Strategies to overcome challenges in aquatic testing of particulate material – Expert Group

Context

ECHA developed appendices to the guidance documents on data requirements under REACH specific to nanomaterials, including for guidance R7b (endpoint specific guidance covering ecotoxicity and fate testing). The advice provided in these appendices is focussed to specific recommendations for nanomaterials, though parts of the advice may also be applicable to other particulate materials (PMs).

With respect to REACH guidance for nanomaterials, the aquatic testing of PM has revealed inherent challenges aggravating the application of the respective guidance documents.

For instance, the preparation of stable PM dispersions is often not possible for standard test media. To overcome this issue, the addition of humic substances, changes in pH and other modifications resulting in an adjustment of the test media composition, are possibilities to improve dispersion stability. However, such modifications do not always result in enhanced PM dispersion stability. In fact, those kinds of modifications frequently alter the behaviour and fate of PM, and consequently their ecotoxicological potential (e.g. reactivity, bioavailability, size distribution, etc.), which may cause acceptance issues with authorities.

What is needed is a testing strategy, which defines the best way forward for aquatic testing of PM. This may be an adjustment of the test media composition, with the consent of the authorities, to ensure acceptance of the study, or, a replacement of the aquatic testing by a more appropriate setting (e.g. sediment testing).

Both options require upfront buy-in of the strategy from the regulatory authorities, and consequently the design of such a strategy should be a joint effort.