Case Study Paints and Lacquers with Silica Nanoparticles - Safety of Nanomaterials along Their Lifecycle - page 387

delivery (Knopp et al. 2009; Mamaeva et al. 2013; Tang and Cheng 2013). However,
the hazard of MN may be different from that of the comparable bulk material. In the
following sections, we summarize some findings from in vivo studies on the toxicity of
silica MN relevant for paints and lacquers as well as the few studies available on paint
dust particles generated by sanding of paints and lacquers added silica MN.
17.4.1 i n v ivo t oxiCity of m anufaCtured n anosiliCa
As listed earlier, the types of silica used in paints and lacquers comprise fumed and
precipitated synthetic amorphous silica, colloidal silica, surface-treated derivates,
and doped silica. Several in vivo toxicological studies of pure amorphous silica
nanoparticles have been recently published (reviewed in Fruijtier-Poelloth 2012).
Based on this review it can be concluded that silica has inflammatory properties but
none of the reported studies detected genotoxic or carcinogenic effects in animal
studies. To exemplify the current developments, a few recent publications on the
toxicity of silica are described in greater detail as follows.
Brown et al. (2014) studied the effects 24 h after intratracheal instillation of neu-
tral and positively (NH 2 ) charged 50 and 200 nm-size silica in Male Sprague Dawley
rats (30 µg/rat). The silica was dispersed and dosed in different media, including
saline, 0.2% BSA water, and 0.2% rat lung lining fluids. There was a statistically
significant higher pulmonary neutrophil influx in rats instilled with 50 nm-size silica
compared with 200 nm-size silica when dispersed in saline and BSA, but not when
dispersed in lung lining fluids (see Table 17.2 later in this chapter).
Saber et al. (2012a) tested the toxicity of two specific paint and binder-relevant
silica nanoparticles (Bindzil CC30, Akzo Nobel Chemicals and Axilat LS5000, and
Hexion Specialty Chemicals B.V.). DNA damaging activity and inflammogenicity
(pulmonary cell composition and mRNAs) were determined 24 h after intratracheal
instillation of a single dose of 54 µg in mice (see Table 17.2 later in this chapter).
Instillation of Axilat increased the pulmonary influx of neutrophils compared to con-
trol animals. Bindzil CC30 did not induce inflammation at the tested dose and none
of the nanosilicas were DNA damaging tested by the comet assay 24 h after exposure.
As shown in Table 17.1, the MN often have more complex chemical composition
than silica alone due to different surface treatments. In the studies of Saber and col-
leagues, the surface modifications did not appear to add toxicity to the nanosilica.
Similar observations have been made as part of the German nanoGEM project from
which first results are presented in Chapter 8 (Hahn et al. ibid). In this study, three pure
nanosilica and three surface-modified silica denoted SiO 2 .naked (SiO 2 Levasil ® 200
nanoparticles), SiO 2 .PEG, SiO 2 .amino, or SiO 2 .phosphate, respectively, were tested in
vivo for inflammation, genotoxicity, and adjuvant effects. Immediately after, as well
as three weeks after, five consecutive days of 6 h exposure to 50 mg/m 3 electrosprayed
nanosilica using a male Wistar rat inhalation model, significant inflammatory effects
(neutrophil influx) were observed only for the SiO 2 .naked. The allergy tests, how-
ever, showed significant adjuvant effects of both SiO 2 .naked and SiO 2 .PEG, but no
significant effect of the SiO 2 .amino or SiO 2 .phosphate, after single dose intratracheal
instillation of 50 µg in mice and subsequent OVA-albumin inhalation challenge. In
other cases, however, surface modifications may increase the toxicity; for example,