This section of the FEDERAL REGISTER

contains notices to the public of the proposed

issuance of rules and regulations. The

purpose of these notices is to give interested

persons an opportunity to participate in the

rule making prior to the adoption of the final

rules.

Proposed Rules Federal Register

45923 

Vol. 86, No. 156 

Tuesday, August 17, 2021 

1 Dr. Doss was the first of several signatories on 

the February 24, 2015, correspondence. The 

correspondence identified the signatories as 

members or associate members of Scientists for 

Accurate Radiation Information (SARI). There is no 

indication in the February 24, 2015, 

correspondence that SARI, as an organization, 

formally endorsed the petition from Dr. Doss, et al. 

2 80 FR 50804–05; August 21, 2015. 

3 .The terms ‘‘occupational worker,’’ ‘‘radiation 

worker,’’ ‘‘nuclear worker,’’ and ‘‘worker’’ are used 

interchangeably in this document. 

NUCLEAR REGULATORY 

COMMISSION 

10 CFR Part 20 

[Docket No. PRM–20–28, PRM–20–29, and 

PRM–20–30; NRC–2015–0057] 

Linear No-Threshold Model and 

Standards for Protection Against 

Radiation 

AGENCY: Nuclear Regulatory 

Commission. 

ACTION: Petition for rulemaking; denial. 

SUMMARY: The U.S. Nuclear Regulatory 

Commission (NRC) is denying three 

petitions for rulemaking (PRMs), 

submitted by Dr. Carol S. Marcus, Mr. 

Mark L. Miller, Certified Health 

Physicist, and Dr. Mohan Doss, et al. 

(collectively, the petitioners) in 

correspondence dated February 9, 2015, 

February 13, 2015, and February 24, 

2015, respectively. The petitioners 

request that the NRC amend its 

regulations based on what they assert is 

new science and evidence that 

contradicts the linear no-threshold 

(LNT) dose-effect model that serves as 

the basis for the NRC’s radiation 

protection regulations. The NRC 

docketed these petitions on February 20, 

2015, February 27, 2015, and March 16, 

2015, and assigned them Docket 

Numbers PRM–20–28, PRM–20–29, and 

PRM–20–30, respectively. The NRC is 

denying the three petitions because they 

fail to present an adequate basis 

supporting the request to discontinue 

use of the LNT model. The NRC has 

determined that the LNT model 

continues to provide a sound regulatory 

basis for minimizing the risk of 

unnecessary radiation exposure to both 

members of the public and radiation 

workers. Therefore, the NRC will 

maintain the current dose limit 

requirements contained in its 

regulations. 

DATES: The dockets for PRM–20–28, 

PRM–20–29, and PRM–20–30 are closed 

on August 17, 2021. 

ADDRESSES: Please refer to Docket ID 

NRC–2015–0057 when contacting the 

NRC about the availability of 

information for this action. You may 

obtain publicly-available information 

related to this action by any of the 

following methods: 

• Federal Rulemaking Website: Go to 

https://www.regulations.gov and search 

for Docket ID: NRC–2015–0057. Address 

questions about NRC dockets to Dawn 

Forder, telephone: 301–415–3407, 

email: Dawn.Forder@nrc.gov. For 

technical questions, contact individual 

listed in the FOR FURTHER INFORMATION

CONTACT section of this document. 

• NRC’s Agencywide Documents 

Access and Management System 

(ADAMS): You may obtain publiclyavailable documents online in the 

ADAMS Public Documents collection at 

https://www.nrc.gov/reading-rm/ 

adams.html. To begin the search, select 

‘‘ADAMS Public Documents’’ and then 

select ‘‘Begin Web-based ADAMS 

Search.’’ For problems with ADAMS, 

please contact the NRC’s Public 

Document Room (PDR) reference staff at 

1–800–397–4209, 301–415–4737, or by 

email to pdr.resource@nrc.gov. For the 

convenience of the reader, a list of 

materials referenced in this document 

are provided in Section V, ‘‘Availability 

of Documents.’’ 

• Attention: The PDR, where you may 

examine and order copies of public 

documents, is currently closed. You 

may submit your request to the PDR via 

email at pdr.resource@nrc.gov or call 1– 

800–397–4209 between 8:00 a.m. and 

4:00 p.m. (EST), Monday through 

Friday, except Federal holidays. 

FOR FURTHER INFORMATION CONTACT: 

Vanessa Cox, Office of Nuclear Material 

Safety and Safeguards, telephone: 301– 

415–8342; email: Vanessa.Cox@nrc.gov; 

U.S. Nuclear Regulatory Commission, 

Washington, DC 20555–0001. 

SUPPLEMENTARY INFORMATION: 

I. The Petitions 

Section 2.802 of title 10 of the Code 

of Federal Regulations (10 CFR), 

‘‘Petition for rulemaking—requirements 

for filing,’’ provides an opportunity for 

any interested person to petition the 

Commission to issue, amend, or rescind 

any regulation in 10 CFR chapter I. By 

correspondence dated February 9, 2015, 

February 13, 2015, and February 24, 

2015, respectively, the NRC received 

three similar petitions from Dr. Carol S. 

Marcus, Mark L. Miller, CHP, and 

Mohan Doss, Ph.D., et al.1 The NRC 

published a notice of docketing for the 

three petitions in the Federal Register 

on June 23, 2015 (80 FR 35870), and 

requested public comment. The public 

comment period was initially set to 

close on September 8, 2015, but was 

extended to November 19, 2015.2

The petitioners request that the NRC 

amend 10 CFR part 20, ‘‘Standards for 

Protection against Radiation,’’ to 

discontinue use of the LNT model as the 

primary scientific basis for the agency’s 

radiation protection standards. The 

petitioners’ assertion is that the use of 

the LNT model is no longer valid based 

on various scientific studies. In 

particular, the petitioners advance the 

concept of radiation hormesis, which 

posits that low doses of ionizing 

radiation protect against the deleterious 

effects of high doses of radiation and 

result in beneficial effects to humans. 

Therefore, the petitioners request that 

the NRC amend its dose limits for 

occupational workers 3 and members of 

the public as follows: 

• Maintain worker doses ‘‘at present 

levels, with allowance of up to 100 mSv 

(10 rem) effective dose per year if the 

doses are chronic’’; 

• Remove the As Low As Is 

Reasonably Achievable (ALARA) 

principle entirely from the regulations, 

because they claim that ‘‘it makes no 

sense to decrease radiation doses that 

are not only harmless but may be 

hormetic’’; 

• Raise the public dose limits to be 

the same as the worker doses, because 

they claim that ‘‘these low doses may be 

hormetic’’; and 

• ‘‘End differential doses to pregnant 

women, embryos and fetuses, and 

children under 18 years of age.’’ 

II. Background 

In 1991, the NRC issued the 10 CFR 

part 20 final rule, which established the 

current regulatory framework for the 

NRC’s radiation protection regulations. 


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45924 Federal Register / Vol. 86, No. 156 / Tuesday, August 17, 2021 / Proposed Rules 

4 10 CFR 20.1101(a). 

5The Atomic Energy Act of 1954 assigned the 

Atomic Energy Commission (AEC) the functions of 

both encouraging the use of nuclear power and 

regulating its safety. The AEC was the predecessor 

agency to the NRC. 

6The terms ‘‘ionizing radiation’’ and ‘‘radiation’’ 

are used interchangeably in this document. 

7 ‘‘The biological dose or dose equivalent, given 

in rems or sieverts (Sv), is a measure of the 

biological damage to living tissue as a result of 

radiation exposure.’’ NRC Glossary, Definition of 

Dose, https://www.nrc.gov/reading-rm/basic-ref/ 

glossary/dose.html. 

8For example, in the October 2015 ACMUI 

teleconference, Dr. Zanzonico noted that ‘‘[w]e all 

recognize that the issue of the linear no-threshold 

model of radiation carcinogenesis versus a hormetic 

model versus an alternative model remains highly 

controversial and really engenders very strong 

emotions from folks on different sides of the 

question.’’ ACMUI, Official Transcript of 

Proceedings (October 28, 2015), at 18–19. 

9 ICRP, ‘‘Low-dose extrapolation of radiationrelated cancer risk,’’ Pub. No. 99 (2005), at 38. 

10 56 FR 23360; May 21, 1991. Under current NRC 

regulations, each NRC licensee must ensure that its 

operations do not exceed, for each member of the 

public, a total effective dose limit of 0.1 rem (1 

mSv) in a calendar year. § 20.1301(a)(1). For 

occupational workers, the primary annual dose 

limit, per licensee, is a total effective dose 

equivalent of 5 rems (50 mSv). § 20.1201(a)(1)(i). 

11 Id. 

All NRC licensees are subject to the 

NRC’s radiation protection requirements 

set forth in 10 CFR part 20. These 

requirements are designed to protect 

both members of the public and 

occupational workers from harm that 

could be caused by a licensee’s use of 

radioactive materials. In accordance 

with § 20.1101, ‘‘Radiation protection 

programs,’’ each licensee ‘‘shall 

develop, document, and implement a 

radiation protection program 

commensurate with the scope and 

extent of licensed activities.’’ 4

The LNT model has been the 

underlying premise of much of the 

NRC’s radiation protection regulations 

since the late 1950s.5 The LNT model 

provides that ionizing radiation 6 is 

always considered harmful and that 

there is no threshold below which an 

amount of radiation exposure to the 

human body is not harmful. The LNT 

model further holds that biological 

damage caused by ionizing radiation 

(the cancer risk and adverse hereditary 

effects) is directly proportional to the 

amount of radiation exposure to the 

human body (response linearity). Thus, 

the higher the amount of radiation 

exposure, or dose,7 the higher the 

likelihood that the human receptor will 

suffer biological damage. The validity of 

the LNT model has been the subject of 

dispute within the scientific community 

for decades.8 The NRC’s standards for 

protection against radiation, which are 

contained in 10 CFR part 20, are 

underpinned by the LNT model. These 

radiation protection standards provide 

requirements for— 

• Dose limits for radiation workers 

and members of the public, 

• Monitoring and labeling radioactive 

materials, 

• Posting signs in and around 

radiation areas, and 

• Reporting the theft or loss of 

radioactive material. 

The petitioners do not dispute that 

high doses of radiation exposure are 

harmful to the human body. Instead, 

their argument centers on low doses of 

radiation exposure, generally doses 

below 10 rem (100 mSv), the effects of 

which are difficult to quantify. In this 

regard, the petitioners contend that 

there is a threshold below which 

radiation exposure to the human body is 

not harmful. As described by the 

International Commission on 

Radiological Protection (ICRP) in its 

Publication No. 99, ‘‘Low-dose 

extrapolation of radiation-related cancer 

risk,’’ the threshold theory posits that 

‘‘there is some threshold dose below 

which there is either no radiationrelated health detriment or a radiationrelated health benefit that outweighs 

any detriment. If the threshold was a 

universal value for all individuals and 

all tissues, a consequence of the theory 

is that, at some point, a very low dose 

to any number of people would have no 

associated risk and could be ignored.’’ 9

The petitioners also advance a 

companion concept to the existence of 

a threshold, the radiation hormesis 

concept (hormesis), which provides that 

exposure of the human body to low and 

very low levels of ionizing radiation is 

beneficial to the human body. 

III. Petitioners’ Assertions 

The petitioners request to amend NRC 

dose limits (dose limit for occupational 

workers; dose limit for embryos, fetuses, 

and pregnant workers; and the dose 

limits for the public) as well as to 

remove the ALARA principle for the 

NRC’s regulations. The requested 

amendments to the regulations were 

supported by several assertions made by 

the petitioners. The NRC reviewed each 

assertion separately, as outlined in this 

section and followed by the NRC’s 

response. 

Petitioners’ Assertion That LNT Is Not 

Justified by Current Science 

The petitioners assert that current 

science does not justify the use of the 

LNT model and that there is a threshold 

below which radiation exposure to the 

human body is not harmful. 

NRC’s Response 

The NRC does not agree with the 

petitioners’ assertion. Exposure to 

ionizing radiation is a known cancer 

risk factor for humans. The LNT model 

assumes that, in the long term, 

biological damage caused by ionizing 

radiation (i.e., cancer risk and adverse 

hereditary effects) is directly 

proportional to the dose. The NRC 

acknowledges the difficulties inherent 

in determining the amount of damage to 

the human body caused by low doses of 

radiation. The NRC, however, does not 

use the LNT model to assess the actual 

risk of low dose radiation. Instead, the 

NRC uses the LNT model as the basis for 

a regulatory framework that meets the 

‘‘adequate protection’’ standard of the 

Atomic Energy Act of 1954, as amended 

(AEA). Furthermore, the LNT model is 

applied so that the framework can be 

effectively implemented by an agency 

that regulates diverse categories of 

licensees, from commercial nuclear 

power plants to individual industrial 

radiographers and nuclear medical 

practices. The NRC’s use of the LNT 

model as the basis for its radiation 

protection regulations is premised upon 

the findings and recommendations of 

national and international authoritative 

scientific bodies, such as the ICRP, that 

have expertise in the science of 

radiation protection. 

The NRC issued the framework for its 

current 10 CFR part 20 radiation 

protection regulations in 1991.10 The 

NRC acknowledged the role of the 

national and international authoritative 

scientific bodies in the 1991 final rule, 

stating that ‘‘[t]he [U.S. Atomic Energy 

Commission] and the NRC have 

generally followed the basic radiation 

protection recommendations of the 

[ICRP] and its U.S. counterpart, the 

National Council on Radiation 

Protection and Measurements (NCRP), 

in formulating basic radiation protection 

standards.’’ The 1991 final rule 

explained that the NRC based its 

radiation protection regulations upon 

three assumptions. The first assumption 

concerned the use of the LNT model, 

which was described as follows: 

The first assumption, the linear 

nonthreshold dose-effect relationship, 

implies that the potential health risk is 

proportional to the dose received and that 

there is an incremental health risk associated 

with even very small doses, even radiation 

doses much smaller than doses received from 

naturally occurring radiation sources. These 

health risks, such as cancer, are termed 

stochastic because they are statistical in 

nature; i.e., for a given level of dose, not 

every person exposed would exhibit the 

effect.11

The other two assumptions 

supporting the NRC’s radiation 


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12The NRC defines the term ‘‘stochastic effects’’ 

as meaning ‘‘health effects that occur randomly and 

for which the probability of the effect occurring, 

rather than its severity, is assumed to be a linear 

function of dose without threshold. Hereditary 

effects and cancer incidence are examples of 

stochastic effects.’’ § 20.1003. The NRC defines the 

term ‘‘nonstochastic effects’’ as meaning ‘‘health 

effects, the severity of which varies with the dose 

and for which a threshold is believed to exist. 

Radiation-induced cataract formation is an example 

of a nonstochastic effect (also called a deterministic 

effect).’’ Id. 

13 56 FR 23360. 

14 Id. 

15 Id. 

16 Id. 

17 Id., at 23360–61. 

18 42 U.S.C. 2011 et seq. 

19 56 FR at 23360. In its Publication 26, the ICRP 

states ‘‘[f]or radiation protection purposes it is 

necessary to make certain simplifying assumptions. 

One such basic assumption underlying the 

Commission’s recommendations is that, regarding 

stochastic effects, there is, within the range of 

exposure conditions usually encountered in 

radiation work, a linear relationship without 

threshold between dose and the probability of an 

effect.’’ ICRP Pub. No. 26. 

20 56 FR at 23360. The ‘‘Federal Radiation 

Protection Guidance for Occupational Exposure’’ 

concerned the protection of workers from ionizing 

radiation and was published in the Federal Register 

on January 27, 1987 (52 FR 2822). The guidance 

was prepared by the Environmental Protection 

Agency, the NRC, and several other Federal 

agencies having an agency program or function that 

involved the use of radioactive material. The 

guidance stated ‘‘[w]e have considered these [ICRP] 

recommendations, among others, and believe that it 

is appropriate to adopt the general features of the 

ICRP approach in radiation protection guidance to 

Federal agencies for occupational exposure;’’ and 

‘‘[b]ased on extensive but incomplete scientific 

evidence, it is prudent to assume that at low levels 

of exposure the risk of incurring either cancer or 

hereditary effects is linearly related to the dose 

received in the relevant tissue.’’ 52 FR at 2824. 

21Position Statement of the Health Physics 

Society (HPS), PS008–2, ‘‘Uncertainty in Risk 

Assessment,’’ Adopted July 1993, Revised April 

1995, February 2013. 

22HPS PS–008–2 at 2. 

23 Id. 

24The NAS ‘‘is a private, non-profit society of 

distinguished scholars. Established by an Act of 

Congress . . . the NAS is charged with providing 

independent, objective advice to the nation on 

matters related to science and technology. Scientists 

are elected by their peers to membership in the 

NAS for outstanding contributions to research.’’ 

http://www.nasonline.org/about-nas/mission/. 

25The NCRP is a private, non-profit corporation 

whose mission is ‘‘to formulate and widely 

disseminate information, guidance and 

recommendations on radiation protection and 

measurements which represent the consensus of 

leading scientific thinking.’’ http://ncrponline.org/ 

about/mission/. 

26E.g., 56 FR at 23360. 

27NAS, ‘‘Health Risks from Exposure to Low 

Levels of Ionizing Radiation, BEIR VII—Phase 2’’ 

(2006) (NAS BEIR VII). The BEIR VII report may be 

viewed online at https://www.nap.edu/catalog/ 

11340/health-risks-from-exposure-to-low-levels-ofionizing-radiation. The NRC was one of several 

Federal agencies that provided funding to NAS for 

the BEIR VII study. 

protection requirements relate to 

stochastic and nonstochastic effects. 

Stochastic risks or effects from exposure 

to radiation are primarily the long-term 

potential for cancer induction and 

adverse hereditary effects, while 

deterministic or nonstochastic risks or 

effects are those that can be directly 

correlated with exposure to high or 

relatively high doses of radiation, such 

as the formation of cataracts.12 The 

NRC’s second assumption was that the 

severity of a stochastic effect is 

independent of, or not related to, the 

amount of radiation dose received.13

The NRC’s third assumption was that 

there is an ‘‘apparent threshold; i.e., a 

dose level below which the 

[nonstochastic] effect is unlikely to 

occur.’’ 14 Therefore, the LNT model 

only applies to stochastic effects. 

In the 1991 final rule, the NRC stated 

that these ‘‘assumptions are necessary 

because it is generally impossible to 

determine whether or not there are any 

increases in the incidence of disease at 

very low doses and low dose rates, 

particularly in the range of doses to 

members of the general public resulting 

from NRC-licensed activities.’’ 15 The 

NRC further noted that there is 

‘‘considerable uncertainty in the 

magnitude of the risk at low doses and 

low dose rates.’’ 16 The NRC concluded: 

In the absence of convincing evidence that 

there is a dose threshold or that low levels 

of radiation are beneficial, the Commission 

believes that the assumptions regarding a 

linear nonthreshold dose-effect model for 

cancers and genetic effects and the existence 

of thresholds only for certain nonstochastic 

effects remain appropriate for formulating 

radiation protection standards and planning 

radiation protection programs.17

Thus, the NRC, as a regulator 

statutorily charged under the AEA 18

with protecting the public from 

radiological harm, determined in 1991 

that it was prudent to assume the 

validity of the LNT model because of 

the considerable uncertainty with 

respect to the effect of low doses of 

radiation. The NRC’s 1991 final rule was 

premised, to a large extent, upon the 

recommendations of ICRP Publication 

26, ‘‘Recommendations of the 

International Commission on 

Radiological Protection’’ (1977), several 

of which, in turn, were premised upon 

the LNT model.19 The 1991 final rule 

also referenced the government-wide 

‘‘Federal Radiation Protection Guidance 

for Occupational Exposure,’’ signed by 

President Reagan in 1987, which was 

similarly premised upon the ICRP 

Publication 26 recommendations.20

The NRC’s position remains 

unchanged from 1991. Convincing 

evidence has not yet demonstrated the 

existence of a threshold below which 

there would be no stochastic effects 

from exposure to low radiation doses. 

As such, the NRC’s view is that the LNT 

model continues to provide a sound 

basis for a conservative radiation 

protection regulatory framework that 

protects both the public and 

occupational workers. 

Despite the various studies cited by 

the petitioners, uncertainty and lack of 

consensus persists in the scientific 

community about the health effects of 

low doses of radiation. For example, the 

Health Physics Society (HPS) has stated 

that ‘‘[h]ealth risks of radiation exposure 

can only be estimated with a reasonable 

degree of scientific certainty at radiation 

levels that are orders of magnitude 

greater than limits established by 

regulation for protection of the 

public.’’ 21 The HPS has further stated 

‘‘that radiation protection literature is 

filled with differing views as to the 

shape of the radiation dose-response 

curve at low doses and dose rates.’’ 22

According to HPS, ‘‘[s]ome data support 

a linear no-threshold model, whereas 

other data support models that predict 

lower estimates of risk and perhaps 

even a threshold below which no 

detectable radiation health risk 

exists.’’ 23

Although there are studies and other 

scholarly papers that support the 

petitioners’ assertions, there are also 

studies and findings that support the 

continued use of the LNT model, 

including those by national and 

international authoritative scientific 

advisory bodies. Those authoritative 

scientific advisory bodies that have a 

specialty in the subject matter area of 

radiation protection include, 

domestically, the federally chartered 

National Academy of Sciences (NAS) 24

and NCRP,25 and, internationally, the 

ICRP and the International Atomic 

Energy Agency (IAEA). All four of these 

bodies support the continued use of the 

LNT model. It has been the longstanding 

practice of the NRC to generally place 

significant weight on the 

recommendations of these authoritative 

scientific advisory bodies.26

National Authoritative Scientific 

Advisory Bodies Favoring Continued 

Use of LNT 

In 2006, the NAS published its 

Biological Effects of Ionizing Radiation 

(BEIR) VII report, ‘‘Health Risks from 

Exposure to Low Levels of Ionizing 

Radiation,’’ the seventh in a series of 

reports that concern the health effects 

from low doses of radiation, and by 

extension, the appropriateness of the 

LNT model.27 The report was prepared 

by the Committee to Assess Health Risks 

from Exposure to Low Levels of Ionizing 


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28 Id., at vii. 

29 In its report, the BEIR VII committee ‘‘defined 

low dose as doses in the range of near zero up to 

about 100 mSv (0.1 Sv) of low-[linear energy 

transfer] radiation.’’ NAS BEIR VII at 2. The NCRP 

has considered a ‘‘very low dose’’ to be a dose 

below 1 rem or 10 mSv. NCRP, ‘‘Implications of 

Recent Epidemiologic Studies for the Linear 

Nonthreshold Model and Radiation Protection,’’ 

Commentary 27 (April 24, 2018), at 66. 

30NAS BEIR VII at 10. 

31 Id. 

32 Id., at 323. 

33NCRP, ‘‘Limitation of Exposure to Ionizing 

Radiation,’’ Report No. 116 (1993), at 10 (emphasis 

in the original). 

34NCRP, ‘‘Evaluation of the Linear-Nonthreshold 

Dose-Response Model for Ionizing Radiation,’’ 

Report No. 136 (2001), at 1. 

35 Id., at 208. 

36 Id., at 7. See also id., at 48–49 (The NCRP also 

stated ‘‘[t]herefore, if radiation-induced cancer 

results directly from the induction of mutations 

involved in the oncogenic pathway, the data 

reported do not support the existence of a 

threshold.’’); and id., at 77 (The NCRP also noted 

that ‘‘the majority of studies report linear doseresponse relationships in the lower dose range with 

the coefficient being quite similar to the alpha 

coefficient of the in vitro linear-quadratic doseresponse curves.’’). 

37 J. Boice, Jr., ‘‘The linear nonthreshold (LNT) 

model as used in radiation protection: An NCRP 

update,’’ International Journal of Radiation Biology, 

Vol. 93, No. 10 (2017), at 1080 (Boice). 

38 Id. 

39 Id., at 1089. 

40NCRP, ‘‘Implications of Recent Epidemiologic 

Studies for the Linear Nonthreshold Model and 

Radiation Protection,’’ Commentary 27 (April 24, 

2018), at 139. The acronym ‘‘DDREF’’ refers to the 

dose and dose-rate effectiveness factor, and is used 

to extrapolate the risk of cancer induction from high 

doses received acutely, and thus measurable, to 

those low doses, which cannot be measured and are 

the focus of the LNT model. Id., at 20 22–23, and 

34. 

41 Id., at 140. 

Radiation that was established by NAS 

for the purpose of advising ‘‘the U.S. 

government on the relationship between 

exposure to ionizing radiation and 

human health.’’ 28 The BEIR VII report 

focused on health effects from low doses 

of radiation (below 10 rem or 100 

mSv) 29 and updated the findings of the 

previous report of low dose radiation, 

the 1990 BEIR V. 

The BEIR VII committee analyzed 

epidemiologic data and biological data, 

including a study of the survivors of the 

Hiroshima and Nagasaki atomic bomb 

attacks and studies of cancer in 

children. The BEIR VII committee found 

‘‘that the preponderance of information 

indicates that there will be some risk, 

even at low doses’’ and ‘‘that there is no 

compelling evidence to indicate a dose 

threshold below which the risk of tumor 

induction is zero.’’ 30 The BEIR VII 

committee further found ‘‘[w]hen the 

complete body of research on this 

question is considered, a consensus 

view emerges. This view says that the 

health risks of ionizing radiation, 

although small at low doses, are a 

function of dose.’’ 31 The BEIR VII 

committee concluded that ‘‘current 

scientific evidence is consistent with 

the hypothesis that there is a linear, nothreshold dose-response relationship 

between exposure to ionizing radiation 

and the development of cancer in 

humans.’’ 32

Following the publication of BEIR V, 

the NCRP updated its radiation 

protection recommendations in its 1993 

report, NCRP Report No. 116, 

‘‘Limitation of Exposure to Ionizing 

Radiation.’’ Although the NCRP 

acknowledged that it could not exclude 

the possibility of no health risk from 

low doses, the NCRP expressed its 

reliance on the LNT model as the basis 

for several of its recommendations, 

Based on the hypothesis that genetic effects 

and some cancers may result from damage to 

a single cell, the Council assumes that, for 

radiation-protection purposes, the risk of 

stochastic effects is proportional to dose 

without threshold, throughout the range of 

dose and dose rates of importance in routine 

radiation protection. Furthermore, the 

probability of response (risk) is assumed, for 

radiation protection purposes, to accumulate 

linearly with dose.33

In 2001, the NCRP published Report 

No. 136, ‘‘Evaluation of the LinearNonthreshold Dose-Response Model for 

Ionizing Radiation,’’ which reported the 

work of the NCRP’s Scientific 

Committee 1–6. Scientific Committee 1– 

6 was charged with reassessing ‘‘the 

weight of scientific evidence for and 

against the linear-nonthreshold doseresponse model, without reference to 

policy implications.’’ 34 The NCRP 

Report No. 136 explained that the 

existence of the LNT model for low 

radiation doses must be extrapolated 

from data showing adverse health 

effects from high radiation doses and 

that there were differing sets of data that 

both showed evidence for and against 

the LNT model. Nevertheless, the NCRP 

noted ‘‘that radiation imparts its energy 

to living matter through a stochastic 

process, such that a single ionizing track 

has a finite probability of depositing 

enough energy in traversing a cell to 

damage a critical molecular target 

within the cell, such as DNA.’’ 35 After 

a comprehensive review of many 

studies, the NCRP concluded that 

‘‘[a]lthough other dose-response 

relationships for the mutagenic and 

carcinogenic effects of low-level 

radiation cannot be excluded, no 

alternate dose-response relationship 

appears to be more plausible than the 

linear-nonthreshold model on the basis 

of present scientific knowledge.’’ 36

In a May 2017 article published in the 

‘‘International Journal of Radiation 

Biology,’’ the NCRP’s president, Dr. 

John D. Boice, Jr., supports the 

continued use of the LNT model. Dr. 

Boice states that ‘‘[t]he LNT model, at 

least at the current time, has been useful 

in radiation protection, e.g., a safety 

culture exists that encompasses the 

principle of ‘as low as reasonably 

achievable’ (ALARA) considering 

financial and societal issues,’’ and in 

this context, notes that ‘‘worker 

exposures have dropped dramatically 

over the years.’’ 37 Given that 

epidemiological studies may not 

demonstrate the validity of the LNT 

model for low doses (below 100 mSv), 

Dr. Boice further states that the use of 

the LNT model combined with the 

technical and professional judgment of 

a competent regulator provides ‘‘a 

prudent basis for the practical purposes 

of radiological protection.’’ 38 In his 

conclusion, Dr. Boice emphasized that 

the LNT model is not an appropriate 

mechanism to assess radiological risk 

but is the most appropriate model 

currently available for a system of 

radiological protection when coupled 

with the appropriate regulatory and 

technical judgment.39

In a study funded by the NRC, the 

NCRP reevaluated the LNT model based 

on new studies completed since the 

publication of NCRP Report No. 136 in 

June 2001. In April 2018, the NCRP 

released Commentary 27, ‘‘Implications 

of Recent Epidemiologic Studies for the 

Linear-Nonthreshold Model and 

Radiation Protection,’’ which provides a 

detailed assessment of currently 

available epidemiological evidence and 

concludes that ‘‘the LNT model (with 

the steepness of the dose-response slope 

perhaps reduced by a DDREF [dose and 

dose rate effectiveness factor] factor) 

should continue to be utilized for 

radiation protection purposes.’’ 40 The 

Commentary explains that ‘‘[w]hile the 

LNT model is an assumption that likely 

cannot be scientifically validated by 

radiobiologic or epidemiologic evidence 

in the low-dose range, the 

preponderance of epidemiologic data is 

consistent with the LNT assumption, 

although there are a few notable 

exceptions.’’ 41 The Commentary 

concludes that the ‘‘current judgment by 

national and international scientific 

committees is that no alternative doseresponse relationship appears more 

pragmatic or prudent for radiation 

protection purposes than the LNT 

model on the basis of available data, 

recognizing that the risk [for doses] 


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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. 

48Academy 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. 

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. 

52The 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. 

53NCI, 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’’). 

55NCI 2015, at 1. 

56 Id., at 2. 

57NIOSH, 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. 

<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 ‘‘[t]he 

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 

mechanisms have been proposed by 

which this might occur, a recent 

example being the phenomenon of 

genomic instability.’’ 49 The IAEA report 

concluded that ‘‘[f]rom 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 IAEA’s safety standards 

are based. It is not proven—indeed it is 

probably not provable—for 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 NRC’s 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 NRC’s 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 

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 NIOSH’s 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 


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59 K. Leuraud et al., ‘‘Ionising Radiation and Risk 

of Death from Leukaemia and Lymphoma in 

Radiation-monitored Workers (INWORKS): An 

International Cohort Study, Lancet Haematology, 

Vol. 2’’ (June 2015). 

60 Id., at 278. 

61 Id., at 280. 

62NIOSH 2015, at 2. 

63 Id., at 2–3. 

64 Id., at 3. The NRC’s general public and 

occupational dose limits are 1 mSv (0.1 rem) and 

0.05 Sv (5 rem), respectively. See § 20.1201(a)(1) 

(occupational dose limit) and § 20.1301(a)(1) 

(public dose limit). 

65NIOSH 2015, at 3. 

66 Id., at 6. 

67EPA, J. Edwards, ‘‘Comments on Linear NoThreshold Model and Standards for Protection 

Against Radiation’’ (October 7, 2015), at 1. 

68 Id. 

69 Id. 

70 Id., at 2. 

71 Id. 

72The meeting notice for the October 28, 2015, 

meeting was published in the Federal Register on 

September 8, 2015 (80 FR 53896). 

73ACMUI, ‘‘Final Report on the Hormesis/Linear 

No-Threshold Petitions’’ (October 28, 2015), at 1. 

74 Id. 

75 Id., at 1–2. 

76 Id., at 2. 

77 Id., at 1. 

‘‘INWORKS’’ study).59 This study 

included within its cohort over 308,000 

nuclear industry workers from the 

United States, the United Kingdom, and 

France.60 The INWORKS study’s 

authors stated that ‘‘[i]n summary, this 

study provides strong evidence of an 

association between protracted low dose 

radiation exposure and leukemia 

mortality.’’ 61

NIOSH, in its comments, further 

stated that its researchers and others 

conducted meta-analyses of cancer risk from 

low-dose exposures in a variety of 

populations receiving protracted exposure to 

external ionizing radiation [Jacob et al. 2009; 

Daniels and Schubauer-Berigan 2011]. These 

meta-analyses concluded that there is a small 

but significant excess risk of solid cancer and 

leukemia, respectively, at occupational doses 

received during a typical working lifetime 

[Walsh 2011].62

The NIOSH researchers and others 

also published two studies describing 

cancer risk among nuclear workers at 

four Department of Energy sites and the 

Portsmouth Naval Shipyard. According 

to the NIOSH comments, a pooled 

cohort study included nearly 120,000 

nuclear workers from these five sites 

(these workers were also included in the 

larger INWORKS study). The authors of 

the pooled cohort study found that the 

‘‘excess relative risk (ERR) was 

significantly associated with 

occupational radiation dose for all nonsmoking related cancers combined.’’ 63

NIOSH stated that ‘‘[t]hese findings 

suggest that the risk of these cancers 

rises by 0.7% and 2.0% (respectively) 

for every 10 millisieverts (mSv; 1 rem) 

increase in dose.’’ 64 NIOSH, in its 

comments, stated that the LNT model 

presents ‘‘a reasonable framework for 

protecting workers from excess risks 

associated with occupational exposure 

to ionizing radiation’’ 65 and concluded 

with a recommendation that the NRC 

retain the current radiation protection 

standards.66

Similarly, in its comments, EPA 

recommended that the NRC deny the 

petitions. EPA stated the following: 

Within limitations imposed by statistical 

power, the available (and extensive) 

epidemiological data are broadly consistent 

with a linear dose-response for radiation 

cancer risk at moderate and low doses. 

Biophysical calculations and experiments 

demonstrate that a single track of ionizing 

radiation passing through a cell produces 

complex damage sites in DNA, unique to 

radiation, the repair of which is error-prone. 

Thus, no threshold for radiation-induced 

mutations is expected, and, indeed, none has 

been observed.67

EPA, in its comments, referenced four 

epidemiological studies conducted after 

BEIR VII, including the INWORKS 

study, two studies of ‘‘residents along 

the Techa River in Russia who were 

exposed to radionuclides from the 

Mayak Plutonium Production Plant,’’ 

and a study of children who had 

received computed tomography (CT) 

scans.68 The EPA stated that ‘‘[t]hese 

studies have shown increased risks of 

leukemia and other cancers at doses and 

dose rates below those which LNT 

skeptics have maintained are 

harmless—or even beneficial.’’ 69 EPA, 

in its comments, referenced the findings 

of the various domestic and 

international bodies, including the NAS 

and concluded, 

[g]iven the continuing wide consensus on the 

use of LNT for regulatory purposes as well 

as the increasing scientific confirmation of 

the LNT model, it would be unacceptable to 

the EPA to ignore the recommendations of 

the NAS and other authoritative sources on 

this issue.70

EPA concluded that it could not 

endorse basing radiation protection on 

the petitioners’ proposals, which it 

characterized as ‘‘poorly supported and 

highly speculative.’’ 71

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. The ACMUI is a committee 

authorized under the FACA, which 

regulates the formation and operation of 

advisory committees by Federal 

agencies. The ACMUI membership 

includes health care professionals from 

various disciplines, who comment on 

changes to NRC regulations and 

guidance; evaluate certain non-routine 

uses of radioactive material; provide 

technical assistance in licensing, 

inspection, and enforcement cases; and 

bring key issues to the attention of the 

Commission for appropriate action. 

Subsequent to the filing and docketing 

of the petitions, the ACMUI formed a 

subcommittee to review and comment 

on the petitions. The ACMUI held a 

public teleconference meeting on 

October 28, 2015, to vote on the 

subcommittee’s draft report.72 The draft 

subcommittee report was approved by 

the ACMUI and issued as final on that 

same date.73 The ACMUI report stated 

that determining the ‘‘ ‘correct’ doseresponse model for radiation 

carcinogenesis remains an unsettled 

scientific question.’’ 74 Although the 

report acknowledged that there ‘‘is a 

large, and growing, body of scientific 

literature as well as mechanistic 

considerations’’ that question the 

accuracy of the LNT model, the ACMUI 

determined that ‘‘very large-scale 

epidemiological studies with long-term 

follow-up would be needed to actually 

quantify any such risks or benefits’’ and 

that ‘‘such studies may be logistically 

and financially prohibitive.’’ 75

According to the ACMUI report, ‘‘a 

mathematical extrapolation model 

remains the only practical approach to 

estimating the presumed excess cancer 

risk from low-dose radiation.’’ 

Therefore, the ‘‘dose-response data 

derived from epidemiological studies of 

human cohorts, such as the [1945 

Hiroshima and Nagasaki atomic 

bombing] survivors exposed to highdose radiation, are largely consistent 

with an LNT model.’’ 76 In making its 

recommendation, the ACMUI stated that 

it ‘‘recommends that, for the time being 

and subject to reconsideration as 

additional scientific evidence becomes 

available, the NRC continue to base the 

formulation of radiation protection 

standards on the LNT model.’’ 77

Conclusion 

Based upon the current state of 

science, the NRC concludes that the 

actual level of risk associated with low 

doses of radiation remains uncertain 

and some studies, such as the 

INWORKS study, show there is at least 

some risk from low doses of radiation. 

Moreover, the current state of science 

does not provide compelling evidence 

of a threshold, as highlighted by the fact 

that no national or international 

authoritative scientific advisory bodies 

have concluded that such evidence 

exists. Therefore, based upon the stated 


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78Marcus petition (PRM–20–28), at 1–2. 

79 Id., at 7 (‘‘Why deprive the public of the 

benefits of low dose radiation?’’). 

80NAS BEIR VII, at 315. 

81NCRP Report No. 136, at 196; see also NCI 

2015, at 3 (‘‘there is little data to suggest a threshold 

in dose, or possible hormetic (beneficial) effects of 

low-dose radiation exposure’’). 

82 42 U.S.C. 2051(a). 

83 42 U.S.C. 2201(c). 

84 56 FR at 23389. 

85The NRC regulations define ALARA as 

‘‘making every reasonable effort to maintain 

exposures to radiation as far below the dose limits 

in this part as is practical consistent with the 

purpose for which the licensed activity is 

undertaken.’’ § 20.1003. Those individuals and 

entities that hold NRC licenses are required, ‘‘to the 

extent practical,’’ to incorporate ALARA into their 

procedures and engineering controls in accordance 

with § 20.1101(b). The NRC’s Regulatory Guide (RG) 

8.10, ‘‘Operating Philosophy for Maintaining 

Occupational and Public Radiation Exposures As 

Low As Is Reasonably Achievable,’’ Rev. 2 (August 

2016), provides guidance to NRC licensees on 

complying with the ALARA requirement. Other 

NRC regulatory guides provide additional ALARA 

guidance to licensees in specific categories, e.g., RG 

8.8 (power reactor licensees) and RG 8.18 (medical 

licensees). 

86 56 FR at 23389. 

87E.g., Section 182a. of the AEA, with respect to 

reactor applications, requires the Commission to 

Continued 

positions of the aforementioned 

advisory bodies; the comments and 

recommendations of NCI, NIOSH, and 

the EPA; the October 28, 2015, 

recommendation of the ACMUI; and its 

own professional and technical 

judgment, the NRC has determined that 

the LNT model continues to provide a 

sound regulatory basis for minimizing 

the risk of unnecessary radiation 

exposure to both members of the public 

and occupational workers. 

Consequently, the NRC will retain the 

dose limits for occupational workers 

and members of the public in 10 CFR 

part 20 radiation protection regulations. 

Petitioners’ Assertion That Hormesis 

Disproves the LNT Model 

The petitioners advance the concept 

of hormesis, ‘‘in which low levels of 

potentially stressful agents, such as 

toxins, other chemicals, ionizing 

radiation, etc., protect against the 

deleterious effects that high levels of 

these stressors produce and result in 

beneficial effects (e.g., lower cancer 

rates).’’ 78 Thus, the petitioners assert 

that low doses of radiation are beneficial 

to humans in that such doses may 

enhance the immune response or DNA 

repair processes. The petitioners request 

that the NRC amend its regulations to 

raise the dose limit for members of the 

public to be the same as the 

occupational dose limit.79

NRC’s Response 

There is scientific uncertainty and no 

compelling evidence as to whether the 

hormesis concept is valid for 

application to radiation protection 

requirements. None of the national and 

international authoritative scientific 

advisory bodies described above 

support the hormesis concept as a 

regulatory model for radiation 

protection. Of note, the BEIR VII report 

produced by NAS included a strong 

conclusion against applying the 

hormesis concept to radiation 

protection: 

Although examples of apparent stimulatory 

or protective effects can be found in cellular 

and animal biology, the preponderance of 

available experimental information does not 

support the contention that low levels of 

ionizing radiation have a beneficial effect. 

The mechanism of any such possible effect 

remains obscure. At this time, the 

assumption that any stimulatory hormetic 

effects from low doses of ionizing radiation 

will have a significant health benefit to 

humans that exceeds potential detrimental 

effects from radiation exposure at the same 

dose is unwarranted.80

Similarly, the NCRP has found that 

there is not strong support for the 

hormesis concept in the scientific 

literature.81 The NRC has determined 

that it is prudent to continue to rely 

upon the LNT model as a basis for the 

NRC’s radiation protection regulations. 

Consequently, the NRC will retain the 

dose limits for occupational workers 

and members of the public in 10 CFR 

part 20 radiation protection regulations. 

Petitioners’ Assertion That the NRC has 

a Conflict of Interest 

The petitioners suggest a conflict of 

interest, because the NRC is one of the 

Federal agencies that funded the 

development of the BEIR VII report by 

the NAS and has funded, and is 

funding, research by the NCRP. 

NRC’s Response 

Sections 31.a and 161.c of the AEA 

authorize the NRC to enter into 

arrangements with organizations such as 

the NAS and the NCRP. Specifically, 

section 31.a of the AEA authorizes the 

NRC to enter into arrangements, with 

either public or private institutions or 

persons, for research and development 

and to expand theoretical and practical 

knowledge in the various fields 

specified in section 31.a, including 

radiological health and safety.82

Additionally, section 161.c authorizes 

the NRC to ‘‘make such studies and 

investigations, obtain such information 

. . . as the Commission may deem 

necessary or proper to assist it in 

exercising any authority provided in 

[the AEA].’’ 83

The petitioners merely allege a 

conflict of interest. The NRC did not 

influence or direct the findings of either 

the NAS or the NCRP, and the NRC is 

not aware of any irregularities in the 

methods invoked by NAS or NCRP 

technical experts who analyzed the data 

and prepared the respective reports. The 

petitioners did not present any evidence 

to the contrary. Moreover, the 

petitioners did not demonstrate that the 

findings of either the BEIR VII report or 

any of the various NCRP reports that 

were funded in part by the NRC are 

either technically or scientifically 

unsound. The NRC will continue to 

review and consider recommendations 

on radiation protection regulations 

provided by national and international 

authoritative scientific advisory bodies. 

Petitioners’ Assertion That the Cost of 

Compliance With LNT-Based 

Regulations Is Enormous 

The petitioners assert that the cost of 

complying with LNT-based regulations 

is ‘‘enormous’’ and ‘‘incalculable.’’ 

NRC’s Response 

In 1991, the NRC issued the 10 CFR 

part 20 final rule, which established the 

current regulatory framework for the 

NRC’s radiation protection regulations. 

In issuing that final rule, the 

Commission concluded that the rule 

‘‘provides for a substantial increase in 

the overall protection of the public 

health and safety and that the direct and 

indirect costs of its implementation are 

justified in terms of the quantitative and 

qualitative benefits associated with the 

rule.’’ 84 Although the NRC 

acknowledges the costs involved in 

complying with its regulations, the NRC 

continues to conclude that its regulatory 

provisions that rely on LNT, such as the 

ALARA concept, remain both beneficial, 

in terms of the health and safety benefits 

they provide to both members of the 

public and occupational workers, and 

are cost-justified.85 The petitioners have 

not provided any new information that 

would cause the NRC to revisit its 

findings with respect to cost that it 

made in 1991. 

Moreover, in the 1991 final rule, the 

Commission further noted that if it had 

determined that the rule was not costjustified, the Commission would have 

still issued the rule ‘‘because the 

changes made to part 20 also amount to 

a redefinition of the level of adequate 

protection.’’ 86 ‘‘Adequate protection’’ is 

the NRC’s fundamental safety standard 

and is derived from various provisions 

of the AEA.87 An ‘‘adequate protection’’ 


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find that ‘‘the utilization or production of special 

nuclear material will be in accord with the common 

defense and security and will provide adequate 

protection to the health and safety of the public.’’ 

42 U.S.C. 2232(a). 

88Union of Concerned Scientists v. NRC, 824 F.2d 

108, 114 (D.C. Cir. 1987). 

89 80 FR 35870. 

90 80 FR 50804. 

finding means that the Commission or 

the NRC staff, if appropriate, has 

determined that a given requirement is 

the minimum necessary for public 

health and safety. Applicable case law 

holds that ‘‘adequate protection’’ 

findings are made without regard to 

cost. In this regard, the United States 

Court of Appeals, District of Columbia 

Circuit stated that— 

Section 182(a) of the Act commands the 

NRC to ensure that any use or production of 

nuclear materials ‘‘provide[s] adequate 

protection to the health or safety of the 

public.’’ 42 U.S.C. 2232(a). In setting or 

enforcing the standard of ‘‘adequate 

protection’’ that this section requires, the 

Commission may not consider the economic 

costs of safety measures. The Commission 

must determine, regardless of costs, the 

precautionary measures necessary to provide 

adequate protection to the public; the 

Commission then must impose those 

measures, again regardless of costs, on all 

holders of or applicants for operating 

licenses.88

The NRC is mandated under the AEA 

to impose requirements that it 

determines to be necessary for adequate 

protection of public health and safety 

regardless of cost. As set forth earlier in 

this document, the consensus of the 

various international and domestic 

authoritative scientific advisory bodies, 

as well as the NCI, NIOSH, and EPA, is 

that the LNT model should remain the 

basis for radiological protection 

regulations. Based upon these external 

organizations’ recommendations, the 

recommendation of the ACMUI, and the 

professional and technical judgment of 

the NRC, those regulations that are 

based upon the LNT model remain 

necessary for adequate protection. 

Therefore, the NRC will continue to use 

the LNT model as the basis for its 

current radiation protection regulations 

in 10 CFR part 20. 

IV. Public Comments on the Petition 

On June 23, 2015, the NRC published 

in the Federal Register a notice of 

docketing of the three petitions, and 

requested public comment with the 

comment period ending on September 

8, 2015.89 On August 21, 2015, the NRC 

extended the comment period to 

November 19, 2015, to allow more time 

for members of the public to develop 

and submit their comments.90 The NRC 

received over 3,200 comment 

submissions, with 635 of those 

comment submissions being unique, 

including comments from certified 

health physicists, nuclear medical 

professionals, other scientific 

professionals, scientific associations, 

Federal agencies, and concerned 

citizens. 

In determining the appropriate 

response to the petitions, the NRC 

carefully reviewed the public 

comments. To simplify the analysis, the 

NRC grouped all comment letters into 

two main groups: Those that opposed 

the petitions and those that supported 

them. A description of the comments in 

both groups and the NRC’s responses 

are provided as follows. 

Comments Opposed to the Petitions 

Comments: There were 535 unique 

comment submissions that opposed the 

petitioners’ recommendation to 

discontinue use of the LNT model as a 

basis for the NRC’s radiation protection 

regulations. Some of these commenters 

stated that the petitioners did not 

provide sufficient evidence to support 

changing the technical basis regarding 

radiation exposure from the LNT model 

to the hormesis concept. One 

commenter stated that the proposal to 

increase allowable public radiation 

doses to the same as those of nuclear 

industry workers neglects the fact that 

the workers made a voluntary choice to 

work in the nuclear industry, and thus 

be subject to accompanying exposure to 

radiation, whereas the general public 

did not make that choice. Another 

commenter stated that the LNT model is 

satisfactory and that there is no 

substantial science upon which to base 

any change to the current 10 CFR part 

20 public and occupational dose limits. 

One commenter stated that no threshold 

exists because every organism’s 

adaptive response varies considerably, 

with the very young being the most 

vulnerable. Another commenter stated 

that ‘‘the existing standard needs to be 

retained, or at least, retained unless and 

until an undeniable and clear 

preponderance of the evidence indicates 

that the existing standard definitely 

should be replaced by some specific 

alternative.’’ 

Response: The NRC agrees that the 

petitions should be denied. The NRC’s 

rationale is set forth earlier in this 

document. Therefore, the NRC will not 

amend its radiation protection 

regulations in response to the 

petitioners’ requests. 

Comments Supporting the Petitions 

There were 100 unique comment 

submissions that agreed with the 

petitioners. These commenters provided 

varied responses, and so to simplify the 

analysis and address each type of 

comment, the NRC grouped the 

comments by subject and separated 

them into subject areas. A review of the 

comments and the NRC’s responses 

follow. 

Comments Supporting the Petitions— 

General Comments; Assertions That 

NRC Regulations Lead to Unjustified 

Fear of Radiation by Authorities and the 

Public 

Comment: The NRC received several 

comments that expressed support for 

the petitions without providing a 

specific rationale. 

Response: These comments expressed 

support for the petitions in general 

terms and did not provide any further 

rationale or explanation for why the 

petitions should be considered for 

rulemaking. Therefore, no detailed 

response is being provided separate 

from the justification presented above 

for the NRC’s denial of the petitions. 

Comment: The NRC received a 

comment that supports the petitions 

based on the commenter’s experiences 

working in the radiation protection 

field. The commenter concludes that, 

outside of individuals with experience 

in a nuclear facility, most individuals 

do not have proper authority or 

experience to appropriately determine 

proper radiation protection practices. 

Response: The NRC interprets this 

comment to mean that those who lack 

experience working in a nuclear facility 

cannot properly understand radiation 

protection principles. The NRC 

disagrees with this comment. The NRC’s 

radiation protection regulations, 

policies, and guidance are informed by 

operational experience, the findings and 

recommendations of national and 

international authoritative scientific 

advisory bodies, and academic and 

government research. 

Comment: Several commenters 

expressed concern that the LNT model 

and the ALARA concept create an 

unjustified fear of radiation exposure 

that could lead to authorities directing 

mass evacuations in the event of a major 

nuclear incident. The commenters 

expressed concern that such a mass 

evacuation would result in casualties, 

some of which may be caused by mass 

panic, and also result in significant 

socioeconomic costs. 

Response: The NRC disagrees with 

this comment. The appropriate Federal, 

State, and local decision-makers take 

many factors into account when 

deciding to recommend or order an 

evacuation, including the size and 

nature of the incident and the potential 

impacts on affected communities. With 


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91NCRP, ‘‘Ionizing Radiation Exposure of the 

Population of the United States,’’ Report No. 160 

(2009), at 5. 92 Id., at 85 (alteration added). 93Fred A. Mettler, MD, Professor Emeritus and 

Clinical Professor, Department of Radiology, Mew 

Mexico School of Medicine, presentation entitled 

‘‘Dose, Benefit, Risk and Safety’’ at the 2018 Annual 

Meeting of the NCRP (March 5, 2018). Dr. Mettler’s 

presentation is expected to be published in the 

Health Physics Journal in 2019. 94 Id., at 117 (the number of procedures in 

radiographic fluoroscopy increased by 54% 

between 2002 and 2005) and at 195 (5% annual 

growth in the number of nuclear-medicine 

procedures between 1995 and 2005). 

95Marcus petition (PRM–20–28), at 7. 

96 Id. 

97 Id., at 4. 

98Miller petition (PRM–20–29), at 6–7. 

99 80 FR, at 35872. 

respect to evacuation decisions, the 

State and local authorities who make 

those decisions are not subject to the 

AEA or to the NRC’s ALARA 

requirement. 

Moreover, ALARA is an operating 

principle designed to minimize the 

potential stochastic effects of low levels 

of ionizing radiation that members of 

the public and occupational workers 

may be exposed to as a result of routine 

licensee activities. The long-term 

potential (in terms of years or even 

decades) for the induction of cancer 

from these routine activities is the 

primary stochastic effect that the 

application of ALARA seeks to 

minimize. In an emergency situation 

involving the release of radioactive 

material, the overriding concern 

associated with evacuation decisions is 

to avert potential acute radiation 

exposure. 

The NRC has concluded that the 

selection of a specific dose response 

model, LNT in this case, and the 

ALARA concept, which is premised 

upon the LNT model, do not lead 

directly to an unjustified fear of 

radiation, and thereby do not directly 

contribute to evacuation casualties and 

associated socioeconomic costs after a 

nuclear incident. The NRC’s rationale 

for continuing to use the LNT model as 

the basis for its radiation protection 

regulations is set forth earlier in this 

document. The costs of mass evacuation 

scenarios described by the commenters 

do not provide an adequate basis to 

discontinue the use of the LNT model. 

Comment: One commenter asserted 

that ‘‘there may be cases where, in 

efforts to minimize even low radiation 

exposure to workers and the public in 

the design, operation, and accident 

management of nuclear facilities, we 

may actually increase the probability of 

much larger exposures from severe 

accidents.’’ 

Response: The NRC disagrees with 

this comment. The operating experience 

of nuclear facilities has not shown any 

relationship between severe accident 

risk and radiation protection practices. 

Comment: Several commenters 

expressed concern that the public’s fear 

of radiation exposure due to the NRC’s 

continued use of the LNT model could 

result in patients postponing or 

foregoing CT scans and other diagnostic 

radiology procedures, thereby resulting 

in adverse medical consequences to the 

patient. Other commenters asserted that 

the use of LNT in the medical field can 

inhibit lifesaving processes that require 

a higher radiation dose than what is 

currently acceptable or can add to the 

cost of certain procedures, also 

inhibiting patients from receiving 

important treatment. 

Response: The NRC disagrees with 

this comment. Moreover, the NRC’s 

regulations do not apply to the 

decisions of a physician to prescribe a 

certain diagnostic or therapeutic 

modality to treat a patient. The 

physician’s recommendation and the 

patient’s decision to undergo a CT scan 

are wholly informed by the professional 

judgement of the medical provider and 

are therefore outside the scope of the 

NRC’s regulatory authority. The NRC 

does not regulate machine-generated 

radiation, which is the type generated 

by the use of x-ray machines and CT 

devices. Machine-generated radiation is 

regulated by the states, and as such, any 

application of the LNT model to the 

NRC’s radiation protection requirements 

would not affect these medical uses. 

Moreover, current evidence 

demonstrates that the use of radiation 

producing devices in medical diagnostic 

tests and therapies in the United States 

is increasing—all while LNT has been in 

place as the underlying dose-response 

assumption for radiation protection. For 

example, the NCRP reported that the 

average medical exposure in 2006 had 

increased substantially from the early 

1980s, primarily due to the increased 

use of CT, interventional fluoroscopy, 

and nuclear medicine.91 With respect to 

CT, the NCRP stated that 

‘‘[t]echnological advances in CT and the 

ease of use of this technology have led 

to many clinical applications that have 

increased the use of CT at a rate of 8 to 

15% per year for the last 7 to 10 years 

[prior to 2006].’’ 92 CT scanning further 

increased from 2006 to 2012.93 The use 

of interventional fluoroscopy and 

nuclear medicine have also similarly 

increased.94 The commenters’ claims 

that patients are postponing or foregoing 

radiology procedures is not supported. 

These commenters did not present 

evidence to support the assertion that 

the NRC’s use of the LNT model results 

in adverse medical treatment 

consequences. 

Comment: One commenter stated that 

the summary of the petitioners’ position 

as described in the NRC’s June 23, 2015, 

notice of docketing (80 FR 35870), 

characterized the petitions inaccurately, 

by stating that the petitioners wanted 

the NRC to amend the basis for radiation 

protection under 10 CFR part 20 from 

the LNT model to the hormesis model. 

The commenter expressed concerns that 

readers would be negatively biased 

against the petitions due to this 

representation of the petitioners’ 

position. 

Response: The NRC disagrees with 

this comment. In her petition, Dr. 

Marcus requested that the NRC amend 

its radiation protection regulations in 10 

CFR part 20 to ‘‘take radiation hormesis 

into account.’’ 95 Dr. Marcus then made 

several specific recommendations, 

including the complete removal of 

ALARA from the NRC’s radiation 

protection regulations; the end of 

‘‘differential doses to pregnant women; 

embryos and fetuses, and children 

under 18 years of age’’; and an increase 

in radiation dose limits to members of 

the public so that the public dose limit 

would be equal to the dose limits for 

occupational workers. In her petition, 

Dr. Marcus states that the removal of 

ALARA is ‘‘not only harmless but may 

be hormetic,’’ and in requesting that 

‘‘[p]ublic doses should be raised to 

worker doses,’’ asked ‘‘[w]hy deprive 

the public of the benefits of low dose 

radiation?’’ 96 In addition, Dr. Marcus 

referenced studies which she argued 

suggest that low doses of radiation 

decrease cancer rates and asserted 

‘‘[h]ormesis is a perfectly good 

alternative explanation’’ for such 

results.97 Similarly, in his petition, Mr. 

Miller recommends that ‘‘[p]ublic dose 

limits should be raised to match worker 

dose limits, as these low doses may be 

hormetic,’’ and that ‘‘[l]ow-dose limits 

for the public perpetuates 

radiophobia.’’ 98 Moreover, in its June 

23, 2015, Federal Register notice of 

docketing, the NRC stated that the 

petitions were publicly-available and 

should be consulted for additional 

information.99 Thus, the NRC concludes 

that it accurately summarized the 

petitions in its June 23, 2015, Federal 

Register notice of docketing. 

Comment: One commenter stated that 

a public education system should be put 

in place to dispel fear of low-level 

radiation. 

Response: The NRC considers this 

comment to be outside the scope of the 

issues raised by the petitions, because 


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100NAS BEIR VII, at 6. 

101NCRP Report No. 116, at 60. 

102 ICRP, ‘‘1990 Recommendation of the 

International Commission on Radiological 

Protection,’’ Pub. No. 60 (1991), at 22; NCRP Report 

No. 116, at 29. 

103 ICRP Pub. No. 60, at 111. 104UNSCEAR, ‘‘Non-stochastic effects of 

irradiation,’’ Report to the General Assembly, 

ANNEX J (1982) at 575. 

105 ICRP Pub. No. 103, at 53; ICRP Pub. No. 60, 

at 18; NCRP Report No. 116, at 29. Although the 

NRC has not formally adopted a DDREF in 

regulation, it has relied upon a DDREF in computer 

modeling. E.g., NUREG–2161, ‘‘Consequence Study 

of a Beyond-Design-Basis Earthquake Affecting the 

Spent Fuel Pool for a U.S. Mark I Boiling Water 

Reactor,’’ (September 2014) at 195 (incorporating 

DDREF into computer modeling for offsite 

consequences of a postulated spent fuel pool 

accident). 

106 ICRP Pub. No. 60, at 19; NCRP Report No. 116, 

at 60. 

107 ICRP Pub. No. 60, at 22; NCRP Report No. 116, 

at 29. 

108For example, a DDREF value of ‘‘1’’ (no dose 

and dose rate effect) is used for certain tissues such 

as the thyroid and a higher value (e.g., a ‘‘2’’ or a 

‘‘3’’) is used for other, less radio-sensitive tissues. 

the establishment of a public education 

system to dispel fears of low-level 

radiation is not a mission or 

responsibility of the NRC and is beyond 

the NRC’s statutory authority. The NRC 

supports communication efforts to 

accurately convey the radiological risks 

associated with any given regulated 

activity. The NRC, through its 

communication efforts, engages 

stakeholders in order to foster 

transparency and communication 

between the NRC and the public (e.g., 

through public meetings, public 

comment on NRC rulemakings and 

guidance development, the NRC’s 

public website, and the NRC’s use of 

social media). 

Comment: The NRC received several 

comments requesting that the NRC 

conduct research on topics raised by the 

petition. 

Response: The NRC disagrees with 

these comments. The comments 

requesting that the NRC engage in 

additional research is outside the scope 

of the subject petitions. Other Federal 

agencies are charged with conducting 

basic radiation research, such as the 

Department of Energy and the National 

Institutes of Health. 

Comments Supporting the Petitions— 

Assertions That the LNT Model Lacks 

an Adequate Scientific Basis 

Comment: Several commenters 

questioned the scientific basis of the 

LNT model and asserted that it should 

no longer be the premise of the NRC’s 

radiological protection regulations. 

Response: The NRC disagrees with 

these comments. The NRC’s goal as a 

regulatory agency is to protect both the 

public and occupational workers from 

the radiological hazards associated with 

NRC-licensed material, activities, and 

facilities. The NRC uses the LNT model 

to establish radiation protection 

measures that quantify radiation 

exposure and set regulatory limits. The 

premise of the LNT model is that the 

long-term biological damage caused by 

ionizing radiation (i.e., risk of cancer 

induction or adverse hereditary effects) 

is directly proportional to the dose 

received by the human receptor. The 

LNT model provides for a conservative, 

comprehensive radiation protection 

scheme that protects individuals in all 

population categories (male, female, 

adult, child, and infant) and exposure 

ranges by reducing the risk from lowdose radiation exposure. 

As described earlier in this document, 

the consensus among various domestic 

and international authoritative scientific 

advisory bodies and the three Federal 

agencies that submitted comments (NCI, 

NIOSH, and EPA) is that the LNT model 

should remain the basis for the NRC’s 

radiological protection regulations. 

Similarly, the ACMUI recommends that 

the NRC continue to use the LNT model. 

Based upon the external organizations’ 

recommendations, the ACMUI’s 

recommendation, and its own 

professional and technical judgment, 

the NRC has determined that the LNT 

model continues to provide a sound 

basis for minimizing the risk of 

unnecessary radiation exposure to both 

members of the public and occupational 

workers. 

Comment: One commenter noted that 

multiplying the LNT-based risk 

coefficient by a population dose to 

derive a hypothetical number of cancer 

deaths in no way shows, proves, or 

demonstrates that anyone is getting 

cancer. 

Response: The NRC disagrees with 

this comment. The petitions for 

rulemaking request that the NRC amend 

10 CFR part 20 to discontinue use of the 

LNT model as the primary scientific 

basis for the agency’s radiation 

protection standards. The NRC does not 

use the LNT model for deterministic 

mortality projections. 

Comment: One commenter noted that 

the LNT model is flawed, because it 

lacks timescale modeling to account for 

the differences between getting a large 

dose over a long period of time as 

opposed to a large dose in a short period 

of time. 

Response: The NRC disagrees with 

this comment. The LNT model, as 

applied by the NRC in its licensing and 

regulatory decisions, effectively 

addresses the potential health impacts 

of any given dose received either 

acutely or chronically. 

Human epidemiologic studies have 

established that there is an increased 

incidence of certain cancers associated 

with radiation exposure at high doses 

and high dose rates (acute exposure). 

The principal source of information for 

risk estimation is the Japanese survivors 

of the atomic bombing of Hiroshima and 

Nagasaki in 1945, who were exposed to 

a range of doses at a high dose rate.100

The NCRP defines high dose rate as a 

dose rate above which recovery and 

repair processes are unable to 

ameliorate the radiation damage.101

Both the ICRP and NCRP estimate that 

the risk of death from radiation-induced 

cancer resulting from an acute exposure 

is 10 × 10–2 per Sv for a population of 

all ages.102 However, experimental 

results in animals and other biological 

systems suggest that cancer induction 

from acute exposures at low doses and 

involving low dose rates should be less 

than that observed after high doses 

involving high dose rates.103

If the radiation dose is received 

chronically (i.e., over a long period of 

time), the biologic response differs 

because much of the radiation damage 

is effectively and efficiently repaired.104

To account for this difference in 

response to chronic low dose and low 

dose rate radiation exposure as 

compared to high dose and high dose 

rate radiation exposure, the ICRP and 

NCRP recommend, and the NRC has 

adopted, adjusting the risk of death from 

radiation exposure using a DDREF of 

two.105 The DDREF is assumed to apply 

whenever the absorbed dose is less than 

200 mSv (20 rem) and the dose rate is 

less than 100 mSv (10 rad) per hour.106

Consequently, the risk coefficient for 

members of the public pertaining to low 

dose and low dose rate radiation 

exposure is 5 × 10–2 per Sv. This risk 

coefficient is further reduced to 4 × 10–2

per Sv for occupational workers because 

this population excludes both the very 

young and elderly who may be slightly 

more sensitive to radiation-induced 

carcinogenesis.107 The risks of radiation 

exposure to occupational workers are 

described further in Regulatory Guide 

(RG) 8.29, ‘‘Instruction Concerning 

Risks from Occupational Radiation 

Exposure,’’ Revision 1 (1996). 

Although the appropriate value of the 

DDREF may depend on the specific low 

or very low dose scenario,108 the use of 

a DDREF, particularly one with a high 

value, does not mean that there are no 

harmful health effects from low and 

very low doses of radiation. The use of 

a DDREF also does not demonstrate the 

presence of a threshold below which no 

permanent harmful effects will occur. 

The NRC staff concludes that the use of 


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109NCI 2015, at 3. 

110 Id. (alteration added). 

111 Id. 

112 Id. 

113 Id., at 1. 

114 Id. 

115NAS BEIR VII, at 228. 

116UNSCEAR, ‘‘Sources, Effects and Risks of 

Ionizing Radiation, Annex B: Epidemiological 

studies of cancer risk due to low-dose-rate radiation 

from environmental sources,’’ Report to the General 

Assembly with Scientific Annexes (2017) 

(UNSCEAR 2017 Report, Ann. B). 

117UNSCEAR 2017 Report, Ann. B, at 153. 

118 Id., at 155. 

a DDREF in its dose calculations aligns 

with the LNT model. 

Comment: Several commenters 

observed that mammals evolved in an 

environment with a constant low dose 

of radiation. One commenter noted that 

humans developed DNA repair 

mechanisms to compensate. This 

commenter further stated that we 

experience far more DNA double strand 

breaks during mitotic cell division than 

we do from exposure to background 

radiation. As the biological mechanisms 

deployed to repair DNA damage caused 

by mitotic cell division are well 

documented, the commenter concludes 

that the rate of DNA damage that we can 

accommodate is also documented. This 

commenter reasons that because the rate 

of damage is substantially greater than 

zero, the LNT model cannot be correct. 

Response: The NRC disagrees with 

this comment. There is substantial 

scientific uncertainty regarding the 

ability of the human body’s immune 

system, or other forms of adaptive 

response, to repair cells damaged by 

ionizing radiation. According to the NCI 

comments, the available data does not 

show that any immune or other adaptive 

response offsets the carcinogenic 

damage caused by a given dose of 

ionizing radiation.109 NCI, in its 

comments, states that the ‘‘repair of 

[DNA] double strand breaks (DSBs) 

relies on a number of pathways,’’ and 

that these pathways are ‘‘prone to 

errors,’’ which may result in cell 

mutations, a fraction of which may lead 

to cancer.110 NCI further notes that the 

petitioners, and by extension, the 

commenter, do not reference data which 

shows that various cohorts subjected to 

‘‘protracted radiation exposures’’ 

develop ‘‘an increase in stable 

chromosome aberrations and other 

markers of biological damage in the 

peripheral blood lymphocytes.’’ 111 NCI 

states that such chromosome aberrations 

may increase the risk of cancer, and 

concluded that ‘‘there is little data to 

suggest a threshold in dose, or possible 

hormetic (beneficial) effects of low-dose 

radiation exposure.’’ 112

Comments Supporting the Petitions— 

Assertions That There Are No 

Observable Adverse Effects From 

Background Radiation 

Comment: Several commenters 

remarked that background levels of 

ionizing radiation, which vary 

significantly around the world, have 

never been demonstrated to be a health 

hazard to humans. Some commenters 

also noted that in regions of the world 

such as Brazil or India where 

background radiation levels are higher 

than normal, epidemiological studies of 

large cohorts of subjects living in these 

areas did not reveal excess cancers or 

diseases linked to radiation exposure. 

On this basis, these commenters 

conclude that the LNT model is based 

on a premise that is not supported by 

evidence. 

Response: The NRC disagrees with 

these comments. The NRC notes that, in 

general, the inability to observe an effect 

does not mean that the effect has not 

occurred. These high background 

exposure studies are epidemiological in 

nature. They cannot be used as 

quantitative estimates of disease risk 

associated with the radiation exposure 

levels found in the areas studied, 

because the studies lack sufficient 

quantifiable evidence of the absence of 

cancer risk. As explained by NCI there 

are limitations associated with reliance 

on epidemiological studies in any effort 

to invalidate the LNT model. NCI noted 

that ‘‘[c]ancer risks predicted by the 

LNT model are likely to be small at low 

doses; so small as to be difficult to 

detect in the presence of large numbers 

of cancers resulting from other 

causes.’’ 113 In this regard, NCI further 

stated that ‘‘because epidemiologic 

studies are observational in nature and 

not controlled experiments, differences 

in risks in exposed and unexposed 

[populations] may reflect differences in 

life style factors such as smoking and 

may not necessarily result from 

radiation exposure.’’ 114

In addition, the BEIR VII report 

prepared by NAS indicates that studies 

of populations exposed to natural 

background radiation are limited in 

their ability to define risk of disease in 

relation to radiation dose. In discussing 

four studies of populations exposed to 

natural background radiation, the BEIR 

VII Phase 2 report states: 

These studies did not find higher disease 

rates in geographic areas with high 

background levels of radiation exposure 

compared to areas with lower background 

levels. However, these studies were ecologic 

in design and utilized population-based 

measures of exposure rather than individual 

estimates of radiation dose. Thus, they 

cannot provide any quantitative estimates of 

disease risk associated with the exposure 

levels found in the areas studied.115

Also, the United Nations Scientific 

Committee on the Effects of Atomic 

Radiation (UNSCEAR) has recently 

published a review of cancer risk due to 

low dose rate radiation from 

environmental sources.116 UNSCEAR 

concluded that ‘‘the results of the 

studies of cancer risk due to radiation 

exposure at low dose rates from 

environmental radiation do not provide 

strong evidence for materially lower 

risks per unit exposure than in studies 

of high radiation doses and dose 

rates.’’ 117 In this regard, UNSCEAR 

noted that methodological 

improvements in environmental studies 

are needed to overcome ‘‘low statistical 

power, dosimetric uncertainties, 

imperfections in control of confounding, 

and any other biases’’ to include 

‘‘under-ascertainment of cases (deaths 

or diagnoses), inaccurate cancer 

diagnosis, imprecise dose assessment, 

and residual confounding.’’ 118

Therefore, no direct inferences about 

radiation effects can be drawn from 

studies where background radiation 

levels are higher than normal. 

Comments Supporting the Petitions— 

Objections to ALARA 

Comment: One commenter asserted 

that current regulations are too 

restrictive and focus too heavily on 

radiation protection, thus creating a 

system that emphasizes compliance 

with ALARA at the expense of ‘‘basic 

lab safety,’’ such as somebody falling 

and hitting their head. The commenter 

posits that such accidents are far more 

likely than receiving a ‘‘fatal radiation 

dose.’’ 

Response: The NRC disagrees with 

this comment. The NRC interprets the 

commenter’s use of the phrase ‘‘basic 

lab safety’’ as meaning compliance with 

non-radiologic safety requirements. 

Non-radiologic safety issues are the 

oversight responsibility of the 

Occupational Safety and Health 

Administration (OSHA) and appropriate 

State and local government agencies. 

Licensees are required and expected to 

comply with both applicable NRC 

requirements as well as those of OSHA 

and the pertinent State and local 

authorities. Moreover, licensees 

demonstrate compliance with ALARA 

by such actions as establishing 

appropriate procedures and engineering 

controls, providing the proper training 


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119 10 CFR 20.1003 and 10 CFR 20.1101(b). 

120RG 8.8, Rev. 3, at 2. 

121RG 8.10, Rev. 2, at 5. 

122 10 CFR 20.1003. 

123 Id. 

124 10 CFR 20.1101(b). 

125 56 FR at 23366. 

126 10 CFR 20.1003 (‘‘the economics of 

improvements in relation to the state of 

technology,’’ ‘‘the economics of improvements in 

relation to benefits to the public health and safety,’’ 

and ‘‘other societal and socioeconomic 

considerations’’). 

127RG 8.8, Rev. 3, at 2. 

128 Id. 129RG 8.10, Rev. 2, at 5; see also RG 8.8, Rev. 3. 

and equipment, restricting access to 

radiation areas, and ensuring 

appropriate facility design. Therefore, 

ALARA practices should complement 

and work in concert with ‘‘basic lab 

safety,’’ rather than degrade it. 

The ALARA definition and the 

associated regulatory requirement also 

involve the concept of reasonableness, 

meaning that the licensee should make 

‘‘every reasonable effort’’ to implement 

ALARA measures and should use 

procedures and engineering controls 

based upon sound radiation protection 

principles to achieve ALARA, to the 

‘‘extent practical.’’ 119 In addition, NRC 

guidance indicates that non-radiological 

hazards should be considered in 

determining appropriate ALARA 

measures. For example, RG 8.8, 

‘‘Information Relevant to Ensuring That 

Occupational Radiation Exposures at 

Nuclear Power Stations Will Be as Low 

as Is Reasonable Achievable,’’ states that 

‘‘a comprehensive consideration of risks 

and benefits will include risks from 

nonradiological hazards. An action 

taken to reduce radiation risks should 

not result in a significantly larger risk 

from other hazards.’’ 120 Similarly, RG 

8.10, ‘‘Operating Philosophy for 

Maintaining Occupational and Public 

Radiation Exposures as Low as Is 

Reasonably Achievable,’’ states that ‘‘the 

decision to implement measures to 

reduce occupational radiation doses 

should be weighed against the risk of 

any other occupational hazards in the 

workplace, to minimize the total risk to 

the worker’s health and safety.’’ 121

Finally, the commenter did not 

provide any support for the assertion 

that a licensee’s compliance with 

ALARA or other NRC requirements 

based upon the LNT model undermines 

or otherwise impedes a licensee’s ability 

to comply with non-radiologic safety 

requirements. 

Comments: Several commenters 

objected to the use of the ALARA 

concept as a regulatory requirement by 

the NRC. Many of these commenters 

asserted that the implementation of 

ALARA results in excessive costs to 

licensees and as such, inhibits potential 

growth and innovation. Some 

commenters also asserted that ALARA 

does not strike the appropriate balance 

between safety and economy. Virtually 

all of these commenters requested the 

removal of the ALARA requirement in 

order to reduce costs. 

Response: The NRC disagrees with 

these comments. The NRC regulations 

define ALARA as ‘‘making every 

reasonable effort to maintain exposures 

to radiation as far below the dose limits 

in this part as is practical consistent 

with the purpose for which the licensed 

activity is undertaken.’’ 122 ALARA 

takes into account the following, in 

relation to the utilization of nuclear 

energy and licensed materials in the 

public interest: (1) The state of 

technology, (2) the economics of 

improvements in relation to the state of 

technology, (3) the economics of 

improvements in relation to benefits to 

the public health and safety, and (4) 

other societal and socioeconomic 

considerations.123 The NRC requires 

that its licensees ‘‘use, to the extent 

practical, procedures and engineering 

controls based upon sound radiation 

protection principles to achieve 

occupational doses and doses to 

members of the public that are 

[ALARA].’’ 124 Furthermore, the NRC’s 

1991 rule stated that ‘‘the ALARA 

concept is intended to be an operating 

principle rather than an absolute 

minimization of exposures.’’ 125

The regulatory language of the 

ALARA definition sets out the 

considerations in making ALARA 

determinations, several of which 

include the consideration of economic 

factors.126 The NRC guidance states that 

‘‘ ‘[r]easonably achievable’ is judged by 

considering the state of technology and 

the economics of improvements in 

relation to all the benefits from these 

improvements.’’ 127 In general, the NRC 

determines compliance with the 

ALARA requirement based on whether 

the licensee has incorporated measures 

to track and, if necessary, to reduce 

exposures; not whether exposures and 

doses represent an absolute minimum or 

whether the licensee has used all 

possible methods to reduce exposures. 

Furthermore, the level of effort 

expended on radiation protection 

programs, including compliance with 

the ALARA concept, should reflect the 

magnitude of the potential exposures— 

both the magnitude of average and 

maximum individual doses and, in 

facilities with large numbers of 

employees, collective (population) 

doses.128 Thus, the size of a licensee’s 

radiation protection program should be 

commensurate with the scope and 

extent of the licensed activities. For 

example, a large organization, such as a 

nuclear power reactor licensee, would 

be expected to have a considerably 

larger and more extensive radiation 

protection program than a smaller 

organization that may maintain lower 

activity sealed sources. 

In addition, ALARA is achieved by 

implementing such fundamental 

measures as effective planning, training 

of the appropriate personnel, provision 

of appropriate equipment (e.g., 

dosimeters), controlling access to 

radiation areas, installation of radiation 

monitoring systems, and preparing 

appropriate facility designs.129 The 

regulated community has had decades 

of operational experience in 

implementing ALARA measures, and it 

is likely that most costs of ALARA 

compliance have long since been 

optimized. Moreover, the NRC considers 

many of these measures to be simply the 

implementation of sound operating 

practices. Finally, other than their 

general assertions, the commenters have 

not provided any substantive evidence 

demonstrating that the ALARA concept 

or the LNT model inhibits innovation or 

growth. The NRC has determined that 

current ALARA requirements are 

consistent with the LNT model of 

radiation protection and reasonably 

account for economic considerations. 

Comments Supporting the Petitions— 

Assertion That the NRC Relies on the 

LNT Model as a Result of Political 

Pressure or Bias 

Comment: Several commenters stated 

that the LNT model continues to remain 

relevant as a regulatory framework only 

because of political pressure or 

ideological or scientific bias. 

Response: The NRC disagrees with 

this comment. The NRC is an 

independent regulatory agency that 

establishes its radiation protection 

regulations based, in part, on the 

recommendations of domestic and 

international authoritative scientific 

advisory bodies such as the ICRP, the 

NAS, and the NCRP. As described 

previously in this document, three other 

Federal agencies and the ACMUI 

recommend that the LNT model remain 

the basis for the NRC’s radiation 

protection regulations. The commenters 

have not provided any substantive 

support for their assertion that political 

pressure or bias is motivating the NRC 

to continue to rely upon the LNT model. 

The NRC continues to conclude that, in 

the absence of convincing evidence that 

there is a dose threshold or that low 


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Federal Register / Vol. 86, No. 156 / Tuesday, August 17, 2021 / Proposed Rules 45935 

levels of radiation are beneficial, the 

LNT model remains a prudent and 

conservative basis for the NRC’s 

radiation protection regulations. 

V. Availability of Documents 

The following table provides 

information about materials referenced 

in this notification. The ADDRESSES

section of this notification provides 

additional information about how to 

access ADAMS. 

Date Document ADAMS accession No. or Federal 

Register citation 

Submitted Petitions 

February 9, 2015 ............................. Petition for Rulemaking (PRM–20–28) .................................................. ML15051A503. 

February 13, 2015 ........................... Petition for Rulemaking (PRM–20–29) .................................................. ML15057A349. 

February 24, 2015 ........................... Petition for Rulemaking (PRM–20–30) .................................................. ML15075A200. 

Federal Register Notifications 

June 23, 2015 ................................. 10 CFR part 20—Linear no-Threshold Model and Standards for Protection Against Radiation—Notice of Docketing and Request for 

Comment (PRM–20–28, PRM–20–29, and PRM–20–30).

80 FR 35870. 

August 21, 2015 .............................. 10 CFR part 20—Linear no-Threshold Model and Standards for Protection Against Radiation—Notice of Docketing and Request for 

Comment; Extension of Comment Period (PRM–20–28, PRM–20– 

29, and PRM–20–30).

80 FR 50804. 

September 8, 2015 ......................... Advisory Committee on the Medical Uses of Isotopes: Meeting Notice 80 FR 53896. 

May 21, 1991 .................................. 10 CFR part 20, ‘‘Radiation Protection,’’ Advance Notice of Proposed 

Rulemaking; Request for Comments.

56 FR 23360. 

January 27, 1987 ............................ Federal Radiation Protection Guidance for Occupational Exposure .... 52 FR 2822. 

Federal Regulations 

1991 ................................................ 10 CFR part 20, ‘‘Standards for Protection Against Radiation’’ ............ N/A. 

2006 ................................................ NAS BEIR VII, ‘‘Health Risks from Exposure to Low Levels of Ionizing Radiation’’.N/A. 

1946 ................................................ U.S. Code: Title 42, Chapter 23, ‘‘Development and Control of Atomic 

Energy’’.

N/A. 

National and International Publications 

2005 ................................................ ICRP Publication 99, ‘‘Low-dose Extrapolation of Radiation-related 

Cancer Risk’’.

N/A. 

1977 ................................................ ICRP Publication 26, ‘‘Recommendations of the International Commission on Radiological Protection’’.N/A. 

1993 ................................................ NCRP Report No. 116, ‘‘Limitation of Exposure to Ionizing Radiation’’ N/A. 

2001 ................................................ NCRP Report No. 136, ‘‘Evaluation of the Linear-Nonthreshold DoseResponse Model for Ionizing Radiation’’.N/A. 

2005 ................................................ Academy of Sciences and National Academy of Medicine (France), 

‘‘Dose-Effect Relationships and Estimation of the Carcinogenic Effects of Low Doses of Ionizing Radiation’’.

N/A. 

August 1998 .................................... IAEA, ‘‘Measures to Strengthen International Co-Operation in Nuclear, Radiation and Waste Safety, Nuclear Safety Review for the 

Year 1997’’.

N/A. 

2014 ................................................ IAEA, ‘‘Radiation Protection and Safety of Radiation Sources: International Basic Safety Standards, General Safety Requirements 

Part 3’’.

N/A. 

April 24, 2018 .................................. NCRP Commentary 27, ‘‘Implications of Recent Epidemiologic Studies for the Linear Nonthreshold Model and Radiation Protection’’.N/A. 

2009 ................................................ NCRP Report No. 160, ‘‘Ionizing Radiation Exposure of the Population of the United States’’.N/A. 

1991 ................................................ ICRP Publication 60, ‘‘1990 Recommendations of the International 

Commission on Radiological Protection’’.

N/A. 

2007 ................................................ ICRP Publication No. 103, ‘‘The 2007 Recommendations of the International Commission on Radiological Protection’’.N/A. 

Other Reference Documents 

July 1993 ......................................... Health Physics Society, Position Statement PS008–2, ‘‘Uncertainty in 

Risk Assessment,’’ (Revised April 1995, February 2013).

N/A. 

2017 ................................................ Dr. John D. Boice, Jr., ‘‘The linear nonthreshold (LNT) model as used 

in radiation protection: An NCRP update,’’ International ournal of 

Radiation Biology, Vol. 93, No. 10.

N/A. 

June 2015 ....................................... K. Leuraud et al., ‘‘Ionising Radiation and Risk of Death from 

Leukaemia and Lymphoma in Radiation-monitored Workers 

(INWORKS): An International Cohort Study, Lancet Haematology, 

Vol. 2’’.

N/A. 

October 28, 2015 ............................ ACMUI, ‘‘Final Report on the Hormesis/Linear No-Threshold Petitions’’.ML15310A418. 


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45936 Federal Register / Vol. 86, No. 156 / Tuesday, August 17, 2021 / Proposed Rules 

Date Document ADAMS accession No. or Federal 

Register citation 

August 2016 .................................... RG 8.10, ‘‘Operating Philosophy for Maintaining Occupational and 

Public Radiation Exposures As Low As Is Reasonably Achievable,’’ 

Rev. 2.

ML16105A136. 

June 1978 ....................................... RG 8.8, ‘‘Information Relevant to Ensuring that Occupational Radiation Exposures at Nuclear Power Stations Will Be as Low as Is 

Reasonably Achievable,’’ Rev. 3.

ML003739549. 

September 2014 .............................. NUREG–2161, ‘‘Consequence Study of a Beyond-Design-Basis 

Earthquake Affecting the Spent Fuel Pool for a U.S. Mark I Boiling 

Water Reactor’’.

ML14255A365. 

2017 ................................................ UNSCEAR, ‘‘Sources, Effects and Risks of Ionizing Radiation, Annex 

B: Epidemiological studies of cancer risk due to low-dose-rate radiation from environmental sources’’.

N/A. 

1996 ................................................ RG 8.29, ‘‘Instruction Concerning Risks from Occupational Radiation 

Exposure’’ Rev. 1.

ML003739438. 

VI. Conclusion 

The NRC reviewed the petitioners’ 

requests, as well as public comments 

received on the petitions. For the 

reasons cited in this document, the NRC 

is denying the three PRMs, specifically 

PRM–20–28, PRM–20–29, and PRM–20– 

30, in their entirety. Given the current 

state of scientific knowledge, the NRC 

has determined that the LNT model 

continues to be an appropriate basis for 

its radiation protection regulatory 

framework. Thus, the NRC’s current 

radiation protection regulations provide 

for the adequate protection of human 

health and safety, and as such, changes 

to 10 CFR part 20 are not warranted at 

this time. 

Dated: August 11, 2021. 

For the Nuclear Regulatory Commission. 

Annette L. Vietti-Cook, 

Secretary of the Commission. 

[FR Doc. 2021–17475 Filed 8–16–21; 8:45 am] 

BILLING CODE 7590–01–P 

DEPARTMENT OF HOMELAND 

SECURITY 

Coast Guard 

33 CFR Part 110 

[Docket Number USCG–2020–0216] 

RIN 1625–AA01 

Anchorage Grounds; Cape Fear River 

Approach, North Carolina 

AGENCY: Coast Guard, Department of 

Homeland Security (DHS). 

ACTION: Notice of proposed rulemaking. 

SUMMARY: The Coast Guard is proposing 

to amend the anchorage regulations for 

Lockwoods Folly Inlet, NC, and adjacent 

waters, by establishing a new offshore 

anchorage and relocating and amending 

the existing explosives anchorage. The 

purpose of this proposed rule is to 

improve navigation and public safety by 

accommodating recent and anticipated 

future growth in cargo vessel traffic and 

vessel size that call on Military Ocean 

Terminal Sunny Point and the Port of 

Wilmington, NC. We invite your 

comments on this proposed rulemaking. 

DATES: Comments and related material 

must be received by the Coast Guard on 

or before October 18, 2021. 

ADDRESSES: You may submit comments 

identified by docket number USCG– 

2020–0216 using the Federal 

eRulemaking Portal at https://

www.regulations.gov. See the ‘‘Public 

Participation and Request for 

Comments’’ portion of the 

SUPPLEMENTARY INFORMATION section for 

further instructions on submitting 

comments. 

FOR FURTHER INFORMATION CONTACT: If 

you have questions about this proposed 

rulemaking, call or email Marine 

Science Technician Chief (MSTC) 

Joshua O’Rourke, Sector North Carolina, 

U.S. Coast Guard; telephone (910) 772– 

2227, email Joshua.P.Orourke@uscg.mil; 

or Mr. Jerry Barnes, Waterways 

Management Branch, Fifth Coast Guard 

District, U.S. Coast Guard; telephone 

(757) 398–6230, email Jerry.R.Barnes@

uscg.mil. 

SUPPLEMENTARY INFORMATION: 

I. Table of Abbreviations 

BOEM Bureau of Ocean Energy 

Management 

CFR Code of Federal Regulations 

DHS Department of Homeland Security 

FR Federal Register 

NM Nautical Miles 

U.S.C. United States Code 

II. Background, Purpose, and Legal 

Basis 

On May 8, 2020, the Coast Guard 

published a notice of inquiry in the 

Federal Register (85 FR 27343) to solicit 

public comments on whether we should 

initiate a rulemaking to establish an 

anchorage ground offshore in the 

approaches to the Cape Fear River, NC, 

and to increase the size and relocate the 

existing Lockwoods Folly Inlet 

explosives anchorage. We received two 

comment letters in response, both 

endorsing a rulemaking to amend the 

anchorage regulations as described. The 

Coast Guard is now moving forward 

with this proposed rulemaking. 

The Cape Fear River supports a 

diverse marine transportation system 

which includes Military Ocean 

Terminal Sunny Point, North Carolina 

State Port of Wilmington, and several oil 

terminals and bulk-handling facilities 

for cement, asphalt products, molasses, 

liquid chemicals, sulfur, fertilizers and 

liquid sugar. Military Ocean Terminal 

Sunny Point is a Department of Defense 

facility that stores and ships 

ammunition, dangerous cargo and 

explosives for United States forces 

worldwide. A federal navigation project 

provides for a channel 44 feet deep from 

the ocean to a point just south of 

Southport, NC, and 42 feet to the Lower 

Anchorage Basin and Turning Basin at 

Wilmington, NC. In support of 

continued port growth and growth in 

both size and volume of vessel traffic, 

the U.S. Army Corps of Engineers is 

considering the need for major channel 

depth, width, and alignment changes. 

These include deepening the existing 

federal navigation channel to the Port of 

Wilmington, extending the ocean 

entrance channel farther offshore, and 

widening channels in the Cape Fear 

River where needed. 

At the same time, the demand for 

offshore wind energy is increasing. 

Plummeting costs, technological 

advancements, increasing demand and 

great economic potential have combined 

to make offshore wind a promising 

avenue for adding to a diversified 

national energy portfolio. In 2018, the 

Bureau of Ocean Energy Management 

(BOEM) developed and sought feedback 

on a Proposed Path Forward for Future 


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