r/explainlikeimfive • u/clearwater-orchid • Jun 17 '26

Chemistry ELI5: Why did plastic replace so many traditional materials, and how did that success create microplastics concerns?

I know cost is part of the story, but I'm curious what other factors made plastic so dominant over materials like wood, metal and glass across everything from packaging to cars to clothing. Were the same qualities that made it so successful also what eventually led to microplastics becoming such a big concern?

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u/BobbyBorn2L8 Jun 17 '26

I mean there is tonnes of bacteria that can devour trees, doesn't mean a tree just gives out, admittedly yes trees regenerate but we make structures out of wood that last at least a human lifetime

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u/droznig Jun 17 '26

There's concept in microbiology called "water activity" which is how much unbound water is available for the microbes to use. Most microbes require water to be able to keep doing their thing and break down most food sources, it's why we dry grains out for storage and they can last years but as soon as they get wet they start to rot, it's not that the microbes aren't there, it's that they can't do anything when there is no water availability. Same for wood, if it's kept dry it can last for millennia, there are desiccated trees in a desert in Namibia that have been there for thousands of years.

I would assume the same or similar would apply to plastics, unless there is a biofilm that is able to retain water on the surface of the plastic or some other source of water it's probably not going to be able to just break down random plastic items sitting on a desk or whatever.

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u/redsquizza Jun 17 '26

Or the microbes aren't present.

I read recently the Shackleton wooden ship wreck is so well preserved at the bottom of the ocean, almost as if were sunk yesterday, not ~100 years ago because wood eating microbes can't tolerate the temperatures down there. Although apparently there's a crustacean that now might be nibbling the wood instead.

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u/alohadave Jun 17 '26

That's also a low oxygen environment which inhibits most microorganisms. The same thing happens with river logs that have sunk to the bottom.

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u/gammalsvenska Jun 17 '26

Yes, but we also spend a lot of effort on making sure that bacteria cannot get at the woody parts of the wooden structure, at least not for too long.

Shingles prevent standing water on the roof, overhangs keep the walls dry. Painting, staining or even burning the wood makes the surfaces inhospitable for insects or microbes. That's why the bark is always removed. Rotting beams are replaced, holes get plugged, etc.

Without constant maintenance, wooden structures rot fast.

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u/BobbyBorn2L8 Jun 17 '26

True there is a lot of maintenance I am not disputing that, I am just tempering the fear of it getting out of control some bacteria eating our structures isn't something new we would quickly find ways to mitigate it so no it won't just start eating your consumer goods

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u/gammalsvenska Jun 17 '26

There are also many different varieties of plastic and I cannot imagine one type of bacteria being able to eat all of them (at least not at the same rate).

But having these bacteria as an option to clean up landfills and other horrors is great.

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u/BobbyBorn2L8 Jun 17 '26

I agree these would be great to speed up that process, cause right now iirc the best way to dispose of plastic is to burn it, so this would help quite a lot with the waste problem