Risk acceptability, discussion

The somewhat controversial theory of risk homeostasis is relevant to a discussion of risk taking. RHT was developed initially in the area of driving behavior (Wilde, 1984). The theory states that accident rates are not determined by actual levels of intrinsic risk but by the levels of risk acceptable to individuals in the situation. The theory implies that people adjust their risk-taking behavior to maintain a constant level of perceived risk. Thus, if improved safety measures are introduced (e.g., better guarding, improved protection systems then individuals will behave in a more risky fashion in order to maintain their accustomed levels of risk. 

Ultimately, the credibility—for scientists, stakeholders and society in general—of the data and assessments on which critical risk management decisions are based owes much to the underlying tenets of data quality discussed in this document. Credibility is a basic element of risk communication and social trust and, in turn, is a determining factor in risk acceptance and risk management. 

The NRC document calls for hazard identification, dose-response assessment, exposure assessment, and risk characterization. In an effort to place descriptive experimental toxicity results in a clearer perspective and place more emphasis on evaluation, this outline deviates slightly from the NRC document and calls for hazard evaluation, hazard extrapolation, exposure assessment and risk characterization. In addition, a few comments on risk acceptability are given. Exposure assessments have been adequately discussed elsewhere in this symposium and will be discussed here only as they relate to hazard identification, evaluation, extrapolation and risk characterization. 

Risk matrices (discussed below) can be used to set the boundaries of acceptable and unacceptable risk. The middle squares in such a matrix represent the risk levels that are marginally... 

An acceptable risk level for structures must be related to the basic risk accepted by all people in a society. Tliis basic risk is that which is beyond th individuals direct control. In modern times it has been the duty of govermeni through various safety controls, to regulate this hazard at an acceptable level fo society as a whole. The choice of an acceptable risk level will be affected by th special importance of structures in society as previously discussed, but must b clearly distinguished from the risk levels that an individual is prepared to tolerat when he is in control of what he is doing (for example mountaineering). 

However, there has also been some discussions about the suitabihty of risk acceptance criteria to assess and control risks, see Aven and Vinnem (2005). One concern is that the introduction of pre-determined criteria may give the wrong focus to risk assessment activities, i.e., on meeting risk criteria rather than on obtaining overall safe and cost-effective solutions and measures. 

The use of risk acceptance criteria is, despite the critique raised to this approach, one possible approach to ensure that safety is reasonable accounted for. Common practice in Norway is that the enterprises themselves define the RAC even in the case of societal risk. This practice has been questioned, and a broader principal discussion is on the way in Norway. The recent developments in the UK and the Netherlands in relation to land-use planning are believed to also improve the Norwegian thinking. 

In the practice of modem system safety analysis, the system safety engineer attempts to provide a sufficient level of information to organizational management so that informed decisions may be made regarding hazard risk acceptance or rejection. In the safety and health arena, the provision of such choices often requires ample substantiation in order to justify decisions to accept a hazard risk. The system safety practitioner can utilize a wide variety of techniques and methods to determine risk levels and, through preestablished acceptance criteria, make recommendations to management. These analytical tools serve to qualify the risk in relation to some existing level and/or standard of operation. Some of the more common of these tools are discussed in detail in Part II of this text. When acmal failure rate data are known or can be determined or deduced, the system safety effort can take the analysis process further and actually quantify the risk of hazard in terms of these known or expected failure rates. 

In the context of this textbook legislation is discussed that affects preparation in pharmacies, mainly concerning exposure to chemical substances. Legislation provides the logic for determination of safe levels , for which risk acceptance by Society takes part. 

ZlO-2005 tersely states its purpose in Section 1.2 as follows The primary purpose of this standard is to provide a management tool to reduce the risk of occupational injuries, illnesses, and fatalities. This question logically follows. What risk reduction level is to be achieved This chapter Establishes that achieving a zero risk level is unattainable Discusses the great variations in cultural and situational aspects of risk acceptance and Combines the elements of risk (probability and severity) with ALARP (as low as reasonably practicable) to arrive at a definition of acceptable risk, the operational goal. 

It was found, however, that application of the model method to data of the past shows model-contrary inconsistencies in the population s attitude toward risks. This was explained by means of the difference between objective risk, which is the deciding quantity in Starr s model, and perceived risk. Neither does the risk perception remain constant for the old risks nor can the difference between objective risk and subjective risk perception be neglected in the case of new risks . Though the revealed reference model is therefore subject to criticism as an acceptance-prediction model, the risk-acceptance comparison which can be obtained with the help of this model is suited as an argumentum ad hominem in public discussion. 

Some Safety Case reports contain an as low as reasonably practicable (ALARP) demonstration section that shows how the identified major hazards have been managed such that the associated level of risk is acceptable. The vexed topics of ALARP and acceptable risk are discussed in Chapter 1. 

Understanding cost effectiveness has become a more important element in risk acceptance decision making. That brings the discussion to ALARA and ALARP. 

Risk-acceptance criteria are used as a reference in evaluating the results of the risk analysis and in determining the needs of remedial actions. They therefore have to be available prior to the start of the analysis. There are many different types of risk acceptance criteria, see NORSOK standard Z-013 for an overview (Norsk Standard, 1996/97/98/99). Here we will use acceptance criteria related to the risk of fatality or injury to personnel. They must meet the same standards as those of the SHE performance indicators discussed in Section 11.1. In other words, they must be ... 

I have also been dependent on many people for source input to the book. I have used examples from the project work of my students at NTNU. Here I especially want to mention Gro Blindheim, Borge Godhavn, Bjornar Andre Haug, Jorn Lindtvedt, Vidar Tuven and Elisabeth Wendel. Karsten Boe at Norsk Hydro has been my discussion partner in the area of risk acceptance criteria. Bengt Elf at ASG Road Transport, Lennart Svensson at Volvo Lastvagnar AB and Thomas Lekander at the Swedish National Road Administration have helped me with input to the chapter on traffic safety. 

LindeU s work discussed the fact that people do not take information from expert sources at face value and introduced a need to consider both information about earthquake risk and preparedness and the qualify of the (communication) relationship between the sources and recipients of earthquake risk information. An important contextual element of this relationship is that it occurs under conditions of uncertainty. People may have no or limited experience of earthquakes, and the infrequent nature of earthquake activity makes it impossible for them to independently test the validity of the information about risk and preparedness. Under these circumstances, an important aspect of the relationship between source of information and its recipients is the degree to which recipients trust sources of information. Levels of risk acceptance and people s willingness to take responsibility for their own safety is increased, and decisions to take steps to actively manage their risk more likely, if people believe that their relationship with risk management agencies is fair and empowering (e.g., agencies are perceived as trustworthy, as... 

At first sight, the procedure appears to be valid not merely for evaluating but also encouraging risk acceptance. However, increasingly often no practical alternative is available or seems acceptable to the public or a particular pressure group. Frequently, the comparison is based on unproven or uneconomic technology, or merely alternative proposals are not considered in the discussion. 

The norms, beliefs, and procedures that affirmed risk acceptability in the SRB Work Group were a part of the worldview that many engineers brought to the teleconference discussion. What had previously been an acceptable risk was no longer acceptable to many Thiokol engineers. The Five-Step decision sequence was initiated a final—and fatal—time, but with one alteration it was followed not by a successful launch, but by a failure. 

Most of these methods are commonly employed in the downstream processing of the desired ceU culture technology product. Hence, most of the time it is only necessary to demonstrate that the designed process is reducing the putative risk factors to acceptable levels. Validation methods employed for risk reduction are discussed in the Hterature (25). 

The case studies that follow have mainly come from live product development projects in industry. Whilst not all case studies require the methodology to predict an absolute capability, a common way of applying CA is by evaluating and comparing a number of design schemes and selecting the one with the most acceptable performance measure, either estimated Cp, assembly risk or failure cost. In some cases, commercial confidence precludes the inclusion of detailed drawings of the components used in the analyses. CA has been used in industry in a number of different ways. Some of these are discussed below ... 

Toxicologists tend to focus their attention primarily on c.xtrapolations from cancer bioassays. However, tlicrc is also a need to evaluate the risks of lower doses to see how they affect the various organs and systems in the body. Many scientific papers focused on tlic use of a safety factor or uncertainty factor approach, since all adverse effects other than cancer and mutation-based dcvclopmcnUil effects are believed to have a tlu cshold i.e., a dose below which no adverse effect should occur. Several researchers have discussed various approaches to setting acceptable daily intakes or exposure limits for developmental and reproductive toxicants. It is Uiought Uiat an acceptable limit of exposure could be determined using cancer models, but today tliey arc considered inappropriate because of tlircsholds. ... 

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