Under such experimental conditions, the test material

is aerosolised Obeticholic Acid mw applying high shear stresses and mass median aerodynamic diameters [MMAD] range significantly below 10 μm (ideally 1–3 μm). The respirable fraction then accounts for more than 80 vol%. In conclusion, the toxicologically relevant, respirable fraction is much lower in the products under normal handling and use conditions than under experimental conditions. Surface-treated SAS may be used in perfumes, and hence may be aerosolised during use by consumers (Becker et al., 2009). With typical aerosol particle diameters in the 10–100 μm range, most aerosol particles will not be respirable, but deposited in the nasopharyngeal region. Oral and dermal SAS exposure may arise from the use of personal care products and medicines. Recently, Dekkers et al. (2010) analysed food products

with added silica (E551), and estimated the likely oral intake of “nanosilica” via food. The authors estimated a daily intake of 124 mg “nanosilica”, corresponding to 1.8 mg/kg bw/day for an adult of 70 kg based on products containing E551, although it is stated in the publication C59 mouse itself that “… it is not clear whether the food additive E551 contains nano-sized silica.” The terminology “nanosilica” as used by Dekkers et al. (2010) was later criticized by Bosch et al. (2011). Silica is usually tightly bound into the matrix of end-use articles, and hence significant exposure of the general population through these products is unlikely. The different forms of SAS have been used as test materials

in a number of environmental, ecotoxicological and toxicological studies. Some of these studies were conducted to investigate the toxic potential of SAS while others used SAS as a comparison material in studies on various nanoparticles. Several studies described in the following sections refer to the testing of “nanosilica” versus “bulk silica”, with some studies highlighting the enhanced biological responses for nano-forms versus the findings for larger silica particles. selleck screening library These studies, however, generally refer to the primary particle diameter when classifying some silica products as “nano” rather than a whole-particle dimension that reflects the complex aggregate structures of most silica particles, such as the aggregate diameter. This can lead to the misinterpretation of these study findings as reflecting an effect of particle size while it is well known that silica particles can differ in other toxicologically relevant properties, such as surface area and particle number. Pyrogenic, precipitated and gel forms of SAS, including surface-treated forms, have been the subject of dissolution testing using a simulated biological medium at 37 °C and pH values near 7 (Roelofs and Vogelsberger, 2004). Depending on the material, the solubility was between 2.3 and 2.