No classification for SiC products (CAS 409-21-2)

Since March 2022, silicon carbide (SiC) fibres are classified as carcinogenic category 1B (Carc. 1B). This classification does not concern SiC crude and grains (CAS 409-21-2). Customers of SiCMa members buying SiC crude and grains are therefore not affected by the new classification of SiC fibres.

SiC crude and grains has been extensively tested for the REACH registration dossier and is clearly classified as non-hazardous material.

The new classification applies only to SiC fibres and cleavage fragments which fall within the World Health Organization (WHO) definition of a ‘fibre’ . The WHO defines ‘fibres’ as particles with a length of >5µm, a diameter of <3µm and an aspect ratio (length/diameter) of >3:1.

The classification is based on scientific studies for whiskers. Nevertheless, RAC took a decision for all particles falling under the WHO definition, irrespective whether or not they showed adverse effects. SiCMa disagrees with this decision from a scientific perspective. Scientific studies undertaken by SiCMa and other publicly available information indicate that a differentiated view on SiC fibres is required. None of the scientific studies, to our knowledge, showed evidence that cleavage fragments and short fibres have carcinogenic effects. Only very long fibres, so-called ‘whiskers’ (diameter <1µm, length >10µm; aspect ratio >10) which are produced in a different way than SiC crude and grains may be considered carcinogenic.

Unfortunately, a source of confusion might be that SiC fibres have the same CAS 409-21-2 as SiC crude and grains, although, this is a completely different material.