plant. Pica children (2.5-year-old) were used as individuals potentially at the highest risk of exposure to cesium-137 and strontium-90 via non- dietary ingestion or external exposure to contaminated soils. When applied to the Chernobyl Exclu- sion Zone, the estimated dose levels exceeded the United States NCRP (National Council on Ra- diation Protection and Measurements) negligible individual dose of 0.01 mSv/yr, one hundredth of Russian Federation’s public dose limit, for children residing in the Exclusion Zone. Key words: cesium-137, strontium-90, soil, bioaccessibility, dose, estimation, SRS, Chernobyl Contents Introduction 1. Materials and Methods 2. Results and Discussion 3. Conclusion References 10 Chernobyl: 20 Years Later f 1 Address correspondence to Dr. Paul J. Lioy. EOHSI, Room 302, 170 Frelinghuysen Road, Piscataway, NJ 08854, USA. Tele- phone: +1-732-445-0155, Fax: +1-732-445-0116, E-mail: plioy@eohsi.rutgers.edu