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Nanotechnology: the things we don't know
(Nanowerk Spotlight) "To know that we know what we know, and that we do not know what we do not know, that is true knowledge" (Thoreau). Seems like our 'true knowledge' of the risks of nanotechnology is getting better and better. There still is a lot we don't know yet about the environmental, health and safety impact of nanomaterials, but at least scientists are making progress in identifying the gaps – the 'known unknowns' as they call it.
A group of researchers at the Technical University of Denmark (DTU) have conducted a systematic analysis of 31 recently published reports and articles which discuss the environmental, health, and safety (EHS) aspects of nanomaterials. They find that serious knowledge gaps pervade nearly all areas of basic nanotechnology EHS knowledge.
These knowledge gaps or areas of uncertainty were ranked to how often they were included in the screened literature. The analysis found that the following areas in particular have been highly cited as important knowledge gaps within the field:
  • the lack of reference materials and standardization
  • environmental fate and behavior
  • human and environmental toxicity
  • test methods to assess, particularly, the effects, and
  • commercial or industrial-related aspects (e.g. life cycle assessments).
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    "We expect that further empirical research will presumably reduce most areas of uncertainty, although it is likely to be time-consuming and expensive" Khara Deanne Grieger, a PhD student in DTU's Department of Environmental Engineering, tells Nanowerk. "Our analysis shows that research should be prioritized towards the assessment and development of testing procedures and equipment and full characterization of nanomaterials in both biotic and abiotic systems in order to most effectively reduce uncertainties in the short term given the minimal presence of inherent stochastic variability in these locations."
    Grieger emphasizes that, while research within assessing toxicity/ecotoxicity and monitoring exposure are indeed greatly important in nano-EHS research, the lack of standardized testing procedures, equipment, materials and full characterization of NM may create serious difficulties in comparing test results and drawing conclusions.
    The DTU team – Grieger, Steffen Foss Hansen and Anders Braun, part of the research group Nanotechnology & Risk – has published their findings in a recent paper in Nanotoxicology (The known unknowns of nanomaterials: Describing and characterizing uncertainty within environmental, health and safety risks).
    This analysis was motivated by the aim of assisting the development of nano-EHS research priorities. The fields of nanotechnology and nanomaterial development are moving extremely fast, and there are many questions and debates on how to assess some of the potential health and environmental impacts of nanomaterials. Therefore, a better description of the most frequently cited knowledge gaps and areas of uncertainty is one possible way to prioritize nano-EHS research.
    "Since it is known that describing and communicating scientific uncertainty is very important, especially in terms of making decisions in complex policy-relevant science, we thought it was important to more qualitatively describe the uncertainty within the field to more accurate communicate to various stakeholders the types and levels of uncertainty that are involved with EHS issues of nanomaterials," says Grieger.
    Since the presence of uncertainty plays such a large role in environmental and health assessments of nanomaterials as well as decision making processes within the field, this analysis is highly relevant and timely in order to fully evaluate the collective knowledge on the potential EHS risks of nanomaterial exposure. This information may increase transparency and openness within nano-risk characterization and analysis processes, which is also important when considering the e.g. prioritization of research efforts and performing risk assessments.
    Within the 31 documents reviewed the researchers found a total of 2752 different citations of uncertainty or incomplete knowledge regarding the potential environmental, health and safety risks of nanomaterials. These fall within four general groups:
  • testing considerations (which covers how to perform various tests on nanomaterials, including, e.g., equipment, methodology and risk assessment procedures) (31% of total uncertainty citations found);
  • assessing effects from nanomaterials exposure (including beneficial or deleterious effects from nanomaterials exposure) (25%)
  • characterization of nanomaterials (including, e.g., inherent properties of NM and how they behave in organisms and the environment) (21%);
  • assessing exposure (including, e.g., human and environmental exposures and routes) (13%)
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    The three DTU scientists acknowledge the limitations of this type of analysis: that it may not necessarily reflect all EHS-related uncertainties within the production and use of nanomaterials; that estimating the current level of knowledge may be debatable in itself especially considering 'unknown unknowns'; and that the selected reports focused mainly on broad EHS aspects of NM and the selected review articles were not intended for detailed discussions on, for example, specific testing methodologies.
    Nevertheless, these findings are novel in that it is the first attempt known to the authors to systematically and comprehensively describe and characterize scientific uncertainty beyond merely statistical terms in regards to EHS risks of nanomaterials.
    "To put the analysis in a broader context, it has been known for over two decades that characterizing and communicating scientific uncertainty and ignorance within particularly complex, policy-relevant science has played an increasingly important role," explains Grieger. "Also, while there are other methods and frameworks to assess scientific uncertainty – e.g. Monte Carlo analysis, sensitivity analysis, etc. – the knowledge gaps within estimating EHS risks of nanomaterials are likely to be too large, complex, and potentially serious to be handled with solely quantitative estimates, and therefore we chose a qualitative uncertainty analysis framework for this analysis."
    The main field of application of this work is to better communicate the scientific uncertainty involved in estimates of potential health and environmental risks of nanomaterials. This is in terms of not only the areas of uncertainty but also the level and nature of this uncertainty. Regulators, industry, and scientists may benefit from this knowledge since it will likely provide a more comprehensive evaluation of the current knowledge (or on the other side, uncertainty) associated with the potential risks of nanomaterials. With this, there are some fields which have varying degrees of uncertainty compared to others, similar to the fact that it is likely that more knowledge is available for e.g. some nanomaterials than others as well. Therefore, a more comprehensive and thorough description of the uncertainties involved in the different aspects of EHS risks can be better communicated, and ultimately aid in better, more informed decisions.
    Grieger, Hansen and Baun recommend that further attention be given to the assessment and development of standardized testing procedures, equipment, materials as well as the full characterization of nanomaterials in order to most effectively reduce uncertainties in the near term.
    "This is based on the minimal presence of inherent stochastic variability in these knowledge gaps, as found in this analysis" says Grieger. "Research within these fields is also important due to the serious challenges that are created when comparing test results and drawing conclusions without adequate standardization and nanomaterial characterization."
    She anticipates that the research fields involved in assessing the health and environmental risks of nanomaterials, and particularly those involved in the decision making processes in regards to nano-risks, increasingly open up to new methodologies and frameworks. This is due to the diversity of nanomaterials and products containing them and the fact that current assessment methods often struggle to keep pace.
    "Also, in light of the general movement towards ?greener? engineering and production, I also anticipate that ?greener? initiatives will start to be incorporated into the production of at least some nanomaterials. Among other things, this may help consumer acceptance as well as reduce some potentially costly ?down stream? health and environmental assessments."
    Michael Berger By – Michael is author of three books by the Royal Society of Chemistry:
    Nano-Society: Pushing the Boundaries of Technology,
    Nanotechnology: The Future is Tiny, and
    Nanoengineering: The Skills and Tools Making Technology Invisible
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