this post was submitted on 20 Oct 2023
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Particularly, I worry that CO₂, plastics, uranium, HCFCs etc. are just the first of many problems we'll have with breaking down these materials. The non-biological elementome will not degrade, at least not without leaving non-biological elements behind.
That can be fine. Rocks generally don't participate in the biological cycle either and they don't bother anyone.
But for example, plastics are practically rocks in funny shapes, which float out into the ocean. Even just that tiny difference causes problems for maritime wildlife. Other super-durable materials will produce different rocks, which may cause problems in new and innovative ways.
And of course, not everything we use is a rock. Some materials will genuinely just interact with our surroundings in destructive ways. The hope is that they do then degrade.
Plastics are not rocks in funny shapes. We are made of plastics. They're just unusual compounds which no primary decomposer has developed yet.
That's not to say we shouldn't address the issue, but it's important to understand what the issue actually is. The fact that plastics are familiar yet unfamiliar compounds is actually what causes the problems.
Where do you get the idea we are made of plastics? Not necessarily throwing shade, just.. I'm a molecular biologist and at first pass that seems like a stretch. I'd be excited to be wrong
Thermosets and thermoplastics, right? Not sure that we have that going on in there...
Cellulose, starch, and chitin are all sugar polymers in plants and crustaceans (may be a broader group, I used chitosan from crustaceans though).
In mammals, collagen is a polymer. It's like 30% of a humans non-water weight. Bones are composites that are tough collagen binding hard and strong fibers of apatite (mostly calcium apatite/ hydroxyapatite). I don't think the apatite system is considered a polymer, though.
Triglycerides aren't polymers in adipose tissue. Although plant triglycerides can split and polymerize. Which make beautiful wood stains.
Yeah but like... not all polymers are plastics, right? Like... they aren't synonyms?
Wikipedia says acrylics, polyesters, silicones, polyurethanes, thermoplastics, and thermosets are plastics. Do those exist in organic tissue? Am I missing an obvious group?
All plastics are polymers, but I really don't think it's a commonly held view that all polymers are plastics
Ah ok. That's probably true. I was under the impression that a polymer that is solid at room temperature is a plastic.
Plastic as a term only makes sense to not include biological polymers if we define it to only be man-made polymers. It's arbitrary semantics, so I find it's better to be inclusive to help show the chemical quirks than to be exclusive on arbitrary lines.
It's fine if you want to draw some conceptual comparisons between biological and synthetic polymers, but it's 100% not true that "plastics" as defined as synthetic, organic polymers (I.e. acrylics, silicones, polyesters, polyurethanes, halogenated plastics, thermosets, thermoplastics et al.) are the same on a chemical basis as most biological polymers.
Like... where are you drawing the line? Are proteins a plastic? Is starch plastic? Is DNA plastic? RNA? Clearly not, by multiple definitions (bioavailability, reactivity, structure and function, persistence in the environment, etc.). Even biological compounds closer to synthetic polymers (cellulose, chitin, etc.) are definitively different, even if they do have longer persistence, lower reactivity, etc. And bioplastics (like what people mean when they say biodegradable plastics) are heat-modified biological polymers. They don't come out of a living thing that way; they are fundamentally altered from their previous form.
I guess I just... disagree that the distinction is "arbitrary semantics"?
All of these types of plastic you're using as counterexamples are more distinct from each other than they are from biological polymers.
Plastics are a ridiculously diverse group of chemicals, not including naturally occurring polymers is anthropocentric and not always useful.
What, in your opinion, is the semantic difference between the words plastic and polymer?
What is your word of choice to distinguish between naturally occurring and lab-made polymers?
It depends on the context. Sometimes plastic is good for that, but in this case I don't believe that it is.
Plastic is not a rigorous term. When discussing specific plastics it's petty much always better to describe specifics, because plastics are too diverse of chemistry to do anything else.