Safety assessment of cosmetic products containing nanomaterials. Current research trends and challenges

Abstract

Nanomaterials (NMs) may exert biologica! effects that differ from their macroscale counterparts. The combination of small particle size, large surface area, and abi lity to generate reactive oxygen species has been demonstrated to be a key factor in induction of celi injury following exposure to certain engineered NMs. Nanostructure can be associated with modification of biologica) properties and toxicological effects of ingredients used in cosmetics. However, the issue is controversial. Contrasting results have been obtained with widely used agents such as Ti0 2 and ZnO. From a regulatory perspecti ve, there are two major uncertai nties that impact on safety assessment strategies for nanotechnology-derived products. The first is as to whether nano-sized particles have to be considered new chemicals, or whether the use of existing materials at the nano-leve! should be considered a "new use" of an existing chemical. Addressing th is question is of crucial importance to define adeguate strategies and establish whether NM-tailored testing methods should be added to conventional toxicity testing protocols to comply with regulatory demand. A second issue is whether the classical toxicity testing methods and strategies that are currently used in the hazard evaluation of macroscale chemicals are adequate when applied to NMs. NMs used in cosmetics can be divided into two groups: labile nanoparticles which disintegrate upon application to skin into their molecular components (e.g. liposomes microemulsions, nanoemulsions) and insoluble nanoparticles such as Ti02, fullerenes and quantum dots. It is currently believed that while conventional risk assessment methodologies may be adequate for labile nanoparticles, specific toxicological and physicochemical parameters must be investigated to establish safety characteristics of insoluble particles. At the present time, the production and commercialisation of manufactured NMs do not trigger additional safety testing. However, the European regulation of chemical substances (REACH), which effectively shifts responsibil ity from authorities to industry to assess safety of chemical substances, is likely to represent a significant challenge in resolving the conflict between progress and protection of cosmetics containing NMs.