In 2017, approximately 2.25 billion nurdles — tiny plastic pellets the size of a lentil — spilled from a ship moored in Durban in South Africa.

Now, just as predicted, they're washing up on beaches in the south-west of Western Australia.

While nurdles might sound cute, they are anything but.

These pellets are the raw form of plastic, used since the 1960s as the basis of most plastic goods ranging from laptops through to milk bottles.

They can spill at the point of manufacture or while in transit, and when they do, they are extremely difficult to clean up.

That's if anyone is prepared to take responsibility for the clean-up.

Thousands of kilometres from Durban, Harriet Paterson spends her days on hands and knees, methodically scouring local beaches for this plastic waste.

Dr Paterson, a biological oceanographer based in Albany, south of Perth, says around a third of the plastic she collects is made up of nurdles, from countless spills.

As far as most nurdles are concerned, their origins are mysterious — they could have been circulating the planet for the last 60 years.

But, Dr Paterson says, the Durban nurdles are different.

"We know what they look like, we know what their chemical signature is and we know where they started from," she says.

This makes them particularly interesting to oceanographers tracking how currents carry rubbish around the ocean. And they provide a case study into the question of who should clean them up.