Insights on toxicity, safe handling and disposal of silica aerogels and amorphous nanoparticles

Amorphous forms of silica have always raised a lot of interest by the scientific community and are nowadays rapidly growing in commercial applications. These are commercialized as aerogels or as nanoparticles, which can feature many similarities, not only in the synthesis process but also because clusters of nanoparticles are commonly released from aerogels. Nevertheless, the health effects of amorphous silica materials are not fully understood, as occurs with many other nanoforms. Amorphous silica is known to be less toxic than its crystalline form, but toxicity studies, regulatory aspects and handling practices are still scarce. In this work, the knowledge on toxicity of amorphous silica nanostructures and suitable regulations are reviewed. Furthermore, relevant safety practices for handling these materials are discussed and strategies used to recycle and dispose them are summarized.