Cytotoxicity Assessment of Some Carbon Nanotubes and Related Carbon Nanoparticle Aggregates and the Implications for Anthropogenic Carbon Nanotube Aggregates in the Environment

Abstract

Nanotechnology and nanomaterials have become the new frontier world-wide over the past few years and prospects for the production and novel uses of large quantities of carbon nanotubes in particular are becoming an increasing reality. Correspondingly, the potential health risks for these and other nanoparticulate materials have been of considerable concern. Toxicological studies, while sparse, have been concerned with virtually uncharacterized, single wall carbon nanotubes, and the conclusions have been conflicting and uncertain. In this research we performed viability assays on a murine lung macrophage cell line to assess the comparative cytotoxicity of commercial, single wall carbon nanotubes (ropes) and two different multiwall carbon nanotube samples; utilizing chrysotile asbestos nanotubes and black carbon nanoaggregates as toxicity standards. These nanotube materials were completely characterized by transmission electron microscopy and observed to be aggregates ranging from 1 to 2 μm in mean diameter, with closed ends. The cytotoxicity data indicated a strong concentration relationship and toxicity for all the carbon nanotube materials relative to the asbestos nanotubes and black carbon. A commercial multiwall carbon nanotube aggregate exhibiting this significant cell response was observed to be identical in structure to multiwall carbon nanotube aggregates demonstrated to be ubiquitous in the environment, and especially in indoor environments, where natural gas or propane cooking stoves exist. Correspondingly, preliminary epidemiological data, although sparse, indicate a correlation between asthma incidence or classification, and exposure to gas stoves. These results suggest a number of novel epidemiological and etiological avenues for asthma triggers and related respiratory or other environmental health effects, especially since indoor number concentrations for multiwall carbon nanotube aggregates is at least 10 times the outdoor concentration, and virtually all gas combustion processes are variously effective sources. These results also raise concerns for manufactured carbon nanotube aggregates, and related fullerene nanoparticles.

Effects of suspended multi-walled carbon nanotubes on daphnid growth and reproduction

“…CNTs have been found in ice core samples , deep rock formations, and crude oil in ultra-trace concentrations (Velasco-Santos et al 2003). CNTs also form in less extreme conditions such as incinerators (Murr et al , 2005. However, the size, purity, quality, and quantity of CNTs produced by such processes are far below what is needed for laboratory testing or composite material applications.…”

Carbon nanotubes in wood soot

“…We have in fact observed two other wood combustion stream collections with no carbon nanotubes. Furthermore, any adverse health effects attributed to smoke particulates, for any fuel combustion producing mixtures of carbonaceous soot aggregates or multiwall carbon nanotube aggregates, are not likely to differ for these nanoparticulate species since cytotoxicity assays using animal or human lung cells have demonstrated equivalent toxic responses for commercial black carbon composed of carbonaceous spherule aggregates identical to Figure 2, and commercially prepared, multiwall carbon nanotube aggregate material essentially identical to Figure 3 Murr et al, 2005b;Soto et al, 2006).…”

Toxic effects of nanoparticles - differences and similarities with fine particles

“…Of the studies carried out in macrophage and monocyte cells, both SWCNTs and multi-walled CNTs (MWCNTs) were reported to be cytotoxic in murine macrophages (Murr et al, 2005), and the toxicity of different particles was ranked in alveolar macrophages: SWCNT > MWCNT > quartz > C60 fullerene (Jia et al, 2005). The authors of the latter study demonstrated that monocytic cell phagocytic ability was reduced after exposure to all of the nanotubes tested.…”