ABSTRACT
BARBARA ROTHEN-RUTISHAUSER, FABIAN BLANK, CHRISTIAN MU¨HLFELD*, and PETER GEHR University of Bern, Bern, Switzerland
I. Introduction
During the past years, there has been a substantial increase in the debate on the potential harmful effects of nanomaterials (1-4), defined as materials with a diameter below 100 nm, and nanotubes, which have two dimensions below 100 nm while the third dimension can be much larger (5). Among these nanomaterials, specific concern is expressed about adverse health effects of nanoparticles (NP), since recent studies indicate a specific toxicological effect of inhaled combustion-derived ultrafine particles (UFP) (6-11). Although there are obvious differences between UFP, which are polydispersed and have a chemically complex nature, and NP, which are in contrast monodispersed with precise chemically engineered characteristics, the same toxicological principles have been assumed (3). An important basis for the current concerns about the possible adverse health effects of NP and nanotubes has been provided by research in the field of inhalation toxicology (12). Rodent inhalation studies provided evidence that NP induce considerably stronger pulmonary toxicity when compared at equal mass dose with larger particles. For instance, inhaled or intratracheally instilled poorly soluble particles of low toxicity such as carbon black and titanium dioxide induce pulmonary inflammation in proportion to their surface area (3,13,14). These findings indicate that a large surface area deposited in the lung may be sufficient to initiate inflammation. The in vivo studies are supported by in vitro studies where UFP show stronger inflammatory or toxic responses than larger-sized particles of the same chemical composition (15).
