Relevance of aerosol dynamics and dustiness for personal exposure to manufactured nanoparticles |
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Authors: | Thomas Schneider Keld A Jensen |
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Institution: | (1) National Research Centre for the Working Environment, Copenhagen, Denmark |
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Abstract: | Production and handling of manufactured nanoparticles (MNP) may result in unwanted worker exposure. The size distribution
and structure of MNP in the breathing zone of workers will differ from the primary MNP produced. Homogeneous coagulation,
scavenging by background aerosols, and surface deposition losses are determinants of this change during transport from source
to the breathing zone, and to a degree depending on the relative time scale of these processes. Modeling and experimental
studies suggest that in MNP production scenarios, workers are most likely exposed to MNP agglomerates or MNP attached to other
particles. Surfaces can become contaminated by MNP, which constitute potential secondary sources of airborne MNP-containing
particles. Dustiness testing can provide insight into the state of agglomeration of particles released during handling of
bulk MNP powder. Test results, supported by field data, suggest that the particles released from powder handling occur in
distinct size modes and that the smallest mode can be expected to have a geometric mean diameter >100 nm. The dominating presence
of MNP agglomerates or MNP attached to background particles in the air during production and use of MNP implies that size
alone cannot, in general, be used to demonstrate presence or absence of MNP in the breathing zone of workers. The entire respirable
size fraction should be assessed for risk from inhalation exposure to MNP. |
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