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Federal Register / Vol. 86, No. 156 / Tuesday, August 17, 2021 / Proposed Rules <100 mGy <10 rad is uncertain but small. 42
International Authoritative Scientific Advisory Bodies Favoring Continued Use of LNT
The ICRP, in its Publication No. 99, Low-dose Extrapolation of Radiationrelated Cancer Risk, stated that we are uncertain about the likelihood of a dose threshold, and that, in addition, if there should be a dose threshold, we are uncertain about what dose level it would be. 43 The ICRP further stated that the mechanistic and experimental data discussed in this monograph tend to give weight to a non-threshold model, as do the solid tumour data in the Japanese atomic bomb study. 44 The ICRP concluded that the LNT theory remains the most prudent risk model for the practical purposes of radiological protection. 45 The ICRP reaffirmed this conclusion in its Publication No. 103, The 2007 Recommendations of the International Commission on Radiological Protection 2007.46 In Publication No. 103, the ICRP
acknowledged that the LNT model was not universally accepted as a biological truth and that the possibility of a lowdose threshold could not be ruled out, but because we do not actually know what level of risk is associated with very-low-dose exposure, the LNT
model is considered to be a prudent judgement for public policy aimed at avoiding unnecessary risk from exposure. 47 While a 2005 joint French Academy of Sciences and National Academy of Medicine review expressed doubts on the validity of using LNT for evaluating the carcinogenic risk of low doses, this review noted that the LNT concept can be a useful pragmatic tool for assessing rules in radioprotection for doses above 10 mSv 1 rem. 48
The IAEA, in its 1997 nuclear safety review published in August 1998, stated that some researchers have interpreted experimental results and epidemiological findings as providing evidence that low doses of radiation are much more harmful than the LNT
hypothesis implies. A number of
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42 Id.
43 ICRP, Low-dose Extrapolation of Radiationrelated Cancer Risk, Pub. No. 99 2005, at 108.
44 Id.
45 Id., at 113.
46 ICRP, The 2007 Recommendations of the International Commission on Radiological Protection, Pub. No. 103 2007, at 36 and 38, 65
67.
47 Id., at A178 and A180.
48 Academy of Sciences and National Academy of Medicine France, Dose-Effect Relationships and Estimation of the Carcinogenic Effects of Low Doses of Ionizing Radiation 2005, at 5.

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mechanisms have been proposed by which this might occur, a recent example being the phenomenon of genomic instability. 49 The IAEA report concluded that from the evidence available at the present time, however, the LNT hypothesis continues to seem the most radiobiologically defensible basis for radiation protection recommendations. It is also a workable hypothesis that can underpin systems of regulation which, when applied reasonably, provide sound and sensible management of the risks from radiation. 50 The current IAEA
radiation safety standards, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, published in 2014, relies upon the LNT model, stating that the LNT model is the working hypothesis on which the IAEAs safety standards are based. It is not provenindeed it is probably not provablefor low doses and dose rates, but it is considered the most radiobiologically defensible assumption on which to base safety standards. 51
Comments of Federal Agencies In addition to the findings of the national and international authoritative scientific advisory bodies, three Federal agencies provided comments on the petitions and supported the continued use of the LNT model as the basis for the NRCs radiation protection program.
The three agencies are the National Cancer Institute NCI, National Institutes of Health, Department of Health and Human Services; National Institute for Occupational Safety and Health NIOSH, Centers for Disease Control and Prevention, Department of Health and Human Services; and the Radiation Protection Division, Office of Air and Radiation, Environmental Protection Agency EPA. Furthermore, the NRCs Advisory Committee on the Medical Uses of Isotopes ACMUI 52
recommends that the NRC continue to rely upon the LNT model.
NCI provided detailed comments during the 2015 public comment period 49 IAEA, Measures to Strengthen International Co-Operation in Nuclear, Radiation and Waste Safety, Nuclear Safety Review for the Year 1997
August 1998, Attachment at 32.
50 Id.
51 IAEA, Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, General Safety Requirements Part 3
2014, at 401.
52 The ACMUI is an official advisory body to the NRC established in accordance with the Federal Advisory Committee Act FACA, 5 U.S.C. App. 2.
The ACMUI advises the NRC on policy and technical issues that arise in the regulation of the medical uses of radioactive material in diagnosis and therapy.

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for the petitions.53 In response to the petitioners assertions that several epidemiologic studies showed that individuals exposed to higher doses of radiation were less likely or no more likely to develop cancer than those who received lower doses of radiation, NCI, in its comments, noted the limitations of such studies. NCI explained that because epidemiologic studies are observational and not controlled experiments, differences in risks in exposed and unexposed may reflect differences in life style factors such as smoking and may not necessarily result from radiation exposure. 54 In addition, NCI stated in its comments:
the petitions are selective in citing studies that appear to support hormesis or a threshold and omitting mention of the many studies that provide evidence of a doseresponse at low doses. In some cases, analyses published many years ago are cited, when more recent analyses based on current follow-up of the same populations, often with improved dose estimates, do not support their claims.55

In this regard, NCI, in its comments, provided several examples of such studies and the more recent follow-up analyses that did not support the petitioners assertions but provided evidence of a dose-response at low doses, 56 especially among children.
NIOSH also provided detailed comments during the 2015 public comment period.57 NIOSH, in its comments, noted that the lines of evidence given by the petitioners are not new and are fundamentally the same as those rejected by the BEIR VII
committee. 58 NIOSHs comments are based, in part, upon a large study of nuclear workers, completed in 2015, which found that even tiny doses slightly boost the risk of leukemia the study has been informally referred to as the international nuclear workers or 53 NCI, A. Berrington de Gonza lez, et al., Contribution to Nuclear Regulatory Commission NRC comments on petitions on linear nothreshold model and standards for protection against radiation November 19, 2015 NCI 2015.
The specific component of NCI that provided the comments was the Radiation Epidemiology Branch, Division of Cancer Epidemiology and Genetics.
54 Id. at 1. See also Boice at 1089 All models are wrong, but some are useful for radiation protection. LNT is an assumption. It is unlikely to be scientifically validated in the low-dose domain, and not by epidemiology.
55 NCI 2015, at 1.
56 Id., at 2.
57 NIOSH, S. Toye, Comments of the National Institute for Occupational Safety and Health on the Nuclear Regulatory Commission Notice of Docketing and Request for Comment on Linear NoThreshold Model and Standards for Protection Against Radiation, September 11, 2015 NIOSH
2015.
58 Id., at 2.

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