Hazard and Exposure Assessment

Once the hazard and exposure assessments ate complete for any specific hazard, it is relatively simple to determine how many people will be affected and the severity of the effect (i.e., the risk). It is considerably more difficult to decide whether these risks are warranted compared to the benefits. This is particularly true if the risks are uncertain, involuntary, or not understood by those at risk if those at risk are not primarily those who benefit or if alternatives are unknown, uncertain, or impractical. The process is complex because the goals are multiple and frequently contraindicating. 

Change can be expected in almost every aspect of both the applied and the fundamental aspects of toxicology. Risk communication, risk assessment, hazard and exposure assessment, in vivo toxicity, development of selective chemicals, in vitro toxicology, and biochemical and molecular toxicology will all change, as will the integration of all of these areas into new paradigms of risk assessment and of the ways in which chemicals affect human health and the environment. 

Integrate hazard analyses to identify worker hazards and to provide a basis for speeifieation of job and task hazard eontrols. (The upeoming seetion eovering hazard eharaeterization and exposure assessment will provide some suggestions on effeetive ways of eondueting hazard analyses using the HAZWOPER job, task, and hazard analysis approaeh [1].)... 

Wlien utility work is located in an exclusion zone, are workers who enter the area exposed to hazardous materials Hazard characterization and exposure assessment performed by a competent person may show that the area surrounding the equipment and an access corridor leading to the equipment can be cleaned so that the utility workers can work in the... 

Critical to hazard characterization is the identification of hazards and the assessment of possible worker exposure. This can be accomplished in a variety of ways. As described before, one commonly used technique is a JHA with project teams that include the worker. The information collected is used by the SSHO and the radiation control officer to develop an appropriate hazard control and protection strategy. 

Work zones are designed to control access to actual and anticipated hazards. Work zone positioning is based on hazard characterization and exposure assessment. Anticipated work activity, potential releases, and the amount of contaminant dispersion are important for delineating these zones [3]. 

Condueting a hazard eharaeterization and exposure assessment to identify ... 

At present the approach to assessing the potential risks of exposure to a chemical in the diet involves the application of a standardised risk assessment approach consisting of three main elements - hazard identification and characterisation and exposure assessment. 

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. ... 

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-... 

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... 

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... 

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... 

Plants used to produce PRPs should be amenable to confinement . Isolation distances were increased, and the cultivation of food and feed crops following a PRP crop was discouraged. New hazard and exposure data for human and livestock health assessment may also be required from PRP-containing traditional food or feed crops prior to the approval of field trials. Exposure risk concerns the potential for PRPs to be present in human food or animal feed, and where exposure can occur, what mechanisms are used to limit biological activity. Hazards included direct toxicity and allergenicity in humans or animals as well as hazards presented by the coproduct streams that result from processing. These latter requirements could place a major burden on proponents to prove their materials are safe prior to even confined field trials. 

In the final phase of risk analysis—risk characterization—one integrates outputs of effects and exposure assessments. Risk is expressed in qualitative or quantitative estimates by comparison with reference values (e.g., hazard quotient). The severity of potential or actual damage should be characterized with the degree of uncertainty of risk estimates. Assumptions, data uncertainties and limitations of analyses are to be described clearly and reflected in the conclusions. The final product is a report that communicates to the affected and interested parties the analysis findings (Byrd and Cothern, 2000). 

In many cases, hazard based substitution eliminates the need for notoriously difficult exposure assessment. Persistence and bioaccumulation potential are surrogate measures of both hazard and exposure that can be applied quickly to all chemicals In order to identify those of greatest concern. 

Another model, used in the USA, is the OASYS Pollution Prevention Optional Analysis System, developed by the Toxic Use Reduction Institute. Technologies are assessed on a variety of hazard criteria, including acute and chronic human toxicity, physical properties, aquatic impacts, persistence/bioaccumulation, atmospheric releases, disposal, chemical properties, energy/resource use, product hazard and exposure potential. Alternatives are rated to... 

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. 

The aim of the risk characterization of a chemical substance under evaluation is to integrate the hazard assessment and exposure assessment in order to evaluate the qualitative and quantitative probability for a health risk likely to occur in a given human population due to actual or predicted exposure to that specific chemical as well as the seriousness of any health risk. 

Hazard assessment and exposure assessment of chemicals are generally common stages performed similarly independent of the chemical use category (industrial chemical, pesticide, biocide, food additive, food contact material, etc.). However, variation occurs in the way in which the exposure assessment and hazard assessment information are integrated in the risk characterization step, depending on the regulation involved and the goal of the risk assessment. This wdl be addressed in more detail in the next section. 

Risk characterization is thus the step in the risk assessment process where the outcome of the exposure assessment (e.g., daily intake via food and drinking water, or via inhalation of airborne substances) and the hazard (effects) assessment (e.g., NOAEL and tolerable intake) are compared. If possible, an uncertainty analysis should be carried out, which produces an estimation of the risk. Several questions should be answered before comparison of hazard and exposure is made ... 

Pre.sents the. steps in ri.sk as.ses.sment, including hazard identification, exposure assessment, and risk characterization... 

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 (also referred to in the CTSA process as risk integration) is the integration of hazard and exposure information to quantitatively or qualitatively assess risk. 

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. 

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. 

The conditions under which the drug is used need to be estimated as do acceptable residues linked to the level of acceptable risk to the consumer. The acceptable level of risk, which is determined in theory at the risk management stage, has already been expressed in terms of residues by the ADI under hazard characterization. Moreover, the elements considered for hazard identification, hazard characterization, and exposure assessment make it possible, for a given form of utilization of a particular substance, to establish a profile of residues in animal tissues and to associate this with a profile of consumer exposure. Comparison of this consumer profile and ADI indicates whether the mode of utilization of the substance is acceptable or not. Analysis of the different results of residue content in animal products then provides an indication of level of residues in one or several animal tissues, making it possible to differentiate between veterinary drug applications that do or do not permit compliance with the ADI. 

Hazard or dose-response assessment the attempt to assemble the hazard and exposure information along with mathematical models to estimate an upper bound on the carcinogenic risk at a given dose. 

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