carbon nanotube

Toxicology of Carbon Nanomaterials

Understanding the environmental impact of carbon nanotubes remains a vital component of government and industry’s push to capitalize on the scientific advances of the past decade. As such, National Institute of Standards and Technology announcement that they have recently released the first certified “reference material” for carbon nanotube soot provides a glimpse at the direction in which manufacturers must travel in order to vouchsafe their products.

The certification of a reference material provides scientists with a standardized comparison point for toxicology studies and is an important part of establishing large-scale commercial ventures, as well as testing them for potential health and environmental hazards.

The toxicity of carbon nanotubes has been part of the scientific landscape for several years; it is far from recent news that in 2006 Professor Robert Hurt and Professor Agnes Kane from Brown University, together with Marc Monthioux from the Center for Material Elaboration & Structural Studies (CEMES) in France edited a special issue of the journal Carbon on the subject of Toxicology of Carbon Nanomaterials. approching the manufacture and use of  fullerenes, nanotubes, nanofibers, and a wide variety of related forms the report focused on how these nanomaterials may enter the human body through a variety of processes, including inhalation, skin contact, ingestion, or intentional injection. Attention was also paid to how inclusion in the food chain via microorganisms may affect plants life, or animals, if nanomaterials were released into the environment in significant quantities.

In the light of these concerns the NIST decision to certify a reference material is a much overdue step forward.

NIST, which is part of the U.S. Department of Commerce, has identified carbon nanotube soot,

“perhaps the archetype of all nanoscale materials.”

Following concerns arising from study of rats exposed to carbon nanotubes the National Institute for Occupational Safety and Health issued draft recommendations that anybody directly exposed to CNT’s during the manufacturing process take care to avoid any inhalation exposure to the material. A growing weight of evidence points to the possibility that nanomaterials can behave in ways in which we are unaccustomed to. For instance, studies by Liu et al published in 2009 show how larval and adult Drosophila melanogaster cope under a variety of situations in which nanomaterials had been incorporated into their environment. The results were mixed, and not entirely as expected.

Dietary uptake of fullerene C60, carbon black (CB), or single-walled or multiwalled nanotubes (SWNTs, MWNTs) delivered through the food to the larval stage had no detectable effect on egg to adult survivorship, despite evidence that the nanomaterials are taken up and become sequestered in tissue. However, when these same nanocarbons were exposed in dry form to adults, some materials (CB, SWNTs) adhered extensively to fly surfaces, overwhelmed natural grooming mechanisms, and led to impaired locomotor function and mortality. Others (C60, MWNT arrays) adhered weakly, could be removed by grooming, and did not reduce locomotor function or survivorship. Evidence is presented that these differences are primarily due to differences in nanomaterial superstructure, or aggregation state, and that the combination of adhesion and grooming can lead to active fly borne nanoparticle transport.

Environ. Sci. Technol., 2009, 43 (16), pp 6357–6363

Toxicologists remain at the forefront of determining what’s safe and what’s harmful, and so the latest development from NIST will be welcomed for its part in making possible standardised and consistent experimental conditions. Making best use of the materials in the safest way remains the goal of the scientific and industrial community.

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