1
Introduction
Ionizing radiation has a wide range of medical, industrial, military, and commercial applications. However, there are longstanding concerns about its potential to cause harm, even at low doses that may be delivered over long periods of time. A “low dose” of ionizing radiation (referred to as “radiation” in this report unless clarity is needed to distinguish from non-ionizing radiation) is generally taken to mean a dose below 100 milligray1 (mGy; see Box 1.1 for basic radiation terms and units), and the term “low dose rate” is taken to mean a radiation dose rate of less than 5 mGy per hour. High doses of radiation can cause cell death promptly, and the damage may be extensive enough to adversely affect tissue or organ functions. Low doses of radiation delivered over long periods of time do not cause prompt tissue or organ damage but may cause cellular damage that increases an individual’s long-term risk of cancer and hereditary disorders in a stochastic fashion.
Current radiation protection standards for low-dose and low-dose-rate exposure focus on protection against such stochastic effects. The risk of cancer following low-dose and low-dose-rate exposure is assumed to increase linearly with increasing dose and to increase after even very low-level exposures, albeit as very small excess risks. This assumption is based on biophysical observations regarding the stochastic nature of radiation energy deposition and resultant induction of DNA damage, as well as analysis of the shape of the relationship between radiation dose and cancer risk (referred
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1 The definition of low-dose radiation is in line with that of national and international advisory bodies and entities with radiation protection responsibilities. For comparison, the annual average dose due to background radiation in the United States is about 3 mSv.
to as the “dose-response curve”) from epidemiological investigations. For low-dose and low-dose-rate exposures, scientific review committees have found that radiation is less effective per unit dose at causing cancer at low doses and low dose rates than at high doses and high dose rates. This difference in effectiveness is formulated by the application of a dose and dose-rate effectiveness factor when deriving risks at lower doses and dose rates from those observed at higher doses and dose rates (ICRP, 2007; NRC,22006a).3
Public perception and acceptance of radiation exposure is influenced by the context in which radiation is used (Slovic, 2012), but uncertainties associated with health effects attributed to low-dose radiation generally create communication challenges for every situation where exposure occurs. Some communication challenges recognized by radiation protection regulators include justifying regulating radiation to low levels in the presence of inconclusive scientific evidence of risk, addressing questions regarding a “safe” level of radiation exposure and about individual risks, and using appropriate risk comparisons.4 Communicating about additional low-dose radiation exposures in relation to background natural radiation exposure levels also presents challenges.
Today, concerns about risks at low doses and low dose rates influence patient acceptance of medical diagnostic procedures, as well as U.S. government decisions and policies related to the future of nuclear power and clean energy policies, management of nuclear waste, and plans for and responses to radiological threats. Concerns about radiation risk also raise questions as to whether the public and workers are adequately protected from current environmental and occupational radiation exposures and from potential new sources of exposure such as rare earth element and lithium mining to support green energy and long-term energy policies in the United States.
In many communities directly impacted by past or current radiation releases,5 decisions related to radiation protection policies as well as radiation research are viewed with skepticism and distrust. This distrust originates
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2 NRC stands for the National Research Council. As of July 2015, the name under which the three academies fulfill their mission of advising the nation and conducting related activities became the National Academies of Sciences, Engineering, and Medicine (the National Academies), and publications are referred to as National Academies publications.
3 The International Commission on Radiological Protection (ICRP) is reviewing current science relevant to the estimation of risk at low doses and low dose rates and will provide recommendations on how this risk is estimated for radiological protection purposes.
4 Jessica Wieder, Environmental Protection Agency, presentation to the committee on October 27, 2021.
5 Impacted communities in the context of this report include Indigenous communities; atomic veterans; nuclear workers; uranium miners, millers, transporters, and their families; and individuals or communities impacted by radioactive contamination or nuclear fallout due to nuclear weapons testing, offsite radiation releases from nuclear weapons production sites, and nuclear waste cleanup activities.
from the Atomic Energy Commission, was fostered by the Department of Energy’s (DOE’s) secrecy during the nuclear weapons program activities, and has persisted over multiple generations. Some impacted communities express continuing distrust toward the U.S. government because of their views on governmental unwillingness to accept responsibility for past radiation exposures and failure to develop programs that adequately compensate all impacted communities. (See discussion in Sections 2.1.6 and 6.7.)
This report argues that the increasing numbers of people exposed to radiation (primarily to medical radiation; see Chapter 2) and the improved capabilities to quantify health risks at low-dose and low-dose-rate exposures (see Chapter 5, specifically Sections 5.2 to 5.4) make it both urgent and feasible to improve the scientific understanding of the adverse human health effects from radiation exposures at doses and dose rates experienced by the U.S. population. This report also argues that a revitalized multidisciplinary low-dose radiation program that leverages advances in biotechnology, improved mechanistic understanding of disease processes, and research infrastructure, can provide evidence on risks from low doses of radiation for different health outcomes, thereby alleviating the need to rely on risk estimates interpolated from higher doses (see Chapter 5, specifically Sections 5.2 to 5.4). To assist with developing a low-dose radiation research strategy in the United States, this report sets priorities to guide research for a multidisciplinary coordinated low-dose radiation program that involves the broader U.S. research enterprise and extends beyond the resources of any one federal agency (see Chapter 5, specifically Sections 5.2 to 5.4). The recommended strategic agenda was developed to be neutral in terms of the impact of the proposed research on assessment of radiation health risks and consequently
its potential impact on radiation protection policy and practice in the United States. This report also recommends essential elements (see Chapter 6) for a successful low-dose radiation program that achieves its scientific goals and which includes taking steps to mitigate the challenges of distrust toward some government-sponsored radiation research.
1.1 LOW-DOSE RADIATION EXPOSURES TO THE U.S. POPULATION
Agencies with radiation protection responsibilities including the Environmental Protection Agency and advisory bodies such as the National Council on Radiation Protection and Measurements communicate radiation exposures to the U.S. population in terms of average annual dose. However, there is notable variation among individuals and across populations in the types of sources of radiation and in the frequency, level, and duration of exposure (Simon and Linet, 2014), and therefore, these averages, although informative, do not identify individuals or communities that have received doses higher than the average and therefore are at higher risk.
The estimated annual average dose to members of the U.S. population is just over 6 mSv.6 Half of the estimated average annual dose (about 3 mSv) comes from natural background radiation, primarily radon, and most of the remaining dose from medical diagnostic procedures (3 mSv; see Figure 1.1). Doses from industrial applications (including operation of nuclear power plants) and occupational exposures account for less than 0.1 percent of the average annual dose to the total U.S. population.7 The contributions from other radiation sources to the average annual dose to the U.S. population such as from DOE’s nuclear facilities and nuclear weapons testing is currently smaller (NCRP, 2009a). However, they are of concern to the impacted communities due to the disproportionate level of exposure compared to the general U.S. population and the higher past exposures (see Sections 2.1.6 and 2.1.7 for discussion and Table 2.1 for approximate sizes of currently exposed populations).
The global average annual radiation dose is about half that of the United States (about 3 mSv). This difference is primarily due to the lower global exposure from radon and the much lower global exposure from medical diagnostic procedures (see Figure 1.1), even in countries with similar health care levels as the United States.8
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6 See https://www.epa.gov/radiation/radiation-sources-and-doses.
7 See https://www.epa.gov/radiation/radiation-sources-and-doses and Table 2.1 of this report for the estimated annual dose to nuclear workers and other occupationally exposed populations.
8 For example, the average dose from medical diagnostic procedures to the population is about 2 mSv in Germany and less than 0.5 mSv in the United Kingdom (UNSCEAR, 2008). The United Nations Scientific Committee on the Effects of Atomic Radiation is in the process of updating these estimates.
NOTE: mSv = millisievert.
SOURCES: U.S. data from the Environmental Protection Agency, https://www.epa.gov/radiation/radiation-sources-and-doses, which subsequently uses NCRP (2009a); global data from UNSCEAR (2008).
Although some low-dose radiation exposures, natural or human-made, can be avoided or controlled (e.g., by limiting occupational exposures and those to members of the public from nuclear power plant routine operations and accidental releases or by remediating high radon levels in homes), others may be unavoidable (e.g., background radiation exposures from space and terrestrial radiation, or environmental contamination sources). To prevent adverse health outcomes caused by radiation during routine, accidental, or malevolent exposures to radiation, regulatory agencies within the United States and internationally have established radiation protection systems (see Chapter 3) that include exposure limits guidance that apply to a wide range of settings in which such exposure may occur to occupational workers and members of the public. Setting exposure limits and providing appropriate guidance requires an assessment of risks at low doses of radiation.
Cancer is the health outcome most commonly studied for its association with low doses of radiation. It is a common and heterogeneous disease in etiology and phenotype and is influenced by genetic, lifestyle, and environmental factors. Therefore, detecting the effects of low-dose radiation on cancer risk is challenging. Statistical estimates of low-dose cancer risk have become more precise as larger studies have been conducted. Fifteen
years ago, when considering postnatal9 exposure to radiation, a statistically significant estimate of the effect of radiation exposure on cancer was only directly detectable above about 100 mGy (NRC, 2006a; UNSCEAR, 2006a). Below that exposure level, risk estimates were derived from statistical models fitted to data derived from studies of populations that were exposed to higher doses of radiation, most notably the follow-up study of the Japanese atomic bombing survivors in Hiroshima and Nagasaki who received an average weighted absorbed colon dose of 200 milligrays (see Section 4.5.6). More recently, other cohort studies involving populations with medical, occupational, and environmental radiation exposures have allowed for direct estimates of the effect of radiation exposure on cancer risks following protracted exposures that are more relevant to the types of exposures received today by the U.S. population (Kitahara et al., 2015). These epidemiological studies have provided direct evidence that postnatal external exposure to radiation below 100 mGy is associated with elevated cancer risk. Evidence regarding low-dose internal exposures (aside from radon progeny) and different types of radiation is more limited (see, e.g., Schonfeld et al., 2013).
The quantitative relationship between postnatal exposure to radiation and cancer risk at the very low doses most commonly encountered by the U.S. population (e.g., below about 10 mGy) is not well established. There is also increasing evidence, some of which is summarized in this report, that low-dose radiation exposure may be associated with non-cancer health outcomes such as cardiovascular disease, neurological disorders, immune dysfunction, and cataracts. In epidemiological studies of populations exposed to higher doses of radiation, radiation-associated excesses of these non-cancer adverse health outcomes have been observed. In recent studies, such associations have been observed at doses lower than previously considered important for these effects (see Section 2.2). Therefore, elucidating their occurrence at low doses is of increasing interest. These other health effects are currently classified as “tissue reactions,” and it is assumed that they do not occur below a certain threshold. However, this classification remains to be reassessed based on more recent studies of their induction at low levels of radiation (Clement et al., 2021; Little et al., 2021a).
Well-designed experimental studies in cells and animals or other models can supplement and redirect epidemiological studies in several contexts including where epidemiology has potential issues of inconsistency, bias, or lack of suitable cohorts. Experimental studies also provide mechanistic insights on the pathways leading to radiation-related cancer (NCRP, 2015a) and other diseases. Integration of information from radiation biology and epidemiology can be achieved by adding mechanistic information
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9 The association between low-dose radiation received prenatally by the fetus in utero and cancer risk is discussed in Section 2.2.1.
in cancer and other adverse health effects’ risk models (Kaiser et al., 2014) or by using biological markers in epidemiological studies as described in Pernot et al. (2012) to enhance low-dose health risk assessment (NCRP, 2020a).
1.2 LOW-DOSE RADIATION RESEARCH IN THE UNITED STATES
Research focused on the mechanisms and outcomes from exposures to low-dose radiation can answer critical questions relevant to radiation protection of the U.S. population. A 2017 Government Accountability Office (GAO) report stated that between 2012 and 2016, DOE and the National Institutes of Health (NIH) were the two federal agencies primarily supporting low-dose radiation research in the United States. Within that period, the two agencies combined accounted for 98 percent of federal funding for low-dose radiation research, with the remaining 2 percent provided by other agencies including the Environmental Protection Agency, the U.S. Nuclear Regulatory Commission, the National Aeronautics and Space Administration (NASA), and the Centers for Disease Control and Prevention (GAO, 2017; see Figure 1.3).
DOE and its predecessor organizations, the Atomic Energy Commission (AEC) and the Energy Research and Development Agency (ERDA), have a long history of supporting research on radiation effects in academia, national laboratories, and elsewhere, in support of the U.S. nuclear weapons program. Starting in the 1940s, research supported involved human experiments10 and the assessment of the effects of radiation on human health in the nuclear workforce (NRC, 2006b); studies of the effects of radiation on the Japanese atomic bombing survivors (Putnam, 1998); large radiobiology animal life-span studies (Brooks, 2012; NRC, 1998b; Zander et al., 2019);11 elucidation of fundamental DNA damage and repair mechanisms (Bedford and Dewey, 2002); development of technologies including flow cytometry and sorting (Fulwyler, 1980; Van Dilla et al., 1969) and chromosome analysis to assess the effects of radiation in humans (Bigbee et al., 1997; Gray et al., 1992); and elucidation of the role of the microenvironment in carcinogenesis (Rizki and Bissell, 2004). This body of research made significant contributions toward understanding radiation health effects and radiation risk management. However, the management and use of the information by AEC, ERDA, and DOE have been criticized
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10 See https://ehss.energy.gov/ohre/roadmap/roadmap/index.html.
11 Materials from the animals and detailed information are available at the Woloschak Laboratory website at Northwestern University (see janus.northwestern.edu/wololab). Archived data and tissues continue to be used today in laboratories in the United States and around the world.
for conflict and lack of transparency. In addition, human experiments and studies raised ethical concerns (DOE EHHS Openness, 1995).
In 1990, DOE initiated the Human Genome Project and co-managed it with NIH (Cook-Deegan, 1994; Patrinos and Drell, 1997) in recognition that detailed knowledge of the structure and function of the human genome can improve understanding of the health effects of DNA damage by radiation and chemicals (NRC, 1998b). The Human Genome Project generated the first publicly available reference genome and catalyzed many breakthroughs including inexpensive nucleic acid analysis technologies that have revolutionized biology, biotechnology, and drug development. The organizational rigor required to manage the Human Genome Project provided lessons learned to be applied in future programs (Gibbs, 2020).
DOE terminated the radiobiology life-span studies in the mid-1990s and, after some years of not supporting radiobiology research, initiated the low-dose radiation program in 1999 which continued until 2016. DOE’s Low-Dose Radiation Research Program almost exclusively funded radiation biology studies and only supported one epidemiological study, the Million Person Study (Boice et al., 2022a),12 toward the final years of its operation. The program took advantage of new technologies available at the time as well as advances in molecular and cell biology made by the Human Genome Project and expanded knowledge of molecular and cellular responses to radiation and helped better understand biological responses at low doses of radiation. For example, research supported by the Low-Dose Radiation Research Program (1) found that exposure to low-dose radiation resulted in both qualitatively as well as quantitatively different cellular and molecular responses when compared to higher doses; (2) provided evidence of systemic non-targeted effects of radiation, including bystander effects and genomic instability measured in cells not directly “hit” by the radiation; and (3) identified adaptive protective responses and molecular pathways activated by low-dose radiation (Brooks, 2012).
Over the course of the program, DOE provided an average of $14 million per year to universities and national laboratories for research on low-dose radiation. At its peak, in 2008, the program funded research at 45 institutions nationally and internationally. Just prior to its termination in 2016, it funded only two DOE-affiliated national laboratories—Pacific Northwest National Laboratory and Lawrence Berkeley National Laboratory (highlighted in yellow in Figure 1.2).
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12 More than 30 cohorts that fit in 7 broader groups make up the Million Person Study. The groups are DOE workers, nuclear weapons test participants, nuclear power plant workers, industrial radiographers, medical radiation workers, nuclear submariners and other U.S. Navy personnel, and radium dial painters. These groups were exposed to radiation from 1913 to the present (Boice et al., 2022a).
SOURCE: William F. Morgan, Pacific Northwest National Laboratory, presentation at a National Academies meeting on November 4, 2014, based on data provided by DOE.
The low-dose program was terminated because DOE’s Office of Science Biological and Environmental Research (BER) program shifted its research focus to bioenergy and environmental research. BER’s current mission is to “support scientific research and facilities to achieve a predictive understanding of complex biological, Earth, and environmental systems with the aim of advancing the nation’s energy and infrastructure security.”13 In support of its mission, BER has remained at the forefront of genome biology research and has also produced computational infrastructure and modeling capabilities that are run on DOE’s fastest supercomputers, among the most capable in the world.14 However, as BER shifted its focus to bioenergy and environmental research, its interest and expertise in radiation research have markedly diminished. Despite suggestions from the Low Dose Radiation Expert Subcommittee of the Biological and Environmental Research Advisory Committee15 for the scope of a small program on radiation health
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13 See https://www.energy.gov/science/ber/biological-and-environmental-research.
14 See https://www.energy.gov/sites/default/files/2021-06/03%20BER%20Program%20Narrative%206_16_21.pdf.
15 The Biological and Environmental Research Advisory Committee (BERAC) is tasked with advising the leadership of DOE’s Office of Science on scientific and technical issues related to the BER program.
and an indication of promising research directions to pursue (BERAC, 2016), and a recommendation to create and lead an interagency coordinating mechanism for low-dose radiation research (GAO, 2017), DOE has maintained the position that it should not be leading low-dose radiation research and that low-dose radiation research does not align with current BER priorities (AIP, 2021; BERAC, 2016; GAO, 2017).
Federal support for low-dose radiation research dropped by about half between 2012 and 2016 following the termination of DOE’s low-dose program in 2016 and parallel decline in funding by NIH (see Figure 1.3). According to DOE officials, decreases in funding for the program reflected the shift of research focus described above. At NIH, the decline in radiation research funding was not due to research priority changes but instead coincided with across-the-board budget cuts at federal agencies and a decline in the number of high-quality radiation proposals submitted to NIH as judged by NIH’s peer-review process (GAO, 2017).
NOTES: Funding from the Department of Energy (DOE) shown in the graph reflects that from the Biological and Environmental Research program in support of the low-dose program and from other DOE offices. The other five agencies that funded low-dose radiation research during that period were the U.S. Nuclear Regulatory Commission, the National Aeronautics and Space Administration, the Department of Defense, the Centers for Disease Control and Prevention, and the Environmental Protection Agency.
SOURCE: GAO (2017).
Today, a few federal agencies conduct or fund research in radiation topics that may also include low-dose radiation exposures, but none explicitly focuses on low-dose radiation research. This makes it difficult to assess the current effort and available funding dedicated to low-dose radiation research (see Chapter 4). Also, radiation research supported by these agencies lacks leadership and is generally fragmented, as it is set to respond to specific missions and not to an overarching strategic vision that aims to understand critical scientific issues relating to low-dose radiation. A much larger number of federal agencies, although they do not conduct or fund low-dose radiation research, use the research findings to meet their statutory responsibilities to set up radiation protection standards and guidelines, assist in the response to nuclear or radiological incidents, administer radiation compensation programs, or carry out other activities relevant to their missions that require knowledge of low-dose radiation risks (see Figure 1.4 and Chapter 3). Without good understanding of these risks, these agencies base decisions on potentially inaccurate information.
Attempts have been made in Congress to reestablish the low-dose radiation research program every year since its termination, in each case with DOE as the program-managing agency. In 2018, Congress passed legislation to resume the program (Department of Energy Research and Innovation Act, Public Law 115-246), and in 2021 it passed additional legislation (Consolidated Appropriations Act, 2021, Public Law 116-260; see Appendix A) that included directing the Secretary of Energy to enter into an agreement with the National Academies of Sciences, Engineering, and Medicine (the National Academies) to develop a long-term strategic and prioritized research agenda for low-dose and low-dose-rate research. The 2021 law states two goals for the program:
- Enhance scientific understanding of, and reduce uncertainties associated with, the effects of exposure to low-dose and low-dose-rate radiation; and
- Inform improved risk-assessment and risk-management methods with respect to such radiation.
The law also provides several clauses including coordination of the low-dose radiation program with the Physical Science Subcommittee of the National Science and Technology Council (NSTC) within the White House’s Office of Science and Technology Policy (see Section 4.1.6 for its task) and an evaluation of the low-dose radiation program by GAO in 2023. Authorized funds for the low-dose program started at $20 million in 2021 and will reach $40 million in 2024 (see Appendix A). The appropriated funds in 2021 were $5 million.
Despite authorization to start the program and appropriation of limited funds, DOE has not reestablished a low-dose radiation program of the
scale and scope defined in the Consolidated Appropriations Act, 2021.16 In addition, BER did not direct the limited appropriated funds to support research focused on developing and testing new hypotheses that could provide foundational direction for the new program. Instead, DOE directed appropriated funds to support a project on artificial intelligence in cancer research carried out at three national laboratories (see Section 4.1.1).
1.3 STUDY TASK AND APPROACH
In response to the Consolidated Appropriations Act, 2021, the National Academies entered into an agreement with the Biological Systems Science Division in DOE’s Office of Science/BER (referred to as DOE’s Office of Science in the report) in April 2021. The charges agreed upon between DOE and the National Academies go beyond the original congressional charge to the National Academies as indicated in the Consolidated Appropriations Act, 2021. For example, in addition to developing a long-term strategic and prioritized research agenda for low-dose and low-dose-rate radiation research within DOE, the National Academies was also tasked by DOE with defining the health and safety issues that need to be guided by an improved understanding of low-dose and low-dose-rate radiation health effects and with identifying the essential elements of a low-dose radiation program as well as with addressing coordination with other entities. The complete Statement of Task is shown in Box S.1. A separate congressional directive (American Innovation and Competitiveness Act of 2017, Public Law 114-329) aims to develop a strategy for coordination of low-dose radiation research conducted across federal agencies and tasked NSTC with the coordination (see Section 4.1.6).
This study was carried out by the Committee on Developing a Long-Term Strategy for Low-Dose Radiation Research in the United States (referred to as “the committee” in this report), which was appointed by the president of the National Academy of Sciences. Brief biographies of the committee members and staff involved in this study are provided in Appendix B. The committee comprises experts in disciplines relevant to the study request, namely radiation biology, epidemiology, and biostatistics; radiation training and education; cancer and molecular research; health physics and dosimetry; risk assessment; economics; and scientific program development and management.
The committee collected the information it needed to write this report from July 2021 to February 2022. During that period, the committee received more than 80 presentations during 7 public meetings.17 Invited
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16 Todd Anderson, DOE, presentation to the committee on January 24, 2022.
17 All committee meetings took place via video-conferencing because of the COVID-19 pandemic and associated travel restrictions.
presenters included national and international subject-matter experts; congressional, federal, and state representatives; national laboratory staff; university researchers; and representatives from nongovernmental associations. The committee also invited presentations from members of and advocates for communities exposed to radiation as a result of the U.S. nuclear weapons program. These included officials and representatives of Indigenous communities; atomic veterans; nuclear workers; those individuals or communities impacted by radioactive contamination or nuclear fallout due to nuclear weapons testing or by radioactive fallout from nuclear weapons production sites (downwinders) and those impacted by nuclear waste cleanup activities. Appendix C provides the list of presentations the committee received during its information-gathering meetings, and these presentations and meeting recordings are posted on the National Academies website for open access.18
In addition to these information-gathering meetings, several committee members attended scientific meetings organized by other entities that addressed low-dose radiation issues including the Radiation Research Society’s annual meeting and webinars organized by the National Council on Radiation Protection and Measurements, NASA’s Human Research Program Space Radiation Quality Workshop, the International Society of Radiation Epidemiology and Dosimetry, the Electric Power Research Institute, and the National Academies. The committee also received written comments, both solicited and unsolicited, from government agencies, technical experts, and members of the public. Most of the commenters were based in the United States, but the committee also received comments from individuals and organizations concerned with radiation-related issues in Japan. These written comments were helpful in informing the committee about perspectives related to the study and for uncovering useful data sources and documents.
A number of the commenters were specifically concerned that the committee’s report would reflect a pro-DOE bias because the study was funded by DOE. The National Academies study process is designed to protect the integrity and independence of the committee’s work. To comply with the procedures implementing Federal Advisory Committee Act, Section 15, under which this committee operated, in the course of the study the information received by the committee was made available to the public upon request through the study’s public access file.19 Also, according to National Academies study processes, the committee kept an arm’s-length relationship
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18 See https://www.nationalacademies.org/our-work/developing-a-long-term-strategy-for-low-dose-radiation-research-in-the-united-states.
19 Inquiries and requests for the list of the public access file materials can be made to the National Academies’ Public Access Records Office (see https://www8.nationalacademies.org/pa/managerequest.aspx?key=DELS-NRSB-21-02).
with the study’s sponsor (DOE) in order to preserve its independence. For example, the sponsor did not have an opportunity to see the committee’s draft findings and recommendations or otherwise appear to influence the content of the report.
1.4 REPORT ROADMAP
This report is organized in six chapters:
- Chapter 1 (this chapter) provides background information on low-dose radiation exposures to the U.S. population, the history of the low-dose radiation research program, and the study request.
- Chapter 2 discusses exposure sources that result or could result in low-dose radiation exposures to members of the U.S. population and the main health effects of concern associated with low-dose radiation exposures. This chapter addresses Charge 1 of the Statement of Task.
- Chapter 3 addresses the radiation protection framework in the United States and economic impacts of decisions related to changes in this framework. This chapter addresses Charge 7 of the Statement of Task.
- Chapter 4 addresses the status of low-dose radiation research in the United States. This chapter addresses Charge 3 of the Statement of Task and provides some background information to address Charge 6.
- Chapter 5 provides the committee’s recommendation on the research priorities for the low-dose radiation program. This chapter addresses Charges 2 and 4 of the Statement of Task.
- Chapter 6 provides the committee’s recommendation on the essential elements of the low-dose radiation program. This chapter addresses Charges 5 and 6 of the Statement of Task as well as parts of Charge 4 (on training and public engagement).
