11/07/2008

Tiny, "Barely There" Particles Could Pose Big Health Risks

Preliminary study says carbon nanotubes look and act like asbestos fibres.

Imagine tiny wiry tubes that are about 50,000 times thinner than a single
strand of hair, and stronger than steel. These tiny tubes made of rolled up
sheets of carbon hexagons are better known as carbon nanotubes. They look and
act much like asbestos, according to a recent preliminary study, raising
concerns with researchers.

Nanotechnology involves working at the nanometre scale of small numbers of
atoms to produce materials and devices. It's at the forefront of research and
technology development - and carbon nanotubes are the building blocks. Most
carbon nanotubes are made from sheets of graphite about a nanometre, or one
billionth of a metre wide, and formed into cylinders. Nanotubes are important
in electrical research and the next-generation of computer chips and are also
being developed for use in new drugs, batteries and other products. However
some scientists and environmentalists are concerned that they could pose hidden
dangers.

A recent study showed that inhaling carbon nanotubes in sufficient quantities
could be as harmful as breathing in asbestos. During the study, led by the
Queen's Medical Research Institute at the University of Edinburgh/MRC Center
for Inflammation Research in Scotland, scientists observed that the long,
needle-like fibre shape of carbon nanotubes look and behave like asbestos
fibres. The researchers reached their conclusions after they introduced the
needle-thin nanotubes into the abdominal cavities of lab mice and found that
the inside lining of the animals' body cavities became inflamed and formed
lesions.

This resemblance raises the concern that the nanotubes may cause illness
similar to that linked to asbestos. Asbestos can cause mesothelioma, a deadly
cancer of the membrane lining the body's internal organs (especially the lungs)
that can appear 30 to 40 years after exposure. Most people who develop
mesothelioma have worked on jobs where they inhaled asbestos particles.

Study co-author Ken Donaldson stated, "We still don't know whether carbon
nanotubes will become airborne and be inhaled, or whether, if they do reach the
lungs, they can work their way to the sensitive outer lining. But if they do
get there in sufficient quantity, there is a chance that some people will
develop cancer-perhaps decades after breathing the stuff."

Donaldson also commented on what he deemed to be the upside of the findings.
"Short or curly carbon nanotubes did not behave like asbestos, and by knowing
the possible dangers of long, thin carbon nanotubes, we can work to control
them. It's a good news story, not a bad one. It shows that carbon nanotubes and
their products could be made to be safe."

But Donaldson added that the present study only tested for fibre-like behaviour
and did not discount the potential for carbon nanotubes to damage the lungs in
other ways. "More research is still needed if we are to understand how to use
these materials as safely as possible," he notes.

It is estimated that the market for carbon nanotubes will continue to grow and
could easily reach 1-2 billion dollars annually within the next seven years,
according to studies.

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AplusA-online.de - Source: Canadian Centre for Occupational Health and Safety