One in three New Statesman readers recently affirmed that we should fear nanotechnology. If they had all read Michael Crichton's bestselling Prey you can appreciate their position. The book tells of tiny robots, the size of dust grains, devouring every living thing in their path.
The nanotechnology guru K Eric Drexler had already sketched this scenario in his 1986 book Engines of Creation, a vision of robots just a hundred nanometres or so in size that could replicate, assembling copies of themselves by pulling substances apart virtually atom by atom and reorganising these building blocks of matter. A nanometre is a millionth of a millimetre - Drexler's "nanobots" are many times smaller than a bacterium, which is typically about 10,000 nanometres long.
Drexler imagined nanobots doing all kinds of useful things: making new materials, harvesting energy, patching up our damaged cells and killing off cancer cells. But what if they went wrong and started replicating mindlessly? Any substance they got hold of would be converted into more nanobots, creating an undifferentiated mass of microscopic machines or "grey goo". Trees, houses and people would melt before the advancing tide of goo, which would multiply so fast that in theory it would outweigh the earth in less than two days. Small wonder, then, that nanotechnology has the dubious distinction of being the Prince of Wales's latest technological demon.
It is easy to dismiss the prince as ill-informed, but at least he is seeking more reliable sources of information than those on which his worries are based. He apparently became alerted to grey goo by a document from a Canadian environmental body called the ETC Group, which is emerging as the unofficial leader of the nanosceptics. And that lethal sludge is mutating rapidly: ETC has conjured up "green goo", a blend of "living cells and nanomachines". ETC asks: "Will a newly manufactured virus retrofitted with nano-hardware evolve and become problematic?"
Yet governments seem to be welcoming the science of the ultra-small with open arms. US funding for nanotech runs to around $600m; in Japan the spending has leapt to $750m; and the EU has pledged £1bn in the coming financial year. Small science is big business. But nanotech doomsayers are not necessarily just reactionary Luddites. The ETC Group, for instance, is starting to focus its efforts on a valid and even urgent concern: the potential toxicity of nanoparticles.
Nanoparticles are lumps of matter smaller than 1,000 nanometres across - typically, about the same size as a virus. Scientists can now make these minuscule grains to order from all kinds of materials, including polymers and metals. They can act as flashing beacons which allow biologists to track molecules moving around a cell. They could be used to package and deliver drugs into cells in a targeted manner: for example, enter- ing tumour cells but staying out of healthy cells. Nanoparticles made from semiconductors could act as electronic components on super-miniaturised chips.
Nanoparticles have already found their way into commercial products. Nano-sized grains of titanium dioxide, for example, are used in sun creams developed by BASF and L'Oreal. They absorb ultraviolet light but are transparent - so skin needn't look as if it is smeared with chalk.
But when titanium dioxide nanoparticles absorb UV light, they become chemically reactive. This property is exploited in another nanotech product just crossing the threshold of commercialisation: self-cleaning tiles and glass. Here a thin, transparent film of nanoparticles uses the energy of sunlight to burn up dirt stuck to the surface. Might nanoparticle sun creams burn up our cells in the same way, causing cancer-inducing damage? Could other nanoparticles pose asbestos-like hazards if breathed in?
These are reasonable concerns, as Vicki Colvin of the Centre for Biological and Environmental Nanotechnology at Rice University in Houston avers. "I feel that eventually there will be a regulatory component to this industry," she says. But toxicity is a subtle issue which depends, among other things, on the extent of exposure. Just because something can be shown to be toxic doesn't mean it poses a health hazard; the poison is in the dose. Toast contains carcinogens, but it isn't banned. To assess whether nanoparticle sun creams are dangerous requires studies of dosages.
The ETC Group tends to sweep these complexities under the carpet, assuming guilt until innocence is proven - which makes sense only if you have a sound definition of guilt. The group's publications imply, absurdly, that the mere possibility of toxicity warrants an absolute ban not only on commercial products but also on laboratory research using nanoparticles. Yet every undergraduate chemistry lab in the country is stacked with lethal compounds: safe handling is part and parcel of chemical research. And the technological world is full of poisons: every CD player, for instance, contains arsenic. "After all, we're not advising that you eat nanotech stuff," says Richard Smalley, a nanotech pioneer and Nobel laureate at Rice University.
But this does not impress the ETC Group. Along with other pressure groups, it suggests that there is something "unnatural" and uniquely scary about the nanoscale. This is nonsense: it is at the nanoscale that nature does some of its most ingenious work. Nanoscale motors made of protein power the whiplike flagella that allow bacteria to swim. Nanoscale "antenna arrays" in plants gather sunlight for photosynthesis. Nanoscale machinery assembles proteins from the instructions encoded in our genes. Scientists look to these examples of natural nanotechnology for inspiration when attempting to design synthetic nano-machines of their own.
Nano is different in one respect, however, because of quantum mechanics, notorious for its counter-intuitive nature. In the nanoworld, the "classical" physics of our everyday world starts to merge with the quantum physics of the atomic scale. This gives nanoparticles some bizarre properties. For example, the colour of metal and semiconducting nanoparticles depends on their size: crudely speaking, the smaller they get, the bluer they become. This enables scientists to "tune" the colour of nanoparticles used as tiny light bulbs for light-emitting display devices.
From such behaviour, it is easy to suggest that, at the nano- scale, anything might happen - as though the dangers become not only heightened but spookily, unpredictably so. But quantum mechanics is now well understood, and has no hidden demons lying in wait. Others have suggested that nanotech carries unprecedented dangers in its reliance on the manipulation of matter at the atomic scale. But this is nothing more than chemists have been doing for longer than a century; they have simply got steadily better at it. Nanotech looks miraculous because we live in a culture profoundly ignorant about modern chemical science. As Sir Harry Kroto of Sussex University put it in a recent radio debate, "Calm down, it's only chemistry."
Nanoparticle toxicity is perhaps the only sound, scientific concern raised so far. Existing safety regulations do not allow for the possibility that a substance may be harmless on the everyday scale but have altered physical and chemical properties at the nanoscale. This is unsatisfactory: nanoparticles should be treated, from a toxicological point of view, as entirely new chemicals.
The research community is not indifferent to this issue. Colvin's group at Rice, for example, is working with biologists to assess the dangers. "It would be almost amazing if all those materials were as safe as water," she says. "It is a mistake for someone to say nanoparticles are safe, and it is a mistake to say nanoparticles are dangerous. It will depend very much on the specifics."
Yet some of the high-profile fears raised about nanotechnology come from people who find such specifics boring. What about rampaging self-replicating nanobots and grey goo, which led Bill Joy, a chief scientist at Sun Microsystems, to float the idea of a nanotech moratorium in an article in Wired magazine in 2000? What if nanotech is abused by rogue states and terrorists? Even the Astronomer Royal, Sir Martin Rees, has speculated (albeit rather soberly) about a nanotechnological Armageddon in the coming century.
Such concerns say more about human nature than about nanotechnology. These fears loom large not because we are terrified, but because we are fascinated by them. Any nanotech researcher will tell you that assessing the prospects of this field on the basis of grey goo is like basing predictions of the impact of space travel on Star Trek. No one has the faintest idea how to make a replicating nanobot. "The nearest we can get to a self-replicating machine such as a mosquito is a helicopter," says Kroto - that is, big, cumbersome and not self-replicating at all. The assembly-line approach to nanotechnology on which Drexler's grey goo idea was based, in which nanoscale robotic arms pick up and manipulate molecular fragments like so many factory components, is sheer fiction. Even Drexler no longer rates grey goo as an important concern for nanotechnology.
And the flaw in the idea that nanotechnology could become an instrument of terrorism should be obvious after 11 September: terrorists do not need cutting-edge technology. Even if they could access it, it is probably more trouble than it is worth.
Chimeric fears like this could hinder the emergence of nanotechnology, but they also risk diverting attention from the real issues. Greenpeace has raised a raft of pertinent questions about this new science: who is developing it, and for what purpose, and with what mandate, and under what guidelines? Nanotechnology could have tremendous impact on environmentally friendly technologies such as solar cells and fuel cells; but there is also a huge military interest, especially in the United States. Will it benefit developing countries, or will it exacerbate the global technological divide? If its potential in medicine (for tissue regeneration, for example) and information technology is realised, what will be the social and economic impacts?
Such questions are not unique to nanotechnology; they should be asked about any emerging technology. But in general we have failed to do that. Doing so would, for example, force scientists to confront the ethical dilemmas of military research, which delivers so much of their funding, while economists would have to reconsider the notion of unlimited growth and limitless consumption. But we cannot ask such questions while we demonise the nanoworld as a future landscape of fictional terrors.