Comparison risk analysis

The process by which the results of a risk analysis (i.e., risk estimates) are used to make decisions, either through relative ranking of risk-reduction strategies or through comparison with risk targets... 

In the final phase of risk analysis—risk characterization—one integrates outputs of effects and exposure assessments. Risk is expressed in qualitative or quantitative estimates by comparison with reference values (e.g., hazard quotient). The severity of potential or actual damage should be characterized with the degree of uncertainty of risk estimates. Assumptions, data uncertainties and limitations of analyses are to be described clearly and reflected in the conclusions. The final product is a report that communicates to the affected and interested parties the analysis findings (Byrd and Cothern, 2000). 

Table 19 Comparison of different risk analysis methods. 

Lofstedt, R. and Vogel, D. (2001) The changing character of regulation a comparison of Europe and the United States. Risk Analysis 21(3) 393-402. 

A further divide between risk analysts arises between realism and constructionism, but this debate can be seen as unifying positivist and relativist approaches. Constructionism considers how social and cultural perspectives influence risk definitions and interpretations [12]. In comparison, realists exclude social and cultural phenomena in their reference of risk, but do acknowledge their existence [12]. Constructionism resembles constrained relativism and does not represent the paradigms of the unconstrained relativists. For positivists and realists, acknowledging risk perceptions provides a potential framework to incorporate the risk perceptions into their process of risk analysis because risk perceptions can be subject to scientific analysis as social phenomena. 

Kraus N, Malfors T, and Slovic P (1992) Intuitive toxicology A comparison of expert and lay judgements of chemical risks. Risk Analysis 12 215-232. 

Risk analysis and comparison is very difficult due to the high concern of radiation exposure. It is advisable to contact USACHPPM or other trained Nuclear Medical Science Officers for guidance before making any risk analysis for radiation. The BEIRV committee estimated that the risk of dying of cancer for a low-level exposure to radiation is about 8% per sievert or 0.08% per rem or roughly 10 4 per mrem. 

This chapter presents the basic concepts and definition of risk (Section 3.1), a protocol for conducting transportation risk assessments (Section 3.2), and a prioritization process for identifying important issues and transportation scenarios requiring a more detailed risk analysis (Section 3.3). Due to the differences in safety and security definitions and risk assessment methodologies, the focus of Chapters 3, 4, and 5 is limited to transportation safety. Security concepts, definition, and assessment methods are presented separately in Chapter 6, with this chapter providing a high-level comparison of safety and security. 

The site-level health and safety manager was given notice from corporate for the need to conduct the qualitative risk analysis of the plant s hazardous material transportation operations. The safety manager was provided with a questiotmaire regarding all chemicals of concern, shipping quantities, modes of transit, and the route characteristics (similar to the checklist found in Table 4.2). This information was transmitted back to corporate for analysis, which included a corporate-level comparison to the other XYZ Chemical facihties risk results. Based on the information collected at the site level, the following was determined and reviewed by corporate for this facility ... 

Once the specific issues and scope of the analysis are defined, a semi-quantitative risk assessment may be conducted using either risk indexing or a risk ranking matrix. The risk indexing and risk matrix techniques should be built on the information from the earlier analyses. Each level of risk analysis should not be considered a separate effoit, but a continued understanding of the transportation issue. Additionally the information gained from these activities can be used to update the qualitative analysis, especially benchmarking comparisons. 

Similar to the process defined for semi-quantitative risk analysis in Chapter 4, quantitative risk is a function of consequence and likelihood. Decisions are made regarding the resnlting risk level and the need for additional risk mitigation based on a comparison of the resnlts to a set of criteria. The QRA process is illustrated in Figure 5.1. The differences between a QRA and the other simpler techniques are ... 

In addition to the risk reduction benefits, the costs of risk mitigation options need to be evaluated. Due to the uncertainties associated with semi-quantitative and quantitative risk analysis results, a relative risk comparison, as compared to absolute measures of risk and benefits, is recommended. To conduct this type of relative comparison, incremental risk analysis can be used to evaluate the cost effectiveness of risk mitigation options, or determine the optimal combination of risk mitigation options. Figure 7.4 illustrates example results of this type of analysis, and uses the options from the F-N curve in Figure 7.3 as the basis for comparison. 

Qualitative Risk Analysis Based primarily on description and comparison nsing historical experience and engineering jndgment, with httle quantification of the hazards, consequences, likelihood, or level of risk. 

Hattis D, White P, Koch P. 1993. Uncertainties in pharmacokinetic modeling for perchloroethylene II. Comparison of model predictions with data for a variety of different parameters. Risk Analysis 13(6) 599-610. 

Such a multidimensional risk analysis is especially suitable for the comparison of chemical substances with a common scope of application. Since the imidazoHum ILs under investigation are being used as alternatives for conventional organic solvents, a first screening risk comparison of two selected substances with the common solvent acetone is presented here as a preliminary example. The chosen substances are l-butyl-3-methylimidazolium tetrafluoroborate ([BMIM] [BFJ) and l-decyl-3-methylimidazoHum tetrafluoroborate ([DMIM] [BF4]), one for its abundance in organic synthesis literature, the other for its increased toxicity (see below). 

Comparisons with Traditional Programmatic Risk Analysis Techniques... 

The NASA analysis did not include a causal analysis of the risks and thus no comparison is possible. Their goal was to determine what should be included in the upcoming ITA risk assessment process and thus was narrower than the STAMP demonstration risk analysis effort. 

Another informal comparison was made in the ITA (Independent Technical Authority) analysis described in section 8.6. An informal review of the risks identified by using STPA showed that they included all the risks identified by the informal NASA risk analysis process using the traditional method common to such analyses. The additional risks identified by STPA appeared on the surface to be as important as those identified by the NASA analysis. As noted, there is no way to determine whether the less formal NASA process identified additional risks and discarded them for some reason or simply missed them. 

Another issue regarding RAC is the influence of imcertainty. The results of risk assessments will always be associated with some imcertainties, which may be linked to the relevance of the data basis, the models used in the estimation, the assumptions, simplifications or expert judgements that are made. This uncertainty will be reduced as the development work progresses. NORSOK Z-013 states that the comparison to RAC should usually be made in relation to best estimate from the risk analysis rather than to some level of confidence. 

The aim of the present study was to investigate the effectiveness of passive protections of tankers in the reduction of the overall risk due to LPG road and rail transportation. In the first part of the study (Section 2) the effect of the thermal protection on the time to BLEVE was analyzed. In the second part of the study (Section 3), the results obtained were used to investigate the potential effect on risk due to the reduction of the probability of the fired BLEVE, following the adoption of the road tanker coating. A case-study derived from actual LPG road transportation scenario in Europe was analyzed, and a Transport Risk Analysis (TRA) was performed. Thus, TRA results allowed to widen the economic aspect of this issue (Section 3). Costs were identified and assessed considering also the amortization and taxes, while benefits were assessed taking into account the risk reduction as a number for life loss reduction. Finally, the comparison between costs and benefits provided an evaluation of the economic impact connected with the adoption of passive fire protections of tankers. 

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