Classification Strategies for Regulatory Nanodefinitions - Safety of Nanomaterials along Their Lifecycle - page 47

European Biocides Directive, and the French Decret have regulatory status, whereas
the other definitions have advisory status. The French Decret refers to the European
Commission (EC) nanodefinition recommendation (Table 3.1) and narrows the scope
by restriction to “intentionally produced” materials, but widens the scope by sub-kg
notification thresholds. Particulate materials exhibit a distribution of particle sizes,
are often polymorph, and in most cases several particles are sintered together to
aggregates, which further agglomerate. Particles “bound” in agglomerates or aggre-
gates are explicitly included—this is the first major analytical challenge. The other
major analytical challenge is the number metrics employed for size distributions
and cut-off criteria. Only the United States Environmental Protection Agency has
stuck to the well-established mass metrics, for which standardized methods exist.
All definitions refer to the ISO size range of 1-100 nm. To exclude molecular struc-
tures, “particle” structures are mentioned, and additionally macromolecules such as
polymers and proteins are excluded. The upper size limit is softened in the Health
Canada definition, which considers any manufactured substance or product and any
component material, ingredient, device, or structure to be a nanomaterial if it is at or
within the nanoscale in at least one external dimension, or has an internal or surface
structure at the nanoscale, or if it is smaller or larger than the nanoscale in all dimen-
sions and exhibits one or more nanoscale properties/phenomena.
The EC recommendation for a definition has possibly the broadest scope because it
refers to number metrics and includes natural, incidental, and manufactured materials
containing particles (Table 3.1) (EC 2011), and provides the framework for sector-spe-
cific definitions (Bleeker et al. 2013). However, it clearly expresses that classification
as a nanomaterial does not imply that the material has a specific risk or new haz-
ardous properties (EC 2011). The number metrics is the game-changing decision that
inflates the scope. The first estimates of the impact of the EC nanodefinition recom-
mendation by BiPRO and Öko-Institut expect about 2000-5000 substances in scope;
80,000-160,000 preparations and 800,000-1,300,000 articles alone in Belgium. About
35,000-45,000 enterprises (15%-20% of all enterprises in Belgium) would be affected
from the following sectors: cosmetics, healthcare, food and feed, coatings and inks,
cleaning and disinfection, tires and rubber products, plastic products, building and
construction, textiles, paper and wood products, sporting goods, electronics, and so
on (BiPRO 2013). Although the EC nanodefinition recommendation does not specify
material composition, an understanding of correlated nano-object size and compo-
sition will be necessary, especially for formulated products with several particulate
substances mixed (Brown et al. 2013). In the absence of a technical guidance, the fol-
lowing sections review the established and emerging methods that determine size dis-
tributions in number metrics, and propose practical elements of a technical guidance.
3.2 METHODS TO MEASURE THE SIZE DISTRIBUTION
IN NUMBER METRICS: FOR POWDERS
Electron microscopy is generally accepted as the reference counting method
(Figure 3.1) for the size distribution of particulate materials. For reasonably well-
dispersible powders, transmission electron microscopy (TEM) can be performed on
monolayer preparations, such that the remaining uncertainty is the attribution of an