Hazard Identification and Characterization

Hazard assessment begins with assembling information regarding the potential physical/chemical hazards or toxicity of a chemical. The risk assessor may seek to characterize  

Hazard characterization may consider both acute and chronic effects. Acute effects occur in the short term chronic effects result from longer-term exposure. 

This information may derive from laboratory testing. Alternatively, toxicologists may predict hazards from a structure-activity relationship (SAR), which is the relationship of the molecular structure of a chemical with a physicochemical property, environmental fate attribute, and/or specific effect on human health or an environmental species. These correlations may be qualitative (simple SAR) or quantitative (quantitative SAR, or QSAR) [79, p. 1]. Both read across from the behavior of one chemical to that of a similar chemical and the practice of assessing chemicals by categories are forms of SAR [80,81]. 

Assessment endpoints have often included those listed in Table 2.4 the endpoints considered in a risk assessment may depend on the nature of the substance and the applicable regulatory regime, among other factors, and can include effects other than those tabulated (e.g., see [82]). Table 2.4 also includes environmental behaviors relevant to short- and long-term exposure that may be considered during the risk assessment. 

Toxicologists typically quantify the response of test organisms to a chemical dose and then extrapolate from those test data, incorporating various margins of safety, to develop benchmarks used in risk assessment. Some of the most important benchmarks are described below using the jargon applied to the process in the European Union and the United States [84-86]. 

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This chapter will review the application of these methods for the hazard identification and characterization of chemical allergens and, where appropriate, for the measurement of relative potency in the context of risk assessment. 

Prevention and intervention efforts are a major focus of NIEHS activities. These efforts include hazard identification and characterization, both through... 

Additional parameters that are readily incorporated into a stand-alone immune function test such as the KLH-TDAR model include ex vivo lymphocyte proliferation, cytokine protein expression, and immunophenotype analysis any or all of which can enhance hazard identification and characterization of a potential immunotoxicant. While the KLH-TDAR is an example of a combined immune function screen and mechanistic study, the ex vivo methodologies described herein are generally applicable to toxicology studies that do not include an immunization protocol. Moreover, the methodologies are not species-specific however, responsiveness to various stimulants to induce ex vivo lymphocyte proliferation and cytokine production may differ across species and strain, requiring procedural optimization for a given species and ex vivo test. 

The Pantex Emergency Hazards Assessment (MNL-190881) includes quantitative hazards analyses of onsite chemicals lhat exceed either the TQ in 29 CFR 1910.119, or the TPQ in 40 CFR 355 Appendix A. This document includes hazard identification and characterization, development of accident scenarios, and consequence analysis using airborne dispersion modeling. 

After compiling data, the registrant must perform a hazard assessmenf [97]. (This step corresponds to hazard identification and characterization in the generic risk assessment process described in Chapter 2.) ECHA describes this process as follows [98, p. 5] ... 

The remaining step in the hazard identification and risk assessment procedure shown in Figure 1 is to decide on risk acceptance. For this step, few resources are available and analysts are left basically by themselves. Some companies have formal risk acceptance criteria. Most companies, however, use the results on a relative basis. That is, the results are compared to another process or processes where hazards and risks are weU-characterized. 

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. 

The degree of confidence in the final estimation of risk depends on variability, uncertainty, and assumptions identified in all previous steps. The nature of the information available for risk characterization and the associated uncertainties can vary widely, and no single approach is suitable for all hazard and exposure scenarios. In cases in which risk characterization is concluded before human exposure occurs, for example, with food additives that require prior approval, both hazard identification and hazard characterization are largely dependent on animal experiments. And exposure is a theoretical estimate based on predicted uses or residue levels. In contrast, in cases of prior human exposure, hazard identification and hazard characterization may be based on studies in humans and exposure assessment can be based on real-life, actual intake measurements. The influence of estimates and assumptions can be evaluated by using sensitivity and uncertainty analyses. - Risk assessment procedures differ in a range of possible options from relatively unso-... 

Due to this, it is necessary to assess the risk to human health and the environment due to the exposure to these chemical additives. In this chapter the impacts that a substance can cause to a certain receptor (humans and the environment) and the harms to the receptor at different exposure levels are identified in hazard identification and hazard characterization steps, respectively. Exposure assessment takes into account the amount, frequency, and duration of the exposure to the substance. Finally, risk characterization evaluates the increased risk caused by such exposure to the exposed population. 

For the two aforementioned steps, hazard identification and hazard characterization, data adequacy is of high importance. The data adequacy is defined by the reliability and the relevance of the data for human risk assessment [3],... 

The process includes hazard identification and hazard characterization. The process focuses on the hazard in contrast to risk assessment where exposure assessment is a distinct additional step. 

The risk assessment comprises an effect assessment (hazard identification and hazard characterization) and an exposure assessment. The principles for the effect assessment of the active substances are in principle similar to those for existing and new chemicals and are addressed in detail in Chapter 4. Based on the outcome of the effect assessment, an Acceptable Daily Intake (ADI) and an Acceptable Operator Exposure Level (AOEL) are derived, usually from the NOAEL by applying an overall assessment factor addressing differences between experimental effect assessment data (usually from animal studies) and the real human exposure situation, taking into account variability and uncertainty for further details the reader is referred to Chapter 5. As a part of the effect assessment, classification and labeling of the active substance according to the criteria laid down in Directive 67/548/EEC (EEC 1967) is also addressed (Section 2.4.1.8). 

Hazard assessment is A process designed to determine the possible adverse effects of an agent or simation to which an organism, system or (sub) population could be exposed. The process includes hazard identification and hazard characterization. The process focuses on the hazard in contrast to risk assessment where exposure assessment is a distinct additional step. ... 

During both steps of the hazard assessment, hazard identification and hazard characterization, it is important to evaluate the available data with regard to their adequacy and completeness. The evaluation of adequacy shall address the reliability and relevance of the data. These aspects are addressed in detail in Chapter 3. 

Risk characterization The synthesis of critically evaluated information and data from exposure assessment, hazard identification and dose-response considerations into a summary that identifies clearly the... 

Risk assessment, a process used to evaluate potential adverse effects on health from human exposure to veterinary drug residues, involves four stages starting from hazard identification and terminating through the hazard characterization and exposure assessment stages to risk characterization. 

Risk characterization The synthesis of critically evaluated information and data from exposure assessment, hazard identification, and dose-response considerations into a summary that identifies clearly the strengths and weaknesses of the database, the criteria applied to evaluation and validation of all aspects of methodology, and the conclusions reached from the review of scientific information. 

In the evaluation of carcinogenicity of chemicals, data obtained from human and animal studies are analyzed for hazard identification and dose-response relationships. The results are used in combination with exposure assessment and risk characterization for the assessment of cancer risks of the chemicals to humans. 

The US government s new approach (2000) to health assessment of agents involves the iterative interaction of four major components basic scientific research (hazard identification), science-based toxicity/risk assessment (dose-response assessment), exposure assessment, and risk characterization (Figure 2). This section relies heavily on the US EPA guidelines for the health assessment of suspect developmental toxicants which describe how the government uses, and plans to use, developmental toxicity data as part of their weight-of-evidence approach to both the hazard identification and the dose-response assessment components of risk assessment. 

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