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Nanoparticles – billionths of metre in dimensions - produced by nanotechnology
have unusual properties not found in the bulk material, which can be exploited
in numerous applications such as biosensing, electronics, photovoltaics, diagnostics
and drug delivery. However, research within the past few years has turned
up a range of potential health hazards, which has given birth to the new discipline
Researchers in the University of Texas in the United
States found that carbon nanotubes squirted into the trachea of mice caused
serious inflammation of the lungs and granulomas (tumour-like nodules of
bloated white blood cells in the lining of the lungs), and five of the nine
mice treated with the higher dose died (“Nanotubes highly toxic”, SiS
21) [1, 2].
In a similar experiment carried out at the National
Institute of Occupational Safety and Health in Morgantown, West Virginia,
in the Unites States, researchers not only found granulomas in the lungs,
but also damage to mitochondrial DNA in the heart and the aortic artery,
and substantial oxidative damage, both foreshadowing atherosclerosis (hardening
of the arteries) .
In yet another similar experiment in Tottori University,
Japan, researchers showed that within a minute of contacting the mice’s
tiniest airways, carbon nanotubes began to burrow through gaps between the
surface lining cells and into the blood capillaries, where the negatively
charged nanoparticles latched onto the normally positively charged red blood
cells surface, thereby potentially causing the red blood cells to clump
and the blood to clot .
Researchers from the University of Rochester, New
York, reported an increased susceptibility to clotting in rabbits that had
inhaled carbon nanospheres (buckyballs, an isotope of carbon shaped like
a tiny football) .
Buckballs present in water at 0.5 parts per million
were taken up by largemouth bass, which suffered severe brain damage 48
hours later, the extent of damage being 17 times greater than that seen
in controls .
Nanoparticles in the lungs are translocated to the
circulatory system and from there throughout the body, accumulating in the
liver, spleen, and bone marrow .
Nanoparticles inhaled through the nose and air passages
are translocated to the brain through the olfactory nerves, and accumulate
in the brain .
Nanoparticles can enter the body through the skin;
and quantum dots injected into the skin accumulate in lymph nodes with potential
effects on the immune system .
Quantum dots consisting of a core of fluorescent
cadmium selenide, touted as a non-invasive way to image internal body tissues,
break down in the body, releasing cadmium, a toxic heavy metal .
In August 2005, the International Council on Nanotechnology
(ICON) and Rice University’s Center for Biological and environmental Nanotechnology
(CBEN) launched an online database of scientific findings related to the risks
as well as benefits of nanotechnology  (http://icon.rice.edu/research.cfm).
Searches using common key words such as “quantum dots” and “nanospheres” gave
zero returns in September 2005, which shows it is far from adequate and hence
could well be misleading.