Single Wall Carbon Nanotubes (SWCNT)

Nanomaterial dustiness

Administrative data

Endpoint:

nanomaterial dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2012

Report date:

2012

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Vortex Shaker (VS) method in collaboration with INRS (The French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases)

Version / remarks:

CEA internal procedure: AQ/PRT/SEN/162 Version A applicable since Oct. 17th, 2017

Deviations:

no

Principles of method if other than guideline:

The Vortex Shaker (VS) method consists of a specially designed stainless steel cylindrical tube with a conical bottom agitated by a vortex (IKA® Vortex Genius3) in which the test powdered material is placed (0.5 cm³ of powder). The tube is continuously shook according a circular orbital motion (displacement amplitude 4 mm, rotation speed 1800 rpm). HEPA filtered air, controlled at 50 ±5% relative humidity and 21±3 °C, pass through the tube in order to transfer the released aerosol to the sampling and measurement section at a flow-rate of 4.2 lpm. All tests were conducted with VS method using approximately 0.5 cm³ powder precisely weighed and placed in the sample vial. The sample is allowed conditioning in the 50 ±5% relative humidity 24 hours before the shaker for a powder agitation period of 60 seconds. Next to the bench are standard laboratory characterization devices. For the measurement of the particle size distribution, an Electrical Low-Pressure lmpactor (ELPITIVI Classic, Dekati) is used to determine number-based particle size distribution in aerodynamic equivalent diameter with a time step of 1 second. Number concentration is determined using handheld CPC (Model 3007, TSI). SEM/TEM images are acquired on some samples after aerosolization and dust collection on filter also conditioned at 50 ±5% relative humidity and 21 ±3 °C during 24 hours (PTFE) and TEM grid.
The test protocol has two separate steps. The experimental set-up shown above is therefore used once with a sampling line downstream for the mass-based dustiness index in respirable fraction (a), and once with another measurement line for determining the number-based dustiness index, for characterizing particle-size distribution of the emitted aerosol, and for collecting airborne particles for subsequent SEM and TEM observations (b).

GLP compliance:

not specified

Other quality assurance:

other: The quality management system in place at CEA is certified according to ISOQOO1:2015

Type of method:

vortex shaker

Details on methods and data evaluation:

The Vortex Shaker (VS) method was used, in collaboration with INRS (The French National Research and Safety Institute for the Prevention of Occupational Accidents and Diseases). Intercomparison study between CEA and INRS set-up is undergoing through a collaboration with Claire Dazon who initially published dustiness results on carbon nanotubes (C. Dazon, O. Witschger, S. Bau, R. Payet, K. Beugnon, G. Petit, T. Garin, L. Martinon; Dustiness of 14 carbon nanotubes using the vortex shaker method; Journal of Physics: Conference Series, 838, (2017), 012005.).

Test material

Test material information

Constituent 1

Reference substance name:

Tin dioxide

EC Number:

242-159-0

EC Name:

Tin dioxide

Cas Number:

18282-10-5

Molecular formula:

O2Sn

IUPAC Name:

Tin Dioxide

Test material form:

solid: nanoform

Details on test material:

Sample Reference: W0167

Specific details on test material used for the study:

OCSiAl represented that the material tested was the same material subject to the US-EPA consent order for PMN-17-257. The TUBALL NTC were observed as received through SEM imaging using carbon substrates.

Reference material / nanomaterial and sample identification number

Reference

Reference substance name:

Unnamed

IUPAC name:

carbon

Inventory number:

InventoryMultipleMappingImpl [inventoryEntryValue=EC 943-098-9]

CAS number:

7440-44-0

Identifier:

CAS number

Identity:

7440-44-0

Identifier:

IUPAC name

Identity:

single wall carbon nanotubes

Identifier:

other: Molecular formula

Identity:

C

Identity:

Single Wall Carbon Nanotubes (SWCNT)

Molecular formula:

Carbon.

Morphological features:
- Tube cylindrical surface is formed by 6-membered rings consisting of carbon atoms linked by a double bond.
- Carbon nanotube chirality is random.
- Tube length: 1 - 10 μm.
- Agglomeration: CNTs tend for form bundles

Molecular weight:

ca. 16

SMILES notation:

[C]

InChl:

not applicable

Data gathering

Calibration:

The mass-based dustiness index in the respirable fraction (DIRM), reported in milligrams of aerosol per kilogram of powder, was calculated by dividing the mass collected by the respirable sampling filter (in milligrams), by the mass Mo of the powder placed in the cylindrical tube (in milligrams): DIRM = Δmf/Mo * QVS/QC * 100.000
The limit of detection of the mass-based dustiness index (LOD (DIRM)) corresponds to the ratio of the gravimetric detection limit to the mass of the test sample, thus the LCD (DIRM) was determined for each experiment. The limit of detection associated with the gravimetric analysis was obtained from the reproducibility of the blank PTFE membrane weights as measured before and after their assembly within a 37 mm sampling cassette used with the respirable cyclone. The repeat weight measurements took place over a half-month period and were performed on 3 series of 3 PTFE membranes from the same batch. The gravimetry limit of detection finally obtained was 4 µg. Assuming a mass Mo of 51.67mg, this corresponds to a LCD (DIRM) of 80.1 mg/kg.
The number-based dustiness index in the respirable fraction (DIRN), given in particles per milligram of powder, was calculated by dividing the number of particles emitted over the duration of the vibrating period (Le. 60 sec) (in particles) by the mass Mo of the powder placed in the cylindrical tube (in milligrams): DIRN = 1/Mo SUM(CCPC(t) * QVS * ΔtCPC * 1000/60
The average, the standard deviation (SD), the Relative Standard Deviation (RSD) and the Confidence Interval (Cl) were calculated on the average of the three experiments.

Reproducibility:

All measurements were performed in triplicates.

Results and discussion

Dustiness index

Dustiness index 1

Mean:

1 660 other: mass-based dustiness index DI(RM) in mg/kg

St. dev.:

818 mg/kg

Dustiness index 2

Mean:

146 000 other: number-based Dustiness Index DI(RN) in #/mg

St. dev.:

84 500 other: #

Any other information on results incl. tables

The average bulk density obtained was 0.10 g/cm³ from the triplicates studied. This value is in the range of other types of carbon nanotubes (CNTs) reported in the publication of C. Dazon et al.

Applicant's summary and conclusion

Conclusions:

The mass-based dustiness index was calculated: DI(RM) = 1.66 10³ mg/kg (limit of detection was calculated: LOD (DI(RM)) = 80.1 mg/kg. The measurement of dustiness in terms of respirable mass fraction were performed and a number-based dustiness index was calculated: DI(RN) = 1.46 10⁵ 1/mg. The characterization of the aerosol from its particle size distribution given by the ELPI shows one mode at 1.2 µm, which is in agreement with the SEM/TEM observations of collected airborne material.

Executive summary:

The measurement of dustiness in terms of respirable mass fraction were performed and a mass-based dustiness index was calculated: DI_RM= 1.66 10³ mg/kg. The limit of detection of the mass-based dustiness index was calculated (LOD (DI_RM) = 80.1 mg/kg) and is far below the measured value of mass-based dustiness index of the TUBALL nanotubes.

The measurement of dustiness in terms of respirable number fraction were performed and a number-based dustiness index was calculated: DI_RN = 1.46 10⁵ 1/mg. The characterization of the aerosol from its particle size distribution given by the ELPI shows one mode at 1.2 µm, which is in agreement with the SEM/TEM observations of collected airborne material.

The results obtained with the VS method are quite reproducible. The dustiness indexes, (DI_RM= 1.66 10³ and DI_RN = 1.46 10⁵) compared to the published results (C. Dazon, O. Witschger, S. Bau, R. Payet, K. Beugnon, G. Petit, T. Garin, L. Martinon; Dustiness of 14 carbon nanotubes using the vortex shaker method; Journal of Physics: Conference Series, 838, (2017), 012005.) are in the same range (~1600 - 300000 mg/kg), but at the very low end, although different configuration and measurement protocols were used for the tests.