Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 336

These exposure results provide strong indications that: (i) conventional exposure
monitoring methods, such as personal and area sampling, combined with newly
emerging nanoparticle measurement techniques, may be effective in measuring
MWCNT exposure concentrations; (ii) MWCNTs can be counted like asbestos and
measured for the number of tubes per millilitre using TEM, despite the unavail-
ability of supplementary light microscopy, as suggested by Donaldson et al. (2006) ,
which would be inadequate because of its lack of size resolution; and (iii) conven-
tional engineering control measures work well for MWCNT exposure control.
Yeganeh et al. (2008) carried out a study to characterise airborne particle con-
centrations during the production of carbonaceous nanomaterials, such as fuller-
enes and carbon nanotubes, in a ' small ' commercial nanotechnology facility in the
United States. They measured fi ne particle mass concentrations (PM 2.5 ), submicron
size distributions and photoionisation potential, an indicator of the particles' car-
bonaceous content. There was no attempt to characterise the particles in terms of
morphology. Fine particulate matter mass concentrations (aerodynamic diameter

< m, PM 2.5 ) were measured using a light-scattering aerosol photometer (TSI

DustTrak 8520); submicrometer particle number concentrations and size distribu-
tions were measured using a scanning mobility particle sizer (TSI SMPS 39301 and
CPC 3025A) with long and nano differential mobility analysers (LDMA and
NDMA) that measure particles between 14 and 673 nm and 4- 160 nm, respectively;
photoionisation potential, an indicator of surface chemical composition, was mea-
sured using a photoelectric aerosol sensor. The PAS' response has been shown to
be proportional to polycyclic aromatic hydrocarbon, elemental carbon, and/or
sooty content of the particles and is used here as an indicator of carbonaceous
particle composition. Measurements were made at three locations, inside the facil-
ity inside the fume hood where nanomaterials were produced, just outside the fume
hood and in the background.
There was no specifi c attempt to discriminate between manufactured nanoma-
terials and naturally occurring or incidental particles. Average PM 2.5 and particle
number concentrations were not signifi cantly different inside the facility or out-
doors. However, large, short term increases in PM 2.5 and particle number concentra-
tions were associated with physical handling of nanomaterials and other production
activities. In many cases, an increase in the number of sub-100 nm particles accounted
for the majority of the increase in total number concentrations. Photoionisation
results indicate that the particles suspended during nanomaterial handling inside
the fume hood were carbonaceous and therefore likely to include engineered
nanoparticles, whereas those suspended by other production activities taking place
outside the fume hood were not. Measurements made within the fume hood clearly
showed that ultrafi ne particles were aerosolised during handling. However, the
engineering controls at the facility appear to be effective at limiting exposure to
nanomaterials.
Fujitani et al. (2008) measured the physical properties, number concentrations
and number size distributions of aerosols in a fullerene factory in Japan. In this
factory, the mixed fullerene is extracted by solvent from soot generated by the
combustion of hydrocarbon-oxygen mixtures. Mixed fullerenes include C 60 , approx-
imately 60%, C 70 , approximately 25%, and other higher fullerenes. The molecular

2.5 µ