Zinc oxide

Nanomaterial dustiness

Administrative data

Endpoint:

nanomaterial dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2021

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

The study was not performed under GLP conditions.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: EN_17199-4

Version / remarks:

2019 version

Principles of method if other than guideline:

The setup of the “Small Rotating Drum” (SRD) is entirely standardised by (EN_17199-4 2019). “Dustiness” is defined as the ability of a material (e.g. loose, granulated, or pelletized powder) to generate dust during agitation. Dustiness is important for the assessment of the occupational exposure by powders. Standardised methods to assess dustiness are documented in EN 15051 and are currently being revised to include nanomaterials and advanced methodology in the CEN Dustinano project. Here we implemented and performed tests in a Small Rotating Drum (SRD) according to EN17199:2019.

GLP compliance:

no

Type of method:

rotating cylinder

Remarks:

standardised Small Rotating Drum (SRD)

Details on methods and data evaluation:

The powder is loaded into the drum and is evenly spread on one of the lamellae that
lift the powder during rotation. One “conditioning” run coats the inner surface of the drum, and is not used for data acquisition (Schneider et al. 2008).

The mass-based dustiness index is determined gravimetrically. The filter in the cyclone is measured before and after the rotation of the drum. The results are given as average of the triplicate, and its standard deviation. All measurements were performed as triplicate.

Sampling:

Measurements were performed for each replicate with 6g powder, which had been left to equilibrate to the air humidity overnight.

Test material

Test material information

Constituent 1

Reference substance name:

Zinc oxide

EC Number:

215-222-5

EC Name:

Zinc oxide

Cas Number:

1314-13-2

Molecular formula:

ZnO

IUPAC Name:

oxozinc

Test material form:

solid: nanoform, surface-treated

Remarks:

hydrophobic

Details on test material:

- Particle size distribution: D10 is 10.4 nm ; D50 is 18.3 nm ; D90 is 29.5 nm
- Shape of particles: spheroidal
- Surface area of particles: ca. 10 - 40 m2/g
- Crystal structure: hexagonal zincite crystalline phase
- Coating: hydrophobic coating
- Dustiness: 20 mg/kg (respirable mass index)
- Dissolution rate (kmin): 97.5 ng/cm2/h

Data gathering

Instruments:

A “Small Rotating Drum” (SRD) was used to determine dustiness, as described by the standardised EN_17199-4 2019.
The number-based dustiness index is determined by the Condensation Particle Counter (CPC).

Calibration:

not specified

Reproducibility:

All measurements were performed as triplicate.

Results and discussion

Dustiness index

Dustiness index 1

Mean:

20 mg/kg

St. dev.:

4.1 mg/kg

Remarks on result:

other: respirable mass index

Dustiness index 2

Mean:

97 000 other: /mg

St. dev.:

5 300 other: /mg

Remarks on result:

other: number based index

Any other information on results incl. tables

Size distribution not determined: if less than 0.2 mg deposit overall on all MOUDI stages, then no size distribution can be given due to the limit of gravimetric determination. 

Applicant's summary and conclusion

Conclusions:

The respirable mass-based dustiness of T0410 is 20 +/ 4.1 mg/kg.

Executive summary:

The respirable mass-based dustiness places most of the ZnO materials into the category of “low” or “moderate” dustiness. There are some materials in the “very low” dustiness, and one in “high” dustiness. There is no direct correlation between the dustiness and either the size of the materials (as determined by TEM) or their coating, but there is a trend of smaller particle sizes inducing the more elevated dustiness. The number-based dustiness indices range from 2.7 10³/mg to 1.5 10⁶/mg. No categories are defined for the number-based index.
Most of the ZnO materials show substantial agglomeration in the aerosol with peak aerodynamic diameters between 1.8µm and 5.6µm, except for two cases with rather low agglomeration and a substantial fraction below 0.18µm.