External Dose Reconstruction Under Part B of the Energy Employees Compensation Act

Abstract

External doses reconstructed under Part B of the Energy Employees Occupational Illness Compensation Program Act include not only those that were recorded by personal dosimeters, but also those that were not recorded. Recorded doses may require corrections to account for measurement bias or limitations in the dosimeters' capabilities. Unrecorded doses that have been reconstructed include (1) those missed due to limits of detection associated with personal dosimeters, (2) external ambient doses that may have been inadvertently omitted from the monitoring results (or were not monitored altogether in the case of nonradiation workers), and (3) doses incurred as a result of medical x-ray examinations required by employers. Additionally, some workers were not monitored (or their dosimetry data are not available) even though there was a potential for exposure; doses to such workers are typically assigned based on the records of coworkers who performed the same, or similar, tasks. Additional issues that complicate the dose reconstruction process include the requirements that (1) all external doses must be partitioned according to radiation type and energy, and (2) the accompanying doses to specific body organs must be estimated. Since the external dose reconstruction process typically incorporates many claimant-favorable methodologies, parameters, and assumptions, the doses assigned do not necessarily reflect either realistic or actual estimates of the doses received, and external doses assigned to workers under the Act often are substantially higher than those contained in the dosimetry records.

The growing importance of radiation worker studies

“…Figure 1 indicates the potential for the underestimation of external penetrating radiation doses, in the early years of operations at two US nuclear installations with workers included in INWORKS. Undoubtedly, the claimant-favourable assumptions made by Merwin et al, 8 when reconstructing doses for the purposes of worker compensation, led to unrecorded doses being overestimated; possibly substantially so. Nonetheless, the differences between recorded and reconstructed doses shown in Fig.…”

“…Such a positive correlation would lead to an overestimation of the slope (risk per unit dose) of the dose-response for the photon doses presently used in INWORKS, and this must be borne in mind when assessing the INWORKS results.

Fig. 1Comparison of the distributions by calendar year of average annual individual whole-body doses received occupationally from penetrating (primarily photon) radiation from external sources, as recorded at the US nuclear installations at Hanford 13 and Savannah River, 14 and as reconstructed 8 for the purposes of compensating people who develop cancers that could be attributable to prior occupational exposure to radiation at these installations

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Characterization of Exposures to Workers Covered Under the U.S. Energy Employees Compensation Act

“…In all cases processed by NIOSH, missed dose is explicitly included in the external and internal dose reconstructions (Bracket et al 2008; Merwin et al 2008). Although missed dose for external exposure can be substantial for the early years when the detection limit for film badges was higher than that for currently employed thermoluminescent dosimeters and the badges were exchanged more frequently, the most significant missed dose is that associated with persons monitored for internal exposure to insoluble actinides.…”

Data Collection, Processing, Validation, and Verification

“…To date, approximately 1,085,000 documents have been uploaded to NOCTS ( Database (SRDB). § § Finally, the data are also entered into spreadsheets that facilitate the dose reconstructors in using relevant data as inputs into the process of estimating both external and internal doses on an individual worker basis (Merwin et al 2008b;Brackett et al 2008;Maher et al 2008). After the dose reconstruction is completed and approved by NIOSH, a complete copy of the worker's record is submitted electronically to the U.S. Department of Labor (DOL), the agency responsible for rendering a decision as to whether a case is compensable.…”

“…Later, such measurements were made primarily through the use of thermoluminescent dosimeters (TLDs). Although this reduced many uncertainties, they were not eliminated (Merwin et al 2008b). Another source of external exposures was the use of x rays in diagnostic medical examinations required in the course of employment by DOE and AWE facilities.…”