Exposure assessment overview

In an attempt to provide an overview and assessment of the POPs in South Korea, we have conducted a comprehensive literature search and compiled the existing POPs data (including the emerging POPs) from surveys conducted since the mid-1990s in South Korea. This chapter presents (1) emission inventories of individual POPs (2) concentrations in various environmental including humans (3) exposure assessment in the ecosystem and humans (4) a case study of fate and multi-media transport of POPs and finally, (5) a proposal for a strategy to minimize releases and ultimately eliminate POPs in South Korea. 

The exposure assessment characterizes the pathways, magnitude, frequency, and duration of human exposures from various sources. Chapter 5 provides an overview of these components and addresses the principles of exposure assessment in children. General principles of exposure assessment have been reviewed in a number of publications (USEPA, 1992a, 2005a IPCS, 1999a, 2000 Needham et al., 2005). This chapter will focus on the considerations that are important when applying the exposure data to a children s health risk assessment (see Box 2). 

The objective of this monograph is to provide an overview on the nature and characterization of uncertainty in exposure assessments, including guidance on the identification of sources of uncertainty, its expression and application, not only in risk assessment, but also in risk management decisions, delineation of critical data gaps and communication to decisionmakers and the public. 

However, since exposure assessment is an interdisciplinary activity, this monograph is also expected to be a useful resource for a wider audience, considering that each group may use the information contained herein for different purposes. The monograph provides an overview of the types of uncertainty encountered by an exposure analyst and provides guidance on how uncertainty can be characterized, analysed and described in a risk assessment and communicated effectively to a range of stakeholders. 

This chapter gives an overview of different sources of uncertainty that may arise at different stages of the exposure assessment. Therefore, this chapter aims to systematically describe the steps of exposure assessment and the related sources of uncertainties. 

Section 3.1 provides a brief overview of approaches and steps typically used in exposure assessment. Next, in section 3.2, a taxonomy of the different sources of uncertainty is given. There are numerous texts providing schemes for the classification of sources of uncertainty. The classification given below follows in outline the one given in the USEPA s Guidelines for Exposure Assessment (USEPA, 1992). 

In view of the often considerable limitations of available data supporting exposure assessment, which sometimes limit the extent of uncertainty quantification and the need to explicitly identify sources of uncertainty prior to their quantification, this section provides an overview of existing concepts and proposes a harmonized approach for the qualitative analysis of uncertainty in exposure assessment. 

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. 

This section outlines the current scientific state of the art in the assessment of human health risks for chemical mixtures. It focuses on the gathering, assessment, and evaluation of effect data. The reader is referred to Chapter 1 for detailed information on exposure assessment of chemical mixtures. The section starts with an overview of methods commonly used to obtain effect data on chemical mixtures. This is followed by an overview of the current mixture approaches in human health assessments, that is, the whole mixture approach for common mixtures and the component-based approach. The section concludes with a paragraph on uncertainties in human health assessments of chemical mixtures. 

Figure 4.3 Overview of non-dietary (residential) exposure assessment...

USEPA (1999b). Overview of Issues Related to the Standard Operating Procedures for Residential Exposure Assessment, Presented to the USEPA Science Advisory Panel for the meeting on September 21, 1999, United States Environmental Protection Agency, Office of Pesticide Programs, Washington, DC, USA. 

Nielsen, A., P. Curry and T. Leighton (1995). The Pesticide Handlers Exposure Database (PHED) Regulatory Overview, in Methods of Pesticide Exposure Assessment, M. Maroni,... 

The mass balance concept serves as the foundation of the Environmental Protection Agency (EPA) guidelines for assessing percutaneous absorption of chemicals (U.S. EPA, 1998). The combined use of the mass balance procedure coupled with detection and measurement of a substance in the stratum comeum and deeper layers of the skin may provide valuable information for exposure assessment. A schematic overview of the EPA Health Effects Test Gnidelines for Dermal Penetration Smdies is presented in Figure 4.2. A few points are highlighted ... 

An overview of the methodology cmd the interconnections cimong the components is shown on figure 8.1. In data evaluation, the conditions at the site cire identified. In this step, we use information about the chemicals present at the site to identify concentrations to which we could be exposed and the spatial extent of contamination. In exposure assessment, we identify how humans could contact chemicals, and estimate possible doses resulting from cissumed levels of exposure. This includes identifying the types of people that could be exposed, cmd by what routes they could be exposed (e.g., ingestion, inhalation). For example, would someone be exposed to lead if it was buried in soil under concrete If the impacted area were an active industrial facility, would you assume children could be exposed In toxicity assess-... 

Fate and exposure analyses. The multimedia transport and transformation model is a dynamic model that can be used to assess time-varying concentrations of contaminants that are placed in soil layers at a time-zero concentration or contaminants released continuously to air, soil, or water. This model is used for determining the distribution of a chemical in the environmental compartments. An overview of the partitioning among the liquid, solid and/or gas phases of individual compartments is presented in Fig. 7. The exposure model encompasses... 

Huckins, J.N. Prest, H.F. Petty, J.D. Lebo, J.A. Hodgins, M.M. Clark, R.C. Alvarez, D.A. Gala, W.R. Steen, A. Gale, R.W Ingersoll, C.G. 2004, Overview and comparison of lipid-containing semipermeable membrane devices (SPMDs) and oysters (Crassostrea gigas) for assessing chemical exposure. Environ. Toxicol. Chem. 23 1617-1628. 

Huckins J.N. Prest H.F Petty J.D. R0e T.I. Meadows J.C. Echols K.R. Lebo J.A. Clark R.C. 1998, A Overview of the Results of Several Comparisons of Lipid-containing Semipermeable Membrane Devices (SPMDs) and Biomonitoring Organisms for Assessing Organic Chemical Exposure. Abstracts of the 19th Annual National Meeting SETAC Charlotte, NC November 15-19, 1998 p 215. 

The reader is also referred to the OECD Guidance Document No. 43 on Reproductive Toxicity Testing and Assessment (13), which will form the basis for the methodological points discussed below. More information can also be found in the IPGS paper on principles for evaluating health risks to reproduction associated with exposure to chemicals (14) as well as in an overview paper by Buschmann (15). 

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