A number of physicochemical properties characterize a chemical substance. Some of these properties are characteristic for one specific substance. Other properties can vary to a smaller or larger degree, which can for example lead to a change in the hazard potential of said substance. The physicochemical characterization is an overarching task that touches not only occupation hygiene issues but is essential for consumer protection and environmental protection as well. Particle size and size distribution is one of the physicochemical properties which can vary for a substance. The size distribution can be determined and described with different methods and on different bases, e.g. mass, number or volume based, just to name the most common ones. Goal of the project is the "Development of a specific OECD Guideline to determine the particle size and number size distribution of nanomaterials". Thereby such guideline describes the practical procedure, the scope and limitations of one or more methods to determine an endpoint of a substance. The new guideline currently drafted is closely related to the OECD Test Guideline 110 ("Particle Size Distribution / Fibre Length and Diameter Distributions"). It will summarise methods for reproducibly measuring particle size distributions and size distributions as well as for the morphological characterization (determination of diameter and length per fibre and the distribution) of fibres including nanofibers. The draft work program of the OECD-WPMN for 2017-2020 foresees the review of the OECD Test Guideline 110.
The OECD has in the past published a document listing the in principle available methods for particle size measurements in the sub-micrometre range down to 1 nm. These methods are examined and assessed in theory and tested under the aspects of practicability, reproducibility and validity. The assessment will indicate if a method needs adaptions or can be used without further adaptions. These assessed methods will be further tested in an international interlaboratory comparison study, which is one prerequisite for a draft guideline to be accepted. During the interlaboratory comparison study, different laboratories will use the methods according to the draft guideline with specifically chosen materials. The results are collected, compared and evaluated afterwards.
The project will be coordinated by BAuA and carried out together with BAM. The focus of BAuA in this project is the development and establishment of test methods for fibres, including nanofibers. The results of the project, including those for (nano-)particles by BAM, provide a basis for drafting a guideline document for size distributions of particles and fibres in the size range of around 1-1000 nm. This document is will be submitted to the OECD Testing Program via the German delegation.
After adoption and publication of the test guideline by the OECD Joint Meeting of the Chemicals Committee and the Working Party on Chemicals, Pesticides and Biotechnology, it is accessible to all laboratories in the OECD member countries, and those outside the OECD as well. It provides methods to determine the basic physicochemical property of particle size and size distribution. This can be used, for example, in the context of the EU REACH chemicals regulation to comply with standard information requirements.
Unit 4.5 "Particulate Hazardous Substances, Advanced Materials"