A comparative study of the National Institute for Occupational Safety and Health 7400 "A" and "B" counting rules using refractory ceramic fibers.
Buchta-TM; Rice-CH; Lockey-JE; Lemasters-GK; Gartside-PS
Appl Occup Environ Hyg 1998 Jan; 13(1):58-61
Industrial hygiene samples were taken at seven facilities where refractory ceramic fibers (RCF) were manufactured and analyzed. NIOSH Method 7400 was used to obtain the 150 samples and a comparison was made between 7400-A and 7400-B counting rules used to estimate exposures. The two methods differ according to the definition of a fiber, but the data demonstrated no significant difference in the relative counting levels obtained. Both counting techniques had similar magnitudes of intracounter variation. A frequency distribution of the data sets generated by the A and B counting rules indicated that the fiber density values were log normally distributed. A paired t-test was performed on the set of 150 transformed counts to determine if there was a statistical difference in the results obtained from the two counting techniques. The result of the paired t-test indicated no difference in fiber density between the two counting rules. The findings indicate that it would be possible to combine the results from these two methods when conducting a long term exposure assessment evaluation of RCF manufacturing operations. The authors suggest, however, that in other settings researchers should conduct a similar evaluation prior to merging samples analyzed by different rules.
NIOSH-Publication; NIOSH-Grant; Analytical-methods; Fibrous-bodies; Air-quality-monitoring; Air-sampling-techniques; Fiber-deposition; Asbestos-fibers; Ceramic-materials; Exposure-assessment; Exposure-limits
Environmental Health University of Cincinnati 3223 Eden Avenue Cincinnati, OH 45267-0056
Applied Occupational and Environmental Hygiene
University of Cincinnati, Cincinnati, Ohio