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SC 1-16:  Uncertainties in the Estimation of Radiation Risks and Probability of Disease Causation

The goal of this report is to analyze the major aspects of uncertainty in relating absorbed doses in specific organs and tissues to the risk of disease, including cancer, noncancer health effects, and severe genetic defects. At the present time the risk of these radiation-induced health effects is largely based on long-term studies of atomic-bomb survivors in Japan, and to a lesser extent, on observations of individuals treated with radiation in medical procedures and survivors of radiation accidents. The report will analyze sources of uncertainty in making conversions from absorbed doses to estimates of health risks, and of calculating the probability of disease causation (PC).

This report will build upon the analysis in other NCRP reports of sources and magnitude of uncertainties in the estimation of radiation doses from exposure to external and internal sources of radiation. Topics to be addressed in this report include: (1) uncertainties in radiation weighting factors for gamma and x-ray radiations, alpha particles, beta particles, and neutrons; (2) uncertainties in estimation of relative tissue sensitivity (tissue weighting factors) used to calculate effective dose; (3) uncertainties in calculating total committed dose from internal emitters; and (4) calculation of overall uncertainty in estimation of health risks (cancer and non-cancer effects, severe genetic defects) associated with doses delivered by external and internal radiation sources, including effects of parameters such as age at exposure, gender, time since exposure, dose and dose rate effectiveness factors. The report will also provide a comprehensive analysis of these uncertainties on the estimation of probability of radiation-induced disease, including (1) application of radiation doses and associated uncertainties in estimation of probability of disease causation (including a review and analysis of the National Institute of Occupational Safety and Health (NIOSH) and National Cancer Institute versions of the Interactive RadioEpidemiological Program tables used to calculate PC); (2) evaluation of inherent uncertainties in calculating PC, or assigned share of excess relative risk for various types of cancer attributable to radiation exposure; (3) methods of improving existing procedures for estimating disease probability based on input doses and their uncertainties.

After funding was confirmed by NIOSH the candidate members of SC 1-16 were identified by NCRP and Dr. Preston, and were approved by the NCRP Board of Directors by mid-November, 2008. Following approval by the Board of Directors, letters of appointment and calendars were sent to the members of SC 1-16, and the initial Committee meeting is scheduled for March 26-27, 2009.  The Committee (1) revised its initial scope statement, (2) developed a topical outline for the report with Committee member assignments for timely in-depth development of each topic, (3) agreed  to a deadline of 15 July 2009 for elaborated outline development, (4) planned a teleconference in early August to review the status of section writing assignments, due for intra-Committee circulation in October, and (5) planned to hold a Committee meeting in late November or early December for review of draft materials and anticipated revisions/additions.

A teleconference was held (August 26, 2009) in which further refinement and elaboration of sections was undertaken (along with general writing assignments). A full Committee meeting was convened at NCRP offices on October 22-23 for the purpose of refining and coordinating writing assignments of report sections. Drafts are due by February 1, 2010.

A full Committee meeting took place at the NCRP offices on January 31 - February 1, 2011, for purposes of (1) reviewing the draft report and also (2) revising it to include where possible quantitative aspects of the various uncertainties, including dose, associated with the calculated risk assessments. A deadline was set for March 31, 2011, for receipt of all revisions. A subgroup of the Committee met in Bethesda in conjunction with the NCRP Annual Meeting to finalize their sections of the draft report. The draft report will be submitted for PAC review in April 2011.

A revised draft report was submitted for PAC review in April 2011. The draft is being revised based on the reviewers’ comments and will be submitted for Council review in the fourth quarter of 2011.

The membership of SC 1-16 is: R.J. Preston, Chairman J.D. Boice, Jr. A.B. Brill R. Chakraborty R. Conolly R. Hornung R.E. Shore G.E. Woloschak F.O. Hoffman, Advisor C.E. Land, Advisor M.W. Miller, NCRP Staff Consultant

Meetings: March 26-27, 2009 > August 26, 2009 > October 22-23, 2009 > April 7-8, 2010 >

SC 1-15 Radiation Protection and Science Goals
for Short-Term Lunar Missions >

SC 1-17 Second Cancers and Cardiopulmonary
Effects After Radiotherapy >

SC 1-20 Biological Effectiveness of Photons as a Function of Energy >

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