Hematite, chromium green black

Particle size distribution (Granulometry)

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

particle size distribution (granulometry)

Remarks:

dustiness

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2009-09-28

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:

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 seperator needed to supply the cascade impactor with 40 L/min air current as specified in the manufacturer´s specifications.

The calculation report: EBRC (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

Remarks:

Heubach-Dust-Meter connected to a cascade impactor

Type of distribution:

volumetric distribution

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: Kept dry in closed containers

Mass median aerodynamic diameter:

11.92 µm

Geometric standard deviation:

4.1

Percentile:

D50

Remarks on result:

not measured/tested

Dustiness (airborne fraction): total: 41.02 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 by standard a non-linear regression procedures to the data. As a result, the MMAD and GSD are calculable and reported (MMAD = 11.92 µm, GSD = 4.10). 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): 55.2 %

Tracheobronchial (TB): 1.4 %

Pulmonary (PU): 4.0 %

Conclusions:

Total Dustiness (airborne fraction): 41.02 mg/g (experimental results, DMT Report).

Mass median aerodynamic diamater of airborne fraction: MMAD = 11.92 µm (distribution fitted to cascade impactor data).
Geometric standard deviation of MMAD: GSD = 4.10.

Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 55.2 %
Tracheobronchial (TB): 1.4 %
Pulmonary (PU): 4.0 %

A suitable method for determining the PSD of a dry powder to assess the inhalation potential of airborne dust resulting from the handling of that powder is cascade impactor testing (Dustiness). During the cascade impactor testing, the material gets moderately agitated in a rotating drum (to simulate agitation during typical occupational powder handling activities). A constant airstream directs any generated airborne dust to a cascade impactor in which the particles and their agglomerates get separated according to their size.
The aerodynamic PSD is described as being monomodal. With the given parameters it is possible to calculate the cumulated mass percentage of particles at or below 4 µm. This fraction does however not indicate how much is deposited in the deep lung if such aerosol would be inhaled. Instead, the fractional deposition in the human respiratory tract was calculated using the MPPD model.
Thus, only a sub-fraction of 4.00 % particles could deposit in the alveoli of the human lung.

Reference 2

Endpoint:

particle size distribution (granulometry)

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Missing data: – Expected percent change of reported values in the future (e.g. variations between production batches) – Lot number – Temperature, pH – Stoke's (effective hydrodynamic) radius Rs distribution for 2 ≤ Rs ≤ 200 μm – Mean value and approximate "area" (percent) of any resolvable peaks in Rs distribution – Percent of particles with Rs ≤ 2 μm – Percent of particles with Rs ≥ 200 μm

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 110 (Particle Size Distribution / Fibre Length and Diameter Distributions - Method A: Particle Size Distribution (effective hydrodynamic radius)

Deviations:

yes

Remarks:

please refer to the field "Rational to reliability incl. deficiencies" above

GLP compliance:

no

Type of method:

Laser scattering/diffraction

Type of distribution:

volumetric distribution

Remarks on result:

not measured/tested

Key result

Percentile:

D10

Mean:

1.4 µm

Remarks on result:

other: no data for St.dev.

Key result

Percentile:

D50

Mean:

3.8 µm

Remarks on result:

other: no data for St.dev.

Key result

Percentile:

D90

Mean:

8.7 µm

Remarks on result:

other: no data for St.dev.

The parameters d₉₀, d₅₀ and d₁₀ are the cut off particle size below which 90 %, 50 % and 10 % of the total particle volume lies. The parameter d_v and d_s are respectively the volume mean diameter and the surface area mean diameter.

All values are calculated assuming that the particles are spherical.

d₁₀ = 1.4 µm

d₅₀ = 3.8 µm

d₉₀ = 8.7 µm

d_v = 4.5 µm

d_s = 2.7 µm

Conclusions:

The particle size distribution of the pigment Hematite, chromium green black was determined using a MALVERN laser diffraction equipment. The size distribution was calculated using the MIE theory in order to interpret the light scattering signal collected by the detectors.

The following values were calculated assuming that the particles are spherical:
d10 = 1.4 µm
d50 = 3.8 µm
d90 = 8.7 µm

Description of key information

Dustiness:

Total Dustiness (airborne fraction): 41.02 mg/g (experimental results, DMT Report).

Mass median aerodynamic diamater of airborne fraction: MMAD = 11.92 µm (distribution fitted to cascade impactor data).

Geometric standard deviation of MMAD: GSD = 4.10.

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

Head (ET): 55.2 %

Tracheobronchial (TB): 1.4 %

Pulmonary (PU): 4.0 %

The particle size distribution of the pigment

Hematite, chromium green black was determined using a MALVERN laser diffraction equipment. The size distribution was calculated using the MIE theory in order to interpret the light scattering signal collected by the detectors.

The following values were calculated assuming that the particles are spherical:

d10 = 1.4 µm

d50 = 3.8 µm

d90 = 8.7 µm

Additional information

The so-called physical particle size distribution (PSD) was obtained by the laser diffraction method in a wet dispersion after ultrasonic treatment for individualisation of the particles and further mechanical stirring. The particle size of the individualised particles is provided.

Any agglomerates of particles normally existing in the pigment powder were destroyed by (i) the contact with water, (ii) the ultrasonic treatment and (iii) the mechanical stirring. Such agitation of the dry pigment does however not occur under intended and foreseeable manufacture and use conditions and is therefore not suitable to deduce the likelihood of inhalation exposure under workplace conditions.

A suitable method for determining the PSD of a dry powder to assess the inhalation potential of airborne dust resulting from the handling of that powder is cascade impactor testing (Dustiness). During the cascade impactor testing, the material gets moderately agitated in a rotating drum (to simulate agitation during typical occupational powder handling activities). A constant airstream directs any generated airborne dust to a cascade impactor in which the particles and their agglomerates get separated according to their size.

The aerodynamic PSD is described as being monomodal. With the given parameters it is possible to calculate the cumulated mass percentage of particles at or below 4 µm. This fraction does however not indicate how much is deposited in the deep lung if such aerosol would be inhaled. Instead, the fractional deposition in the human respiratory tract was calculated using the MPPD model.

Thus, only a sub-fraction of 4.00 % particles could deposit in the alveoli of the human lung.