Nuclear pollutant found in seafood caught off Wales

Vast quantities of a nuclear pollutant have been discovered in seafood caught off the Welsh coast.

The National Radiation Protection Board (NRPB) examined the level of risk presented by tritium after fish caught near a Cardiff factory were found to contain levels of the pollutant hundreds of times greater than expected.

Tritium does not pose an "external" radiation threat because the particles released when the atoms decay have so little energy that they can be stopped by a layer of water less than half a millimetre (1/50th of an inch) thick.

But if water containing tritium atoms is drunk, a cancer-causing change in a cell's DNA could theoretically take place.

Medical experts cast doubts on the safety of eating fish caught near centres of tritium pollution.

"The finding could have significant implications for people who eat a lot of fish from around the Cardiff plant," Barrie Lambert, a radiation expert from St Bartholomew's hospital in London, told the New Scientist magazine.

Tritium, an isotope of hydrogen produced as a by-product of some nuclear reactions, is used as a radiation source in exit signs and even some luminous watches. The tritium is surrounded by materials that give off light when hit by the beta particles produced by its decay.

Vast quantities of tritium were released by hydrogen bomb tests in the 1960s, and more could be produced if scientists develop nuclear fusion as a power source.

But John Harrison, a NRPB spokesman, said the risk was small. "People should not be particularly concerned about this," he said.