5 ms·

It is with complete ignorance that I'm asking this, but isn't it the case that, at a molecular level, plastics are just like any other material? That they can b

It is with complete ignorance that I'm asking this, but isn't it the case that, at a molecular level, plastics are just like any other material? That they can be broken down to such a point that their molecular composition no longer matters, and they are, once again, "raw" molecules by which other things (even living things) can be composed? What does "accumulation" even mean in that context?

mlyle 5y ago
Anything can be broken down, but many things are effectively stable in the environment-- including in organisms-- for nearly forever, because nothing breaks them down or the rate of degradation is low enough that it doesn't matter. What I believe he's saying is: even if it looks like bacteria may eventually begin to chip away at the microplastics problem, we still face the prospect of having them accumulate for decades or longer in bigger lifeforms and cause problems. (But at least today's plastic releases wouldn't be a problem forever). That is, this improves the situation greatly but doesn't remove any of the nearer term suck.
- politician 5y ago
  On long enough time scales, the all of the plastic on Earth will be incinerated, regardless of whether microbes evolve to make use of it sooner.
- ars 5y ago
  > we still face the prospect of having them accumulate for decades or longer in bigger lifeforms and cause problems. That's not really accurate - if an organism can breakdown (digest) plastic to any extent, it can do so all the way to water and CO2. There are a few exceptions: Teflon and PVC are the main ones, but most plastic is pretty simple, and once digested it will not accumulate.
  - mlyle 5y ago
    > That's not really accurate - if an organism can breakdown (digest) plastic to any extent, it can do so all the way to water and CO2. I can't breakdown most plastic to any significant extent. If I ate small pieces of plastic, some would be excreted in poop and some would accumulate in my body. If I ate animals that have eaten small pieces of plastic, being high up the foodchain, this may be exacerbated (biomagnification). If bacteria learn to degrade plastic--- that may improve the situation for my grandchildren but it probably doesn't reduce how much is accumulating in marine life now that much.
    - soperj 5y ago
      that's entirely dependent on whether the bacteria can exist within the gut of the aforementioned marine life. If they're eating plastic, and ingest that bacteria, and it starts to act on all of the plastic that's been stuck in their system for years, that would improve the situation.
      - mlyle 5y ago
        > If they're eating plastic, and ingest that bacteria, and it starts to act on all of the plastic that's been stuck in their system for years, that would improve the situation. That's a lot of ifs. Right now significant biodegradation of plastic by marine bacteria is still pretty unlikely. Further presuming that the bacteria capable of this will also evolve to exist within the gut of higher marine line is a bit of a leap: guts are a pretty harsh competitive environment and "random" bacteria you ingest don't go live there. And, it further presumes that all the accumulated plastic resides within the gut (it doesn't).
        soperj 5y ago
        >And, it further presumes that all the accumulated plastic resides within the gut (it doesn't) Where does it reside?
        mlyle 5y ago
        Once the pieces get small, they tend to migrate and accumulate throughout an organism. e.g. https://www.acs.org/content/acs/en/pressroom/newsreleases/2020/august/micro-and-nanoplastics-detectable-in-human-tissues.html https://www.acs.org/content/acs/en/pressroom/newsreleases/20... No one really knows what the impact of this is. Maybe it's not too bad. Maybe it is.
- pphysch 5y ago
  How are plastics different than other un-metabolizeable (?) substances (dirt) that organisms have been accidentally ingesting since time immemorial? Some are probably toxic, but so are naturally occurring heavy metals, etc.
ars 5y ago
Most plastics are just water and CO2 in various combinations. A few (PVC) have some chlorine, but the vast majority could be burned, or digested by a bacteria, and emit just water and CO2.

mlyle 5y ago

Anything can be broken down, but many things are effectively stable in the environment-- including in organisms-- for nearly forever, because nothing breaks them down or the rate of degradation is low enough that it doesn't matter. What I believe he's saying is: even if it looks like bacteria may eventually begin to chip away at the microplastics problem, we still face the prospect of having them accumulate for decades or longer in bigger lifeforms and cause problems. (But at least today's plastic releases wouldn't be a problem forever). That is, this improves the situation greatly but doesn't remove any of the nearer term suck.

politician 5y ago
On long enough time scales, the all of the plastic on Earth will be incinerated, regardless of whether microbes evolve to make use of it sooner.
ars 5y ago
> we still face the prospect of having them accumulate for decades or longer in bigger lifeforms and cause problems. That's not really accurate - if an organism can breakdown (digest) plastic to any extent, it can do so all the way to water and CO2. There are a few exceptions: Teflon and PVC are the main ones, but most plastic is pretty simple, and once digested it will not accumulate.
- mlyle 5y ago
  > That's not really accurate - if an organism can breakdown (digest) plastic to any extent, it can do so all the way to water and CO2. I can't breakdown most plastic to any significant extent. If I ate small pieces of plastic, some would be excreted in poop and some would accumulate in my body. If I ate animals that have eaten small pieces of plastic, being high up the foodchain, this may be exacerbated (biomagnification). If bacteria learn to degrade plastic--- that may improve the situation for my grandchildren but it probably doesn't reduce how much is accumulating in marine life now that much.
  - soperj 5y ago
    that's entirely dependent on whether the bacteria can exist within the gut of the aforementioned marine life. If they're eating plastic, and ingest that bacteria, and it starts to act on all of the plastic that's been stuck in their system for years, that would improve the situation.
    - mlyle 5y ago
      > If they're eating plastic, and ingest that bacteria, and it starts to act on all of the plastic that's been stuck in their system for years, that would improve the situation. That's a lot of ifs. Right now significant biodegradation of plastic by marine bacteria is still pretty unlikely. Further presuming that the bacteria capable of this will also evolve to exist within the gut of higher marine line is a bit of a leap: guts are a pretty harsh competitive environment and "random" bacteria you ingest don't go live there. And, it further presumes that all the accumulated plastic resides within the gut (it doesn't).
      - soperj 5y ago
        >And, it further presumes that all the accumulated plastic resides within the gut (it doesn't) Where does it reside?
        mlyle 5y ago
        Once the pieces get small, they tend to migrate and accumulate throughout an organism. e.g. https://www.acs.org/content/acs/en/pressroom/newsreleases/2020/august/micro-and-nanoplastics-detectable-in-human-tissues.html https://www.acs.org/content/acs/en/pressroom/newsreleases/20... No one really knows what the impact of this is. Maybe it's not too bad. Maybe it is.
pphysch 5y ago
How are plastics different than other un-metabolizeable (?) substances (dirt) that organisms have been accidentally ingesting since time immemorial? Some are probably toxic, but so are naturally occurring heavy metals, etc.

ars 5y ago

Most plastics are just water and CO2 in various combinations. A few (PVC) have some chlorine, but the vast majority could be burned, or digested by a bacteria, and emit just water and CO2.