Physical and Chemical Determinants of Nanofiber/Nanotube ToxicityEPA Grant Number: R831719
Title: Physical and Chemical Determinants of Nanofiber/Nanotube Toxicity
Investigators: Hurt, Robert H. , Kane, Agnes B.
Institution: Brown University
EPA Project Officer: Carleton, James N
Project Period: August 1, 2004 through July 31, 2007
Project Amount: $335,000
RFA: Exploratory Research to Anticipate Future Environmental Issues: Impacts of Manufactured Nanomaterials on Human Health and the Environment (2003) RFA Text | Recipients Lists
Research Category: Nanotechnology , Health , Safer Chemicals , Health Effects
Tubular and fibrous materials play a very special role in emerging nanotechnologies, but may show asbestos-like toxicity in humans upon inhalation. For asbestos fibers, it is known that both surface-reactive transition metals and fibrous geometry are major determinants of toxicity. Most commercial nanotubes/fibers are complex materials containing transition metal catalysts or residues and exhibiting complex distributions of length and diameter, as well as variability in defect density and surface functional groups.
The objective the proposed project is to carry out a carefully designed parametric study of the physical and chemical factors that underlie nanofiber/tube toxicity, in which the effects of shape, size, purity, and surface chemistry are carefully isolated by special synthesis techniques developed at Brown University.
This project focuses on model carbon nanofibers and nanotubes synthesized by non-catalytic templating routes from high-purity liquid-phase precursors. This approach allows explicit control of size and shape, and the as-produced materials are essentially free of transition metal impurities. Subsequent combinations of metal doping (spiking) and surface oxidation of these pure nanocarbons will then be carried out to assess directly the effects of metals and hydrophilicity. A panel of fibrous and tubular nanocarbons will be synthesized, post-processed, and characterized, and the following toxicologic endpoints will be determined over a range of doses:(i) phagocytosis, (ii) cell toxicity, (iii) induction of proinflammatory gene expression, and (iv) genotoxicity. These short-term toxicologic assays will establish the toxicity of these nanomaterials relative to carcinogenic asbestos fibers and nontoxic titanium dioxide nanoparticles.
We hypothesize that fiber length and availability of reactive transition metals are major determinants of carbon nanofiber/tube toxicity. On the basis of our preliminary data we predict that nanomaterials doped with transition metals will be more toxic than pure carbon nanomaterials. This mechanistic study will provide guidance for the manufacturing of nanomaterials with minimal human health impact (e.g. through catalyst selection, purification, size/shape control), while maintaining desirable material properties and functions.