Biomedical Engineering Reference
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control over the chemical and physical conditions is possible. However, because the
tests are performed on a larger scale the number of replicates or treatments is more
limited. Very often these tests are based on some established standard norms and
thus certain parameters are fixed according to the standard. An example is the use of
ISO washing tests for color fastness that were adapted to investigate release of ENM
from textiles (Geranio et al. 2009). Adaptations had to be made to be able to collect
the released materials and to guarantee sufficiently low levels of silver background.
Although these studies are not directly transferable to the real world, they still allow
at least estimating the order of magnitude of a certain release.
The highest level of relevance for real-world conditions are of course studies per-
formed under normal use of products. This could be to follow weathering and release
of materials from facades painted with nano-paints or washing of clothes in normal
washing machines. However, the main problems are that the exposure conditions are
much less controlled and that especially the collection of the released materials is very
difficult if not even impossible. Consider washing a single nano-T-shirt together with
4 kg of other textiles and then quantifying and characterizing the released materials
in several liters of washing and rinsing liquid, where any eventually released ENM
are diluted to a large extent and occur together with a large variety of other materials
released from the various textiles. In the lab washing machine the solid:water ratio
and the amount of textiles can be optimized to allow detection of released materials
under the chosen analytical methods. However, if performed well, real-world studies
provide of course data that can be directly used for release and exposure scenarios and
are in fact the prime source of data for modeling or risk assessment studies.
Figure 15.1 compares the different types of studies presented here and lists the
possibilities and advantages of them. All studies have their merits and ideally we
would have data from all three levels, allowing us to understand the mechanisms
and have data that can be used for exposure scenarios. In the following sections that
describe release data we will see that for the different nano-products that have been
investigated so far, studies at all three levels have been performed.
Advatages/
disadvantages
Type of release study
To be used for
Mechanistic study
- Batch tests
- Method development
- Conditions can be completely
controlled
- Fast and simple experiments
- Understanding mechanisms
- Simplified systems
Model study
- Method development
- Climate chamber
- Test washing
- Conditions are to some extent
controlled
- Understanding mechanisms
- Release scenarios
Real-world study
- Release scenarios
- Specific trace analytical
methods needed
- Very little control of conditions
- Washing machine
- Outdoor weathering
- Exposure scenarios
- Risk assessment
FIGURE 15.1
Classification of release studies.
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