Uncertainty Factor

confidence interval used to assess the probable accuracy of an estimate; value used in toxicological assessment to apply data from experimental animals to man or from selected individuals to the general population

One of several factors used in calculating the reference dose from experimental data. UFs are intended to account for (1) the variation in sensitivity among humans; (2) the uncertainty in extrapolating animal data to humans; (3) the uncertainty in extrapolating data obtained in a study that covers less than the full life of the exposed animal or human; and (4) the uncertainty in using LOAEL data rather than NOAEL data.