Exposure assessments forms

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... 

The exposure assessment could be performed for a single exposure scenario, or be more comprehensive including several exposure scenarios. In some simations, the estimated exposure from a single scenario is taken forward to the risk characterization while for other purposes, the estimated exposures from various scenarios form the basis for an estimation of a combined exposure to the chemical under evaluation from all characterized exposure scenarios. 

Exposure assessment The qualitative and/or quantitative assessment of the chemical nature, form and concentration of a chemical to which an identified population is exposed from all sources (air, water, soil and diet). 

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. 

Describe the conditions of waste disposal. Wastes in specified physical and chemical forms and having certain compositions or ranges of compositions of hazardous substances are assumed to be emplaced in certain ways in a disposal site having specified characteristics. The disposal site can be a real location or generic with hypothetical characteristics typical of real sites. The exposure assessment usually assumes that disposal operations have been completed and the site is closed, although the... 

The nature and extent of the qualitative characterization of these sources of uncertainty are necessarily dependent on the objective of the exposure assessment and the appropriate form of output for its intended purpose. Prior to initiating the development of any assessment, its intended purpose must be clearly articulated. 

What are the key sources of uncertainty in the exposure assessment This question can also be posed as Which exposure factors contribute the most to the overall uncertainty in the inventory This insight can be used, in turn, to target resources to reduce the largest and most important uncertainties. There are various ways to answer this question, including various forms of sensitivity analysis. For example, in the context of a probabilistic uncertainty simulation for an overall exposure assessment, various statistical methods can be used to determine which input distributions are responsible for contributing the most to the variance of the output. 

An especially useful form of validation is where the results of an assessment can be compared with independent data or information (e.g. comparing predicted exposure with biomarker measurements or epidemiological studies). When making such comparisons, it is important to remember that both sides of the comparison are subject to uncertainty. The methods described in this document should be applied to the independent data, as well as to the exposure assessment, to provide a fair comparison between the two. 

The general intake model used for the case-study is adapted from a USEPA model. We use this model in the form adopted for generalized multipathway exposure modelling as described in Chapter 6 of IPCS Environmental Health Criteria 214, Human Exposure Assessment (IPCS, 2000). In this form, the model expresses the potential average daily intake or potential daily dose, ADDpot, over an averaging time, AT, as... 

Data are thus considered to be any information that contributes to, or is relevant to, a particular exposure assessment.3 The term encompasses not just numerical values or estimates, but also information provided in other forms, such as default values adopted for regulatory purposes, theory developed from first principles or basic science, computer programs, surveys, demographic data, census information, graphs, mathematical formulae, subjective expert judgements and descriptive summaries. More detail on the diversity of information that contributes to exposure assessment may be found in the other IPCS risk assessment documents, shown in Figure 1 (IPCS, 2000, 2004, 2005 Part 1 of this document). 

Environmental exposures form the basis for determining indirect exposures to the general public that will usually occur during a lifetime. Direct consumer exposure assessments prove equally challenging, and may vary from acute to chronic exposure scenarios. Ideally the data set for consumer exposure from a substance in a product should include [127] ... 

The models and methods used for purposes of estimating potential residential exposure (and absorbed dose) continue to be refined and validated as new monitoring studies become available. The goal is to simulate actual exposure conditions as closely as possible. The following sections present an example of a simplistic screening-level exposure assessment calculation for a consumer product, followed by a discussion of how more refined, probability-based or uncertainty analysis methods can be used. Screening-level methods typically include conservative bias in the form of default assumptions that are used in the absence of directly relevant and robust exposure monitoring data and other information. These methods can be used to predict potential exposure. However, it... 

Screening-level or initial tier predictive exposure assessment methods typically involve the use of an algebraic equation that expresses exposure or absorbed dose as a function of the concentration of a chemical in relevant media (e.g., air, food, and water) and other important factors. For example, inhalation exposure (Emh) to an airborne chemical can be estimated using some form of the following equation ... 

Chemical Dosimetry bv TSP LC/MS. One of our long-term objectives in studying TSP LC/MS is the development of chemical dosimetry based on direct determination of polar metabolites in biological fluids. Most toxic substance exposure scenarios (i.e., near hazardous waste sites) involve complex and variable mixtures of substances. Biological monitoring, where human fluids, tissues and excreta are analyzed, measures actual exposure, whereas analysis of soil, air or water can only provide an estimate of potential exposure. Exposure data forms the basis of human health risk assessment, and ultimately defines cleanup requirements at contaminated sites. 

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