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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
Study period:
2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
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 (2015)

The Multiple-Path Particle Dosimetry Model (MPPD, v2.11; ARA, 2009) 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:
other: Heubach dust meter connected to a cascade impactor
Type of distribution:
volumetric distribution
Mass median aerodynamic diameter:
20.44 µm
Geometric standard deviation:
2.65
Remarks on result:
not measured/tested
Remarks on result:
not measured/tested

Dustiness (airborne fraction): total: 126.32 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 monomodal lognormal distribution to the data by non-linear regression procedure. As a result, the MMAD and GSD are calculable and reported (MMAD = 20.44 µm, GSD = 2.65).

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): 55.61 %

Tracheobronchial (TB): 0.64 %

Pulmonary (PU): 0.79 %

Conclusions:
Total Dustiness (airborne fraction): 126.32 mg/g (experimental results, DMT Report).

Mass median aerodynamic diamater of airborne fraction: MMAD = 20.44 µm, GSD = 2.65

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 55.61 %
Tracheobronchial (TB): 0.64 %
Pulmonary (PU): 0.79 %
Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Reason / purpose:
reference to same study
Qualifier:
no guideline followed
Principles of method if other than guideline:
Particle size distribution was determined using a MALVERN laser diffraction equipment. In this equipment, the particles pass through a laser beam and the scattered light is collected by 52 detectors.
The size distribution was calculated using the MIE theory in order to interpret the light scattering signal collected by the detectors. The calculations were made considering the refractive index of the sample (1.92) and an absorption coefficient value of 0.01.
A wet dispersion of the sample was used. The powder was mixed with 1.8 g sodium hexametaphosphate and 0.4 g anhydrous sodium carbonate in 1 L water, which yielded a water suspension in which the sample was dispersed. A 5-minute ultrasonic bath was further applied in order to completely individualise the particles. Finally, the sample was mechanically stirred before it was fed into the instrument.
GLP compliance:
no
Type of method:
Laser scattering/diffraction
Type of distribution:
volumetric distribution
Percentile:
D10
Mean:
2.8 µm
Remarks on result:
other: No St.dev. was stated
Key result
Percentile:
D50
Mean:
11.9 µm
Remarks on result:
other: No St.dev. was stated
Percentile:
D90
Mean:
29.4 µm
Remarks on result:
other: No St.dev. was stated

All values are calculated assuming that the particles are spherical.

d50 = 11.9 µm

d90 = 29.4 µm

d10 = 2.8 µm

Conclusions:
Particle size distribution of the test item:
d50 = 11.9 µm
d90 = 29.4 µm
d10 = 2.8 µm
All values are calculated assuming that the particles are spherical.

Description of key information

Particle size analysis by laser diffraction (Mestre Beltrán, 2014)

d50 = 11.9 µm

d90 = 29.4 µm

d10 = 2.8 µm

(All values were calculated assuming that the particles are spherical)

Dustiness (Parr, Grewe, 2015)

Total Dustiness (airborne fraction): 126.32 mg/g (experimental results, DMT Report).

Mass median aerodynamic diamater of airborne fraction: MMAD = 20.44 µm, GSD = 2.65

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):

Head (ET): 55.61 %

Tracheobronchial (TB): 0.64 %

Pulmonary (PU): 0.79 %

Additional information