Page:NIOSH Manual of Analytical Methods - Chapter R.pdf/16

 '''TABLE 7. XRD METHOD EVALUATION: AIR CONCENTRATIONS (µg/cm3) CORRESPONDING TO ACTUAL FILTER LOADINGS (µg/filter). [76]'''

* Eight-hour sampled masses are combined with results of NIOSH, BOM [1983].

'''TABLE 8. IR METHOD EVALUATION: AIR CONCENTRATIONS (µg/cm$3$) CORRESPONDING TO ACTUAL FILTER LOADINGS (µg/filter). [76]'''

* Eight-hour sampled masses are combined with results of NIOSH, BOM [1983].

7. SUMMARY

Silica is commonly found in the earth's crust and occurs in both crystalline and non-crystalline forms. Exposure to crystalline silica causes silicosis, is associated with pulmonary tuberculosis, lung cancer, scleroderma and may be related to autoimmune disorders and chronic renal disease.

Current methods for sampling airborne crystalline silica use a cyclone/cassette to collect the respirable fraction of the aerosol. There are several cyclones available, each with specific particle collection characteristics. To support interlaboratory precision, a single sampler which meets the ISO/CEN/ACGIH respirable sampling convention should be used.

Accurate and sensitive measurement of crystalline silica is complex. A high degree of attention is required throughout the analysis. The sample cassette should be checked for any adherence of particles to the walls of the cassette. Mineral interferences may be removed prior to analysis or may be dealt with via analytical data and a thorough knowledge of the characteristic analytical peaks. For methods involving redeposition of the sample, the entire analysis is dependent upon the uniform deposition of the particles onto the analytical filter for laboratory analysis. Calibration of the technique is crucial; the most important factors being the use of prescribed SRMs, the preparation of standards at appropriate concentrations and the use of QC samples to monitor calibration. An internal quality assurance program which incorporates strict adherence to standardized procedures is essential for measurement accuracy and precision. 3/15/03