Intervention is needed to stop an estimated 25million tons of plastic flowing into the oceans every year.

If nothing is done, humans will start to asphyxiate themselves in less than two decades because plastic pollution is impairing plankton's ability to produce oxygen.

"People do not realise that 50% of the earth's oxygen is produced by microscopic plankton in the ocean. And if take that away we won't be able to breath soon," said Marco Simeoni, president of the Race for Water Foundation.

The foundation's scientific crew collected data and compiled a snapshot of plastic pollution across the globe on a 300-day, 40 000 nautical mile research expedition as part of a United Nations-led campaign called The Race for Water Odyssey. They visited island beaches situated in known pollution hotspots – five vortexes of plastic waste miles wide that has formed across the various oceans.

"Our preliminary results from the first three stopovers in the Azores, Bermudas and Easter Island showed that plastic makes up 80% of waste in our seas," said Frédéric Sciacca, scientific adviser to the odyssey.

Hard plastic made up between 40% and 74% of the total amount of plastic found at these three sites. Fishing line and rope was the next biggest category, followed by foam, capsules, film and cigarette filters.

Plastic pollution is taking a devastating toll on sea life with 267 different species known to have suffered from entanglement or ingestion of marine debris, including 86% of all sea turtle species, 44% of all sea bird species, while 70 to 100% of albatrosses are known to ingest plastics.

"Plastic is also putting the human food chain at risk. Fish are eating the plastic, and we are eating the fish. We are starting to ingest toxic material," Simeoni said.

The majority of plastic pollution is caused by land-based pollution that is swept into the oceans by heavy rains and rivers.