Nurdles are lentil-sized pellets of plastics—polyethylene, polypropylene, polystyrene, and so on—that are used to make everything from consumer goods to the containers we ship them in. They're an environmental terror, not least because they look like food to aquatic life. Some 230,000 tons of them are set afloat on the high seas every year.
Like crude oil, nurdles are highly persistent pollutants, and will continue to circulate in ocean currents and wash ashore for decades. They are also "toxic sponges," which attract chemical toxins and other pollutants on to their surfaces.
"The pellets themselves are a mixture of chemicals—they are fossil fuels," says Tom Gammage, at the Environmental Investigation Agency (EIA), an international campaign group. "But they act as toxic sponges. A lot of toxic chemicals—which in the case of Sri Lanka are already in the water—are hydrophobic [repel water], so they gather on the surface of microplastics.