By Ivan Noble BBC News Online science staff

Terrorists could find the materials to build a dirty radiation bomb in almost any country in the world, the International Atomic Energy Agency (IAEA) warned on Tuesday.

No region is exempt

Mark Gwozdecky IAEA

They could pack radioactive material normally used in industry and medicine around a conventional bomb and use it to contaminate a wide area.

The IAEA says more than 100 countries may not be keeping proper track of what happens to materials like cobalt-60, strontium-90, caesium-137 and iridium-192.

Some of them would not even notice if such materials were stolen, it says.

"It's a global issue. No region is exempt," the agency's Mark Gwozdecky told BBC News Online.

He said 82 IAEA member countries have asked for help to tighten up their radiological monitoring and that another 50 or so countries have not joined the agency.

"It's fair to assume that those countries believe they have no problem at all, despite the fact that they use radiation sources in cancer treatment and in industry," he said.

'Cradle-to-grave' call

The former Soviet Union is an area of particular worry because of the number of radiation sources there which have fallen out of any kind of supervision.

But Western countries, too, report failures to keep track of radiological materials.

Around 70 sources are lost every year in the European Union and hundreds annually in the US, Mr Gwozdecky said.

The IAEA is calling for a "cradle-to-grave" approach to keeping track of radiation sources.

It wants to see adequate security and monitoring during manufacture, transport, use and particularly disposal.

"It's at the end of the life cycle that most of the recorded losses happen," Mr Gwozdecky said.

"Sources have their radiation symbols scrubbed off. They end up on dumps or get dealt with as scrap metal," he said.

The IAEA lists five incidents over the past 15 years where people have been seriously hurt or killed by poor handling of radiation sources:

• three people in one family in China died of radiation exposure in 1992 when one of them unwittingly picked up a lost cobalt-60 source
• 11 border guards fell ill with radiation injuries in the former Soviet republic of Georgia in 1997 after they were exposed to radiation from sources kept in a barracks
• ten people were treated for acute radiation syndrome in Turkey in 1998 after two cobalt-60 sources were sold as scrap metal
• a worker in Peru suffered severe radiation burns in 1999 after he put a source in his pocket
• several hundred people fell ill in Brazil in 1987 when a radiotherapy machine was broken up and left on a dump, where children and adults used caesium powder as body decoration and ate contaminated food.