Risks evaluation

Risk evaluation is the apparently simple task of comparing an estimate of intake with the ADI. If intakes are below the ADI then there is virtually no risk whereas if they exceed the ADI then some risk management action may be required. In practice risk evaluation is a far less certain science. 

A vital and often over-looked aspect of risk evaluation is ensuring that the estimate of intake corresponds to the PTWI so that like is being compared with like. For example, toxicological end-points are frequently time-related. On rare 

It is advisable that a risk register should be compiled in order to provide an overview of these matters. Such a register should mainly comprise the identified risk and a number to assign to it, the risk owner, the risk manager, the description and cause of the risk, its categoiy, the safeguards in place and what other measures could be employed so as to mitigate the threat. 

Throughout this chapter, reference will be made to annual fatality risks expressed as a probability. To provide a frame of reference here are some railroad fatality probabilities  

Working as a train crew member for one year (based on average fatality rate for 1990-6) 

Crossing a highway crossing with passive warning devices twice a day for a year  

Once the risks have been analyzed and risk scores determined, it is now possible to do a risk evaluation. A risk evaluation is a quantification of the risks at hand and an evaluation of the cost of risk reduction and benefits derived from reducing or eliminating risks. It is basically a cost-benefit analysis to determine which risks can be reduced, the benefit of risk reduction, and the cost of reduction. 

One of the main objectives of risk evaluation is to enable managanent to take decisions on which risks should receive priority and where risk control efforts shonld be directed. 

By taking the risk score, equating it with the percentage of risk reduction, and comparing the cost of risk reduction to the benefits, a thorough evaluation can be made of whether or not the risk reduction justifies the effort. 

For example, it may cost a lot of money to improve the instrumentation on a control circuit. The cost of reducing this risk would not be justified because the possibility of an undesired event occurring due to the instrumentation is extremely slight and the consequence of the risk would be a minimal interruption only. 

In every walk of life there is a certain amonnt of risk. The same can be said for manufacturing and mining processes. It is virtnally financially and physically impossible to eliminate all risks from all walks of life and, therefore, we accept a certain amount of risk as part of onr day-to-day living. Safety has been defined by some as acceptable risk.  

These four steps of generating knowledge and insights provide the data and information base for the next step risk evaluation. 

FIGURE 1.2 Areas of acceptable, tolerable and intolerable risks (adopted from Renn 2008, p. 150). 

When you can measure what you are speaking about and express it in numbers, you know something about it. 

A witty statesman said, you might prove anything by figures. 

Nature Addresses and Lectures, 1841 Ralph Waldo Emerson 

As we all know, international trade has increased incredibly in the last few decades with the advent of the European common maiket (especially the Maastricht Treaty), the North American Eree Trade Agreement, various regional trade agreements in Asia, the common maiket in South America (Mercosur), and various other smaller agreements. With the large cross border traffic and even the internationalization of the engineering profession, risk assessment becomes aitical to assuring a safe and cost-effective operation. 

System Safety Engineering and Risk Assessment A Practical Approach 

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A common risk evaluation and presentation method is simply to multiply the frequency of each event by consequence of each event and then sum these products for all situations considered in the analysis. In insurance terms, this is the expected loss per year. The results of an uncertainty analysis, if performed, can be presented as a range defined by upper and lower confidence bounds that contain the best estimates. If the total risk represented by the best estimate or by the range estimate is... 

The work required to evaluate risk results will be a function of the objectives of the study. For relative risk studies, this evaluation is usually not very time-consuming. For absolute risk studies, in which many uncertainty and sensitivity cases may have been produced, the risk evaluation step may account for to 35% of the total effort of a large-scale QRA. Chapter 4 discusses the problems associated with interpreting risk results. 

Previously, the facility had several mullimillion dollar accidents, and near misses. After each accident, investigations were made and corrective actions taken. However the large fire precipitated a risk evaluation of the entire mining complex to find latent accidents. 

Thermal comfort assessments room air and operative temperatures (bur not draft risk evaluations)... 

Due to the methods and limitations outlined in Section 11.3..3, in thermal comfort analysis, draft risk evaluations cannot be performed using this type of room model. Analysis of air temperature stratification and thermal comfort for the occupant zone can be achieved only by using multi-air-node room models. 

The risk inventory or risk evaluation is die ne. t part of die hazard survey. It is not practical to expect the plan to cover every potential accident. When die hazards liave been evaluated, die plan should be focused on die most significant ones. This risk assessment stage requires die technical expertise of many people to compare die pieces of data and detennine die relevance of each. Among die important factors to be considered in performing die risk evaluation are die following ... 

The health risk evaluation process consists of four steps hazard identification, dose-response assessment or hazard assessment, exposure assessment, mid risk cliaracterization. 

Risk evaluation of accidents serves a dual purpose. It estimates tlie probability tliat an accident will occur iuid also assesses tlic severity of the consequences of an accident. Consequences may include dmnage to tlie surrounding environment, financial loss, or injury to life. This cliapter is primarily concerned witli tlie metliods used to identify hazards and tlie causes and consequences of accidents. Issues dealing witli healtli risks have been explored in die previous chapter. Risk assessment of accidents provides an effective way to help ensure eidier diat a mishap does not occur or reduces die likelihood of an accident. The result of the risk assessment allows concerned parties to take precaudons to prevent an accident before it liappens. 

Cause-consequence risk evaluation combines event tree and fault tree analysis to relate specific accident consequences to causes. Tlie process of cause-consequence evaluation usually proceeds as follows ... 

The risk evaluation process defines the equipment, hazards, and events leading to an accident. It detennines the probability tliat an accident will occur. The severity and acceptability of the risk are also evaluated. 

This cliapter serves to introduce tlie general subject of hazard risk assessment and analysis, including cause-consequence risk evaluation. The cause-consequence aspect of this topic is perliaps tlie key to understanding hazard risk. As such, it is treated in a separate section later in diis cliapter. 

Tlie reader should also note that tlie risk to people can be defined in terms of injury or fatality. The use of injuries as a basis of risk evaluation may be less disturbing tlian tlie use of fatalities. However, tliis introduces problems associated with degree of injury and comparability between different types of injuries. Further complications am arise in a risk assessment when dealing witli multiple hazards. For example, how are second-degree bums, fragment injuries, and injuries due to toxic gas e.xposure combined Even where only one type of effect (e.g., tlueshold to.xic exposure) is being evaluated, different durations of e.xposure can markedly affect tlie severity of injury. 

Guidelines for Risk Evaluation and Loss Prevention in Chemical Plants, Manufacturing Chemists Assoc., 1970. 

Compromises have to be struck between the different requirements and the restrictions implied. A deep knowledge of the actual task is essential, and for this reason it not possible to provide prescriptive prevention measures such measures have to be worked out by those involved in the actual processes of a task. The security person appointed can only act in an advisory role, although it is likely to be his responsibility to initiate the preliminary risk evaluation. 

The flashpoint experimental data overlap each other. Notice in anticipation that there is a limit of 93°C, which leads to a change in the NFPA classification code (inflammability from 1 to 2) showing how sometimes the level of error can have important consequences on risk evaluation. This example shows up another concern, which is in considering a comparison of the approach by Hilado with the author s variant, since there is a conflict between the methods on the calculation of stoichiometric concentration. 

The most difficult problem of risk evaluation linked to chemicals will be discussed in this Part. This is primarily a medical problem, which therefore comes within the competence of the company medical officer and epidemiologists, but neverthel need not only be dealt with by them. The person in charge of safety control in a place where chemicals are handled also has to tackle this problem. This person will have to take into account the level of toxicity risk of a substance. This will determine the constraint level of the measures to be taken, its favoured means of penetration, which depends on the activity, and its penetration properties specific to the organism. The physical properties of the substance (which will determine the nature of the precautions to be taken) and also the values of toxicity parameters have to be taken into account. He has to check the container labelling and know how to interpret and explain the toxicity instructions on this labelling. 

Their technical expertise is evident throughout the book, especially in the risk evaluation (Chapters 2-6) and explosion and fire phenomena and principles of blast-resistant design (Appendices A and B). 

While societal risk is generally applied to events that can impact the public, major accidents in chemical processing plants may also have the potential to affect large numbers of people. In particular, a single major event could affect multiple buildings and many individuals inside each building. Thus, the concept of societal risk can be applied to on-site risk evaluations as well as off-site evaluations. 

PHRED. 1988. Public Health Risk Evaluation Database. U.S. Environmental Protection Agency, Washington, DC. March 1988. 

Initiate pharmacotherapy for non-ST-segment elevation ACS based upon patient risk evaluate moderate and high-risk patients for early angiography and revascularization... 

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