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Combining Uncertainty Factors in Deriving Human Exposure Levels of Noncarcinogenic Toxicants
Author(s) -
KODELL RALPH L.,
GAYLOR DAVID W.
Publication year - 1999
Publication title -
annals of the new york academy of sciences
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.712
H-Index - 248
eISSN - 1749-6632
pISSN - 0077-8923
DOI - 10.1111/j.1749-6632.1999.tb08085.x
Subject(s) - percentile , extrapolation , sensitivity (control systems) , econometrics , uncertainty analysis , product (mathematics) , benchmark (surveying) , statistics , mathematics , engineering , geometry , geodesy , electronic engineering , geography
A bstract : Acceptable levels of human exposure to noncarcinogenic toxicants in environmental and occupational settings generally are derived by reducing experimental no‐observed‐adverse‐effect levels (NOAELs) or benchmark doses (BDs) by a product of uncertainty factors (Barnes and Dourson, Ref. 1). These factors are presumed to ensure safety by accounting for uncertainty in dose extrapolation, uncertainty in duration extrapolation, differential sensitivity between humans and animals, and differential sensitivity among humans. The common default value for each uncertainty factor is 10. This paper shows how estimates of means and standard deviations of the approximately log‐normal distributions of individual uncertainty factors can be used to estimate percentiles of the distribution of the product of uncertainty factors. An appropriately selected upper percentile, for example, 95th or 99th, of the distribution of the product can be used as a combined uncertainty factor to replace the conventional product of default factors.