Hazard Characterization and Exposure Assessment

In Chapter 4 we will diseuss the regulatory framework and analyti-eal tools to eonduet these assessments, sueh as JHA (job hazard analysis), job safety analysis (JSA), safety analysis reports, proeess hazard analysis (PHA), and job, task, and hazard analysis. The reader needs to understand that OSHAs view on physieal and ehemieal hazards is far reaehing, as stated in the HAZWOPER standard. Note the following examples. 

Keep in mind that should a eonfliet exist in applieability in the CER the more proteetive, or stringent applies. Typieally, on a mid to large HAZWOPER site you will eneounter a situation that is eovered by more than one OSH A standard. 

Notice that published exposure levels are specifically mentioned. In the past, many felt that the only exposure limits that must be adhered to were permissible exposure limits, or PELs. This wording makes it clear that employers need to also consider reputable studies involving substances not found in the PELs. 

Here again, published exposure levels are specifically mentioned when no PELs exist. Considering published exposure levels while monitoring is not often found in OSHA standards. The authors believe that utilizing all available hazard information can give you a better opportunity to adequately protect workers. 

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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... 

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]. 

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. 

All leading food industries have to perform thorough risk assessments in the preservation of food products (Van Gerwen et al., 2000 Hoornstra and Notermans, 2001). The crucial point then is analysis of the production process as a whole, the so-called from farm to fork and consists of four subprocesses that are executed systematically (1) hazard identification, (2) hazard characterization, (3) exposure assessment, and (4) risk characterization (Brul et al., 2002). 

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

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-... 

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). 

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). 

The approach to exposure assessment is not as internationally harmonized as hazard assessment. A synopsis of current activities regarding exposure assessment for industrial chemicals in a number of OECD Member countries has been published (OECD 2006). The executive summary of this document states that while there is a significant level of sharing of approaches used for hazard characterization for risk assessment, this is not the case for exposure characterization. Although broad consistency in the overall approaches used by different countries in conducting exposure assessment exists, there is variation in policy-related factors, including the regulatory context for assessment and the way that information is applied, as well as in the types of approaches and tools used. 

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 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. 

Figure 5.1 Risk assessment is traditionally organized in a series of consecutive steps—1) hazard identification, 2) exposure assessment, 3) effect assessment, and 4) risk characterization—and generally embedded in a wider framework involving research, problem formulation, risk management, and action.

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... 

This summary serves as the starting materials for the overall risk characterization process that completes the risk assessment. This chapter will concentrate on a specific feature of this risk characterization process, namely the importance of developing approaches for incorporating mechanistic data into the hazard, dose-response, and exposure assessments to reduce uncertainties in the process and thereby reduce the reliance on default factors that are used in the absence of reliable data. Given that the risk characterization is for the estimation of risks to humans from low, enviromnental exposures, then the issues that cover the necessary defaults are as follows (see Rart I, this volume) ... 

Risk characterization combines the results of the hazard assessment and exposure assessment to project the potential risk to human health or the environment. The way in which it is done in the European Union under REACH illustrates the process [76]. 

The size and quality of the available database for an environmental pollutant will vary greatly across substances and will also vary within the four components of the typical risk assessment. The variety of adverse health risks of a substance may be qualitatively well known, for example, but dose—response relationships may be poorly quantifiable because of either limits of inadequate exposure measurement data or absence of good biomarkers of adverse effect or absence of information on the full span of the dose—response curve. Hazard characterization and dose—response relationships may both be understood as general descriptors, but case-specific or scenario-specific exposure data may be lacking, requiring judgment about alternative approaches (e.g., default values). 

The final step in the risk assessment methodology employed here for environmental contaminants is quantification of the extent of risks to health in various human populations. This step combines the general elements of hazard characterization and dose—toxic response relationships for lead with case-specific data quantifying the extent of toxic exposure to arrive at some quantitative value for risk. Various regulatory entities differ in the specifics of how this methodological template is applied but retain these broad features. 

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. 

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