Risk assessment questioning techniques

Unique Whole Mixtures Many techniques are available to directly quantify total toxic impacts of mixtures. The risk assessment question in this case is related to the regulatory evaluation of emissions, like in the case of effluents, or it is related to the concept of good ecological status (GES), introduced in the EU Water Framework Directive (EU Directive 2000/60/EC). 

The reality of risk assessment in investment for new processes is somewhat more complex than this. The specific innovations are often not discrete and the confidence of success of each item is a probability distribution rather than a single value. Techniques to handle the mathematical aspects have been available for many years [61] and computational tools are now readily available. A detailed coverage of managing uncertainty is beyond the scope of the current text and this simplistic approach suffices to address the key question of how to effectively manage the N-and C-values. 

Exposure assessment is done under the strong assumptions that (1) an adequate model for exposure calculation is on hand and (2) sufficient data about all influential exposure factors are available. The calculation is a prognosis about the expected level of exposure or the burden. Direct methods of exposure assessment, such as personal sampling (air, radiation), duplicate studies (nutrition) and human biomonitoring, provide information on a measurement level. The exposure assessors and the risk managers should balance the reasons for using prognostic techniques instead of direct exposure measurement methods. Both should anticipate critical questions about the validity of the exposure assessment technique in the course of public risk communication. Questions heard by the authors from concerned persons include, for example ... 

The review presented in the previous sections shows an enormous diversity in risk assessment methods and procedures for chemical mixtures. This diversity is characteristic for the current state of the art. The awareness that mixtures may cause risks that are not fully covered by single compound evaluations is growing, but the knowledge required to accurately assess the risks of chemical mixtures is still limited. The scientific community is attempting to unravel the mechanisms involved in mixture exposure and toxicity, and over recent decades, a multitude of new techniques to assess mixture risks have been developed. However, a comprehensive and solid conceptual framework to evaluate the risks of chemical mixtures is still lacking. The framework outlined in Section 5.4 can be considered a first step toward such a conceptual framework. The framework recognizes that the problem definitions vary greatly (between protective and retrospective assessments, for humans and ecosystems), and that each question has resulted in a different type of approach. 

Unease with the risk management techniques used by the railway industry were apparent in the Southall and Ladbroke Grove inquiries. The Southall Inquiry is blunt in its criticism risk assessment procedures have been shown to produce variable results, which are seldom rigorous and sometimes questionable. No primary or secondary paper-based system is a substitute for common sense and commitment to the job (Uff 2000 208). The evidence given by the Director of HSE to the Ladbroke Grove Inquiry concentrates more specifically on problems in the methods and perspectives used ... 

The basic scientific approach for utilization of quantitative toxicological risk assessment techniques can be used to help address questions of risk associated with varying exposure assumptions. 

Usually statistics on occupational accidents are presented on the aggregate level. Risk assessment of individual workers is complicated, since it requires detailed information on outcomes of all workers at risk, not only the accident casualties. Information gathering is usually initiated when occupational accidents occur the counterfactual— workers who under the same circumstances did not get involved in an accident— is not observed. For instance, Rivas et al. (2011) analyze with the help of data-mining techniques 62 questionnaires to be completed whenever an accident occurred. They conclude that data-mining outperform conventional statistics in terms of the predictive function and the possibility of identifying interactions between variables with a bearing on accidents. However, the question is whether inferences drawn from a sample of accidents only can be extrapolated to the workers who did not get involved in... 

One important question that can emerge from the assessment of safety barriers in a plant is how their performance can affect the overall risk picture. A technique capable to assess this and effectively visualize the result would provide an important decision support not only during daily operations but also on the medium term. For example, it would allow defining a maintenance plan by assessing the effect on the overall risk of temporary impairment of specific safety functions. 

Question Risk assessment process Useful tools techniques (see Annex A)... 

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 ... 

An effective HE or cost-effectiveness analysis is designed to answer certain questions, such as Is the treatment effective What will it cost and How do the gains compare with the costs By combining answers to all of these questions, the technique helps decision makers weigh the factors, compare alternative treatments, and decide which treatments are most appropriate for specific situations. Typically, one chooses the option with the least cost per unit of measure gained the results are represented by the ratio of cost to effectiveness (C E). With this type of analysis, called a cost-effectiveness analysis (CEA), various disease end points that are affected by therapy (risk markers, disease severity, death) can be assessed by corresponding indexes of therapeutic outcome (mmHg blood pressure reduction, hospitalizations averted, life years saved, respectively). It is beyond the scope of this chapter to elaborate further on principles of cost-effectiveness analyses. A number of references are available for this purpose [11-13]. 

An uncertainty assessment is an integral part of the characterization of exposure. In the majority of assessments, data will not be available for all aspects of the characterization of exposure, and those data that are available may be of questionable or unknown quality. Typically, the assessor will have to rely on a number of assumptions with varying degrees of uncertainty associated with each. These assumptions will be based on a combination of professional judgment, inferences based on analogy with similar chemicals and conditions and estimation techniques, all of which contribute to the overall uncertainty. It is important that the assessor characterize each of the various sources of uncertainty and carry them forward to the risk characterization so that they may be combined with a similar analysis conducted as part of the characterization of ecological effects. 

There are many techniques that can be used to assess risks. The ISO standard (lEC/ISO 31010, 2009) alone lists over 30 RA techniques. The question that arises is how to properly choose an appropriate RA technique that satisfies a given urban security need Criteria for that can be the applicability with given constraints concerning personnel required, e.g., expert knowledge, time-frames and resources. To this end we review the methods presented in (lEC/ISO 31010, 2009). 

However most of these methods rely on scarce accident statistics, predictive traffic flow methods (Fowler Sorgard 2000) or simulation techniques (Goerlandt Kujala 2011), which necessitate assumptions on what constitutes a vessel encounter. This may lead to an unreliable identification of risk areas, as discussed in (Goerlandt Kujala 2014). Therefore, the method presented in this paper utilizes non-collision information from actually observed traffic to assess system risk and avoid assumptions, which may question the reliability and validity of the method. 

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