We have long known about massive piles of garbage that blot the surface of the oceans. The Great Pacific Garbage Patch is a sprawling 1.6 million square km mass floating between Hawaii and California that is estimated to contain about 1.8 trillion pieces of plastic — or about 250 pieces per person on the planet — and weighs about 80,000 metric tons. A similar patch stains the Atlantic Ocean.

Because plastic floats, scientists had assumed that those horrific spectacles were the worst of the problem. They recently discovered, however, that plastic can be found far below the ocean surface. In fact, most of the plastic is underwater, from just below the waves to the deepest parts of the ocean. Concentrations are higher the greater the distance from shore. Plastic fibers have even been found in the stomachs of creatures in the Marianas Trench, the lowest point on Earth at 12,000 meters below sea level. Japan is pressing for action in the Group of 20 to counter this discovery; it is long overdue.

Scientists have discovered that the highest concentrations of microplastics — tiny pieces of material less than 5 mm in size — are in water 200 to 600 meters deep and reach levels of 12 to 15 particles per square meter, amounts comparable to those of the Great Pacific Garbage Patch. They concluded that the presence of these plastics "extends much further and more extensively into the waters, sediments, and animal communities of the deep sea" than previously realized.