[Federal Register Volume 86, Number 156 (Tuesday, August 17, 2021)]
[Proposed Rules]
[Pages 45923-45936]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2021-17475]


 ========================================================================
 Proposed Rules
                                                 Federal Register
 ________________________________________________________________________
 
 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.
 
 ========================================================================
 

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

[[Page 45923]]



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: [email protected]. 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 publicly-available 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 [email protected]. 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 [email protected] 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: 
[email protected]; 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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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:
---------------------------------------------------------------------------

    \3\ \.\The terms ``occupational worker,'' ``radiation worker,'' 
``nuclear worker,'' and ``worker'' are used interchangeably in this 
document.
---------------------------------------------------------------------------

     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.

[[Page 45924]]

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 Sec.  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\
---------------------------------------------------------------------------

    \4\ 10 CFR 20.1101(a).
---------------------------------------------------------------------------

    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--
---------------------------------------------------------------------------

    \5\ The 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.
    \6\ The 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.
    \8\ For 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.
---------------------------------------------------------------------------

     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 radiation-related health 
detriment or a radiation-related 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\
---------------------------------------------------------------------------

    \9\ ICRP, ``Low-dose extrapolation of radiation-related cancer 
risk,'' Pub. No. 99 (2005), at 38.
---------------------------------------------------------------------------

    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:
---------------------------------------------------------------------------

    \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. Sec.  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). Sec.  
20.1201(a)(1)(i).

    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\
---------------------------------------------------------------------------

    \11\ Id.

    The other two assumptions supporting the NRC's radiation

[[Page 45925]]

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.
---------------------------------------------------------------------------

    \12\ The 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.'' Sec.  
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.
---------------------------------------------------------------------------

    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:
---------------------------------------------------------------------------

    \15\ Id.
    \16\ Id.

    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\
---------------------------------------------------------------------------

    \17\ Id., at 23360-61.

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \21\ Position Statement of the Health Physics Society (HPS), 
PS008-2, ``Uncertainty in Risk Assessment,'' Adopted July 1993, 
Revised April 1995, February 2013.
    \22\ HPS PS-008-2 at 2.
    \23\ Id.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \24\ The 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/.
    \25\ The 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/.
    \26\ E.g., 56 FR at 23360.
---------------------------------------------------------------------------

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

[[Page 45926]]

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.
---------------------------------------------------------------------------

    \27\ NAS, ``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-of-ionizing-radiation. The 
NRC was one of several Federal agencies that provided funding to NAS 
for the BEIR VII study.
    \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.
---------------------------------------------------------------------------

    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, no-
threshold dose-response relationship between exposure to ionizing 
radiation and the development of cancer in humans.'' \32\
---------------------------------------------------------------------------

    \30\ NAS BEIR VII at 10.
    \31\ Id.
    \32\ Id., at 323.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \33\ NCRP, ``Limitation of Exposure to Ionizing Radiation,'' 
Report No. 116 (1993), at 10 (emphasis in the original).

    In 2001, the NCRP published Report No. 136, ``Evaluation of the 
Linear-Nonthreshold 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 dose-response 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\
---------------------------------------------------------------------------

    \34\ NCRP, ``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 dose-response relationships in the lower dose range with the 
coefficient being quite similar to the alpha coefficient of the in 
vitro linear-quadratic dose-response curves.'').
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

    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 dose-
response 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]

[[Page 45927]]

<100 mGy [<10 rad] is uncertain but small.'' \42\
---------------------------------------------------------------------------

    \40\ NCRP, ``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.
    \42\ Id.
---------------------------------------------------------------------------

International Authoritative Scientific Advisory Bodies Favoring 
Continued Use of LNT
    The ICRP, in its Publication No. 99, ``Low-dose Extrapolation of 
Radiation-related 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 low-dose 
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\
---------------------------------------------------------------------------

    \43\ ICRP, ``Low-dose Extrapolation of Radiation-related Cancer 
Risk,'' Pub. No. 99 (2005), at 108.
    \44\ Id.
    \45\ Id., at 113.
    \46\ ICRP, ``The 2007 Recommendations of the International 
Commission on Radiological Protection,'' Pub. No. 103 (2007), at 36 
and 38, 65-67.
    \47\ Id., at A178 and A180.
    \48\ Academy of Sciences and National Academy of Medicine 
(France), ``Dose-Effect Relationships and Estimation of the 
Carcinogenic Effects of Low Doses of Ionizing Radiation'' (2005), at 
5.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \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.
---------------------------------------------------------------------------

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.
---------------------------------------------------------------------------

    \52\ The ACMUI is an official advisory body to the NRC 
established in accordance with the Federal Advisory Committee Act 
(FACA), 5 U.S.C. App. 2. The ACMUI advises the NRC on policy and 
technical issues that arise in the regulation of the medical uses of 
radioactive material in diagnosis and therapy.
---------------------------------------------------------------------------

    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:
---------------------------------------------------------------------------

    \53\ NCI, A. Berrington de Gonz[aacute]lez, et al., 
``Contribution to Nuclear Regulatory Commission (NRC) comments on 
petitions on linear no-threshold 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'').

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 dose-response 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\
---------------------------------------------------------------------------

    \55\ NCI 2015, at 1.

    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.
---------------------------------------------------------------------------

    \56\ Id., at 2.
---------------------------------------------------------------------------

    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

[[Page 45928]]

``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\
---------------------------------------------------------------------------

    \57\ NIOSH, S. Toye, ``Comments of the National Institute for 
Occupational Safety and Health on the Nuclear Regulatory Commission 
Notice of Docketing and Request for Comment on Linear No-Threshold 
Model and Standards for Protection Against Radiation,'' September 
11, 2015 (NIOSH 2015).
    \58\ Id., at 2.
    \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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \62\ NIOSH 2015, at 2.

    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 non-smoking 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\
---------------------------------------------------------------------------

    \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 
Sec.  20.1201(a)(1) (occupational dose limit) and Sec.  
20.1301(a)(1) (public dose limit).
    \65\ NIOSH 2015, at 3.
    \66\ Id., at 6.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \67\ EPA, J. Edwards, ``Comments on Linear No-Threshold Model 
and Standards for Protection Against Radiation'' (October 7, 2015), 
at 1.

    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,
---------------------------------------------------------------------------

    \68\ Id.
    \69\ Id.

[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\
---------------------------------------------------------------------------

    \70\ Id., at 2.

    EPA concluded that it could not endorse basing radiation protection 
on the petitioners' proposals, which it characterized as ``poorly 
supported and highly speculative.'' \71\
---------------------------------------------------------------------------

    \71\ Id.
---------------------------------------------------------------------------

    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' dose-response 
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 high-dose 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\
---------------------------------------------------------------------------

    \72\ The meeting notice for the October 28, 2015, meeting was 
published in the Federal Register on September 8, 2015 (80 FR 
53896).
    \73\ ACMUI, ``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.
---------------------------------------------------------------------------

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

[[Page 45929]]

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\
---------------------------------------------------------------------------

    \78\ Marcus petition (PRM-20-28), at 1-2.
    \79\ Id., at 7 (``Why deprive the public of the benefits of low 
dose radiation?'').
---------------------------------------------------------------------------

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\
---------------------------------------------------------------------------

    \80\ NAS BEIR VII, at 315.

    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.
---------------------------------------------------------------------------

    \81\ NCRP 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'').
---------------------------------------------------------------------------

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\
---------------------------------------------------------------------------

    \82\ 42 U.S.C. 2051(a).
    \83\ 42 U.S.C. 2201(c).
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \84\ 56 FR at 23389.
    \85\ 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.'' Sec.  
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 Sec.  
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).
---------------------------------------------------------------------------

    Moreover, in the 1991 final rule, the Commission further noted that 
if it had determined that the rule was not cost-justified, 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''

[[Page 45930]]

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--
---------------------------------------------------------------------------

    \86\ 56 FR at 23389.
    \87\ E.g., Section 182a. of the AEA, with respect to reactor 
applications, requires the Commission to 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).

    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\
---------------------------------------------------------------------------

    \88\ Union of Concerned Scientists v. NRC, 824 F.2d 108, 114 
(D.C. Cir. 1987).

    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.
---------------------------------------------------------------------------

    \89\ 80 FR 35870.
    \90\ 80 FR 50804.
---------------------------------------------------------------------------

    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

[[Page 45931]]

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.
---------------------------------------------------------------------------

    \91\ NCRP, ``Ionizing Radiation Exposure of the Population of 
the United States,'' Report No. 160 (2009), at 5.
    \92\ Id., at 85 (alteration added).
    \93\ Fred 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).
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \95\ Marcus petition (PRM-20-28), at 7.
    \96\ Id.
    \97\ Id., at 4.
    \98\ Miller petition (PRM-20-29), at 6-7.
    \99\ 80 FR, at 35872.
---------------------------------------------------------------------------

    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

[[Page 45932]]

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 low-dose 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 x 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\
---------------------------------------------------------------------------

    \100\ NAS BEIR VII, at 6.
    \101\ NCRP 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.
---------------------------------------------------------------------------

    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 x 10-2 per Sv. This risk coefficient 
is further reduced to 4 x 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).
---------------------------------------------------------------------------

    \104\ UNSCEAR, ``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.
---------------------------------------------------------------------------

    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

[[Page 45933]]

a DDREF in its dose calculations aligns with the LNT model.
---------------------------------------------------------------------------

    \108\ For 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.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \109\ NCI 2015, at 3.
    \110\ Id. (alteration added).
    \111\ Id.
    \112\ Id.
---------------------------------------------------------------------------

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\
---------------------------------------------------------------------------

    \113\ Id., at 1.
    \114\ Id.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \115\ NAS BEIR VII, at 228.


    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\
---------------------------------------------------------------------------

    \116\ UNSCEAR, ``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).
    \117\ UNSCEAR 2017 Report, Ann. B, at 153.
    \118\ Id., at 155.
---------------------------------------------------------------------------

    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

[[Page 45934]]

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\
---------------------------------------------------------------------------

    \119\ 10 CFR 20.1003 and 10 CFR 20.1101(b).
    \120\ RG 8.8, Rev. 3, at 2.
    \121\ RG 8.10, Rev. 2, at 5.
---------------------------------------------------------------------------

    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\
---------------------------------------------------------------------------

    \122\ 10 CFR 20.1003.
    \123\ Id.
    \124\ 10 CFR 20.1101(b).
    \125\ 56 FR at 23366.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \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'').
    \127\ RG 8.8, Rev. 3, at 2.
    \128\ Id.
---------------------------------------------------------------------------

    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.
---------------------------------------------------------------------------

    \129\ RG 8.10, Rev. 2, at 5; see also RG 8.8, Rev. 3.
---------------------------------------------------------------------------

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

[[Page 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.

------------------------------------------------------------------------
                                                         ADAMS accession
                                                         No. or Federal
             Date                      Document             Register
                                                            citation
------------------------------------------------------------------------
                           Submitted Petitions
------------------------------------------------------------------------
February 9, 2015..............  Petition for            ML15051A503.
                                 Rulemaking (PRM-20-
                                 28).
February 13, 2015.............  Petition for            ML15057A349.
                                 Rulemaking (PRM-20-
                                 29).
February 24, 2015.............  Petition for            ML15075A200.
                                 Rulemaking (PRM-20-
                                 30).
------------------------------------------------------------------------
                     Federal Register Notifications
------------------------------------------------------------------------
June 23, 2015.................  10 CFR part 20--Linear  80 FR 35870.
                                 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).
August 21, 2015...............  10 CFR part 20--Linear  80 FR 50804.
                                 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).
September 8, 2015.............  Advisory Committee on   80 FR 53896.
                                 the Medical Uses of
                                 Isotopes: Meeting
                                 Notice.
May 21, 1991..................  10 CFR part 20,         56 FR 23360.
                                 ``Radiation
                                 Protection,'' Advance
                                 Notice of Proposed
                                 Rulemaking; Request
                                 for Comments.
January 27, 1987..............  Federal Radiation       52 FR 2822.
                                 Protection Guidance
                                 for Occupational
                                 Exposure.
------------------------------------------------------------------------
                           Federal Regulations
------------------------------------------------------------------------
1991..........................  10 CFR part 20,         N/A.
                                 ``Standards for
                                 Protection Against
                                 Radiation''.
2006..........................  NAS BEIR VII, ``Health  N/A.
                                 Risks from Exposure
                                 to Low Levels of
                                 Ionizing Radiation''.
1946..........................  U.S. Code: Title 42,    N/A.
                                 Chapter 23,
                                 ``Development and
                                 Control of Atomic
                                 Energy''.
------------------------------------------------------------------------
                 National and International Publications
------------------------------------------------------------------------
2005..........................  ICRP Publication 99,    N/A.
                                 ``Low-dose
                                 Extrapolation of
                                 Radiation-related
                                 Cancer Risk''.
1977..........................  ICRP Publication 26,    N/A.
                                 ``Recommendations of
                                 the International
                                 Commission on
                                 Radiological
                                 Protection''.
1993..........................  NCRP Report No. 116,    N/A.
                                 ``Limitation of
                                 Exposure to Ionizing
                                 Radiation''.
2001..........................  NCRP Report No. 136,    N/A.
                                 ``Evaluation of the
                                 Linear-Nonthreshold
                                 Dose-Response Model
                                 for Ionizing
                                 Radiation''.
2005..........................  Academy of Sciences     N/A.
                                 and National Academy
                                 of Medicine (France),
                                 ``Dose-Effect
                                 Relationships and
                                 Estimation of the
                                 Carcinogenic Effects
                                 of Low Doses of
                                 Ionizing Radiation''.
August 1998...................  IAEA, ``Measures to     N/A.
                                 Strengthen
                                 International Co-
                                 Operation in Nuclear,
                                 Radiation and Waste
                                 Safety, Nuclear
                                 Safety Review for the
                                 Year 1997''.
2014..........................  IAEA, ``Radiation       N/A.
                                 Protection and Safety
                                 of Radiation Sources:
                                 International Basic
                                 Safety Standards,
                                 General Safety
                                 Requirements Part 3''.
April 24, 2018................  NCRP Commentary 27,     N/A.
                                 ``Implications of
                                 Recent Epidemiologic
                                 Studies for the
                                 Linear Nonthreshold
                                 Model and Radiation
                                 Protection''.
2009..........................  NCRP Report No. 160,    N/A.
                                 ``Ionizing Radiation
                                 Exposure of the
                                 Population of the
                                 United States''.
1991..........................  ICRP Publication 60,    N/A.
                                 ``1990
                                 Recommendations of
                                 the International
                                 Commission on
                                 Radiological
                                 Protection''.
2007..........................  ICRP Publication No.    N/A.
                                 103, ``The 2007
                                 Recommendations of
                                 the International
                                 Commission on
                                 Radiological
                                 Protection''.
------------------------------------------------------------------------
                        Other Reference Documents
------------------------------------------------------------------------
July 1993.....................  Health Physics          N/A.
                                 Society, Position
                                 Statement PS008-2,
                                 ``Uncertainty in Risk
                                 Assessment,''
                                 (Revised April 1995,
                                 February 2013).
2017..........................  Dr. John D. Boice,      N/A.
                                 Jr., ``The linear
                                 nonthreshold (LNT)
                                 model as used in
                                 radiation protection:
                                 An NCRP update,''
                                 International ournal
                                 of Radiation Biology,
                                 Vol. 93, No. 10.
June 2015.....................  K. Leuraud et al.,      N/A.
                                 ``Ionising Radiation
                                 and Risk of Death
                                 from Leukaemia and
                                 Lymphoma in Radiation-
                                 monitored Workers
                                 (INWORKS): An
                                 International Cohort
                                 Study, Lancet
                                 Haematology, Vol. 2''.
October 28, 2015..............  ACMUI, ``Final Report   ML15310A418.
                                 on the Hormesis/
                                 Linear No-Threshold
                                 Petitions''.

[[Page 45936]]

 
August 2016...................  RG 8.10, ``Operating    ML16105A136.
                                 Philosophy for
                                 Maintaining
                                 Occupational and
                                 Public Radiation
                                 Exposures As Low As
                                 Is Reasonably
                                 Achievable,'' Rev. 2.
June 1978.....................  RG 8.8, ``Information   ML003739549.
                                 Relevant to Ensuring
                                 that Occupational
                                 Radiation Exposures
                                 at Nuclear Power
                                 Stations Will Be as
                                 Low as Is Reasonably
                                 Achievable,'' Rev. 3.
September 2014................  NUREG-2161,             ML14255A365.
                                 ``Consequence Study
                                 of a Beyond-Design-
                                 Basis Earthquake
                                 Affecting the Spent
                                 Fuel Pool for a U.S.
                                 Mark I Boiling Water
                                 Reactor''.
2017..........................  UNSCEAR, ``Sources,     N/A.
                                 Effects and Risks of
                                 Ionizing Radiation,
                                 Annex B:
                                 Epidemiological
                                 studies of cancer
                                 risk due to low-dose-
                                 rate radiation from
                                 environmental
                                 sources''.
1996..........................  RG 8.29, ``Instruction  ML003739438.
                                 Concerning Risks from
                                 Occupational
                                 Radiation Exposure''
                                 Rev. 1.
------------------------------------------------------------------------

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