Carbon Nanotubes Risk Assessment. The Secret Behind Carbon Nanotubes (CNTs) the Miracle Materials of the 21st Century By Regina Ma & Aster Zemenfeskidus Winter 2010. Background. History of Carbon Nanotubes (CNTs).
The Secret Behind
Carbon Nanotubes (CNTs)
the Miracle Materials of the 21st Century
Regina Ma & Aster Zemenfeskidus
*Note: In each case, the form of nanotube is identified by a sequence of two numbers, the first one of which represents the number of carbon atoms around the tube, while the second identifies an offset of where the nanotube wraps around to.
*TEM – Transmission Electron Microscopy
A polymer-wrapped single-walled carbon nanotube
High-resolution transmission electron microscopy (HRTEM) images of Ag-nanoparticles deposited on N-doped and undoped carbon nanotubes: (a) Ag-nanoparticles (2-5 nm in diameter) deposited on CNxMWNTs. The image reveals a nanotube bundle which is uniformly coated with Ag-nanoparticles, and (b) Ag nanoparticles (10-20 nm in diameter) poorly coating carbon MWNTs (undoped); the latter sample was produced by the reduction of Silver nitrate (AgNO3) in DMF in presence of MWCNTs. Note the clear absence of Ag-nanoparticles covering the undoped material.
* dope - altering properties of the tube so as to alter the electronic, mechanical and chemical properties of the tubes
Four groups of mice (Poland et al.):
*Note: these results indicate that lesions caused by the long nanotubes would have developed into mesothelioma (cancer of lung lining)
Five groups of mice (Poland et al.):
Source: Nature Nanotechnology
*Note: hazardous health effects, hence, depend on the route of exposure and the type of the nanoparticle to which an individual or animal is being exposed
Nanotubes inside lung cells
Particles less than 5.0 microns are deposited in the lower respiratory tract
Animal Study (single exposure)
Conversion used 1 fiber/cc = 5mg/m3
Occupational Safety and Health Administration Permissible
Exposure Limit (OSHA PEL) for graphite: 5mg/m3/8hr = 1
American Conference of Industrial Hygienists Threshold Limit
Value (ACGHI TLV) for asbestos: 0.1 fibers/cc/8hr
OSHA PEL for asbestos: 0.1 fibers/cc/8hr
National Institute for Occupational Safety and Health
Recommended Exposure Limit (NIOSH REL) for asbestos: 0.1
NOAEL? from animal study:
1mg/m3/6hr = 1.6 fibers/cc/8hr
LOAEL? from animal study:
30mg/m3/6hr = 8 fibers/cc/8hr
[1.6 fibers/cc/8hr] /  = 0.0016 fibers/cc/8hr
[8 fibers/cc/8hr] /  = 0.008 fibers/cc/8hr
*Compared with ACGHI TLV, NIOSH REL, OSHA PEL for asbestos:
0.1 fibers/cc/8hr& OSHA PEL for graphite:1 fibers/cc/8hr
*Note: No NOAEL and LOAEL for MWCNTs. The numbers
above were based on whether adverse health effects were
observed during the experiment.
NOT supportive of health or community
Louis Brus and Sumio Iijima received the Kavli Prize in nanoscience at an award ceremony in Oslo, Noway in September 2008. In the middle Fred Kavli who initiated the prize.
The inhalation of asbestos fibres can cause lung diseases and cancers
“Absence of evidence is not evidence of absence!”