Concerns about the need for research, not only to understand potential hazards from nanomaterials, but also to develop an appropriate framework to regulate them, are well justified. An estimated 500 to 2,000 nanomaterials were placed on the EU market at volumes of at least 1 tonne/year in the period from 2012 to 2014 (5). This trend is likely to continue or even increase, and these nanomaterials are consequently affected by registration obligations under the chemicals’ safety framework known as REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), which entered into force in 2007. About 10% of these nanomaterials are untreated nanoforms of a bulk material that is already registered (5). Testing these nanomaterials and updating the registration dossiers would entail costs of between €50 million and €315 million based on the proposed amendments to REACH guidelines for nanoforms.
In more recent studies using isotopically labelled CuO (8) and Ag (9), we have demonstrated the increased sensitivity that isotopic labeling provides. This is important because experiments can now be performed at environmentally relevant concentrations. As a result, exposures are more realistic and the true toxicity mechanisms can be identified and distinguished from the result of excessive dosing. In the case of Ag nanoparticles, isotope mass balance calculations show that labelling increases tracing sensitivities at least 40 times and possibly up to 4000 times, compared to when the label is not present. This is despite having to use a silver isotope (107Ag) that is not particularly rare (approx. 52% of the elements total natural abundance).