The chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is... Show moreThe chemical composition and properties of environmental media determine nanomaterial (NM) transport, fate, biouptake, and organism response. To compare and interpret experimental data, it is essential that sufficient context be provided for describing the physical and chemical characteristics of the setting in which a nanomaterial may be present. While the nanomaterial environmental, health and safety (NanoEHS) field has begun harmonization to allow data comparison and re-use (e.g. using standardized materials, defining a minimum set of required material characterizations), there is limited guidance for standardizing test media. Since most of the NM properties driving environmental behaviour and toxicity are medium-dependent, harmonization of media is critical. A workshop in March 2016 at Duke University identified five categories of test media: aquatic testing media, soil and sediment testing media, biological testing media, engineered systems testing media and product matrix testing media. For each category of test media, a minimum set of medium characteristics to report in all NM tests is recommended. Definitions and detail level of the recommendations for specific standardized media vary across these media categories. This reflects the variation in the maturity of their use as a test medium and associated measurement techniques, variation in utility and relevance of standardizing medium properties, ability to simplify standardizing reporting requirements, and in the availability of established standard reference media. Adoption of these media harmonization recommendations will facilitate the generation of integrated comparable datasets on NM fate and effects. This will in turn allow testing of the predictive utility of functional assay measurements on NMs in relevant media, support investigation of first principles approaches to understand behavioral mechanisms, and support categorization strategies to guide research, commercial development, and policy. Show less
Mass is traditionally the unique measure of the administered dose in toxicity studies with conventional chemical substances. Because of the variety of specific physical properties of nanoparticles,... Show moreMass is traditionally the unique measure of the administered dose in toxicity studies with conventional chemical substances. Because of the variety of specific physical properties of nanoparticles, other dose metrics such as the number of particles, their size, shape, surface area or volume may be more appropriate. Here we applied a systematic, unbiased approach to derive the most appropriate dose metric for nanoparticles from experimental data. The approach was exemplified for copper, zinc oxide, and silver nanoparticles with different diameters, coatings and shapes, combining experiments with six aquatic organisms, two mammalian and two piscine liver cell lines from different research groups. The nanoparticle diameter appeared to be a powerful estimator of metal oxide nanoparticle effects. Since effect concentrations were related to size to the power 3, it is indicated that volume (mass) is the appropriate dose metric for all tested species and toxicological endpoints and all tested metal oxide nanoparticles within the tested size range (25–500 nm). The new method enables extrapolation of test results from one type of metal oxide nanomaterial to another, thereby offering a powerful tool to improved efficiency in risk research and risk assessment of nanomaterials. Show less
