This study was conducted to evaluate the accuracy and the precision of asbestos counting data produced by the Division of Industrial Health, School of Public Health, Seoul National Universitys (SNU). The study was performed from July 18 to October 4, 1991, and the results are summarized as follows.
1. Intracounter Relative Standard Deviations (Sr) in the category of 5-50.5 fibers as total fibers counted ranged from 0.27 to 0.37, which were greater than 0.10-0.17 which were reported by the NIOSH. The reasons are supposed to be as follows.
First, inexperience of counters in asbestos fiber counting was considered to be a main reason. Second, poor quality of :samples due to sampling and mounting error increased variation of counting. Third, fiber density of many samples were less than 100 fibers/㎟.
But Intracounter Relative Standard Deviations (Sr) in samples with $gt;50.5 fibers ranged from 0.16 to 0.20, approaching the value of NIOSH.
2. Intralaboratory Relative Standard Deviations (Sr) in categories of 5-20.5, $gt;20.5-50.5 and $gt;50.5 fibers were 0.54, 0.37 and 0.26, respectively. Intralaboratory Sr in samples with fiber density greater than 100 fibers/㎟ was 0.26. This was similar to the values reported by other foreign experienced laboratories.
3. Comparing results of three counters, Counter C, a beginner, overestimated asbestos fiber concentrations.
4. Since our SNU laboratory has participated in two quality control programs, IOM-A.F.R.I.C.A., U.K. and NIOSH PAT Program, U.S.A., this laboratory has been evaluated as $quot;Rating 1$quot; and $quot;Proficient$quot; laboratory, by IOM and NIOSH, respectively.
|