MPS dose reconstruction for internal emitters: some site-specific issues and approaches

Area of Science:

• Radiation Health Physics
• Occupational Health and Safety
• Radiological Dose Assessment

Background:

• Dose reconstructions for internal emitters were conducted for the Million Person Study (MPS) at U.S. facilities handling radionuclides.
• Key challenges and error sources in retrospective dose estimates for internally exposed workers differ across sites.

Purpose of the Study:

• To discuss significant issues encountered in dose reconstructions for selected MPS sites.
• To present approaches used to address these issues in retrospective dose assessments.

Main Methods:

• Analysis of illustrative exposure data and dose reconstructions for workers at selected MPS facilities.
• Inclusion of related findings from some non-MPS sites for comparative insights.

Main Results:

• Major error sources in reconstructed tissue doses include identifying all internal emitters, intake timing and mode, bioassay reliability, use of coworker data, radionuclide forms, and air monitoring data relevance.
• Specific challenges were identified for radionuclide identification, intake patterns, bioassay reliability, and the use of surrogate data.

Conclusions:

• Prioritize developing best exposure scenarios for dose reconstruction.
• Use coworker data cautiously, only with strong evidence of similar exposure.
• Recognize questionable reliability of some bioassay data and uncertainty in air monitoring-based dose estimates.
• Improve lung dose estimates with site-specific respiratory parameters, but site-specific systemic models are often not justifiable.