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Radiation Dose and the Impacts on Exposed Populations: Worker Exposures Session Q&A

Cassata, James

doi: 10.1097/HP.0000000000000029
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Why was there such a precipitous drop in 239Pu dose around 1980?

YOUR OBSERVATION is correct that there is a sharp drop in the reported 50th and 84th percentile urinary excretion of 239Pu at the Hanford site starting in the early 1980s. On 10 September 1981, the site practice changed from recording 0.025 dpm per sample to indicate a nondetectable value, to recording the exact result as measured. Because the data were no longer left-censored after this time, the fitted geometric mean and standard deviations for this and subsequent years were substantially reduced.

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Given increasing awareness of the emotional consequences of radiation-related disasters, what are you doing to deal with this phenomenon?

Although the National Institute for Occupational Safety and Health (NIOSH) does not have a formal program in place to provide emotional counseling to claimants, we have established a number of avenues for workers and claimants to personally communicate the facts of their case and to voice their concerns and frustrations. As part of the NIOSH dose reconstruction (DR) process, each claimant is provided a single point of contact within NIOSH to deal with their case. In addition, prior to the initiation of a DR, each claimant is interviewed to obtain any information that might be relevant to the case. Claimants are also provided the opportunity to voice their concerns during scheduled public comment sessions during routine meetings of the Advisory Board on Radiation and Worker Health. Finally, NIOSH participates in town hall meetings that are regularly scheduled by the U.S. Department of Labor to discuss newly added Special Exposure Cohort sites.

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How has the increased number of people in the “Special Exposure Cohorts” impacted the compensation program?

The Energy Employees Occupational Illness Compensation Program (EEOICPA) made provisions for certain classes of employees to be added to what is called the Special Exposure Cohort (SEC). Under certain conditions, workers in the SEC class do not require dose reconstructions for any of 22 cancers. In general, the National Institute for Occupational Safety and Health finds that about 60% of the cases in a designated class do not require dose reconstruction. Thus, the direct effect of adding a class to the SEC is a reduction in the number of dose reconstructions that must be completed for a site.

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For those cases with lung cancer, was the additive or multiplicative effect of smoking or radon exposure considered?

The effect of smoking on the development of lung cancer is explicitly considered in the probability of causation calculation. Because there is uncertainty about the nature of the interaction between smoking and radiation exposure, the excess relative risk per sievert is adjusted using an uncertainty distribution with various weights given to the additive or multiplicative interaction.

The adjustment for the interaction between radon exposure and smoking is also considered, but this adjustment, which relies on data collected from uranium miner studies, gives greater weight to the multiplicative interaction.

A detailed discussion of these adjustments can be found in an article by Kocher et al. (2008).

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How has the confounding factor of x-rays for tuberculosis screening or to serve as a baseline to assess potential later bone damage been evaluated, and how does this influence epidemiological studies?

As mentioned in the presentation, the radiation exposure associated with diagnostic x-rays is included in a worker’s dose reconstruction, as long as it was required as a condition of employment. Thus, if these types of x-rays were required, they would be included in the worker’s total occupational exposure.

While our division within the National Institute for Occupational Safety and Health (NIOSH) is not engaged in occupational epidemiologic studies, it would be important to consider exposure associated with these types of x-rays in risk studies.

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Can the reconstructed doses developed for compensation be credibly recalculated for use in epidemiological studies?

It is believed that the National Institute for Occupational Safety and Health (NIOSH) has collected sufficient data so that the doses reconstructed for compensation purposes could be recalculated for use in epidemiological studies. This would, of course, require additional funding that is beyond the scope of our current mission.

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Are attorneys involved in compensation activities?

Yes, attorneys do represent some claimants within the Energy Employees Occupational Illness Compensation Program (EEOICPA).

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What are the main factors that resulted in the maximum individual exposures being so different in the four largest nuclear accidents (Windscale, Three Mile Island, Chernobyl, and Fukushima)?

The four accidents were very different. The steam explosion at Chernobyl resulted in the loss of the containment and in a series of fires that had to be extinguished quickly. This is the reason for the very high radiation doses received during the first day of the accident. At Fukushima, the reason for the high exposures has not been provided officially (as far as I know), but it seems that air mainly contaminated with 131I found its way to the reactor control room, where the workers were not equipped with respirators and had not taken potassium-iodide tablets. At Three Mile Island, the exposure situation was well managed, so that the maximum doses were relatively low. I am not familiar enough with the Windscale accident to explain why the maximum doses to the workers were also relatively low.

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What fraction of the total Chernobyl liquidator workforce was actively monitored for radiation dose?

I do not think that there is any published information on this topic. According to unpublished information, ~15–20% of the Chernobyl workforce was actively monitored by means of personal dosimeters. The other two methods that were used to determine dose at the time of exposure were: (1) the group assessment method (a personal dosimeter was worn by one member of a group of liquidators assigned to perform a particular task, and all members of the group were given the same dose); and (2) the calculation method (the dose to a group of liquidators was calculated in advance from the dose rate at the work location and the planned duration of work). Altogether, 48% of the workers had a recorded dose (UNSCEAR 2010/2011).

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How are medical exposures tracked for the clinical use of x-rays/computed tomography/nuclear medicine procedures on soldiers for screening or injury?

This question falls outside of the speaker’s expertise. For further information on this topic, interested parties should contact: Office of the Assistant Secretary of Defense for Public Affairs, 1400 Defense Pentagon, Washington, DC 20301-1400, (703) 571-3343. For further information see:

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An atmosphere detonation participant was informed 30 y ago that his occupational dose was classified information. Are exposed individuals able to receive their personal doses from that time today?

Yes, this information is no longer classified. A U.S. military service member or civilian may request this information by calling this toll-free number: (800) 462-3683; or emailing; or writing to Defense Threat Reduction Agency, J9-NTSN/NTPR, 8725 John J. Kingman Road, MSC 6201, Fort Belvoir, VA 22060-6201. For further information see:

Introduction of Radiation Exposure of U.S. Military Individuals (Video 2:19,

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Kocher DC, Apostoaei AI, Henshaw RW, Hoffman FO, Schubauer-Berigan MK, Stancescu DO, Thomas BA, Trabalka JR, Gilbert ES, Land CE. Interactive RadioEpidemiological Program (IREP): a web-based tool for estimating probability of causation/assigned share of radiogenic cancers. Health Phys 95 (1): 119–147; 2008.
UNSCEAR. Sources and effects of ionizing radiation. UNSCEAR 2008 report to the general assembly, with scientific annexes. New York: United Nations Publications; United Nations Scientific Committee on the Effects of Atomic Radiation; 2010/2011.
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