US scientists warned today that nano-particles could damage DNA and possibly lead to cancer.

Research presented at the 2007 Annual Meeting of the American Association for Cancer Research suggests that nano-engineered materials about a billionth of a metre in size are small enough to penetrate cell membranes yet large enough to cause trouble by interfering with normal cell processes.

The warning came from researchers at the University of Massachusetts who pointed out that such nano-particles are already in use in electronics, cosmetics and chemical manufacturing.

Because of their extremely small size, nano-particles can be difficult to isolate from the larger environment as they are much too small for removal by conventional filtering techniques.

When nano-particles find their way into cancer cells, they can wreak havoc, according to Sara Pacheco, an undergraduate researcher at the University of Massachusetts.

Yet very little is known about how they behave in the environment or how they interact with and affect humans.

"Unfortunately, only a very small portion of research on nano-particles is focused on health and safety risks, or on threats to the environment," said Pacheco.

"I am concerned because so many new nano-particles are being developed and there is little regulation on their manufacture, use and disposal.

"A lot is unknown about nano-particle function, but clearly both size and composition are important. Several studies have shown that smaller particles are more likely to enter cells and cause more toxicity."

Pacheco added that, aside from preventing their release, there are no known ways to prevent the harmful effects of environmental nano-particles.

"Until we understand which types of nano-particles are harmless and which have the potential to be harmful, I think it is prudent to limit their introduction into the environment," she said.