Exposure to Nanoparticles - Environmental and Human Health Impacts of Nanotechnology - page 337

diameter of C 60 is about 0.7 nm; however, the diameter of the mixed fullerene par-
ticles is about 20 m (sic). The factory has a production capacity of 40 000 kg per

year. Fullerenes are produced in a closed system, minimising the potential for
exposure during production. After the drying process, the fullerene is transported
to, and kept in, a storage tank until it is removed by workers and bagged. During
this procedure, a vacuum cleaner facilitates the bagging operation. After a certain
amount of fullerene is bagged, it is weighed in the same room.
The authors used an SMPS and an optical particle counter to measure the par-
ticle number size distributions of particles ranging in diameter (Dp) from 10 to

µ

> 5000 nm in the fullerene factory and used SEM to examine the morphology of the

particles. Results were presented as number and volume distributions, including
size differentiated times series, enabling comparison of results for a series of activi-
ties, non-work, bagging, use of a vacuum cleaner and moderate agitation. For the
time series, the results were grouped into four size bands, 10- 50 nm, 50 - 100 nm,
100- 2000 nm and 2000 nm. The source, workers and measuring instruments were

all within a 1.5 m range.
A modal diameter of 25 nm was found in the working area during the non-work
period, which the authors considered was probably due to the ingress of outdoor
air. The particle number concentration for Dp

>

< 50 nm and the particle volume

concentration for Dp 2000 nm increased during the bagging operation (peaking

around 20 000 particles ml − 1 , compared with a background of around 10 000 parti-
cles ml − 1 ). Afterward, both of these concentrations decreased when no workers
were present in the room. Peaks were also seen during vacuuming and during agita-
tion (30 000 particles ml − 1 ). The authors considered one possible source of nanopar-
ticles to be an operating vacuum cleaner (in the carbon brushes of the motor). SEM
revealed that the coarse particles emitted during bagging and/or weighing were
aggregates/agglomerates of fullerenes; although the origin of particles with Dp

>

<

50 nm is unclear.
These few studies represent the totality of knowledge on exposures in manufac-
turing and use of new nanoparticles.

8.3.4.2 Exposures in Existing Nanoparticle Processes

Given the absence of real data on exposure to new nanomaterials it is pertinent to
examine data from existing processes where nanomaterials might be used or where
nanomaterials are an unwanted by-product of the process.
Kuhlbusch and Fissan (2006) measured physical and chemical characteristics of
airborne particles (ultrafi ne, PM 1 , PM 2.5 and PM 10 ) in reactor and pelletting areas
during carbon black production. Particle number and mass concentration measure-
ments were conducted in these work areas and at ambient comparison sites at each
of the three carbon black plants. The carbon black production line had three process
steps: reaction- collection, pelletising -drying and packing. In the fi rst process phase,
chemical reactions took place in the reactor to produce the primary carbon black
particles during partial combustion or thermal decomposition of hydrocarbons by
gas-to-particle conversion. Primary particle sizes can range from 1 to 500 nm, with
most produced in the 10-100 nm range. A few to many tens of primary particles