Risk decision table

Risk Analysis Another group of methods used in system safety involve risk analysis. In many cases, the hazards are charted into a risk decision table or risk assessment matrix (see Figure 6.5). The severity of hazards is rated and charted on one axis of the chart. The probability of occurrence is on the other axis. Then severity-probability cells are marked for the kind of action required, such as risk reduction required, management approval, or that the operation is permissible. 

In making an effort to miderstand the significance of risk analyses, it is helpful to place tlie estimated risks in tlie same perspective as otlier everyday risks tliat have been determined by a similar inctliodology. Table 18.7.1 lists a nmnber of risks for comparison. These have been derived from actual statistics and reasonable estimates." " People often overestimate tlie frequency and seriousness of dramatic, sensational, dreaded, well-publicized causes of death and miderestimate the risks from more familiar, accepted causes tliat claim lives one by one. Indeed, risk estimates by "experts and lay people (or "the public ) on many key enviromiieiital problems differ significantly. This problem and the reasons for it are extremely important because in our society the public generally does not trust experts to make important risk decisions alone. 

The proposed systems framework for EU decision-making under REACH seeks to counterbalance the weaknesses and to draw on the strengths of the national approaches while addressing the points shown in Table 7.1. Specifically, the framework would fuse hazard, technical and risk-benefit approaches to risk management (Table 7.2). Compared with the current process of chemical legislation and the recent REACH proposal, the systems framework would avoid a linear substance-by-substance approach by applying a set of decision-making rules based on hazard and use to all chemicals (Section 5.3.1). 

Earlier in this chapter, reference was made to a speaker who reviewed the hazard analysis and risk assessment methods used in his company, which relied on typical risk assessment and decision-making matrices, to achieve acceptable risk levels. Use of such matrices is a method some organizations apply to arrive at acceptable risk levels. Table 15.1 is an example of such a risk assessment matrix. Using the results from Table 15.1, levels of remedial action or risk acceptance for individual risk categories can be established, as in Table 15.2. 

The decision table shown is the simplest possible it can be made more complex if an higher level of detail is used in the classification of a risk in terms of severity and probability we tend to keep for each project the classification of risks as detailed as the classificatian of defects. 

Step f considers all of the background information discussed in Section 2.f. If the information requirement is based on a regulatory concern or a special purpose need, then Steps 2 through 5 are bypassed and a QRA should be performed. If the information is needed for decision making, you must determine whether the significance of the decision warrants the expense of a QRA. If not, you may be able to use less resource-intensive qualitative approaches to satisfy your information requirements. Table 8 contains examples of typical conclusions reached from qualitative risk analysis results. 

Quantitative risk analysis is subject to several theoretical limitations. Table 13 lists five of the most global limitations of QRA. Some of these may be relatively unimportant for a specific study, and others may be minimized through care in execution and by limiting one s expectations about the applicability of the results. However, you must respect these limitations when chartering a QRA study and when using the results for decision-making purposes. 

Table 18.4.1 smiinuuizes another inetliod of risk assessment tliat can be applied to an accident system failure. Both probability and consequence have been ranked on a scale of 0 to 1 witli table entries being the sum of probability and consequence. The acceptability of risk is a major decision and can be described by dividing tlie situations presented in Table 18.4.1 into unacceptable, marginally acceptable, and acceptable regions. Figiue 18.4.2 graphically represents tliis risk data. ... 

The calculated MOEs in Table 3 demonstrate some of the problems with using this approach for characterizing risks and making regulatory decisions. Several of the exposure scenarios have MOEs of less than 10, which is the... 

If an analytical test results in a lower value x, < x0, then the customer may reject the product as to be defective. Due to the variation in the results of analyses and their evaluation by means of statistical tests, however, a product of good quality may be rejected or a defective product may be approved according to the facts shown in Table 4.2 (see Sect. 4.3.1). Therefore, manufacturer and customer have to agree upon statistical limits (critical values) which minimize false-negative decisions (errors of the first kind which characterize the manufacturer risk) and false-positive decisions (errors of the second kind which represent the customer risk) as well as test expenditure. In principle, analytical precision and statistical security can be increased almost to an unlimited extent but this would be reflected by high costs for both manufacturers and customers. 

Table 3 describes the main parts of an environmental risk assessment (ERA) that are based on the two major elements characterisation of exposure and characterisation of effects [27, 51]. ERA uses a combination of exposure and effects data as a basis for assessing the likelihood and severity of adverse effects (risks) and feeds this into the decision-making process for managing risks. The process of assessing risk ranges from the simple calculation of hazard ratios to complex utilisation of probabilistic methods based on models and/or measured data sets. Setting of thresholds such as EQS and quality norms (QN) [27] relies primarily on... 

Priority substances were selected, which are considered to be of particular concern to human health and/or the environment. The suppliers of these priority substances had to provide any missing studies to complete a EU notification Base Set (Table 1). A rapporteur Competent Authority evaluates the full review dossier on behalf of the EU. The final output is a risk assessment (see Section 14), with final recommendations on how to deal with the substance i.e., it may be of no concern, require risk reduction or restriction, or further data may be needed before a decision is made. 

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