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Recent Epidemiologic Studies and the Linear No-Threshold Model For Radiation Protection—Considerations Regarding NCRP Commentary 27

Shore, Roy E.1; Beck, Harold L.2; Boice, John D. Jr.3; Caffrey, Emily A.4; Davis, Scott5; Grogan, Helen A.6; Mettler, Fred A. Jr.7; Preston, R. Julian8; Till, John E.9; Wakeford, Richard10; Walsh, Linda11; Dauer, Lawrence T.12

doi: 10.1097/HP.0000000000001015
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National Council on Radiation Protection and Measurements Commentary 27 examines recent epidemiologic data primarily from low-dose or low dose-rate studies of low linear-energy-transfer radiation and cancer to assess whether they support the linear no-threshold model as used in radiation protection. The commentary provides a critical review of low-dose or low dose-rate studies, most published within the last 10 y, that are applicable to current occupational, environmental, and medical radiation exposures. The strengths and weaknesses of the epidemiologic methods, dosimetry assessments, and statistical modeling of 29 epidemiologic studies of total solid cancer, leukemia, breast cancer, and thyroid cancer, as well as heritable effects and a few nonmalignant conditions, were evaluated. An appraisal of the degree to which the low-dose or low dose-rate studies supported a linear no-threshold model for radiation protection or on the contrary, demonstrated sufficient evidence that the linear no-threshold model is inappropriate for the purposes of radiation protection was also included. The review found that many, though not all, studies of solid cancer supported the continued use of the linear no-threshold model in radiation protection. Evaluations of the principal studies of leukemia and low-dose or low dose-rate radiation exposure also lent support for the linear no-threshold model as used in protection. Ischemic heart disease, a major type of cardiovascular disease, was examined briefly, but the results of recent studies were considered too weak or inconsistent to allow firm conclusions regarding support of the linear no-threshold model. It is acknowledged that the possible risks from very low doses of low linear-energy-transfer radiation are small and uncertain and that it may never be possible to prove or disprove the validity of the linear no-threshold assumption by epidemiologic means. Nonetheless, the preponderance of recent epidemiologic data on solid cancer is supportive of the continued use of the linear no-threshold model for the purposes of radiation protection. This conclusion is in accord with judgments by other national and international scientific committees, based on somewhat older data. Currently, no alternative dose-response relationship appears more pragmatic or prudent for radiation protection purposes than the linear no-threshold model.

1New York University School of Medicine, New York, NY, and Radiation Effects Research Foundation, Hiroshima, Japan (retired);

2US Department of Energy (retired), New York, NY;

3National Council on Radiation Protection and Measurements, Bethesda, MD, and Vanderbilt University, Nashville, TN;

4Radian Scientific, Huntsville, AL;

5Fred Hutchinson Cancer Research Center, Seattle, WA;

6Cascade Scientific, Bend, OR;

7University of New Mexico, Albuquerque, NM;

8US Environmental Protection Agency, Research Triangle Park, NC;

9Risk Assessment Corporation, Neeses, SC;

10University of Manchester, Manchester, UK;

11University of Zurich, Zurich, Switzerland;

12Memorial Sloan Kettering Cancer Center, New York, NY.

Conflicts of interest: Richard Wakeford is a member of the Technical Working Party of the UK Compensation Scheme for Radiation-Linked Diseases and provides advice on radiological protection matters to the Tokyo Electric Power Company, Roy Shore and Julian Preston are members of the Low-Dose Scientific Advisory Committee for the Electric Power Research Institute (EPRI), and Lawrence Dauer has contracts with EPRI. The respective authors attest that these associations had no influence on their work on this report.

For correspondence contact Roy Shore at New York University School of Medicine, New York, NY (mailing address: 550 Trails End, Easton, PA 18040), or email at hrshore@gmail.com.

(Manuscript accepted 1 October 2018)

© 2019 by the Health Physics Society