Thesis
Variability and uncertainty in radiation doses to members of the U.S. population from naturally-occurring radionuclides in the body
Washington State University
Master of Science (MS), Washington State University
2009
Handle:
https://hdl.handle.net/2376/100101
Abstract
The U.S. public's annual effective dose from internally deposited, naturally occurring and anthropogenic radionuclides is calculated using dose factors for seven phantoms (adult male, adult female, newborn, 1-, 5-, 10-, and 15-year-old) from the Radiation Dose Assessment Resource. This study uses 11,741 lines of tissue concentration data from non-occupationally exposed individuals along with information on age, sex, geographic region, body mass index and smoking history, if available. These data-from the literature and from Pacific Northwest National Laboratory's In Vivo Radioassay and Research Facility-contain measurements of 15 radionuclides, including 3H, 14C, 40K, 87Rb, 137Cs, and some members of the natural 238U, 235U, and 232Th decay series. Assumptions about equilibrium with long-lived parents are made for the 28 other radionuclides in these series lacking data. After matching literature data to phantoms based on gender and age, radionuclide concentrations are imputed into all other phantoms' source regions, and the imputed values' uncertainties are increased. Within phantoms, concentration values are grouped into source tissue regions by radionuclide, and imputed into source regions lacking tissue data. Concentrations in the hollow-organ contents source regions are calculated and activities are apportioned to the bone source regions using assumptions about each radionuclide's boneseeking behavior. Equivalent doses to target tissues from these source regions are estimated, and the target tissues are then mapped to lists of tissues with ICRP tissue weighting factors, or to surrogate tissue regions when there is no direct match. Effective doses, using ICRP tissue weighting factors recommended in 1977, 1991, and 2007 are calculated from tissue and organ equivalent doses. An upper bound of variability of the effective dose is estimated by calculating the average coefficients of variation (CV), assuming all variance is due to variability. The estimate of an adult male's average annual effective dose of 418 µSv (CV = 0.68, geometric mean = 346 µSv, sG = 1.85) using 2007 ICRP tissue weighting factors is higher than both the NCRP's estimates of 390 µSv in 1987 and 285 µSv in 2009, and is 31% higher than UNSCEAR's 310 µSv estimate in 2000. The causes of these differences are discussed
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Details
- Title
- Variability and uncertainty in radiation doses to members of the U.S. population from naturally-occurring radionuclides in the body
- Creators
- David Justin Watson
- Contributors
- Daniel J. Strom (Degree Supervisor)R. G. Schreckhise (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525099501842
- Language
- English
- Resource Type
- Thesis