Analysis on Numbers of Observed Field and Counting Error in PCM Method by Using Monte-Carlo Simulation

Abstract

Monte-Carlo simulation was performed to estimate the influence of numbers of observed fields in relation to counting errors of the phase contrast microscopy (PCM) method for measurements of asbestos fibers concentrations in air. By repeatedly observing 2,000 fields of virtual samples having several concentrations, relative standard deviations (RSD) as to counting fibers were estimated. Without depending on concentration levels, RSD was significantly decreased with an increase of observed numbers of the fields (up to approximately 300 fields). Even if 20% of RSD was acceptable and fibers were uniformly deposited on a virtual sample, it was necessary to observe around 300 fields in order to achieve a sufficient quantification limit to measure an environment level. It was also suggested that the PCM method should be automated to observe such many fields.