Radionuclides

A wide range of radionuclides can be released to the environment from the scenarios listed in Table 1. These include both short- and long-lived radionuclides, and a range of alpha, beta and gamma hazards and, in certain scenarios and conditions (e.g., a criticality accident), neutron hazards. Radionuclides can be released singly or as a mixture, depending on the type of scenario. Typically, accidents involving criticalities, operating faults, and explosions at nuclear facilities and malicious use of nuclear weapons involve the release of a range of fission products (e.g., isotopes of cesium, iodine, and strontium), noble gases (xenon, krypton), and activation products (e.g., isotopes of iron, zinc, and manganese). Scenarios involving single radionuclides from medical or industrial settings tend to be beta/gamma emitting sources, such as ⁶⁰Co, ⁹⁹Tc, ¹³¹I, ¹³⁷Cs, ¹⁹²Ir, and ²⁴¹Am. These sources are also the most likely to be used with malicious intent in a RDD or RED scenario. However, as the Litvinenko ²¹⁰Po poisoning case in the UK indicated, any available radionuclide can be used with malicious intent to contaminate food and drinking water supplies.

Duration of response and recovery phases

The duration of different phases is driven by the size and complexity of the radiation emergency. For a criticality accident, such as the one at Tokai Mura, Japan in 1999, the response phase may only last a few days. In contrast, damage to a radioactive source like what happened at Goiania, Brazil in 1987, can lead to a response phase of several months. Similarly, the recovery phase for small scale emergencies or those involving short-lived radionuclides (e.g., Windscale Fire, UK in 1957), may be of short duration, lasting a few months, while for large accidents, malicious events or military acts during armed conflict, involving long-lived isotopes, the recovery phase may extend over several years to decades (e.g., atomic bombings in Japan in 1945, Kyshtym explosion in former USSR in 1957, or Palomares accident in Spain in 1966).

Dose criteria and other derived criteria

For the protection of people in emergency and existing exposure situations, ICRP Publication 146 ³ recommends using reference levels, expressed in terms of individual effective dose (mSv), to restrain inequity in the distribution of exposures and to maintain or reduce all exposures to as low as reasonably achievable. ICRP notes that the use of effective dose is primarily aimed for planning purposes and to support preventing and mitigating stochastic health effects. Whilst this can be useful for large scale releases involving whole body immersions in a plume (e.g., the Three Mile Island accident in USA in 1979), it may be less appropriate for malicious events or smaller scale accidents where the exposures may be localized to a specific area of the human body (e.g., RED, ²¹⁰Po poisoning of Litvinenko in the UK in 2006, and the orphaned source accident in Chile in 2005). Given the range of situations that may be encountered, the TG is also considering developing additional situation specific criteria expressed in terms of absorbed dose (including RBE-weighted absorbed dose) to protect against severe tissue effects or injuries.

Exposure pathways

Release of radionuclides during a radiation emergency can be to the atmosphere, to waterbodies, or to the ground. After release, radionuclides can be dispersed through the environment by wind, water flow, and other processes. Any humans present will be exposed to radiation emitted by those radionuclides via a number of exposure pathways that include inhalation of radionuclides in air; ingestion of radionuclides in dusts, water, or foods; direct deposition onto skin; and external irradiation from radionuclides present in air and soils and on surfaces of buildings, roads, and vegetation. Some types of radiation emergency, such as the Goiania accident, have the potential to involve all exposure pathways, whereas others may only affect 1 pathway. For example, deliberate emplacement of a RED leads to external exposures, whilst deliberate contamination of food and water supplies causes internal exposure following ingestion. In addition, scenarios such as a RDD may involve contamination of wounds with radioactive material.

Justification and optimization of protection

All decisions that aim to reduce the impact of exposure in the event of a radiation emergency inevitably introduce additional constraints on living and working in the affected areas, and these must be considered when justifying the decision and optimizing protection. Involvement of key stakeholders in these processes should be sought whenever possible, and regularly reassessed as the situation evolves. Protective actions should continue to do more good than harm in the broadest sense by balancing the level of residual exposure of the affected people against the societal, environmental, and economic effects, and mental health and psychosocial wellbeing. Protection is considered optimized when it has achieved the most reasonable outcome for all stakeholders and the magnitude of individual doses are as low as reasonably achievable.

Protective action(s)

Protective actions are taken during a radiation emergency to reduce or prevent exposures. The action can be to secure or remove the source, or to modify the location and habits of the exposed individuals. Some actions, such as sheltering in place, evacuation, and stable iodine, can be taken if there is a threat of a release (e.g., the Three Mile Island accident). In the immediate aftermath, urgent protective actions are to save life while preventing and mitigating severe tissue reactions and injuries that can result in long-term health effects, disability, and even the loss of life. Restricting access to highly contaminated areas and personal decontamination are effective in the early response phase and were implemented, for example, during the Birmingham hospital accident in the UK in 2018 and the Litvinenko poisoning in 2006.

Doses to people and effects

There are 2 broad categories of people that may be affected by radiation emergencies: members of the public and responders. Responders include for example emergency teams (e.g., firefighters, police officers, medical personnel, drivers, and crews of vehicles used for evacuation), workers who may or may not be considered as occupationally exposed, military support personnel, security services, care workers and social workers, and citizens who volunteer to help. ³ Radiation emergencies have the potential to expose responders and members of the public to a wide range of doses. Some of these doses may cause radiation-induced health effects, either by inducing tissue reactions at high levels of exposure or increasing long-term risk of cancer.

Effects: tissue reactions. Doses greater than a few Gy are likely to result in tissue/organ damage that is characterized by a threshold dose above which the severity increases with level of exposure. Threshold values vary according to the organ or tissue, to the effect considered, and to the type of radiation exposure (e.g., acute or protracted). Such damage may occur in the hours, days, or weeks after exposure (early tissue reaction), or after a much longer period of time that could extend from years to even decades (late tissue reactions). Early tissue reactions may result from high-dose external exposure or significant internal contamination. Such effects have been observed in past radiation accidents. For example, following the Tokai Mura criticality accident in 1999, 2 workers receiving absorbed doses of 16-20 Gy and 6-10 Gy (from neutrons and gamma rays) died some 83 and 194 days later, respectively, from Acute Radiation Syndrome.Reference Tanaka ⁵ Alexander Litvinenko, who was poisoned with ²¹⁰Po in 2006, died 22 days later as a result of widespread damage to the organs and tissues of the reticulo-endothelial system, including red bone marrow. The highest estimated doses to Litvinenko’s liver and kidneys were 92 Gy and 140 Gy, respectively, at the time of death.Reference Harrison, Fell and Leggett ⁶ Early tissue reactions may also arise from military action during armed conflict, for example, a nuclear detonation. Late (delayed) tissue reactions, such as non-healing wounds, hair loss, and radiation dermatitis may occur in the months or years following external exposure or internal contamination, acute or protracted. These effects were recorded after the bombing of Hiroshima.

Effects: stochastic. Cancer and heritable effects are characterized by an increase in the probability of occurrence proportional to the dose, while their severity is independent of the dose received. The risk of health effects associated with low-dose and low-dose-rate radiation exposure is very low, with some uncertainty about the exact risk to an individual. Based on the results of epidemiological studies, it is estimated that a dose of 100 mSv above the natural background level adds approximately 0.5% to the 25% lifetime risk of fatal cancer typically seen in populations worldwide. ² In addition to the early and late tissue reactions, the bombing of Hiroshima in 1945 also caused a surge in childhood leukaemia cases into the 1950s, and elevated rates of other types of cancer in the exposed population.

Doses to non-human biota and effects

Flora and fauna may be exposed to radiation in a similar way to humans, leading to DNA damage. Although there are broad similarities in radiation responses of different organisms, there are wide differences in their radiation sensitivity. As such, radiological induced effects to non-human biota have no universal “value” for causing tissue reactions. As an example, the lethal absorbed dose for different flora and fauna can vary by factors of 1000 to 10 000, with mammals being the most sensitive and viruses being among the most radiation resistant.

Scale and land use affected

The scale of radiation emergencies may range from an isolated occupational over-exposure of a single person (e.g., the Chile accident in 2005), to contamination of a single building (e.g., Harborview in 2019), to contamination of many buildings (e.g., the Goiania accident in 1987; the Litvinenko case in 2006), to contamination of large areas of agricultural land (the Windscale Fire in 1957; the Kyshtym accident in 1957), or extend to a major catastrophe with global dimensions (nuclear detonation). All types of land use may be affected, resulting in widescale food and drinking water restrictions, and destruction of critical infrastructure. The scale of contamination affects the resources required for remediation and decontamination and ultimately the management of large volumes of waste.

Psychosocial consequences

Lessons learned from previous nuclear accidents have demonstrated that the long-term mental health and psychosocial consequences can outweigh the more immediate and direct physical health impacts of radiation exposure and can persist for years if not adequately addressed. ⁷ Fear and uncertainty about radiation risks, negative perceptions about protective actions, social stigma towards affected people, and misinformation can exacerbate people’s distress. This can result in substance abuse, domestic violence, anxiety, and post-traumatic stress disorder. Following the Goiania accident in 1987, thousands of people were impacted psychologically, especially as it happened a year after the Chernobyl accident. Some residents of Goiania were not allowed to register in hotels, to fly on planes, or to travel on buses. The mental health consequences of a malicious event are more severe than from a radiation accident, primarily due to the deliberate intent to cause harm, instill fear, and disrupt societal norms. Radiological terrorism creates a heightened sense of ongoing security threats and the potential for additional attacks. This sustained state of fear and uncertainty (in terms nature of the source and location) can contribute to chronic stress and anxiety among affected individuals and communities, made worse if there has been little or no emergency preparedness for such an event.

Societal and economic impacts

The sudden presence of radioactive contamination in the environment may upset the quality of life of affected communities. Some people will choose to stay in the affected area, when this is allowed, and others will leave. This can seriously affect community life and may impact economic activities in the affected area over the short and long terms. This can lead to the long-term depopulation of previously thriving regions due to a negative feedback loop of poor economic conditions and lack of infrastructure, especially medical care.Reference Schneider, Lochard and Maître ⁸ Residents of Goiania, for example, suffered significant economic and social stigma that lasted for an extended period. The impact on food production and manufactured goods was felt beyond the contaminated area.

Stakeholder engagement and risk communication

By engaging with all the relevant stakeholders, protection decisions should be more holistic, inclusive, and sustainable, provided that the process adopted is transparent and fair. Furthermore, early engagement, even prior to a radiation emergency, is key for building and shaping the subsequent communication strategy. ⁹ Different engagement processes are required according to circumstance, and different stakeholder groups can be reached through different channels to ensure that accessibility of the process is optimized (e.g., face to face meetings or online, social media or printed newsletters, technical or plain language). The level of engagement should be proportionate to the nature of the radiation protection issues and their context, ¹⁰ and to the level of perceived risk. Throughout the response to the Palomares accident and subsequent remediation, affected stakeholders (regional and local authorities, citizens, environmental groups, media etc.) were closely involved in decisions on the protective actions taken, and this was a fundamental to optimizing the strategy. This maintained confidence in the expert’s assessments and authorities’ recommendations.

Crisis communication for radiation emergencies should respond to the publics’ concerns and address potential uncertainties without triggering panic. The information provided should help affected individuals assess their own risks and motivate them to take appropriate protective actions. Prompt, clear, and accurate communication enhances trust in the responsible authorities. This can be strengthened by following the key principle of 1 message, many voices. ¹¹ The communication strategy at the time of the Litvinenko poisoning was open and transparent. The government agencies responsible for managing the response held regular press conferences, issued daily press statements, set up help lines for anyone affected, responded to thousands of media calls, and regularly updated their websites.Reference Rubin, Page and Morgan ¹² In contrast, the accident at Three Mile Island was heavily criticized due to communication failures that ultimately contributed to the public’s fears, confusion, and distrust, as indicated in the Report of the President’s Commission on the Accident at Three Mile Island (October 30, 1979).

The rapidly evolving social media landscape over the last few decades provides new challenges to public communication. It has the potential to provide benefits to radiation protection authorities by rapidly disseminating critical information to much larger audiences. In so doing, it can help establish trustworthiness of authorities and experts.Reference Eriksson ¹³ However, social media can also give rise to an increase in mis- and disinformation available online, resulting not only in uncertainty and an undermining of trust, but also in the adoption of incorrect protective actions. ¹⁴ The TG is currently developing recommendations on how best to use social media for a range of radiation scenarios, as no single message fits all. Clearly, a small-scale accident involving a known radionuclide at a nuclear facility would require a very different communication strategy from that for a large scale malicious event such as a dirty bomb or nuclear detonation in an urban area, where the radionuclides may initially be unknown.