Anyone who has given a public lecture on nanotechnology has probably been asked the question: “What about the 'grey goo'?” The term, coined by the futurist Eric Drexler back in the 1980s, describes the ever-growing mess of self-replicating nanorobots as they consume the environment and manufacture more of their own kind. For researchers working on the science of the incredibly small, this highly improbable scenario has become a tiresome piece of apocalyptic baggage.

The tiresome may be about to become genuinely threatening, however. Seasoned environmental campaigners, fresh from bloodying the nose of the biotechnology industry over the issue of genetically modified (GM) crops, are now eyeing nanotechnology as their next target (see page 246). Some are even calling for a moratorium on research in the field. And they've cooked up a new goo with which to scare the public: the marriage of nanotechnology and biotechnology to create new forms of life that will behave in unpredictable and uncontrollable ways, threatening natural habitats, biodiversity and human health — 'green goo', as it has been dubbed.

Researchers weary from years of grey-goo scaremongering may throw up their hands at the prospect of a second, similarly improbable form of gunk. Certainly, the discussion at a meeting held in June in Brussels, organized by the Action Group on Erosion Technology and Concentration (ETC) of Winnipeg, Canada, to stoke political opposition to nanotechnology in Europe, veered into the downright ludicrous. One activist argued that potatoes could be constructed from nanorobots, threatening traditional methods of agriculture.

Faced with such patent nonsense, it is easy to dismiss the anti-nanotech campaign as an irrelevant rant — easy, but very unwise. The claims made by groups such as ETC may at times appear irrational, but that doesn't mean they won't have resonance with the public. Many campaigners against biotech and nanotech aren't concerned so much about the specific dangers of the two technologies as about the general environmental and social consequences of advanced technologies when placed in the hands of multinational corporations. Many ordinary citizens, and some scientists, have similar misgivings about this trend towards economic techno-globalization. As a result, groups such as ETC may gain a sympathetic ear.

Public concern

What's more, the European experience with GM crops has shown that environmental campaigners are adept at building from vague public misgivings to whip up a storm of protest, even if their arguments rest on shaky scientific ground. In Britain, for instance, where 'mad cow disease' had fed distrust of official assurances about food safety, green campaigners in 1999 skilfully exploited a study that purported to show that rats fed GM potatoes suffered health problems. The research was deeply flawed, but the misleading message that GM food can kill touched a public nerve in a way that the most thorough investigation into the effects of GM agriculture on farmland biodiversity — an issue of genuine scientific controversy — never could.

Many of the activists now calling for strict controls on nanotechnology are veterans of the GM crop wars. ETC, for instance, was formerly known as the Rural Advancement Foundation International, which enjoyed considerable success in its efforts to portray Monsanto and other agribiotech companies as enemies of the developing world's small-scale farmers. In making an explicit link with agribiotech by deploying its green-goo scenario, ETC may succeed in transferring public concerns about GM crops to nanotechnology, even though the issues involved are different.

How should those working on nanoscale science respond? Simply dismissing the claims of ETC and its allies out of hand, and arguing that nanotechnology poses no conceivable hazards, will do little to win hearts and minds. Many people remember similar assurances from the past: that mad cow disease posed no threat to human health, and that transgenes would not find their way from GM crops into wild relatives, for example.

Honest debate

Another tactic, already being used by some researchers, is to argue that there's nothing really new about nanotechnology: it's simply an extension of existing research in chemistry, materials science, physics and engineering. This is also likely to fail because nanotechnologists — or, at least, their official spokespeople — have spent the past few years telling the public just the opposite. New results from the field of nanoscale science are paraded into the media spotlight almost daily, each allegedly capable of curing disease, cleansing the environment, or otherwise extending peace and prosperity. Such hype ensures that nobody will believe the message that nanotech is old news. And if the technology is capable of such wonders, people may muse, the chances are that it can probably do bad things as well.

So what can researchers do to address public concerns about nanotechnology? First, don't panic. The European backlash against GM crops provides a gloomy backdrop, but the conditions for the storm were created by a spectacular own goal by the US biotechnology industry. The decision not to segregate exports of soya beans into GM and non-GM batches enraged European public opinion by denying consumer choice. Such mistakes don't have to be repeated.

Second, scientists should engage the public in honest debate about the potential risks posed by nanotechnology, and how they can be managed. One of the rallying calls of the anti-nanotech campaign is that too little is being done to address the toxicity of engineered nanoparticles. According to preliminary studies, nanoparticles can disperse through the environment and may do some harm inside the body. Scientists should start thinking about how to limit people's exposure to them.

More research into the risks posed by nanoparticles is warranted, and the findings must be shared with the public. At the same time, researchers should engage in debate about the understandable fear that lies behind green goo — that new technologies can radically alter our unstable world. In doing so, they need to counter the hype currently being deployed in generous measure by both opponents and proponents of nanotechnology. The challenge is to convey the possibilities and risks of this new science without painting it as a panacea or a plague.