Volume 3, Issue 6 (November 1975)
Detection of Chrysotile Asbestos in Airborne Dust from Thermosetting Resin Grinding
Airborne dust samples generated during grinding thermosetting resin plaques containing 0.8 to 18% chrysotile and reference samples were examined optically and on the electron microprobe up to magnifications of ×900.
Chrysotile in dust samples was analyzed by new methods using iodine in solution or as a vapor for selectively staining chrysotile and increasing its visibility and by the NIOSH phase contrast method. No free fibers of chrysotile were detected in dust collected from 0.8% chrysotile-polyester plaques. Only a low-level concentration was found in dust from 4–18% chrysotile-polyester plaques. The difference in texture of chrysotile and cellulose ester membrane (CEM) filters was emphasized by vacuum deposition of aluminum and carbon.
The importance of care in handling chrysotile-bearing CEM filters and the improvement in retention with carbon coating are described.
Electron microprobe methods are presented that distinguish between chrysotile completely encapsulated in resin and chrysotile with a free surface. The airborne chrysotile in the grinding dust was usually nonfibrous, encapsulated in resin, and closely associated with other materials. In the samples analyzed, the number of chrysotile fibers with a free surface varied from zero to two per thousand dust particles.