Speakers and Abstracts
Regulatory Science
Historical Changes, Current Situation and Challenges in Classification of Radiation Effects for Dose Limitation Purposes
Nobuyuki Hamada
Research Institute of Electric Power Industry, Japan
Abstract
Exposure to ionizing radiation causes various health effects, each of which differs greatly in the shape of the dose-response curve, latency, persistency, recurrence, curability, fatality and impact on quality of life. Since 1977, for dose limitation purposes, the International Commission on Radiological Protection has divided all such diverse effects into either stochastic effects with no dose threshold or tissue reactions (formerly termed nonstochastic and deterministic effects) with a threshold. On one hand, effective dose limits aim to reduce the risks of stochastic effects (cancer and heritable effects) and are based on the detriment-adjusted nominal risk coefficients, assuming a linear-nonthreshold dose response and a dose and dose rate effectiveness factor of 2. On the other hand, equivalent dose limits aim to prevent tissue reactions (cataracts and skin changes) and are based on a threshold. Historically, tissue reactions were excluded from radiation detriment calculation, due to a threshold at relatively high dose. However, ICRP now recommends a threshold of 0.5 Gy for cataracts and circulatory disease, and other non-cancer effects on the radar include neurodegenerative disease. This raises a question about the level of risk to be reduced or prevented for cancer, life-threatening non-cancer effects (e.g., circulatory and neurodegenerative disease), and non-life threatening non-cancer effects (e.g., cataracts). The boundary between these two categories is also becoming obscure (e.g., no clear threshold in late occurring cataracts).
This talk gives an overview of historical changes, current situation and challenges in classification of radiation effects for dose limitation purposes.
Biography
Nobuyuki Hamada, RT, PhD has been involved in various radiation effect studies for more than two decades, and a particular focus of his research over the last decade has been placed on tissue reactions (circulatory and ocular diseases, in particular). Currently, he serves on various radiation protection-related committees (e.g., ICRP Task Groups 102 and 111, NCRP PAC 1) and as editor for various scientific journals (e.g., Mutation Research Reviews, PLOS ONE, International Journal of Radiation Biology). He was involved in production of ICRP Publications 126–132 as Associate Editor, NCRP Commentary No. 26 as a Consultant, and NEA Report No. 7265 as a member.
Experimental Radiobiology
Low Dose and Low Dose-Rate Effects in Animals
Gayle E. Woloschak
Northwestern University
Abstract
Based on current knowledge, the health effects of low dose radiation exposure remain ambiguous and require additional study for clarification. Most policies currently in place regulating radiation exposures rely on models developed for high dose and high dose-rate exposures that have been extrapolated inappropriately to low doses and low dose-rate exposures that are encountered environmentally or occupationally. Many new technologies have been developed that have not been adequately applied for low dose radiation research. These technologies can be exploited to provide new insights into the effects of exposures at the occupational and environmental exposure ranges and thus impact nuclear cleanup sites, worker exposure risks, and even low-dose medical diagnostic exposures. Among these technologies are improved statistical and computational approaches for large data analyses, nanoscale resolution of cellular responses, single-cell sequencing and molecular techniques, and many others. Our group has exploited large-scale animal datasets (mouse and dog) and archives to understand matters related to radiation-induced carcinogenesis at low doses and low-dose rate exposures.
Biography
Gayle E. Woloschak is Professor of Radiation Oncology, Radiology, and Cell and Molecular Biology in the Feinberg School of Medicine, Northwestern University. Gayle received her B.S. in Biological Sciences, from Youngstown State University and a Ph.D. in Medical Sciences from the University of Toledo (Medical College of Ohio). She did her postdoctoral training at the Mayo Clinic, and then moved to Argonne National Laboratory until 2001. Her scientific interests are predominantly in the areas of Molecular Biology. Radiation Biology, and Nanotechnology studies, and she has authored over 200 papers. She is editor-in-chief for the International Journal of Radiation Biology, is past-President of the Radiation Research Society, is a member of the National Council of Radiation Protection and Measurements, is a member of Committee-1 for the International Commission on Radiation Protection and serves on a committee studying low dose radiation effects for UNSCEAR.
Radio-epidemiology
Key Takeaways from the Results of the Life Span Study of Atomic Bomb Survivors
Eric J. Grant
Radiation Effects Research Foundation, Japan
Abstract
The Radiation Effects Research Foundation (RERF) and its predecessor, the Atomic Bomb Casualty Commission, have administered the Life Span Study (LSS) of atomic bomb survivors since 1950. This unique cohort of a population of survivors exposed to ionizing radiation provides results that inform radiation protection policy makers around the world.
Due to its long-term follow-up, large range of doses, a population-based cohort, and consistent surveillance methods, the LSS results provide fundamental data informing the long-term health effects from ionizing radiation exposure. Despite these design strengths, the low-dose effects remain uncertain due to several limitations related to statistical power, and variations in background rates due to geographical and other poorly defined factors.
This talk will discuss the primary conclusions from the LSS, the limitations of those results, and how uncertainty puts scientists in a difficult position when faced with questions from the public or the media that require extrapolation beyond the conclusions of the data.
Biography
Eric J. Grant is the Associate Chief of Research at the Radiation Effects Research Foundation (RERF) in Hiroshima and Nagasaki, Japan. Dr. Grant received his BSEE from the University of Michigan and his PhD in Epidemiology from the University of Washington.
RERF's mission is to study the long-term health effects due to radiation exposure to the atomic bombings. Dr. Grant's research has focused on solid cancer risks of radiation exposure. He is the PI of a project bringing Master- and PhD-level students to RERF to complete projects using RERF data. This outreach program has been successful in recruiting students to radiation-related research positions. Eric is also working to improve institutional data sharing policies to improve collaborative research opportunities with students and scientists around the world.
Comparative Toxicology
How Can Chemical Carcinogenesis Shed Light on the LNT Hypothesis in Radiation Carcinogenesis?
James E. Trosko
Michigan State University
Abstract
Within global concerns of “metabolic diseases”, exposures to ionize radiations, ineffective toxicological tests, costly animal tests, governmental restrictions on animals for toxicity testing, and the impossibility to acquire large enough human sample sizes for epidemiological studies. new strategies are needed to test the validity of the Linear No Threshold hypothesis.
Given that human cancers are viewed as a major consequence of radiation exposures, it appears that radiation epidemiologists, radiation biologists and regulators have used cancers associated with exposures to ionizing radiation as the gold standard of potential radiation effects. Yet, these radiation disciplines have ignored knowledge, derived from chemical carcinogenesis, that human carcinogenesis is a multi-step, multi-mechanism process that involves three cellular mechanisms of toxicity, e.g., mutagenesis; cytotoxicity; epigenesis, and one specific cell type of the human body, namely the organ-specific adult stem cell. This process involves three specific phases, namely the “initiation” by mutation of a few critical genes of a single normal organ specific stem cell; followed by clonal expansion of that single cell by a promotion process, caused by non-mutagenic or “epigenetic” endogenous or exogenous agents. After a chronic exposure to these epigenetic agents at threshold levels, in the absence of “anti-promoters”, an “initiated” cell can accrue addition mutational and epigenetic events to acquire the so-called “Hallmarks of Cancer”, that allows this cell to invade tissues and to metastasize into a “cancer stem cell”. A SINGLE ACUTE EXPOSURE OF IONIZING RADIATION, ESPECIALLY AT LOW DOSES, CANNOT BRING ABOUT ALL THESE REQUIRED MECHANISMS OF THE CARCINOGENIC PROCESS.
Biography
James E. Trosko has completed his Ph.D. at the age of 25 from Michigan State University, USA. He is a Distinguished Emeritus Professor at Michigan State University. He spent 3 years as a postdoctoral fellow at Oak Ridge National Laboratory under Drs. Ernest Chu; Dr. Sheldon Wolff and Dr. Richard Setlow. After joining Michigan State University, he obtained an NCI- Career Development award; spent one year at the McArdle Lab for Cancer Research at the University of Wisconsin under Dr. Van R. Potter. Later he was Chief of Research at the Radiation Effects Research Foundation for two years in Hiroshima and Nagasaki, Japan. He spent 2 years at Seoul National University as a Korean “World Class University Professor”. He also spent one year at the ARNAS-Civico-Regional Cancer Hospital in Palermo, Sicily. He has over 450 publications that have been cited over 17,000 times, and his publication H-index is 62.
Regulatory Science II
Research to Recommendations to Standards
Donald A. Cool
Electric Power Research Institute
Abstract
The translation of scientific information into recommendations and regulatory documents is a complex process, with multiple inputs and considerations. In the United States, Federal Agencies are required to utilize a public comment process in the preparation of regulations and significant guidance documents, and to support the rulemaking process with detailed background information and considerations. Scientific information must be combined with risk management strategies through a risk informed development process to prepare recommendations and regulations. In the context of the dose response paradigm for radiological protection, not only must scientific information be compelling, but any proposal needs to ensure adequate protection, provide for consistent and unbiased application of requirements, and be universally applicability to all individuals. It is insufficient to suggest that a regulation be changed simply based on a scientific study, without substantiation and consensus, and without a clear proposal that meets the principles of good regulation. Regulations and guidance must take a prudent approach to risks, provide a consistent proportional approach across the spectrum of doses, give coherence and predictability to users, and pragmatically deal with details. Across a wide spectrum of risks, two risk approaches have traditionally been utilized: a linear relationship of the dose to the risk, or a threshold. More complex functions make a universally applicable system difficult. Additional research and discussion of how to more effectively incorporate complex scientific information is needed if proposals for changes in the current regulatory structures are to be seriously considered.
Biography
Dr. Donald A. Cool is currently the Technical Executive for Radiation Safety with the Electric Power Research Institute, working with member utilities on occupational, public and environmental issues. Before joining EPRI, Dr. Cool served with the U.S. Nuclear Regulatory Commission in various senior management and advisory positions. Dr. Cool is a member of the Main Commission of the International Commission on Radiological Protection and the Chair of ICRP Committee 4 on Application of the Commission’s Recommendations. He is a Council Member of the U.S. National Council on Radiation Protection and Measurements and was Co-Chair of NCRP Council Committee 1 on Radiation Protection Recommendations. Dr. Cool has more than 36 years of experience in Radiological Protection, and is a Fellow of the Health Physics Society.
History
A People-Centered Approach to Radiation Protection
Sumiko Hatakeyama
University of Pennsylvania
Abstract
As a historian of science, my work traces the history of the development of atomic-bomb dosimetry systems and related technologies (e.g., cytogenetic techniques) at the Atomic Bomb Casualty Commission (ABCC) and its successor organization, the Radiation Effects Research Foundation (RERF). This presentation draws on my research to discuss a set of humanist concerns that are important for standard developers and practitioners in the field. Archival materials—such as correspondence, memos, and unpublished reports—as well as technical reports and other publications highlight the inescapable uncertainties that have always underpinned dosimetry work. Often, consensus was as much about policy as about data: uncertainties were “settled” by a series of institutional decisions, which in turn reflect the intricate historical web of cultural, political, and economic interests surrounding the ABCC/RERF. Working with hibakusha—atomic-bomb survivors—and other nuclear victims both within and beyond my research, I have also encountered various situations where laws and regulations exacerbate people’s suffering rather than mitigate or alleviate it. I therefore suggest that the fact that uncertainty has been present in all aspects of radiation research must not be forgotten, and the history of the LNT model should be discussed in this context. Further, any reexamination of the LNT model must acknowledge that primary beneficiaries of regulatory practices ought to be people who are exposed to radiation (actually or potentially), and that individual wellbeing should shape radiation protection practices.
Biography
Sumiko Hatakeyama is a doctoral candidate in History and Sociology of Science at the University of Pennsylvania. Sumiko is interested in exploring the history of nuclear weapons and nuclear power from radiation risk perspective: how radiation risk has been understood, framed and weighed against other risks; and how such risk perceptions, in turn, have influenced nuclear policies.