Fears from Fukushima20 April 2013
A task group of the International Commission on Radiological Protection reported on radiological protection issues arising from the Fukushima disaster in October 2012. ICRP said that it is already taking action, but added that these issues and recommendations will continue to influence the ICRP programme of work for years to come.
While the people affected by the Fukushima accident were largely protected against radiation exposure and no one incurred a lethal dose of radiation (or a dose sufficiently large to cause radiation sickness), many radiological protection issues were raised. Some of the 18 issues identified as needing attention are outlined below.
Inferring radiation risks
The substantial biological, epidemiological, and ethical foundations supporting the basic notion of the nominal risk coefficients used for radiological protection purposes were misunderstood by the public at large in Japan, and the media unfortunately contributed to this misunderstanding. The concept of a dose and dose-rate effectiveness factor (DDREF) was notably not understood. Following a review of the biological and epidemiological information on the health risks attributable to ionising radiation, the new ICRP Recommendations reconfirm previous estimates of the combined detriment due to excess cancer and heritable effects, which remain unchanged at around 5% per sievert of effective dose.
Since the accident, hypothetical estimates of future casualties due to the accident have been made. They oscillated between some tens of cases in the peer reviewed literature to half a million in reports by the media. These alarmist and unfounded theoretical calculations have caused severe emotional distress in the Japanese population. The epistemological limitations of the sciences of radiobiology and radioepidemiology, and their influence on the attribution of health effects to low-dose exposure situations are often ignored. Notwithstanding, it may be necessary for decision-making bodies to ascribe nominal radiation risks to prospective exposure situations and impose radiological protection measures even at low doses, in part for reasons of social duty, responsibility, utility, prudence and precaution.
Quantifying radiation exposure
In the aftermath of the accident, the quantities and units used for quantifying radiation exposure of individuals in terms of radiation doses have caused considerable communication problems. These include the following:
- The differences between the quantities have not been well explained and are not well understood even by educated audiences
- The distinction between the quantities used in the radiological protection system and the operational quantities used for radiation measurement is even more difficult to understand in part due to semantic problems
- The use of the same unit for the quantities equivalent dose of an organ and effective dose without always specifying which quantity is used has enhanced confusion further
- There is very little understanding for why there are so many different quantities used in radiation protection, not only many dosimetric quantities but also many radiometric quantities (such as activity and activity concentration).
There are great difficulties to communicate radiological information to non-experts and the public at large using the ICRP system and its quantities. This is a consequence of the rather intricate concept behind the system of quantities which uses more than one quantity -- organ (equivalent) doses and whole body (effective) dose -- and combines physical exposure data with scientific data on radiation risk for organs and tissues. In other words, the system and the quantities have shown to be well-suited for operational radiation protection but they are much less suited for communication with non-experts, particularly in emergency situations.
A strict and consequent application of a simplified dose reporting (for example, organ dose, effective dose) could help to improve the situation in cases of emergencies.
Managing emergency crises
In sum, those handling the crisis have difficulties with the application of the international guidance available for managing the emergency exposure situation. There were problems associated with the protracted period of release and with extending emergency planning zones (this issue is important during the emergency response phase but it may not be a matter of the principle of radiological protection but rather of regulatory policy). Prioritizing emergency protective measures was another issue of concern. Many specific issues for crisis management following a serious accident need to be addressed more clearly, including: the management of the unique emergency exposure situation created by the prolonged (rather than acute) release from the accident; the consequent need of extendibility of the emergency planning zones and of prioritization of emergency protective measures; and, finally and significantly, the lifting of emergency protective measures and the transit from the emergency exposure situation to an existing exposure situation.
The adequacy of the occupational radiological protection recommendations for workers who are not customary 'radiation' workers, such as firefighters and volunteers, has been questioned.
A number of medical management issues arose in the aftermath of the accident. These included the following:
- Problems related to an accident as a combined disaster
- Questions about personnel involved in emergency medicine
- Dealing with people's contamination, including the selection of a screening level for contamination and the consequences of the removal of clothing
- The role of health physics experts for radiation safety during emergencies
- The appropriate model of core curriculum in medical schools
- Risk communication
- Medical preparedness, including drills and exercises.
Justifying disruptive actions
Like in other similar situations, some of the decisions taken after the accident in order to protect the public were extremely disruptive and caused significant social harm. For instance, evacuating people from their homes is a measure that it is prone to cause serious disturbance to normal public life. Questions have arisen on whether some of these measures are justified, in the sense that they really produce more good than harm.
Applying justification in an emergency situation such as that triggered by the accident is particularly difficult. For instance, decisions on whether or not to evacuate people from areas of elevated but not high doses can present difficult dilemmas. If people remain they will incur some radiation doses and increase their plausibility of radiation-induced harm in the future; if they are evacuated such a plausibility will disappear but they will certainly incur the actual detriments associated to the evacuation itself.
A recently-published report by Japan's Reconstruction Agency indicates that the stresses of personal involvement in the evacuation, management and clean-up related to the Fukushima nuclear accident have emerged as the biggest factors in ill health for Japanese people.
The accident has reconfirmed that psychological consequences are a major outcome from major radiation accidents. While they are health effects in their own right, they are basically ignored in radiological protection recommendations and standards. Advance planning for emergencies should recognise the necessity for dealing with psychological consequences and the concerns that may be engendered for decades following an accident.
Rehabilitating evacuated areas
A clear lesson from the Chernobyl accident was that it was, and continues to be, extremely difficult to rehabilitate an area evacuated as a result of a nuclear accident. A similar situation is occurring in the areas of the Fukushima prefecture that were evacuated due to the accident. However, it is expected that those regions may be rehabilitated in the not-too-distant future. At that time, people (including part of the relocated population) may want to move into the region despite the fact that the exposure might still be somewhat elevated. Questions arising in this case are: what is the category of the exposure situation, what is the type of exposure, and consequently how should the exposure be controlled? While the ICRP Recommendations are not explicit on how to handle this type of situation, it might be considered implicit that returning from a temporary evacuation leads to an existing exposure situation.
Dealing with contamination
The fallout of some of the releases from the accident has deposited radioactive substances over large territories. The issues for the authorities are whether these territories are 'contaminated' and whether they have to be 'remediated' in order to allow their habitation. It seems therefore that there is a strong connection between the misunderstandings of the concepts of 'contamination', 'remediation' and 'habitability'. For anxious members of the general public, the issue can be summarized in this simple question: Is it safe for my family and I to live in this territory?
It is expected that, following significant releases of radioactive substances into the environment, products used or consumed by the public, such as foodstuffs, water and non-edible consumer products, may present slightly elevated levels of radioactive substances attributable to the accident. While natural radionuclides are present in consumer products because of natural processes, the inclusion of artificial radionuclides following accidents is a serious issue because it is perceived as the more pervasive process of incorporation of radioactivity. Its regulation has been controversial and not straightforward. In fact, the control of these consumer products is one of the main unresolved issues of practical radiological protection. It has created (and continues to create) many problems for Japan in general and for the Fukushima region in particular.
In sum, the international regulation of consumer products containing radioactive substances is bizarre and it is not surprising that it is causing so much confusion in the Japanese public and authorities alike.
Radiation exposure to radionuclides incorporated into the body has been a source of debate among the public and the media and also in some scientific circles in Japan. For a given (organ or effective) dose, internal exposures appear to be perceived as more dangerous than the same exposure from external sources. There is compelling scientific evidence that radiation risk depends on the amount of dose received, and not on whether that dose is delivered from outside or inside the body, but this is largely ignored by the media and the public.
Restricting non-worker doses
As the accident released large amounts of radioactive materials into the human habitat, the issue on how to restrict doses to members of the public became crucial. In terms of radiological protection the evacuation and food restrictions that were adopted at the time by the authorities effectively reduced the dose received by people living in the affected area. In selecting the reference levels in some areas under a de facto emergency exposure situation, the authorities tried to follow the situation-based approach recommended by ICRP. In deriving the criteria, the regulatory authority selected a reference level of 20 mSv/y, while the dose limit for planned exposure situations was (and continues to be) 1 mSv/y.
However, people living in the affected areas were confused by the logic behind the restrictions applied to individual doses, in what was perceived as a mixture of the pre-emergency, emergency and post-emergency protection policies.
Also, there seems to be considerable discrepancy in understanding the dose value of 1 mSv/y. The general public and society at large tend to regard a dose above this value dangerous and consequently this creates a lot of complications in coping with radiological events.
Children and pregnant women
Recommendations specifically dedicated to the protection of children and infants are not available. The relatively small difference between the detriment-adjusted nominal risk coefficient for the population as a whole, which includes children, and those for the adult population, that is around 30%, merits at least further consideration, particularly taking into account that new data on radiation risks of children have been recently reported.
Affording proper protection to foetuses and embryos has been controversial and unclear, even at the level of the medical profession.
Monitoring public protection
Two main issues on monitoring the protection of the public have arisen in the aftermath of the accident:
- What should be the general policy of environmental monitoring after an accident
- Why members of the public are not individually monitored while workers receive that benefit.
Mistakes in communicating radiation risk and protection measures to members of the public and the media have been made during previous accidents and were repeated in this accident.
This article is an edited version of the report of ICRP Task Group 84, led by ICRP vice-chair Abel González of Argentina's nuclear regulatory authority. The report, which does not necessarily present the views of the ICRP, was accepted by the ICRP main commission on 31 October 2012. A full copy is available via www.tinyurl.com/icrpfuku