The Organization for Economic Cooperation and Development (OECD) recently published two guidance documents in its series on testing and assessment:

• Guidance Document on Aquatic and Sediment Toxicological Testing of Nanomaterials (No. 317): The guidance document addresses practical aspects of carrying out valid tests with manufactured nanomaterials, as well as modifications or additions to OECD Test Guideline procedures intended to improve incrementally the accuracy, intra-laboratory repeatability, inter-laboratory reproducibility, and intra-laboratory reproducibility of test results.  The guidance document considers initial characterization of test materials, preparation of test dispersion, monitoring the behavior of manufactured nanomaterials in the test dispersion throughout the duration of the test, and quantifying exposure and exposure-response.  The focus of the guidance document is on measurements of worst-case hazard using traditional population level endpoints, including survival, growth, and reproduction, and does not provide guidance on making formal risk assessments.  OECD states that since the focus is on the most conservative assessment of hazard, the guidance within involves efforts to disperse manufactured nanomaterials into laboratory media that may not always be realistic to environmental dispersal.

• Guidance Document for the Testing of Dissolution and Dispersion Stability of Nanomaterials and the Use of the Data for Further Environmental Testing and Assessment Strategies (Excel) (No. 318): The guidance document provides guidance for the methods to address dissolution rate and dispersion stability for nanomaterials, with a focus on environmental aqueous media.  OECD states that the guidance provided is relevant for solids in the nanoscale, as well as their aggregates and agglomerates, and it focuses on their fate and behavior in aqueous media.  In particular, the guidance document presents the influence of various experimental conditions on the performance and outcomes of the discussed methods.  In addition, the guidance document addresses modifications or additions to the methods and aims to give support for the interpretation of the test results.