Risk assessment steps

In terms of the contents of Part 111, Cliapter 9 serves to introduce die general subject of healdi risk assessment (HRA). An expanded presentation on each of die four healdi risk assessment steps follows, as detailed below ... 

The risk assessment steps and the risk characterization are influenced by uncertainty and variability. Variability arise from heterogeneity such as dose-response differences within a population, or differences in contaminant levels in tlie environment. Uncertainty on tlie other lumd, represents lack of knowledge about factors such as adverse effects or contaminant levels. 

In this chapter human health and environmental risk assessment steps were introduced. Five models (EUSES, USEtox, GLOBOX, SADA, and MAFRAM) risk and LCIA models were briefly described and also other 12 models were appointed. There is no risk assessment model better than another. All models have their strengths and weaknesses and many of them also are focused on one... 

When the scope is known and the extrapolation methods are defined, the data for the risk assessment steps (and extrapolations) can be collected. For tiered systems, this implies that choices need to be made on the manner in which uncertainties are addressed and what to do when these are only addressed by simple methods. A distinction was already made between prospective use and retrospective use of extrapolation methods. In both cases, extrapolations are being applied, but the way in which existing methods are selected for an assessment problem can differ. 

Risk assessment iinoKes the integration of the information and analysis associated with the above four steps to provide a complete characterization of the nature and magnitude of risk and the degree of confidence associated with tliis characterization. A critical component of the assessment is a full elucidation of the uncertainties associated witli each of die major steps. Under this broad concept of risk assessment are encompassed all of the essential problems of toxicology. Risk assessment takes into account all of the available dose-response data. It should treat uncertainty not by the application of arbitrary safety factors, but by stating them in quantitatively and qualitatively explicit tenns, so tluit they tire not hidden from decision makers. Risk assessment defined in tliis broad way, forces an assessor to confront all the scientific uncertainties and to set fortli in e.xplicit terms tlie means used in specific cases to deal with these uncertainties. An e. panded presentation on each of the four hcaltli risk assessment steps is provided telow. 

An overview of the steps in a TOPAZ safety risk assessment cycle is given in Figure 3. Although the cycle itself is very much in line with the established risk assessment steps (e.g. Kumamoto and Henley, 1996), some of these steps differ significantly. 

The following subsections present the risk assessment steps of a TOPAZ cycle in more detail. Then it also becomes clear that Monte Carlo simulation plays a key role in step 5 assess frequency. 

Prior to the development of a quantitative accident risk model for the active runway crossing operation considered, all risk assessment steps had been performed using an expert-based approach. In this study the following safety relevant scenarios were found ... 

For facilities that are still in the design stage, the actions taken, particularly during the Risk Assessment step, will change for each iteration. For example, early evaluations of risk will use a HAZID (Hazard Identification) technique later on, as detailed engineering information becomes available, the more comprehensive HAZOP (Hazard and Operability Study) method will be used. 

Figure 24.2 Coarse and detailed risk assessments (Steps 2 and 3).

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