Radioactivity in the environment chapter 2 radiation risks and the ICRP

Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP Radioactivity in the environment chapter 2 radiation risks and the ICRP

Radioactivity in the Environment, Volume 19

ISSN 1569-4860, http://dx.doi.org/10.1016/B978-0-08-045015-5.00002-2

Jack Valentin a

Jack Valentin Radiological Protection, Stockholm, Sweden

E-mail: jack.valentin@telia.com

2.1 WHAT IS ICRP?

The International Commission on Radiological Protection, ICRP for short, is an advisory nongovernmental organization, established to advance for the public benefit the science of radiological protection, in particular by providing recom-mendations and guidance on all aspects of protection against ionizing radiation Its recommendations form the basis of the basic safety standards documents issued by the United Nations and the European Commission and are reflected worldwide in legislation and regulations concerning radiation

ICRP was formed in 1928 by the International Congress of Radiology, with the name of the International X-ray and Radium Protection Committee (IXRPC), following a decision by the Second International Congress of Radiology

a Although the author was the Scientific Secretary of ICRP from 1997 through 2008, the views presented here are his own and do not necessarily represent those of ICRP.

Radiation Risks and the ICRP

Chapter Outline

2.1 What is ICRP? 17

2.2 The Aims and Scope of

ICRP Recommendations 18

2.3 The Early History and

Development of

ICRP Recommendations 21

2.4 The Development of the

System of Radiological

Protection and Current

ICRP Recommendations 23

2.5 Ethical Underpinning of the

Evolution of

ICRP Recommendations 26

2.6 Some Moot Points 29

2.6.1 Different Dose Limits for Occupational or

2.6.2 Protecting Average Individuals or the Most

2.6.4 Cultural Differences

in Ethical

In 1950 it was restructured and renamed as now It is an independent char-ity (i.e a nonprofit-making organization), registered in the United Kingdom It works closely with its sister body, the International Commission on Radiation Units and Measurements (ICRU), has official relationships with several United Nations bodies, the European Commission, and the Nuclear Energy Agency

of the OECD, and works with organizations such as the major international standardization bodies (ISO and IEC) ICRP maintains contact with the pro-fessional radiological community through links with the International Radia-tion ProtecRadia-tion AssociaRadia-tion and takes account of progress reported by naRadia-tional organizations (ICRP, 2007a)

ICRP comprises a Main Commission with a Chairperson, 12 other members, and a Scientific Secretary; five Committees (each with 10–20 members) dealing with various aspects of radiological protection; and a number of ad hoc Task Groups and Working Parties drafting new advisory documents At any one time, some 200–250 people worldwide are engaged within ICRP More information about ICRP and its membership is available at its web site, www.icrp.org Early on in the history of ICRP, it became apparent that its independence and scientific integrity could be jeopardized by demands from special inter-est groups and others with vinter-ested interinter-ests Its second ever meeting, in 1934, involved pressures concerning membership that were the first, but certainly not the last, examples of demands or covert criticisms aimed at gaining out-side control the membership and/or policies of ICRP Wary of such attempts, ICRP maintains as its strict policy that members are elected by the Commission itself Outside nominations are accepted as a means to achieve the widest pos-sible range of expertise, but the actual elections are made by the Commission alone, and solely on the grounds of scientific merit, not as representatives of any country, organization, or other entity (Clarke & Valentin, 2009)

2.2 THE AIMS AND SCOPE OF ICRP RECOMMENDATIONS

According to its current general recommendations, the primary aim of the Com-mission’s recommendations is to contribute to an appropriate level of protec-tion for people and the environment against the detrimental effects of radiaprotec-tion exposure without unduly limiting the desirable human actions that may be asso-ciated with such exposure (ICRP, 2007a)

Obviously, as underlined in the 2007 Recommendations, this aim cannot

be achieved solely on the basis of scientific knowledge on radiation exposure and its health effects Scientific data are a necessary prerequisite, but societal and economic aspects of protection have also to be considered All of those concerned with radiological protection have to make value judgments about the relative importance of different kinds of risk and about the balancing of risks and benefits In this, radiological protection is not different from other fields concerned with the control of hazards Thus, ICRP (2007a) states that the basis for, and distinction between, scientific estimations and value judgments should

be made clear whenever possible, so as to increase the transparency, and thus the understanding, of how decisions have been reached

Nevertheless, the formal ethical bases on which the Recommendations of ICRP rest are not explicitly mentioned in the formal Recommendations, and touched upon in just a few ICRP documents General discussions are provided

in ICRP (1999, Annex D) and Clarke and Valentin (2009); specific aspects of medical ethics are mentioned in ICRP (1996) and the particular ethical consid-erations in the context of volunteers in medical research are discussed in some detail in ICRP (1992)

In order to understand the ethical issues involved in radiological protec-tion, one needs to know that in general, ionizing radiation causes two types

of harmful effect High doses will cause harmful tissue reactions, often called

deterministic effects These are often of an acute nature, and they will usually only appear if the dose exceeds a threshold value Both high and low doses may

cause stochastic effects (cancer or heritable effects) Spontaneous cancers and

genetic damage occur frequently, and at the present state of scientific knowl-edge it is not possible to distinguish radiation-induced cases from spontaneous ones However, while the specific cases cannot be attributed to radiation, given sufficiently large exposed populations and sufficiently high doses, statistically detectable increases in the population incidence of cancer occur long after the exposures

For various statistical reasons no such significant increase in the incidence

of heritable effects has yet been demonstrated, but unequivocal evidence from animal and plant experiments, population genetic considerations, and observa-tions of damage to the genetic material in human somatic cells all prove beyond any shadow of a doubt that heritable effects are also produced—albeit at a fre-quency which is too low to demonstrate statistically in man against the back-ground of our considerable genetic burden of natural variation

The ICRP system of radiological protection aims primarily to protect human health, and historically, this was the only aspect considered in any way at all until the ICRP (1977) Recommendations The health objectives are to manage and control exposures to ionizing radiation so that deterministic effects are pre-vented, and the risks of stochastic effects are reduced to the extent reasonably achievable (ICRP, 2007a)

The protection of other species and the environment is a more recent, and somewhat more complicated, issue ICRP (1977) claimed that “the level of safety required for the protection of all human individuals is thought likely

to be adequate to protect other species, although not necessarily individual members of those species The Commission therefore believes that if man

is adequately protected then other living things are also likely to be suffi-ciently protected.” In a marginally more sophisticated phrase, ICRP (1991)

assumed that “the standard of environmental control needed to protect man to the degree currently thought desirable will ensure that other species are not put at risk Occasionally, individual members of nonhuman species might be

harmed, but not to the extent of endangering whole species or creating imbal-ance between species.”

However, ICRP (2007a) observed that “there is no simple or single uni-versal definition of “environmental protection” and the concept differs from country to country and from one circumstance to another.” Other ways of con-sidering radiation effects are therefore likely to prove to be more useful for nonhuman species—such as those that cause early mortality, or morbidity, or reduced reproductive success The Commission’s aim is now that of preventing

or reducing the frequency of deleterious radiation effects to a level where they would have a negligible impact on the maintenance of biological diversity, the conservation of species, or the health and status of natural habitats, communi-ties, and ecosystems In achieving this aim, however, the Commission recog-nizes that exposure to radiation is but one factor to consider, and is often likely

to be a minor one

The ICRP system of radiological protection applies to all ionizing radia-tion exposures from any natural or man-made source, regardless of its size and origin This however does not mean that all exposures, sources, and human actions, can or need to be equally considered Instead, the approach should be graded according to the amenability of a particular source or exposure situation

to regulatory controls, and the level of exposure/risk associated with that source

or situation (ICRP, 2007b)

Thus, exposures that are not amenable to control, regardless of their

magni-tude, are excluded from radiological protection legislation For instance,

expo-sure to the natural radionuclide 40K incorporated into the human body cannot

be restricted by any conceivable regulatory action, and control of exposure to cosmic rays at ground level is obviously impractical In short, some exposures cannot be regulated

Furthermore, exposures that are such that the effort to control them is judged

to be excessive compared to the associated risk should be exempted from some

or all radiological protection regulatory requirements For instance, while it is important to control the manufacture and supply of smoke detectors containing radioactive material, it makes sense to exempt their use in homes from regu-latory licensing requirements In short, some exposures (or more often, some aspects of some exposures) need not be regulated

This does not necessarily mean that exempted exposures equal small doses Even a small dose is worth removing, if the effort to do so is small Conversely,

if no reasonable control procedure can achieve significant dose reductions, exemption is warranted even if the doses are not trivially small

Given the multitude of different exposure situations, the enormous range of possible doses, and the extreme sensitivity of radiation measuring equipment (compared with instruments for most other noxious agents), the need for the concepts of exclusion and exemption is usually taken as an indisputable fact in the public debate The choice of exposures and exposure situations that merit exclusion is usually also reasonably uncontroversial In contrast, exemption

decisions may be rather more difficult, depending for instance on different per-ceptions of benefits and risks of particular situations involving radiation

As an added complication, exemption may sometimes be seen as a means to achieve conservation of resources, which is usually regarded as ethically com-mendable “Clearance” is a special case of exemption where regulatory control

is relinquished because it is no longer warranted For instance, much material (tools, clothes…) is taken into controlled areas of nuclear installations Such material will by default be regarded as contaminated (and often is) Much of

it can be returned outside the installation and reused after appropriate decon-tamination and/or measurements While the concept of such clearance is not highly controversial, the levels and conditions to be applied can be the subject

of heated debate

2.3 THE EARLY HISTORY AND DEVELOPMENT OF

ICRP RECOMMENDATIONS

The discoveries of X-rays in 1895 and radioactivity in 1896 immediately spawned numerous practical applications of these phenomena, particularly in medicine The capacity of these radiations to cause serious damage to human tissues (what we now usually call deterministic effects or tissue reactions) also became apparent within months (e.g Drury, 1896), and by 1902, Frieben extended the observation to include the induction of cancer However, ignorance about the risks was widespread, there were numerous injuries over the next two decades, and several hundred deaths of medical staff (Molineus, Holthusen, & Meyer, 1992)

This was the backdrop that caused the 2nd International Congress of Radiology, in Stockholm 1928, to establish the “International X-ray and Radium Protection Committee” (IXRPC), which later developed into ICRP As indicated above, the carcinogenic effect of ionizing radiation was already known, and in the previous year, Muller (1927) had reported that X-rays induce mutations in the genetic material

Nevertheless, at this initial stage the protection philosophy was focused entirely on deterministic effects (described in the first Recommendations,

IXRPC, 1928; as “injuries to superficial tissues, derangements of internal organs and changes in the blood”) The main emphasis of the 1928 Recommendations was on practical physical protection, such as shielding No form of dose limit was proposed, but a prolonged holiday and a limitation of the working hours

of medical staff were recommended The occupational annual effective dose to medical staff at the time may have been in the order of 1000 mSv (cf Clarke & Valentin, 2009)—this corresponds to about 400 times the average dose due to natural sources and is 50 times higher than the current recommended limit on average annual effective dose for occupational exposures

The first “dose limit” (actually, a recommended limit on exposure rate for X-rays) was promulgated with the IXRPC (1934) Recommendations It was

still based entirely on the desire to avoid deterministic effects, and the recom-mendations clearly implied the concept of a safe threshold below which no untoward effects were expected In modern terms and units, the limit would have corresponded to an annual effective dose of approximately 500 mSv This would likely have achieved what the limit set out to do, i.e to prevent determin-istic harm (at least to healthy adults), but of course was inadequate with respect

to stochastic harm

These IXRPC Recommendations led to a great improvement in the standard

of occupational radiation safety The “dose limits” also served as the basis for the safety measures applied when nuclear energy programs were first developed during and immediately after World War II (Sowby, 1981) Sowby stresses that thanks to this, there were very few radiation injuries among the many thou-sands of workers involved in the early days of nuclear energy, despite the large amounts of radioactive material they handled

The next, 1950, set of Recommendations appeared under the Commis-sion’s new name, ICRP (1951) Again, the quantitative restriction on expo-sures became more stringent; the new recommended limits correspond in modern terminology to an annual limit on occupational effective dose of approximately 150 mSv (although the concept of a limit was somewhat differ-ent than the currdiffer-ent limits) Health effects that “should be kept under review” now included not just deterministic effects, but also, e.g leukemia, malignant tumors, and genetic effects

However, it is not immediately apparent that the inclusion of stochastic effects among those health parameters that should be monitored actually influ-enced the recommendations as such or, in particular, the “dose limit” The reduction from ∼500 mSv in a year to ∼150 mSv in a year may have reflected that ICRP considered the possibility of individual variations in radiosen-sitivity Genetic harm had been known for many years already to occur at quite low doses in experimental organisms, and the 1950 Recommendations

“strongly recommended that every effort be made to reduce exposures to all types of ionizing radiation to the lowest possible level”—but, inconsistently, the text was also full of expressions like “permissible levels”, “maximum per-missible exposure”, and “the probable threshold for adverse effects” All of these implied the existence of a safe threshold below which there would be no deleterious effects

The situation started to change with the next, 1954, set of Recommenda-tions (ICRP, 1955) which claimed that: “whilst the values proposed for maxi-mum permissible doses are such as to involve a risk which is small compared

to the other hazards of life … it is strongly recommended that every effort be made to reduce exposure to all types of ionizing radiation to the lowest possible level.” ICRP now recognized (albeit somewhat vaguely) the need to protect not just radiation workers but also the general public, e.g with nuclear energy expected to be an expanding industry The major problem was believed to be hereditary harm, but the occurrence of leukemia among radiologists and among

the survivors in Hiroshima and Nagasaki also contributed to the decision to rec-ommend that “in the case of the prolonged exposure of a large population, the maximum permissible levels should be reduced by a factor of 10 below those accepted for occupational exposures.”

In a short amendment ICRP (1957) made several points reflecting signifi-cant ethical decisions Thus, it was recommended that the dose restrictions for members of the public should apply to staff working outside “controlled areas” within an enterprise involving radiation In other words, only those employees who were actually working with radiation (and would usually ben-efit from pertinent training) were to be regarded as occupationally exposed This clarification must have had a significant effect in terms of reduced doses

to other staff

Furthermore, for the first time specific advice concerning pregnant women was provided: “Since … the embryo is very radiosensitive, special care should be exercised to make sure that pregnant women are not occupationally exposed … through some accident or otherwise … to large doses of penetrat-ing radiation.”

This was soon followed by a major revision in the shape of the 1958 Recom-mendations, also somewhat quaintly called “Publication 1” (ICRP, 1959) They proposed new limitations of dose for occupational exposure and, for the first time in formal terms, for members of the public The occupational limit was expressed as a restriction on the dose accumulated at any particular age in years, and corresponded to an average annual effective dose of 50 mSv, while the public limit was expressed was simply set per year at what is now termed 5 mSv The dose limit for the public reflected the understanding that stochastic effects had to be taken into account, and that for such effects no safe threshold dose could be taken for granted There was not yet any clear dose–response model, malignant tumors were not really considered, and leukemia was regarded as possibly not stochastic in nature, so the concern regarding stochastic effects was focused on genetic harm Yet the 1958 Recommendations constituted a paradigm shift that subsequently evolved into the current system of radiological protection

2.4 THE DEVELOPMENT OF THE SYSTEM OF RADIOLOGICAL PROTECTION AND CURRENT ICRP RECOMMENDATIONS

The increasing understanding of stochastic effects soon necessitated further revisions The ICRP (1966) Recommendations, Publication 9, ventured a speculation on the possible dose–response relationship for stochastic effects:

“the Commission sees no practical alternative, for the purposes of radiological protection, to assuming a linear relationship between dose and effect, and that doses act cumulatively The Commission is aware that the assumptions of no threshold and of complete additivity of all doses may be incorrect, but is satis-fied that they are unlikely to lead to the underestimation of risks.”

Thus the default assumption of a safe threshold was rejected For sto-chastic effects, primarily the probability rather than the severity of the effect

is proportional to the size of the dose Therefore, the objective of radiologi-cal protection refocused onto reducing and limiting the probability of harm, rather than preventing harm As a logical consequence, it was no longer sufficient to aim at keeping doses below a limit The concept of optimiza-tion of protecoptimiza-tion was signaled in the statement in ICRP (1966) that “as any exposure may involve some degree of risk, the Commission recommends that any unnecessary exposure be avoided and that all doses be kept as low

as is readily achievable, economic and social consequences being taken into account.”

The 1966 Recommendations also introduced a distinction between “normal operations” and accidents where the exposure “can be limited in amount only,

if at all, by remedial action.” Again, this raised new ethical issues, not least concerning the protection aims for emergency staff that might have to deal with situations entailing high dose rates

The requirement that doses be reduced even below the dose limits neces-sitated further guidance In a report, ICRP (1973) tightened up the requirement

by stating that doses should be kept as low as reasonably achievable, rather than

readily achievable, and suggested that differential cost–benefit analysis (CBA) could be used to ensure that protection was indeed optimized

The next set of Recommendations, ICRP (1977), developed this by stating

that doses “as low as reasonably achievable” would correspond to a collective

dose so low that “any further reduction in dose would not justify the incremental cost required to accomplish it.” The Recommendations went on to recommend that this be analyzed with CBA with collective dose as the independent vari-able and with a monetary value assigned to a unit of collective dose Thus, the question that was asked (and hopefully answered by the use of CBA) was “How much does it cost and how many lives are saved?” This also meant that optimi-zation of protection was the main means of radiological protection Dose limits were no longer a primary regulatory tool, although they had to be retained in order to protect the individual from the combined exposure from all controlled sources

The 1977 Recommendations also established the formal System of

radiological protection, which is essentially still in place today (with some amendments and shifting accents as described below) The system includes three basic principles, viz.,

justification—no practice shall be adopted unless it produces a positive net benefit;

optimization—doses shall be as low as reasonably achievable, and economic and social factors taken into account;

application of limits—doses to individuals shall not exceed recommended limits

The levels of dose at the limits were assumed to represent exceptional cases Thus, although it was claimed that an average annual dose of 1 mSv would entail a risk that members of the public were likely to regard as acceptable, the public annual dose limit of 5 mSv was retained It was argued that a public annual dose limit of 5 mSv would achieve lifetime doses corresponding to an average of 1 mSv per year in “critical [=highly exposed] groups.” Similarly, the dose limit for workers was argued on a comparison of average doses, and therefore risk, in the workforce, with average risks in industries that would be recognized as being “safe”, and not on maximum risks to be accepted

The following, 1990, set of Recommendation (ICRP, 1991) included both revised risk estimates and significant amendments to the system of protection Both the epidemiology and the dosimetry concerning cancer among survivors from Hiroshima and Nagasaki showed that the risk of cancer per unit dose

of radiation had to be adjusted upwards by a factor of about 3 As a conse-quence, the 1990 Recommendations re-emphasized the need to keep doses as low as reasonably achievable ICRP also reduced the annual dose limits from

50 mSv to 20 mSv for occupational exposure (averaged over 5-year periods with a maximum of 50 mSv in any one year), and from 5 to 1 mSv for public exposure

These reductions should not be construed as directly proportional to the increased risk estimates The concept of an acceptable risk, as discussed in the

1977 Recommendations, was no longer regarded as satisfactory People tend

to accept or reject activities (with their attendant benefits and risks) rather than specific risk values ICRP (1991) used a much more sophisticated multi- attribute study to illuminate different risk dimensions associated with exposures

at the dose limits

Furthermore, the three basic principles were rephrased, and the most signifi-cant amendment concerned the optimization principle: “In relation to any par-ticular source within a practice, the magnitude of individual doses, the number

of people exposed, and the likelihood of incurring exposures where these are not certain to be received should all be kept as low as reasonably achievable, economic and social factors being taken into account This procedure should be constrained by restrictions on the doses to individuals (dose constraints), or on the risks to individuals in the case of potential exposures (risk constraints) so as

to limit the inequity likely to result from the inherent economic and social judg-ments.” Thus, while the primary aim of optimization is to reduce the collective dose, ICRP added a restriction on individual dose to the process

The current ICRP (2007a) Recommendations reiterate the system of radiological protection Thus, they represent continuity rather than change to the fundamental features, and they again emphasize the importance of opti-mization However, they also extend the concept Added guidance on how to use constraints in planned exposure situations (such as the normal operation

of practices using radiation) is complemented by the extension of optimiza-tion, with constraints, to other situations (i.e emergencies and existing exposure

situations) Furthermore, the 2007 Recommendations include a commitment to environmental protection

2.5 ETHICAL UNDERPINNING OF THE EVOLUTION OF

ICRP RECOMMENDATIONS

While explicit discussions of formal ethical underpinnings are rare in ICRP documents, this certainly does not mean that ICRP is unaware of the importance

of such discussions For instance, the ICRP (1966) Recommendations state that

“as any exposure may involve some degree of risk, the Commission recom-mends that any unnecessary exposure be avoided and that all doses be kept as low as is readily achievable, economic and social consequences being taken into account.” Here, ICRP considered ethical considerations to be implied in the word “social” (or, in the corresponding version of the same statement in the current, 2007, Recommendations, “societal”)

Sometimes, debaters suggest that ICRP (or other organizations) should refrain from proposing a particular ethical approach However, one cannot lift oneself from the floor by the bootstraps, i.e protection recommendations will inevitably represent an ethical position, irrespective of whether that position is explicit, tacitly implied, or unpremeditated Better then to specify the position, thus allowing users of the recommendations to adapt them to their own ethical predilections! Ethical issues are often discussed within ICRP before new docu-ments are released for publication, and several leading representatives of ICRP have produced papers reflecting the basic tenets as well as their own views and interpretations (e.g Beninson, 1996; González, 2011; Lindell, 1988; Silini,

1992; Taylor, 1957)

However, initially the level of sophistication of the ethical considerations was not very advanced Between 1896, when deleterious effects of ionizing radiation were first identified as such, and the mid-1950s, when public concern about radiation risks increased and the focus of protection shifted toward sto-chastic harm, the purpose of radiological protection was just to avoid determin-istic harm The principle that was applied in order to achieve this was simply to keep individual doses below pertinent threshold values Low doses of radiation were not a concern; if anything, they were regarded as beneficial There was a plethora of radioactive consumer products

Little is known about any ethical discussions within ICRP during this period; the protection philosophy appears to have been based loosely on Aristotelian virtue ethics In other words, protective actions should be “good” and follow from an inner sense of moral orientation

The first documented instance of a discussion within ICRP of the philosophy and principles of radiological protection is provided in the “Prefatory Review”

of the 1958 Recommendations (ICRP, 1959) Neither ethics nor morals are men-tioned explicitly, but in a section called “Objectives of Radiation Protection” the Recommendations state specifically that these are “to prevent or minimize