Intracounter, Intralaboratory, and Interlaboratory Variation of Asbestos Counting with Phase-Contrast Microscopy

Abstract

The findings from this study illustrate how a recently developed industrial hygiene laboratory can be evaluated in its performance in assessing the precision of asbestos fiber counting data. Further, the results demonstrate how one such laboratory, the Seoul National University – School of Public Health (SNU – SPH) Industrial Hygiene (IH) laboratory, has done in comparison to other laboratories. Interlaboratory variation of asbestos fiber counting in a group of Korean and international laboratories participating in the Asbestos Fiber Regular Informal Counting Arrangement (AFRICA) Scheme and the performance of the SNU-SPH IH laboratory in the American Industrial Hygiene Association–Proficiency Analytical Testing (AIHA–PAT) Program were evaluated. Intracounter variation was significant for two out of three counters studied. The overall intracounter variations for the three counters ranged from 0.23 to 0.31, being the lowest for the most experienced person. Large variation was determined for samples at low fiber density while variation decreased at higher fiber density. Intralaboratory variation was significant when all three counters were involved, while no significant difference was indicated when the counter with only three months of experience was excluded. The interlaboratory variation among laboratories of developing and newly industrialized countries was significant; the interlaboratory variations ranged from 0.27 to 0.34 at fiber density over 100 f/mm² in the AFRICA Scheme. The performance of the SNU–SPH EH laboratory has been rated as “proficient” by the AIHA–PAT Program.