Nanotechnology has the potential to generate "enormous" health benefits for the more than five billion people living in the developing world, according to a leading professor of medicine.

However, Dr Peter Singer, senior scientist at the McLaughlin-Rotman Centre for Global Health, and professor of medicine at University of Toronto, warned that it remains to be seen whether novel applications of nanotechnology will deliver on their promise.

"A fundamental problem is that people are not engaged and are not talking to each other," he said. "And business has little incentive to invest in the appropriate nanotechnology research targeted at the developing world."

Dr Singer explained that this is shown by the lack of new drugs for malaria, dengue fever and other diseases that disproportionately affect people in developing countries.

The professor's group in Toronto published a study in 2005 identifying and ranking the 10 nanotechnologies most likely to benefit the developing world in the near future.

Applications related to energy storage, production and conversion, agricultural productivity enhancement, water treatment and remediation, and diagnosis and treatment of diseases topped the list.

Dr Andrew Maynard, chief science advisor for the Project on Emerging Nanotechnologies, said: "Countries like Brazil, India, China and South Africa have significant nanotechnology research initiatives that could be directed towards the particular needs of the poor.

"But if market forces are the only dynamic there is still a danger that small minorities in wealthy nations will benefit from nanotechnology breakthroughs in the health sector, while large majorities, mainly in the developing world, will not."

Dr Piotr Grodzinski, director of the National Cancer Institute's Alliance for Nanotechnology in Cancer, added: "It is my belief that nano-materials and nano-medical devices will play increasingly critical and beneficial roles in improving the way we diagnose, treat and ultimately prevent cancer and other diseases.

"But we face challenges because the complexity of clinical implementation and the treatment cost may cause the gradual, rather than immediate, distribution of these novel yet effective approaches."

Dr Maynard cited one example of a future application in which citizens in the developing world could place contaminated water in inexpensive transparent bottles that would cause the water to be disinfected when placed in direct sunlight.