Characterization of three types of chrysotile asbestos after aerosolization

Jeffrey Mine and Coalinga Mine chrysotile, two asbestos samples prepared for experimental research by the National Institute of Environmental Health Sciences, and the UICC B chrysotile reference sample have been characterized in the aerosolized state using gravimetric measurements, light microscopy, scanning electron microscopy, and x-ray energy spectrometry. These methods revealed (1) a greater "respirable" mass fraction in the Jeffrey and UICC B preparations compared to the Coalinga sample, (2) for fibers greater than 5 μm in length and less than 3 μm in diameter, Jeffrey Mine chrysotile contained a significantly greater fraction of fibers longer than 40 μm in length compared to the UICC B or Coalinga Mine chrysotiles, and (3) Jeffrey and UICC B chrysotile contained no fibers or fiber clusters which exceeded 2 μm in diameter while Coalinga chrysotile contained numerous fibers and fiber clusters which were greater than 2 μm in diameter. The characterization of these chrysotile preparations in the aerosolized state, in particular the Coalinga Mine chrysotile, demonstrated different fiber length and fiber width distributions when compared with previous characterizations of samples that had been dispersed in a liquid medium by ultrasonification. These observations emphasize the importance of determining the size distribution of fibers in the aerosolized state for inhalation studies and the size distribution of fibers in a liquid suspension for oral ingestion, instillation, or injection studies. Because of differences in length-width distributions, each of the studied chrysotile preparations would be expected to have different patterns of deposition in the alveolar regions of the lung after an inhalation exposure.