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Particle size distribution (Granulometry)

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Description of key information

The mass median diameter was calculated to be 0.076 mm (= 76 µm).  The calculated amount of material in the size fraction < 10 µm is < 0.1%, the amount in the 4 µm size fraction << 0.1%.

Additional information

In the non-GLP Klimisch 1 study from Bütfering (2013) the particle size distribution of Butanedioic acid, sulfo-, 4-C12-14-alkyl esters, disodium salts was determined using Laser Scattering Particle Size Distribution Analyser Partica LA-950V2. The mass median aerodynamic diameter (MMAD) of the test item is calculated by 76,0 µm. This study is considered relevant for the risk assessment.

The non-GLP Klimisch 2 study from Siebke und Tiedge (2009) determined the size distribution of [trade name] on a Retsch sieving machine by using in total 13 sieves with mesh sizes ranging from 0.032 to 0.500 mm (= 32 to 500 µm). Details to the method other than the mesh sizes of the DIN sieves were not provided.

 In the smallest fraction , i.e., 0-32 µm 8% of the total mass were found. Sixty-four percent (64%) of the total mass was in the size fraction < 100 µm.

For the determination of the mass median diameter and the inhalation potential of the substance , i.e., < 10 and < 4 µm, a linear fit was performed between the probit transformed percent of cumulative mass and the log10 transformed size class. The mass median diameter (50% of the total mass) was calculated to be 0.078 mm (= 78 µm). As mentioned before, the size fraction < 100 µm corresponds to 64% of the total mass. The calculated amount of material in the size fraction < 10 µm is < 0.1%, the amount in the 4 µm size fraction is << 0.1%.

Despite the shortcomings in providing experimental details, the results are considered to be acceptable for the risk assessment.

Both studies indicate that the MMD is 76 and 78 µm. Hence, both studies confirm the obtained results. For the risk assessment, the lower value will be used, i.e., 76 µm.