Environmental Risks of Nanomaterials - Nanotechnologies for Water Environment Applications - page 593

products containing NMs is another important route. However, limited data and
guidelines are available for handling nanoparticles in occupational settings as well as
research laboratories (Wiesner et al., 2006). Research on different companies that
manufacture NMs indicates that the companies are aware of health and environmental
effects of NPs, but there are knowledge gaps on what these effects will be. Inhalation is
seen as the most potent point of entry where the nanoparticles could cause respiratory
and cardiovascular diseases. However, most of the manufacturers do not believe the NPs
they produce are problematic (Helland, 2004).
The effluent from NM manufacturing facilities may contain a variety of NPs.
These NPs enter the environment through intentional and unintentional releases such as
atmospheric emissions. The NM releases may come from spillages associated with the
transportation of manufactured NMs from production facilities to other manufacturing
sites. Long-range atmospheric transport, as well as transport in saturated and unsaturated
regions in the subsurface, also possibly result in transfer of NMs to the water. During
manufacturing, NMs are most likely released into the atmosphere, and are finally
deposited on land and water bodies. NMs in solid wastes, wastewater effluents, or
accidental spillages can be transported to aquatic systems by wind or rainwater runoff.
Because suspended sediment particles largely sequester and transport contaminants over
significant distances, the hydrodynamic and morphological characteristics of water body
will also determine the distribution of bound NPs (Smedes, 1994).
17.2.2 Treatment of Drinking Water
NMs have promising applications for removal of chemical contaminants and
bacteria from drinking water. This should have a positive health benefit to humans from
the stand point of water quality. For example, iron oxide NPs can be used in
ultrafiltration technology for drinking water treatment (Karnik et al., 2005), and iron
sulfide NPs are used to remove organochlorine pesticides from drinking water supplies
(Paknikar et al., 2005). Nanosorbents are used to remove arsenic from drinking water
(Sylvester et al., 2007). However, few address the possible risk of NMs escaping from
the drinking water treatment media, such as water filters coated with NPs. A technique
of using Ag NPs coated onto polyurethane foam is a low cost and effective way of
killing bacteria, providing an effective antimicrobial means for water treatment (Jain and
Pradeep, 2005). Although Ag NPs are stable on the foam and the risk of human exposure
to the Ag NPs is minimal, it is highly likely that Ag NMs will be released into the water
after a prolonged period of use.
Recently, a line of fabric products impregnated with copper-based biocides was
made available for use and sale to consumers nationwide in stores and over the Internet.
In general, these copper-containing fabric products are made by depositing the copper on
the clothing fibers via a chemical plating reaction [e.g., adding a cuprous oxide powder