The article by Hoet et al. provides a comprehensive review of the health risks associated with nanoparticles, ranging from well-established applications like carbon black and fumed silica to more novel uses such as fluorescent quantum dots in biological imaging. The authors highlight the growing investment in nanotechnology and the increasing presence of nanoparticles in consumer and industrial products. While the benefits of nanotechnology are widely publicized, the potential health effects of widespread use are just beginning to be explored. The review discusses the various entry points of nanoparticles into the human body, including the skin, lungs, and intestinal tract, and explores their pathways inside the body. It also analyzes published experimental results on the bioactivity of nanomaterials. Key points include: 1. **Lung Entry and Clearance**: Nanoparticles can enter the lungs through inhalation and are cleared by the mucociliary escalator and macrophage phagocytosis. The clearance rate depends on particle size, surface area, and chemical properties. Ultrafine particles (less than 100 nm) are more likely to cause pulmonary inflammation and fibrosis. 2. **Intestinal Tract**: Particles can translocate from the intestinal lumen via M-cells in Peyer's patches and normal enterocytes. The kinetics of translocation depend on diffusion, accessibility through mucus, and cellular trafficking. Particles can enter the lymphatic system or capillaries, leading to systemic distribution. 3. **Skin Entry**: The skin is a protective barrier, but nano-sized particles are more likely to penetrate deeper layers. Different types of particles are found in deeper skin layers, and materials that can dissolve or break into smaller parts may also penetrate the skin. 4. **Systemic Effects**: The body distribution of nanoparticles is influenced by their surface characteristics. For example, coating nanoparticles with surfactants can alter their distribution in the body. Nanoparticles can affect cardiovascular parameters, such as thrombosis and pulmonary inflammation, and may also induce oxidative stress in the liver. 5. **Cellular Uptake and Oxidative Stress**: Nanoparticles can be taken up by various cells, including endothelial cells, pulmonary epithelium, and macrophages. They can induce oxidative stress and modify cellular antioxidant systems. The review emphasizes the need for further research to understand the full range of health risks associated with nanoparticles and to develop appropriate safety measures.The article by Hoet et al. provides a comprehensive review of the health risks associated with nanoparticles, ranging from well-established applications like carbon black and fumed silica to more novel uses such as fluorescent quantum dots in biological imaging. The authors highlight the growing investment in nanotechnology and the increasing presence of nanoparticles in consumer and industrial products. While the benefits of nanotechnology are widely publicized, the potential health effects of widespread use are just beginning to be explored. The review discusses the various entry points of nanoparticles into the human body, including the skin, lungs, and intestinal tract, and explores their pathways inside the body. It also analyzes published experimental results on the bioactivity of nanomaterials. Key points include: 1. **Lung Entry and Clearance**: Nanoparticles can enter the lungs through inhalation and are cleared by the mucociliary escalator and macrophage phagocytosis. The clearance rate depends on particle size, surface area, and chemical properties. Ultrafine particles (less than 100 nm) are more likely to cause pulmonary inflammation and fibrosis. 2. **Intestinal Tract**: Particles can translocate from the intestinal lumen via M-cells in Peyer's patches and normal enterocytes. The kinetics of translocation depend on diffusion, accessibility through mucus, and cellular trafficking. Particles can enter the lymphatic system or capillaries, leading to systemic distribution. 3. **Skin Entry**: The skin is a protective barrier, but nano-sized particles are more likely to penetrate deeper layers. Different types of particles are found in deeper skin layers, and materials that can dissolve or break into smaller parts may also penetrate the skin. 4. **Systemic Effects**: The body distribution of nanoparticles is influenced by their surface characteristics. For example, coating nanoparticles with surfactants can alter their distribution in the body. Nanoparticles can affect cardiovascular parameters, such as thrombosis and pulmonary inflammation, and may also induce oxidative stress in the liver. 5. **Cellular Uptake and Oxidative Stress**: Nanoparticles can be taken up by various cells, including endothelial cells, pulmonary epithelium, and macrophages. They can induce oxidative stress and modify cellular antioxidant systems. The review emphasizes the need for further research to understand the full range of health risks associated with nanoparticles and to develop appropriate safety measures.