Biomedical Engineering Reference
In-Depth Information
have entered the environment for centuries; products of the nanotechnology
may follow in a similar manner. For instance, million tons of production of
nanosized TiO
2
(and other NMs in less amounts) will inevitably be accompa-
nied by release into effluents, and one may also expect that accidental spills
during production or transport will become more likely with increased pro-
duction [10]. In addition, manufactured NMs will also enter the environment
by using cosmetics, household products (e.g., cleansing aids, fabrics, washing
machines, toys, etc.), paints (especially on buildings), and as various surface
treatments, such as self-cleansing windows or other surfaces (self-cleaning
condensers in air conditioners). The wear and tear of NM-containing objects
by natural erosion processes will result in transfer into the atmosphere (NMs
becoming airborne), in which they are either subsequently settled down or
removed by rain and transported by storm water. Other sources might be the
effluents of wastes sites (discharge water) where degradation and leaching
of NP-containing objects may occur. In this respect, it is noteworthy to men-
tion that the Wilson Woodrow International Center for Scholars has identi-
fied >1000 consumer products containing NMs or nanotechnology [21]. Of
these products, nanosilver was the most commonly used NM (in 200 items),
mainly as an antimicrobial agent. Finally, various dispersive compounds
such as fuel additives (case of CeO
2
) may contribute to the environmental
bu rden [22].
The potential contamination resulting from leaching of NMs present in
surface coating of buildings has been recently studied [23]. The presence of
TiO
2
in water has been reported earlier (albeit without determination of the
source and concentration of the NP) [35], while a recent study presents the
first evidence that NP incorporated in paints can be transported by facade
runoff and discharged into aquatic systems [23]. Approximately half of the
TiO
2
amount could originate from facades and the larger aggregates could
presumably come from other sources, such as road paints or other types of
coatings. These studies do not cover all forms of transport of man-made NPs
into the environment, but they identify some impacts of nanotechnology on
our environment. In fact, using a life cycle model to calculate the predicted
environmental concentrations for nanosilver, nano-Ti, and carbon nanotubes
(CNTs), it is concluded that presence of TiO
2
may be a risk to aquatic life,
based on its low predicted no-effect concentration (PNEC) value and rela-
tively high predicted environmental concentrations (PEC) in the environ-
ment [24].
Other studies have used environmental exposure models to estimate envi-
ronmental concentrations ranges of various NMs used in consumer products
[27]. While the estimated results show relatively low concentrations, it should
be noted that in some countries, industrial uses may multiply these estimates
by many orders of magnitude. For example, a million metric tons of produc-
tion is forecasted for nano-TiO
2
that will eventually completely replace the
m ic r o -TiO
2
production [26]. In a different approach, the PECs were used for
sludge-treated soil in Europe and the United States [27]. It is reported that the
