Hazard characterization effects

Hazard characterization and delineation of dose-effect or dose-response relationships. 3. Assessment of exposure 4. Risk characterization... 

Hazard characterization is a quantitative or semi-quantitative evaluation of the nature, severity, and duration of adverse health effects associated with biological, physical, or chemical agents that may be present in food. The characterization depends on the nature of the toxic effect or hazard. Eor some hazards such as genotoxic chemicals, there may be no threshold for the effect and therefore estimates are made of the possible magnitude of the risk at human exposure level (dose-response extrapolation). 

Stages in hazard characterization according to the European Commission s Scientific Steering Committee are (1) establishment of the dose-response relationship for each critical effect (2) identification of the most sensitive species and strain (3) characterization of the mode of action and mechanisms of critical effects (including the possible roles of active metabolites) (4) high to low dose (exposure) extrapolation and interspecies extrapolation and (5) evaluation of factors that can influence severity and duration of adverse health effects. 

Risk characterization is the last step in the risk assessment procedure. It is the quantitative or semi-quantitative estimation, including uncertainties, of frequency and severity of known or potential adverse health effects in a given population based on the previous steps. Risk characterization is the step that integrates information on hazard and exposure to estimate the magnitude of a risk. Comparison of the numerical output of hazard characterization with the estimated intake will give an indication of whether the estimated intake is a health concern. ... 

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). 

Hazard characterization is the estimation of the relationship between the dose of a substance and the effects observed. To evaluate this relationship, the following studies can be performed (in order of reliability) ... 

Related terms Hazard Characterization, Dose-Effect Relationship, Effect Assessment, Dose—Response Relationship, Concentration—Effect Relationship. 

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). 

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. ... 

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. 

The basis of the recommended approach to a hazard assessment of the potential immunotoxicity of a substance is that many immunotoxic substances can be identified via the standard tests for systemic toxicity. Special smdies to characterize effects of concern for immunotoxicity are used only when necessary for adequate hazard assessment. The nature of special smdies, and when they should be conducted, need to be decided on a case-by-case basis. A tiered approach to the identification of immunotoxic hazard in routine toxicology is described in WHO/IPCS (1996). 

Hazard identification is the first step in the process of risk assessment, and hazard characterization is the second step. The hazard assessment is also known as effect assessment and is addressed in detail in Chapter 4. 

The evaluation of dose-response relationships is a critical component of hazard characterization (OECD, 1989 ECETOC, 1992 US , 1997a IPCS, 1999). Evidence for a dose-response relationship is an important criterion in establishing a toxic reproductive effect. It includes the evaluation of data from both human and laboratory animal studies. Because quantitative data on human dose-response relationships are infrequently available, the dose-response evaluation is usually based on the assessment of data from tests performed using laboratory animals. However, if data are available in humans with a sufficient range of doses, dose-response relationships in humans can also be evaluated. 

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 final stage of risk assessment, sets out to provide a qualitative and/or quantitative estimate, given the uncertainties of assessment, the probability of occurrence, and the severity of known or potential adverse health effects in a given population based on hazard identification, hazard characterization, and exposure assessment. The aim is to characterize the risks to the consumer from residues possibly present in animal products on the basis of use of the substance and particularly the withdrawal period, given that the period of administration and the dosage are predetermined by the objective of effectiveness. 

Hazard Characterization. Once chemicals have been identified as mutagens, they can be classified according to their relative potency and spectrum of effects. The activity of mutagenic chemicals varies markedly, as does the nature of the damage they cause. 

Risk assessment is an empirically based process that estimates the risk of adverse health effects from exposure of an individual or population to a chemical, physical, or biological agent or property. The health risk assessment process involves the following steps hazard identification, effects assessment (dose-response assessment), exposure assessment, and risk characterization (Van Leeuwen and Vermeire 2007). 

Although human exposure data are essential for accurate evaluation of an agent s risk potential, data of sufficient quality and quantity are frequently unavailable. Thus, there is uncertainty in the exposure component of the evaluative process, even as there is in hazard characterization. When toxicity data indicate the potential for an adverse effect, the need to estimate the nature of human exposure becomes imperative. In those instances, exposure estimates can be derived using modeling approaches based on data from other sources, and one or more default assumptions can be used. The greater the number of default assumptions employed, the greater the uncertainty about the accuracy of the expert judgment. 

Mechanistic data for cancer are considered in hazard characterization in the context of mode of induction of toxic effects. A postulated mode of action is a biologically plausible sequence of key events leading to an observed effect supported by robust experimental observations and mechanistic data. It describes key cytologi-cal, genetic, and biochemical events— that is, those that are both measurable and necessary to the observed effect. Mode of action is contrasted with mechanism of action, which generally involves a much greater understanding of the molecular basis for an effect. 

Risk assessment is usually divided into four steps hazard identification, hazard characterization, exposure assessment, and, finally, risk characterization [1]. In hazard identification, agents capable of exerting negative health effects are identified. Often, the first indications of toxic potential of a compound or mixture are derived from epidemiological studies. The advantage of epidemiological studies is that extrapolation from experimental animal studies is unnecessary. On the other hand, indications from epidemiological studies show that unwanted exposure has already taken place. For marine biotoxins in bivalve mollusks, all known syndromes have been detected as a result of... 

Hazard characterization consists of qualitative or quantitative evaluation of the adverse health effects associated with different agents, whether they are chemicals or microorganisms. This step comprises several elements, like toxicokinetics (absorption, distribution, metabolism, and excretion of the toxic agent), mechanism of toxic action, dose-response relationships, target organs and different end points, like acute or chronic toxicity, teratogenicity, neoplastic manifestations, and so forth. 

Hazard characterization Data on toxicokinetics for the AZA group are lacking, mainly due to lack of availability of pure toxins. Also, information on the mechanism of action is scarce, but they do not inhibit protein phosphatise 2A, which is the main mechanism of DSP toxins [3]. Results from in vitro studies have shown multiple effects like cytoskeleton disruption [32], increased levels of cytosolic calcium and cAMP [33,34], and cytotoxicity towards multiple cell types [3]. 

Hazard characterizations cannot address undiscovered or unappreciated health effects. The limited information available on the health effects of most chemicals makes this a major concern. For example, of the more than 5 million compounds known to science, only about 100,000 are listed in the Registry of the Toxic Effects of Chemicai Substances (RTECS) published by the National Institute for Occupational Safety and Health (NIOSH). Of these 100,000 substances, fewer than 5000 have any toxicity... 

---