Risk Assessment
Options for Development of Parametric Probability Distributions for Exposure Factors
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Users of the Exposure Factors Handbook (EPA/600/P-95/002Fa-Fc) expressed the need to fit distributions to the data in the handbook to assist them when applying probabilistic methods to exposure assessments. The purpose of this document is to fulfill this need. The document summarizes a system of procedures to fit distributions to selected data from the Exposure Factors Handbook. Three factors - tap water intake, population mobility, and inhalation rules - are used at test cases in the document. The system used includes components for models, estimation, assessment of fit, and uncertainty. Eight models were tested including: generalized F, generalized gamma, Burr, gamma, lognormal, Weibull, log-logistic, and exponential. The document provides recommendations on the models that provide the best fit.
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- Appendix A: Glossary (PDF) (NA pp, 42 KB, about PDF)
- Chapter 1: Introduction (PDF) (NA pp, 884 KB, about PDF)
- Table of Contents (PDF) (NA pp, 51 KB, about PDF)
- Chapter 7: References (PDF) (NA pp, 23 KB, about PDF)
- Appendix D: the Generalized (Power Transformed)F Family of Nonnegative Probability Distributions (PDF) (NA pp, 294 KB, about PDF)
- Chapter 4: Analysis of Population Mobility Data (PDF) (NA pp, 27 KB, about PDF)
- Appendix C: Fitting Quantiles By Combining Nonlinear and Linear Regression (PDF) (NA pp, 25 KB, about PDF)
- Chapter 3: Analysis of Tap Water Data (PDF) (NA pp, 238 KB, about PDF)
- Chapter 5: Application to Inhalation Rates (PDF) (NA pp, 29 KB, about PDF)
- Chapter 2: A System for Fitting Distributions to Exposure Factor Data (PDF) (NA pp, 56 KB, about PDF)
- Appendix B: Fitting Models to Percentile Data (PDF) (NA pp, 26 KB, about PDF)
- Chapter 6: Discussion and Recommendations (PDF) (NA pp, 30 KB, about PDF)