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Particle size distribution (Granulometry)

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Description of key information

Inhalable fraction (MMD ca. 20.797 µm)

Additional information

Granulometry is of considerable importance for the toxic properties of a substance as it influences aspects such as the route of exposure of humans and toxicity by inhalation; the choice of route of administration for animal testing; the efficiency of uptake in an organism and the distribution in the environment.

For this purpose fractions can be divided in:

Inhalable fraction(the mass fraction of particles that can be inhaled by nose and mouth. Particles >100 μm are not included in the inhalable convention;

Thoracic fraction(the mass fraction of the inhaled particles that passes the larynx). The convention for thoracic fraction sets that 50% of the particles in air with an aerodynamic diameter of 10 μm belong to the thoracic fraction;

Respirable fraction(the mass fraction of the inhaled particles that reaches the alveoli) The convention for respirable fraction sets that 50% of particles with an aerodynamic diameter of 4 μm belong to the respirable fraction.


Direct Blue 080:1 is a multiconstituent substance composed by the acidic and the sodium salt forms of the same structure (58.44 % and 13.55 % of the substance respectively). The test was performed on the sodium salt of the Direct Blue 080:1.

The tested substance presented a granulometry of 20.797 µm (D50 after 2 minutes of ultrasonic treatement) that can be considered as inhalable fraction.

Considering the great similarity of the molecules, the composition of the substance and the fact that the substance is produced in the same production plant with the same production process, the Mass Median Diameter of the multiconstituent substance is expected to be the same of the sodium salt (20.797 µm).