Abstract
For the past 3 years the Bureau of Mines, Avondale Research Center, has been doing extensive particle size measurements on respirable coal dust collected at surface and underground mines in the eastern United States. Respirable dust is the portion of airborne dust that penetrates the deepest portion of the lungs and is generally considered to be particles less than 10 μm in size. To monitor dust exposure, approximately 40,000 respirable dust samples are collected by inspectors annually. The quartz in these samples is determined by either infrared spectrophotometry or x-ray diffraction. Both methods require quartz standards. The response of both methods, however, as shown by Tuddenham, Huggins, and Klug is particle size dependent. Joint studies by the Bureau of Mines and Mine Safety and Health Administration show that inaccuracy in quantitative quartz values may be as much as 30% when the particle size of the quartz standard does not match that of the quartz in coal dust.
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