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Particle size distribution (Granulometry)

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Endpoint:
particle size distribution (granulometry)
Remarks:
dustiness
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
DIN 55992-1 (Determination of a parameter for the dust formation of pigments and extenders - Part 1: Rotation method)
Deviations:
yes
Remarks:
please see below
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 feed of 20L/min via the coarse dust seperator needed to supply the cascade impactor with 40L/min air current as specified in the manufacturer´s specifications.

The calculation report: Grewe, 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:
no
Type of method:
rotating drum method
Remarks:
seven stage cascade impactor is connected to a heubach dust meter
Type of distribution:
volumetric distribution
Remarks on result:
other: p1: 16.4 %, MMAD1 = 5.60 µm, GSD = 1.93; p2: 83.6 %, MMAD2 = 30.25 µm, GSD2 = 1.39
Remarks on result:
not measured/tested

Dustiness (airborne fraction): total: 22.67 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 bimodal lognormal distribution to the data by standard non-linear regression procedure. As a result, the MMAD and GSD are calculable and reported (p1: 16.4 %, MMAD1 = 5.60 µm, GSD = 1.93; p2: 83.6 %, MMAD2 = 30.25µm, GSD2 = 1.39). 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): 50.73%

Tracheobronchial (TB): 0.34%

Pulmonary (PU): 0.85%

Conclusions:
Total Dustiness (airborne fraction): 22.67 mg/g (experimental result, DMT Report).

Mass median aerodynamic diamaters (bi-modal distribution) of airborne fraction: MMAD1 = 5.60 µm (16.4 %) , MMAD2 = 30.25 µm (83.6 %) (distribution fitted to cascade impactor data, percentale in parentheses indicates weighting factor).

Geometric standard deviation of MMAD: GSD1 = 1.93, GSD 2 = 1.39.

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 50.73 %
Tracheobronchial (TB): 0.34 %
Pulmonary (PU): 0.85 %
Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-04-20
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: European Commission Regulation (EC) No. 440/2008
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:
D10
Mean:
0.6 µm
St. dev.:
0.01
Percentile:
D50
Mean:
3.2 µm
St. dev.:
0.11
Percentile:
D90
Mean:
8.9 µm
St. dev.:
0.2
Conclusions:
The median particle size D50 of the test items deduced from the particle size distribution is 3.2 µm.
The particle size D10 of the test items deduced from the particle size distribution is 0.6 µm.
The particle size D90 of the test items deduced from the particle size distributions is 8.9 µm.

Description of key information

The following parameters have been determined with a representative sample:

Median particle size (laser diffraction method): D50 = 3.2 µm

Mass median aerodynamic diameters of airborne fraction (rotating drum method, bi-modal distribution fitted to cascade impactor data): MMAD1 = 5.60 µm (16.4 %) , MMAD2 = 30.25 µm (83.6 %) (percentage in parentheses indicates weighting factor of bimodal distribution).

Additional information