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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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24 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: