Biomedical Engineering Reference
In-Depth Information
and (iv) the nanoparticles already present in the background, is required.
Additionally, the emitted mass and number of particle concentration are
needed along with knowledge about the physico-chemical properties of the
nanoparticles, which include the shape, surface area, surface chemistry, com-
position (including coatings), solubility, charge, crystal structure, and state of
agglomeration of the nanoparticles.
67-71
However, until now, little is known about the exact magnitude of the emis-
sions.
72-74
Although several measurements are currently performed in the work-
place and during laboratory simulations, not all studies are able to distinguish
between background and nanoproduct-induced emissions,
75,76
and techniques
do not allow for consistent monitoring and characterization of nanoparticle
emissions.
74
In several studies, it was therefore not possible to assign consis-
tently the part of nanoparticle emissions arising from the nanoproduct itself to
the measured occupational concentrations. Among the few studies that report
emissions of nanoparticles, some detected nano-TiO
2
in water leaching from
exterior painted facades
77
or releases of nanosilver from textiles, for example,
during washing.
24,53
Other studies also reported emissions during the manu-
facturing stage
78
and at the disposal stage, for example, recycling.
79
Difficulties also arise in characterizing the physico-chemical properties of
the nanoparticles, primarily due to (i) the variations in the importance of the
different properties among nanoparticles that prevent any generic treatment,
for example, the crystallinity for nano-TiO
2
, which has a strong influence on
its toxicity (e.g., Warheit et al.
80
), and (ii) the accessibility to some properties
requiring sophisticated and expensive methods or techniques, which are not
standardized and thus often lead to incomparable results across studies.
11.3.2.1.2 Models of Nanoparticle Releases: Also Many Challenges Left
The general lack of comparable, empirical data has resulted in some research
focusing on the development of modeling approaches for quantifying
releases of nanoparticles across the nanoproduct life cycle. Table 11.6 pro-
vides an overview of these available models, based on a review performed
by Gottschalk and Nowack
74
and the authors' own search.
Table 11.6 shows that all currently existing modeling approaches (i) adopt a
system-oriented perspective, using material flow analysis (MFA) to typically
encompass a whole defined region or market system; (ii) have the implicit
purpose of preparing the ground for assessing outdoor exposure, primarily
of aquatic ecosystems; and (iii) restrain their scope to selected nanoproducts
in a truncated life cycle perspective, with often an exclusive focus on the use
stage (exceptions made of Mueller and Nowack
84
and Gottschalk et al.
86,87
).
Therefore, although these approaches contribute to provide an overarching
overview of releases of nanoparticles to the environment, they do not allow
reaching process-specific release data that could be useful inputs for com-
prehensive LCAs. Also, they do not allow carrying information on the dif-
ferent properties of the released nanoparticles, which may vary through the
nanoproduct life cycle.
