Cerium dioxide

Nanomaterial dustiness

Administrative data

Endpoint:

nanomaterial dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 26 April 2018 to 12 October 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:

2018

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

other: DIN 55992-1:2006 "Determination of a parameter for the dust formation of pigments and extenders - Part 1: Rotation method"

Test guideline 2

Qualifier:

according to guideline

Guideline:

other: DIN EN 481

Test guideline 3

Qualifier:

according to guideline

Guideline:

other: DIN 18121-1

GLP compliance:

no

Type of method:

rotating cylinder

Details on methods and data evaluation:

The dust fractions of this substance was determined according to the DIN 55992-1:2006 method. The different dust fractions are defined in DIN EN 481 as the:
- inhalable fraction,
- thoracic fraction and
- respirable fraction.
The modified Heubach procedure was applied. ln the process, the substance sample was mechanically stressed in a rotating drum (dust generation device), and both the dust already contained in this sample and the dust generated due to abrasion were removed from the dust generation device by an air current. The proportion of dust separated and considered as dust with the ability to become airborne was fed into a seven-stage cascade impactor connected to the dust generation device. Particle size classification was conducted by subsequent weighing of the respective dust masses deposited on the individual cascade stages reflecting certain particle size ranges.
The "total dustiness" value was determined as the ratio of the mass of removed dust to the total sample mass initially weighed in.
Subsequently, the dustiness values for the inhalable, thoracic and alveolar fractions according to DIN EN 481 were determined.

Test material

Test material information

Constituent 1

Reference substance name:

Cerium dioxide

EC Number:

215-150-4

EC Name:

Cerium dioxide

Cas Number:

1306-38-3

Molecular formula:

CeO2

IUPAC Name:

cerium dioxide

Test material form:

solid: nanoform

Data gathering

Instruments:

Heubach dust meter with a rotating drum (dust generation device) applying the modified Heubach procedure

Calibration:

Not specified

Reproducibility:

Not specified

Results and discussion

Dustiness index

Key result

Mean:

670 665.1 mg/kg

Remarks on result:

other: Total dustiness is given here (ratio of the mass of removed dust to the total sample mass initially weighed in).

Remarks:

Standard deviation is not available in the study report.

Any other information on results incl. tables

Table 1. Dust masses and calculated relations (Pass/Residue) on the impactor stages

Impactor stage	Average aerodyn. Diameter	Calculated particles size	Separated dust mass	Pass	Residue
	dae [µm]	dg [µm]	[mg]	D [%]	[%]
Limit inhalable fraction^1)	100	-	-	100
A	32.40	13.12	327.40	51.28	48.72
B	15.80	6.40	180.56	24.41	75.59
C	8.13	3.29	100.75	9.42	90.58
D	4.06	1.64	39.18	3.59	96.41
E	2.04	0.83	13.94	1.51	98.49
F	0.99	0.40	6.31	0.58	99.42
G	0.47	0.19	2.98	0.13	99.87
< G^2)	< 0.47	< 0.19	0.88
Extrapolated total dust quantity ^3)			670.29 mg
Total dust mass, including impactor correction ^4)			672.01 mg
Total dustiness of the examined sample (incl. correction)			670.6651 mg/g

1) According EN 481 for the inhalable fraction exists an upper limit which is defined for the aerodynamic particle size of 100 µm. This corresponds with a mass limit of 100% for the total dust which can be inhaled (EN 481 chap.5 "agreement of conventions").

2)The dust mass is taken into account with the impactor stage "< G" (which was validated independently of the substance in earlier investigations) which is removed from the impactor with the exhaust air (mass extrapolation).

3)The "extrapolated total dust quantity" takes into account the dust masses separated at the individual impactor stages (without mass of stage "< G"). The dust masses separated at the individual impactor stages are evaluated with experimentally determined correction factors, taking into account the various separating strengths of the impactor stages (manufacturer 's specifications).

4)The "total dust mass including impactor correction" is the total mass from impactor stage A to G plus the extrapolated mass from stage "< G".

Table 2. Characteristics data of the frequency distribution of the inhalable fine dust

Particle size	Residue	Average particle size	Slope of CPSD
dae [µm]	[%]	dae av. [µm]	D'
0.47	99.87	0.73	0.85
0.99	99.42	1.52	0.89
2.04	98.49	3.05	1.03
4.06	96.41	6.10	1.43
8.13	90.58	11.97	1.95
15.80	75.59	24.10	1.62
32.40	48.72	49.20	0.80
66.00	21.83	83.00
100.00	0.00

Table 3. Dustiness values of the test item sample

Quantity of substance used	1.002 g	Relative amounts of used quantity	Relative amounts of the whole fraction
Total dust mass in impactor	672.01 mg
Mass Median Aerodynamic Diameter (MMAD)*	31.4 µm
Geometric Standard Deviation (GSD)*	2.5 µm
Total dustiness, whole fraction	670.6651 mg/g
Dustiness, inhalable fraction	413.4513 mg/g	41.35%	61.65%
Dustiness, thoracic fraction	119.8436 mg/g	11.98%	17.87%
Dustiness, alveolar fraction	29.0746 mg/g	2.91%	4.34%

*: Median of the distribution of airborne particle mass with respect to the aerodynamic diameter. MMAD is one of the metrics most widely adopted as a single number descriptor of aerodynamic particle-size distribution. MMADs are usually accompanied by the geometric standard deviation (GSD) which characterizes the variability of the particle size distribution. The diameter that divides the mass distribution of an aerosol in half [P.A. Baron, K. Willecke; Aerosol Measurement, 2005].

Determining the humidity of the substance

The humidity of the substance mesured by drying a sample in a furnace in accordance with DIN18121-1 was 2.48%.

Applicant's summary and conclusion

Conclusions:

The most important information resulting from the determination of the dustiness is that the respirable fraction represents 2.91 % of used quantity of the substance under the modified Heubach procedure.
According to EN 15051-2, the dustiness of the sample is allocated to category "high".

Executive summary:

The dustiness of a sample of Cerium dioxide and also the different dust fractions were determined in a non-GLP compliant study in accordance with DIN 55992 -1:2006, DIN EN 481 and DIN 18121-1 methods using the Heubach procedure modified by the laboratory DMT.

ln the process, the substance sample was mechanically stressed in a rotating drum (dust generation device), and both the dust already contained in this sample and the dust generated due to abrasion were removed from the dust generation device by an air current. The proportion of dust separated and considered as dust with the ability to become airborne was fed into a seven-stage cascade impactor connected to the dust generation device. Particle size classification was conducted by subsequent weighing of the respective dust masses deposited on the individual cascade stages reflecting certain particle size ranges.

The "total dustiness" value was determined as the ratio of the mass of removed dust to the total sample mass initially weighed in. Subsequently, the dustiness values for the inhalable, thoracic and alveolar fractions according to DIN EN 481 were determined.

Total dustiness [mg/g]	670.67
Inhalable fraction [mg/g]	413.45 (41.35%)
Thoracic fraction [mg/g]	119.84 (11.98%)
Respirable fraction [mg/g]	29.07 (2.91%)
Mass Median Aerodynamic Diameter (MMAD) [µm]	31.40
Geometric Standard Deviation (GSD) [µm]	2.50

As a conclusion, the most important information resulting from the determination of the dustiness is that the respirable fraction represent 2.91 % of used quantity of the substance under the modified Heubach procedure. According to EN 15051-2, the dustiness of the sample is allocated to category "high".