Acceptable risk compared

Starr, 1969 approached this by investigating the "revealed preferences exhibited in society ls the result of trial and error. (Similar to the "efficient market theory" in the stock market.) Stan-conjectured that the risk of death from disease appears to determine a level of acceptable voluntary risk but that society requires a much lower level for involuntary risk. He noted that individuals seem to accept a much higher risk (by about 1000 times) if it is voluntary, e.g., sky-diving or mountain climbing, than if it is imposed, such as electric power or commercial air travel, by a correlating with the perceived benefit. From this study, a "law" of acceptable risk was found concluding that risk acceptability is proportional cube of the benefits. Figure 1.4.4-1 from Starr, 1972 shows these relationships. One aspect of revealed preferences is that these preferences do not necessarily remain constant (Starr et al., 1976). In Starr et al., 1976, it is shown that while nuclear power has the least risk of those activities compared, it also has the least perceived benefit. Clearly the public thinks that... 

Risk characterization for non-threshold effects, e.g., for chemicals that are both genotoxic and carcinogenic, generally proceeds by comparing the acceptable risk level (Section 6.2.4) with the actual or estimated total daily intake. An alternative, new approach is the margin of exposure approach (Section 6.4). 

Through some form of risks assessment it is possible to obtain a measure of the absolute or relative magnitude of the risks posed. However, there is no standard form of risks assessment methodology or a generally accepted standard for what is an acceptable risk, not are all or most of the data required for risk assessment likely to be available. Moreover, neither is it obvious, or generally agreed upon, as to how to compare fundamentally different types of risk posed by hazardous waste, such as acute versus chronic health effects and environmental damage versus health effects. 

The enterprise analyzes and compares the established requirements baseline against enterprise and project constraints to ensure that the technical requirements correctly represent, and stay within, enterprise and project policies and procedures, acceptable risk levels, plans, resources, technology limitations, objectives, decisions, standards, or other documented constraints. 

To set the new pipeline safety zone range we should compare individual risk from gas pipeline with acceptable risk levels. This can be done using geographical information systems, where we display individual risk iso-curves on a map and than we mark spatial continuous area with risk level higher than acceptable risk level, see Fig. 3. 

The ambient exposure concentration (AEC) of PAH in soil was compared with the published toxicolog-icaUy effective concentration (TEC). The value of the detected non-dimensional hazard quotient (HQ) is either lower or higher than 1 and represents the situation with either acceptable or non-acceptable risk requiring further assessment. 

There are minor differences between the two decision processes. The SSCl is determined in a more qualitative way by using two factors, i.e. hazard severity and software autonomy. The SIL should he determined in a quantitative probabilistic way by computing the risks of the system and comparing with accepted risk levels. Thus the necessary risk reduction is determined which in tun determines the rehahhity requirement for the safety function. Risk graphs (see section 2.2) and risk maps are rather considered as qualitative estimation methods by lEC 61508. Finally we mention that the AOP 52 presents in chapter 11 in total 6 case studies where 3 are taken fi om the ammunition domain. Such specific examples are not available in the lEC 61508. 

On the basis of statistical data on risk of death in the United States, C. Starr [9-18] tried to provide a quantitative view off the difference in readiness in the case of voluntarily accepted as compared to imposed risks. 

Acceptable Risk An acceptable level of risk for regulations and special permits is established by consideration of risk, cost/benefit and public comments. Relative or comparative risk analysis is most often used where quantitative risk analysis is not practical or justified. Public participation is important in a risk analysis process, not only for enhancing the public s understanding of the risks associated with hazardous materials transportation, but also for insuring that the point of view of all major segments of the population-at-risk is included in the analyses process. 

Comparable statements and definitions appear in much of the current literature on risk and acceptable risk. One resource has been chosen for citation here because of its broad implications. The following excerpts are taken from the Framework for Environmental Health Risk Management (1997) issued by The Presidential/Congressional Commission on Risk Assessment and Risk Management. 

Never look at the risk expectation value as an absolute final number. It is only to be used to compare risks. The risk number is a relative number, relative to other risks. The risk number should never stand alone. If you say the risk of a fire in your plant is 1.5 x 10 , you will be in an endless battle trying to prove it is 10 and not 10 , and you will never win. A better approach is to use risk profiles and compare your plant fire risk with other known, accepted risks. 

Prioritize hazards and associated risks by potential impact. The risk assessment combines the impact of all hazards and risk, comparing them against defined criteria as to what is acceptable. 

The Standard requires manufacturers of electro-medical equipment to have a formal risk management system in place. Manufacturers must estimate the risks relating to their device and take action dependent upon how that risk compares to predefined levels of acceptability. There are objective pass/fail criteria and one may choose simply to follow such requirements in the design of their device. 

Passengers on trains are, in a sense, riding voluntarily, but they are certainly not in control of the situation. People are less willing to accept risk when they put their lives in the hands of an airline pilot or locomotive engineer than when they are behind the wheel of their own automobile. Jones-Lee and Loomes (1995) found that subway travelers in London place a risk premium of fifty percent on subway travel compared with automobile travel. 

The remaining step in the hazard identification and risk assessment procedure shown in Figure 1 is to decide on risk acceptance. For this step, few resources are available and analysts are left basically by themselves. Some companies have formal risk acceptance criteria. Most companies, however, use the results on a relative basis. That is, the results are compared to another process or processes where hazards and risks are weU-characterized. 

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