Civil Engineering Reference
In-Depth Information
7.3.3 Demolition, disposal, and recycling
To reduce the consumption of raw MNMs and minimize waste, recycling
and reusing MNMs from construction materials is a safe alternative. Demo-
lition must be controlled and monitored to prevent the release of MNMs
into the environment and community. As with the manufacturing and con-
struction phases, MNMs are capable of becoming airborne during decon-
struction and disposal, posing potential health risks for workers. Dust can
contain MNMs that may be inhaled, ingested, or cause eye irritation.
Prior to demolition, effi cient strategies for collecting the used MNMs
from complex media should be developed so that the unique properties of
the MNMs remain intact and human or environmental exposure is mini-
mized. The MNMs should be characterized and evaluated for their ability
to be reactivated and reused. The ease and costs of extraction should also
be considered in determining the recycling potential of an MNM. The
remaining MNM-containing construction wastes must be disposed of prop-
erly to prevent release and/or transformation of MNMs (Bystrzejewska-
Piotrowska
et al.
, 2009). Each MNM may have special disposal requirements
according to the manufacturer or other regulatory frameworks so a thor-
ough investigation of these procedures should be performed in advance.
Reinforcement barriers in landfi lls are recommended to prevent MNM
leachate from contaminating groundwater and underlying aquifers. Once
the appropriate disposal measures have been taken, continual interception
and remediation methods must be developed to monitor secondary MNM
release into the environment.
7.4
Toxicity profi ling for nanomaterials
Currently, there is considerable debate about how to proceed with engi-
neered nanomaterials (ENM) toxicity testing, with the major discussion
points centering around which toxicological endpoints to screen for, the
rigor of the screening effort, the correct balance of
in vitro
(cellular and
molecular) versus
in vivo
(animal or whole organism) testing, the cost of
the effort, and who should be responsible for overseeing this nano-EHS
development. Attempts to use traditional toxicological assays and models
have resulted in some advancement of our knowledge about nanotoxicol-
ogy but we are still experiencing at times confl icting results and we are far
away from the implementation of a generally accepted screening platform.
While much of the knowledge about MNM toxicity has been generated
using fairly straightforward single read-out plate reader based screening
assays, each chosen assay represents typically only a single specifi c reaction
to a toxic stimulus and thus is of limited predictive value. Since toxic effects
are always a function of the presence or absence of targets for a given toxic
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