Nanotechnology plays a major role in modern science and industry through the development of novel materials and advanced consumer products with unique physicochemical properties. Nanoparticles are increasingly utilized in medicine, electronics, agriculture, cosmetics, and industrial applications due to their enhanced functionality and efficiency. However, the widespread use of nanoparticles has also raised important concerns regarding their potential effects on human health and the environment. Because of their extremely small size, large surface area, and high reactivity, nanoparticles can interact with biological systems in ways that may lead to toxic effects in humans, animals, and ecosystems. This review summarizes the major characteristics of nanoparticles that contribute to their toxicity and discusses the primary routes of human exposure, including inhalation, ingestion, and dermal contact. In addition, the environmental impacts of nanoparticles on soil, water systems, plants, and microorganisms are highlighted. Since information regarding long-term exposure and safety remains limited, further toxicological investigations are necessary to better understand the short and long-term consequences of nanoparticle exposure. Finally, recent progress, existing limitations, and future challenges in nanoparticle safety research are briefly outlined.