"As asbestos fibers and other fine particles have been studied extensively to correlate physical and chemical properties with their potential for negative human health impact on inhalation, there remains no concise definitions for the individual particle types nor collective considerations of combined variabilities. Extensive studies relating negative health to asbestos morphology, chemistry, surface effects, and biodurability form general qualitative bins of what is more likely causative or less, but do not provide enough information to quantitatively dismiss particles with parameters outside any given range. Further, natural mineral species and accessory mineralization makes standardization of universally applicable reference materials nearly unobtainable. With modern advent of engineered nanoparticles, we are adding even more unknowns to the universe of the microscopic size fraction and its potential for human disease, and our paradigm is challenged."

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