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1
Introduction
The presence of naturally occurring radionuclides in soil, rock, water,
and air along with cosmic radiation results in continuous and largely
unavoidable radiation exposures of all humans. Exposures larger than these due
to undisturbed natural background can result from human activities that move
naturally occurring radionuclides from normally inaccessible locations to
locations where humans are present or concentrate naturally occurring
radionuclides. Examples of human activities that can increase exposures to
naturally occurring radionuclides by relocation or concentration are mining and
milling of mineral ores, extraction of petroleum products, use of groundwater
for domestic purposes, and living in houses. The present US inventory of waste
materials generated by these activities is in excess of 60 billion metric tons
(EPA 1993b).
DEFINITION AND SCOPE OF STUDY
This study by the National Research Council's Committee on the
Evaluation of EPA Guidelines for Exposures to Naturally Occurring
Radioactive Materials (NORM) was initiated in response to a congressional
directive that included the following:
The Administrator of the Environmental Protection Agency
(EPA) shall enter into an arrangement with the National Academy of
Sciences to investigate and report on He scientific bases for Me public
recommendations of EPA with respect to indoor radon and other
naturally occurring radioactive materials (NORM). The National
Academy shall examine EPA's guidelines in light of the
recommendations of the National Council on Radiation Protection and
16
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INTRODUCTION
Measurements, and other peer-reviewed research by the National
Cancer Institute, the Centers for Disease Control, and others, on radon
and NORM. The National Academy shall summarize the principal
areas of agreement and disagreement among the above, and shall
evaluate the scientific and technical basis for any differences that exist.
17
Exposures to naturally occurring radionuclides resulting from human
activities that alter the natural environment can, to some degree, be subjected to
regulatory control. The general concern of this study is the regulation of
exposures to technologically enhanced naturally occurring radioactive materials
by the US Environmental Protection Agency (EPA) and other regulatory and
advisory organizations. The issues are complex and have been the focus of
attention of radiation-protection authorities at the state and federal levels for
over 2 decades (for example, CRCPD 1997; Bliss 1978; CRCPD 1978~.
Pursuant to the congressional mandate, the National Research Council's
committee was charged with undertaking a study to compare EPA guidelines for
controlling exposures of the public to technologically enhanced NORM with
other regulatory and advisory organizations' guidelines. The concern expressed
by Congress is that different organizations had arrived at different numerical
values for guidelines that apply to essentially the same exposure situations and
that the reasons for the differences, especially their scientific and technical
bases, were not apparent.
Specifically, the committee was asked to address the following
questions:
· Whether the differences among EPA and other guidelines for
technologically enhanced NORM are based on scientific and
technical information or on policy decisions related to risk
management.
· If there are differences in the scientific and technical bases of the
guidelines developed by EPA and other organizations, what the
relative merit of the different bases is.
· Whether there is appropriate scientific information that has not
been used in the development of contemporary risk analysis for
NORM.
in regard to the third question, the committee was asked to evaluate whether
there might be important differences in approaches to risk assessment between
NORM and human-made radionuclides.
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18
GUIDELINES FOR EXPOSURE TO TENORM
On the basis of the congressional mandate and the charge to the
committee, the committee defined the scope of the study as follows:
· This study is concerned with guidelines for controlling
exposures of the public to NORM, but it is not concerned with
guidelines for NORM in occupational settings or with guidelines for
human-made radionuclides in the workplace or the environment.
· This study is not concerned with issues of exposure during, risks
posed by, or guidelines for transportation of NORM.
· This study is concerned with the extent to which the assumptions
about radiation risks used by EPA in developing its guidelines for
NORM differ from the assumptions used by other organizations in
developing similar guidelines and with the relative merits of
assumptions about radiation-related risks. The study is not concerned
with other issues of risk assessment for NORM that may arise in
attempting to estimate real risks posed by actual exposures of
individuals or populations.
· This study does not include an independent evaluation of current
information on radiation-related risks from epidemiologic studies.
That kind of evaluation is the responsibility of such other
authoritative organizations as the National Research Council's
Committee on the Biological Effects of Ionizing Radiations (BEIR),
the Unfed Nations Scientific Committee on the Effects of Atomic
Radiation (UNSCEAR), the National Council on Radiation
Protection and Measurements (NCRP), and the International
Commission on Radiological Protection (ICRP). In particular, the
extensive information on the health risks from exposure to the
important naturally occurring materials radium, thorium, uranium,
and radon, based on human and animal studies, has been reviewed
and evaluated, for example, by the BEIR IV Committee (National
Research Council 1988) and by Stannard (1988), but is not evaluated
in this study.
· This study is not concerned with issues of site-specif~c risk
assessments for NORM. But some issues that are important to site-
specific assessments are also important in the development of
guidelines for NORM, such as the dependence of exposure pathways
on the physical and chemical forms of radionuclides, and these issues
are considered in this study.
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INTRODUCTION
· This study is not concerned with evaluations of nonscientific
issues that are important in the development of guidelines for
NORM, including costs and policy judgments in risk management.
But in evaluating whether differences among EPA and other
guidelines for NORM are based on scientific and technical
information, the committee found it necessary to consider policy
judgments in risk management that have influenced the development
of guidelines, even though the merit of any judgments is not
evaluated in this study.
· This study is not concerned with exposures of, risks to, or
guidelines for biota other than humans.
THE RAI)IOACTIVE MATERIALS OF CONCERN
19
The committee has used the term technologically enhanced naturally
occurring radioactive materials (TENORM) to refer to the materials of concern
in this study. The committee defines this term as follows:
Technologically enhanced naturally occurring radioactive
materials are any naturally occurring radioactive materials not
subject to regulation under the Atomic Energy Act whose
radionuclide concentrations or potential for human exposure
have been increased above levels encountered in the natural
state by human activities.
The exclusion of NORM that are regulated under the Atomic Energy
Act from the definition of TENORM is important. This study is not concerned
with evaluating guidelines developed by EPA or other organizations that apply
to NORM associated with the production and use of nuclear fuels such as
uranium and thorium mill tailings, any naturally occurring radionuclides
released to the environment during operations of nuclear fuel-cycle facilities, or
natural uranium or thorium in the form of source material. However, the
committee has considered EPA guidelines for NORM arising from the nuclear
fuel cycle because these guidelines have provided important precedents in
establishing guidelines for similar non-fuel-cycle radioactive materials of
concern to this study.
The distinction between NORM associated with the nuclear fuel cycle,
which are not of concern in this study, and TENORM as defined above is rooted
in the definitions of source, special nuclear, and byproduct materials as used in
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20
GUIDELINES FOR EXPOSURE TO TENORM
the Atomic Energy Act (see appendix A) and the authority given to the US
Atomic Energy Commission (and, later, the US Nuclear Regulatory
Commission) to regulate radioactive materials defined in the act but not any
other radioactive materials. Before the establishment of EPA in 1970 and the
promulgation of environmental laws concerned primarily with hazardous
materials other than radionuclides, there was no legal authority for federal
regulation of TENORM, and the regulation of radioactive materials from the
nuclear fuel cycle has proceeded largely independently of the regulation of
TENORM, with considerably greater attention given to fuel-cycle materials.
Thus, the concern about guidelines for TENORM that led to this study
arises from the definitions of radioactive materials in the Atomic Energy Act
and the much greater attention that has been given to the regulation of
radioactive materials from the nuclear fuel cycle. However, the distinction
between naturally occurring radionuclides associated with the nuclear fuel cycle
and naturally occurring radionuclides associated with other activities is artificial
with regard to protection of human health and the environment in that the risks
posed by a given radiation exposure do not depend on the source of the
radioactive material.
APPROACH TO THE STUDY
In evaluating guidelines for TENORM developed by EPA and other
organizations in response to the charge described above, the committee has
considered guidelines for indoor radon separately from guidelines for any other
TENORM. The distinction between radon and any other radionuclides in the
context of developing guidelines for radiation exposure was incorporated in the
earliest standards for limiting internal exposures of workers (Advisory
Committee on X-ray and Radium Protection 1941), and has been maintained
ever since in developing guidelines for workers and the public.
There are two important scientific and technical reasons for the
distinction between radon and other radionuclides. First, radon is an inert gas; it
is the only naturally occurring radionuclide in this form. Its emanation from
radium-bearing soil, rock, and building materials results in substantial exposures
in indoor environments, and it is unique among the radionuclides with regard to
the importance of this exposure pathway. Indeed, indoor radon is the most
important source of radiation exposure of the public.
Second, and more important, the relationship between exposure to
short-lived decay products of radon in air and the risk of lung cancer can be
estimated, with some uncertainty, from epidemiologic studies in various groups
of miners. Thus, the risk posed by exposure to indoor radon can be estimated
without the need to develop models for estimating doses to radiosensitive tissues
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INTRODUCTION
21
of the lung from irradiation by alpha particles after inhalation and without the
need to invoke assumptions about the risk per unit dose of alpha particles.
Radon is unique among the radionuclides in this regard; for no other
radionuclides can estimates of cancer risk posed by internal exposure be
obtained without estimating the dose per unit intake and the risk per unit dose.
Estimates of risk associated with external exposure to any radionuclide also
must be based on estimates of dose and risk per unit dose.
Evaluation of Guidelines for Indoor Radon
The approach in this study to evaluating guidelines for indoor radon
developed by EPA and other organizations is relatively straightforward because
tibe guidelines for this exposure situation are well defined. The main task of the
committee was to evaluate whether the differences among the various guidelines
have a scientific and technical basis.
Evaluation of Guidelines for TENORM Other Than Indoor Radon
The committee's task in evaluating guidelines for TENORM other than
indoor radon was more difficult than the task in evaluating guidelines for indoor
radon, in part because of the variety of exposure situations of concern, including
releases from controlled sources, waste management and disposal, and
remediation of environmental contamination. In addition, for the following
reasons, it was not a simple matter for the committee to define the current EPA
guidelines for these materials.
First, some guidelines are outdated and seem not to represent EPA's
current views on suitable approaches to regulating TENORM. In some cases,
proposals for revising guidelines have been published in the Federal Register to
provide opportunity for public comment, but revised guidelines have not been
issued in final form. Thus, it was not clear at the time of this study whether the
existing but outdated guidelines would be replaced or, if so, what the new
guidelines would be. An important example is EPA's proposed federal guidance
on radiation protection of the public, which would replace guidance developed
by the Federal Radiation Council (FRC) nearly 40 years ago. The proposed
revision of the federal guidance contains a dose limit for all controlled sources
of exposure combined (including human-made radionuclides and TENORM
other than indoor radon) that is one-fifth the dose limit in the FRC guidance.
The question of which guidance represents EPA's current views on radiation
protection of the public is obviously important in comparing EPA guidelines for
TENORM with guidelines developed by other organizations.
Second, some EPA guidelines for specific exposure situations
involving TENORM are in the form of legally enforceable regulations that were
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22
GUIDELINES FOR EXPOSURE TO TENORM
published in the Federal Register and took public comment into account, but
EPA's preferred approach to regulating TENORM in other situations is indicated
only by policy statements that have not been subjected to public comment.
Important examples are EPA's strategy for protecting groundwater resources and
various EPA directives on the interpretation of requirements for remediation of
contaminated sites under the Comprehensive Environmental Response,
Compensation, and Liability Act (CERCLA). The committee was faced with
decisions about the weight to be given EPA guidelines in the form of policy
statements relative to those in the form of legally enforceable regulations.
Third, for some important exposure situations, such as management
and disposal of waste that contains TENORM except waste arising from
treatment of drinking water, EPA has not published any guidelines, and the
committee had to infer EPA's preferred approach to regulation on the basis of
existing or proposed guidelines for similar exposure situations.
Fourth, no EPA regulation or set of regulations applies to all potentially
important sources of exposure to TENORM other than indoor radon.
For all those reasons, the committee had to use judgment in selecting
EPA guidelines for TENORM other than indoor radon to be given the greatest
emphasis in comparisons with guidelines developed by other organizations. In
general, the committee has emphasized more recent guidelines without regard
for other considerations, such as whether they have been issued in proposed or
final form and whether they are legally binding regulations or only policy
statements. However, in an effort to provide a reasonably complete picture of
EPA's current policies, the committee has attempted to discuss all EPA
guidelines of any kind that are relevant to the regulation of TENORM.
Other Considerations
The committee has interpreted its charge to review and evaluate
guidelines for TENORM quite broadly. It has endeavored to go beyond simple
recitations of facts and figures for the guidelines of concern. There are many
and diverse guidelines, especially for TENORM other than indoor radon, and
many of them seem inconsistent with regard to the acceptable health risks for
the public. The committee believes it important to describe the bases for the
various guidelines, how they should be interpreted, and how they fit within an
overall framework for radiation protection of the public that embodies only a
few basic principles. Guidelines are important individually, but it also is
important to understand how they are related and how they are consistent with
one another.
In protection of public health, there have been different uses among
various federal agencies and other organizations of such terms as acceptable and
unacceptable to describe different levels of risk, and some organizations also
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INTRODUCTION
23
have used tolerable and intolerable. In discussing any particular guideline for
TENORM, the committee has endeavored to use such terms as they were used
by the organization whose guideline is under consideration. However, because
the terms, especially acceptable and unacceptable, sometimes have been used in
ways that do not conform to the public's general understanding of their meaning
and import, the committee has commented on their possible misinterpretations
in discussing particular guidelines.
Although the purpose of any guideline is to limit health risks,
guidelines themselves usually are expressed in terms of exposure or dose, rather
than directly in terms of risk. The earliest radiation standards often were
expressed in terms of limits on dose to the whole body or He critical organ,
which usually is the organ that receives the highest dose. Later standards have
been expressed in terms of the effective dose equivalent or effective dose, as
defined by the ICRP. Those quantities are weighted sums of doses to several
organs and tissues that are intended to be proportional to risk posed by any
uniform or nonuniform irradiation of the whole body, the latter often occurring
as a result of intakes of radionuclides by ingestion or inhalation. An
understanding of the various concepts and terms for radioactivity and radiation
dose is important for understanding risk, and a glossary of radiation quantities
and units is given in the appendix.
STRUCTURE OF THE REPORT
as follows.
The remaining chapters in this report are organized into three groups,
Chapters 2-6 provide background information that is important for
understanding and evaluating the various guidelines for TENORM: information
on characteristics of naturally occulting radionuclides and natural background
radiation, important sources of TENORM, the role of exposure pathway and
dose or risk assessments in providing a technical basis for radiation standards,
the basic judgments involved in developing radiation standards for any exposure
situation, and the responsibilities of the regulatory and advisory organizations
whose guidelines for TENORM have been considered in this study.
Chapters 7-9 present detailed information on the guidelines for
TENORM considered in this study. Chapter 7 reviews the existing or proposed
guidelines developed by EPA. It also discusses health risks to the public
corresponding to the different guidelines, the issue of consistency of guidelines
with regard to limits on risk, the relationship between the guidelines and risks
experienced in actual exposure situations, and the importance of the objective
that exposures be as low as reasonably achievable (ALARA) in determining
actual risks. Chapter 8 reviews the existing guidelines for indoor radon
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GUIDELINES FOR EXPOSURE TO TENORM
developed by EPA and other organizations and information on radon-related
risks assumed by the various organizations. Chapter9 reviews the existing
guidelines for TENORM other than indoor radon developed by organizations
other than EPA. It also discusses the issue of transferability from one exposure
situation to another of guidelines in the form of limits on concentrations of
radionuclides in environmental media.
Chapters 10-12 focus on the charge to the committee on the basis of
information presented in the preceding chapters. Chapter 10 presents summaries
and comparisons of the various guidelines for TENORM reviewed in
Chapters 7-9. Guidelines developed by EPA for indoor radon and for TENORM
other than indoor radon are compared with guidelines developed by other
organizations, and the committee's views on the reasons for the differences are
presented. Chapter 11 mainly presents summary discussions on the question of
whether the differences between EPA and other guidelines for TENORM have a
scientific and technical basis, specific ways in which the technical approaches to
risk assessment of radionuclides currently used by the EPA and other
organizations differ and whether the differences have been important in
developing guidelines for TENORM, and specific ways in which the differences
between EPA and other guidelines for TENORM are based on policies related to
risk management, rather than scientific and technical issues. Chapter 12 presents
some summary conclusions and recommendations developed by the committee
during the course of this study.
Systeme International (SI) units are used throughout this report.
However, the conventional units for such quantities as activity, exposure, and
dose are given in parentheses in many cases because most regulations in the
United States use the conventional units. The relationships between SI and
conventional units are given in the appendix.
Representative terms from entire chapter:
radioactive materials
