Exposure assessment definition

The terms below have been adopted or adapted from existing definitions for use in the context of human exposure assessment. Definitions of additional terms used in this document may be found in the IPCS risk assessment terminology Harmonization Project Document (IPCS, 2004). 

It may often be useful to initially conduct an exposure assessment based on worst-case assumptions, and to use default values when model calculations are applied. Such an approach can also be used in the absence of sufficiently detailed data. If the outcome of the risk characterization based on worst-case exposure assumptions is that the substance is not of concern, the risk assessment for that substance can be stopped with regard to the effect/population considered. If, in contrast, the outcome is that a substance is of concern, the assessment must, if possible, be refined using a more realistic exposure prediction in order to come to a definitive conclusion. 

This chapter provides the context, concepts and definitions related to uncertainty analysis in exposure assessment that are necessary to an understanding of subsequent chapters in the monograph. 

To address these questions, an exposure assessment should begin with a definition of the assessment objective (section 2.2.1). From this follows the need to define and evaluate the conceptual exposure model (section 2.2.2). The goal of the conceptual model is to establish exposure links via exposure pathways to exposure routes and relative magnitude of uptake or intake by different exposure routes. These questions are discussed in more detail in section 5.4 with respect to interpretation of the results of a probabilistic exposure assessment. 

Exposure assessment, however, is a highly complex process having different levels of uncertainties, with qualitative and quantitative consequences. Exposure assessors must consider many different types of sources of exposures, the physical, chemical and biological characteristics of substances that influence their fate and transport in the environment and their uptake, individual mobility and behaviours, and different exposure routes and pathways, among others. These complexities make it important to begin with a clear definition of the conceptual model and a focus on how uncertainty and variability play out as one builds from the conceptual model towards the mathematical/statistical model. 

Because the objective of an exposure assessment is to characterize both the magnitude and the reliability of exposure scenarios, planning for an uncertainty analysis is a key element of an exposure assessment. The aims of the uncertainty analysis in this context are to individually and jointly characterize and quantify the exposure prediction uncertainties resulting from each step of the analysis. In performing an uncertainty analysis, typically the main sources of uncertainties are first characterized qualitatively and then quantified using a tiered approach (see chapter 4). In general, exposure uncertainty analyses attempt to differentiate between key sources of uncertainties scenario uncertainties, model uncertainties and parameter uncertainties (for definitions, see section 3.2). 

The definition of the scope and purpose of each exposure assessment provides the specifications for building the exposure scenario, which represents the real-life situation that is to be assessed and provides the boundary limits of the assessment. As pointed out... 

For the purposes of this document, the term data is defined broadly based on the description of exposure assessment detailed in IPCS (2004) and covers a wide variety of measurements, methods, modelling and survey information relevant to a given exposure assessment. The definition of data also includes the many elements of exposure assessment, from the development of exposure scenarios to the details of how they are modelled, to the selection of model input parameters and ultimately to how the results and their uncertainties are characterized and communicated to others (see text box for more detailed definitions). 

TOWARDS A BROADER DEFINITION OF QUALITY IN EXPOSURE ASSESSMENT HALLMARKS OF DATA QUALITY... 

Data that successfully meet the challenges posed in these questions can be said to exhibit certain distinctive characteristics—hallmarks, as we have called them in this document—that are indicative of data quality appropriateness, accuracy, integrity and transparency. Table 1 provides a brief overview of the hallmarks, their definitions and some general examples. As the summary table indicates, these four hallmarks of data quality are closely related and may in some cases overlap. In particular, the need for transparency in documentation and communication cuts across each of the other hallmarks. In the paragraphs that follow, we define each hallmark in greater detail and illustrate how implementation of the principles they embody can improve the quality of exposure assessments and the decisions that follow from them. 

An important similarity between human and ecological assessment of mixtures is the structure of the assessment procedure. Both procedures are often organized along a series of consecutive steps, that is, problem definition, hazard identification, exposure assessment, effect- or dose-response assessment, and risk characterization... 

Identifying a hazard is only a small part of the risk assessment process. Hazard must be differentiated from risk. Assessing risk involves an analysis of the likelihood that adverse effects to human health or the environment after exposure to a chemical may occur. For risk management, exposure assessments therefore play equal (if not more) important parts as evaluations of hazard. The following sections discuss how toxicology, exposure assessments, and risk characterisations contribute to the central scientific definition of risk as probability versus consequence [93-95]. 

Within the exposure assessment, the definition of the conditions under which the substance is manufactured and used is critical in order to determine the levels of exposure. The information on the conditions under which a substance is manufactured and used is called the exposure scenario under REACH. For each exposure scenario, the exposure levels of humans and the environment need to be determined. 

Code of Federal Regulations (CRC) (2013) 21CFC170.3, Title 21, Vol. 3, Part 170, Food Additives Section 170.3(i) Definitions definition of safety. htqD //www.accessdata.fda.gov/ scripts/cdrh/cfdocs/cfCFR/CFRSearch.cfm fr=170.3. Accessed 20 Oct 2013 Cushen M, Kerry J, Morris M et al (2013) Migration and exposure assessment of silver from a PVC nanocomposite. Food Chem 139(l-4) 389-397 de Azeredo HMC (2013) Antimicrobial nanostructures in food packaging. Trends Food Sci Technol 30(l) 56-69... 

E1 The Extent of Population Exposure to Assess Clinical Safety for Drugs Intended for Long-Term Treatment of Non-Life Threatening Conditions E2A Clinical Safety Data Management Definitions and Standards for Expedited Reporting... 

Envlroiunental testing Is a critical element In this process since It enables the qualitative and quantitative determination of toxic chemicals In the environment and the definition of environmental pathways which may lead to human exposure This paper briefly reviews the overall process of health risk assessments and the particular role which environmental testing plays Recent efforts to assess environmental health risks In relation to Love Canal Illustrate both the usefulness and the limitations of environmental testing In risk assessment ... 

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