Applicability of Radiation Response Models to Low Dose Protection Standards September 30-October 3, 2018 Pasco, Washington Sponsored by American Nuclear Society
Health Physics Society
Conference website with all papers: https://umtanum.github.io/LowDoseRad/ Introduction This review contains a brief summary of the ANS/HPS Joint Conference on Low Level Radiation, including both an overview of the conference as well as key conclusions deemed to be helpful in planning the path forward. Without future action, this meeting--like those of the past-will have little impact. We plan on continuing activity so that the information and momentum gained from this conference can be captured to productively impact the radiation community. Without special funding, this conference would have had little chance for success. We very much appreciate all those that worked so hard to get the funding, and the favorable response of the agencies, companies and individuals that made the generous contributions to make the conference possible. Almost half of the total money was designated for travel support--without which many of the participants would not have been able to attend. This turned out to be a very successful meeting with some 210 total individuals registered. Beginning with a most unusual but magnificent concert at the front face of the historic B-Reactor, the food, tours and activities that made the meeting a pleasant experience was also a direct result of special funding. In recognition of those who contributed money we have attached a listing in order of the size of their contributions. This conference was almost four years in the making, with Dr. Alan Waltar serving as Chairman for the meeting, along with a most talented and dedicated planning committee that invested an incredible amount of time and energy to make sure this event would and did run smoothly. We put together an excellent international advisory council (IAC), which helped us attract top scientists from around the world. A listing of both groups is attached. In organizing the conference, we developed several specific goals, which were presented by Mike Lawrence (International Chair) at the start of the meeting: 1) Explore the current scientific knowledge and understanding of low-dose radiation effects that provide the scientific basis for radiation protection standards. 1
2) Find areas and models which are used to set standards where we could reach consensus, areas where there was no consensus, and identify areas that need to be modified. 3) Recommend a path forward. It was not the intent of this conference to explore the political side of the standard setting responsibility. Rather, in going forward it was our goal to reach consensus on as many important questions related to the dose-response relationships as possible and to use this information to impact regulations. The scientific evidence of harmful human effects of low dose exposure to radiation is difficult to detect and currently is very limited. We must challenge the concept that it is possible to evaluate precise risk estimates due to low-level radiation, given our wide range of natural background radiation and the high incidence of cancer from all causes combined—both natural and those arising from human activities. We might therefore ask, and, hopefully, reach consensus on what is the lowest level at which we can definitively assess risk, and to what degree it makes sense to regulate at exposures below those levels. We intentionally structured the conference for a singly plenary format, so that ALL conference participants could hear ALL of the presentations and subsequent dialog. Our stated intentions of having radiation epidemiologists and radiation biologists in the same room and at the same time to learn from each other was gratifyingly accomplished. But confining the entire conference to a single plenary format naturally placed considerable pressure on strict adherence to the schedule so that all speakers had time to share their views from the podium, Accordingly, Dr. Waltar appealed to those participating to make sure they limited their presentations to the time allotted. Mike Lawrence challenged all speakers to consider the four following points: 1) Be a strong advocate for your position; that is why you are here. 2) By all means, present additional facts; not alternative facts. 3) Be open to new information; listen and consider how different data and analysis applies to our goals and be open to someone else’s “facts”. 4) Apply the scientific method to help us achieve our goal: observe, experiment, measure, and evaluate. We feel those participating in the meeting were successful in following his instructions. The meeting was organized to optimize the potential for interactions between those in attendance. After the introductory remarks, the current President of the Health Physics Society, Dr. Nolan Hertel, and the Past President of the American Nuclear Society, Dr. Andy Klein, stepped to the podium to provide their support for the conference.
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The program for the meeting is provided as an attachment. We had forty-six presentations in the meeting and seven panels--where we included an additional opportunity for participation from all those registered in the meeting. Each of the panels resulted in active discussions although we had to limit the discussion because of lack of time. The discussions were dynamic but we were able to continually maintain good order and interaction between those with very different opinions. The Meeting The Keynote Address was presented by Dr. David Brenner of Columbia University, where he explained the biophysical argument for the current use of the Linear No Threshold (LNT) model. This was followed by a historical overview of development of radiation protection standards by Dr. Roger O. McClellan. It was then important to have talks from those involved in the decisions related to regulatory standards. Presentations were made by representatives of the ICRP, NCRP, UNSCEAR, IAEA, NRC, and EPA. This session allowed the speakers to let the scientists and others at the meeting know of their needs and regulatory restrictions that each agency must deal with. This laid a useful framework for the meeting. As was the case for each session, this was followed up with a panel discussion to continue the subject and allow the audience to be involved in the information flow. The next session was designed to give the epidemiologists a chance to share the latest data on human populations exposed to radiation. Since epidemiology is the driving force in all regulations, having this session early in the meeting provided the basic groundwork on which the rest of the meeting could be constructed. The session focused on two important populations: 1) the Mayak population of workers exposed to radiation during the development of the atomic bomb in Russia, and 2 the Techa River population exposed to the release of radioactive material into the environment. Both of these populations received doses that were higher than most human populations. This dose was delivered at a low dose rate and was the result of both external and internally deposited radioactive materials. This session resulted in a very good discussion during the panel where questions about both the radiation dose and the biological effects were asked. The bottom line from these presentations was that there was an increase in the cancer frequency in these populations and it was similar to that calculated for the Japanese Abomb populations. The poster session featured during the first evening was very active. The posters received a strong review and played an important part in the meeting. After laying the groundwork for the regulators and the epidemiology studies, the next session was focused on the basics of biology to describe the response at the cell and molecular level to low doses and low dose rate radiation exposure. The take home from this session was basically that the biological response induced by low doses of radiation is very different from the response generated following exposure to high doses. This session thus concluded that the 3
mechanisms of action are distinct as a function of dose and dose rate and provided much evidence for the potential for protective effects following low dose and dose-rate exposures. This provided serious evidence that the LNT model used in radiation protection is not supported by basic science and represents an overestimate of the risk following exposure to low doses and low dose rate radiation exposures. Again, the panel resulted in vigorous discussion with a wide range of different views. With the previous sessions in place it was then possible to discuss the models used to describe radiation dose-response relationships. Much of this session was focused on the response in the low dose region and which models were best supported by the scientific evidence in this region. This is where the three different groups discussed latter found their voices. They were, first the LNT group, second the threshold group, and finally the hormesis group. This discussion seemed to be one of the focuses of much of the discussion in the meeting with little shift in those that seemed to support each of the positions. The meeting then moved from the basic sciences to the impact of radiation regulations, with important presentations on the influence of fear, perception of risk, and costs associated with the current methods of regulating radiation. This impacted the field of medical use of radiation, use of radiation standards for nuclear clean-up, the value of human life, and the use of nuclear power to meet our nations energy needs. All of these areas impact the daily lives of all of us and require a well thought out approach to help us gain the benefits of radiation in each of these important fields. As these areas were discussed, it led naturally to the next session where there were some very important presentations on the impact of fear, regulations, lack of communication and public distrust of authority during the aftermath of the Fukushima accident. The presentations from those impacted by the accident brought a new sense of the importance of this meeting on future actions. What would you do if you were asked to leave your home after a nuclear accident? What level of radiation would make you abandon your home, your lifestyle, your ability to make your own decisions and you family unity to avoid exposure to low doses of radiation delivered at a low dose rate? These questions provided for a new look into each of our backgrounds and would have a wide range of responses depending on the background and fear for each individual. These questions provided a stimulus for our follow-up with a survey to evaluate the feelings of those in attendance. Finally, the conference asked the important question of what are the needs to move forward both in the area of the science as well as in communication, addressing fear and helping understand the risk of radiation in the low dose region. These needs are independent of the type of model used to describe the results in the low dose region and the regulations used to limit the public exposure. Summary There is very little question that the meeting reached the goal of facilitating open exchanges of facts, views, interpretations, hypotheses and theories and of the consequences of optimization of radiation protection with the best possible overall outcome in the service of 4
society. Having succeeded in bringing the radiation epidemiologists and radiation biologists together, there was wide concurrence within both disciplines that they need each other in order to really understand the health effects of low level radiation. Extensive efforts were made to ensure that the interdisciplinary composition of the experts was well balanced and came from a wide range of backgrounds including epidemiology, systems biology, cell and molecular biology, biochemistry, biophysics, health physics, mathematics, model makers, legal socio-economists, physicians, decision makers, administrators as well as having lay people directly impacted by decisions to evacuate. After three days of meeting with this high-powered group it became obvious that there were several areas where we were able to reach near consensus while in other areas, there remained a wide range of views supported by different scientific bases. Additional information will be available as open literature publication of extended abstracts and a commentary of the meeting become available. This will be a special publication of the Health Physics Society, scheduled for release in the spring of 2019. Interviews with key players in the meeting and a complete documentation of the meeting, including videos filmed during the entire conference, will also be forthcoming. The areas of near consensus, as viewed by the organizers of the meeting, are briefly summarized below: First, it was the opinion of the group that the fear of radiation is a serious problem and lack of communication between the scientific community and stake holders seems to be a major contributor to that fear. This fear of radiation is far greater than the scientific data can justify. We have a large data base of human data on which the regulations are largely based, and these data clearly show that radiation at low levels is a very poor carcinogen –especially in relation to other well-known toxins such as smoking. This unsubstantiated fear is reinforced almost daily in the news media, the regulatory actions taken, and has wide spread financial and societal impact. Each of us make decisions daily on medical treatments, nuclear waste disposal, and nuclear energy, etc. that can be influenced by this fear. Second, there was general agreement that there is a need for carefully directed, focused research program that can address regulatory concerns and provide data on the underlying science of low dose radiation effects in humans. Several areas of new research were discussed in the meeting that require additional funding. Application on newly developed techniques and equipment to the understanding the mechanisms of action of high and low doses of radiation remain a fertile field for research. The field of epigenetics was discussed and, in limited data, demonstrated that low doses of radiation resulted in beneficial effects. The need to conduct research focused on linking molecular biology to human epidemiology studies remains high and can lead to significant insights needed to understand the risk of low doses of ionizing radiation in humans. This focused research effort needs to be adequately funded, be international in nature, and be closely coordinated to achieve optimum results.
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Third, there seemed to be a consensus of those in the audience that there is a gross inconsistency related to the setting of restrictive standards in light of the variable background levels of radiation. Many of the standards are set below the natural radiation background and complying with these standards has no measurable benefit in terms of health effects. Further, it fuels the fear of radiation, causes much more harm than good in the case of evacuation, and costs billions of dollars. The natural background level of radiation, which we cannot alter, averages around 3 mSv/year (there are areas where the background is 100 times higher) and medical exposure in the U.S. adds an additional 3 mSv. Similar active discussions were related to the use of 20 mSv/year dose in a nuclear accident or event to determine if it is necessary to evacuate a given area or population. This dose is about equal to two CT scans. About 90 million CT scans are given in the U.S. each year without a detectable health effect. Twenty mSv/year is a dose that is less than the dose to the down winders in Southern Utah received as a result of nuclear weapons testing fallout. Utah has the lowest cancer rate in the nation and southern Utah has the lowest cancer incidence in the state. Evacuation has been shown to have very serious health, social, emotional and economic costs that far outweigh the calculated benefit derived by avoiding the low doses of radiation exposure. Fourth, the discussion on the use of radiation in medicine was evaluated and discussed. It was again the general consensus of the meeting that medical uses of radiation provides great benefit and one should not refuse a medical exposure if it is justified and recommended by the medical experts. The risk from medical exposures was carefully compared to some real data on the benefits associated with medical exposure. There was focus on the use of CT scans since a single CT scan delivers a dose of up to 10 mSv and we deliver over 90 million CT scans per year. The individual risk from this procedure is very small relative to the great benefit derived and the many lives saved each year through the use of CT scans. Another area of concern was the lack young people coming into these fields. Young scientists are needed to insure that proper and new information is available for future decisions related to nuclear activities. However, there are several other areas where serious differences remain. These are listed below, along with a summary of the extensive discussions and data presented by all sides of these controversies. The major differences seem to be related to the shape and slope of the doseresponse relationships in the low dose region. These can be divided into three easily distinguishable groups. The first and oldest group holds the Linear No Threshold (LNT model) to be best for the practice of radiation protection. This group suggests that each and every ionization increases the risk of cancer and genetic effects in humans regardless of the total dose. There is extensive data that suggest that this is not scientifically supported. However, this group advocates the continued use of the LNT model for practical administrative and precautionary reasons. The second group suggests that the data support the fact that the health effects from low doses and low dose rates are well defined and negligibly small and that the LNT model be replaced by a threshold model. Doses below this threshold should be of no concern for the induction of health effects and should be declared “safe�. The strength of this argument is 6
twofold. First, there is lack of evidence of a detectable increase in human cancer incidence in the low dose region, especially if delivered at a low dose rate. This observation is supported by a wide range of molecular, cellular and animal data. Radiation induced disease produced or calculated at these levels of exposure is very small--even with the use of the LNT model. Further, we have exposed almost the whole world to low doses of radiation from fallout, nuclear medicine, and use of radiation in industry, without a detectable increase in human health effects. Thus, it is rather well accepted that the standards set using the LNT model are conservative and do not underestimate the risk. Considerable data support the position that the LNT model is conservative and overestimates the risk. The third group started after the discovery of low-dose-induced cell signal changes with delayed metabolic responses 40 years ago. This discovery has been strengthened recently with the advance of research in cell and molecular biology that demonstrates low doses of radiation increase the gene expression in a different set of genes than those induced by high doses of radiation. Many of the genes activated by low doses of radiation have been postulated to be protective. The research also demonstrated that intracellular, cell/cell and cell/tissue communication is stimulated predominantly by low doses of radiation that lead to stress response type of metabolic alterations, which result in protection against subsequent radiation damage and against non-radiogenic damage in terms of adaptive protective responses. If the radiogenic damage prevention outweighs radiogenic damage, a decrease in the risk is produced and the overall system experiences a hormetic response. Stated differently, the amount of damage and risk induced by the radiation is reduced to a level that is lower than the spontaneous background level. Thus, modeling should include negative values in the low dose region. This group suggests that low doses of ionizing radiation may be essential to the evolution and maintenance of life.
Path Forward The path forward and the total impact of the meeting will be dependent on how well the information from this meeting is accepted, disseminated and incorporated into decisions related to the control of radiation exposures. We, the organizing committee, have made a commitment to continue to work with the collected data and the concept of true optimization to insure that indeed this meeting has a long lasting impact on our understanding of the underlying science of radiation exposure, along with the regulations associated with protecting the public with adequate and appropriate radiation standards. Initial steps have included exploring ways that this initiative can be elevated to a more encompassing international level, with dedicated leadership coming from globally recognized institutions such as the OECD/NEA.
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