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You probably already knew that plastic can be bad, but scientists have taken a closer look, and found out it can be bad in surprising ways.

Happy Earth Day! After watching this video, check out our Earth Day play list, which features episodes about our world, and how we're handling some of our biggest problems.

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[ intro ].

Plastic as we know it has only been widely used since Tupperware was invented in the 1940s, but now it's nearly impossible to go a day without it. And as useful as it is, plastic also causes some serious problems.

You've heard about these things, turtles caught in six-pack rings, garbage patches as large as Texas, and beaches with more plastic debris than sand. After all, millions of tons of plastic end up in our oceans every year. But as bad as that sounds, some consequences of plastic pollution might still surprise you.

For one, plastics can emit greenhouse gases forever— not just during the making and disposing of them. Plastic is basically just a long chain of molecules, and when it's exposed to sunlight,. UV radiation starts to break that chain down into smaller molecules like methane and ethylene, in a process called off-gassing.

Both of these are greenhouse gases, but methane is especially bad because it's 25 times better at trapping heat in our atmosphere than carbon dioxide. And as plastic breaks down, the problem actually gets worse, not better. Researchers have found that, as more surfaces get exposed, there's a huge increase in the release of gases.

For example, a common plastic called LDPE, or low-density polyethylene, releases methane 488 times faster in a powdered form than in pellet form. . To make matters worse, once this off-gassing process begins, it can continue even without sunlight. That's because those first broken bonds make the rest of the plastic more brittle, so it more easily breaks down on its own.

Over time, it keeps breaking into smaller and smaller, eventually invisible, particles. And as it does, it releases greenhouse gases into the air. Unfortunately, that's not the end of the story.

These indestructible pieces of plastic are also contributing to another modern problem: antibiotic resistance. In a 2020 study out of Northern Ireland, scientists collected bacteria from plastic found along the Irish coastline and tried to kill them with 10 commonly used antibiotics. ...which turned out to be surprisingly hard to do. 98% of the bacteria were resistant to ampicillin, one of the most commonly prescribed antibiotics for things like sinus and ear infections. And 16% of the bacteria were resistant to minocycline, another type of antibiotic.

Unfortunately, plastic is a great breeding ground for bacteria, because they will grow on any available surface in the ocean. And many antibiotic-resistant bacteria are already out there— plastics just give them more places to flourish. Once again, the problem gets worse as plastics break down, because they create even more surface area for bacteria to colonize.

And these bacteria don't just stay way out in the ocean. The same study showed that ocean currents can carry plastic covered in bacteria back into coastal waterways, where different species could ingest them. Unfortunately, another 2020 study found that bacterial growth on marine plastics actually makes these plastics smell like food to sea turtles.

So animals could be eating plastic because it smells good rather than because it looks like food. Which is not great. Ingesting plastic covered in antibiotic-resistant bacteria could create health problems for marine animals— and also for creatures higher up the food chain, including us.

Now, as plastic breaks down, it breaks into smaller and smaller and smaller pieces, and some of the smallest plastics may be capable of doing the most harm. Any plastic that's smaller than a few micrometers is called a nanoparticle, and research has found that these microscopic particles can even pass through biological barriers, such as cell membranes. That means they can enter the bloodstream of animals, pass through the gut lining, and penetrate tissues.

They can also accumulate in organs like the liver, kidneys, and intestines. Plastic nanoparticles have even been found to penetrate the blood-brain barrier, a layer of cells that filter harmful substances out of the blood so they can't get into the brain. This seems to be dangerous no matter where you are on the food chain.

In a 2017 study out of Sweden, researchers exposed a zooplankton called Daphnia magna to a bunch of plastic nanoparticles. The Daphnia consumed these particles, and scientists found that, while the larger particles didn't seem to affect them, the smallest particles —around 50 nanometers—were deadly. Next, to see the effect of the nanoparticles higher up in the food chain, they exposed a group of Daphnia to the plastic nanoparticles again, and then fed them to some fish called Crucian carp.

Over the next two months, the carp started to change:. They swam slower, explored less of their environment, and lost more weight than the control group. When the researchers analyzed their brains, they found the 53-nanometer particles they had fed to the Daphnia— in the fish's brains.

And they think these invisible particles changed the carp's behavior. These findings show that plastic nanoparticles can move up the food chain— and interfere with the natural function of an ecosystem. And if we ate fish that had ingested nanoparticles, researchers suggest that could even have a direct impact on us.

Plastic is everywhere—in every environment in our planet— and it's not going away anytime soon. In some ways, that's great, because plastic can be really useful. But unfortunately, it has some impacts that probably no one was thinking about when they invented Tupperware.

Still, the less plastic we use, and the more we understand the consequences, the better we can protect ourselves and our planet's natural ecosystems. Thanks for watching this episode of SciShow! Today is Earth Day!

And if you want to learn about ways to make this planet a better, less-polluted place, you might like our video about how engineers and research groups are working on ways to clean up our oceans. You can watch that right after this. [ outro ].