The HSE have examined the concepts of acceptability and tolerability of risk in some detail in their document ‘Reducing Risks, Protecting People’, 2001.
Acceptability does not necessarily mean tolerability. A dictionary denition of ‘accept’ includes
‘agree to’, whereas the dictionary denition of ‘tolerate’ includes ‘put up with’. Clearly agreeing to the presence of a particular risk and putting up with a particular risk are different concepts.
Arguably acceptability relates to the willingness to accept the presence of a particular risk to secure certain benets to tolerate a risk implies that the individuals who are at risk do not regard the presence of the risk as being a fact of life or negligible but some thing which needs to be regularly reviewed and controlled.
For example, most people are undeterred from using the road and car as a means of transport despite learning that over 3,000 people are killed each year by trafc.
The view of risk varies signicantly depending on whether the individuals are capable of judging the extent of the hazard by experience or whether there is a lack of understanding from the cause or the presence of the danger or whether there is a large dread factor in terms of the consequence of realising risks. A lack of understanding therefore can lead to a lack of tolerance as a result of dread.
In many circumstances the risk assessor looks at the hazard associated with a situation or event, while the public may look at the outrage involved. This is not a misperception of risk, simply a different way of dening a particular risk. Perception of risk may be affected by factors such as:
▪ Who controls the risk;
▪ Risk transfer or substitution;
▪ Naturally occurring hazards;
▪ Risk familiarity / dread;
▪ Benets to individual / society;
▪ The proximity of the risk;
▪ The level of technology required to control the risk;
▪ Condence in control measures;
▪ Whether the alternatives are worse;
▪ Whether danger money is paid; and
▪ Local or media interest.
Hazards giving rise to concerns can be put into two broad categories:
▪ Individual Concerns
How individuals see the risk from a particular hazard affecting them and things they value personally. This is not surprising since one of the most important questions for individuals incurring a risk is how it affects them, their family and things they value. Though they may be prepared to engage voluntarily in activities that often involve high risks, as a rule they are far less tolerant of risks imposed on them and over which they have little control, unless they consider the risks as negligible. Moreover, though they may be willing to live with a risk that they do not regard as negligible, if it secures them or society certain benets, they would want such risks to be kept low and clearly controlled; and
▪ Societal Concerns
The risks or threats from hazards which impact on society and which, if realised, could have adverse repercussions for the institutions responsible for putting in place the provisions and arrangements for protecting people, e.g. Parliament or the Government of the day.
This type of concern is often associated with hazards that give rise to risks which, were they to materialise, could provoke a socio-political response, e.g. risk of events causing widespread or large scale detriment or the occurrence of multiple fatalities in a single event. Typical examples relate to nuclear power generation, railway travel, or the genetic modication of organisms.
Hazards giving rise to societal concerns share a number of common features. They often give rise to risks which could cause multiple fatalities; where it is difcult for people to estimate intuitively the actual threat; where exposure involves vulnerable groups, e.g. children; where the risks and benets tend to be unevenly distributed - for example, between groups of people with the result that some people bear more of the risks and others less, or through time so that less risk may be borne now and more by some future generation. People are more averse to those risks and in such cases are therefore more likely to insist on stringent Government regulation.
The opposite is true for hazards that are familiar, often taken voluntarily for a benet, and individual in their impact. These do not as a rule give rise to societal concerns.
Nevertheless, activities giving rise to such hazards (for example, bungee jumping) are often regulated to ensure that people are not needlessly put at risk.
In dealing with societal risk the term outrage is often used to describe the public’s reaction, based on a number of subjective, personal factors. These factors can be summarised in a series of questions about the potential hazard
Table 6: Outrage Factors
High Outrage Low Outrage
1. Coerced 2. Industrial 3. Exotic 4. Memorable 5. Dreaded
6. An Emergency 7. Not Knowable
8. Controlled by Others
9. Process is not Responsive
10. Done by Someone Unknown or not Trusted
1. Voluntary 2. Natural 3. Familiar 4. Nondescript 5. Not Dreaded 6. Chronic 7. Knowable
8. Controlled by the Individual 9. Process is Responsive 10. Done by Someone Trusted
If the words in the rst column best describe the hazard, then the public outrage is likely to be high. Regardless of what the assessors believe, the public will perceive the hazard as being associated with a high risk. If, however, the words in the second column best describe the hazard, then the outrage is likely to be low.
Where risks are not so clearly dened, risk communication and consultation are important.
Radon provides a good example of a situation where the public has a low outrage level where assessors consider that there is a high hazard level, while the electro-magnetic ux controversy provides an example of high public outrage and current low hazard estimates by assessors.
Methods to overcome public concerns about risks include providing information, education and propaganda, carrying out a quantied risk assessment and emphasising the level of risk rather than the hazard severity, risk comparison, highlighting local and societal benets, demonstrating legal and best practice and acceptance by regulatory bodies.
Reducing Risks Protecting People 2001, describes the framework for tolerability of risk following HSE research which numerically valued the risk and tolerability as shown in Figure 13. (HSE, 2001)
Figure 13: HSE Framework for the Tolerability of Risk
Unacceptable region
The ALARP or Tolerability region (risk is undertaken only if a benefit is desired)
Risk cannot be justified save in extraordinary circumstances
Tolerable only if risk reduction is impracticable or if its cost is grossly disproportionate to the improvement gained
Tolerable if cost of reduction would exceed the improvement gained
Necessary to maintain assurance that risk remains at this level Broadly acceptable
region (No need for detailed working to demonstrate ALARP)
ALARP = As Low As is Reasonable Practicable