Radioactivity in the environment chapter 9 ALARA what is reasonably achievable

Radioactivity in the environment chapter 9 ALARA what is reasonably achievable Radioactivity in the environment chapter 9 ALARA what is reasonably achievable Radioactivity in the environment chapter 9 ALARA what is reasonably achievable Radioactivity in the environment chapter 9 ALARA what is reasonably achievable Radioactivity in the environment chapter 9 ALARA what is reasonably achievable Radioactivity in the environment chapter 9 ALARA what is reasonably achievable

Radioactivity in the Environment, Volume 19

ISSN 1569-4860, http://dx.doi.org/10.1016/B978-0-08-045015-5.00009-5

ALARA: What is Reasonably

Achievable?

Sven Ove Hansson

Royal Institute of Technology (KTH), Division of Philosophy, Stockholm, Sweden

E-mail: soh@kth.se

9.1 INTRODUCTION

Our knowledge about the dangers of ionizing radiation has passed through three stages In the first few years after Röntgen’s discovery of X-rays in 1895, the risks were unknown and researchers exposed themselves and others to high exposures that we now know to have lethal effects In the second phase, begin-ning about 1900, it was recognized that acute effects such as skin burns can result from high short-term exposures Efforts were made to keep doses well below the levels that had given rise to these effects It was believed that below those levels there was no danger, so that exposure limits could provide complete protection against the negative health effects of radiation (Kathren & Ziemer, 1980) The third phase has its origin in the discovery that accumulated exposure to ionizing radiation increases the risk of cancer, in particular leukemia Beginning

in the 1950s, radiation protectors extended their concerns from acute effects to long-term genetic and cancer effects Such effects appeared to be stochastic, and there did not seem to be any threshold dose below which they disappear com-pletely (Lindell, 1996) This was expressed as an uncertain hypothesis in a report

by the International Commission on Radiological Protection (ICRP) in 1959:

Chapter Outline

9.1 Introduction 143

9.2 ALARA and Optimization

in the Radiation Protection

9.3 A Three-Levelled Model 146

9.4 What is “Reasonably

9.5 The Scope of Economic

9.6 ALARA and Cost-Benefit

9.7 Related Principles of

9.8 Conclusion 154

“The mechanism of leukemia induction by radiation is not known It may be postulated that if the dose is lower than a certain threshold value no leukemia is produced In this case it would be necessary to estimate the threshold dose and to make allowances for recovery, if any There is not sufficient information to do this, but caution would suggest that an accumulated dose of 750 rem might exceed the threshold The most conservative approach would be to assume that there is no threshold and no recovery, in which case even low accumulated doses would induce leukemia in some susceptible individuals, and the incidence might be proportional to the accumulated dose The same situation exists with respect to the induction of bone tumors by bone-seeking radioactive substances.”

(ICRP, 1959, p 4)

Perhaps ironically, major advances in radiation protection were made in the Man-hattan project, the same project that resulted in the worst radiation exposures that the world has seen In order to protect their own personnel, the project assigned

to Dr Robert S Stone in the Health Division of the Metallurgical Laboratory in Chicago the task of setting “tolerance levels” for radiation He and his colleagues made it clear that since there is no absolutely safe level, radiation exposures should

be kept at the lowest level that was practically possible to achieve After the war, this principle was adopted by the country’s National Committee on Radiation Pro-tection (NCRT) that stated in 1954 that radiation exposures should “be kept at the lowest practical level” (Auxier & Dickson, 1983) The International Commission

on Radiological Protection (ICRP) made a similar recommendation in 1959:

“[T]he Commission recommends that all doses be kept as low as practicable, and that any unnecessary exposure be avoided.”

(ICRP, 1959, p 11)

This recommendation has repeatedly been confirmed by the Commission In the

1977 recommendations, it was rephrased as a requirement that “all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account” (ICRP, 1977, p 3) Over the years, the principle has been known under several different names:

as low as practicable (ALAP)

as low as reasonably achievable (ALARA)

as low as reasonably attainable (ALARA)

as low as reasonably practicable (ALARP)

so far as is reasonably practicable (SFAIRP) (HSE, 2001a, p 92)

ALAP appears to have been the first of these abbreviations In the early 1970s,

it was replaced by ALARA (mostly in the US) and ALARP (mostly in Europe) that were thought to be less imprecise (Wilson, 2002) Some authors have tried

to make distinctions between these terms:

“What is achievable is a function of current science But what is practicable is a function of economics and benefit–cost analysis … If ICRP were really serious about

making its recommendations less tied to utilitarian and benefit–cost criteria, then it

would recommend exposures that were as low as possible/achievable, not those that are as low as practicable.”

(Shrader-Frechette & Persson, 2002, p 155)

In practice, however, ALARA and ALARP are taken as synonyms The major difference is one of usage: In Britain where the principle is called ALARP it has a general use in workplace health and safety In countries where it is called ALARA it tends to be restricted to radiation protection

9.2 ALARA AND OPTIMIZATION IN THE RADIATION

PROTECTION SYSTEM

In 1977 the ICRP introduced a system of three basic principles for radiation protection that are still in use The three principles are:

“(a) no practice shall be adopted unless its introduction produces a positive net benefit; (b) all exposures shall be kept as low as reasonably achievable, economic and social factors being taken into account; and

(c) the dose equivalent to individuals shall not exceed the limits recommended for the appropriate circumstances by the Commission.”

(ICRP, 1977, p 3)

These principles are known under the names justification, optimization, and (individual) dose limits The combination of the three principles has been described as a “regulatory mix” that combines to provide better protection than what each of the three proposals could do alone (Lierman & Veuchelen, 2005) According to the justification principle, all radiation exposures have to be jus-tified, which is usually interpreted as meaning that the benefits (advantages) should be shown to outweigh the risks (disadvantages) The third principle (dose limits) restricts the permitted exposure of each individual But accord-ing to the second principle (ALARA), keepaccord-ing the limits is not enough Even

if exposures are below the dose limits, efforts should be made to reduce them further These further reductions in doses are usually conceived as referring to collective rather than individual doses, and therefore ALARA is often seen as a utilitarian principle (cf chapter 3) (Lierman & Veuchelen, 2006)

The terminology “optimization” for ALARA indicates that some sort of com-promise is aimed at To optimize two or more factors (here: dose and costs) means

to find the best balance between them To optimize radiation doses while tak-ing costs into account would therefore seem to mean that one finds a balance from which it would be undesirable to deviate in either direction: Higher doses should be avoided since they can cost-efficiently be reduced, and lower doses since they would involve indefensible costs As we will see, such an “optimal bal-ance” view is a common interpretation of ALARA However, there is also another interpretation, namely that the principle requires lowering of doses as far as pos-sible According to the “as low as possible” view, further reduction of the doses can never conflict with the ALARA principle The “as low as possible” view is

arguably supported by the actual wordings of the acronym; it reads “as low as reasonably achievable”, not “at the exact level that is reasonably achievable” The legal status of the ALARA principle differs between jurisdictions In Great Britain, an operator who has achieved what is considered to be an accept-able risk level may still be under an ALARA-based legal obligation to take further action to reduce exposures In the US the ALARA principle does not have such legal force (French, Bedford, & Atherton, 2005; Lierman & Veuchelen, 2006)

9.3 A THREE-LEVELLED MODEL

According to some explications of ALARA, it is only intended to be applied to the middle part of the dose range If the doses are sufficiently high, then they have to be reduced irrespective of the costs, and there is no need for consider-ations of what is “reasonable” or “practicable” On the other hand, if the doses are sufficiently low, then there is presumably no need for action It is in the intermediate region, with doses that are neither negligible nor utterly unaccept-able, that the ALARA principle will be applied The upper limit of the ALARA region in this model has been called the “action level” and its lower limit the

“inaction level” (Hendee & Edwards, 1986) Doses below the inaction level have also been referred to as “de minimis” doses This term is derived from the legal phrase “de minimis non curat lex” (law does not concern itself with trifles) In the context of risk assessment, it expresses the view that some risks are so small that we have no reason to take action against them even if such action can be taken at no or negligible cost

This three-levelled approach has been promoted in particular by the Health and Safety Executive (HSE) in Great Britain In its influential policy document

“Reducing risks, protecting people” from 2001, it divided situations involving risk into three categories: the unacceptable region, the tolerable region, and the broadly acceptable region (HSE, 2001a) An activity or practice falling in the unaccept-able region should be “ruled out unless the activity or practice can be modified to reduce the degree of risk so that it falls in one of the regions below, or there are exceptional reasons for the activity or practice to be retained” (p 42) The zone

at the opposite end, the broadly acceptable region, contains risks that “are com-parable to those that people regard as insignificant or trivial in their daily lives” and are therefore “generally regarded as insignificant and adequately controlled” The intermediate, “tolerable” region consists of risks that “people are prepared to tolerate in order to obtain benefits” (p 43) It is in that intermediate region that the HSE recommends application of the ALARA principle (or in their own terminol-ogy: the ALARP principle) This approach is illustrated in Figure 9.1

The HSE has also specified tentative limits between the three regions in terms of probabilities of fatalities The limit between the broadly acceptable and the tolerable region has been set at an individual risk of death of one in a mil-lion per year (both for occupational and nonoccupational risk exposure) Hence, risks below that level would typically be taken to be negligible and therefore not in need of ALARA-based activities (p 45) The limit between tolerable and

unacceptable risks is tentatively set at one in 1000 per year for occupational risks and one in 10000 per year for nonoccupational risks (p 46)

The idea that ALARA is only applicable above a certain “de minimis” dose

is not in obvious conformity with the standard linear no-threshold assumption according to which there is no safe dose level above zero If there is no safe level, then why should there be a level below which no efforts are made to reduce exposures? In the early 1980s this problem was discussed among three major contributors to the ICRP’s work, namely the American Harald H Rossi (1917–2000), the Swede Bo Lindell (b 1922) and the Argentinian Dan J Benin-son (1931–1994) The debate was started by Rossi who defended “de minimis”, although he conceded that there are strong reasons to believe that any dose of ionizing radiation can cause genetic damage In defense of de minimis he said:

“One stops when one has reached a level where the radiation hazard has become de minimis… It follows that a more accurate formulation of the ALARA philosophy is

that: ‘It is the obligation of those responsible for radiation protection to see to it that personal exposures are below maximum permissible limits and reduced as near as practicable to de minimis levels Further reductions are not required’.”

(Rossi, 1980)

In a reply, Lindell and Beninson claimed that the level below which no further reductions are needed is not the same in all contexts but has to be determined from the specific circumstances:

“[I]n each situation, there is a level of dose below which it would not be reasonable to

go because the cost of further dose reduction would not be justified by the additional

High risk

No risk

Tolerable region Unacceptable region

Broadly acceptable region

FIGURE 9.1 The three-leveled model of radiation protection.

eliminated detriment That level of dose, however, is not a de minimis level below which there is no need of concern, nor can it be determined once and for all for general application It is the outcome of an optimization assessment which involves marginal cost-benefit considerations … It is not reasonable to pay more than a certain amount of

money per unit of collective dose reduction, but if dose reduction can be achieved at a lesser cost even at very low individual doses, the reduction is, by definition, reasonable.”

(Lindell & Beninson, 1981)

9.4 WHAT IS “REASONABLY ACHIEVABLE?”

The key terms ALAP, ALARA, and ALARP are all vague When is a reduc-tion of radiareduc-tion doses “practicable”, “achievable” or “attainable”? Accord-ing to a strict interpretation these criteria are satisfied whenever a reduction is technically possible, irrespectively of what it would cost According to a weak interpretation these acronyms refer to what can easily be afforded In practice

an interpretation that is intermediate between these two extremes seems to be aimed at The additional term “reasonably” indicates that the strictest interpreta-tion is not intended

“Reasonable” is a common legal term that seems impossible to define in a precise manner In a penetrating analysis, Corten (1999) drew attention to two major functions that this word has in legal discourse First, it makes regulations adaptable, allowing them to be applied in different circumstances The term

is used to “introduce a degree of flexibility” in legal instruments in order to resolve “a contradiction between the essentially static character of legal texts and the dynamic character of the reality to which they apply” (p 615) The term

“reasonable” provides a legitimation for judges and administrators to interpret regulations flexibly, taking into account conditions and circumstances that the enactor of the regulations did not foresee Secondly, the notion of reasonable-ness can provide legitimacy to a legal order “by presenting an image of a closed, coherent, and complete legal system” The notion “masks persistent contradic-tions regarding the meaning of a rule, behind a formula which leaves open the possibility of divergent interpretations” (p 618)

The reasonableness incorporated in radiation protection (the “R” in ALARA) appears to have both these functions First, it provides the flexibility needed to solve potential conflicts with economic and practical constraints and objectives

In this way “the degree of risk can be balanced against time, trouble, cost and physical difficulty of its risk reduction measures” (Melchers, 2001) Secondly,

it creates the impression of a coherent and comprehensive system that is capable

of solving all potential conflicts Divergences between economic demands and the demands of health protection are presented as solvable within the system

of radiation protection, rather than having to be treated as conflicts between radiation protection and external, economic interests This “internalization” of economic compromises can of course be seen both as a way to resolve conflicts and as a way to hide them from view

Even before the notion of “reasonable practicability” was used in radiation protection, it was established in legal language as a means to express that eco-nomic considerations must be taken into account Its meaning was explained by the judge in an often quoted English court case from 1949 (Court of Appeal in Edwards vs National Coal Board):

“‘Reasonably practicable’ is a narrower term than ‘physically possible’ and seems

to me to imply that a computation must be made by the owner, in which the quantum

of risk is placed on one scale and the sacrifice involved in the measures necessary for averting the risk (whether in money, time or trouble) is placed on the other; and that if it be shown that there is a gross disproportion between them—the risk being insignificant in relation to the sacrifice—the Defendants discharge the onus on them.”

(Jones-Lee & Aven, 2011)

Five years later the House of Lords confirmed this interpretation in another case (Marshall vs Gotham Co Ltd):

“The test of what is (reasonably practicable) is not simply what is practicable as a matter

of engineering, but depends on the consideration, in the light of the whole circumstances

at the time of the accident, whether the time, trouble and expense of the precautions suggested are or are not disproportionate to the risk involved, and also an assessment of the degree of security which the measures suggested may be expected to afford.”

(Jones-Lee & Aven, 2011)

9.5 THE SCOPE OF ECONOMIC COMPROMISES

Since we do not have unlimited resources, a compromise has to be struck between radiation protection and economic considerations It is less obvious what should be the scope (aggregation level) of such compromises (Hansson,

1998; pp 106–109) As shown in Figure 9.2, there are at least four alterna-tive such scopes that one could choose between in radiation protection First,

the compromise could be struck separately for each individual workplace or company This would for instance mean that a financially strong company is required to provide its workers with better protection than a company with eco-nomic difficulties Such an interpretation of ALARA would seem to be in accor-dance with the exact phrasing of the acronym; if a company can easily afford an improvement in protection then that improvement would seem to be reasonably achievable The fact that there are other companies who cannot afford the same level of protection does not seem to be a decisive argument against it But of course, such an interpretation will be more problematic from the viewpoint of workers in the economically less fortunate companies They will receive less protection than their colleagues in the richer companies, and may have good reasons to call this difference unfair

The second scope is that of the industry or work process A choice of this

scope would for instance imply that the same degree of protection is required

of all nuclear power stations, and similarly of all industrial X-ray facilities, etc However, the requirements need not be the same for the different types of indus-try The requirements on the nuclear industry could presumably be based on what a representative such plant can afford, and similarly for other types of plants

The third scope is general exposure type We can divide radiation exposures

into a small set of major types: occupational exposure, exposure through food, medical exposure of patients, etc These types can be used to delineate scopes for radiation protection This would mean for instance that the same ments are applied to all occupational exposures, and similarly the same require-ments for all exposures through ambient air, etc

Finally, a standard for radiation protection can have all exposures as its

scope This would mean that the same standards are applied to all types of expo-sures, be they occupational or ambient

In practice, individual dose limits are applied to general exposure types Both the ICRP and national standard-setting bodies have separate exposure limits for occupational and nonoccupational exposures, the latter typically being about one order of magnitude lower In contrast, the ALARA principle is applied to the other three scopes, but usually not to that of general exposure types On some occasions, a company that can afford to decrease its exposures is required

to do so with reference to ALARA, even though other similar companies with the same problem cannot afford to do so On other occasions what is “reason-ably practicable” is judged on the level of a whole industry or work process This means for instance that the protection requirements in dentists’ offices are decided uniformly for all such offices, presumably based on what they can typically afford, and similarly for other types of workplaces Finally, attempts

Category

All

exposures

General

exposure type

Industry or

work process

Individual

workplace

Example

Any exposure

Occupational exposures

The nuclear industry

Ringhals nuclear power plant

Dose limits

ALARA

Regulatory approach

ALARA

ALARA

r

FIGURE 9.2 Different scopes (aggregation levels) for compromises between radiation protection

and economic considerations.

have been made to operationalize ALARA in a uniform way for all exposures

by means of cost-benefit analyses

9.6 ALARA AND COST-BENEFIT ANALYSIS

By cost-benefit analysis (CBA) is meant a decision-aiding technique that weighs advantages against disadvantages in numerical terms (Hansson, 2007)

In a typical CBA, the various advantages and disadvantages associated with an option are all assigned a monetary value Usually, a fixed value is assigned to the loss of a human life, and risks of losses in life are valued as fractions of that value Hence, if the loss of a life is assigned the value $7.000.000, then the value

of a risk of 1 in 1000 of an accident in which 8 people would die is

0.001 × 8 × 7.000.000 dollars = 56.000 dollars

Cost-benefit analysis has largely been used as a means to avoid excessive regu-latory demands Government agencies entrusted with the protection of humans and the environment are required to show that the monetary costs of their regu-lations are lower than the value of the resulting gains in risk reduction This way

of thinking may seem to be quite different from that of ALARA, but in particu-lar in the USA the ALARA principle has often been interpreted as a requirement that dose reductions be optimized with the help of cost-benefit analysis

According to Kathren, Munson, and Higby (1984), in the tolerable region (“ALARA region”) as depicted in Figure 9.1, “the value of a person-rem is con-stant” Below that region, the value of a person-rem “tends to zero”, whereas above it that value “increases sharply” This means that in its area of application the ALARA principle is “treated as being simply a restatement of the standard cost-benefit criterion that from the point of view of social welfare maximization

a safety project should be undertaken only if its costs do not exceed its benefits” (Jones-Lee & Aven, 2011)

In Britain the Health and Safety Executive (HSE) has chosen to explicate ALARA in terms of cost-benefit analysis, but with another method that puts higher demands on safety If cost-benefit analysis is applied in the standard way, then safety obligations are satisfied when a level has been reached where the costs of further improvements would be larger than the calculated gains But instead of this standard criterion, the HSE applies what they call a “test of gross disproportion” According to that test, safety obligations are only satisfied when

the costs of further improvements would be much larger than the calculated

gains (HSE, 2001a, p 67) In the agency’s own words:

“[A] computation must be made in which the quantum of risk is placed on one

scale and the sacrifice, whether in money, time or trouble, involved in the measures necessary to avert the risk is placed in the other; and that, if it be shown that there

is a gross disproportion between them, the risk being insignificant in relation to the sacrifice, the person upon whom the duty is laid discharges the burden of proving that compliance was not reasonably practicable.” (p 62)

According to the HSE, the extent of this “bias” toward safety differs between different contexts In each particular case it “has to be argued in the light of all the circumstances applying to the case”, including the needs that there may be

to apply a precautionary approach (p 67) In another document, the HSE intro-duced a numerical specification of this type of bias toward safety:

“In any assessment as to whether risks have been reduced ALARP, measures to reduce risk can be ruled out only if the sacrifice involved in taking them would be grossly disproportionate to the benefits of the risk reduction …[W]e believe that the greater the

risk, the more that should be spent in reducing it, and the greater the bias on the side of safety This can be represented by a ‘proportion factor’, indicating the maximum level

of sacrifice that can be borne without it being judged ‘grossly disproportionate’.”

(HSE, 2001b)

In 2006 the British railway inspectorate specified such proportion factors (also called “disproportion factors”) in numerical terms These factors are intended to

be applied to the “value for preventing a fatality” (VPF), which is essentially a more palatable term for what cost-benefit analysts usually call a “value of life” The inspectorate noted that the disproportion factors applied in practice by the HSE were in general around 1–2 in cases with a very low baseline risk (i.e close

to the “broadly acceptable” region in Figure 9.1) and around 10 at very high baseline risk (i.e close to “unacceptable” in the same diagram) Based on this they proposed the following rules of thumb:

low baseline individual risk and no societal risk: disproportion factor 1–2 low baseline individual risk and societal risk: disproportion factor 3

high baseline individual risk: disproportion factor 3–10 depending on the level

of individual risk (HMRI, 2006)

The recommendation is to multiply the VPF with the appropriate disproportion factor and then use this augmented VPF in comparisons with the costs This use

of disproportion factors will have essentially the same effect as using higher VPFs (or “values of life”) than what are commonly used in cost-benefit analy-sis It is an open question whether this calculative approach corresponds to the meaning of the acronyms ALARA and ALARP

9.7 RELATED PRINCIPLES OF PROTECTION

Several principles that are used in other areas are quite close in meaning to

ALARA One of the more important of these is best available technology (BAT)

that is used in several jurisdictions to promote efficient pollution-limiting tech-nologies Just like ALARA, BAT is usually used in combination with a numeri-cal limit, e.g an effluent limit It has the function of requiring further reductions below that limit to the extent that this is practically possible Just like ALAP, the earliest version of ALARA, BAT has a wording that seems to require reduc-tions at any price, but in practice it has been applied in ways that take economic