Environmental Risks of Nanomaterials - Nanotechnologies for Water Environment Applications - page 594

mix (70% Cu 2 O and 30% CuO) to 10 g/l of undiluted latex]. Obviously, the
manufacturing process involves creation of a biocide with properties that differ from
those of the individual input materials. Borkow and Gabbay (2004) found the cleaning
process removed a considerable portion of the copper-containing layer, but the leached
ions are “an insoluble salt” (Christen, 2007). The key issues here are that the insoluble
copper salt may change to a soluble one after it is mixed with sewage. It really doesn't
matter if copper is dissolved or not because a treatment plant is regulated for total copper.
In addition, no information is available on how to ensure proper disposal of used fabrics
at the end of life.
17.2.3 Treatment of Wastes
Metal and metal-oxide NPs (e.g., nanoiron, magnetite, TiO 2 ) have been proposed
for groundwater remediation, wastewater treatment, and removal of toxic contaminants
from air streams. For example, zerovalent iron NPs may be useful in removing
(dehalogenating) chlorinated hydrocarbons from contaminated soil ( Schrick et al., 2004 ).
NPs are used for the controlled release of fungicides in wood to control fungal infection
in soils ( Liu et al., 2003 ). Because of their effective antimicrobial properties and low
toxicity toward mammalian cells, silver NPs have become one of the most commonly
used NMs in consumer products (104 out of 502 products) as of 2007, according to the
Project on Emerging Nanotechnologies at the Woodrom Wilson International Center
(Luoma, 2008). These applications involve delivery of a large amount of NPs, and the
NPs will likely enter into the water system and the wastewater treatment plants.
17.2.4 Uptake
Uptake of NPs by many organisms in the aquatic environment is one of the
major routes (Moore, 2006). It includes direct ingestion or entry across epithelial
boundaries into the water environment. For example, fullerenes are lipophilic and redox
active, and can localize into lipid-rich regions such as cell membranes in vitro
(Oberdörster, 2004). Although fullerenes have very low solubility in water, chemical
and biological modification may change their functionalities and thus make them
dissolve into water and interact with organisms. Fish may uptake the modified C 60 -
fullerene (Howard, 2004). Oberdörster (2004) has demonstrated that colloidal C 60
fullerenes are taken up by the largemouth bass and accumulated into the fish brains.
Eukaryotes (e.g., protists and metazoans) have highly developed processes for the
cellular internalization of nanoscale (100 nm or less) and microscale (100-100,000 nm)
particles, namely endocytosis and phagocytosis, respectively (Na et al., 2003; Panyam
and Labhasetwar, 2003). These processes are integral to key physiological functions
such as intracellular digestion and cellular immunity. However, prokaryotes, like
bacteria, may be largely protected against the uptake of many types of NMs, since they
do not have mechanisms of allowing NMs to cross their cell wall (Klaine et al., 2008).