3.1.The system of protective actions and other response actions in an emergency (see Table 1) includes numerical values of generic criteria as well as of the corresponding operational criteria that form the basis for decision making in an emergency.

TABLE. 1. System of Protective Actions and Other Response Actions in an Emergency

^a Generic criteria are established at levels of dose that are approaching the thresholds for severe deterministic effects.

^b Such actions include immediate medical examination, consultation and treatment as indicated, contamination control, decorporation where applicable, registration for long term health monitoring, and comprehensive psychological counselling.

^c Such actions include relocation and long term restriction of consumption of contaminated food.

^d Such actions include screening based on individual doses to specific organs, considering the need for registration for medical follow-up and counselling to allow informed decisions to be made in individual circumstances.

3.2.The following considerations form the basis of this system:

• The following possible outcomes should be considered during the planning and implementation of protective actions and other response actions in an emergency:

  • Development of severe deterministic effects¹1;

  • Increase in stochastic effects;

  • Adverse effects on the environment and property;

  • Other adverse effects (e.g. psychological effects, social disorder, economic disruption).

• The following types of exposure should be taken into account in the planning and implementation of protective actions and other response actions in an emergency:

  • The projected dose that could be prevented or reduced by means of precautionary urgent protective actions;

  • The dose that has been received, the detriment due to which may be minimized by, for example, medical actions, as required, and may be addressed by public reassurance or counselling.

• Precautionary urgent protective actions should be implemented before the event (on the basis of a substantial risk of a release or exposure) under any circumstances, in order to prevent the development of severe deterministic effects for very high levels of dose (generic criteria are presented in Table 2).

• If the risk of stochastic effects is the main concern and the risk of the development of severe deterministic effects is negligible, urgent and early protective actions and other response actions, all of which are justified and optimized, should be implemented to reduce the risk of stochastic effects (generic criteria are presented in Table 3).

• If the dose exceeds a particular generic criterion identified in Table 2 or 3, individuals should be provided with appropriate medical attention, including medical treatment²2, long term health monitoring and psychological counselling.

• For all levels of dose that may result in an emergency exposure situation, a plain language explanation of the risks should be provided to decision makers and the public to allow them to make informed decisions about what actions they will take.

3.3.Table 1 summarizes, for different types of possible health consequences of exposure, the basis for implementation of protective actions and other response actions. A summary of the dose concepts and the dosimetric quantities is provided in Appendix I.

3.4.The system of generic criteria and operational criteria is illustrated in Fig. 1. Generic criteria are provided in terms of dose that can be projected or dose that has already been received. The operational criteria³3 are values of measurable quantities or observables that include operational intervention levels (OILs), emergency action levels (EALs), specific observables and other indicators of conditions on the scene that should be used in decision making during an emergency. The operational criteria can be used immediately and directly to determine the need for appropriate protective actions and other response actions.

3.5.Generic criteria have been established on the basis of generic optimization in consideration of the range of conditions that prevail in an emergency. Generic criteria are established for urgent protective actions and early protective actions, as well as for other response actions that may be required in an emergency. Urgent protective actions (e.g. evacuation) should be taken promptly (e.g. within hours) to be effective, because their effectiveness will be reduced by delay [6]. Early protective actions should be implemented within days or weeks to be effective. They can be long lasting, even after the emergency (e.g. temporary relocation). In no case should urgent protective actions and early protective actions based on the generic criteria cause more detriment than they avert. Event specific conditions may warrant modification of the generic criteria.

3.6.The generic criteria replace the system of generic intervention levels (GILs) and generic action levels (GALs) that have been described in previous standards [6, 10]. This use of generic criteria meets the need for a common term for the system of values that would be used as the basis for the implementation of protective actions (e.g. evacuation or food replacement) and other response actions (e.g. medical follow-up).

3.7.A protection strategy, comprising specific protective actions and other response actions, should be developed. It should include, but should not be limited to, the following aspects:

• Generic criteria for implementing precautionary urgent protective actions to prevent severe deterministic effects should be established (see Table 2).

• A reference level should be set, typically an effective dose of between 20 and 100 mSv, expressed in terms of residual dose, which includes dose contributions via all exposure pathways. The protection strategy should be optimized to reduce exposures below the reference level.

• On the basis of the outcome of the optimization of the protection strategy, and by using the reference level, generic criteria for particular protective actions and other response actions, expressed in terms of projected dose or dose that has been received, should be developed. If the numerical values of the generic criteria are expected to be exceeded, those actions, either individually or in combination, should be implemented. Table 3 provides a set of generic criteria for use in the protection strategy that are compatible with reference levels within a range of 20–100 mSv, as well as further details for specific actions in different time frames. The implementation of protective actions and other response actions, given in Table 3, would prevent a significant amount of dose.

• Once the protection strategy has been optimized and a set of generic criteria has been developed, default triggers for initiating the different parts of an emergency response plan, primarily for the early phase, should be derived from the generic criteria. Default triggers, such as conditions on the scene, OILs and EALs, should be expressed in terms of parameters or observable conditions. Arrangements should be established in advance to revise these triggers, as appropriate, in an emergency exposure situation, with account taken of the prevailing conditions as they evolve.

3.8.Table 2 presents generic criteria (expressed in terms of the dose that is projected or dose that has been received) for taking precautionary urgent protective actions under any circumstances to prevent severe deterministic effects.

TABLE. 2. Generic Criteria for Acute Doses for Which Protective Actions and Others Response Actions Are Expected to Be Taken Under Any Circumstances to Avoid or To Minimize Severe Deterministic Effects

^a AD_{Red marrow} represents the average RBE weighted absorbed dose to internal tissues or organs (e.g. red marrow, lung, small intestine, gonads, thyroid) and to the lens of the eye from exposure in a uniform field of strongly penetrating radiation.

^b Dose delivered to 100 cm² at a depth of 0.5 cm under the body surface in tissue due to close contact with a radioactive source (e.g. source carried in the hand or pocket).

^c The dose is to the 100 cm² dermis (skin structures at a depth of 40 mg/cm² (or 0.4 mm) below the body surface).

^dAD(∆) is the RBE weighted absorbed dose delivered over the period of time ∆ by the intake (I₀₅) that will result in a severe deterministic effect in 5% of exposed individuals.

^e Different criteria are used to take account of the significant difference in the radionuclide specific intake threshold values for the radionuclides in these groups [3].

^f The generic criterion for decorporation is based on the projected dose without decorporation.Decorporation is the biological processes, facilitated by a chemical or biological agent, by which incorporated radionuclides are removed from the human body.

^g For the purposes of these generic criteria, ‘lung’ means the alveolar-interstitial region of the respiratory tract.

^h For this particular case, ∆` means the period of in utero development.

3.9.Table 3 provides a set of generic criteria expressed in terms of the dose that has been projected or the dose that has been received. The set of generic criteria expressed in terms of the projected dose is compatible with reference levels within a range of 20–100 mSv. Taking protective actions at this level of dose will allow the occurrence of all deterministic effects to be avoided and the risk of stochastic effects to be reduced to acceptable levels. If a protective action is implemented effectively, the majority of the projected dose can be averted. The concept of averted dose is therefore useful for the assessment of the efficiency of individual protective actions or their combination. The concept of averted dose represents an important component of the optimization of emergency response planning [15]. In the application of generic criteria for individual protective actions, the process of optimization of emergency response planning should be applied.

TABLE. 3. Generic Criteria for Protective Actions and Others Response Actions in Emergency Exposure Situations to Reduce the Risk of Stochastic Effects

Note: H_T — equivalent dose in an organ or tissue T; E — effective dose.

3.10.The generic criterion provided in Table 3 for iodine thyroid blocking is applied for an urgent protective action: (a) if exposure due to radioactive iodine is involved, (b) before or shortly after a release of radioactive iodine, and (c) within only a short period after the intake of radioactive iodine. Less disruptive protective actions such as sheltering could be implemented for lower doses.

3.11.In the absence of national guidance, the generic criteria presented in Tables 2 and 3 could be used as a basis for the development of criteria at the national level. If a reference level different from 20–100 mSv is chosen, appropriate scaling of the values of the generic criteria in Table 3 should be carried out, with account taken of the time frame (acute or annual) of the reference level. In exceptional circumstances, higher values of the generic criteria may be necessary.

3.12.Examples of when such higher values of generic criteria in exceptional circumstances may be warranted include cases in which replacement food or water is not available, cases of extreme weather conditions, natural disasters, the rapid progression of a situation and cases of malicious acts. Generic criteria used in such cases should not exceed those presented in Table 3 by a factor of more than 2–3.