Harmful plastic waste should be classed as hazardous because of the threat it poses to humans and wildlife, scientists have urged.
Many rich countries class plastic as solid waste, which means it is treated in the same way as food scraps or grass clippings, the experts writing in Nature magazine said.
But plastic debris can harm wildlife, such as turtles, seabirds and marine mammals which can get tangled up in or swallow the waste, while many plastics may be harmful because they are potentially toxic or can absorb other pollutants.
Concerns about the damaging impact of plastic bags, which can find themselves in the marine environment, was behind the south Devon town of Modbury's plastic bag ban – a world first – which remains in force.
Now the team of academics said classifying the most harmful plastics as hazardous would give official environmental agencies the power to restore affected habitats and drive innovation to find new materials with safer, reusable alternatives.
They claimed that if current patterns continued, the planet would hold another 33 billion tonnes of plastic by 2050, enough to fill 2.75 billion bin lorries which could wrap around the planet about 800 times if placed end to end.
But this total could be reduced to just four billion tonnes if the worst plastics were classified as hazardous immediately and replaced with safer, continually reused plastics, the scientists estimated.
Recycling rates are increasing but often involves burning plastics to create energy, which can cause pollution.
Most plastic still goes to landfill, where chemicals leach into surrounding habitats, or end up in the land and marine environment.
Larger pieces of plastic, from bottles to bags, can transport species to new habitats where they can become invasive and do damage, while debris can also damage important species such as mussel and corals.
One of the international team of academics, Professor Richard Thompson of Plymouth University, said that more than 370 species, including some that were critically endangered, could ingest or become entangled in plastic debris.
And as the waste breaks down into microscopic pieces, it can become ingested by fish, invertebrates and tiny organisms, and enter the food chain as a result.
Studies in humans and mussels suggest ingested and inhaled micro-plastic can cause harm in cells and tissues, the scientists said.
The chemical ingredients of some plastics are hazardous, with ingredients of plastics including PVC and polystyrene shown to be cancer-causing in laboratory tests.
Others, such as the plastic used to make carrier bags, are not harmful on their own but can become toxic by picking up pollutants such as pesticides.
Writing in Nature, the scientists said: "We feel that the physical dangers of plastic debris are well enough established, and the suggestions of the chemical dangers sufficiently worrying, that the biggest producers of plastic waste – the United States, Europe and China – must act now.
"These countries should agree to classify as hazardous the most harmful plastics, including those that cannot be reused or recycled because they lack durability or contain mixtures of materials that cannot be separated."