Risk characterization process

The analysis of chemical risk is a process comprising the following elements hazard identification, exposure assessment, dose-response assessment, and risk characterization [6]. Figure 1 shows the main elements that constitute the risk characterization process together the methodologies used for their determination. The essence of risk characterization is to relate the exposure (the concentration of a... 

The process of risk characterization has been described and discussed extensively in the scientific literature. It is beyond the scope of this book to review aU these references. This chapter is limited to give a very short overview of some general aspects related to the risk characterization process, as well as of the currently used approaches in the WHO, the US-EPA, and the EU, and is thus not meant to be exhaustive. 

If possible, as a last step in the risk characterization process, an uncertainty analysis should be carried out, which, if it results in a quantifiable overall uncertainty, produces an estimation of the risk. 

The US-EPA s Risk Characterization Handbook (US-EPA 2000) was developed to implement the Risk Characterization Policy. This Handbook provides a single, centralized body of risk characterization implementation guidance for the US-EPA s risk assessors and risk managers to help make the risk characterization process Transparent and the risk characterization products. Clear, Consistent, and Reasonable (TCCR). TCCR became the underlying principle for a good risk characterization. The Handbook has two parts. 

The determination of MOE is a part of the risk characterization process of a compound. MOE is a way to express the risk of noncarcinogenic effects of... 

Because the dose-response assessment step is performed differently for agents considered to be carcinogens compared to those classified as noncarcinogens, the risk characterization process for these two kinds of agents differs as well. The result of the dose-response assessment for carcinogens is some measure of the potency of the agent for example, the... 

As mentioned before, the ecological risk assessment is characterized by a problem formulation process, analysis containing characterizations of exposure and effects, and a risk characterization process. Several outlying boxes serve to emphasize the importance of discussions during the problem formulation process between the risk assessor and the risk manager, and the critical nature of the acquisition of new data, verification of the risk assessment, and monitoring. The next few sections detail each aspect of this framework. 

This summary serves as the starting materials for the overall risk characterization process that completes the risk assessment. This chapter will concentrate on a specific feature of this risk characterization process, namely the importance of developing approaches for incorporating mechanistic data into the hazard, dose-response, and exposure assessments to reduce uncertainties in the process and thereby reduce the reliance on default factors that are used in the absence of reliable data. Given that the risk characterization is for the estimation of risks to humans from low, enviromnental exposures, then the issues that cover the necessary defaults are as follows (see Rart I, this volume) ... 

Dose-Response Evaluation The process of quantitatively evaluating toxicity information and characterizing the relationship between the dose a contaminant administered or received, and the incidence of adverse health effects in the exposed population. From a quantitative dose-respoiise relationship, toxicity values can be derived that are used in the risk characterization step to estimate the likelihood of adverse effects occurring in humans at different exposure levels. 

Risk characterization is lire process of estimating llie incidence of a health effect under the various conditions of human or animal exposure described in lire exposure assessment. It is performed by combining the exposure (see Cliapter 12) and dose response (see Cluipter 11) assessments. The summary effects of the uncertainties in lire preceding steps should also be described in lliis step. 

Risk characterization is tlie process of estimating tlie incidence of a healtli effect under tlie various conditions of human or animal exposure as described in the exposure assessment. It evolves from both dose exposure assessment and toxicity response assessment. The data are then combined to obtain qualitative and quantitative expression of risk. 

Risk characterization estimates tlie healtli risk associated with tlie process under investigation. The result of tliis cliaracterization is a number tliat represents tlie probability of adverse healtli effects from tliat process or from a substance released in tliat process. For instance, a risk cliaracterization for all effects from an incineration process might be expressed as one additional cancer case per 1 million people. 

Critical load exceedances may serve as the basis for interpreting ecological impacts as ecological risks (or rather changes in the level of current risk to ecosystem health ). This would refer to the process of ecological risk characterization. 

Risk Assessment The scientific process of evaluating the toxic properties of a chemical and the conditions of human exposure to it, in order to ascertain the likelihood that exposed humans will be adversely affected, and to characterize the nature of the effects they may experience. It may contain some or all of the following four steps hazard identification, dose-response assessment, exposure assessment, and risk characterization. 

The following are the major subjects of the book the various institutions, agencies, and programs involved in chemicals regulation (Chapter 2). The data for hazard assessment (Chapter 3) and the hazard assessment process, i.e., identihcation and characterization of the various toxicological effects and the associated test methods (Chapter 4). Standard setting for threshold effects (Chapter 5) and non-threshold effects (Chapter 6). Exposure assessment (Chapter 7) and risk characterization (Chapter 8). Regulatory standards set by various bodies (Chapter 9) and combined actions of chemicals in mixture (Chapter 10). 

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. 

Hazard identification is the process of collecting and evaluating information on the effects of an agent on animal or human health and well-being. In most cases, this involves a careful assessment of the adverse effects and what is the most sensitive population. The dose-response assessment involves evaluation of the relationship between dose and adverse effect. Typically, an effort is made to determine the lowest dose or exposure at which an effect is observed. A comparison is often made between animal data and any human data that might be available. Next is exposure assessment, in which an evaluation of the likely exposure to any given population is assessed. Important parameters include the dose, duration, frequency, and route of exposure. The final step is risk characterization, in which all the above information is synthesized and a judgment made on what is an acceptable level of human exposure. In the simplest terms, risk is the product of two factors hazard and exposure (i.e. hazard x exposure = risk). In real risk assessments, all hazards may not be known and exposure is often difficult to quantify precisely. As a result, the calculated risk may not accurately reflect the real risk. The accuracy of a risk assessment is no better than the data and assumptions upon which it is based. 

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. 

Human health hazards assessment is the process of identifying the potential effects that chemical may have on humans who are exposed to it, and of determining the levels at which these effects may occur. Human health toxicity data are compared with data from the exposure assessment module to assess human health risk in the risk characterization module. 

Risk characterization (also referred to in the CTSA process as risk integration) is the integration of hazard and exposure information to quantitatively or qualitatively assess risk. 

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