Sodium dithionite

Particle size distribution (Granulometry)

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-06-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions)

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: CIPAC MT 187: Particle Size Analysis by Laser Diffraction

Deviations:

no

Qualifier:

according to guideline

Guideline:

other: ISO13320-1: Particle Size Analysis - Laser Diffraction Methods

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2009-10-29

Type of method:

Laser scattering/diffraction

Type of distribution:

volumetric distribution

Remarks on result:

not measured/tested

Percentile:

D50

Mean:

107.1 µm

St. dev.:

2

Percentile:

D10

Mean:

13.9 µm

St. dev.:

0.88

Percentile:

D90

Mean:

314.41 µm

St. dev.:

1.48

Conclusions:

The median particle size L50 of the test items deduced from the particle size distributions is 107.1 µm.
The particle size L10 of the test items deduced from the particle size distributions is 13.9 µm.
The particle size L90 of the test items deduced from the particle size distributions is 314.4 µm.

Reference 2

Endpoint:

particle size distribution (granulometry)

Remarks:

dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2010-06 to 2010-08

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Heubach-dust-meter connected to a cascade impactor

Qualifier:

according to guideline

Guideline:

DIN 55992-1 (Determination of a parameter for the dust formation of pigments and extenders - Part 1: Rotation method)

Version / remarks:

2006

Deviations:

yes

Remarks:

Heubach-Dust-Meter connected to a cascade impactor

Principles of method if other than guideline:

The Heubach dust meter is modified in a way that a seven stage cascade impactor is connected to the system. This involves an additional air fed of 20 L/min via the coarse dust separator needed to supply the cascade impactor with 40 L/min air current as specified in the manufacturer’s specificcations.
The calculation report: Grewe, T (2010)
The Multiple-Path Particle Dosimetry Model (MPPD, v2.0; CIIT, 2006) was used to predict this fractional deposition behaviour for workers.
The model algorithms calculate the deposition (and clearance) of mono-disperse and polydisperse aerosols in the respiratory tract for particles ranging from ultra-fine (0.01 microns) to coarse (20 microns) sizes. Within each airway, deposition is calculated using theoretically derived efficiencies for deposition by diffusion, sedimentation and impaction within the airway or airway bifurcation. Filtration of aerosols by the head is determined using empirical efficiency functions.

GLP compliance:

not specified

Type of method:

other: Heubach-dust-meter connected to a cascade impactor

Type of distribution:

volumetric distribution

Mass median aerodynamic diameter:

24.46 µm

Geometric standard deviation:

1.85

Remarks on result:

not measured/tested

Remarks on result:

not measured/tested

Dustiness (airborne fraction): total: 182.353 mg/g.

In the original study report by DMT, a calculation of the mass median diameter was not conducted. Since the deposited fractions were provided for each of the cascade impactor stages, it was possible to fit a mono modal lognormal distribution to the data by standard non-linear regression procedure. As a result, the MMAD and GSD are calculable and reported (MMAD = 24.46 µm, GSD = 1.85). As the cascade impactor already takes aerodynamic characteristics of the particles into account, the reported mass median diameter can be interpreted as the mass median aerodynamic diameter.

This figure and the corresponding GSD were used as distribution parameters for the MPPD model enabling an estimation of deposited dust fractions in the human respiratory tract: These fractions were estimated as follows:

Head (ET): 54.8 %

Tracheobronchial (TB): 0.2 %

Pulmonary (PU): 0.2 %

Conclusions:

Total Dustiness (airborne fraction): 182.35 mg/g (DMT)

Mass median aerodynamic diamaters (mono-modal distribution) of airborne fraction: MMAD = 24.46
Geometric standard deviation of MMAD: GSD = 1.85

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 54.8 %
Tracheobronchial (TB): 0.2 %
Pulmonary (PU): 0.2 %

Description of key information

The particle size of a representative sodium dithionite sample was determined to be:
D50 = 107.1 µm.
D10 = 13.9 µm
D90 = 314.4 µm

Dustiness and MMAD (GSD) of airborne material:
Dustiness: 182.35 mg/g; MMAD (GSD): 24.46 µm (1.85)

Head (ET): 54.8 %

Tracheobronchial (TB): 0.2 %

Pulmonary (PU): 0.2 %

Additional information

The particle size distribution of the test item was determined by laser diffraction (light scattering) according to OECD guideline 110.

The test item was tested as received and was analysed with the Master-Sizer 2000 (Version 5.12G) of Malvern Instruments with a dry powder feeder; measuring range was 0.02 to 2000 µm.

In addition to the physical particle size, the dustiness, i.e. the tendency of the materials to become airborne, has been determined with a representative sample using the modified Heubach method (in accordance withDIN 55992 -1:2006, Determination of a parameter for the dust formation of pigments and extenders – Part 1: Rotation method). In this modified method - in addition to the dustiness - the mass median aerodynamic diameter of the airborne particles has been determined using cascade impactor data. Further, the Multiple-Path Particle Dosimetry Model (MPPD, v2.0; CIIT, 2006) was used to predict fractional deposition behaviour of these particles in the human respiratory tract.