BIO Web Conf.
Volume 14, 2019The 12th International Conference on the Health Effects of Incorporated Radionuclides (HEIR 2018)
|Number of page(s)||2|
|Section||Dosimetry and Dose Assessment: Oral presentations|
|Published online||07 May 2019|
Comprehensive dosimetry for seven exposure sources at the earliest US uranium processing facility
Oak Ridge Institute for Science and Education, 100 ORAU Way, Oak Ridge, TN 37831, USA
2 Oak Ridge National Laboratory, Oak Ridge, TN 37830, USA
3 National Council on Radiation Protection and Measurements, 7910 Woodmont Ave, Bethesda, MD 20814, USA ;
Vanderbilt University Medical School, 2525 West End Ave, Nashville, TN 37203, USA
* Corresponding author: firstname.lastname@example.org
Mallinckrodt Chemical Works (MCW) was the earliest uranium processing facility in the United States, beginning in 1942. The 2,514 workers included in the epidemiologic study were exposed to external gamma radiation, medical x-rays, internal radiation from intakes of pitchblende ore and its extracted radionuclides (mainly uranium isotopes and radium-226), and ambient levels of radon and its progeny .
© The Authors, published by EDP Sciences, 2019
This is an open access article distributed under the terms of the Creative Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Multiple sources of exposure data were available to a degree unique for an epidemiologic study . Personal film badges captured external exposures in 12,686 records. Additional external exposure included over 31,297 occupational medical x-rays and 210 exposure records from employment outside of MCW. Organ dose estimates were adjusted for photon energy and job-specific orientation of workers to the radiation source during processing. Intakes of uranium and radium were based on 39,451 uranium urine bioassays and 2,341 breath radon measurements using International Commission on Radiological Protection (ICRP) biokinetic models to estimate organ-specific radiation absorbed dose . Estimates of exposure to airborne radon and its progeny were available from 6,846 ambient radon measurements in work areas where radium-containing material was handled or stored, together with estimated exposure times in these areas based on job titles. Dose estimates for radon progeny were based on models and methods recently recommended by ICRP . Contributions of uranium dust and silica exposures to risk were estimated from 6,300gol worker-specific estimates of daily exposure to uranium dust . These data were used to calculate job-specific daily time-weighted average dust exposures. Because intake of uranium is best described by bioassay data, the dust exposures were used to explore potential associations with heavy metal toxicity and silica, independent of the radioactive content.
This comprehensive dosimetric approach follows methods outlined by the National Council on Radiation Protection Scientific Report 178 for the Million Worker Study . Annual doses were calculated for 6 organs: lung, brain, heart, kidney, colon and red bone marrow. Mean and median dose estimates for external, internal, and total radiation exposure for each organ of interest are listed in Table 1.
Summary of contributions of each exposure source to organ-specific doses
The largest organ doses were to the lung (mean 69.9 mGy; max 885 mGy) and heart (mean 47.5 mGy; max 737.6 mGy). External gamma dose was the largest contributor to dose for all organs, but doses from medical x-rays were also important. Average annual dust exposure was 15.1 mg/m3 (max 400 mg/m3).
The extensive collection of radiation exposure data available for the MCW workers provides the broadest application to date of the methodology endorsed by the NCRP  for construction of organ doses for use in epidemiologic studies. Such comprehensive dosimetry is required to produce the best radiation risk estimates for addressing current radiation issues on the effectiveness of low dose-rate exposures. These estimates are relevant to: projecting risks from environmental contamination from nuclear waste, terrorist events, and radiations used in medical diagnosis or treatment; compensation issues related to prior exposures; improved protection standards for workers and the public; evaluation of the safety and radiation risks for astronauts leaving Earth’s orbit; and appropriateness of the linear non-threshold model as a principle for radiation protection guidance.
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