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Ecotoxicological information

Toxicity to terrestrial arthropods

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Description of key information

In accordance with column 2 of REACH Annex IX, studies with terrestrial arthropods do not need to be conducted as direct and indirect exposure of the soil compartment is unlikely.  

Key value for chemical safety assessment

Additional information

Justification for a weight of evidence approach for adaptation according to column 2 of REACH Annex IX

 

1. Hazard Information:
Three acute tests in aqueous system with algae, daphnia, fish representing the three trophic levels showed no significant effects. Due to molecular weight and size, MWCNT are not expected to be bioavailable as they are characterised by a very low vapour pressure and a very low water solubility. It is therefore expected that tests with terrestrial arthropods would not give additional scientific evidence.

 

2. Exposure Information:
a) Operational conditions and risk management measures in all related exposure scenarios: MWCNT are manufactured in a closed process with no likelihood of exposure. Any waste gas is incinerated and no waste water is generated. Thus, manufacture of MWCNT does not result in any exposure of the soil compartment. Direct and indirect exposure of the soil compartment from downstream users is very limited as surfaces in the processing units are sealed and waste gas and waste water are adequately processed. End-uses of MWCNT involve incorporation into material matrices, again leading to negligible direct and indirect exposure of the soil compartment.

b) Quantification of the resulting release/exposure: A relevant distribution into soil and a considerable exposure of soil macroorganisms is not expected. This is supported by results of environmental modelling in the scientific literature. For instance, Gottschalk et al. predicted soil concentrations for MWCNT to be negligible leading to a yearly deposition yielding 0.0015 µg/kg (direct emission to soil) and 0.074 µg/kg (sludge treated soil) (Gottschalk et al. (2009) Environ. Sci. Technol. 43, 9216-9222). These estimations include the whole life cycle of the substance including manufacture, consumption,recycling and waste stages. Furthermore it was reported recently (Nguyen T., Presentation at Nanosafe 2010, Grenoble, France), that MWCNT bound in polymer matrices form a network on the composite surface during UV exposure which may be responsible for preventing release of MWCNT to the environment.

 

3. Conclusion:
No further testing of MWCNT is considered necessary, as there is sufficient weight of evidence to conclude that MWCNT are not toxic to terrestrial arthropods. Based on operational conditions during the service life and based on release estimations, the registrant demonstrates that exposure to the environment is so low that additional information will not lead to improvement of risk management.