A leading scientist has said that the millions of tonnes of plastic pollution floating in the world's oceans could pose a threat to human health.

Dr Robbie Smith, from the Bermuda Natural History Museum, warned plastic rubbish is attracting other chemical pollutants washed into the sea - such as flame retardants and pesticides - as sunlight breaks plastic down and waves churn it into tiny fragments.

Because the plastic pieces look so similar to the natural prey of marine animals, the chemicals then get passed up the food chain.

Dr Smith said: "The more we look where plastic is and the form it's in, big or small, the stronger it is integrated into food webs."

"The only place it can go once it is in the food web is up to the top, and we are sitting at the top. So we have the most to lose here."

Bermuda is increasingly alarmed by the amount of rubbish washing up on its shores.

It is on the edge of the Atlantic garbage patch, a swirling mass of plastic that is hundreds of kilometres wide and has been concentrated by the ocean currents.

Scientists trawling a fine-mesh net have found up to 200,000 pieces per square kilometre. Most are just millimetres across - fragments of the myriad of plastic items in use today.

Eight million tonnes of plastic are dumped in the world's oceans every year. That is the equivalent of one full rubbish lorry's worth every minute.

But the plastic does not disappear - it just disintegrates into ever smaller pieces over several decades.

By 2050, it is predicted that so much plastic will have accumulated in the world's oceans that it will weigh more than all the fish combined.