"However, as the potential uses of SiNPs have increased, research looking into the biological effects and toxicity has not kept up to speed. Studies have shown that inhalation of microcrystalline silica may be linked with the pulmonary disease silicosis in humans. Chronic inhalation studies in rats have been associated with pulmonary fibrosis and cancer, and exposure to microscale amporphous silica has been linked to inflammation, granuloma formation and emphysema. A complete understanding of the size, shape, and composition-dependent interactions of SiNPs with biological systems is lacking, largely due to suitable analytical methods.
The Livermore PK analysis showed that SiNPs were rapidly cleared from the circulatory system (the "central compartment" in PK models) and were distributed to various body tissues, where they persisted over the eight-week time course of the study, raising questions about the potential for bioaccumulation and associated long-term effects."