Milk cartons that glow when their contents turn sour. A sinful-tasting, non-fat ice-cream with loads of fibre, protein and nutrients. Programmable soft drinks, even (simply select the flavour and pull the tab).

Such wonders are still being developed, yet engineered nanoparticles are already used across the globe in everything from antibacterial sponges to iron-fortified baby formula.

Nanotechnology is the manipulation of matter at a minuscule scale. A human hair is 80,000 nanometres wide. One nanoparticle is just 100 nanometres wide.

And scientists are utterly fascinated by them. Many use phrases such as "a new toolbox" and "bigger than the industrial revolution" when talking about their potential. The reason is that nanoparticles often behave in weird and wonderful ways compared to bigger particles of the same substance.

Unfortunately, that could make them risky. Who knows how nano-sized iron particles react in humans? Could they slip past the barriers to the brain that keep larger particles out? Or could they be a godsend to iron-deficient women? What's more, food manufacturers don't have to tell consumers or regulators whether their products contain nanoparticles. Nobody can say for sure which, if any, foods in Australia contain engineered nanomaterials (an Epicure investigation found only one brand - a line of body building supplements made by Advanced Sports Nutrition - claiming to contain nanomaterials). There are few rigorous studies of the effects of nanoparticles in humans and most laboratory research examines particles that are inhaled or injected rather than eaten.

Yet early tests have raised concerns.

In 2004, a toxicologist discovered that largemouth bass exposed to water containing carbon-based nanomaterials known as "buckyballs" suffered brain damage. When a chemist exposed lab-grown human skin and liver cells to a much weaker solution, half the cells died. Meanwhile, Cambridge University researchers claim that carbon nanoparticles can penetrate the nucleus of human cells, potentially damaging DNA.

So what? Producers don't sprinkle carbon dust into our breakfast cereals. Isn't it a stretch to use non-food research to condemn nanofood?

Well, that's the point, critics say. Many substances are more toxic at the nano scale - or even become toxic at the nano scale. Why should nanoparticles in food or food packaging be any different?

It's these concerns that have this week prompted Friends of the Earth to call for a moratorium on all nanomaterials in food until nano-specific testing procedures and laws are developed. Nanomaterials should be regulated as new substances, the group insists, even where the properties of larger-scale counterparts are well-known. And mandatory labelling must be introduced.

These calls echo those of a growing number of scientists and consumer action groups around the world. Britain's Royal Society - the world's oldest scientific organisation - has called for nano-sized particles of all chemicals to be treated as new substances and to undergo a full safety assessment, as well as mandatory labelling. In the United States, the Consumers Union wants all nano-scale food ingredients - even those already approved for use as larger particles - classified as new additives. It, too, has called for mandatory labelling.

Yet human health risks are not the only worry. If it becomes easier and cheaper to transport perishable food, we could see a jump in greenhouse gas emissions. And who knows what effect nanoparticles will have once they enter our landfills and waterways?

Paradoxically, the potential of these more absorbable particles to deliver greater nutrition could result in malnutrition.

"If we have a whole range of nutrient-fortified 'superfoods' with virtually no sugar, salt or fat but the same taste and texture, we run the risk of people eating less fresh food," says Georgia Miller, nanotechnology project co-ordinator for Friends of the Earth Australia. "We don't have a perfect understanding of why food is good for us. To think we can pull it apart and put it back at the nano scale and make it healthier - it's a bit deluded, to be honest."

Miller is even more sceptical about claims that nanofood could feed the starving millions. "Genetically engineered food was promoted as being about feeding hungry kids, but the products it delivered were about increasing the herbicide resistance of plants in the north," she says.

"And the products containing nanomaterials on the market right now all target affluent, diet-conscious consumers and pander to their fears about bacteria."

Miller has compiled a global list of such products. Among the 100 or so slimming teas, body building supplements and anti-bacterial chopping boards, it's hard to find anything an African villager would be grateful for.

But do they really contain nanoparticles? With practically no nano-specific regulations anywhere in the world, Miller relied on manufacturers' marketing claims. Legal experts stress that just because a product claims to contain nanomaterials, that's no guarantee that it does. Given the almost insurmountable time and expense required to scientifically test these claims, no one can be sure.

What makes it even harder is that there is no universally accepted definition of a nanoparticle. Most scientists agree that a nanoparticle has at least one dimension - width, length or depth - smaller than 100 nanometres. Others say that particles up to 300 nanometres are essentially the same. Yet at a recent food convention in Europe, a group of manufacturers claimed a true nanoparticle is one with all three dimensions smaller than 100 nanometres. This rubbery definition could allow manufacturers to use nanoparticles when it suits them but deny their presence when it doesn't.

According to Advanced Sports Nutrition's Australian distributor, customers claim fewer stomach upsets compared to other brands and no adverse effects have been reported.

Of course, we only know this because the company trumpets its nano advantage on its website and product packaging. But given the lack of nano-specific laws, we simply don't know which - if any - other foods in Australia contain nanoparticles.

Epicure contacted several major food manufacturers to ask whether they use this technology. Most insist their products don't contain nanomaterials and they have no plans to introduce them. PepsiCo, which Epicure understands has signed a partnership with an Australian company currently developing nanotechnology food applications, refused to comment.

A spokeswoman for Food Standards Australia New Zealand said the regulator, "is not aware, nor has it been made aware . . . of any commercially sold foods in Australia that have been developed using nanotechnology". (Sports supplements are regulated by the Therapeutic Goods Administration, which does not have nano-specific regulations either.) However, the spokeswoman added that, "all food that is sold must be safe".

"All food is safe because it has to be safe?" says Miller. "That's not actually addressing the loopholes."

She's even more critical of a recent speech made by FSANZ's chief executive officer, Steve McCutcheon, to a group of food manufacturers.

"This is one of those cases . . . where the food industry has to help us help it," McCutcheon said. "You know the (nanotechnology). You know what your plans are to introduce it to the food supply. Please take us into your confidence and give us a bit of a heads-up."

"Please," scoffs Miller. "A heads-up? He's basically saying, 'Tell us whether the products are unsafe so we know whether we should ensure their safety'."

A FSANZ spokeswoman defended McCutcheon's comments, claiming they "were designed to encourage the food industry to discuss with FSANZ the use of nanotechnology in foods and to determine if a risk assessment is required to ensure that the food produced is compliant with the code or if an amendment is required," and that "robust regulatory arrangements to ensure the safety of food (are in place)".

For Miller, this only highlights the need for urgent action. Others aren't so sure. "There are some dangers in over-regulation," says Brian Priestly, director of the Australian Centre for Human Health Risk Assessment and chair of the National Health and Medical Research Council Advisory Committee on Nanotechnology and Health. "We could see certain advancements stifled."

And the potential benefits are huge. Scientists have developed a nano-treatment that targets cancer cells in mice but appears to leave surrounding cells unharmed. Others talk of the potential to massively increase the efficiency of solar panels.

"I don't support a moratorium or nano-specific regulations," Priestly says. "When people say we're playing catch-up in terms of the regulation of this technology, there's probably a reasonable basis for that. But I think that governments and regulatory authorities are starting to address those issues. They're responding in an appropriate way."

But perhaps not fast enough. Sam Bruschi, a toxicologist contracted by the Federal Government to review nanotechnology safety issues for the Australian Safety and Compensation Council, insists a moratorium must be imposed immediately.

"One of my major recommendations is that because nanoparticles have inherently different properties to their bulk scale equivalents they should be treated as separate entities in terms of handling and regulation," he says. "My position is quite clear: they should be embargoed until we have the necessary regulations to assess their toxicity - especially in anything you're going to ingest."

The key point, Bruschi insists, is this: no evidence of danger is not the same as proof of safety.

"The fact we're even talking about this at such an early stage of the technology is an indication that humans have got a bit smarter," he says.

"You wouldn't have had this sort of conversation 50 years ago with things like dioxins or pesticides or asbestos. People were just saying, 'Oh, of course they're safe.

"But if you're saying you have no evidence of harm, the next logical question is, 'Have you looked?' ''