Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 303

Development of new nanomaterials is a major theme of all of these programmes.
Ordinary materials such as carbon or silicon, when reduced to the nanoscale, often
exhibit novel and unpredictable characteristics, such as extraordinary strength,
chemical reactivity, electrical conductivity or other characteristics that the same
material does not possess at the micro or macro-scale. A huge range of materials
has already been produced including nanotubes, nanowires, fullerene derivatives
and other nanoscale materials.
Nanotechnologies are gaining in commercial application. Nanoscale materials
are currently being used in electronic, magnetic and optoelectronic, biomedical,
pharmaceutical, cosmetic, energy, catalytic and materials applications. Areas pro-
ducing the greatest revenue for nanoparticles are reportedly chemical-mechanical
polishing, magnetic recording tapes, sunscreens, automotive catalyst supports, bio-
labelling, electro-conductive coatings and optical fi bres (http://www.nano.gov/html/
facts/appsprod.html ).
Many well known industrial processes produce materials that have dimensions
in the nanometre size range. One example is the synthesis of carbon black by fl ame
pyrolysis, which produces a powdered form of carbon with a very high surface to
mass ratio. While primary particles are generally in the 10-300 nanometer range,
carbon black products are placed into commerce (the fi nal product) as agglomer-
ates, which are much larger in size (100-1000 nanometers in diameter (ICBA,
2008a). Worldwide production of carbon black was approximately 8.1 million
tonnes in 2005 (ICBA, 2008b). Other common materials produced by fl ame pyroly-
sis or similar thermal processes include fumed silica (silicon dioxide), ultrafi ne
titanium dioxide (TiO 2 ) and other ultrafi ne metals such as nickel.
Other industrial processes create and use nanoparticles as part of the process.
An example of this is thermal spraying and coating, where a coating material
(usually metal) is vaporised in a gas fl ame or plasma and deposited as a thin fi lm
onto a surface to improve its hardness or corrosion resistance. Elsewhere, nanopar-
ticles are an undesirable by-product of industrial processes. The most obvious
example of this is welding, which can generate large quantities of nanoparticles
usually in the form of a well defi ned plume of aggregated nanoparticles. Particles
in the nanometre size range are also produced in large quantities from diesel
engines and from domestic activities such as gas cooking.
Nanometre sized particles are also found in the atmosphere where they originate
from combustion sources (e.g. traffi c, forest fi res), volcanic activity and from atmo-
spheric gas to particle conversion processes such as photochemically driven nucle-
ation. In fact, nanoparticles are the end product of a wide variety of physical,
chemical and biological processes, some of which are novel and radically different,
while others are quite commonplace.
It is widely acknowledged that there is a lack of information concerning the
human health and environmental implications of manufactured nanomaterials and
concerns have been expressed regarding potential risks to health that might arise
during their manufacture, use and disposal (European Commission, 2004). There is
a view that the biological activity of nanoparticles, which have both benefi cial and
potentially adverse effects, tends to increase as their size decreases. Evidence for
other particle types (e.g. 'low toxicity dusts') clearly shows that the toxicity of these