Silicate(2-), hexafluoro-, disodium, reaction products with lithium magnesium sodium silicate

Nanomaterial dustiness

Administrative data

Endpoint:

nanomaterial dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

December 2013

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Justification for type of information:

See Document "Laponite Analog justification-BL_6_30_2020.pdf" in Section 13.2 - Toxicokinetic assessment for Synthetic fluorohectorites for justification of read-across.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2015

Report date:

2015

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

other: Results from the site monitoring of a nanoclay powder bagging process

Deviations:

not applicable

Principles of method if other than guideline:

There is no guideline for this test

GLP compliance:

no

Other quality assurance:

other: ISO 9001:2015

Details on methods and data evaluation:

The objective of the visit to BYK Additives, formerly Rockwood additives was to monitor
airborne nanoparticles and their agglomerates during the packaging of a nanoclay powder
(Laponite) and to assess the controls used. In addition, this visit investigated the size of the
particles released when the clay Laponite was handled and whether submicron or <100 nm
nanoclay particles were present in the air.


In detail the following measurements were carried out:

1) measurement of particle number concentration in the range of 20 - 1000 nm
2) measurement of particle number concentration in six size channels ranging from 300 nm to >10,000 nm.
3) Analysis of particle type, morphology and degree of agglomeration by collecting air samples onto filters and electron microscope (EM) grids
4) measurement of the surface area of aerosol particles in the range of 10 - 1000 nm which would deposit in the air-exchange region of the lung

Additional measurements not included in the project-specific sampling protocol

5) Investigation the size of airborne particles released
6) Measurement particle number concentration in the of 10-1000 nm size range (long Differential Mobility Analyser) and provides size distribution information of airborne particles in 45 size channels
7) Measurement of aerodynamic particle-size distribution of airborne particles in 14 size channels and gives an indication of particle number concentrations in the 6 to 10,000 nm (10 μm) size range

Test material

Test material information

Constituent 1

Reference substance name:

Silicic acid, lithium magnesium sodium salt

EC Number:

258-476-2

EC Name:

Silicic acid, lithium magnesium sodium salt

Cas Number:

53320-86-8

Molecular formula:

Na0.7[Li0.3Mg5.5Si8O20(OH)4]

IUPAC Name:

Synthetic hectorite

Test material form:

solid: particulate/powder

Data gathering

Instruments:

P-trak (TSI Instruments Ltd) CPC
Met-One OPC
Electron Microscope (EM)
Aerotrak (AT) 9000 (TSI Instruments Ltd.)
Marple cascade impactor (series 290)
SMPS (Grimm, Aerosol Technik)
ELPI+ (Dekati Ltd)

Calibration:

The instrument was calibrated as required by the manufacturer in accordance with ISO 9001:2015

Reproducibility:

Multiple measurements were accomplished at each location.

Results and discussion

Dustiness index

Remarks on result:

not measured/tested

Remarks:

PLACEHOLDER

Any other information on results incl. tables

Below are listed the various measurements documented in the report. A detailed description and the results are disclosed in the attached report document. It should be noted that this study report is the draft study report. The study was carried out by The Health and Safety Executive (HSE) which is a UK government agency.

1) measurement of particle number concentration in the range of 20 - 1000 nm with

-P-trak (TSI Instruments Ltd) CPC

-Met-One OPC

-ELPI+ (Dekati Ltd)

-SMPS (Grimm, Aerosol Technik)

2) measurement of particle number concentration in six size channels ranging from 300 nm to >10,000 nm

3) Analysis of particle type, morphology and degree of agglomeration by collecting air samples onto filters and electron microscope (EM) grids

4) measurement of the surface area of aerosol particles in the range of 10 - 1000 nm which would deposit in the air-exchange region of the lung

Additional measurements not included in the project-specific sampling protocol

5) Investigation the size of airborne particles released

6) Measurement particle number concentration in the of 10-1000 nm size range (long Differential Mobility Analyser) and provides size distribution information of airborne particles in 45 size channels

7) Measurement of aerodynamic particle-size distribution of airborne particles in 14 size channels and gives an indication of particle number concentrations in the 6 to 10,000 nm (10 μm) size range

Applicant's summary and conclusion

Conclusions:

This visit on 17th December 2013 and 18th December monitored the bagging of Laponite powder
into one tonne FIBC container, the subdividing and packing of this powder into 25 kg boxes and
the cleaning of the areas around the boxing/packing activities using a vacuum cleaner and a
sweeping brush.
A LEV, fixed captor hood, was located on the semi-automatic packaging line. This hood was
not effective at capturing the dust generated during the packing process. A re-design of the hood
and system would be beneficial. It was observed that some ductwork above the packaging line
where the hopper fed into the system had a damaged/worn connection, which was leaking dust.
This defect was pointed out to the Safety Officer by the HSL personnel on-site with the
suggestion that repairing this would reduce the Laponite dust levels in the vicinity of the
packaging line.
The P-traks and Aerotrak data suggest that particles, which were released from the
boxing/packing process, were not particles of a size range between 10 and 1,000 nm. A number
of peaks and increases in particle number concentration above the Met-One and ELPI+ graph
baseline were observed for all size channels greater than 500 / 1,000 nm confirming a release of
airborne Laponite agglomerates in the workplace. The ELPI+ number-based size distribution
was dominated by particles less than 600nm (mainly from ultrafine particles of outdoor and
diesel origin) and the mass-based size distribution by particles greater than 1 μm. The massbased
size distributions from the Marple cascade impactors were dominated by particles greater
than 1 / 2 μm. The off-line TEM analysis provided evidence for release of agglomerated
Laponite particles. The Laponite particles collected were mostly agglomerates (or aggregates) of
size less than 4 / 5 μm but greater than 500 / 1,000 nm. A small number of larger agglomerates
were also observed by TEM but primary or small Laponite particles were not identified. Other
particles observed in significant quantity were agglomerates of typical carbon/diesel particles,
most of them of size less than 500 / 1,000 nm.
The bagging process in one tonne FIBCs did not have LEV. This process was fully automated
and enclosed. The Met-One and ELPI+ data suggested that the releases of particles from the
large bagging process were much lower than those from the packing of powder in 25 kg boxes.
The cleaning activities also resulted in much lower emission of particles compared with the
packing/boxing activity.
The workers wore JSP FFP2 disposable masks, latex gloves and reusable jackets and trousers.
The RPE worn was not face-fit tested to the wearer and was worn for longer than is
recommended in HSE guidance. Also, RPE only protects the wearer and not others in the
vicinity of the work. The powdered latex gloves used put the wearer at risk of skin allergies and
asthma. A suitable alternative would be nitrile. The COSHH assessments received during the
visit needed a little more detail including how control measures are examined, tested and
maintained.
The company considers Laponite as nuisance dust. There are currently no UK statutory
workplace exposure limits (WELs) specifically for nanomaterials.