Toxicity of single-walled carbon nanotube: How we were wrong?

The first issue that we address and justify in this paper is the pejorative and provocative tone of the title; the contradictory data on the toxic effects of single-walled carbon nanotubes (SWCNT) make us believe that it is appropriate and necessary. Two of the first studies in toxicity of carbon nanotube were by Chiu Wing Lam et al.[1] and David Warheit et al.[2], who reported that carbon nanotube can damage lung tissue in mice. Their works were subsequently introduced in Science in 2003. Since then, toxicity of carbon nanotube has become a fresh research topic and a number of papers have been dedicated to this field. Fig. 1 plots the citations versus calendar year for the past five years to these two papers. A linear increasing number of publications citing Chiu Wing Lam et al. and David Warheit et al. have appeared. In 2001, Huczko A. et al. [3] and [4] first discussed the fact that fullerene soot with a high content of single-walled carbon nanotubes did not show any signs of health hazard related to skin irritation and allergic risks and did not induce any abnormalities of pulmonary function or measurable inflammation in guinea pigs. Unfortunately, his publications have essentially been ignored (Sum of citations, Fig. 1). Does carbon nanotube really cause toxic effects? We attempt here to briefly demonstrate why we should rationally understand this conception by taking HiPco® single-walled carbon nanotube (Carbon Nanotechnologies, Inc. Houston, TX) as an example. Though biocompatible behavior of functionalized HiPco® carbon nanotube has been researched by a number of authors, we intend to exclude them from the scope of this work.