Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 347

handling activities with CNT resulted in measurable airborne exposure concentra-
tions. They did not, however, attempt to quantify these in terms of 'fi bre count
concentration', as would be used for other high aspect ratio particles. They did not
conclusively demonstrate that fi bre type aerosols were produced in this activity.
Indeed, most of the aerosol which they observed was amorphous carbon, catalyst
particles or aggregates of CNT. On the other hand, Han et al. (2008) showed clearly
that during handling of MWCNT in the production of composites, MWCNT were
released into the atmosphere in a form that enabled them to be counted using a
method based on current techniques for fi brous aerosols. They also showed,
however, when good ventilation control was applied to the process, that release was
effectively contained and exposures were negligible.
Yeganeh et al. (2008) showed effective control of the release of nanoparticles in
a small commercial nanotechnology facility producing fullerenes. No attempt was
made to assess the morphology of the particles. Fujitani et al. (2008) , however, did
observe increases in the airborne concentrations associated with bagging in a fuller-
ene factory, even though the primary product was fullerene aggregates/agglomer-
ates with a diameter of 20000nm. Interestingly, Kuhlbusch and Fissan (2006)
reported release of sub-100 nm particles in a carbon black production facility, which
they attributed to leaks in the ventilation seals.
In seems clear that, based on theory and on limited experimental evidence, there
are conventional control strategies and systems available which may be used to
control exposures in nanoparticle processes. Engineering controls should be able
to be designed to provide suffi cient levels of containment. Filtration systems includ-
ing respiratory protective equipment should be effective providing that they are
used and maintained correctly.
Until relatively recently, less emphasis has been placed on dermal exposure as
a route of exposure. One consequence of this is that the effectiveness of
control measures to prevent dermal exposures are poorly understood and almost
certainly not as effective as approaches to control exposure by inhalation. Studies
evaluating the effi cacy of gloves and suits to control dermal exposure are beginning
to emerge.
At the present time there is very little available information about the number
of people who are occupationally exposed to engineered nanoparticles. Probably,
the number is relatively small. Aitken et al. (2004) estimated that approximately
2000 people are currently employed in the United Kingdom in the university/
research sector and in new nanoparticle companies in activities in which they may
potentially be exposed to nanoparticles in some form. It is certainly the case that
the number of people in the university/research sectors and in new nanoparticle
companies may increase substantially over the next few years. The proportion of
those involved in existing chemical and pharmaceutical companies and in other
powder handling activities who are exposed to nanoparticles is likely to increase
substantially as the use of nanoparticle materials increases.
Already, there is signifi cant potential for consumers to become exposed to
nanoparticles from a whole series of products, from personal care products to food
additives. This exposure can be by inhalation, through the skin or by ingestion,
dependent on the product. There are no good estimates of current levels of expo-