IntroductionThis chapter is concerned with management of populations exposed to low level radiation. The clinical management of significant exposure and injury due to radiation is discussed in other chapters. In a radiological emergency, the population is likely to be divided into categories of varying risk of suffering harm. These include:
- People close to a source of radioactive material and/or the site of a radiological/nuclear emergency who are at highest risk. These people may require radiation protection measures, such as shelter and evacuation, and medical treatment , if there is significant irradiation or contamination.
- People who are exposed to measurable amounts of radiation, but the exposure is likely to cause very low and/or unquantifiable risks to health in the short to medium term.
- People with no significant exposure to radiation from the emergency, but whose behaviour is adversely affected by their perception of the event, the risk to themselves or loved-ones, or other psychological factors amenable to management by effective communication.
The management of radiation protection and medical treatment for people in the highest risk (a) category is conducted by appropriate medical and scientific specialists. Public health may be important in these operations, as, for example, they may need to ensure adequate safe food, sanitation and medical services to evacuation centres, but does not generally form part of the management of the incident itself.
In lower risk populations (b and c), not at immediate risk of adverse health effects, public health agencies have an important role to play in managing a radiation emergency. This is because:
- The public perception of radiation hazards, combined with the lack of definitive information which may occur in the early stages of managing a radiation emergency, can engender significant anxiety in the wider population.
- The degree of exposure of people to radioactive material may not be known, such as if radioactive material is dispersed in the atmosphere, water or food.
- There may be a need to prepare the general population to move away from areas of risk if an emergency worsens without causing undue alarm or mass ‘self-evacuation’
The role of public health agencies in managing population response to lower levels of radiological riskThe issue in managing public behaviour in an emergency is rarely panic per se. Panic involves ‘irrational, groundless or hysterical flight that is carried out with a complete disregard for others’2. What is more often observed in emergencies is a response to fear, which is rational from the perspective of a person with an incomplete understanding of a situation and/or the belief that their actions are the way to control a threat to their safety. Providing information about the scale of a threat and measures necessary to remain safe can alleviate a lot of what appears to be irrationally motivated behaviour.
Radiation can be accurately detected in minute amounts, allowing for a precise assessment of the physical risk posed to the population. The risk which public health agencies must manage in groups 2 and 3, however, is often ‘distorted’ by psychological factors which include:
- The risk from a radiation emergency is involuntary. People will tolerate more risk when it is adopted by choice, such as using mobile phones while driving.
- The risk from radiation is not under personal control. People will tolerate risks when they feel they can do something to reduce its impact, such as wearing a mask in an influenza outbreak.
- Radiation is unfamiliar and produced by technology that few people understand. This increases people’s perception of the likely danger compared to risks which they understand, such as the risk of physical injury from a fire.
- Radiation causes dread diseases. Cancer and birth-defects are both associated with radiation exposure and are diseases which inspire a high degree of fear. As was observed in the 2009 pandemic, people worry less about a high risk of developing a minor illness.
- Fairness. People will tolerate risks if they perceive they benefit from the activity. This may not be the case where a radiation emergency involves an industrial or military facility.
- Morality. There are many people concerned about pollution in general, whose perception of risk from a radiological emergency is coloured by their views on the morality of the nuclear or other industry.
- Trust: There may be a low level of trust for public authorities, standards and ‘experts’ in communicating risk. This is in the context of trusted networks of friends, media, popular wisdom, and other sources of information about radiation.
- Diffusion in time and space. Risks which kill people ‘anonymously’ by being dispersed throughout the community and occurring at random intervals, such as household falls, engender less concern than those which are localised to a particular incident. A small risk from a radiological emergency with identifiable ‘victims’ localised to one area is less tolerable.
Adapted from Peter Sandman, Risk Communication: Facing Public Outrage, US EPA Journal November 1987.
- Risk communication to the public and other significant stakeholders of the risk poses by exposure to radioactive material in the environment. This can be done by a wide range of agencies, but public health agencies usually have established links with local doctors, schools, and government departments and experience in communicating risk from environmental/communicable disease hazards.
- Surveillance or case-finding to identify people exposed to significant amounts of radiation, who may need medical treatment or an assessment of long-term health risks from exposure. Surveillance and case-finding are routine aspects of the response to communicable disease and food poisoning outbreaks and can be modified to manage environmental hazards.
- Involvement in the development and implementation of evacuation plans from areas of risk. Moving large numbers of people requires planning to avoid public health risks.
Risk communication to the public and stakeholdersPublic health authorities should be tasked with developing communication for any radiological emergency which involves the release of radioactive material into the environment. This recognises the likelihood that the population whose risk perception needs to be managed is far larger the population that is likely to be exposed to acutely dangerous levels of radiation.
Key messagesPublic health agencies should anticipate needing to provide public and media information on, at least, the following information immediately a release of radioactive material into the environment is confirmed:
- What is the risk to the health of the population from exposure to radiation?
Where radiation exposure is very low, it can be useful to compare it to relatively innocuous activities like international flight or medical procedures such as chest x-rays. A comparison of radiation environmental exposures with other ‘safe’ radiation exposures has its limits, however, because it relies on the public perception of the safety of medical radiation. The peak radiation levels in Tokyo in March 2011 were about 0.3-0.5 ÁSv/hr, which is a very low risk to human health but is equivalent to a chest x-ray every two days to one week (20-100 ÁSv), which is not reassuring to everyone. A CT sounds like an innocuous comparator but, at up to 10mSv exposure, it is associated with a 1/2000 increase in lifetime risk of cancer, which is less reassuring3.
For this reason, it can be useful to provide comparisons of the health impacts of probabilities as well as the doses associated. For example:
Table 6.3 Risk comparison
Some comparative risks to a radiation exposure of 1 millisievert (mSv) (Risk of death 1 in 20,000)
- Lifetime risk of death by eating 2000 tablespoons of peanut butter
- Lifetime risk of death by eating 5000 charcoal barbecued steaks
- Lifetime risk of death by eating 1000 extra calories for an overweight person
- Lifetime risk of death by living 100 days in New York*
- Lifetime risk of death by smoking 75 cigarettes
- Annual risk of death from an accident at home
- Risk of death travelling a distance of 5000 km in a car in NSW*
- Risk of a car crash when travelling a distance of 60 km in a car in NSW*
* Suggested best comparatorFrom Northern Central Sydney Area Health Service Radiation Safety Council research guide 2006top of pageThis is useful because the objectively tiny increase in the risk of developing cancer from being exposed to 0.35 ÁSv per hour for 30 days, for example, can be compared to a range of events which many people perceive as rare but generally accept without great concern.
- Is it dangerous to eat produce/drink water?
It must be positively established early in a radiological emergency whether radioactive material is present in water or food, as discovering this later can fatally undermine trust in the management of a radiological emergency. If there is no contamination of food or water, then the issue of public communications is simple. If, however, there is a low level of contamination then it is important that the degree of risk to health this poses is immediately put into context.
Authorities are likely to measure and report the total amount of radioactivity in bulk food or water in Becquerels. This unit can be problematic because 1 Becquerel is a very small unit of radioactivity and so even low levels of contamination produce ‘big’ numbers. A measure in Becquerels also has no direct relationship to absorbed dose, or the human health impact of ingesting food or water, and so is confusing in the context of other units such as microsieverts. Public health agencies may find it useful to request a radiation physicist calculate an absorbed dose from the expected elements present in food or water for a given amount of food or water ingested to equal the normal background level of radiation.
It is also important to convert the total activity in food and water into an assessment of the health impact of ingesting this material, because radioactivity may be reported in terms of the amount it exceeds ‘normal’. As there is no ‘normal’ amount of many radioactive substances in the environment, the emissions limits for a nuclear power station, the limit of detection for radioactivity or the ‘action limit’ for investigation of a source of radioactivity are likely to be taken as a ‘proxy’ figures. These are set at a precautionary level, which is many times lower than the level of radiation that has a measurable health impact, but may lead to contamination being reported by authorities or the press as ‘x thousand’ times normal. This can cause unnecessary concern.
- What can I do to avoid radiation exposure?
The public may not be aware that substantial buildings, such as brick houses, offer 2 to 10-fold reduction in the absorption of radiation, and that basement car-parks can have much higher levels of protection. Simple advice about minimising unnecessary travel outdoors, closing windows and air-conditioning to reduce radiation exposure to As Low As Reasonably Achievable (ALARA) can be useful in providing people with measures they can undertake themselves, even if the underlying health risk is very low.
If there is an airborne distribution of material in a radiological emergency, then public health advice should be provided on issues such as water-tanks and home-grown food. The public health agencies in most jurisdictions have generic advice for the management of home water collection and washing of home-grown food after bushfires or chemical fires, which can be adapted for use in areas under a potential plume of radioactive material. It should be pointed out that filtering, boiling or adding decontamination tablets to water may not reduce levels of radiation.
People in any area where there is contamination from detectable amounts of radioactive material from a radiation emergency should be provided simple advice on what they can do if an emergency worsens. This is likely to be fairly simple advice about sheltering, providing water and related matters, but it is important to avoid an information vacuum of how to respond in the context of potentially inflammatory media reporting of an unstable emergency becoming worse.
- What are the risks to pregnant women/unborn children/breast-feeding women?
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Some radioactive substances, such as Iodine-131, can accumulate in breast milk if ingested during lactation, particularly soon after birth. Given that the overall dose to a mother is likely to be very small, this will probably be a negligible increase in absolute exposure to breast-feeding children.
Table 6.2 Transfer of radionuclides to breast milk following intakes during pregnancy or lactation
|Radionuclide||Transfer to milk as per cent reaching blood, for intake in:|
|Transfer to milk as per cent reaching blood, for intake in:|
|Transfer to milk as per cent reaching blood, for intake in:|
1 Intake at 5 weeks post-conception
2 Intake at 35 weeks post-conception (3 weeks prior to birth)
3 Intake within 1st week after birth
4Figures in brackets for intakes during lactation are percentage ingested activity
From Harrison, JD, Smith, TJ, Phipps, AW, Infant doses from the transfer of radionuclides in mother’s milk, Radiation Protection Dosimetry, (105) 2003
Table 6.3 Comparison of doses following chronic maternal ingestion of radionuclides throughout pregnancy and lactation
|Radionuclide||Ratio of offspring : adult dose1|
|Ratio of offspring : adult dose1|
Infant, in milk3
1 Committed effective dose (environmental exposures)
2 Includes doses received in utero and from activity retained by the child at birth
3 Includes doses from activity transferred to milk as a result of maternal intakes during pregnancy and lactation
From Harrison, JD, Smith, TJ, Phipps, AW, Infant doses from the transfer of radionuclides in mother’s milk, Radiation Protection Dosimetry, (105) 2003
- Do I need iodine tablets?
The protective effect of KI in managing exposure to radioiodines is established, but significant exposure is required to justify the use of this drug. Unfortunately, public perceptions of KI as ‘radiation tablets’ may lead to confusion about circumstances when KI should be used. Public health messages need to clearly identify when the radionuclide is NOT a radioiodine with emphatic advice that KI is ineffective for management of these exposures.
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Adverse effects of KI include gastrointestinal disturbance (nausea, diarrhoea, and abdominal pain), transient hypothyroidism, skin reactions or allergic reactions. While these are generally mild, widespread inappropriate use of KI on a population level can cause significant harm. KI should not be provided to populations at low (or no) risk of exceeding the amount of radiation from radioiodines necessary for protection against thyroid cancer, particularly not on a precautionary ‘just in case’ basis or for psychological reassurance.
- Are people or things which have been near a radiological emergency safe?
Advice about food or water from the vicinity of a radiation emergency should be based on monitoring and control of the distribution of contaminated material. General advice about what to do with material which has come from an area of low radiation risk, such as cars driven by evacuees, clothes and so forth, should be provided.
People from the affected area, who have been effectively decontaminated (which in vast majority of cases just required removal of clothing and showering), are not a radiation risk.
Coordination of communicationsIn an incident affecting Australia, there are three levels of government and, potentially, several portfolios at both the Commonwealth and state level that will have ‘ownership’ of the issue. Media interest and pressure to provide commentary is likely to be intense.
In this environment, public health messages should be:
- applicable to a local area, given its distance from an incident, weather, water and food supply
- presented in a manner that allows people to make contact to seek further information about health concerns
SurveillancePublic health agencies usually monitor or undertake infectious disease and environmental health surveillance for state health departments. Surveillance, or case-finding, can also be used to identify people exposed to significant amounts of radiation. In a radiological emergency, information should be provided on how to recognise injury caused by exposure to radiation in two distinct circumstances:
- To provide medical practitioners and the public information on the signs and symptoms of radiation injury so that they exclude this as a diagnosis and counsel concerned patients. This is the most likely use of this information and it is important to avoid the ‘worried well’ presenting in large numbers for medical assessment with perceived symptoms of radiation injury.
- To find people in a population, who may have been exposed to significant quantities of radiation from a lost/covert source of radiation, such as a source concealed in a public place. In this case, it is necessary to communicate to doctors and the public a case-definition of early radiation sickness and advice on where people should go for further assessment.
Surveillance of ‘ambient’ radiation levelsPart of the anxiety provoked by radiation is that it is invisible to the senses. Monitoring of ambient radiation levels in areas with low levels of risk of contamination can provide reassurance to the public that radiation is not present. During the 2011 Fukushima reactor incident, Japanese public health authorities provided real-time web-based information on levels of radiation detected in urban centres. Apart from being very useful to medical and other professionals advising people in these areas, these readings provided a transparent and real-time source of information that members of the public could access themselves and use to plan their activities.
Daily radiation monitoring could potentially be arranged through radiation physics departments at hospitals, academic institutions, companies specialising in the remediation of environmental health issues, or government reference laboratories. In the absence of an established process, the ability to provide survey meters to staff to quantify low or absent levels of radiation can be useful. This should obviously not replace specialist assessment of radiation present in the environment when, and if, significant contamination by radioactive material occurs.
Development and implementation of evacuation plansEvacuation of areas where people receive high doses of radiation (approximately >1mSv/hr5) is a fundamental part of the repertoire of responses to a radiological emergency. While the decision whether people need to evacuate an area would rest with expert advisory groups with experience in radiation safety, managing the evacuation of large populations raises many public health issues.
The aim of an evacuation process is to reduce the overall hazards to human health, but evacuation of large numbers of people is itself hazardous. In 2005, Hurricane Rita was responsible for 111 deaths in the Texas gulf; 3 of these were from wind-blown trees and 108 were attributable to complications of evacuation, such as hyperthermia, dehydration, decompensation of chronic health conditions and vehicle accidents6
This balance is particularly important in radiological emergencies because the public perception of the risks associated with radiation may be disproportionately high compared to the actual risks from a mass evacuation. There may also be the perception that evacuation from areas of low risk is the only way of reducing exposure to radiation.
To address the potential public health impacts of an evacuation plan, public health agencies should prepare information relevant to people in their area which details:
- When should people evacuate?
If evacuation is a possibility, then the signal which indicates people should evacuate also needs to be clear to people in the community. The use of emergency messaging systems specified jurisdictional emergency plans, such as radio, television, SMS or sirens, should be planned in advance. Ad hoc communication from non-local authorities should not replace standard emergency warning systems.
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- How to evacuate
In this context, public health agencies should work with emergency planners to effectively communicate the degree of the immediate threat to human health a change in weather, plume direction, or severity of a radiological emergency presents. If a town is threatened by a change in the direction of a plume carrying material from a radiological emergency, for example, then peak levels of radioactivity are likely to be transient. Levels of radiation at which people might be advised to move, such as 40 ÁSv/hr8, will still take several weeks of unshielded exposure to exceed a maximum yearly radiation worker exposure standard of 20 mSv. In these situations, advice to shelter in place and evacuate in due course, rather than evacuating ahead of a particular storm or weather change, can potentially reduce some of the hazards of mass evacuation.
- Where to evacuate
The movement of people with chronic diseases, who are technology dependent or who have impaired mobility poses particular challenges. Evacuation centres with high radiation shielding qualities can be implemented in buildings with basement levels and may be better than transporting vulnerable people even if the wider population does evacuate. In setting up evacuation centres, public health agencies should provide advice on sanitation, food preparation, water supply and the provision of medical care. A system of tracking the arrival of people in evacuation centres is essential.
- What to do if you do not evacuate
In either case, providing information, which empowers an individual to take protective action, can avoid a poor outcome from self-evacuation or poorly planned sheltering. This includes how to identify areas of a house or building that provides optimal shielding, how to prepare water and food supplies to avoid contamination by rain or particulates, and activities to avoid. With the exception of not having to actively defend a house against a radiation plume, many of these messages are similar to those required in bushfires, floods, storms and other environmental emergencies managed under jurisdictional emergency plans which include public health input.
Advice may be given to people on the basis of being in a ‘zone’ at a distance from a source of radiation. Zones for immediate evacuation (precautionary action zone) or protective action (urgent protective action zone) are designated ahead of time around US nuclear facilities9 and visiting nuclear-powered warships, and similar zones were declared at 20km and 80km around the Fukushima reactor after the 2011 tsunami. These involve giving people the advice described above based on their location rather than a specific ‘signal’ to evacuate or take action.
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In establishing a response based on response zones, care should be taken to communicate:
- Why the zone is being established; is it precautionary, based on measured exposure, or a zone in which people should be prepared to take further action?
- How the zone affects movement; are people in the zone to leave and can people enter?
- What is the advice for people outside a zone; it is difficult to convince people on the margin of a zone that their risk falls to zero. This is particularly so if there are highly visible protective measures being taken (monitors, distribution of printed material, increased presence of emergency services) in close proximity to an area nominally outside a risk zone.
The naming of zones can assist in communicating its intent to the public. If people in the zone do not have to leave but people outside are to avoid entering unnecessarily, then the term ‘evacuation zone’ is unhelpful. Similarly, if residents are being asked to confine themselves to essential travel into an area but otherwise shelter in place within it then the term ‘exclusion zone’ is misleading10. It can be assumed the media will choose the most alarmist or confusing names, such as ‘no-go zone’, ‘death zone’ and ‘disaster zone’ with reference to the 20km and 80km zones around the Fukushima site. Comparatively bland names such as the “Precautionary Zone” or “Protective Action Zone” may be preferable if they are used consistently in communications and explained.
1. G. Blalock et al, Driving Fatalities After 9/11: A Hidden Cost of Terrorism, Applied Economics, 2009 (Vol. 41, Issue 14).
2. Auf de Heide, E, Common Misconceptions about Disasters: Panic, the “Disaster Syndrome,” and Looting, chapter 27 of The First 72 Hours: A Community Approach to Disaster Preparedness, M O’Leary (ed), published iUniverse 2007
3. US Food and Drug Authority, “What are radiation risks from CT?”
4. California Emergency Management Agency, press release, 17 March 2011
5. ARPANSA Radiation Protection Series Number 7
6. Zacharia, A, Patel, B, Deaths related to hurricane Rita and mass evacuation, Chest, 2006 Slide Presentations.
7. Litman, TA, Lessons From Katrina and Rita: What Major Disasters Can Teach Transportation Planners,” Journal of Transportation Engineering, 132 (2006)
8. ARPANSA Radiation Protection Series 7 p33; Recommends temporary resettlement at a dose of 30mSv in the first month, which equates to 42 uSv/hr.
9.ARPANSA Radiation Protection Series 7, p18
10. “The fire forced the closure of several schools as authorities this morning enforced a 10-kilometre exclusion zone around the factory”, “Huge Canberra Blaze Now Under Control”, Sydney Morning Herald, September 16 2011.