Laboratory bench tests, known as dustiness tests, have been used to evaluate and compare the potential of various powders to cause occupational dust exposure. Dustiness tests are used to develop products with reduced dust emissions. The correlation between dustiness test results and dust exposures was evaluated at two bag dumping and bag filling operations. At one bag dumping and one bag filling operation, there was evidence of a relationship between dustiness test results and dust exposures. In one case, regression analysis showed that dust exposures could be predicted to within nearly one order of magnitude. The variability in this prediction was caused by the inherent variability in the occupational dust exposures. In the other case, there was evidence of a correlation after the data had been adjusted for the effect of varying drop height. At the remaining two operations, no correlation between dust exposures and dustiness test results were observed. These results indicate that the relevance of dustiness tests to occupational dust exposure needs to be evaluated at each site. Because a better option does not exist, manufacturers should continue to use empirical dustiness tests to develop better products in the laboratory. The conclusions reached in the laboratory need to be validated by dust exposure measurements in the field, however.
"These methods have been compared by various groups using a variety of powders (Heitbrink 1990; Carlson et al., 1992; Plinke et al., 1992; Bach and Schmidt, 2008; Schneider and Jensen, 2008; Jensen et al., 2009). Modeling of the aerosolization and dust generation of powders has also been attempted (Plinke et al., 1994a,b; Lanning et al., 1995; Ibaseta et al., 2008). "
[Show abstract][Hide abstract] ABSTRACT: Dustiness may be defined as the propensity of a powder to form airborne dust by a prescribed mechanical stimulus; dustiness testing is typically intended to replicate mechanisms of dust generation encountered in workplaces. A novel dustiness testing device, developed for pharmaceutical application, was evaluated in the dustiness investigation of 27 fine and nanoscale powders. The device efficiently dispersed small (mg) quantities of a wide variety of fine and nanoscale powders, into a small sampling chamber. Measurements consisted of gravimetrically determined total and respirable dustiness. The following materials were studied: single and multiwalled carbon nanotubes, carbon nanofibers, and carbon blacks; fumed oxides of titanium, aluminum, silicon, and cerium; metallic nanoparticles (nickel, cobalt, manganese, and silver) silicon carbide, Arizona road dust; nanoclays; and lithium titanate. Both the total and respirable dustiness spanned two orders of magnitude (0.3-37.9% and 0.1-31.8% of the predispersed test powders, respectively). For many powders, a significant respirable dustiness was observed. For most powders studied, the respirable dustiness accounted for approximately one-third of the total dustiness. It is believed that this relationship holds for many fine and nanoscale test powders (i.e. those primarily selected for this study), but may not hold for coarse powders. Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size. For a subset of test powders, aerodynamic particle size distributions by number were measured (with an electrical low-pressure impactor and an aerodynamic particle sizer). Particle size modes ranged from approximately 300nm to several micrometers, but no modes below 100nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100nm particle contribution in a workplace.
"There is extensive literature regarding the production and measurement of dust aerosols in the laboratory, although these publications generally reflect instruments and experiments not designed to investigate ambient fugitive dust. Most work has instead focused on process control or occupational hygiene in manufacturing (Heitbrink et al., 1990), inhalation toxicology (Shiotsuka et al., 1992), and the pharmaceutical industry (Hindle and Byron, 1995). Still, many techniques, equipment, and findings of these types of studies can be applied to research on atmospheric fugitive dust. "
[Show abstract][Hide abstract] 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 >100nm. 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.
Journal of Nanoparticle Research 10/2009; 11(7):1637-1650. DOI:10.1007/s11051-009-9706-y · 2.18 Impact Factor
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