Titanium dioxide and silver nanoparticles

In the nanoworld, objects are extremely small, and have particularly interesting and different properties to those they have in the macroscopic world. The reactivity of a material depends on the area of contact it has with its environment, and is an increasing function of its specific surface area. The specific surface area of a nanoparticle, defined in square meters per gram, illustrates this gigantic increase in surface area as the diameter decreases. The smaller the nanoparticle size, the greater the proportion of surface atoms. Size, the crystalline or non-crystalline form of the material, charge and solubility are all important parameters. In addition to their reactive properties, nanoparticles have remarkable physicochemical, optical and electrical properties, which may explain the current interest in them. As a result, a great deal of new research has been carried out, followed by industrial developments in a number of fields, some of which have been ignored by consumers. In this article, only the mineral nanoparticles of titanium dioxide (TiO ₂ ) and silver (Ag ⁰ ) used in certain everyday consumer products are considered. Their impact on the skin will be described based on the significant publications available. Vectors of exposure, results of toxicity studies will be discussed, as well as mechanisms of intoxication, when known. Titanium dioxide and silver in nanometric form each present benefits but also risks, and it is currently difficult for the consumer to make a judicious choice, as the risks have not been established with certainty. Given the current state of knowledge, this article will raise more questions than it answers. For simplicity's sake, the term "nanotitanium" will be used instead of titanium dioxide nanoparticles.