Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 318

and its application. This can be easily imagined by considering two potential appli-
cations, both of which are already identifi ed applications for various classes of
nanomaterials.
The fi rst example is the incorporation of nanomaterials into paint. Nanomaterials
used in paints include metals and metal oxides (Aitken et al. , 2006 ). Exposures
resulting from use of paint containing nanoparticles within the formulation will be
dependent on the method of use (painting). Application of paints is commonly
done though a spraying process. This would result in the generation of an aerosol
of fi ne droplets of the solvent material in which the nanomaterial component would
be suspended along with other components (e.g. binders, thinners, additives, etc.).
Exposure could therefore be to these droplets or to matrices in which the solvent
has evaporated leaving a residual aggregate formed from the other components of
the paints including any nanomaterial component. The particle size of these objects
could be highly variable and may or may not be in a size range considered to be a
nanoparticle. While it is unlikely that this scenario will lead to exposure to indi-
vidual nanoparticles of the component nanomaterial, it is likely that aerosols will
be in a size range which can be inhaled into the respiratory tract.
Whilst exposure by inhalation would be a principle concern, exposure to the skin
and by ingestion through hand-to-mouth contact are also plausible. Exposure could
be reduced by various control methods, including use of a ventilated spray booth
or by using personal Respiratory Protective Equipment (RPE).
The levels of exposure would be entirely dependent on the details of the process
(equipment used, quantity of material, object being coated), on the individual
applying the coating and the working practices used. So for the same paint applied
in a different way, for example by brushing, the exposure characteristics are likely
to be very different. In this case the likelihood of generating an inhalable or respi-
rable aerosol would be much lower. Hence, exposure by inhalation is likely to be
much less. However, exposure to the skin, for example from holding the paintbrush
without wearing a suitable glove, is likely to be much higher.
At the current time there are no published data relating to exposures to nano-
materials in scenarios of this type. Nanomaterials can be used in similar applications
including powder coating, antimicrobial coatings and dirt repellent coatings. The
exposure scenarios in these applications would be similar but the nature, level and
duration of exposure could differ greatly.
A second example is the use of nanomaterials incorporated into a composite
material. Naturally formed nanoparticles such as nanoclays have been used as fi llers
in composite materials for many years. Now manufacturers are increasingly turning
to nanomaterials such as carbon nanotubes, seeking to use their properties of
strength and lightness to create stronger lighter composites. For composites, expo-
sures could occur during the manufacturing process or from the powder handling
processes described earlier. It is plausible that that following manufacture, the
composite material would be cut, shaped, drilled or surface processed prior to its
distribution. These fi nishing activities may also result in exposure due to the release
of particles into the air. In these circumstances, it is unlikely that single nanopar-
ticles of the component nanomaterials will be released. It is more likely that aggre-
gates of the nanoparticles, perhaps in the presence of a binder, will be the