There is fresh concern that nano-particles found in some Australian sunscreens and cosmetics may be potentially harmful to humans.

Yesterday, manufacturing company Antaria admitted its sunscreen ingredients contained nano-material, despite strenuously denying it for months to the media, its customers and the Australian Stock Exchange.

In 2008 it was revealed that nano-particles of anatase titanium dioxide, found in some sunscreens, were leading to serious problems with Bluescope steel Colorbond roofing.

Anatase titanium dioxide was found to be one of the main factors which caused the premature weathering of the coating on the pre-painted steel roof sheets after they had been handled by workers with sunscreen on their hands.

It has also been shown to cause deterioration of other surface coatings and paints on cars and other consumer products.

The finding raised concerns about how safe such an ingredient might be for use on human skin.

New tests obtained by the ABC show a swag of sunscreen and cosmetic products still contain the material, including a children's sunblock.

The sunscreen industry regulator says there is no need for the ingredient to be banned or labelled, as the weight of evidence suggests such materials in sunscreens do not penetrate human skin.

But Dr Gregory Crocetti from Friends of the Earth has told AM that research shows anatase titanium dioxide is a "nasty ingredient".

"In 2010 researchers looking into anatase titanium dioxide concluded that it was capable of destroying almost any organic matter, and questioned its use in sunscreens," he said.

"Clearly, anatase is a nasty ingredient in any form. Reducing anatase to nano-scale particles increases its ability to generate free radicals, making a potentially dangerous ingredient even worse."

Dermatologist Dr Robert Salmon also queried its safety as a sunscreen ingredient.

"I was quite concerned when I heard these reports," he said.

"Because when it was explained to me what the mechanisms were that were blowing away this paint coating that had a 10-year guarantee, but that was being partially destroyed within 10 weeks, I noted that they were exactly the same mechanisms by which these nano-particles could also cause mutations in DNA if they got somewhere down near live cells."

Technological revolution

Sunscreens have undergone a technological revolution in recent years.

In order to make them transparent, rather than thick and white, the key metal oxide ingredients can now be manufactured into nano-materials which are hundreds of times smaller than a cell.

Some scientists, environment and consumer groups are worried about the lack of evidence on whether they are safe or not.

Dr Salmon says he has doubts about metal oxide nano-materials in sunscreens generally, but that anatase titanium dioxide is the most reactive of them all.

"I think what we need to look at under these circumstances is the precautionary principle - and that basically states that if we want to introduce new technology into sun blocks, the people that are attempting to do that, or the manufacturers, need to prove that they don't cause problems," he said.

"I think most of the anatase that is actually in sunscreen materials is nano.

"It may not be advertised as nano-particles, and until such time as we need to put particle sizes or particle-size ranges on labels on sun blocks in Australia, we're not really going to know when we look at these translucent or transparent sun blocks that are on the market at the moment.

"So I would doubt that very many of them weren't nano-particle."

Sunscreens on test

Curious to know what has changed since 2008, Friends of the Earth commissioned the National Measurement Institute to test eight sunscreen and cosmetic products from Australian shelves.

Six contained anatase titanium dioxide. The results only proved the ingredient to be in nano form in one of those products - Nivea children's sunscreen.

Dr Crocetti says the industry regulator, the Therapeutic Goods Administration (TGA), should follow the European Union and New Zealand and make labelling of nano-particles, as well as safety testing, compulsory.

"If there's a crisis in confidence in sunscreen then the responsibility really falls on our regulator to restore the confidence," he said.

"The Therapeutic Goods Administration is clearly asleep at the wheel on this issue.

"We've had over five years of warnings from different scientists questioning the use of anatase titanium dioxide, particularly in nano form.

"So why have they taken no action?"

A spokeswoman for the TGA told the ABC that Australia has the highest rate of skin cancer in the world, and sunscreen is a vital way to reduce the risk of developing skin cancer.

She says there is currently no evidence to suggest sunscreen products which incorporate nano-technologies pose greater safety risks than other products.

She says the current weight of evidence suggests nano-particles in sunscreen do not reach living skin cells, but instead remain on the surface of the skin.

A CSIRO spokeswoman says the Bluescope Steel study results cannot be extrapolated and that CSIRO scientists are currently conducting further studies, particularly into whether nano-particles can penetrate the skin.

Chris Winder, a professor of toxicology at the Australian Catholic University, says further studies are critical.

"This is a major policy problem - we can't just say, 'well, the big-sized particles are OK, so the small ones are as well'," he said.

"This needs work. From a regulatory perspective, we shouldn't accept both normal-sized particles and nano-particles as having the same health clearances.

"I think the nano-particles may have some toxicity that we're yet to find, so I think we should be prudent and at least warn people that cosmetic products contain nano-particles."

The Cancer Council says it would like to see more research done on the safety of anatase titanium dioxide, but it does not have any health concerns about the use of nano-materials generally in sunscreens.