Case Study Challenges in Human Health Hazard and Risk Assessment of Nanoscale Silver - Safety of Nanomaterials along Their Lifecycle - page 418

(Lee et al. 2006) and biosensors (Lee et al. 2013a). Nanoscale silver has also been
traditionally used to produce yellow glass for windows (Solomon et al. 2007).
To date, little quantitative information about potential exposure resulting from
such nanosilver applications has been published. To test a setup for measuring the
release of nanoparticles in aerosols generated by sprays intended for the consumer
market, an aqueous solution containing silver nanoparticles was used with two types
of spray dispensers provided by the producer (Hagendorfer et al. 2010). It was shown
that a pump spray dispenser did not produce any measurable droplets in the setup,
that is, the generated droplets were presumably too big and heavy to reach the detec-
tor placed 80 cm apart. In contrast, a propellant-based dispenser produced droplets
in the range of 10-300 nm measured by SMPS (Scanning Mobility Particle Sizer,
see Chapter 2) with a range of 10-500 nm. The droplets contained silver nanopar-
ticles (Hagendorfer et al. 2010). Using the same setup, a second study investigated
the release of nanomaterials from four commercially available sprays, two of which
contained silver (Lorenz et al. 2011). One of the silver-containing sprays was a plant
strengthening spray using a pump spray dispenser. As in the earlier study, the solu-
tion contained silver nanoparticles and no droplets were detected at the detector
after pump spraying due to the droplet size. A propellant-based antiperspirant spray
generated nanometer-size droplets and released very low concentrations of silver
likely in its ionic form.
In a different setup using a mannequin head for sampling, amongst 11 tested
sprays, a silver nanoparticle containing spray intended for topical or internal anti-
bacterial use was compared to a spray labeled to contain silver without reference to
nanotechnology intended for topical and nasal application (Nazarenko et al. 2011).
All sprays were propellant-based and generated droplets in the nanometer range and
reaching into the micrometer range. In both silver-containing sprays nanoscale silver
particles were found. Although the primary particles of the nanosilver spray were
of a relatively defined size of 3-65 nm and exhibited some agglomeration, the sil-
ver-containing spray particles were of a broad size distribution around <3-435 nm.
Three commercially available sprays, an antiodor spray for hunters, a disinfectant
spray, and a throat spray, were investigated for nanoparticle content and release in
another study (Quadros and Marr 2011). Nanoparticulate silver was found in the
antiodor spray and in the throat spray. Although nanosize droplets were observed in
the aerosols, only low amounts of silver were released, and were in micrometer scale
agglomerates. In all studies, the propellant-based sprays generated nanosize droplets
that have the ability to carry nanoscale materials into the alveolar region without
the necessity of prior evaporation of the carrier liquid. Thus, the likelihood of expo-
sure and therefore the level of potential risk from nanosilver sprays were linked to
the mode of aerosol generation.
Silver content and release have also been investigated for textiles (see Chapter
15 for details). The emphasis here was mostly on environmental exposure (Benn
and Westerhoff 2008; Lorenz et al. 2012; Pasricha et al. 2012) and lifecycle analysis
(Meyer et al. 2011) rather than human exposure. The release of particles was appar-
ently dependent on the type of fabric and the particle integration into the fabric
because both near complete release in the first three washing cycles and very low
release in several washing cycles have been observed (Benn and Westerhoff 2008;