Activists have been arguing for years that plastic bags harm the environment. But now there’s also concern that plastic products may be a detriment to the planet because they break down so slowly — or not at all.

That’s the point made by actor Jeff Bridges in a March 28 Facebook video that he narrates on behalf of the Plastic Pollution Coalition.

“Plastic is a substance the Earth cannot digest, and every bit of plastic that has ever been created still exists,” Bridges says. “Plastic never goes away.”

Unlike some types of plastic, that claim fell apart pretty quickly under scrutiny.

Yes, some types of plastic are very slow to decompose, and can persist for decades or centuries. Bridges has a point that these types are major causes for concern.

But all the researchers we talked to said plastics have gone away.

Eric Grulke, associate dean for research in the college of engineering at the University of Kentucky, said a lot of plastic products are no longer around because they’ve been burned. Incinerators consume them, sometimes to generate electricity, he said.

Other plastic decomposes at varying rates, depending on the type and where it is.

Polyethylene, “your basic hefty bag material, breaks down really, really slowly, and in a landfill it might not break down at all because it’s typically starved of oxygen and water. So a polyethylene bag made in 1960 might still be with us … , ” said Eric Beckman, a chemical and petroleum engineer at the University of Pittsburgh.

“On the other hand, if you’re talking about polylactic acid, which is popular in disposable tableware these days, that’s actually designed to degrade,” he said. “In a composting environment, it will go away in a matter of weeks to months.”

Not a lot of microscopic bugs have a talent for breaking apart the strong bonds that make many plastics so durable. But they exist, said Rigoberto Advincula, chairman of the polymer chemistry division of the American Chemical Society.

And not all decomposition is good.

In the ocean, there’s two types of degradation, said Beckman. “The good type is when it’s actually chemically falling apart. When you have water and sunlight, that helps things go faster. There’s also mechanical degradation, where you have a bottle that slowly gets ground down by bumping into other things and becomes chips. That’s bad because fish will eat that. You can find fish with bits of plastic in their stomach.”

Anthony Andrady, a chemical and biomolecular engineer at North Carolina State University, said it’s not universally desirable to have plastics break down or be burned because it takes a lot of energy to make them, energy that could be saved if they were recycled. To throw away a styrofoam cup or plastic cutlery “is a waste,” he said.

And someday, if we run out of the oil that serves as the raw material for making resilient plastics and there are landfills with high concentrations of plastic waste, “I can imagine people mining the landfills to get that resource. That is not inconceivable at all.” Andrady said.

Our ruling

Bridges’ statement was absolute: “Every bit of plastic that has ever been created still exists.”

The experts say that’s rubbish.

Although far too much plastic persists in the environment, because this provocative claim leaves no room for subtlety, we rate it False.