Nanotoxicology is an emerging field that evaluates the safety of engineered nanostructures and nanodevices. It addresses the potential hazards of nanosized particles (NSPs) <100 nm, which can be inhaled, ingested, absorbed through the skin, or injected. These particles, due to their small size and large surface area, can penetrate cells and tissues, reaching organs like the bone marrow, lymph nodes, spleen, and heart. They can also access the central nervous system via neurons. NSPs can cause both positive and negative effects, including inflammation, oxidative stress, and antioxidant activity. The field requires interdisciplinary research involving toxicology, materials science, medicine, and bioinformatics to assess risks. NSPs are categorized as ultrafine particles (UFPs) and include both ambient and engineered materials. They are found in natural and anthropogenic sources, such as combustion processes and industrial activities. NSPs can have different shapes, including spheres, fibers, tubes, and rings. Their toxicity depends on size, surface chemistry, and other factors. Studies show that NSPs can cause significant pulmonary inflammation and extrapulmonary effects. For example, titanium dioxide (TiO₂) particles induce greater inflammatory responses than larger particles of the same chemistry. Similarly, polytetrafluoroethylene (PTFE) fumes cause severe acute lung injury in rats. NSPs can also affect other organs, such as the brain, where they may cause oxidative stress and neurodegenerative effects. Ecotoxicological studies show that NSPs can impact aquatic organisms, with fullerenes affecting daphnia and largemouth bass. NSPs can accumulate in sediments and soil, potentially entering the food chain. Their biocompatibility can be improved through surface coatings, but these may degrade under environmental conditions, affecting toxicity. Reactive oxygen species (ROS) are a key mechanism of NSP toxicity, as they can cause oxidative stress and damage cellular components. NSPs can translocate across cell layers and along neuronal pathways, leading to various health effects. The dose–response relationship is critical in assessing NSP toxicity, as high doses may not reflect realistic in vivo exposures. Studies must consider realistic exposure levels to accurately evaluate risks. NSPs can enter the body through various portals, such as the respiratory tract, skin, and gastrointestinal tract. In the respiratory tract, NSPs are efficiently deposited in the nasopharyngeal region and can translocate to other organs. Clearance mechanisms include mucociliary movement, phagocytosis by alveolar macrophages, and lymphatic drainage. The effectiveness of these mechanisms varies with particle size and surface chemistry. In summary, nanotoxicology is essential for understanding the health and environmental impacts of NSPs. It requires interdisciplinary research to assess risks and ensure the safe use of nanomaterials in various applications.Nanotoxicology is an emerging field that evaluates the safety of engineered nanostructures and nanodevices. It addresses the potential hazards of nanosized particles (NSPs) <100 nm, which can be inhaled, ingested, absorbed through the skin, or injected. These particles, due to their small size and large surface area, can penetrate cells and tissues, reaching organs like the bone marrow, lymph nodes, spleen, and heart. They can also access the central nervous system via neurons. NSPs can cause both positive and negative effects, including inflammation, oxidative stress, and antioxidant activity. The field requires interdisciplinary research involving toxicology, materials science, medicine, and bioinformatics to assess risks. NSPs are categorized as ultrafine particles (UFPs) and include both ambient and engineered materials. They are found in natural and anthropogenic sources, such as combustion processes and industrial activities. NSPs can have different shapes, including spheres, fibers, tubes, and rings. Their toxicity depends on size, surface chemistry, and other factors. Studies show that NSPs can cause significant pulmonary inflammation and extrapulmonary effects. For example, titanium dioxide (TiO₂) particles induce greater inflammatory responses than larger particles of the same chemistry. Similarly, polytetrafluoroethylene (PTFE) fumes cause severe acute lung injury in rats. NSPs can also affect other organs, such as the brain, where they may cause oxidative stress and neurodegenerative effects. Ecotoxicological studies show that NSPs can impact aquatic organisms, with fullerenes affecting daphnia and largemouth bass. NSPs can accumulate in sediments and soil, potentially entering the food chain. Their biocompatibility can be improved through surface coatings, but these may degrade under environmental conditions, affecting toxicity. Reactive oxygen species (ROS) are a key mechanism of NSP toxicity, as they can cause oxidative stress and damage cellular components. NSPs can translocate across cell layers and along neuronal pathways, leading to various health effects. The dose–response relationship is critical in assessing NSP toxicity, as high doses may not reflect realistic in vivo exposures. Studies must consider realistic exposure levels to accurately evaluate risks. NSPs can enter the body through various portals, such as the respiratory tract, skin, and gastrointestinal tract. In the respiratory tract, NSPs are efficiently deposited in the nasopharyngeal region and can translocate to other organs. Clearance mechanisms include mucociliary movement, phagocytosis by alveolar macrophages, and lymphatic drainage. The effectiveness of these mechanisms varies with particle size and surface chemistry. In summary, nanotoxicology is essential for understanding the health and environmental impacts of NSPs. It requires interdisciplinary research to assess risks and ensure the safe use of nanomaterials in various applications.