The reliability of the dimensional measurements of man-made vitreous fibers used for biopersistence assays: A statistical approach

The dimensional measurements of Man-Made Vitreous Fibers (MMVF) are require d in order to conduct in-vivo and in-vitro experiments: for in-vivo experim ents, the geometric mean diameter must be assessed; for in-vitro experiment s, the length-weighted diameter mean and standard deviation is needed in or der to calculate an in-vitro solubility coefficient, Seven fiber samples we re prepared for measurement purpose-using a process described in Hanton et al. (1998). On the basis of these samples, optimal estimation methods and a criteria for stopping the counting of fibers were investigated. It is show n that, unlike the diameter and length distributions, the length-weighted d iameter distribution of these samples can be considered as lognormal. There fore log-normal based estimators have been applied and appear to be more re liable than standard ones. A simple rule for stopping the counting of fiber s has been defined and retrospectively applied to the samples. In several c ases, log-normal based estimators decrease significantly the number of fibe rs which would be otherwise needed in order to meet the stopping condition.