Toxic effects of nanoparticles - differences and similarities with fine particles

There is increasing recognition that nanoparticles may pose a risk to human health. Toxicology studies have indicated that specific properties of nanoparticles drive their toxicity. These properties include surface area and chemistry, size and shape of particles, as well as charge and number, but to a lesser extent, mass. Nanoparticles can influence human health by occupational exposure and by environmental contacts. Uptake of nanoparticles may occur by inhalation, transdermal means and by ingestion. After inhalation, oral administration or parenteral administration, nanoparticles reach the lungs, gastrointestinal tract and brain. It is important to understand the similar and dissimilar features of nanoparticles and fine particles regarding impact on health. The general picture that emerges from experimental animal studies is that, on a mass dose basis, pulmonary toxicity is enhanced when particle size is reduced from the micrometre to the nanometre range. The increase in toxicity appears to be related to the increase in particle surface area. However, different existing materials in the nanometre size exhibit different degrees of toxicity on the respiratory tract. It is not possible to reach generic conclusions about toxicity based on consideration of size alone; the potential toxicity of each individual nanoparticulate material needs to be considered on a case-by-case basis. There is a clear lack of information on the potential health effects of nanoparticles produced for nanotechnologies. These uncertainties arise because of gaps in knowledge about the factors that are essential for predicting health risks — factors such as routes of exposure, translocation of materials once they enter the body, and interaction of the materials with the body's biological systems.