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Don't define nanomaterials

Nature volume 475, page 31 (2011)Cite this article

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Basing regulations on a term with no scientific justification will do more harm than good, argues Andrew D. Maynard.

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References

  1. Maynard, A. D., Warheit, D. & Philbert, M. A. Toxicol. Sci. 120, S109–S129 (2011).

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  2. Holdren, J. P., Sunstein, C. R. & Siddiqui, I. A. Policy Principles for the U.S. Decision-making Concerning Regulation and Oversight of Applications of Nanotechnology and Nanomaterials (Executive Office of the President, 2011).

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  1. Andrew D. Maynard is director of the Risk Science Center at the University of Michigan School of Public Health, Ann Arbor, Michigan 48109-2029, USA.,

    Andrew D. Maynard

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  1. Andrew D. Maynard
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Correspondence to Andrew D. Maynard.

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FURTHER READING

Morris, J. et al. Nature Nanotechnol. 6, 73–77 (2011).

Bowman, D. M., van Calster, G. & Friedrichs, S. Nature Nanotechnol. 5, 92 (2010).

FDA Considering Whether an FDA-regulated Product Involves the Application of Nanotechnology (FDA, 2011); available at http://go.nature.com/oqkukv.

EPA Regulating Pesticides that Use Nanotechnology (EPA, 2011); available at http://go.nature.com/kxrydq

European Commission Public Consultation Document on the Definition of the Term 'Nanomaterial' (EC, 2010); available at http://go.nature.com/ladbj6

Euractiv.com. Commission's nano policy lost in definition (2011); available at http://go.nature.com/7chI1z.

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Maynard, A. Don't define nanomaterials. Nature 475, 31 (2011). https://doi.org/10.1038/475031a

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  1. Diana Boraschi

    Does structure-function relationship exist in nanomaterial risk assessment?

    The comment by Andrew D. Maynard (Don?t define nanomaterials; Nature 475, 31; 2011) on the inappropriateness of defining engineered nanomaterials in order to assess their toxicity/safety raises a very important issue not only for regulatory purposes but also, more in general, for understanding the interaction of nanomaterials with living systems.
    A major problem encountered by many biological and environmental scientists who have only recently approached the universe of nanotoxicity is the general overlook of the basic notions of the changes and evolution of biological reactions, which necessarily influence both the physico-chemical status and the reactivity of nanomaterials upon contact with a bio-system.
    Thus, defining nanomaterials in terms of dimensions, shape, surface area and charge, and chemical composition will not provide sufficient information on their possible toxicity, given the fact that each nanomaterial coming in contact with a biological system will rapidly change its characteristics and become something different. Indeed, the same nanomaterial will change in a different way depending on the biological system it comes in contact with (blood vs. mucus, blood of a healthy person vs. blood of a patient with rheumatoid arthritis, etc.), and the changes will evolve with time. This makes quite unfeasible any attempt at categorising nanomaterials based on physico-chemical parameters alone and, even more unrealistic, to associate a putative hazard to a given structure as originally synthesized.
    It is imperative, in order to come up with reliable and representative safety assays for the regulatory authorities, that many more basic scientists are recruited into the arena of nanosafety. The present challenge is to design a suite of assays, rigorously based on human primary cells and tissues, to measure the evolution of the human reactivity to nanomaterials and to identify a restricted range of meaningful parameters, ?correlates of risk? (as we do when assessing the correlates of protection following vaccination). This would provide the regulators within a short time with some robust assays, until more thorough scientific insight is reached.
    We must acknowledge that nanomaterials are not simple chemical structures, they are complex and they evolve and change. Therefore, in addition to safety in general, we should also try to define their safe use, as for instance we have done in the case of electricity. It is vital that the definition of what is hazardous and what is benign is reached based on sound scientific grounds, if we really want to protect the health of workers and consumers.

    Diana Boraschi &#8211 Institute of Biomedical Technologies, National Research Council, Pisa, Italy diana.boraschi@itb.cnr.it
    Albert Duschl &#8211 Department of Molecular Biology, University of Salzburg, Austria albert.duschl@sbg.ac.at
    Victor F. Puntes &#8211 Institut Català de Nanotecnologia, Barcelona, Spain victor.puntes@icn.cat

  2. Alexander Panich

    Definition of nanomaterials

    Andrew Maynard (Nature 475, 31; 2011) and Hermann Stamm (Nature 476, 399; 2011) discussed the need and possibility of defining engineered nanomaterials. Since the characteristic dimension, at which the difference in properties of nano- and bulk samples occurs, varies noticeably from compound to compound, it is hardly possible to find a general criterion to be valid for all materials. In such a case, a good approach is to divide the materials into several classes and to establish a criterion for each class. For example, in conductive and semiconductive nanoparticles a criterion of defining nanomaterials should be based on the comparison of the sample size with the de Broglie wavelength of the carriers. In these compounds, drop of the top of the valence band and lift of the bottom of the conduction band with reduced particle size result in appearance of the energy gap, i.e. in metal-isolator transition when the sample size becomes smaller than the de Broglie wavelength. In metals, the latter is of the order of the lattice spacing, thus quantum confinement is visible only for very small particles. In semimetals and semiconductors, however, the de Broglie wavelength may considerably exceed the lattice spacing. E.g. semimetal bismuth, which is characterized by a long mean free path of carriers, exhibits quantum confinement and semimetal-semiconductor transition as the nanowire diameter and film thickness are reduced down to 80-100 nm, respectively. (Z. B. Zhang et al., Appl. Phys. Lett. 73, 1589; 1998; V. N. Lutskii et al., JETP Lett. 4, 179; 1966). A similar behavior was observed in Tl2Se nanorods with the diameter of 75 nm. (A. M. Panich et al., Phys. Rev. B 74, 233305; 2006).
    The suggested criterion is based on strong physical principles and meets all scientific requirements.

    Alexander M. Panich, Department of Physics, Ben-Gurion University of the Negev,
    Be'er Sheva 84105, Israel, e-mail: pan@bgu.ac.il

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