Nanoparticles for water and desalination - how safe are they?
The potential dangers from the use of engineered nanoparticles, such as nanotubes, metal oxides or nanodots, some of which form the basis of new solutions for desalination and water treatment, are outlined in a new European Union publication.The Science for Environment Policy Newsletter, produced by the Directorate General for the Environment, published a special edition on 22 April 2009 on Nanomaterials. In the forward to the newsletter, Prof Kenneth Donaldson, Professor of Respiratory Toxicology, ELEGI Colt Laboratory, University of Edinburgh, states, "The potential impacts of manufactured nanoparticles on health are of particular concern."
Under a heading "Are carbon nanotubes the new asbestos?", the newsletter refers to Polish research conducted on mice, which indicated that a specific type of carbon nanotube does have asbestos-like effects, although further research was needed to assess whether this was also the case for humans.
Carbon nanotubes are cylindrical carbon molecules, typically a few nanometres in diameter. They are very strong, conduct heat efficiently and have unique electrical properties that make them potentially useful in many fields.
Two examples of nanotechnology use with water treatment membranes are: nanostructured filters, where either carbon nanotubes or nanocapillary arrays provide the basis for nanofiltration; and nanoreactive membranes, where functionalized nanoparticles aid the filtration process.
The Polish researchers expressed concerns about the potential health hazards of nanotubes due to their superficial resemblance to asbestos. Exposure to asbestos causes a specific type of cancer called mesothelioma, and there are concerns that nanotubes may also cause this cancer.
Their results revealed that only long multi-walled carbon nanotubes show asbestos-like behaviour. However, the authors point out that their test was specific for fibres and that nanocarbon in the form of particles could be harmful in ways that are not addressed in their study.
"This flags up the importance of choosing the correct method of evaluating toxicity," warns the EU newsletter. It goes on to look at a Finnish study, which has found that two commonly manufactured nanomaterials can damage human DNA, highlighting the need to evaluate the risks they might pose and design appropriate safety tests.
The scientists treated cultured human lung cells with nanotubes and graphite nanofibres, and observed changes in the DNA. Both the nanomaterials caused DNA damage in the cultured cells, and there was a direct link between the dose of carbon nanotubes and the amount of damage.
Other articles in the newsletter highlight research on effects on the environment from engineered nanoparticles and how they could be released into it. Prof Donaldson concludes:
"The issues surrounding engineered nanomaterials are recognised as important by the European Commission. The nanotechnology action plan (2005-2009) has provided strong support for research in this area.
"However, more research is needed, especially in the areas of food and exposure assessment. To allow nanotechnology to develop to its full potential, research into the risks of nanotechnology must continue alongside development of nanotechnology itself to inform future policy and maintain European industrial competitiveness."