Security Scanners

2. What are the current guidelines for radiation protection?

The SCENIHR opinion states:

3.2 System and Legislative Framework for Radiation Protection

3.2.1 ICRP System of Radiation Protection

The system of radiation protection that is used across Europe and worldwide is based on the recommendations of: the International Commission for Radiation Protection (ICRP); and the International Commission on Radiation Units and Measurements (ICRU). The conceptual framework adopted by the ICRP in its publication ICRP 60 (ICRP 1991) is one of a System of Radiological Protection and builds on the System of Dose Limitation central to earlier ICRP documents such as ICRP 26 (ICRP 1977). ICRP publication 60 (ICRP 1991) was substantially revised and updated in 2007 with the publication of ICRP 103 (ICRP 2007).

The ICRP system of radiation protection is based on three fundamental principles: justification, optimisation and dose limitation.

The principle of justification requires that any decision that alters the radiation exposure situation should do more good than harm; in other words, the introduction of a radiation source should result in sufficient individual or societal benefit to offset the detriment it causes.

The principle of optimisation requires that the likelihood of incurring exposures, the number of people exposed and the magnitude of their individual exposure should all be kept as low as reasonably achievable, taking into account economic and societal factors. In addition, as part of the optimisation procedure, the ICRP recommends that there should be restriction on the doses to individuals from a particular source and this leads to the concept of dose constraints.

The third principle of the ICRP’s system of protection is that of dose limitation. This principle requires that the dose to individuals from planned exposure situations, other than medical exposure of patients, should not exceed the appropriate limits recommended by the Commission.

As part of the system of protection, ICRP publication 103 defines three categories of exposure situations (ICRP 2007), namely: planned exposure situations which involve the deliberate introduction and operation of sources; emergency exposure situations, which require urgent action in order to avoid or reduce undesirable consequences; and existing exposure situations, which include prolonged exposure situations after emergencies. By adopting this approach, in principle, the ICRP system of protection should be able to be applied to any situation of radiation exposure, including that associated with security screening. Within the ICRP system, security screening would be considered to be a planned exposure.

The ICRP recognises three categories of exposed individuals: workers, patients and members of the public. These categories of exposure are known as occupational, public and medical exposure. Occupational exposure is generally interpreted as radiation exposure of individuals as a result of their work. However, as radiation is ubiquitous, only those exposures that can reasonably be regarded as the responsibility of the operating management are included. Medical exposure is predominantly that of patients but also includes exposures incurred by those caring for patients, other than as part of their occupation, and exposures incurred by volunteers as part of biomedical research programmes, where there is no direct benefit to the volunteer. Public exposure then incorporates all exposures other than medical and occupational.

The principles of justification and optimisation apply universally to all three categories of exposure situations (planned, emergency and existing), whereas dose limits apply only to planned exposure situations. The exception to this is planned exposure situations involving medical exposure where dose limits do not apply. In the absence of a dose limit, dose constraints assume a particular importance.

Dose constraints are used as part of the optimisation process for planned exposures. They represent a level of individual dose which should not, in normal circumstances, be exceeded. They are used in the planning process and the chosen value will depend on the circumstances of the exposure under consideration. They are not a limit and do not represent a demarcation between safe and dangerous levels of radiation exposure but are used, prospectively, as a tool for optimisation. For planned exposures that have a dose limit associated with them, dose constraints should be lower than the pertinent dose limit.

The term ‘practice’ was first introduced in 1991 in the publication ICRP 60 (ICRP 1991) to distinguish between an activity that added doses and one that reduced doses. The latter was known as an intervention. While the ICRP in their more recent publication ICRP 103 (ICRP 2007) have moved to a situation-based approach, as outlined above, they still use the term ‘practice’ to denote an activity that causes an increase in exposure to radiation or in the risk of exposure to radiation. It is implicit in the concept of a practice that the radiation sources that it introduces or maintains can be controlled directly by action on the source. It is understood, within the ICRP system of radiation of protection, that justification is a prior requirement of any new practice.

Although the ICRP revised and updated their recommendations on radiation protection in their 2007 document, ICRP 103, current European legislation is still based on the recommendations contained in their earlier document, ICRP 60 (ICRP 1991).

3.2.2 Justification of practices

The justification of practices involving ionising radiation prior to their introduction into routine use must demonstrate economic, social or other benefits in relation to the health detriment they may cause. Depending on the type of practice under consideration, this justification process can be complex and may involve consideration of a wide range of societal and economic factors, in addition to the potential dose detriment. The consequences to be considered are not confined to those associated with radiation; they also include other risks as well as the costs and benefits of the activity. Sometimes the radiation detriment will be a small part of all factors considered and it is important that other types of detriment are considered. Similarly, benefit must be determined. Justification therefore goes far beyond the scope of radiological protection.

Responsibility for judging the justification of new or existing practices usually falls on national radiation protection authorities to ensure an overall benefit in the broadest sense to society although not necessarily to the individual. However, these authorities are likely to need input from other stakeholders so that a fully informed decision can ultimately be made in relation to justification. To search for the best of all the available alternatives is a task beyond the responsibility of radiological protection authorities (ICRP 2007).

Although the justification process considers the potential benefits and detriments to the exposed individual and to society, a practice may be considered to be justified even if there are no benefits to the individual provided the benefit to society is sufficiently strong. Application of the justification principle to a new practice requires that no practice should be introduced unless it produces sufficient net benefit to the exposed individual or to society to offset the radiation detriment it causes. The justification may need to be re-examined as new information or technology becomes available.

This principle of balancing benefit and detriment is not unique to radiation safety but while often the balancing is done implicitly, the justification process will require an explicit demonstration of a net benefit.

The fact that the doses arising from a practice may be well below the public dose limit does not remove the requirement for justification or optimisation.

3.2.3 Legislative framework

In the European Union, radiation protection legislation relating to ionising radiation derives from the Euratom Treaty. Its common objective is to establish uniform safety standards to protect the health of workers, patients and of the general public and to ensure that they are applied. The specific requirements for radiation protection are laid down in Title II Chapter 3 "Health and Safety", Articles 30 to 39 of the Euratom Treaty. This system has been embodied in various European Directives most notably the Basic Safety Standards (BSS, originally adopted in 1959 and last revised by Council Directive 96/29/EURATOM) and the Medical Exposure Directive (MED, 97/43/EURATOM).

The BSS lays down the requirements for the protection of the health of workers and the general public against the dangers of ionising radiation. It encapsulates the principles of justification, optimisation and dose limitation and applies them to the regulatory system that controls practices involving ionising radiation. The scope of the Directive is wide and incorporates requirements for reporting to the Competent Authorities of a wide range of practices involving the use of ionising radiation and for prior authorisation of many of these practices. The BSS sets dose limits for workers and members of the public and requires that workplaces are organised in a way that delineates and controls areas according to risk of exposure. The dose limitation requirement does not apply to three distinct groups of individuals exposed as a result of the use of ionising radiation in medicine – patients, persons knowingly and willingly helping patients (but not as part of their occupation) and volunteers in (bio)medical research. The BSS specifies the dose limit for workers as 100 mSv in a consecutive five-year period, subject to a maximum effective dose of 50 mSv in any single year. For members of the public, the limit is 1 mSv per year.

The Medical Exposure Directive (MED) deals with the health protection of individuals against the dangers of ionising radiation in relation to medical exposure. This Directive replaced the Patient Directive (84/466/EURATOM) and is the main legal instrument dealing with the protection of patients undergoing diagnostic and therapeutic procedures which utilise ionising radiation.

The MED aims at eliminating the practice of unnecessary medical exposures and to this end the principle of justification is central to the Directive. Justification and optimisation are seen as key in implementing radiation protection in medicine. The scope of the Directive includes not only patients but also other individuals exposed either directly or indirectly. This includes those exposed in occupational health surveillance, health screening, research and medico-legal procedures. Passenger security scanning using ionising radiation is not addressed explicitly in the current text of either the BSS or the MED. However, it has been considered in the context of the revision of the BSS which is currently under discussion.

Since the first BSS Directive was adopted, in 1958, it has been updated many times. The latest update was in 1996. A further revised and updated version was submitted as a Commission proposal to the European Parliament and the Economic and Social Affairs Committee in September 2011. In addition to the BSS, the proposal incorporates a revised version of the MED along with a number of other Directives which deal with radiation safety. The proposal and the opinions of the bodies mentioned above will be further considered by the European Council prior to adoption of a revised Directive. The following section describes the current requirements and the proposed revisions of the requirements are described in section 3.2.2.3.

3.2.3.1 Medico-legal procedures

The MED defines medico-legal procedures as ‘procedures performed for insurance or legal purposes without a medical indication’. In including medico-legal exposures within the scope of the MED Directive, the objective was to ensure that persons presenting for medico-legal procedures were afforded at least the same level of protection as patients.

Medico-legal procedures were originally envisaged to be X-rays for insurance purposes and X-rays arising as a result of legal proceedings. In fact, the definition of medico-legal procedures is such that the scope is almost certainly wider. As a consequence, the range of exposures that might be considered to be medico-legal is both broad and diverse, extending beyond those performed for insurance or as a result of legal proceedings. Exposures arising from the use of security scanners for screening purposes fall under the broad category of medico-legal exposures.

Until such time as existing legislation is revised, the provisions within the Medical Exposure Directive apply. Article 5.4 of this Directive requires Member States to ensure that procedures are put in place that should be observed in the case of medico-legal exposures. The Directive also requires that special attention be given to the justification and optimisation of such exposures (Art 3.1 (d)).

Although medico-legal exposures are considered to be a sub-set of medical exposures, unlike medical exposures that are regarded as exposure of individuals as part of their own medical diagnosis or treatment, medico-legal exposures are not exempt from the public dose limit (96/29/EURATOM, Article 6.4). Therefore the dose limits set out in the BSS, for a member of the public, apply and so the limit for effective dose as a result of medico-legal exposures, such as security scanning, is that applicable to a member of the public. The categorisation of exposures to staff that are required to be screened (airline crews, airport workers, couriers, and others) as part of their occupation is less clear. The current thinking within the ICRP seems to indicate that these will be considered as public exposures rather than occupational and if this is the case then the public dose limit will apply.

3.2.3.2 Legal requirement for justification

The justification of practices involving ionising radiation prior to their introduction into routine use is a legal requirement enshrined in the BSS and the MED. The BSS requires Member States to ensure that all new types of practices are justified by their economic, social or other benefits in relation to the health detriment they may cause, in advance of being first approved.

In relation to justification, the BSS requires an explicit demonstration of a positive net benefit before a practice can be authorized by the regulatory body. As discussed in section 3.2.2., justification is likely to be a complex task and Member States will require some mechanism to ensure that an appropriate level of consultation takes place, commensurate with the radiological and social significance of the type of practice, before it can be considered to be either justified or unjustified.

The justification process may result in particular requirements being applied to these practices. Screening techniques, where the primary focus is security, could also be used to detect other contraband, such as illegal drugs, on a person. However, in the case for justification, the applicant should identify the primary purpose for introducing the technique to the Justifying Body and address issues that may arise that are not pertinent to the primary purpose.

The fact that the doses arising from the use of screening for security purposes may be well below the public dose limit does not remove the requirement for justification. In addition, for practices that are justified and subsequently authorised, optimisation measures must be taken so that all exposures are as low as reasonably achievable (the ALARA principle) for workers, the general public, and the population as a whole.

3.2.3.3 Revision of legislation

The European Commission has undertaken the simplification of Community legislation in the area of radiation protection and has proposed the consolidation into a single text of five Directives. The main Directive is the BSS. The remaining four Directives cover different specific aspects of radiation safety complementary to the overall BSS. This includes health protection during medical exposures (97/43/EURATOM), the control of high activity sealed sources (2003/122/EURATOM), communication issues in an emergency situation (89/618/EURATOM) and the protection of outside workers (90/641/EURATOM).

One of the most significant changes in the revised Directive is in the way exposures previously classified as medico-legal are dealt with. Those exposures have been redefined as ‘non-medical imaging exposure’ and have been put under appropriate regulatory control. The new definition includes ‘any deliberate exposure of humans for imaging purposes where the primary motivation for the exposure is not related to the health or well-being of the individual being exposed’. The need for justification of such practices, in three stages as for medical exposures, and for establishing associated conditions, has been worked out, including the differentiation between procedures implemented by medical staff using medical equipment and procedures implemented by non-medical staff using non-medical equipment, as in security screening.

The BSS annual dose limit and corresponding constraints for public exposure apply, while allowing for some exceptions for some specific non-medical exposure procedures carried out in a medical environment such as drug searches within the body.

3.2.3.4 Implications of the Revised Directive for security screening of passengers

The revised Directive requires a system of authorisation for non-medical imaging exposures, including security screening. The requirements for justification and optimisation have been strengthened. The Directive requires that, in addition to the initial justification of the practice, each particular application of a generally accepted type of practice be justified in advance. Each justification must also be periodically reviewed by the Competent Authority. The Competent Authority must ensure that requirements for the practice, including criteria for individual implementation, are established as appropriate in cooperation with other relevant agencies and professional bodies.

The Competent Authority is required to ensure that dose constraints are established for security screening and that these are set to ensure that annual doses to members of the public remain well below 1 mSv (see draft revised BSS, article 23.3c). This dose criterion is likely to be readily achievable, even for the most frequently exposed groups (air crews, couriers and frequent flyers). The Directive requires that informed consent of the individual to be exposed is sought, although it does allow for exceptions where law enforcement bodies may proceed without consent, if that is permitted by national legislation. Finally, the revised Directive requires that where the exposure is routinely carried out for security purposes the screened individuals are provided with a choice of an alternative technique which does not involve exposure to ionising radiation.

Source & ©: , Health effects of security scanners for passenger screening (based on X-ray technology), (2012),
 3.2 System and Legislative Framework for Radiation Protection, pp.14-18