Risk characterization defined

Risk characterization is defined as the integration of the data and analysis of the above three components to determine the likelihood that humans wiU. experience any of the various forms of toxicity associated with a substance. When the exposure data are not available, hypothetical risk is characterized by the integration of hazard identification and dose—response evaluation data. 

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... 

As mentioned before, environmental exposure is the first key aspect to develop risk characterization from a defined scenario (see Fig. 1). Experimental analysis is the most obvious and classical procedure for determining the chemical occurrence in the environment. Measuring environmental concentrations (MECs) is more accurate and reflects the reality better than any other method, but the main drawback is the large amount of resources required for these laboratory measurements. Field environmental monitoring programs have become increasingly expensive as... 

Finally, in the risk characterization step, the PEC/PNEC quotient that defines the risk of the substance in the environment is calculated. If the quotient (PEC/PNEC) is less than 1, the substance do not present risk to the environment. More information is available in the European Commission Technical Guidance Document on Risk Assessment [3] and in the United States Environmental Protection Agency s Guidelines for Ecological Risk Assessment [6]. 

USEtox . In order to determine the environmental risk characterization for DeBDEs and Pb in China, USEtox requires that different scales are defined. Since China is such a big country, the whole country has been considered as a continent. Therefore, the continental landscape data are defined by parameters describing this target country. Moreover, due to the nature of the model, two... 

Quantitative nature of the CLL approach. Numerical tolerable exposure levels for pollutants of concern are defined to establish quantitative thresholds for risk characterization therefore the CLL approach provides a basis for quantitative ecosystem risk and damage assessment. 

Qualification of a capillary electrophoresis instrument is performed using failure mode, effects, and criticality analysis as the risk analysis tool. The instrument is broken down into its component modules and the potential failures of those components identified. The potential effect of those failures is defined and the risk characterized. Any current evaluation of those failures is identified and any recommended actions to mitigate the risk defined. 

The POD is used as the starting point for subsequent extrapolations and analyses. For linear extrapolation, the POD is used to calculate a slope factor, and for nonlinear extrapolation the POD is used in the calculation of a Reference Dose (RfD) or Reference Concentration (RfC). In a risk characterization, the POD is part of the determination of an MOE, defined as the ratio of the POD over an exposure estimate (MOE = POD/Exposure). 

Exposure should normally be understood as external exposure, which can be defined as the amount of substance ingested, the total amount in contact with the skin (which can be calculated from exposure estimates expressed as mg/cm or mg/cm ), or either the amount inhaled or the concentration of the substance in the atmosphere, as appropriate. In cases where a comparison needs to be made with systemic effects data (e.g., when inhalation or dermal toxicity values are lacking or when exposures due to more than one exposure route need to be combined) the total body burden has to be estimated. Since the assessment of the amount that is absorbed after ingestion, by inhalation or by the skin is usually done in the effects assessment (section on toxicokinetics), this calculation of the total body burden is often placed in the section on risk characterization. 

Risk characterization is The qualitative and, wherever possible, quantitative determination, including attendant uncertainties, of the probability of occurrence of known and potential adverse effects of an agent in a given organism, system or (sub)population, under defined exposure conditions. ... 

The major elements to be considered in the risk characterization part include key information, context, sensitive subpopulations, scientific assumptions, policy choices, variability, uncertainty, bias and perspective, strengths and weaknesses, key conclusions, alternatives considered, and research needs. Whether every element is actually written into the risk characterization or not, depends upon the purpose of the risk assessment and the detail necessary to adequately characterize it. By the time the risk assessment is completed, the universe of policy choices, management decisions, and uncertainties should have been identified, as well as the conclusions of the risk assessment. Because key findings differ for each risk assessment, it is not possible to define exactly what they are genericaUy. Professional judgment is necessary to define them. 

SRA provides an open forum for all those who are interested in risk analysis. Risk analysis is broadly defined to include risk assessment, risk characterization, risk communication, risk management, and policy relating to risk. ... 

Finally, if the registrant can prove that all risks are under control and the substance can be safely manufactured and used, the corresponding initial exposure scenario is defined as the final exposure scenario. In the end, the final exposure scenario is communicated within the framework of extended safety data sheets in order to ensure the safe use of the substance down the supply chain (Caveat The legal text of REACH usually refers to the term exposure scenario while in reality speaking of the final exposure scenario.) By contrast, if the registrant fails to lower the risk characterization ratio below 1, despite the aforementioned refinements and modifications, he must prevent the use of the substance under circumstances where the risks are not controlled. 

Since risk analysis plays an important role in public policy decision making, efforts have been made to devise a means by which to identify, control, and communicate the risks imposed by agricultural biotechnology. A paradigm of environmental risk assessment was first introduced in the United States by Peterson and Arntzen in 2004. In this risk assessment, a number of assumptions and uncertainties were considered and presented. These include (1) problem formulation, (2) hazard identihcation, (3) dose-response relationships, (4) exposure assessment, and (5) risk characterization. Risk assessment of plant-made pharmaceuticals must be reviewed on a case-by-case basis because the plants used to produce proteins each have different risks associated with them. Many plant-derived biopharmaceuticals will challenge our ability to define an environmental hazard (Howard and Donnelly, 2004). For example, the expression of a bovine-specihc antigen produced in a potato plant and used orally in veterinary medicine would have a dramatically different set of criteria for assessment of risk than, as another example, the expression of a neutralizing nonspecihc oral antibody developed in maize to suppress Campylobacter jejuni in chickens (Peterson and Arntzen, 2004 Kirk et al., 2005). 

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). 

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. 

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. 

Hydrophobicity (or lipophilicity) characterizes the readiness of a molecule to escape or to prefer the water environment. It plays a fundamental role in biochemical processes and influences the fate of a molecule in the environment. Thus, hydrophobic descriptors play an important role in QSAR modeling that is used in drug research and for risk characterization. The most widely used hydrophobic descriptor is the octanol-water partition coefficient (log P) proposed by Hansh [49]. P is a quotient between solubihties in octanol and water. It is defined by following equation ... 

A risk assessment is defined as a qualitative and quantitative process conducted by EPA to characterize the nature and magnitude of risks to public health from exposure to hazardous substances, pollutants, or contaminants released from specific sites. Risk assessments include the following components hazard identification, dose-response assessment, exposure assessment, and risk characterization. Statistical and biological models are used in quantitative risk... 

Risk characterization provides for both qualitative and quantitative descriptions of risk. The step involves integrating the results of the hazard identification, dose-response assessment, and exposure assessment to characterize risk. Often, a direct comparison between exposure criteria developed in the first two steps and the results of the exposure assessment (concentration in the environmental media or the estimated dose, as appropriate) provide a basis for determining whether risks are acceptable. Typically, if criteria are exceeded, the risk is not acceptable. What is defined as acceptable, as well as the way risk is expressed, is often a... 

US EPA s approach, as defined in RAGS, incorporates the principles defined in 1983 by NAS. The US EPA RAGS identifies four steps in an environmental risk assessment data collection and evaluation, exposure assessment, toxicity assessment, and risk characterization. Tasks involved in characterizing the environmental media have greater emphasis because they often require tremendous resources and time. 

Risk characterization includes a comparison between toxicity values and/or exposure criteria and exposure (dose or media concentration) to determine whether the exposure is acceptable. US EPA developed a formalized system that is commonly used to determine whether chemicals are likely to present an unacceptable risk based on current and likely future use of the property. The estimated dose is used to calculate an additional lifetime cancer risk for each chemical regulated as a carcinogen. Typically, a total site risk (sum of the risk associated with all carcinogens identified at the site) is presented. Acceptable risk is defined by the agency, in the appropriate laws, or by regulations that govern the site. Acceptable risk is a function of policy or law but is supposed to be rooted in science. 

A second use for NOAELs (or LOAELs) is in the calculation of a proposed margin of exposure (MOE) for developmental toxicity to be used in risk characterization. The MOE is defined as the ratio of the NOAEL from the most sensitive or appropriate species to the estimated human exposure level from all potential sources. If the MOE is very high relative to the estimated human exposure level, then risk to the human population would be considered low. 

Define problem formulation, hazard assessment, exposure assessment, and risk characterization as in Figure 12.1. 

The next three sections of this report are arranged to follow the framework sequentially Section 2 describes problem formulation this section is particularly important for assessors to consider when specific assessment endpoints are not determined a priori by statute or other authority. Section 3 and Section 4 discuss analysis and risk characterization, respectively. Section 5 defines the terms used in this report, and Section 6 provides literature references. The lists of ecological risk assessment issues at the end of Section 1 to Section 4 highlight areas for further discussion and research. EPA believes that these... 

---