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 micrometers (μm) and a length ≥ 5 μm and aspect ratio > 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 (< 30 nm) “are not subject to the proposed classification, as it is assumed that due to a more tangled morphology, the fibre pathogenicity paradigm does not apply (to date negative evidence with regard to fibre-related mesotheliomatogenesis is limited to MWCNT[s] with 15 nm mean diameter).” BAuA concluded that data are sufficient for classification with regard to carcinogenicity and specific target organ toxicity after repeated exposure, but not for germ cell mutagenicity. The proposed entry in Annex VI of the Classification, Labeling and Packaging (CLP) Regulation is:

Carc. 1B, H350i

STOT RE 1, H372

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