Hazards exposure and risk

Kavlock R, Dix D (2010) Computational toxicology as implemented by the U.S. EPA providing high throughput decision support tools for screening and assessing chemical exposure, hazard and risk. J Toxicol Environ Health B Crit Rev 13(2 ) 197-217... 

Considering and examining all available evidence on exposure, hazard, and risk in an interdisciplinary manner, to take account of variability as well as direct and indirect, cumulative, and interactive effects. 

ZIO does not give separate treatment to occupational health exposures. Hazards and risks pertaining to injuries and illnesses are treated as parts of a whole. Also, although no provision requiring access to certified professional resources exists in ZIO, applying many of the provisions in ZIO wiU require the counsel of highly qualified professionals. 

Contains the health hazards and risks, toxicological data, and first aid procedures Exposure routes and limits signs and symptoms target organs and medical conditions aggravated by exposure. 

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... 

A note of caution is appropriate at this juncture as many confuse the inherent hazard of materials with risk. This will be covered in slightly greater detail later in this chapter, but it is important to distinguish between hazard and risk. Risk is defined as being a function of the inherent hazard of a material and the potential, or likelihood, for exposure ... 

A Resources to identify chemicals of concern B Chemical toxicity C Exposure assessment tools D Hazard and risk assessment tools E Safer chemistry design tools... 

Sikov MR. 1992. Hazards and risks from prenatal irradiation Emphasis on internal radionuclide exposures. Radiat Prot Dosim 41(2-4) 265-272. 

Computed parameters are Concentration, exposure (to concentration) dosage hazard (health risk to Individual) exposure (to hazard) and risk (health risk to population). 

In this chapter the risk assessment is briefly introduced. Risk assessment is divided into four steps hazard identification, hazard characterization, exposure assessment, and risk characterization. This chapter also highlights five risk and life cycle impact assessment models (EUSES, USEtox, GLOBOX, SADA, and MAFRAM) that allows for assessment of risks to human health and the environment. In addition other 12 models were appointed. Finally, in the last section of this chapter, there is a compilation of useful data sources for risk assessment. The data source selection is essential to obtain high quality data. This source selection is divided into two parts. First, six frequently used databases for physicochemical... 

Comparative Toxicokinetics. The absorption, distribution, metabolism, and excretion of acrylonitrile in rats has been studied. Limited work in other species suggests that important species differences do exist. Further evaluation of these differences, and comparison of metabolic patterns in humans with those of animals would assist in determining the most appropriate animal species for evaluating the hazard and risk of human exposure to acrylonitrile. 

The distinction between hazard and risk can be made clearer by the use of a simple example. A large number of chemicals have hazardous properties. Acids may be corrosive or irritating to human beings for instance. The same acid is only a risk to human health if humans are exposed to it. The degree of harm caused by the exposure will depend on the specific exposure scenario. If a human only comes into contact with the acid after it has been heavily diluted, the risk of harm will be minimal but the hazardous property of the chemical will remain unchanged. 

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 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. 

The Concise International Chemical Assessment Documents (CICADs) (see Figure 2.3) are similar to the EHC documents in providing internationally accepted reviews on the effects on human health and the environment of chemicals or combinations of chemicals. They aim to characterize the hazard and dose-response of exposure to chemicals and to provide examples of exposure estimation and risk characterizations for application at the national or local level. They summarize the information considered critical for risk characterization in sufficient detail to allow independent assessment, but are concise, i.e., not repeating all the information available on a particular chemical. For more detail, readers of individual CICADs are referred to the original source document for the CICAD (either a national or regional chemical evaluation document) or an existing EHC (chemicals series). 

As mentioned previously, the assessment of hazard and risk to humans from exposure to chemical substances is generally based on the extrapolation from data obtained in smdies with experimental animals. In the absence of comparative data in humans, a basic assumption for toxicological risk assessment is that effects observed in laboratory animals are relevant for humans, i.e., would also be expressed in humans. In assessing the risk to humans, an assessment factor is applied to take account of uncertainties in the differences in sensitivity to the test substance between the species, i.e., to account for interspecies variability (Section 5.3). If data are available from more than one species or strain, the hazard and risk assessment is generally based on the most susceptible of these except where data strongly indicate that a particular species is more similar to man than the others with respect to toxicokinetics and/or toxicodynamics. Two main aspects of toxicity, toxicokinetics and toxicodynamics, account for the namre and extent of differences between species in their sensitivity to xenobiotics this is addressed in detail in Chapter 5. 

Concern has been raised that infants and children are at higher risk than adults from exposure to environmental chemicals. The question of an extra assessment factor in the hazard and risk assessment for chemicals of concern for children has therefore been raised and the rationale for such a children-specific assessment factor has been discussed. 

Risk assessment 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. It includes the components of hazard identification, assessment of dose-response relationships, exposure assessment and risk characterization. 

As discussed above, the risk of chemicals in the environment is dependent on both exposure and toxicity. Pathways through which organisms in the environment are exposed to chemicals are therefore key determinants of how safe (and therefore, how green ) a chemical is, and must be considered in moving towards a reduced risk or hazard approach to the production and use of chemicals. Fate in the environment is the principal determinant of exposure and designing chemicals for reduced hazard and risk to the environment involves consideration of processes that affect the chemical in the environment, in addition to toxicity. Assessment of environmental fate, including design of chemicals for nonpersistence, is discussed in detail in Chapter 16. 

For nanomaterials this is especially true if the exposure scenarios used in the test system are not representative of those likely to be found in the field [91, 92]. For example, the degree of toxicity observed in aquatic invertebrates exposed to multi-walled nanotubes (MWNTs) in water and sediment was influenced by the functional groups on the MWNTs and their preparation for dispersal into the test systems [93]. As noted, even the concept of what constitutes nanomaterials is not fixed [87], so these emerging materials will likely require a rethinking of how their toxicity is assessed and the hazards and risks they might pose to ecosystems [90]. For more information on nanomaterials, including application of life-cycle concepts to their design, see Chapter 8. 

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. 

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