Case Studies in the Human Respiratory System - Computational Fluid and Particle Dynamics in the Human Respiratory System - page 254

Fig. 8.18 Electron
microscope image Amosite
asbestos. (U.S. Geological
Survey—www.usgs.gov)

are not free from toxic properties. The levels of toxicity vary, depending on the fibre
length and its biopersistence in the lungs (Lippman 1990; Timbrell 1982).

8.3.1.4 Diesel Fumes, Vapours, Smoke and Nano Particles

The physiological effects of air pollution consisting of very fine particles, such as the
exhaust fumes from diesel engines, vapours and smoke, have a detrimental impact
on the health of the respiratory system. Chronic inhalation of diesel fumes leads to
the development of cough and sputum, known as chronic bronchitis (Morgan et al.
1997), and interferes with brain functioning and information processing (Crüts et al.
2008) which is a serious problem in highly urbanised, busy cities.
Recent advances in nanotechnology have seen the manufacture of engineered
nanoparticles for many commercial and medical applications such as targeted drug
delivery and gene therapy. Engineered nanoparticles can exhibit a large surface area
to size ratio leading to greater biologic activity. This increased biologic activity can
be desirable. For example, magnetic nanoparticles can be used for magnetic res-
onance imaging (MRI), targeted drug and gene delivery, tissue engineering, cell
tracking and bioseparation (Gupta and Gupta 2005; McCarthy et al. 2007). However
the increased biologic activity can also have adverse repercussions due to toxicity,
induction of oxidative stress or cellular dysfunction (Oberdörster et al. 2005). Trans-
port of nanoparticles is mainly attributed to Brownian motion which is the random
movement of the gas or liquid molecules impacting on small nanoparticles. The in-
stantaneous momentum imparted to the particle varies in a random fashion which
causes the particle to move on an erratic path known as Brownian motion.
Fumes, vapours, and smoke are characteristically small, existing in the submi-
cron range. Technically speaking, nanoparticles are considered as having a diameter
< 10 nm; ultrafine particles have diameters < 10-100 nm; and submicron particles
are any particle less than 1

μ m. The deposition mechanism of nanoparticles will be