Safety issues relating to nanomaterials for construction applications - Nanotechnology in Eco-efficient Construction - page 127

environment. Manufactured nanomaterials (MNMs) have already played a
critical role in the medical and electronic fi elds, while the construction
industry has only recently been exploring nanotechnologies for means to
advance traditional construction methods and materials (Zhu et al. , 2004;
Ge and Gao, 2008; Alvarez et al. , 2010). The reason for the implementation
of MNMs in construction lies in the unique physical and chemical proper-
ties of these nanomaterials that can lead to the improvement of numerous
characteristics of construction materials (Tans et al. , 1998; Chan et al. , 2002;
Daniel and Astruc, 2004; Arico et al. , 2005). It is the very same properties
that make nanomaterials so unique that give rise to concern about their
safety (Lee et al. , 2009).
The diversity of MNMs is staggering. On a broad scale MNMs can be
subdivided into classes such as metals, metal oxides, metal chalcogenides
('quantum dots'), fullerenes, single-walled nanotubes (SWNT), multi-walled
nanotubes (MWNT), dendrimers, etc. However, the members of these
classes are typically fi ne-tuned toward their applications by the variation of
properties, such as size, shape, aspect ratio, crystallinity, and surface modi-
fi cations. At this point in time, we are only beginning to understand the
interactions between nanomaterials and biomaterials that would enable us
to rationally predict the positive or negative impact of MNMs. We are learn-
ing about the MNM properties that make an MNM safe or hazardous but
are still forced to test each MNM for its safety profi le empirically for the
foreseeable future while over 1000 MNMs can be already found in con-
sumer products - and the number is rising exponentially.
Traditional in vivo experiments have been performed to evaluate cyto-
toxicity of many MNMs using live organisms such as laboratory mammals.
However, due to the sheer diversity of novel MNMs, this is not only fi nan-
cially unsustainable but time-consuming. More progressive methods
employed are typically based on in vitro approaches or modeling of surface
activity relationships. In vitro approaches allow for greater control over the
experimental parameters, the assay readouts can be better tailored to
answer specifi c questions regarding specifi c toxicity paradigms, and the
process is generally less expensive. Most importantly, in vitro assays are
amenable to high-throughput methodologies, which enable us to logistically
manage the testing of this avalanche of novel MNMs in an effective manner,
provide rapid feedback for the development of novel MNMs by enabling
us to give the go-ahead to suitable MNMs and minimize hazardous MNMs.
Here, we discuss applications of MNMs in construction, review potential
hazards of these materials and give an introduction to high-throughput
nanotoxicology as an effective means toward the safety assessment of
MNMs. We will also review an example of a safe design feature for zinc
nanomaterials and review the current state of a priori prediction of
nanotoxicity.

￿ ￿ ￿ ￿ ￿ ￿