On 12-13th June 2018, a joint workshop on SOPs harmonization was held at RIVM, Netherlands. This activity was part of the Nanosafety Cluster (Working Group C) and was sponsored by the EU projects PATROLS and GRACIOUS. It was organized to follow-up on the EU ProSafe ‘White Paper’ recommendation for harmonised and validated test methods for nanomaterials (NMs) to support regulatory risk assessment. Such SOPs are required to facilitate generation of data that are reliable and comparable, for application in risk assessment and modelling NMs effects.

The ultimate workshop goal was to transfer SOPs towards a CEN/ISO document or an OECD Test Guideline (TG) / Guidance Document (GD), with an intermediate goal of providing SOPs for use within NanoSafety Cluster projects. All 37 participants from 10 different European countries had either hands-on experience with different tests, were familiar with writing SOPs or had expertise on TG development/standardisation to create and advance SOPs on a variety of topics.

The workshop introductory session included 5 invited speakers. The importance of identifying the use or applicability domain of specific SOPs was highlighted by Minne Heringa (RIVM). Toxicological (in vitro) data can be either used in a qualitative way (classification and labelling), a quantitative way (limit value derivation) or in an actual risk assessment, which governs the expected level of SOP validation required for data acceptance. Peter Kearns (OECD) presented the clear regulatory need for alternative assays, and presented the necessity for clarity on the protocol developed to support scientific and regulatory acceptance. Denis Koltsov (ISO TC229 Nanotechnologies chair) explained the route and timelines towards development of an ISO standard; while Martin Clift (Swansea Uni) presented the NanoImpactNet SOP template, which was considered an excellent model for producing new SOPs. Finally, Elisabeth Heunisch (BauA) elaborated on the MALTA project, which is intended to accelerate the process of updating OECD TGs with respect to NMs testing, to better support the up-coming REACH annexe changes.

The following workshop sessions chaired by Flemming Cassee (RIVM), Shareen Doak (Swansea Uni) and Vicki Stone (Heriot-Watt Uni) focused on development of multiple SOPs:

1. Sample preparation for toxicity testing including sonicator probe calibration, NMs dispersion and sample characterization in biological matrices protocols (Keld Alstrup Jensen, NRCWE)
2. Dispersion and ageing protocols to better mimic NMs transformation in the gastro-intestinal tract (GIT) following oral exposure (Roel Schins, IUF)
3. SOPs for multicellular in vitro models of the human GIT and liver (Ali Kermanizadeh, Heriot-Watt Uni)
4. Characterization in biological materials using ICPMS technologies (Ruud Peters, RIKILT & Norbert Jakubowski, Bundesanstalt für Materialforschung und–prüfung)
5. SOPs for oxidative stress and Reactive Oxygen Species measurements, including the development of an assay selection decision tree (Matthew Boyles, IOM)
6. Review of SOPs for genotoxicity assays to identify areas of adaptation required for NMs (Hedwig Braakhuis, RIVM).

Valuable input from the group was collected and drafts of the SOPs discussed will be prepared as a follow-up, corresponding with deliverable deadlines in the EU projects PATROLS and GRACIOUS.