What Is "Environmentally Relevant"? A Framework To Advance Research On The Environmental Fate And Effects Of Engineered Nanomaterials

Environmental nanoscientists and nanotoxicologists have made significant progress towards understanding the various factors and processes that impact the environmental fate and effects of engineered nanomaterials (ENMs); nevertheless, many knowledge gaps remain. This is partly due to a disconnect that occurs when these factors or processes are elucidated in simplified experimental systems and then applied to predict ENM behavior in significantly more complex real-world systems. To aid the translation of findings between these two extremes, we have outlined and demonstrated the use of a Framework for Relevance And Methods Evaluation (FRAME) based on three components or pillars that collectively define the "environmental realism" of a given experimental design. The three pillars include (1) the properties of the ENMs, (2) the experimental conditions, and (3) the exposure scenario and endpoints that are assessed. FRAME provides researchers with an approach for assessing the environmental relevance of alternative experimental designs. It also provides a basis for reporting how an individual study fits within the broader body of scientific knowledge and for identifying areas where additional research is needed. The proposed framework is intended to be used throughout the scientific process, from the initial conception of the experimental design and continuing through to the interpretation of experimental results. Committing to a more complete assessment of environmental realism has the potential to prevent the overgeneralization of results determined in simplified experimental systems and move the field forward more quickly through the identification of critical knowledge gaps.