Lead Human Exposure and Health Risk Assessments for Selected ...

1 2 DESIGN OF EXPOSURE AND RISK ASSESSMENTS
2 The risk assessment design relies on the use of case studies. The types of case studies
3 included, as well as the analytical aspects of the assessment of each, reflect consideration of the
4 evidence presented in the CD, air quality analyses, and findings of the pilot assessment (Section
5 1.3), as well as comments received from CASAC (Section 1.4) and the public.
6 Drawing primarily from the CD, Section 2.1 provides background for the risk
7 assessment, with regard to key elements of Pb exposure and effects. The assessment scenarios
8 evaluated in the assessment are described in Section 2.2. Background information on the three
9 case studies is described in Section 2.3. Section 2.4 describes the analytical approach, with
10 attention to key analytical steps, and discussion of temporal and spatial aspects of the
11 assessment, as well as the categorization of policy-relevant exposure pathways, and the
12 uncertainty characterization.
13 2.1 BACKGROUND INFORMATION ON LEAD EXPOSURE AND RISK
14 As recognized in Section 1.1, there are a variety of complexities associated with the
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assessment of air-related Pb exposure and risk. In this risk assessment, we have attempted to
16 focus effort on those aspects that are most important and feasible to address within our scope and
17 given the constraints of time, pertinent data, models, etc. With regard to some aspects,
18 simplifying assumptions have been implemented. The following subsections describe elements
19 of Pb exposure and effects pertinent to evaluating public health risks associated with Pb from
ambient air, and specify those that are explicitly addressed in this quantitative risk assessment.
21 This is summarized in Figure 2-1, with boxes outlined in bold indicating items included in the
22 quantitative risk assessment and sources and pathways for which ambient air has played a role
23 identified in bold text.
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July 2007 2-1 Draft – Do Not Quote or Cite