By Danny Savage
North of England correspondent, BBC News
Dead birds have been found with balloon remnants around their legs
Marine conservationists are calling for a ban on mass balloon releases because birds and mammals are dying from eating discarded balloons.
The Marine Conservation Society (MCS) says organisers of balloon releases should look for different ways to publicise their cause.
The Balloon Association says there is no proof latex balloons kill animals.
But the MCS says it has photographs of dead marine birds and mammals washed up on the beach in Blackpool.
A graphic photo from the examination of a dead turtle shows an old balloon in its gut. The suspicion is that the turtle thought the brightly coloured fragment floating on the water was something edible.
Statistically it may not be a huge pollution, but it's wrong and needless
It appears the consequences were fatal.
There is also an image of a decomposed razorbill - a bird which lives on islands off the British coast during the breeding season - with its legs entangled in the string from a balloon.
It is not clear if this is what killed the bird, but it certainly would have hindered its mobility.
Gill Bell, from the MCS, says the problem is getting worse year after year.
"In the last 10 years we have seen a 260% increase in the number of balloons we are finding on our beaches.
"And we know that these are just the balloons on the beaches. We believe there are many more in the water.
"A recent international survey found nearly 60,000 balloons over a two-day period last year. Who knows how many are in the sea. It's vast and we just don't know."
I met Gill in the harbour at Seahouses in Northumberland. The area off the coast here around the Farne Islands is a European Marine Reserve, but still there is evidence of balloon pollution.
Gill Bell of the Marine Conservation Society on alternatives to balloon releases
In a 100m stretch of beach we find two balloons and their strings tangled up in clumps of seaweed.
We are joined by Mike Hosken who lives in the village. He combines walking his dog with regular litter picking on a stretch of beach between Seahouses and neighbouring Beadnell.
He often finds old balloons and, if he can identify where they have come from, he sends them back.
"One of the recent cases - and remember we are on the north-east coast - was a balloon from Gloucester city.
"They come from everywhere. Statistically it may not be a huge pollution, but it's wrong and needless."
The Balloon Association, which represents manufacturers, says the industry drew up a code of conduct for balloon releases in conjunction with the MCS.
The associations say released balloons reach high altitude, shatter and decompose.
In a statement, it said: "Latex is fully biodegradable and an inflated latex balloon decomposes at about the same rate as an oak leaf under similar conditions."
The MCS is now trying to persuade local authorities and organisers of balloon releases to do something different.
They say they are not being killjoys, but suggest that balloons are just filled with air rather then helium. It's the helium balloons that float high up into the air and drift for miles.
They have had some luck. A car dealer filled a car with balloons rather then releasing them.
Here in Northumberland, a local supermarket in Alnwick was also persuaded not to release hundreds of balloons because of concerns for wildlife.
They acknowledge that some balloons are biodegradable, but argue this is a very slow process, especially in water.
They also believe that if people spared a thought for where the balloons they release may end up, they may decide not to let them go in the first place.
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