Editor’s note: For the last few weeks Civil Beat has been exploring the use of plastic foam in Hawaii and asking the question: Why do we use so much of it here? This is another report in that series.

Discarded bottle caps, toothbrushes, computer monitors and about every size and color of broken-down plastics line Kamilo Beach on the Big Island. One of the most polluted beaches in the world, it’s the unfortunate recipient of debris on its way to the Great Pacific Garbage Patch, a massive depository of plastics floating in the Pacific Ocean estimated to be larger than the size of Texas.

But these are just the plastics you see. There are also the plastics you don’t see – many of which come from plastic foam. Technically called expanded polystyrene, the foam breaks down into tiny, even microscopic, parts, sinks and is ingested by fish and other marine life.

“It’s the most pernicious,” said Charles Moore, who has been studying plastics in the ocean for years and discovered the Great Pacific Garbage Patch more than a decade ago. While most plastics float on the ocean’s surface, Moore said, the foam particles sink and become distributed throughout the ocean’s depths. He says plastic foam is probably the most prevalent plastic, affecting the greatest number of marine species.

The small pieces of plastic are mistaken for food by fish, seabirds and filter-feeding organisms, such as jellyfish. The exact impact on the animals and fish in unclear, but scientists say it can’t be good. The plastics can cause irritation or damage to the digestive system, and if stuck in the gut, fish and birds could mistakenly feel full, leading to malnutrition and even starvation, according to the National Oceanic and Atmospheric Association.

And then there are the toxins. Styrene, the foam’s main component is a known animal carcinogen, according to the U.S. Department of Health and Human Services.

Adding to its potential toxicity, oil-based plastics, such as polystyrene, attract other oil-based substances that include PCBs and pesticides, according to Mariam Gordon, the director of Clean Water Action California.

“There is a reason we are focusing on polystyrene and why we support banning foam food containers and its primarily because foam is a bad actor in the marine environment,” she said.

Her organization has led efforts to ban foam cups and containers in California, where presently 53 jurisdictions have passed moratoriums on polystyrene.

Similar actions have been attempted in Hawaii. A bill was proposed in the state legislature in 2008, but it failed, as did a county initiative in Maui in 2008.

It’s hard to say how much of the plastic debris in Hawaii’s near-shore waters comes from plastic foam. It’s also not clear whether polystyrene biodegrades – ever. If it does, scientists say that it could take hundreds of years to disappear.

“None of the major consumer plastics have a time scale in human terms that would be less than several generations,” said Moore. “No one will ever be able to say that the plastic bottle lost overboard by mom is gone now.”

Read our related stories about plastic foam in Hawaii:

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