The European Chemicals Agency (ECHA) has begun a public consultation on a harmonized classification and labeling (CLH) proposal for multi-walled carbon tubes (synthetic graphite in tubular shape) with a geometric tube diameter range ≥ 30 nanometers (nm) to 3:1, including multi-walled carbon nanotubes (MWC(N)T). The dossier submitted by Germany’s Federal Institute for Occupational Safety and Health (BAuA) states that the proposal comprises MWCTs that fulfill the European Union’s (EU) recommendation for a definition of nanomaterial and that, in line with the EU definition, have one external dimension (the diameter) in the size range 1 – 100 nm. The proposal extends the applicability domain of the CLH proposal to MWCTs with a diameter up to 3 μm, however, “as it is expected according to the fibre pathogenicity paradigm that MWCT[s] with diameters fitting into the respirable range will possess similar fibre-like properties.” The dossier notes that it is not known if MWCTs beyond a diameter range of > 200 nm (regarding the constituting particle) are manufactured. The proposal is based on the observation that fibers of high-diameter MWCTs (≥ 30 nm) “have equivalent potential with asbestos and asbestiform fibres and thus is consistent with the ‘fibre pathogenicity paradigm’ (Donaldson et al., 2010, 2013).” According to the dossier, low-diameter MWCNTs (

Carc. 1B, H350i

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The hazard classes open for comment are carcinogenicity and specific target organ toxicity — repeated exposure. Comments are due September 3, 2021.