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Dustiness of fine and nanoscale powders.

Evans DE, Turkevich LA, Roettgers CT, Deye GJ, Baron PA - Ann Occup Hyg (2012)

Bottom Line: For many powders, a significant respirable dustiness was observed.Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size.It is therefore unlikely that these materials would exhibit a substantial sub-100 nm particle contribution in a workplace.

View Article: PubMed Central - PubMed

Affiliation: National Institute for Occupational Safety and Health, Chemical Exposure and Monitoring Branch, Division of Applied Research and Technology, 4676 Columbia Parkway, MS-R7, Cincinnati, OH 45226, USA. dje3@cdc.gov

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 300 nm to several micrometers, but no modes below 100 nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100 nm particle contribution in a workplace.

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. Time dependence of respirable particle mass concentration (measured by a photometer) for Pyrograf III CNFs, following initial dispersion of 5mg within the dustiness chamber.
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Figure 3: . Time dependence of respirable particle mass concentration (measured by a photometer) for Pyrograf III CNFs, following initial dispersion of 5mg within the dustiness chamber.

Mentions: Figure 3 presents a time series of respirable mass concentration. The photometer measurements provided a reasonable estimate of the respirable mass concentration for these carbon nanofibers and therefore no further calibration or correction factor was required (Evans et al., 2010). The exponential decay of concentration (τ = 55.6 s = 0.927min, R2 = 0.995) is consistent with the dominant particle loss mechanism being dilution (removal of contaminated air through sampling and replacement with clean air: Q = V/τ = 5.7 l/0.927min = 6.2 l min−1). Gravitational settling and losses to the chamber walls did not appear to significantly contribute (~5%) to the concentration decay within the chamber.


Dustiness of fine and nanoscale powders.

Evans DE, Turkevich LA, Roettgers CT, Deye GJ, Baron PA - Ann Occup Hyg (2012)

. Time dependence of respirable particle mass concentration (measured by a photometer) for Pyrograf III CNFs, following initial dispersion of 5mg within the dustiness chamber.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3750099&req=5

Figure 3: . Time dependence of respirable particle mass concentration (measured by a photometer) for Pyrograf III CNFs, following initial dispersion of 5mg within the dustiness chamber.
Mentions: Figure 3 presents a time series of respirable mass concentration. The photometer measurements provided a reasonable estimate of the respirable mass concentration for these carbon nanofibers and therefore no further calibration or correction factor was required (Evans et al., 2010). The exponential decay of concentration (τ = 55.6 s = 0.927min, R2 = 0.995) is consistent with the dominant particle loss mechanism being dilution (removal of contaminated air through sampling and replacement with clean air: Q = V/τ = 5.7 l/0.927min = 6.2 l min−1). Gravitational settling and losses to the chamber walls did not appear to significantly contribute (~5%) to the concentration decay within the chamber.

Bottom Line: For many powders, a significant respirable dustiness was observed.Neither total nor respirable dustiness was found to be correlated with BET surface area, therefore dustiness is not determined by primary particle size.It is therefore unlikely that these materials would exhibit a substantial sub-100 nm particle contribution in a workplace.

View Article: PubMed Central - PubMed

Affiliation: National Institute for Occupational Safety and Health, Chemical Exposure and Monitoring Branch, Division of Applied Research and Technology, 4676 Columbia Parkway, MS-R7, Cincinnati, OH 45226, USA. dje3@cdc.gov

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 300 nm to several micrometers, but no modes below 100 nm, were observed. It is therefore unlikely that these materials would exhibit a substantial sub-100 nm particle contribution in a workplace.

Show MeSH
Related in: MedlinePlus