Dr Neil Bruce says the clean-up could take just a few years

British scientists have genetically-engineered plants to produce a bacterial enzyme which breaks down explosives such as TNT and dinitroglycerin.

"Effectively they use the explosives as a food source," says Dr Neil Bruce of Cambridge University's Institute of Biotechnology, who lead the research.

"The bacteria would take centuries to break down the explosives, but the plants would clean up the soil in just years," he told the BBC.

Ammunition dump explosion, such as this one in Addis Ababa, are one source of pollution

The research is published in Nature Biotechnology. In that journal, Dr Brian Hooker of the Pacific Northwest National Laboratory, US, says this work is the first time a genetically-engineered plant has been shown to reduce poisonous chemicals to harmless ones.

"Some of these sites are literally on the verge of exploding," says Dr Hooker. "They also present serious exposure risks to humans and wildlife. This is a new option for cleaning up these toxins and mutagens and could soon become a reality."

Soils near ammunition factories and dumps can contain up to 20% explosives. Currently, this has to be dug up and passed through an incinerator. But this is very expensive.

Newer ideas have tried to use fungi and microbes to break down the dangerous compounds but this still involves costly excavations.

Some plants, like sugar beet, have shown promise but only remove the explosives partially and very slowly. In some cases the breakdown products are new toxins.

Grow and degrade

Using the new genetically-engineered plants suffers none of these drawbacks. The plants simply grow on the land and completely degrade the explosives.

Dr Bruce believes the plants will be more acceptable to the public, as they will create greenery on previously barren sites.

The laboratory experiments have been done using the tobacco plant. But the poplar is more likely to be put into use as it has long, deep roots and grows quickly.