A Fiber Characterization of the Natural Zeolite, Mordenite: A Potential Inhalation Health Hazard
Interest in mordenite as an inhalation hazard arose when it was discovered that the mineral exists in the subsurface of Yucca Mountain, NV, the site of a federally proposed nuclear waste repository. During preliminary geologic investigations at Yucca Mountain, workers performing air coring (dry-drilling) operations were potentially exposed to aerosols of mordenite. Mordenite is also increasingly used in industrial applications, such as cation exchange, molecular absorbency, and reversible dehydration. Concern that the fibrous nature of mordenite may present an inhalation hazard is supported by the ''Stanton Hypothesis," which states that the carcinogenicity of any fiber type depends upon dimension and durability rather than physicochemical properties. To date, little scientific literature is available on the inhalation health hazards of mordenite. This study initiates research in this area. Mordenite specimens collected from different geologic localities were analyzed macroscopically and microscopically. Mineral verification was performed using energy dispersive x-ray and x-ray diffraction analysis. Fibrous aerosols were generated to simulate aerosols created during air coring operations. Anderson cascade impactors were used to obtain aerosol mass median aerodynamic diameters. Electron microscopy of nucleopore filters allowed for individual aerosol fibers to be morphologically sized and applied to the Stanton Hypothesis for mesothelioma induction. Physical fiber dimensions were used to calculate aerodynamic diameters and to estimate pulmonary deposition. Results obtained from this study indicate that under similar conditions of aerosolization, using similar mordenite materials, inhalation of mordenite fibers could produce substantial deep-lung deposition.
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