Laboratories that measure fibers in workplace samples will be the most likely users of two new ASTM International standards: D 7200, Practice for Sampling and Counting Airborne Fibers, Including Asbestos Fibers, in Mines and Quarries, by Phase Contrast Microscopy and Transmission Electron Microscope; and D 7201, Practice for Sampling and Counting Airborne Fibers, Including Asbestos Fibers, in the Workplace, by Phase Contrast Microscopy (with an Option of Transmission Electron Microscopy). Both standards are under the jurisdiction of Subcommittee D22.04 on Workplace Atmospheres, which is part of ASTM Committee D22 on Air Quality.
“Standards D 7200 and D 7201 were originally a single work item,” says Martin Harper, secretary of Subcommittee D22.04. “The work item was split into two standards because concerns specific to the mining industry could be addressed in a standard specific to that industry (D 7200), while leaving a similar, but not identical, standard to cover other workplaces (D 7201)”.
Both new standards describe methods of analyzing air samples for fibers under the optical phase-contrast microscope. In addition, a procedure is presented for identification and counting through the transmission electron microscope. The difference between these procedures is that PCM is quick and not costly, but cannot differentiate asbestos fibers from any others. TEM Is more expensive and complicated, but it can differentiate asbestos from fibers of other common materials (e.g. glass or organic fibers). All particles that meet the geometric rules defining a fiber are included in a PCM count using Practice D 7201. Practice D7200 proposes a method for discriminating amphibole cleavage fragments, common in many mines and quarries from asbestiform amphibole fibers.
Harper says that all interested parties are invited to participate in future revisions of the standard. The subcommittee is hoping to launch a round-robin study for Practice D 7200 to provide the required database on interlaboratory comparison.
ASTM International standards are available for purchase from Customer Service (phone: 610/832-9585; email@example.com or at www.astm.org). Committee D22 meets Oct. 22-25, during the October Committee Week in Atlanta, Ga. For information, contact George Luciw, manager, Technical Committee Operations, ASTM International (phone: 610/832-9710; firstname.lastname@example.org).