Nanoscale reference materials for environmental, health and safety measurements: needs, gaps and opportunities

Abstract

The authors critically reviewed published lists of nano-objects and their physico-chemical properties deemed important for risk assessment and discussed metrological challenges associated with the development of nanoscale reference materials (RMs). Five lists were identified that contained 25 (classes of) nano-objects; only four (gold, silicon dioxide, silver, titanium dioxide) appeared on all lists. Twenty-three properties were identified for characterisation; only (specific) surface area appeared on all lists. The key themes that emerged from this review were: 1) various groups have prioritised nano-objects for development as “candidate RMs” with limited consensus; 2) a lack of harmonised terminology hinders accurate description of many nano-object properties; 3) many properties identified for characterisation are ill-defined or qualitative and hence are not metrologically traceable; 4) standardised protocols are critically needed for characterisation of nano-objects as delivered in relevant media and as administered to toxicological models; 5) the measurement processes being used to characterise a nano-object must be understood because instruments may measure a given sample in a different way; 6) appropriate RMs should be used for both accurate instrument calibration and for more general testing purposes (e.g., protocol validation); 7) there is a need to clarify that where RMs are not available, if “(representative) test materials” that lack reference or certified values may be useful for toxicology testing and 8) there is a need for consensus building within the nanotechnology and environmental, health and safety communities to prioritise RM needs and better define the required properties and (physical or chemical) forms of the candidate materials.

Keywords::

• engineered nanomaterials
• nano-objects
• nanoparticles
• nanotechnology
• reference materials
• characterisation
• physico-chemical properties
• exposure
• risk

Acknowledgements

The authors gratefully acknowledge R. MacCuspie at NIST and V. Castranova and M. Murashov at NIOSH for critical review of this manuscript. The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the National Institute for Occupational Safety and Health. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology. This work received support from the European Community Research Infrastructures project QNano which is financed under the FP7 Capacities Programme (Grant No. INFRA-2010-262163).