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Particle size distribution (Granulometry)

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Inhalable fraction

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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.

 

Acid Red 097:1 is a multiconstituent substance composed by the acidic and the sodium salt forms of the same structure (62.1 % and 11.34 % of the substance respectively). The test was performed on the sodium salt of the Acid Red 079:1.

The tested substance presented a granulometry of 16.891 µm (D50 after 2 minutes of ultrasonic) 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 (16.891 µm).