Jo turns spotlight on sinister plastic islands threatening the world's oceans

The editing process hasn't even begun yet, the hours of footage are yet to be collated into the final film that will reach our cinemas in 2013, but already Sir David Attenborough is calling Bristol-made environmental documentary Away "one of the most important films ever made".

The film will highlight the alarmingly prevalent scourge of plastic pollution in our oceans – a problem that producer Jo Ruxton believes could compete with global warming for the angst of future generations, but which currently goes largely unheeded.

Jo, from Pill, first became aware of the issue during her time as a producer for the BBC's Natural History Unit, during which time she worked on series such as Blue Planet and Life.

But it was a personal trauma that gave Jo the impetus to get this film made.

"I was diagnosed with breast cancer, and it turned my world upside down," she says. "I tried to carry on working as much as I could, but it was a terrifying ordeal to be put through. Seven of my friends were diagnosed with various kinds of cancer all around the same time, and of the eight of us, I am the only one that survived.

"It leaves you feeling that you must have survived it for a reason. Cancer is a dreadful thing to go through, but if you survive and recover from your cancer, you join what Lance Armstrong called the cancer club – you're left a much more driven person.

"Everything falls into place when you've faced your own mortality like that. Everything makes a bit more sense. You sort out your priorities, and it helps you to focus on the things that are most important to you.

"I realised that making a cinema documentary to highlight the growing problem of plastic pollution in our oceans is very important to me. I couldn't help but think that in some way, perhaps that's what I'm still here to do."

Jo first learned about the issue while filming a BBC series called Sharkland back in 2007.

"People kept mentioning this gyre – a sort of enormous vortex of oceans currents – in the middle of the Pacific, that was drawing together an enormous mass of waste plastic," she says.

"It was all washing off the beaches and being flushed through the drains of the Pacific rim countries – mostly the United States – and was being swept up by this natural gyre, until it was all massing in the middle of the ocean – like a sort of enormous floating island of plastic, miles across and many metres deep.

"I later discovered that it wasn't just happening in the Pacific. There were similar gyres of plastic pollution in all the oceans of the world – the one in the North Atlantic that we contribute towards here is every bit as sinister as the Pacific gyre.

"I was so intrigued that I arranged to go out and see it. In my naivety, I had imagined millions of plastic bottles, but it was more insidious than that.

"A lot of it is small pieces of plastic – tiny pieces, small enough to be swallowed by fish and whales – the big plankton eaters are particularly prone to swallowing it up.

"At first glance the water looks immaculate, but dive below the surface and you are surrounded by these millions of pieces of plastic, which have generally at some point either blown off landfill sites, or been washed down streets into sewers and eventually out to sea.

"It takes 20 years for the plastic to reach the centre of the gyre, so we're not even seeing our recent pollution there yet. When you realise that in the last 20 years we have produced and discarded more plastic waste than in the entire century before that, you'll start to realise just how enormous a problem this is turning out to be.

"We have to start asking why we produce so many non-reusable items out of a material that is non-degradable. We have to start acting on this right now."

Jo turns to the screens of the editing suite at Films@59 in Whiteladies Road, where the documentary is currently being put together. She plays a series of horrifying images of the pollution and the devastating effects it is having on fish, whales, seals, turtles and sea birds, filmed by the crew at locations around the world over the past 12 months.

Presenters will include TV's Ben Fogle and world champion freediver Tanya Streeter, and the team is currently in negotiations to get Morgan Freeman to narrate the film.

"It's going to look epic," Jo says. "You have to produce something suitably epic to get the message across that this is an enormous issue. That's why it's ideally suited to cinema release, though we already have a deal in the bag to allow it to get its small screen premiere afterwards on the National Geographic channel.

"The real problem is that these plastics don't degrade, so they're not going anywhere. They're just building up and up. And the problem is not just that they can kill creatures by blocking their digestive system. These tiny pieces of plastic are also carrying numerous toxins, that can easily get into the food chain.

"For example, one of the fish that is consuming this plastic is the little lantern fish, which is in turn the prey of the tuna, which of course we eat. So these toxins very quickly return to us, and research is showing they could potentially be leading to everything from certain kinds of cancers to certain kinds of arthritis – both of which I've had.

"So you see, for me, it's personal," Jo adds, with a smile.

Jo formed a charity, the Plastic Oceans Foundation, to source funding for the project, but she says the charity will continue after the film's release, with the role of further educating children around the world about plastic pollution.

"People simply don't realise that when they drop a fizzy drink bottle on a street, it will probably end up being washed down the drains and eventually into the seas. People often struggle to connect their actions to the bigger picture – that's what I want this film to achieve. To open people's eyes."

Sometimes it's not as subtle as cutting open the stomachs of sea birds and carrying out post-mortem examinations on fish to find plastic-related toxins. While filming in Louisiana earlier this year, the crew found themselves meeting a classic example of how plastic pollution can devastate wildlife.

"We were shown a turtle, known locally as Mae West, who when she was tiny, swam into one of those plastic rings that hang around the neck of a pop bottle," Jo says.

"It lodged around her, and as she grew, her body was forced to contort around the plastic hoop. The result is that her shell and her skeleton are moulded in at the middle, where the hoop was found around her. It was tragic to see."

Jo has named the film simply Away.

"It's where people's rubbish goes," she explains. "You ask anybody where their waste goes, and they say they just throw it away. There is no magical 'away' – people have to realise that it all ends up somewhere. Often that 'away' is in the middle of our oceans."