Risk assessment process characterization

FIGURE 1.2 The risk assessment process from data collection to risk characterization. 

The Risk Assessment process includes four steps hazard identification, hazard characterization (related term dose-response assessment), exposure assessment, and risk characterization. It is the first component in a risk analysis process. 

Risk Characterization is the fourth step in the Risk Assessment process. 

For both human health and the environment, the risk assessment process includes (i) an exposure assessment, (ii) an effect assessment (hazard assessment and hazard characterization -addressed in detail in Chapter 4), and (iii) a risk characterization (addressed in detail in Chapter 8). As a part of the effect assessment, classification and labeling of the substance according to the criteria laid down in Directive 67/548/EEC (EEC 1967) is also addressed (Section 2.4.1.8). 

Risk characterization is thus the step in the risk assessment process where the outcome of the exposure assessment (e.g., daily intake via food and drinking water, or via inhalation of airborne substances) and the hazard (effects) assessment (e.g., NOAEL and tolerable intake) are compared. If possible, an uncertainty analysis should be carried out, which produces an estimation of the risk. Several questions should be answered before comparison of hazard and exposure is made ... 

In 1995, the US-EPA updated and issued the current Agency-wide Risk Characterization Policy (US-EPA 1995). The Policy called for all risk assessments performed at US-EPA to include a risk characterization to ensure that the risk assessment process is transparent. It also emphasized that risk assessments should be clear, reasonable, and consistent with other risk assessments of similar scope prepared by programs across the Agency. 

The Handbook emphasized that other aspects than science influence risk characterization, and that science policy choices must be made to deal with uncertainties. Many choices are usually made during the course of the risk assessment process, resulting in a particular outcome. Therefore, it is possible to perform parallel risk assessments of the same data, but reach different results. 

Other terms used to describe this phase of the risk assessment process include problem dehnition, problem characterization, risk profiling (EC 2000), and scoping phase. ... 

Risk assessment is quantitative and differs from risk management, which involves weighing options to reduce the risk. The risk assessment process begins with identifying the potential hazards and their occurrence in a specihc environment (i.e., exposure assessment), their toxicity (i.e., dose-response), and a characterization of the risk (NRC, 1994). Risk assessment determines the probability of realizing harm as a result of exposure to a given hazard. 

The hardest part of engineering risk assessment has turned out to be the prediction of the modes of failure. Serious accidents at nuclear installations, such as those at Three Mile Island or at Chernobyl, have been caused by modes of failure that had not been analysed at all. For example, the report of the Presidents Commission on the Accident at Three Mile Island (Presidents Commission, 1979, p9) highlighted that the concentration of the assessment process on more obvious large break scenarios meant that the eventual mode of failure, which was a result of a chain of a number of more minor events, was not even considered. Despite the use of significant resources in the design process, the risk assessment had been unable to characterize the complex system adequately, a system that was totally human-made and defined. In particular, the risk assessment process had not been able to identify modes of failure caused by humans involved in the operations of the reactor behaving in unexpected ways. 

Because chemicals regulation is risk-based there must be evidence that an identified type of harm is likely to result from use of a particular chemical (in other words that the chemical poses a significant risk) before action can be taken to restrict its production or use. However, if we consider how risk assessment of chemicals is carried out, it is apparent that current methods are not able to provide evidence that commands agreement on whether there is a risk from a chemical or not. Partly as a consequence of this, risk assessment processes have been characterized by procrastination and delay. During this delay the production and use of potentially harmful chemicals is allowed to continue. 

The overall ecological risk assessment process is shown in Figure 28.1 and includes three primary phases (1) problem formulation, (2) analysis, and (3) risk characterization. Problem formulation includes the development of a conceptual model... 

Suter et al. 1993 Society of Environmental Toxicology and Chemistry [SETAC] 1994 European Union 1997 Ecological Committee on FIFRA Risk Assessment Methods [ECOFRAM] 1999 Campbell et al. 1999). The initial use of conservative assessment criteria (i.e., err on the side of caution) allows substances that do not present a risk to be eliminated from the risk assessment process early, thus allowing the focus of resources and expertise to be shifted to potentially more problematic substances or situations. As one ascends through the tiers, the estimates of exposure and effects become more realistic with the acquisition of more accurate and/or representative data, and uncertainty in the extrapolation of effects is thus reduced or at least better characterized. Likewise, the methods of extrapolation may become more sophisticated as one ascends through the tiers (Figure 1.2). 

Risk characterization A phase of the risk assessment process that integrates the exposure and stressor response profiles to evaluate the likelihood of adverse effects associated with exposure to the contaminants. 

The European Commission risk assessment reports for the diphenylethers Penta (European Commission 2001), Octa (European Commission 2003b), and Deca (European Commission 2002 and 2004) were used to identify examples of scientific uncertainties in the risk assessment process for potential PBT/vPvB substances. A systematic search for indicators of scientific uncertainty in these documents was performed, including how these uncertainties are described and handled in the risk characterization and in the conclusions section, and taking into consideration the use of and weight given to non-standard data in the final conclusions. 

Because most risk assessments include major uncertainties, it is important that biological and statistical uncertainties be described in the risk characterization. The assessment should identify the components of the risk assessment process that involve the greatest degree of uncertainty. 

Each hazard classification and communication system (workplace, consumer, transport) begins coverage with an assessment of the hazards posed by the chemical or chemical product involved. The degree of its capacity to harm depends on its intrinsic properties, i.e. its capacity to interfere with normal biological processes, and its capacity to bum, explode, corrode, etc. This is based primarily on a review of the scientific studies available. The concept of risk or the likelihood of harm occurring, and subsequently communication of that information, is introduced when exposure is considered in conjunction with the data regarding potential hazards. The basic approach to risk assessment is characterized by the simple formula ... 

In 1983, the National Research Council of the (US) National Academy of Sciences published a report titled Risk Assessment in the Federal Government Managing the Process this work has had a marked influence on the risk assessment process used by regulatory agencies worldwide. The risk assessment process, in this report, consists of four components hazard identification, dose-response assessment, exposure assessment, and risk characterization. 

Being able to predict the human health risk from exposure to airborne chemicals can be complex, requiring reliable analysis of human exposure. While the basic principles of risk assessment are applicable to various conditions of exposure, characterizing how an individual s health status can significantly influence the threshold for effects can be a most challenging component of the risk assessment process. One needs to consider the overall scientific weight-of-evidence to predict whether or not an individual may be uniquely susceptible to certain... 

Uncertainties inherent to the risk assessment process can be quantitatively described using, for example, statistical distributions, fuzzy numbers, or intervals. Corresponding methods are available for propagating these kinds of uncertainties through the process of risk estimation, including Monte Carlo simulation, fuzzy arithmetic, and interval analysis. Computationally intensive methods (e.g., the bootstrap) that work directly from the data to characterize and propagate uncertainties can also be applied in ERA. Implementation of these methods for incorporating uncertainty can lead to risk estimates that are consistent with a probabilistic definition of risk. 

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