In an article published on November 8, 2016 in the peer-reviewed journal Environmental Health, Jennifer Sass and colleagues from the Natural Resources Defense Council, U.S., report on the application of GreenScreen to perform comparative hazard assessment of conventional silver and two forms of nanosilver. GreenScreen is a tool developed by the non-profit group Clean Production Action (FPF reported). It allows screening and comparing chemicals based on their inherent hazards. The scientists used publicly available literature to assign hazard classification levels according to defined GreenScreen hazard criteria; where data were not available, a data gap was assigned.
One form of nanosilver, low-soluble nanosilver, received the same – in fact, the highest possible – hazard score as the conventional silver. The second evaluated nanosilver form, a silica-silver nanocomposite called AGS-20, could not be scored because of data gaps. Of note, in the U.S. AGS-20 is approved as an antimicrobial (for non-food contact uses, notably coating of textiles).
The study demonstrated that the GreenScreen tool can be used, with minor adaptations, to compare hazards across a conventional form and various nanoforms of the same substance. Minor nano-specific adaptations include the added requirement to report a number of physical property parameters, such as agglomeration and/or aggregation state, chemical composition, purity, shape, surface area and charge, surface chemistry, and characterization in the relevant experimental media. These allow better characterizing the nanomaterials being evaluated.
The major limitation to the application of the GreenScreen tool was perceived to be the lack of nano-specific test data. Numerous data gaps identified for nanoforms speak in favor of the common regulatory requirement to evaluate each nanomaterial on a case by case basis with use of nanospecific data as opposed to extrapolating from the data obtained for the conventional form. To fill the data gaps, the authors recommended that “regulatory agencies and others require more robust data sets on each novel nanomaterial before granting market approval.”
Coming Clean (2016). “Lifting the nano veil: A peek at nanosilver with GreenScreen®.”
Sass, J., et al. (2016). “Use of a modified GreenScreen tool to conduct a screening-level comparative hazard assessment of conventional silver and two forms of nanosilver.” Environmental Health 15:105.