Abstract.Experimental research has shown that after intragastric administration of a water suspension of nanodispersed silicon dioxide particles synthesized by the method of templating the tested product falls in hazard class 3 by criteria LD50. A number of morphological changes were detected in the least researched dose of 500 mg/kg, in particular, gross changes in the blood circulatory system in the form of vascular distention, kidney, liver, and thymus. Other changes included lymphoid and macrophage proliferation and degenerative changes in the liver, kidney, splenic cords and lungs. After administration of a microdispersed analogue by the same method, no deaths of experimental animals were recorded (hazard class 4). A number of morphological changes were detected in dose 500 mg/kg including moderate vascular changes in liver, lymphoid proliferation, and lymphoid infiltration in the tissues of the esophagus, liver, kidney, large intestine, and gastric tissues.

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The object of the study was amorphous silica dioxide (SiO 2 ), which is widely used as a food additive (E551), a subsidiary component in pharmaceutical preparations

The results of toxicity studies of nano-sized colloidal silver (NCC), the most widely used in medicine, food and life, are given. When evaluating safe doses of silver NP (using commercially available NCC solution stabilized with polyvinylpyrrolidone (PVP), with the size of silver NP at the range of 5-80 nm) when orally administered to male mice, BALB/c mice at doses of 0.1; 1.0 and 10 mg/kg of body weight per silver different effects from the motor and orienting-exploratory activity were revealed, for the part of them the dependence on the dose of the NCC was typical. The following peculiarities were found: reduction in motor activity to reduce the frequency of activities requiring physical effort, reduction of the execution time of these actions; increasing anxiety in terms of frequency and duration of attacks of orienting-investigative activity and animals washing. Morphological examination revealed a series of tissue changes of internal organs (especially liver and spleen, to a lesser extent-kidney, heart and colon) with increase of the spectrum and severity of structural changes with increasing doses of the NCC. From the combination of the data the conclusion was made that maximal ineffective dose (NOAEL) of this nanomaterial at subacute oral administration is no more than 0.1 mg/kg body weight.

Abstract. In subchronic experiment on Wistar's white male rats the negative effects have been studied and the comparative assessment of toxicity of an aqueous suspension of nano-and microfine silicon dioxide has been carried out. It was found that by intragastric administration for 90 days of the dose of 14.6 mg/kg, corresponding to the predicted threshold dose (LOAEL), the aqueous suspension of nanosized silicon dioxide causes immune irritating, cytolytic and inflammatory effects, verified by the deviation of hematologic parameters and morphological changes in tissues bodies / or target systems (liver, stomach, jejunum and colon, immune system). Micro-sized silica causes predominantly an inflammatory effect in the mucosa of stomach, jejunum and colon.