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Physical & Chemical properties

Particle size distribution (Granulometry)

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Description of key information

(i) Total dustiness zinc selenite(airborne fraction): 151.82 mg/g (experimental result, DMT Report). 
MMAD (bimodal distribution) of airborne fraction: MMAD = 13.13 µm (p1=23.4 %) and MMAD = 26.17 µm (p2=76.6 %) (distribution fitted to cascade impactor data, percentage in parentheses indicates weighting factor).
GSD of MMAD: 3.95 (p1=23.4 %) and GSD = 1.79 (p2=76.6 %)
Fractional deposition in human respiratory tract (MPPD model, based on calculated MMAD):
Head (ET): 52.55 %; Tracheobronchial (TB): 0.40 %; Pulmonary (PU): 0.83 %
(ii) Physical particle size: The average of the median physical particle size D50 is 17.4 µm (experimental result, laser diffraction, Krack, 2010)

Additional information

The test data on particle size (GLP, OECD guideline conform) is reliable without restrictions (Krack, 2010). Test procedure for the dustiness testing in accordance with national standards DIN 55992-1:2006 ("Determination of a parameter for the dust formation of pigments and extenders - Part 1: Rotation method"), modified Heubach method is reliable without restrictions. This Parr, 2010; Grewe, 2010 - study considers the airborne fraction of zinc selenite, which is exposure-related and relevant for workplace conditions. In the other study (Krack, 2010), the airborne fraction of zinc selenite was not determined, but the total of the substance used for particle size analysis. This is not exposure-related and not relevant for workplace conditions.