Registration Dossier

Environmental fate & pathways

Bioaccumulation: aquatic / sediment

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In accordance with column 2 of REACH Annex IX, a study on bioaccumulation in aquatic species study does not need to be conducted as MWCNT have a low potential for bioaccumulation. Following current ECHA guidance chapter R7c, a substance is unlikely to be considered as bioaccumulative when it has a molecular weight > 1100 g/mol and a diameter Dmax average of > 1.7 nm. This is based on substances with high molecular weights (typically > 700 g/mol) and/or large molecular diameters (typically > 1.5 nm) being unlikely to be absorbed and to bioconcentrate.

The structure of Carbon Nanotubes (CNT) is a carbon layer similar to graphite which is additionally rolled to form tubes. Multi-Walled Carbon Nanotubes (MWCNT) are large molecules consisting of typically several million carbon atoms with a high molecular weight.

The MWCNT covered in this registration dossier of the form defined in IUCLID section 4.5 exceed the above referenced value for molecular weight by several orders of magnitude and the molecular size criterion by over an order of magnitude for the individual tube strands and the molecular size criterion by several orders of magnitude based on the tangled tube networks. Therefore, the potential for adsorption and bioaccumulation is negligible. Consequently, testing for bioaccumulation is unnecessary.

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