Dichromium nitride

Acute Toxicity: inhalation

Administrative data

Endpoint:

acute toxicity: inhalation

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

the study does not need to be conducted because exposure of humans via inhalation is not likely taking into account the vapour pressure of the substance and/or the possibility of exposure to aerosols, particles or droplets of an inhalable size

Cross-reference

Reason / purpose for cross-reference:

data waiving: supporting information

Reference

1) Cr2N 10µm

Particle size distribution (PSD):

D (v, 0.1) = 0.98 μm

D (v, 0.5) = 1.98 μm

D (v, 0.9) = 3.38 μm

Dustiness:

- total dustiness (airborne fraction): 12.61 mg/g

Mass median aerodynamic diameter:

- p1 (58.8 %): MMAD1 = 3.70 µm, GSD1 = 1.59

- p2 (41.2 %): MMAD2 = 100 µm, GSD2 = 18.59

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

Head (ET): 65.16 %

Tracheobronchial (TB): 1.88 %

Pulmonary (PU): 5.32 %

 

2) Cr2N:

 

Particle size distribution (PSD)

D (v, 0.5) = 2.59 μm

Dustiness:

- total dustiness (airborne fraction): 4.75 mg/g

Mass median aerodynamic diameter:

- p1 (70.6 %): MMAD1 = 4.15 µm, GSD1 = 1.83

- p2 (29.4 %): MMAD2 = 22.92 µm, GSD2 = 20.00

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

Head (ET): 67.95 %

Tracheobronchial (TB): 2.52 %

Pulmonary (PU): 7.21 %

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.

It is noted that any agglomerates of particles normally existing in the powder were destroyed by (i) the contact with water, (ii) the ultrasonic treatment and (iii) the mechanical stirring. Such agitation of the dry powder 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 bimodal.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 the inhalable material (airborne fraction of ~ 1%) could deposit in the alveoli of the human lung.