Minimum physicochemical characterisation requirements for nanomaterial regulation.

Appropriate characterisation of manufactured nanomaterials (NMs) is vital for many aspects of their synthesis, product formulation, toxicological testing and regulation. As the range and quantity of NMs in production has expanded, the interest in their potential environmental and toxicological consequences has grown. With this growth, there is increased need for clarity and rigour in characterising appropriate physicochemical parameters. Which physicochemical parameters should be characterised and under what conditions remains a topic of debate, along with the most appropriate techniques and methodologies to best describe any one characteristic. This review assesses the characterisation requirements of current and future regulatory frameworks for NMs, with specific focus on the incoming REACH framework of the EU. For regulatory compliance, characterisation requirements will be necessarily prescriptive. The minimum physicochemical parameters required to adequately describe NMs for regulatory purposes are proposed, along with a discussion of the most appropriate mechanisms to obtain those data in terms of the overarching delivery mechanism. Guiding principles for particle characterisation during the hazard testing required to comply with regulations are examined.