Image copyright WWT Image caption Ducks, geese and swans can consume spent lead shot in grit and food

About 100,000 wetland birds are killed every year from poisoning by discarded lead ammunition, say scientists.

This is one of the conclusions of a report published on Thursday by the University of Oxford.

The report also suggests that the consumption of game shot with lead ammunition has a greater impact on human health than previously thought.

Scientists involved in the research say the evidence now supports a ban on the use of lead ammunition in the UK.

The report is a collection of research presented by experts who gathered at the Oxford Symposium on Lead ammunition last year. It includes findings from studies carried out by university academics and by conservation groups including the Wildfowl and Wetlands Trust (WWT) and the RSPB.

As well as the impacts of lead on the environment, researchers have investigated the effects on human health of consuming game containing traces of lead ammunition.

Lord Krebs, emeritus professor of zoology at the University of Oxford, and former chair of the UK Food Standards Agency, told BBC News that there was "an overwhelming body of evidence" that lead used in hunting was "a risk both to humans and to wildlife".

"On that basis," he told BBC News. "The advice would be that lead shot should be phased out."

Lead consumption

The use of lead shot has been restricted throughout the UK since 1999, although the rules differ in England and Wales, Scotland and Northern Ireland. But the WWT says that these regulations - designed largely to prevent lead shot being used over wetland habitats - are not working.

In England and Wales, for example, although game birds like pheasant and grouse can be shot with lead, hunters must use alternative, non-toxic ammunition to shoot ducks and geese.

But the WWT recently carried out tests on just over 100 ducks purchased as "locally shot" from suppliers in England and found that more than three quarters were killed using lead.

Media playback is unsupported on your device Media caption Dr Debbie Pain and Ruth Cromie from the Wildfowl and Wetlands Trust explain why wildfowl are vulnerable to lead poisoning

Ruth Cromie from the Wildfowl and Wetlands Trust told BBC News: "A lot of people are ignoring [the regulations]."

"And even where the law is being obeyed, it's possible for water birds to be exposed to legally deposited lead, so the issue is that the law isn't protecting birds from lead poisoning."

But shooting organisations in the UK see a campaign against lead shot as a campaign against hunting.

20-year experiment

Christopher Graffius from the British Association for Shooting and Conservation told BBC News: "We have already reduced the amount of lead being released into the environment.

"And when it comes to human health, there are risk management procedures [in place]; a ban would be a knee-jerk response - it's not proportionate."

But Lord Krebs said that even the threat to human health from consuming wild game shot legally with lead was a concern.

"People who eat wild game regularly, particularly young children, are at risk of some adverse effects," he told BBC News. "It could affect their mental development."

Media playback is unsupported on your device Media caption Danish hunter Niels Kanstrup explains why he believes lead shot is a "poison for hunting"

"We don't allow our children to chew on toys painted with lead paint, so why should we be allowing them to chew on game that contains fragments of lead."

In Denmark, the use and possession of lead shot has been banned since 1996 - creating a test-bed for legislation that some conservation organisations in the UK are pushing for.

Niels Kanstrup, a Danish hunter and biologist says the ban has actually been beneficial for hunting.

"I'm a conservationist," he told BBC News. "I'm a hunter, too.

"I think it's a fair and sustainable way to use natural resources, but we can't have it connected with spreading poisonous heavy metals in nature."

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