Page 416 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

396 13 Nanoaerosol

improvement of our quality of life. Many different types of nanosized drugs have
been developed and some of them can be aerosolized and delivered by inhalation.
Respiratory nanomedicine delivery benefits a patient due to high drug deposition in
central and peripheral regions of the lungs [7]. However, human respiratory systems
did not seem to be effective in capturing nanoaerosol particles smaller than 40 nm [23].
Drug delivery systems for nanoaerosol are believed to have potential to significantly
reduce extrathoracic depositional drug loss [7]. Dosing effect can be improved by
charging the particles. Manufacturing cylindrical or tubular shaped nanoaerosol drugs
may also help since their actual aerodynamic diameters are increased to micron range
and tend to travel only one way into the human respiratory system. On the other hand,
manufacturing sub-10 nanoaerosol-based drugs and associated delivery devices are
challenging because they agglomerate easily at high concentrations.
Another example is the wide use of nano-silver spray as a disinfectant. During
the short life of nanoaerosol after spraying, high dose exposure could result in acute
+
or chronic health effects. The mechanisms of toxicity of silver ions (Ag ) are well
known, but little is known about toxicity nano-silver induced to living organisms.
In addition, limited data available has shown that other potentially hazardous and
toxic materials are involved in the product and the disinfectant spray could also
have negative impacts on the environment and human health.
Nanotechnology market keeps increasing in the past decade to a level of the
order of hundreds billion US dollars, according to a report of European Agency for
Safety and Health at Work [5]. New market opportunities lead to growing concerns
regarding potential risks to the environment and health of human beings. In addition
to the safety risk of explosion, some experts suspect that nanomaterials affect health
more than microscale materials. At the workplace, workers can be exposed during
the production process, use of nanomaterials, transport, storage or waste treatment.
Nanomaterials might also have negative impact on the environment by water and
solid contamination, causing indirect impact on people’s health. As illustrated in
Fig. 13.1, nanoaerosol emitted and formed in the atmosphere eventually falls down
to the ground with precipitation. Many experts in nanotechnology believe that it is
the next industrial revolution. On the other hand, new technologies come with new
risks, which are discovered often later than their benefits.

13.2 Exposure to Nanoaerosol

While the society is enjoying the benefits and excitement brought by nanotechnology,
some experts are concerned about its negative impact on human health and the envi-
ronment. In addition to the nanoaerosol produced in nature and by combustion, recent
rapid advances in nanotechnology have outpaced the risk assessment and government
regulations in this industry. Nanoaerosol can be more toxic than larger ones of the
same material because of their small size, large surface area and great diffusivity. Long-
term exposure to nanoaerosol may cause ischemic heart disease, cardiovascular dis-
eases, stroke, chronic bronchitis, asthma, and respiratory tract infections [14].