How Long Does it Take Plastics to Break Down?

In December of 2016, a little yogurt cup washed along a beach in Canada — not an unusual circumstance. What is unusual was the fact that this yogurt cup was commemorating the 1976 Olympics. For 40 years, it was floating on the surface of the ocean. This event forced us to ask the question: “How long does it take for plastic to decompose?” We’ve investigated the answer, discovering the sheer scale of the amount of time for plastic to break down, including common items like grocery bags, Styrofoam cups, and drinking straws. It might be uncomfortable, but it’s time to talk about what happens to plastic when you throw it away and where it ends up.

First of all, how long does it take for plastic to biodegrade? The answer is simple: It doesn’t. Most common plastics are not biodegradable, or able to be broken down by bacteria or living organisms. Most plastics are photodegradable, or able to be broken down by the sun. But that doesn’t help the plastics at the bottom of landfills or on the ocean floor. The proper question instead is, “How long does plastic take to decompose?”

How long will plastic last in the ocean? In some cases, it’s centuries. More often, items like plastic bottles are pulverized into little bits due to friction. But that means that big chunks of plastic are turned into microplastics, hardly larger than the size of a paperclip, and dangerous chemicals. This led to the creation of the term “plastic soup” when describing the biggest ocean gyres. Indeed, a plastic ocean of those substances might be in our future.

To get from new polyethylene terephthalate plastic bottles in ocean waters to those little microplastics can take anywhere between 450 and 1,000 years. (In human history, that’s the span of time from the death of the Roman Empire to now.) For lighter, thinner plastics, it can be less: About a hundred years is how long it takes for plastic bags to decompose. For plastic straws, disposable diapers, and Styrofoam, decomposition can take about 500 years. It’s not like we can wait around for plastic to decompose with a stop watch, so there may be uncertainty; however, it’s clear that our trash will be still floating around many generations from now.

In the meantime, the plastic pollution in the ocean will be doing untold damage to wildlife. Seabirds will eat plastic bottle caps floating on the surface of the ocean, which look like prey, and die, and the bottle caps inside them will outlast their carcasses. Plastic straws will end up stuck in the nostrils of sea turtles, like in this disturbing viral video. Long and thin microfibers from old polyester clothing will line the stomachs of fish and mussels, eventually killing them.

Just how much plastic is in the ocean? Facts about plastic are upsetting, and this one is a doozy: There’s a giant plastic island in the ocean called the Great Pacific Garbage Patch that measures 1.6 million square kilometers, about the size of Mexico, and contains 80,000 tons of plastic (which is four times previous estimates). And that’s just one of the gyres full of plastic in our seas. A mega-expedition studied the patch, and the data is astounding.

Let’s together think more consciously about what we throw out and how long it takes for plastic to break down before tossing it in our ocean.

Sources:

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