Pathway-related UFs

In the following text, various smdies will be described which attempt to establish a scientific rationale for the selection of the interindividual assessment factor. Based on these studies, it can be concluded that the factor for interindividual variability should preferentially be described probabilistically. However, at present there is no database-derived distribution of the interindividual factor and thus a deterministic default factor of 10, split evenly into a sub-factor of 3.16 for both toxicokinetics and for toxicodynamics, respectively, could be used to account for the inter-individual variability in the human population. Alternatively, a pathway-related UF could be applied in case the pathway(s) of the metabolism of the chemical in humans and the particular enzyme(s) are known. 

FIGURE 5.4 UFs, CSAFs, pathway-related UFs, and general default UFs. (Modified from Renwick, A.G. and Lazarus, N.R., Regul. Toxicol. Pharmacol., 27, 3, 1998.)... 

FIGURE 5.5 Applications of pathway-related UFs for chemical risk assessment and future refinements of toxicokinetic UFs. (Modified from Dome, J.L., Walton, K., and Renwick, A.G., Food Chem. Toxicol, 43, 203, 2005.)... 

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