Case Study Paints and Lacquers with Silica Nanoparticles - Safety of Nanomaterials along Their Lifecycle - page 384

paint mixers in two different paint manufacturing companies (Koponen and Jensen
2014). Silica (SIPERNAT ® produced by Evonik Degussa GmbH) was an ingredient
in one of the paints. The product was not specified as a MN, but online monitoring
with a Fast Mobility Particle Sizer (TSI Inc.) showed that the dust was dominated by
ca. 200 nm-size particles, which we often observe in dust from powder MN.
The near-field particle concentration around the worker increased by ca. 20,000 cm −3
during pouring and wet mixing seven 25 kg bags of the SIPERNAT product. The daily
personal PM 1 (mass concentration of particles ≤1 µm aerodynamic diameter) exposure
level of the worker was 0.65 mg/m 3 . The specific contribution from the SIPERNAT to
the mass concentration was not quantified, but from the online exposure data and elec-
tron microscopy, the exposure was dominated by dust from handling 280 kg talc and
2,675 kg pigment TiO 2 (Koponen and Jensen 2014).
17.3.2 P oWder h andling and d ustiness
In addition to workplace measurements, assessment of the exposure potential can be
made from powder dustiness data on silica powders. A dustiness standard, EN15051,
has been established and contains two different methods: a rotating drum and a
continuous drop dustiness tester. However, a range of other different methods for
dustiness testing exist and have been developed recently for nanopowders (Evans
et al. 2013; O'Shaughnessy et al. 2012; Tsai et al. 2012). Unfortunately, at this point
in time, it is not possible to compare the quantitative levels of dust release between
these different methods.
Six different silica MN powders have been studied using a miniaturized EN15051
rotating drum dustiness tester (Schneider et al. 2008). The results show a wide varia-
tion depending on the product. The least dusty nanosilica was the OECD WPMNM
sample NM-202 (91 ± 11 mg/kg respirable dust) and the most NM-204 (2,058 mg/kg
respirable dust) (Rasmussen et al. 2013). Following the dustiness categorization in
the EN15051 standard, all the products had high dustiness levels.
17.3.3 a Brasion
A small number of groups are currently investigating the potential release of nanoma-
terials from surface coatings such as paints and lacquers during various abrasion pro-
cesses (e.g., sanding and Taber abrasion). Only a few such studies have been carried
out on surface coatings with silica nanoparticles. These were conducted in the Danish
NanoKem study, which was conducted in collaboration with the Danish Coatings
and Adhesives Association (Koponen et al. 2011). Two nanosilica types were inves-
tigated, namely silica (Bindzil CC30, code: Bindzil) and nanosilica-reinforced acry-
late (NANOCRYL XP 21/0768, code: Nanocryl). A binder containing silica-acrylate
(Axilat™ Ultrafine LS500, code: Axilat) was also available, but without reference
binder and is not further discussed in this section. Other test materials included
powders of a pigment size TiO 2 (RDI-S, code: FineTiO 2 ) and seven NM (UV-Titan
L181, code: NanoTiO 2 ), photocatalytic TiO 2 (W2730X, code: PhotocatTiO 2 ), kaolinite
(ASP-G90, code: Kaolin), and a carbon black (Flammruss 101, code: FineCB). The
paint and lacquer matrices tested in NanoKem were: polyvinyl acetate paint (PVA),