Nanotechnology has been hailed as a potential cure for cancer and environmental ills. But could it become the asbestos of the 21st century?
Researchers and futurists believe that nanotechnology could transform everything from healthcare and manufacturing to environmental clean-ups and space travel.
Many of the worst problems threatening us, they say, could be eradicated this century.
Cancer cells could be destroyed by tiny silicon combs; "nanobots" could clear blocked blood vessels. Hydrogen-based fuel cells using "nanotubes" could allow cars to travel 8000km on a full tank. Minute solar cells in building facades and on road surfaces would produce cheap energy.
Nanoparticles might detoxify petrochemical waste. There could be a new industrial revolution as atoms are assembled into useful new products.
But at scales of a millionth of a millimetre, materials can develop unusual and unpredictable properties, leading to concerns about risks to health and the environment.
Some experts are calling for a moratorium on nanotechnology, saying that ultra-fine particles created could prove deadly.
Bob Phelps, director of the Australian lobby group GeneEthics, says: "Each type of nanoparticle may be as deadly as asbestos."
In his opinion, 25 per cent of the investment in nanotechnology should be spent on researching risks.
Friends of the Earth estimates that, in Australia, 300,000 workers in refining and welding could be exposed to nanoparticles; a further 33,000 may be exposed through handling powders, mainly in the pharmaceutical and cosmetics industries.
Like Phelps, Friends of the Earth supports a moratorium on research, development and manufacture of synthetic nanoparticles until regulations are developed.
"This could prevent huge human and financial costs and compensation claims from injured persons, as has been seen with asbestos," it told an Australian senate committee inquiry.
Similar calls are being heard in America. At an Environmental Protection Agency nanotechnology workshop in October, Mihail Rocco, co-chair of the National Science and Technology Council, declared: "Federal agencies lack methods to monitor environmental releases of nanoparticles. Yet they can go to the brain and potentially cause damage."
Another presentation explained that nanoparticles can pass through the skin, causing inflammation and other potential hazards. Products made to be applied to the skin, such as sunscreen and baby products include nanoparticles.
There is concern in Britain about the possible dangers. Last year, the Government commissioned a report by the Royal Society and Royal Academy of Engineering into the new science. It concluded that there were no significant concerns, but more research was needed.
The Department for Environment, Food and Rural Affairs announced last month that it would spend 5 million ($12.2 million) investigating the health risks of nanotechnology. Researchers will look at how nanoparticles travel through the environment and human body, and how they might affect health.
Its approach is understated. But a report last year from the Switzerland-based reinsurer Swiss Re makes a far more urgent case. It states that, once in the blood, "nanoparticles can move practically unhindered through the entire body". During pregnancy, nanoparticles would be likely to enter the foetus.
Nanoparticles, it continued, may harm living tissue in at least two ways: through chemical reactivity, or by damaging phagocytes, or scavenger cells. Also, nanoparticles may disrupt the immune system, cause allergic reactions, interfere with cell communications, or alter enzyme exchanges.
Water filters will not remove nanoparticles, and they could perhaps penetrate plant roots and enter the food chain.
The American technology commentator Jeff Harrow believes that we should resign ourselves to nanotechnology.
"Even if some Governments were to ban or restrict nanotech research," he says, "others would encourage it through enhanced education and funding to help them gain a nano-edge."
What is it?
A technique that creates small materials at the scale of molecules by manipulating single atoms.
What can it do?
There are many claims - including curing cancer, cleaning up the environment and developing hydrogen-powered cars.