National Academy of Sciences | 150 Year Anniversary

Questions? Call 800-624-6242

| Items in cart [0]

The National Academies Press

PAPERBACK
price:$162.25
add to cart

Rights & Permissions

topleft topright

Science and Judgment in Risk Assessment (1994)
Board on Environmental Studies and Toxicology (BEST)

Citation Manager

. "Appendix H-1: Some Definitional Concerns About Variability." Science and Judgment in Risk Assessment. Washington, DC: The National Academies Press, 1994.

Please select a format:

BibTeX EndNote RefMan


Page
503
bottomleft bottomright

The following HTML text is provided to enhance online readability. Many aspects of typography translate only awkwardly to HTML. Please use the page image as the authoritative form to ensure accuracy.


Page 503

Appendix
H-1
Some Definitional Concerns About Variability

Each of the three major types of variability (temporal, spatial, and interindividual) can be characterized in three ways, as follows (these examples are all related to human variability in susceptibility, although other examples are possible):

Variability is (or can be modeled sufficiently precisely as though it were) is) either discrete or continuous. For example, albinos are many times more sensitive to sunlight than other members of the population, so a (dichotomous) discrete assumption might well be appropriate here. In contrast, because body weights vary continuously, the cancer risk per unit dose of a substance cannot be modeled dichotomously without the loss of much of information.

Variability is identifiable or unidentifiable. Albinism is a good example of identifiable variability, whereas the extent of a person's ability to detoxify a particular active metabolic intermediate might not be discernible without invasive testing, and hence is unidentifiable for most of the population.

Identifiable variability is dependent on or independent of additional variable characteristics that society deems salient. For example, some factors that cause genetic predisposition to the carcinogenic effect of chemicals are correlated with race, sex, or age. If society deems that those who are predisposed already deserve special attention because of the other factors, the importance of the variability is heightened. But some kinds of identifiable variability, such as body weight and phenylketonuria, are more "value-neutral" or are uncorrelated with any relevant characteristic.

Page
503
Front Matter (R1-R16)
Executive Summary (1-15)
1 Introduction (16-22)
Part I Current Approaches to Risk Assessment: 2 Risk Assessment and its Social and Regulatory Contexts (23-42)
3 Exposure Assessment (43-55)
4 Assessment of Toxicity (56-67)
5 Risk Characterization (68-78)
Part II Strategies for Improving Risk Assessment: 6 Default Options (79-105)
7 Models, Methods, and Data (106-143)
8 Data Needs (144-159)
9 Uncertainty (160-187)
10 Variability (188-223)
11 Aggregation (224-242)
Part III Implementation of Findings: 12 Implementation (243-268)
References (269-286)
Appendix A: Risk Assessment Methodologies: EPA (287-350)
Appendix B: EPA Memorandum from Henry Habicht (351-374)
Appendix C: Calculation and Modeling of Exposure (375-382)
Appendix D: Working Paper for Considering Draft Revisions to the U.S. EPA Guidelines for Cancer Risk Assessment (383-448)
Appendix E: Use of Pharmacokinetics to Extrapolate from Animal Data to Humans (449-452)
Appendix F: Uncertainty Analysis of Health Risk Estimates (453-478)
Appendix G: Improvement in Human Health Risk Assessment Utilizing Site- and Chemical-Specific Information: A Case Study (479-502)
Appendix H-1: Some Definitional Concerns About Variability (503-504)
Appendix H-2: Individual Susceptibility Factors (505-514)
Appendix I: Aggregation (515-536)
Appendix J: A Tiered Modeling Approach for Assessing the Risks Due to Sources of Hazardous Air Pollutants (537-582)
Appendix K: Science Advisory Board Memorandum on the Integrated Risk Information System and EPA Response (583-590)
Appendix L: Development of Data Used in Risk Assessment (591-598)
Appendix M: Charge to the Committee (599-600)
Appendix N-1: The Case for (601-628)
Appendix N-2: Making Full Use of Scientific Information in Risk Assessment (629-640)
Index (641-652)

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 503
Page 503 Appendix H-1 Some Definitional Concerns About Variability Each of the three major types of variability (temporal, spatial, and interindividual) can be characterized in three ways, as follows (these examples are all related to human variability in susceptibility, although other examples are possible): • Variability is (or can be modeled sufficiently precisely as though it were) is) either discrete or continuous. For example, albinos are many times more sensitive to sunlight than other members of the population, so a (dichotomous) discrete assumption might well be appropriate here. In contrast, because body weights vary continuously, the cancer risk per unit dose of a substance cannot be modeled dichotomously without the loss of much of information. • Variability is identifiable or unidentifiable. Albinism is a good example of identifiable variability, whereas the extent of a person's ability to detoxify a particular active metabolic intermediate might not be discernible without invasive testing, and hence is unidentifiable for most of the population. • Identifiable variability is dependent on or independent of additional variable characteristics that society deems salient. For example, some factors that cause genetic predisposition to the carcinogenic effect of chemicals are correlated with race, sex, or age. If society deems that those who are predisposed already deserve special attention because of the other factors, the importance of the variability is heightened. But some kinds of identifiable variability, such as body weight and phenylketonuria, are more "value-neutral" or are uncorrelated with any relevant characteristic.

OCR for page 504

Representative terms from entire chapter:

identifiable variability