Evaluating the capabilities of portable black carbon monitors and photometers for measuring airborne carbon nanotubes

Hashimoto, Naomi; Ogura, Isamu; Kotake, Mari; Kishimoto, Akira; Honda, Kazumasa

doi:10.1007/s11051-013-2033-3

Cited by 14 publications

(19 citation statements)

References 51 publications

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“…CNTs released in workplaces are often determined using thermal carbon analysis methods, such as National Institute for Occupational Safety and Health (NIOSH) method 5040 [5][6][7][8][9][10] or the IMPROVE protocol 11) , also used for quantifying CNTs [12][13][14][15] . In addition, by measuring respirable-sized MWCNT dust using both a black carbon monitor (BCM) and thermal carbon analysis, a relationship between the analytical methods was detected 16) . However, it is difficult to identify whether or not some CNTs are released during the working process when elemental carbon exists in the background atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Exposure assessment of carbon nanotubes at pilot factory focusing on quantitative determination of catalytic metals

Kato

Nagaya

Matsui

et al. 2017

Journal of Occupational Health

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Objectives: The application of multiwall carbon nanotubes (MWCNTs) currently extends to various fields. However, it has been reported that exposure to CNT causes hazardous effects on animals and cells. The purpose of this study was to quantify the exposure to MWCNT in MWCNT/polymer composites for exposure assessment. We focused on catalytic metals included in the MWCNT and the diameter of dust released during the working processes. Although the Co in MWCNTs is not a common catalyst, it was used as a tracer in this study. Methods: A field survey was conducted in a MWCNT/polymer composite pilot factory. Airborne MWCNTs were monitored using black carbon monitors (BCMs) and optical particle sizers (OPSs) and collected on a filter. The MWCNT powder, all polymer resins used during the working processes, and the filter were analyzed in our lab using inductively coupled plasma mass spectrometry (ICP-MS) and electron microscopic observation. Results: The mean concentration of airborne MWCNT contained in the collected dust was 0.92 μg/m3 a few meters away from the extruder during the working processes (using elemental analysis). The maximum concentration measured using BCMs was shown to be seven times higher than the base concentration during the pelletizing process of polycarbonate (PC) and MWCNT composites. However, free, isolated, and unbound agglomerated MWCNTs were not detected using scanning electron microscopic (SEM) observation. Conclusions: The result obtained by elemental analysis indicated it was possible to quantify MWCNT in composites. The mean concentration at this factory was lower than the recommended exposure limit. However, additional studies during the pelletizing process are required in the future.

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Section: Introductionmentioning

confidence: 99%

Exposure assessment of carbon nanotubes at pilot factory focusing on quantitative determination of catalytic metals

Kato

Nagaya

Matsui

et al. 2017

Journal of Occupational Health

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“…These differences in responses could be caused by variations between monitors, powder types, and the use of different aerosol concentrations. The aerosol concentrations used in this study (1-30 µg/m 3 ), were much lower than those used (100-700 µg/m 3 ) by Hashimoto et al (2013). A limitation of the aethalometer noted in other studies was the tendency of the concentration reported to drift downward despite no changes in the actual concentration (Jiminez et al, 2007;Kirchstetter & Novakov, 2007).…”

Section: Discussionmentioning

confidence: 54%

“…The relative responses of the primarily carbon-based powders ranged from 0.74-1.17. In the study conducted by Hashimoto et al (2013), the relative responses of the aethalometer ranged from 0.12-0.91. Only carbon black was found to have a response (0.74) lower than this range.…”

Section: Discussionmentioning

confidence: 99%

“…A review of several studies by the Environmental Protection Agency (2012) indicated a high correlation (r = 0.86 +/-0.11) between BC and EC with a BC:EC ratio of the correlated data typically near one, suggesting that an aethalometer can evaluate EC concentrations. A study evaluated the response of an aethalometer to ten CNT samples and found the device to underestimate the air concentrations as compared to NIOSH Method 5040 (Hashimoto et al, 2013). The authors suggested the use of correction factors for each unique CNT type to account for the difference in the response between NIOSH Method 5040 and the aethalometer.…”

Section: Aethalometersmentioning

confidence: 99%

“…Overall, there have been very few studies using direct-reading instruments including aethalometers to evaluate exposures to CNTs in the workplace. Hashimoto et al (2013) evaluated an aethalometer's ability to measure ten types of CNTs and found the device to underestimate the air concentrations by as much as 88% as compared to NIOSH Method 5040.…”

Section: Introductionmentioning

confidence: 99%

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Investigation of exposure assessment methods and filtration of carbon nanotubes

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The research presented in this doctoral dissertation aimed to improve knowledge on methods to evaluate exposures to carbon-containing nanomaterials and to develop optimized respiratory filters properties to protect workers from these exposures while minimizing discomfort due to breathing resistance. In the initial study, a novel laboratory-based system generated aerosols of four carboncontaining powders (carbon black, a small-diameter (<8 nm) multi-walled carbon nanotube (MWCNT), a large-diameter (50-80 nm) MWCNT, and a nickel-coated MWCNT) to evaluate the effectiveness of NIOSH Method 5040 for measuring masses as low as 1 μg. A targeted mass of a powder ranging from 1 to 30 μg was deposited on filters for gravimetric and elemental carbon (EC) analysis. The gravimetric mass was compared to the EC mass, and a regression model developed for each powder type. Additionally, the limit of detection (LOD) of the NIOSH Method 5040 for each powder type was determined. The regression models had significant slopes relative to zero for all powder types with all but carbon black demonstrating a statistical difference between the two methods. The LOD of NIOSH Method 5040 ranged from 4.5 for small-diameter MWCNTs to 31.8 μg for nickel-coated MWCNTs. Assuming a sample flow rate of 4.2 L/min and an 8-hour sample duration, the concentration-based LOD for NIOSH Method 5040 ranged from 2.2 μg/m 3 for small-diameter MWCNTs to 15.8 μg/m 3 for nickel-coated MWCNTs. These results indicate the analysis of EC is affected by the structure and elemental content of the CNTs. Additionally, based on the LOD determined for each powder type, the method may not be sufficient to assess exposures at and below the recommended exposure limit accurately without sampling durations longer than 8 hours. A second study used a laboratory-based system to evaluate an aethalometer response to carbon-containing nanomaterials including carbon black and MWCNTs. Concentrations ranging vii TABLE OF CONTENTS LIST OF TABLES .

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