Emissions from Consumer Products Containing Engineered Nanomaterials over Their Lifecycle - Safety of Nanomaterials along Their Lifecycle - page 343

15.3.3 C oatings
Coatings containing ENM represent an important use of ENM in the construction
industry (Lee et al. 2010; Broekhuizen et al. 2011). These coatings can be applied
to glass, metal, or other surfaces. Chabas et al. (2008) have investigated the durabil-
ity of self-cleaning glass coated with nano-TiO 2 . SEM investigations and chemical
analyses on the samples exposed to ambient conditions for 6, 12, and 24 months
showed no evidence of significant weathering of the surfaces or loss of Ti.
Olabarrieta et al. (2012) developed an experimental protocol to simulate the
accelerated aging of photocatalytic coatings under water flow. The influence of
environmental parameters such as the composition of the water matrix or the pres-
ence of UV light was investigated and the release of TiO 2 nanoparticles into water
was studied. TiO 2 emissions as high as 150 µg/L were observed. The release was
enhanced by the presence of NaCl and illumination with UV light. A commercially
available coated glass released in 4 weeks up to 4 mg/m 2 TiO 2 . The authors postu-
late three mechanisms that are involved in TiO 2 emissions (compare also Chapter
14): (1) TiO 2 agglomerates can be stripped off of the coatings by the water flow,
resulting in the release of big TiO 2 agglomerates; (2) dispersion of TiO 2 agglomer-
ates in the presence of NaCl and UV light, resulting in suspended TiO 2 nanopar-
ticles; (3) direct release of TiO 2 nanoparticles from the matrix, also resulting in
suspended TiO 2 nanoparticles.
15.3.4 f ood C ontainers
Food contact materials containing nano-Ag have been widely used in the last years
(Simon et al. 2008). Theoretical calculations show that detectable migration of ENM
will only take place from polymers with low viscosity for ENM with a radius in the
order of 1 nm (Simon et al. 2008). It was also predicted that no appreciable migration
occurs in the case of bigger ENM contained within a polymer with high viscosity.
Several studies are available that experimentally investigated the release and migra-
tion of Ag into water or matrices mimicking foods. Hauri and Niece (2011) measured
Ag release from two types of plastic storage containers into distilled water, tap water,
and acetic acid for up to 2 weeks. The highest observed concentration was 2.6 µg/L
in the acetic acid container. No characterization or size fractionation of the released
Ag was done. Huang et al. (2011) measured release into pure water, acetic acid,
alcohol, and oil simulating solution (hexane) and found releases of up to 4 µg/dm 2 ,
with an increase over time and with increasing temperature. The highest release
was observed for alcohol, followed by acetic acid and water. Electron microscopy
revealed the presence of silver particles with a diameter of 300 nm in the pure water
leachate. Song et al. (2011) performed a similar study and measured Ag release from
plastic material into ethanol and acetic acid at temperatures between 20 and 70°C. In
acetic acid up to 0.6% of the Ag was released after 9 hours, for ethanol up to 0.2%.
No further characterization of the released Ag was performed.
The studies published so far give therefore only very limited evidence for the
release of particulate Ag, they all measured just total release of Ag. Because all stud-
ies found the highest release in acetic acid, it is very likely that the majority of the