An approach to evaluating bias and uncertainty in estimates of external dose obtained from personal dosimeters.
Gilbert-ES; Fix-JJ; Baumgartner-WV
Health Phys 1996 Mar; 70(3):336-345
An approach for quantifying errors in estimates of external radiation based on personal dosimeter data was developed and applied to workers at the Hanford Site, Washington State. For each error source, the systematic error was quantified by determining a bias factor (BF). The overall bias from all sources was computed as the product of the BFs from all sources (BF product). The BFs themselves were determined by evaluating relevant data and expert judgment. Uncertainty factors for quantifying random errors were also computed by a similar procedure. The approach was applied to three specific systems used at the Hanford site to monitor radiation exposures for four calendar periods. Possible errors arising from laboratory sources, energy response sources, backscattering sources, environmental sources, and from converting the data to deep doses and to red bone marrow and lung specific doses were evaluated for the energy ranges 100 to 300 and 300 to 1,000 kiloelectron volts and anterior/posterior and rotational geometries. The most important source of error was energy response. Biases from the other sources accounted for only 10% or less of the total error. For the dose conversions, the deep dose was fairly accurately estimated except for the period before 1958, the overall biases varying from 1 to 12%. Before 1958, the overall bias in the deep dose averaged 27%. Lung and bone marrow doses were overestimated by an average of 10 and 5% for periods after 1957, respectively. Before 1957, the bias in the bone marrow and lung doses was 75 and 33%. The authors conclude that, although this analysis has provided quantitative information on errors in the Hanford site dose estimates, its main contribution may be the development of a general approach for obtaining the information needed to adjust epidemiological analysis for errors in annual and cumulative dose estimates obtained from personal dosimeters.
NIOSH-Publication; NIOSH-Grant; Grants-other; Dosimetry; Statistical-analysis; Information-systems; Radiation-monitoring; Film-badges; Occupational-exposure; Radiation-exposure
Health Risk Assessment Dept Battelle Memorial Inst PO Box 999 Msin P7 82 Richland, WA 99352
Other Occupational Concerns; Grants-other
Battelle Pacific Northwest Laboratories, Richland, Washington