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CEFIC-LRI N1 Project: Inhalation toxicity of a synthetic amorphous silica (SAS) in rats

: Creutzenberg, Otto H.; Pohlmann, Gerhard; Hansen, Tanja; Schuchardt, Sven; Ernst, Heinrich; Tillmann, Thomas; Schaudien, Dirk

The Toxicologist 53 (2014), No. , pp.158, PS 600
ISSN: 0731-9193
Society of Toxicology (Annual Meeting) <53, 2014, Phoenix/Ariz.>
Fraunhofer ITEM ()

The test item was a synthetic amorphous silica (SAS) coded NM-200 and available at the EU JRC nanomaterials repository. It is a nanostructured, precipitated SAS used in the food sector. A subacute 14-day and a subchronic 90-day inhalation toxicity test were conducted (OECD TG 412 and 413) in male Wistar rats both including an expanded endpoint pattern (i.e.toxicokinetics, genotoxicity, TEM analysis) compared to the requirements of OECD TG. In the 14-day test rats were exposed to aerosol concentrations of 1, 5 and 25 mg/m3. No systemic but local acute effects in nose/lungs were detected, i.) mucous (goblet) cell hyperplasia and epithelial eosinophilic droplets/inflammatory cell infiltration in the nasal cavity; ii.) alveolar/ interstitial macrophage/granulocyte infiltration in the lungs of the high dose group. Statistically significant increases of polymorphonuclear neutrophils (PMN) in bronchoalveolar lavage fluid (BALF) were detected in the mid and high dose groups 1 day after exposure. These findings showed a rapid reversibility. The LOAEL was 5 mg/m3 and the NOAEL 1 mg/m3. In the 90-day test, conducted at aerosol concentrations of 1, 2.5 and 5 mg/m3 the LOAEL was 1 mg/m3, thus an experimental NOAEL could not be derived from the study. The EPA benchmark model resulted in a BMCL of 0.6 mg/m3 based on the PMN number in BALF.
Toxicokinetics followed over 90 days after end of exposure revealed a half-time of approx. 30 days (chemical Si analysis) thus indicating a high solubility. TEM analysis detected SiO2 particles located in intraalveolar macrophages. In remote organs, however, such particles were not detectable.
Overall, NM-200 showed acute toxicity in nose and lungs after inhalation. Due to an effective clearance and solubility a full recovery of effects was found. A translocation of NM-200 particles was not observed.