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American Association for the Advancement of Science

Smaller plastic, bigger problem

Plastic fragments collected using a plankton net in the North Pacific subtropical gyre. Fragments are generally 1-5 mm in size.
[Image courtesy of G. Proskurowski/Sea Education Association]

Even very small fragments of plastic can be harmful to life in the ocean, according to a new Policy Forum in the 11 July issue of Science. In this Policy Forum, Kara Law and Richard Thompson explain the dangers of pieces of plastic smaller than a few millimeters, called microplastics.

Because they are so small, microplastics can be eaten by very small animals. Often, before they are eaten, the plastics soak up harmful chemicals polluting the ocean water. They can release these harmful chemicals into an animal's body. When bigger animals eat many smaller animals, they collect a lot of those harmful chemicals, too, in a process called, "biomagnification."

Scientists are still trying to figure out how bad microplastics are for animals, how plentiful they are, and how quickly they are being released into the ocean, but they do know that many different types of animals are eating them.

Because microplastics are so small, it is hard to figure out how they spread. They have been found both far away from land and on the coast, in Arctic sea ice and in the Mediterranean Sea.

Humans cannot remove a substantial amount of microplastics from the ocean, say Law and Thompson, but they can put less into the ocean from now on by using less plastic and understanding how valuable it is.