Italian scientists suggest that we need a much more detailed toxicological
approach to hazard assessment before judgement regarding the long-term safety
of carbon nanotubes can be made. They outline their results in the International
Journal of Environment and Health.
Although nanotechnology is a relatively new field of research, already there
are claims that its products could be harmful to human health and damaging to
the environment. In particular, concerns have been raised about the safety of
carbon nanotubes, minute hollow fibres of the carbon. Carbon nanotubes are just
one group of materials being developed under the umbrella term of nanotechnology,
which focuses on materials comprising particles between 1 and 100 nanometres
in size. A nanometre is a billionth of a metre.
According to Enrico Bergamaschi of the Department of Clinical Medicine, at
the University of Parma Medical School, carbon nanotubes are among the most
promising nanomaterials, with potential in engineering, molecular electronics
and as drug-delivery agents that could significantly reduce side-effects for
countless medications.
In spite of their innovative properties, the small size of carbon nanotubes
has led some observers to hypothesize that they may have similar detrimental
effects to the sooty particles from vehicle exhausts known as PM10 particulates.
Others suggest that toughness and fibrous nature of carbon nanotubes is reminiscent
of asbestos fibres and follow the same fibre paradigm.
Bergamaschi and colleagues point out that carbon nanotubes are a recent invention
only now finding commercial applications and so clinical and epidemiological
evidence for any long-term effects they may have on human health are entirely
lacking.
The researchers explain that, despite the occasionally exaggerated headlines
seen in the media regarding research studies into the effects of nanotechnology,
their novelty means that no one has yet established whether they represent a
long-term health risk, or whether they can exacerbate certain pre-existing medical
conditions.
"As more of these materials are produced, there is an urgent need to refine
strategies to assess their possible effects on employees who represent the main
exposed population, along with characterizing exposure, so that appropriate
safety regulations can be put in place if needed," says Bergamaschi.
Accepted and standardised tests and models have been set up and are in place
to allow for an evaluation of any new chemical or material against existing
benchmarks and to categorise their associated risk level, the team explains.
However, we don't know whether they also work for such a heterogeneous class
of nanomaterials.
As such, researchers have already demonstrated acute toxic effects caused by
inhalation of carbon nanotubes. Several teams have focused on the way these
substances interact with our cells at the molecular level. Their small size
and surface chemistry and reactivity are the most important factors affecting
their biological interactions and toxicity as they could remain intact in the
lung or, after systemic translocation, in other organs for extended periods.
However, it is common to modify the surface of carbon nanotubes for specific
applications by adding different chemical groups. On one hand this seems to
reduce cytotoxicity, and increase their metabolic clearance, but on the other
doesn't necessarily allow cells to break down such structures more readily.
Nevertheless, the Parma team, having reviewed all the available data, suggests
that in order to meet an acceptable level of certainty regarding the safety
or otherwise of carbon nanotubes, we should combine experimental, clinical and
epidemiological evidence. They add that it is time to set up preventive measures
as well as assess the need to implement periodic health examinations of employees
exposed to carbon nanotubes.
Posted September 16th, 2009
