As adverse effects of environmental nanoparticles, like ultrafine particles, have been reported, consumers worry about potential risks when using products containing NMs. The review focuses on metal and metal oxide NMs as common additives in tooth paste and in food industry and exposure by the oral route.
Testing of NMs for oral exposure is very complex because differences in the diet, in mucus secretion and composition, in pH, in gastrointestinal transit time and in gastrointestinal flora influence NM uptake.
Acellular (mucus, saliva) and epithelial layer of the orogastrointestinal barrier are described.
Expected exposure doses, interaction of the NMs with mucus and permeation through the epithelium as well as in vivo data are mentioned.
The role of in vitro models for the study of parameters relevant for ingested NMs is discussed.