The Organization for Economic Cooperation and Development (OECD) announced on July 4, 2023, that it published a number of new, updated, and corrected Test Guidelines (TG), including the following for nanomaterials:

• TG No. 126: Determination of the Hydrophobicity Index of Nanomaterials through an Affinity Measurement: This new TG describes a method to determine the hydrophobicity index (Hy) of nanomaterials, through an affinity measurement. OECD states that hydrophobicity is defined as “the association of non-polar groups or molecules in an aqueous environment which arises from the tendency of water to exclude non-polar molecules.” According to OECD, by measuring their binding rate to different engineered surfaces (collectors), Hy expresses the tendency of the nanomaterials to favor the binding to a non-polar (hydrophobic) surface because of its low affinity for water. OECD notes that the method applies to nanomaterials dispersed in an aqueous solution or to nanomaterial powders after their dispersions in aqueous solutions, with or without a surfactant, using a recommended protocol.

On July 4, 2023, OECD also released a corrected version of its Report on the WNT Workshop how to prepare the Test Guidelines Programme for emerging technologies. The Working Party of the National Coordinators of the TG Program (WNT) held a workshop in December 2022 on how to prepare for emerging science and technologies. During WNT’s annual meeting in April 2022, it agreed to a proposal for the workshop and preparatory steps. The workshop was attended by 56 participants from 22 delegations and chaired by Michael Oelgeschlaeger (Germany). The OECD report summarizes the rationale for organizing the event and the preparatory steps taken in the preceding months, the workshop development, and the outcome of discussions in breakout group and plenary sessions, as well as the workshop conclusions and next steps.

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