Challenges of Regulation and Risk Assessment of Nanomaterials

Primary and secondary characterization of the ENPRA ENP
Jensen K.A. 1 , Bilanikova D. 2 , Brunelli A. 2 , Pojana G. 2 , Birkedal R. 1 , Levin M. 1 , Koponen I.K. 1 ,
Kofoed-Sørensen V. 1 , Clausen P.A. 1 , Marcomini A. 2 , Jacobsen N.R. 1 , Wallin H. 1
1 National Research Centre for the Working Environment, Copenhagen, Denmark
2 University Ca’ Foscari Venice, Italy
The nanomaterials in ENPRA comprise six materials from the OECD WPMN sponsorship programme
[NM101 (TiO2), NM110 (ZnO), NM111 (silane-coated ZnO), NM300 (dispersed silver particles: Ag),
NM400 (carbon coated multi-walled carbon nanotube) and NM402 (multi-walled carbon nanotube)].
Additional four TiO2 samples were selected: A 10 nm- (NRCWE-001) and a 100 nm-size rutile TiO2
(NRCWE-004) of which a subsample of NRCWE-001 was modified to achieve a chemical positive
(NRCWE-002) and negative charge (NRCWE-003). All test materials were selected to obtain a
“dynamic range” in physico-chemical properties and toxicity.
In this work, we characterize the selected test materials and the particle characteristics in the in
batch dispersion and in vitro exposure mediums. We have also established a common serum-based
method for particle batch dispersion for the ENPRA toxicity testing. The primary characterization is
important to document the test materials (Figure 1), but the data are also highly warranted as many
of the end-points (especially primary size and surface area) are thought to play a mechanistic role in
particle toxicity. In addition, we also describe the hydrochemical reactivity (hydroxyl radical
formation capacity and redox potential in test mediums) of the NMs and their emission potential by
rotating drum dustiness testing.
Some of the major challenges in the characterization of primary physico-chemical characteristics, are
inappropriate methods for bulk characterization of CNT, method-dependent results on size
distributions, variation in metal catalyst extraction efficiencies from CNT for ICP elemental analysis,
quantitative analysis of unknown organic ENP surface functionalisations, applicability of the noncatalyzed
benzoic acid test method for quantification of intrinsic hydroxyl radical formation capacity.
Methods and results will be discussed in the lecture and special focus will be set on the need to
improve our understanding of test item preparation and the behavior and reactivity of NM in both
exposure mediums and specific biological compartments.
Figure 1. Overview of the main primary physico-chemical
characteristics and analytical methods applied in ENPRA. As
indicated by the arrows, several methods can give supporting
information to improve the understanding of the materials.
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