Every year millions of lead bullets are fired around the world in combat and at firing ranges. But is there an alternative to using toxic lead?

The idea of a bullet designed both to kill the enemy and be kind to the environment might sound like a macabre joke. In combat, soldiers don't usually worry about the green credentials of the enemy.

But armies in Scandinavia are so concerned about the pollution caused by lead bullets they're replacing their entire stock with non-toxic versions. The manufacturers are encouraging the British armed forces to do the same.

But is there really a case to go lead-free?

"If you're getting killed by a lead bullet or lead-free it doesn't really matter, but most ammunition is used for training anyway," explains Urban Oholm, senior vice-president of Swedish arms manufacturer Nammo.

Find out more Greening the Military, with Angus Crawford, was broadcast on Radio 4 at 20:00 BST on Monday 6 August Catch up via iPlayer

His firm has pioneered the development of "green" ammunition.

"Once you decide that weapons and ammunition is needed in the world as it is today, you have to design them in as environmentally friendly way as possible," says Oholm.

Image caption Lead-free bullets are cased in steel

Lead is toxic and there have been studies that have suggested it can leach from firing ranges into ground water. The US Environmental Protection Agency provides guidelines for firing ranges to avoid lead contamination.

There have also been concerns that gases given off during firing are bad for the health of soldiers, especially to women of child-bearing age. Five per cent of Sweden's soldiers are female.

In 1995, the Swedish government requested alternative ammunition. Four years later, the first lead-free bullets were delivered. Since then Nammo has made 360 million at its plant on the shores of Lake Vattern in southern Sweden.

To the untrained eye there's nothing to mark out the green bullets as different, from the pointed, copper-coloured tip, down the shining cartridge to the ridged base.

But Nammo claims each green round is designed to "minimise the impact on users' health" and on the environment. The company also trumpets that the new design shows "improved lethality".

They now make 80 million a year. All lead has been removed along with any heavy metals in the gunpowder. The core of the round is made of steel.

Image caption Swedish soldiers now fire lead-free bullets

Lead has always been an obvious choice for ammunition. It's cheap, heavy and easy to mould into bullet shapes - it also has a lubricating effect on gun barrels when fired.

Nammo claims that over the past decade it has prevented 1,200 tonnes of lead being put into the environment.

But the introduction of lead-free rounds has not been without its problems. In 2009 soldiers began to report fever, headaches and joint pains after using the rounds in the Norwegian army's new assault rifle. For a time they were forced to revert to their old ammunition.

Research showed that the combination of new bullets and new weapons caused increases in emissions of carbon dioxide, ammonia and hydrogen cyanide. There was a complete redesign and Nammo claims the problems have now been solved.

The British military don't use lead-free rounds, and the Ministry of Defence says it has no plans to introduce them. It says the make-up of the ammunition is "dictated by the target effect required to incapacitate/kill an enemy at specified ranges".

There are no accurate figures for how many are used on firing ranges in the UK, but over the past year in Afghanistan, British troops fired almost four million.

As for the UK's arms firms, in 2006 BAE Systems announced at its AGM that it was going to start making alternative rounds. It was part of a range of new environmentally friendly products including biodegradable landmines. But in 2008, citing increased production costs, the company abandoned plans for the new rounds.

Nammo is disappointed by the British position. "It's embarrassing, that's such a hi-tech country," says Oholm.

But he concedes that the pressures of campaigns in Iraq and Afghanistan are probably to blame.

The MoD has had to focus on getting enough conventional ammunition to the front line, not introducing a new type of bullet.