Nuclear and radiological incidents arise from releases of radioactive materials following accidents and terrorist attacks. Such releases can cause deaths, injuries, and a range of psychosocial effects to emergency responders and members of the public. Affected members of the public (referred to as “populations” in this proceedings) may require immediate medical care and follow-up, dose assessments to ascertain exposures to radiation, and monitoring to identify adverse long-term physical and psychological impacts.
In the United States, state and local agencies are responsible for population monitoring following a nuclear and radiological incident (HHS-CDC, 2014). HHS, through ESF #8–Public Health and Medical Services, has the responsibility of coordinating federal resources to assist state and local agencies with responding to the public health and medical consequences of such an incident (DHS-FEMA, 2016a,b). ESF #8, when activated, is coordinated by ASPR. CDC is responsible for assisting state and local agencies with long-term population monitoring including establishing a radiation registry. CDC also performs many of the administrative functions of ATSDR, an independent operating agency within HHS directed by congressional mandate to perform health surveillance and registries.
The experiences from the 2011 Fukushima Daiichi Nuclear Power Plant accident in Japan and most recently the 2017 Gotham Shield National
Level Exercise1 exemplified the need for planning for efficient and timely health effect surveillance for a large number of affected populations. CDC recognizes that an effective analysis of what type of registry needs to be set up and who to include cannot happen during the response to an incident while the emergency management community focuses on life-saving activities, and identified the need for planning before an incident occurs.
CDC asked the National Academies to organize a workshop to discuss challenges and considerations for setting up a radiation registry for monitoring long-term health effects of populations affected by a nuclear or radiological incident in the United States (see Sidebar 1.1 for the workshop’s Statement of Task). The workshop on Challenges in Initiating and Conducting Long-Term Health Monitoring of Populations Following Nuclear and Radiological Emergencies in the United States was held on March 12–13, 2019, at the National Academies facilities in Washington, DC. The workshop’s goal was to provide a forum for exchanging information, sharing experiences and good practices, and expressing opinions on important activities related to planning in advance for a radiation registry.
The workshop was organized by a committee of seven experts chaired by Dr. Jonathan Fielding (University of California, Los Angeles [UCLA]), and featured a range of presentations on the topics listed in the Statement of Task. The workshop also featured a panel discussion with international, federal, state, and local government representatives to trigger an exchange of viewpoints with audience participation (see Figure 1.1). Appendix A of this proceedings provides the workshop agenda, and Appendix B provides biographical information on the workshop organizing committee members, speakers, and panelists.
A number of participants said that the workshop achieved its goal and some commented on its value in bringing the emergency management community together to discuss the challenges for setting up a radiation registry. For instance, a representative of a local health department in Texas noted that his initial concern with attending the workshop was that the federal vision regarding a radiation registry would outstrip local capacity. Instead, he found that the workshop demonstrated the strength of federal, state, and local partnerships. He also heard that representatives from various organizations with different missions and perspectives have a common understanding of the challenges and a realistic view of the possibilities regarding
1 The 2017 Gotham Shield National Level Exercise involved a scenario of a 10 kiloton (kT) IND being detonated in the New Jersey/New York metro area. It was a 4-day exercise with the majority of the activities being response-related rather than recovery-related.
setting up and maintaining a radiation registry following a nuclear or radiological incident.
However, a dose reconstruction expert observed from the workshop discussions that there was compartmentalization of resources across agencies and organizations without a common plan for coordinating those for setting up a radiation registry. The expert expressed his hope that the workshop would assist with addressing this problem and offer for consideration a list of priorities, which, if addressed by the emergency management community, can help create a coherent and executable plan for setting up a radiation registry. Chapter 2 of this proceedings summarizes opinions on eight potential pre-planning activities that were distilled by the rapporteur (Dr. Ourania Kosti, the National Academies) from the workshop discussions.
This Proceedings of a Workshop was prepared by the workshop rapporteur as a factual summary of what occurred at the workshop. The planning committee’s role was limited to planning and convening the workshop. The views contained in the proceedings are those of individual workshop participants and do not necessarily represent the views of all workshop participants, the planning committee, or the National Academies.
This section provides background information and context on radiation health effects, the expected impacts of different nuclear or radiological incidents, and radiation dose reconstruction for assessing those impacts. Most of the information summarized in this section was provided by presenters during the plenary session of the workshop.
Radiation health effects of those affected by a nuclear or radiological incident depend on the dose of radiation received. Exposure to high levels of radiation can kill hematopoietic or gastrointestinal stem cells, resulting in acute radiation syndrome (ARS). Clinical symptoms of ARS include nausea, vomiting, and diarrhea and can manifest within hours or days following exposure. Patients with ARS will require ongoing screening and monitoring; death or recovery from ARS typically occurs within weeks.
Generally speaking, individuals exposed to whole body doses of 2–3 gray (Gy) will recover with appropriate hospital care; at higher doses, however, cytokine therapy and in some cases bone marrow transplants are additionally warranted,2 and if exposures exceed 10 Gy, the patient is unlikely to recover.
Specialized centers such as the Radiation Emergency Assistance Center/Training Site (REAC/TS) provide advice, management, and education to health care providers about ARS and other radiation injuries. Dr. Carol Iddins, director of REAC/TS, noted that the center deploys its capabilities both nationally through the Department of Energy’s National Nuclear Security Administration and internationally through the World Health Organization’s (WHO’s) Radiation Emergency Medical Preparedness and Assistance Network or the International Atomic Energy Agency’s (IAEA’s) Radiation Assistance Network.3
Exposure to whole-body doses of less than about 2 Gy does not generally cause immediate health effects but it can increase the overall risk of developing radiation-related disease in the future. In addition, individuals who receive high doses of radiation and survive ARS could have a greater risk of developing radiation-related disease later in life, depending on the level of radiation exposure (Sachs and Brenner, 2005). The main stochastic effect of concern following radiation exposure is cancer. Leukemia and thyroid cancers can manifest a few years after exposure, and other types of cancer can develop decades later.
Epidemiological studies on radiation-exposed populations such as the survivors of the atomic bombings in Hiroshima and Nagasaki have shown significant increases in cancer risk at high and moderate doses and at doses as low as the range from 0–100 milligray (mGy) (Grant et al., 2017). This is consistent with epidemiological studies in children who received medical exposures from computerized tomography scans (Berrington de Gonzalez et al., 2016).
2 Dr. David Brenner (Columbia University) pointed out that LD50, the whole-body dose of radiation expected to cause death in 50 percent of an exposed human population, is about 3–4 Gy without treatment and about 7 Gy with appropriate hospital treatment.
3 Dr. Iddins did not discuss the center’s capability to respond to large-scale incidents.
Current understanding of radiation health effects led some workshop participants to consider three rather distinct groups of populations who may require long-term health monitoring following a nuclear or radiological incident through a radiation registry:
- Those who exhibited clinical symptoms related to ARS and require continued medical follow-up or those who received high doses without exhibiting clinical symptoms but are likely to exhibit stochastic effects like cancer in the future.
- Those who received moderate radiation doses within the range where stochastic effects are likely.
- Those who received low radiation doses where stochastic effects like cancer are less likely.
A potential radiation registry could enroll individuals in one or more of these categories.
The impacts of a nuclear or radiological incident will vary depending on the type of the incident and therefore the size of the radiation registry that enrolls the affected individuals will also vary. Dr. Stephen Musolino (Brookhaven National Laboratory) illustrated four nuclear/radiological scenarios to help contextualize the expected radiation dose impacts to the exposed populations (see Figures 1.2–1.5). He clarified that the actual dose impacts depend on a number of factors including whether there is a warning before the incident occurs and if members of the public had time to take protective actions such as evacuating the area or sheltering in place; the time during the day that the incident occurs; and meteorological conditions. The dose impacts presented by Dr. Musolino were derived using the National Atmospheric Release Advisory Center dose projection models. Impacts for doses lower than 100 mGy (or 10 rad) were not discussed or shown in the figures he presented.
The scenarios illustrated were
- A 10 kT IND surface detonation in New York City, representative of a terrorist attack (see Figure 1.2a–b). Following this scenario, the impact to the physical infrastructure will be immense, and there will be an overwhelming number of casualties with physical trauma and thermal burns. Prompt radiation effects will be greatest near the epicenter of the detonation, causing those in close proximity and who survive the blast wave to be afflicted with ARS. Radiation levels will decrease with distance from the point of the
- A 100 kT high-altitude burst would be representative of a state-sponsored weapon detonated at 1,000 feet above New York City, which is representative of a nation-state attack (see Figure 1.3a–b). The immediate effects from this scenario extend further compared to the previous scenario. Dr. Musolino estimated that approximately 500,000 people will receive doses within the range of 100 mGy–2 Gy (or 10–200 rad) by the immediate detonation effects (see Figure 1.3a). However, this scenario is much less impactful from fallout compared to a surface detonation and fewer people (about 100,000) will receive doses within the range of 100 mGy–2 Gy (or 10–200 rad) from the fallout (see Figure 1.3b).
detonation. Fission and activation products will combine with the massive volume of valorized material that is uplifted by the mushroom cloud and be carried at long distance (160 kilometers [about 100 miles] or more) and deposit as fallout. As a result, a large population will be at risk of exposure to a lethal level of radiation in the hours and days post detonation. Dr. Musolino estimated that approximately 200,000 people will receive doses within the range of 100 mGy–2 Gy (or 10–200 rad) by the immediate effects of the detonation (see Figure 1.2a) and 700,000 people will receive similar doses from the fallout (see Figure 1.2b).
- A nuclear power plant accident that involves the San Onofre Nuclear Generating Station4 in California was modeled as a case study. Dr. Musolino said that in contrast to the previous scenarios where there will likely be little to no warning, a nuclear power plant accident evolves slowly and releases of radioactivity to the environment occur hours or even days after a general emergency is declared. Therefore, the doses illustrated in Figure 1.4a (25,000 people exposed to 0.01–0.05 sievert [Sv] [or 1–5 rem]) over a 4-day period will likely be doses that are avoided because of protective actions such as evacuations. Similarly, although the agricultural impacts are expected to be large (see Figure 1.4b), protective actions such as embargoes of food and pasture can prevent the dose from affecting members of the public.
This lesser impact from fallout is because the fireball does not reach the ground.
4 The San Onofre Nuclear Generating Station is a nuclear power plant located south of Saint Clemente, California, that is currently being decommissioned, but for the purposes of this illustration it is assumed to be operating.
- A radiological dispersal device (RDD) in New York City. The detonation of a device could result in fragmentation (see Figure 1.5a) or aerosolization (see Figure 1.5b) of the radioactive material and the dose impacts will differ depending on the type of the RDD. For a fragmentation RDD, a large fraction of the radioactive material in the device disperses as large particles (see the red dots in Figure 1.5a) that are deposited in the vicinity of the detonation. Exposure rates near fragments could be greater than 100 mGy per hour (or 10 roentgen [R] per hour) and all of them combined can create a larger hot zone where the exposure rates are around 0.1 mGy per hour (or 10 mR per hour). An aerosol RDD deposits radioactive material both in the vicinity of the explosion and possibly over a long distance of a few kilometers down wind, but because the concentration of the radioactive material is very low, the dose rates affecting people are low.
- An RDD detonation is likely to occur in highly populated areas with the intent to cause disruption and panic, and therefore could affect a rather large number of people (approximately 50,000). However, with the possible exceptions of fragments becoming embedded in a person’s body, the doses to members of the public are expected to be small. Dr. Musolino said that an RDD in New York City will be detected rapidly because every firehouse and thousands of police officers are equipped with radiation detectors and thus response to the radiological incident can start within minutes. To the contrary, in other cities in the United States, responses will likely take longer depending on local resources.
Dr. John Till (Risk Assessment Corporation) said that radiation dose reconstruction is a fundamental step in assessing the impacts of nuclear and radiological incidents and the associated need for long-term health
monitoring of the affected populations. Information derived from dose reconstruction includes
- Level of exposure of the affected populations
- Pathways of immediate exposure and immediate dose mitigation strategies
- Specific organs exposed and the risk of disease
- Potential pathways of long-term exposure and long-term mitigation strategies
- Feasibility of biodosimetry
He made a distinction between population-based dose reconstruction and individual dose assessment.
Population-Based Dose Reconstruction
Since the 1980s, dose reconstruction has been applied to studying large populations exposed to nuclear weapons fallout (Till et al., 1995, 2018) and later to populations exposed to nuclear accidents. Dr. Till said that each of these dose reconstruction efforts was unique in terms of the source term (quantity of radionuclides released to the environment and the chemical and physical form), the environmental transport of radionuclides, the scenarios of exposure, and the resulting estimated doses and uncertainties (Till et al., 2014).
He added that gathering the data for dose reconstruction is challenging and time consuming. Every dose reconstruction has information gaps due to incomplete, insufficient, or undocumented data, or due to data accessibility issues. As a result, dose reconstruction experts have to use mathematical modeling to fill in the data gaps and face the challenge of communicating the resulting uncertainties in the doses assigned to the populations.
Individual Dose Assessment
Dr. David Brenner (Columbia University) talked about individual dose assessment through biodosimetry. He defined biodosimetry as the use of radiation-induced biomarkers in blood, urine, or other accessible tissues to assess personal radiation exposure. He explained that in addition to generating individual dose estimates, perhaps the biggest advantage of biodosimetry is that it takes into account an individual’s biological response to radiation and therefore can identify those exposed individuals who are radiation-sensitive and presumably in need of a higher level of medical intervention.
The oldest and most studied biodosimetric approach measures DNA damage (e.g., chromosome aberrations or micronuclei) that can then be related to the delivered radiation dose. Until recently, this type of assay was only performed manually, typically in cytogenetic laboratories. According to Drs. Brenner and Iddins, this manual approach would not be suitable to reconstruct doses of a large number of survivors from a large-scale radiological incident, such as an IND, because it is labor intensive, at least in its standard manifestation. In addition, it has a limited dose range where it is practical for large-scale use, typically 500 mGy–5 Gy.
Although there are a number of cytogenetic laboratories around the world that could jointly provide biodosimetric services following a nuclear or radiological incident, Dr. Brenner estimated that the overall capacity using this approach would still be less than 10,000 samples per month, and the logistics of transferring the samples are challenging.
The Biomedical Advanced Research and Development Authority and the National Institute of Allergy and Infectious Diseases conduct and support research in biodosimetry. For example, researchers at Columbia University, with support from these two agencies, developed a completely automated, ultra-high throughput biodosimetric platform called RABiT (Rapid Automated Biodosimetry Tool), which fully automates both sample preparation and image analysis. The RABiT automates two mature, but currently manual, biodosimetry assays (micronucleus and dicentrics). A single RABiT machine can estimate whole-body, partial-body, or neutron doses of 1–10 Gy with a throughput of more than 6,000 samples per day (Garty et al., 2016).
Information on other biodosimetric tools that were not discussed at the workshop can be found at the Radiation Emergency Medical Management webpage at https://www.remm.nlm.gov/biodosimetry_refs.htm.