Costs quantitative risk assessment

A facility risk review (FRR) is intermediate between a qualitative HAZOP and a quantitative risk assessment (QRA) achieved by broad probability and consequence classifications. Although not a risk assessment, an FRR uses PSA to get optimum risk cost-benefit. 

Evaluating risk to process plant building occupants can be accomplished through detailed qualitative and/or quantitative risk assessment. However, because of the large numbers of buildings and varying plant situations involved, these types of studies could be costly and time-consuming if applied in all cases, and should be reserved for those situations for which cost-effective solutions cannot otherwise be identified. 

This paper will summarize briefly some work my colleagues and I at Decision Focus Incorporated have carried out for EPA to show how decision analysis might be used to assist decision making under TSCA ( 5). I will first briefly review the concepts of quantitative risk assessment and cost-benefit analysis to show how decision analysis fits with these concepts and provides a natural way of extending them. Then I will illustrate the approach using a case study on a specific chemical, perchloroethylene. 

For non-thresholded contaminants some mechanism is required that will allow the benefits in terms of reduced risks and costs associated with control to be taken into account. The costs of control will include enforcement costs as well as costs to producers in reaching ever stricter standards. Ultimately these costs will be borne by consumers in taxes, increased prices or reduced choice. Economic theory dictates that there must be a point where the extra increase in the cost of control is not justified by the corresponding increase in benefit (reduction in risk). This optimal point will differ for each contaminant according to the technology needed to control it, the nature of the hazard, and the relationship between dose and risk. It is in this latter context that quantitative risk assessment (QRA) becomes critical (see section 2.3.4 of this chapter). 

A primary directive of CERCLA is the protection of public health. Because the hazards that exist at Superfund sites tend to be quite variable, it has not been possible to establish specific cleanup criteria for the hazardous substances regulated under CERCLA potential human health effects must be evaluated by quantitative risk assessment on a site-by-site basis. Each Superfund site is assessed individually to determine how clean is clean. The rationale is that the hazard of a contaminant is a function of its potential to reach a receptor (e.g., groundwater, population) and the potential harm to the exposed receptor. The ability of a contaminant to migrate, its potential to degrade, and its distance to a receptor of concern (i.e., the risk), all are site-specific. Only on the basis of such individualized risk assessment is it possible to achieve efficient and cost-effective cleanup of the thousands of hazardous waste sites throughout the US. 

The traditional scientific and political response to these data gaps has been to collect more information and use a technique called quantitative risk assessment to calculate the probability of harm given particular exposures, applying numerous assumptions in the process. While this process has been termed the sound science approach, it is often far from that. Quantitative risk assessments often narrow the types of information that go into decision-making and hide uncertainties. They are time-consuming and costly to complete and while debates over details of these assessments occur, the default policy option is that no policy action is necessary. 

Of course, quantitative risk assessment is still necessary, even when ecological models are used, but in addition to specific, absolute quantifications, a main area of ecological models could be relative risk assessments Which application scheme is more efficient in terms of interest, for example, control efficiency, effects on nontarget organisms, and costs ... 

Quantitative Risk Assessment. Previous sections in this chapter dealt with the identification, measurement, and mitigation of hazards in a chlor-alkali plant. Plant safety and Responsible Care programs define the objectives of continuous improvement in safety performance. The discussion of mitigation immediately above naturally leads on to the larger question of the most direct and cost-effective approach to this improvement. 

Experience has shown that the third option is viable, provided that inhibitor performance has been assessed predictably. Experience has also shown dramatic failures where these conditions had not been met. Selection of a corrosion inhibitor, therefore, boils down to quantitative risk assessment and cost performance, which can only be achieved on the basis of reliable/beUevable performance data. 

I was working with an operator of one of the oldest subways in the world. They wanted to bring the design up to meet more modem fire codes. But because the system was so old and so large, it would cost billions and billions of dollars. We did a probabilistic risk assessment using fault trees to identify and quantify how fires can start in the system. We then used a quantitative risk assessment as part... 

Approval of a system is usually based on safety first principle, i.e., a quantitative risk assessment (QRA) and also the cost effectiveness (cost-benefit analysis)... 

Where a major decision regarding cost or safety implication has to be made, it has become increasingly difficult to defend the traditional qualitative process called engineering judgement . Thus, there has been a steady trend towards quantifying risks and/or costs, in particular the techniques of HAZard IDentification (HAZID), Quantitative Risk Assessment (QRA) and Cost-Benefit Analysis (CBA), have come very much to the fore. 

Process Hazards Analysis. Analysis of processes for unrecogni2ed or inadequately controUed ha2ards (see Hazard analysis and risk assessment) is required by OSHA (36). The principal methods of analysis, in an approximate ascending order of intensity, are what-if checklist failure modes and effects ha2ard and operabiHty (HAZOP) and fault-tree analysis. Other complementary methods include human error prediction and cost/benefit analysis. The HAZOP method is the most popular as of 1995 because it can be used to identify ha2ards, pinpoint their causes and consequences, and disclose the need for protective systems. Fault-tree analysis is the method to be used if a quantitative evaluation of operational safety is needed to justify the implementation of process improvements. 

The Chemical Process Industry (CPI) uses various quantitative and qualitative techniques to assess the reliability and risk of process equipment, process systems, and chemical manufacturing operations. These techniques identify the interactions of equipment, systems, and persons that have potentially undesirable consequences. In the case of reliability analyses, the undesirable consequences (e.g., plant shutdown, excessive downtime, or production of off-specification product) are those incidents which reduce system profitability through loss of production and increased maintenance costs. In the case of risk analyses, the primary concerns are human injuries, environmental impacts, and system damage caused by occurrence of fires, explosions, toxic material releases, and related hazards. Quantification of risk in terms of the severity of the consequences and the likelihood of occurrence provides the manager of the system with an important decisionmaking tool. By using the results of a quantitative risk analysis, we are better able to answer such questions as, Which of several candidate systems poses the least risk Are risk reduction modifications necessary and What modifications would be most effective in reducing risk ... 

As probabilistic exposure and risk assessment methods are developed and become more frequently used for environmental fate and effects assessment, OPP increasingly needs distributions of environmental fate values rather than single point estimates, and quantitation of error and uncertainty in measurements. Probabilistic models currently being developed by the OPP require distributions of environmental fate and effects parameters either by measurement, extrapolation or a combination of the two. The models predictions will allow regulators to base decisions on the likelihood and magnitude of exposure and effects for a range of conditions which vary both spatially and temporally, rather than in a specific environment under static conditions. This increased need for basic data on environmental fate may increase data collection and drive development of less costly and more precise analytical methods. 

Due to lack of established, user-friendly, and cost effective quantitative approaches to ecosystem risk assessment inEcoR A, in the current El A practice of project appraisal ecosystem risk assessment (if conducted) is usually comparative or qualitative (see, e.g., Lohani et al. (1997) for in-depth discussion). 

Qualitative findings of ecosystem risk assessments are of low utility for risk management. They cannot be compared with quantitative estimates of other risks this compromises the ability of risk ranking to provide insights to setting priorities. It is particularly difficult to convert them into a format applicable for cost-benefit analysis, which is a key tool that any proponent uses in decision-making on a proposed project. 

In the case of biological contamination, the identification of risk became obvious by experience, the risk assessment was made unambiguous by epidemiology, and the immediate and obvious effectiveness of the risk management decisions demonstrated their wisdom in the absence of elegant quantitative risk extrapolation models and projections of costs per case averted. Costs of water treatment and distribution became trivial relative to almost all other essential commodities, and in the public expectation the biological safety of drinking water became axiomatic. 

In addition to in vivo and in vitro experimentation, mathematical models and quantitative structure-permeability relationship (QSAR) methods have been used to predict skin absorption in humans. These models use the physico-chemical properties of the test compound (e.g. volatility, ionization, molecular weight, water/lipid partition, etc.) to predict skin absorption in humans (Moss et al 2002). The models are particularly attractive because of the low cost and rapidity. However, because of the above-mentioned factors influencing dermal absorption, mathematical models are of limited use for risk assessment purposes. Since these models are currently not accepted by regulatory agencies involved in pesticide evaluations, they will not be further discussed in this chapter. 

This chapter focuses on qualitative and semi-quantitative techniques that can be used to analyze the safe transport of hazardous materials. These simple and efficient risk assessment approaches represent the level of complexity needed to sufficiently understand and make decisions for the majority of hazardous material issues. A fully quantitative approach (Chapter 5) may be needed if the level of detail developed with qualitative or semi-quantitative approaches is inadequate to confidently make final risk management decisions. The choice of a more quantitative approach also may be needed if the cost of the identified risk mitigation options is high, warranting a more detailed understanding of the... 

General Recommendation 3. If a decision is made to move forward with any of these technology packages, health and safety evaluations should progress from qualitative assessments to more quantitative assessments as the process design matures. Quantitative (QRA), health (HRA), and ecological risk assessments should be conducted as soon as is practical. Early initiation of these assessments will allow findings to be implemented with minimal cost and schedule impact. 

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