Dose-response assessment characterization

Most human or environmental healtli hazards can be evaluated by dissecting tlie analysis into four parts liazard identification, dose-response assessment or hazard assessment, exposure assessment, and risk characterization. For some perceived healtli liazards, tlie risk assessment might stop with tlie first step, liazard identification, if no adverse effect is identified or if an agency elects to take regulatory action witliout furtlier analysis. Regarding liazard identification, a hazard is defined as a toxic agent or a set of conditions that luis the potential to cause adverse effects to hmnan health or tlie environment. Healtli hazard identification involves an evaluation of various forms of information in order to identify the different liaz.ards. Dose-response or toxicity assessment is required in an overall assessment responses/cffects can vary widely since all chemicals and contaminants vary in their capacity to cause adverse effects. This step frequently requires that assumptions be made to relate... 

Dose-response assessment is the process of characterizing the relationship between the dose of an agent administered or received and the incidence of an adverse health effect in e.xposed populations, and estimating the incidence of the effect as a function of e.xposure to the agent. This process considers such important factors as intensity of exposure, age pattern of exposure, and possibly other variables that might affect response, such as sex, lifestyle, and other modifying factors. 

Dose-response assessment is the process of obtaining quantitative information about the probability of human illness following exposure to a hazard it is the translation of exposure into harm. Dose-response curves have been determined for some hazards. The curves show the relationship of dose exposure and the probabihty of a response. Since vahdated dose-response relationships are scarce, various other inputs are used to underpin the hazard characterization phase of risk assessment. 

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... 

Hazard characterization (or dose-response assessment) is the qualitative and, as far as possible, quantitative description of the inherent properties of an agent or situation having the potential to cause adverse effects. This step should include a dose-response assessment that describes the severity of adverse effects (the responses) related to the amount and condition of exposure to an agent (the dose). 

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. 

Within the framework depicted in Figure 7.1, the content of risk assessment proposed by the committee is shown as comprising four analytic steps hazard identification, dose-response assessment, human exposure assessment, and a final, integrating step called risk characterization. These four terms and the activities they describe have come to be widely accepted within the risk assessment community, on... 

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. 

Hazard characterization, also known as dose-response assessment, is the second stage in hazard assessment, and the second step in the process of risk assessment. At this step, the No-Observed-Adverse-Effect Level (NOAEL) and the Lowest-Observed-Adverse-Effect Level (LOAEL) are derived for the observed effects, where possible and appropriate. 

Because an agent may induce multiple mmor types, the dose-response assessment includes an analysis of aU tumor types, followed by an overall evaluation that includes a characterization of the risk estimates across tumor types, the strength of the mode of action information of each mmor type, and the anticipated relevance of each mmor type to humans, including susceptible populations and fife stages (e.g., childhood). 

The second step of the dose-response assessment is an extrapolation to lower dose levels, i.e., below the observable range. The purpose of low-dose extrapolation is to provide as much information as possible about risk in the range of doses below the observed data. The most versatile forms of low-dose extrapolation are dose-response models that characterize risk as a probability over a range of environmental exposure levels. Otherwise, default approaches for extrapolation below the observed data range should take into account considerations about the agent s mode of action at each tumor site. Mode-of-action information can suggest the likely shape of the dose-response curve at these lower doses. Both linear and nonlinear approaches are available. 

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. 

Risk characterization is the qualitative and/or quantitative estimation, including attendant uncertainties, of the severity and probability of known and potential adverse effects of a substance in a given population it is based on hazard identification, dose-response assessment and exposure assessment (OECD/IPCS, 2001), as described above. 

Faustman EM, Allen BC, Kavlock RJ. Kimmel CA (1994) Dose-response assessment for developmental toxicity I. Characterization of data base and determination of NOAELs. Fundam Appl Toxicol, 23 478-486. 

According to the National Research Council of the National Academy of Science, risk assessment consists of four broad but interrelated components hazard identification, dose-response assessment, exposure assessment, and risk characterization, as depicted in Figure 24.1. The reader should, however, be aware that these risk assessment activities can provide research needs that improve the accuracy of estimating the risk or probability of an adverse outcome. 

Risk assessment The evaluation of scientific information on the hazardous properties of environmental agents (hazard characterization), the dose-response relationship (dose-response assessment), and the extent of human exposure to those agents (exposure assessment). 

Risk assessment is frequently described as involving four components - hazard identification, exposure assessment, dose-response assessment, and risk characterization. Risk assessment may be an input to risk management. 

This chapter will address the implications of the data presented in previous chapters for assessing the risks from environmental chemical exposures. WHO/IPCS has defined risk assessment as an empirically based paradigm that estimates the risk of adverse effects from exposure of an individual or population to a chemical, physical, or biological agent. As shown in Figure 21, it includes the components of hazard identification (Is there an adverse effect ), dose-response assessment (How severe is it ), exposure assessment (What is the level of exposure ), and risk characterization (What is the risk ) (NRC, 1983 IPCS, 2000). 

The examples noted above serve to highlight where advances in the understanding of basic cellular housekeeping processes and the consequences of their perturbation can have a very significant impact on determining the mechanism of adverse health outcomes and the subsequent assessment of risk. Thus, studies of mutagenicity play an important role in hazard identification, dose-response assessment, and the characterization of risk. 

ASSESSMENT OF RISKS TO HUMANS EXPOSED TO PESTICIDES 2 The Four Steps in Risk Assessment 2 Hazard Identification 2 Dose-Response Assessment 3 Margin of Safety Approach 3 Quantitative Risk Assessment 3 Exposure Assessment 4 Risk Characterization 4 RISK MANAGEMENT 5 ADVANCES IN DATA INTERPRETATION 5 Probabilistic Approaches 5 Recognition of the Tier Approach 5 Aggregate Exposure 6 Cumulative Exposure 6 Impact of New Scientific Advances 7 Post-Registration Monitoring 7 HARMONIZATION OF REGULATORY APPROACHES SUMMARY 9... 

Health risk assessment is defined as tlie process or procedure used to estimate tlie likelihood that humans or ecological systems will be adversely affected by a chemical or physical agent under a specific set of conditions. Tlie health risk evaluation process consists of four steps hazard identification, dose-response assessment or liazard assessment, exposure assessment, and risk characterization. 

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