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Physical & Chemical properties

Particle size distribution (Granulometry)

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Administrative data

Endpoint:
particle size distribution (granulometry)
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2010-05 to 2010-08
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
test procedure in accordance with generally accepted scientific standards and described in sufficient detail

Data source

Referenceopen allclose all

Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010
Reference Type:
study report
Title:
Unnamed
Year:
2010
Report Date:
2010

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
DIN 55992-1 (Determination of a parameter for the dust formation of pigments and extenders - Part 1: Rotation method)
Deviations:
yes
Remarks:
A seven stage cascade impactor is connected to a Heubach dust meter
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 (2009)
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
Type of distribution:
volumetric distribution

Test material

Reference
Name:
Unnamed
Type:
Constituent
Details on test material:
- Name of test material (as cited in study report): Cobalt powder (half micron)
- Physical state: odourless gray (very fine powder)
- Storage condition of test material: Keep container tightly closed. Keep container in a well-ventilated area.

Results and discussion

Particle size
Percentile:
D50
Remarks on result:
other: Migrated from fields under 'Mass median diameter' as D50 percentile. No source field for Standard deviation.

Any other information on results incl. tables

Dustiness (airborne fraction): total: 31.29 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 (MMAD1 = 3.00 µm and MMAD2 = 25.66 µm, GSD1 = 1.46 and GSD2 = 5.87). 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): 50.2%

Tracheobronchial (TB): 1.5%

Pulmonary (PU): 3.2%

Applicant's summary and conclusion

Conclusions:
Cobalt powder half micron

Total Dustiness (airborne fraction): 31.29 mg/g (experimental results, DMT Report).

Mass median aerodynamic diamater of airborne fraction: MMAD1 = 3.00 µm and MMAD2 = 25.66 µm (distribution fitted to cascade impactor data).
Geometric standard deviation of MMAD: GSD1 = 1.46 and GSD2 = 5.87

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 50.2%
Tracheobronchial (TB): 1.5%
Pulmonary (PU): 3.2%