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Particle size distribution (Granulometry)

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Reference
Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2014
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study with acceptable restrictions
Remarks:
The study was conducted according to EU guideline, with minor deviations. Test substance is adequately characterised with its purity. However, as a single measurement was performed, intra and inter batch variation were not assessed. Therefore validity applies with restrictions.
Qualifier:
according to
Guideline:
other: EUR 20268 EN: Guidance Document on the Determination of Particle Size Distribution, Fibre Length and Diameter Distribution of chemical substances (European Commission, 2002)
Deviations:
yes
Remarks:
observation with binocular; no preliminary screening test at 100 µm
Principles of method if other than guideline:
Laser diffraction
GLP compliance:
no
Type of method:
Laser scattering/diffraction
Type of particle tested:
primary particle
Type of distribution:
volumetric distribution
Percentile:
D10
Mean:
9.3 µm
Remarks on result:
other: no data on SD
Percentile:
D50
Mean:
34 µm
Remarks on result:
other: no data on SD
Percentile:
D90
Mean:
88 µm
Remarks on result:
other: no data on SD
Size:
< 515 µm
Distribution:
100 %
Remarks on result:
other: sample as supplied
Size:
< 105 µm
Distribution:
94 %
Remarks on result:
other: sample as supplied
Size:
< 11 µm
Distribution:
12 %
Remarks on result:
other: sample as supplied
Size:
< 4.5 µm
Distribution:
4.8 %
Remarks on result:
other: sample as supplied

Particle size distribution

The results of the sample show a Gaussian-type distribution, with a median size (D50) of 34 µm.

For the thresholds relevant to inhalation potential, results below were not corrected (no pre-sieving therefore total sample distribution), and assuming %v and %w are similar:
Inhalable fraction (< 105 µm):
    94 %
Thoracic fraction (< 11 µm):
       12 %
Respirable fraction (< 4.5 µm):
     4.8 %

A threshold of 500 µm is generally assumed to be of concern for dust explosion potential; the corresponding fraction (< 515 µm) accounts for 100%.

Conclusions:
The test substance contains a fraction of particles fine enough to be inhaled and reach the thoracic fraction.
Dust explosion potential should be considered.
Executive summary:

Following guidance EUR 20268 EN, the test substance was first examined under microscope, and described as crystalline needles, without clusters.

The particle size was measured with a laser diffraction granulometer, in air. For the single sample tested, the distribution was Gaussian, with a median diameter of 34 µm.

With regard to inhalation potential, about 94% of total particles are smaller than 105 µm, and about 12% could reach the thoracic fraction (<11 µm).

Fine particles relevant to dust explosion hazard (<515 µm) account for 100%.

Description of key information

Median diameter = 34 µm

Thoracic fraction (<11µm) = 12%.

Dust particles (<515µm) = 100% (dust explosion potential)

Additional information

A reliable experimental study, conducted according to a recognized EU guideline, is available. Despite restrictions due to single measurement, it is considered as a key study.