When I hear talking about forever chemicals, they are usually described as “chemicals are not affected by naturally occurring reactions, and that accumulate in the bodies of living beings”. By accumulating, they cause all sorts of health issues.
What I don’t understand is how they cause these health issues. If these chemicals do not participate in regular reactions, how do they cause issues?
I am not claiming that the research in the subject is wrong, I am missing the link between “these things don’t react with anything” and “these things still cause all sorts of health problems”.
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The ones I read the most about are not the final products (Teflon) but the surfactants used to help make the Teflon. For ELI5 purposes, a surfactant acts like a “soap”. It’s not really reacting but it’s changing the behavior of things near membranes.
Initial testing in the 1940s showed no *acute* toxicity but those were at low levels. Because your body can’t digest or metabolize it then the substances will just keep building up in your body over time. Too much of a foreign substance in your body will start to have an effect eventually, if only because it “gets in the way”. So, the long term effects have not been good. It eventually messes with your hormones. And clean up is really hard because the molecules are almost designed not to be cleaned up.
This might have been ELI4, maybe someone can chime in with more details.
The ones I read the most about are not the final products (Teflon) but the surfactants used to help make the Teflon. For ELI5 purposes, a surfactant acts like a “soap”. It’s not really reacting but it’s changing the behavior of things near membranes.
Initial testing in the 1940s showed no *acute* toxicity but those were at low levels. Because your body can’t digest or metabolize it then the substances will just keep building up in your body over time. Too much of a foreign substance in your body will start to have an effect eventually, if only because it “gets in the way”. So, the long term effects have not been good. It eventually messes with your hormones. And clean up is really hard because the molecules are almost designed not to be cleaned up.
This might have been ELI4, maybe someone can chime in with more details.
Lots of great but long answers here. Our understanding can be boiled down to “they get in the way”.
Sometimes they get in the way because they look like a key, so the body puts them into a particular lock, but since they aren’t the real key the door doesn’t open.
Sometimes they get in the way like a bunch of cars at rush hour when you’re just trying to get to work.
These chemicals are small, but so is everything else in your body, and there isn’t any room for unnecessary stuff. It causes all sorts of confusion and mayhem.
Depends somewhat on the specific chemical, but the general idea is that the chemical is stable relative to most naturally occurring compounds so does not react in nature with most of what it might encounter. Some of the chemicals can react with particular conditions or compounds that themselves are fairly stable, and in some cases, that is one possible reason they can be a problem (by destroying or modifying chemicals required for body functions).
Often, though, the problem compound is similar in form to some other useful compound (like, say some sort of hormone), at least in part, so it will interact with the things normally targeted by the hormone (or whatever compound it is similar to). It is a problem because it can either trigger responses that should not be turned on, or interfere with mechanisms (by blocking receptors) that ought to be initiated by the expected and useful compound being mimicked.
To understand this fully, you have to understand that many organic molecules are fairly large and made up of different functional groups at different locations on the larger molecule, and thus have a fairly specific shape and reactivity that varies from region to region in the molecule. Like a key only works for a matching lock, many organic compounds only “fit” together with its target, and it is the only compound produced by the body which will fit. Having a similar shaped compound from elsewhere that can fit the lock, well, that can be a problem and disrupt the way the system ought to be working, by locking, or unlocking, a chain of processes.
Most of the time, we measure a health effect but we don’t really know why. But a big reason is probably how PFAS partitions, or what substances it groups with in the body. Most substances group with water or fats. PFAS is weird because it groups with proteins. Since proteins are what perform most of our body’s chemical reactions, PFAS can have an effect by changing how well these proteins work. That might show up as changes in which of our genes are active, or it might affect the proteins that do other reactions more directly, like those which make fatty acids, or those which break down toxins in the liver. We don’t have a ton of direct evidence that I know of how these effects happen. But there are studies that try to model how PFAS interacts with certain proteins (“molecular docking” studies) to see where and how strong PFAS sticks to them.
So your body is broadly controlled by hormones. The hormone is a specific shape like a key, and it falls into specific shaped receivers in your body. When it does that, the signal is acted on.
Plastics as they break down can be these same shapes so they accidentally fit into the receiver slots for the hormones. Making your body do things it shouldn’t.
This is one serious way they effect us. An example is a plastic called BPA which just so happens to be the same shape as estrogen, so children of either gender drinking from cups made of it might grow boobs, or go into puberty at a young age
Not at all a doctor, but as I understand it:
Your body is a serious of complex pumps and tubes, built to move volumes of organic compounds to places they need to be.
If you put things in the tube that arent supposed to be there, you are going to be using some of that tube’s “bandwidth” to move something around that really isn’t supposed to be there.
Thats before you even consider how that something will react to the recipients waiting at the outflows from the tubes.
Say your heart is supposed to be pumping 100 abstract units of blood to your brain. As other stuff starts to build in your vascular system, the tube still moves 100 total abstract units, but now its 99 blood and 1 junk. This is fine, if the brain can make do, but over time as this junk accumulates, the throughput continues to drop, putting stress on the brain until finally it starts to break down due to lack of blood units per heart beat.
Basically your body fills up with junk that blocks it from doing what its supposed to.
The replies so far are accurate as far as possible mechanisms of toxicity, which is your question. But it helps to zoom out a bit- in order to do an experiment, you need a control group. Give one set of rats a dose of halogenated hydrocarbons, raise a second group of rats without them, compare their disease rates. But [these chemicals are in wild animals everywhere except Antarctica](https://www.theguardian.com/environment/2023/feb/22/animal-toxic-pfas-contamination-study) and even [on top of Mt. Everest.](https://www.theguardian.com/environment/2023/feb/22/animal-toxic-pfas-contamination-study) These chemicals are used in the factories that package food for lab animals, and they’re used in the farming process, so it is exceptionally difficult to raise lab animals without them. Now, one might start with the assumption that rats with *tiny* quantitates of these chemicals are going to show tiny effects, and larger doses will show larger but similar effects. That is how most toxins work. But other chemicals, like dioxin, the main contaminant in Agent Orange, and Bisphenol A, the hormone mimic in plastic, [have strongly non-linear dose- response curves.](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2475953/) Tiny doses may have the same response as larger doses, because they have already saturated the sensitive receptors they bind to. *Both of those chemicals are highly persistent in the environment and are sometimes described under the umbrella term “forever chemicals”, although that term is more often applied to precursors of chemicals like Teflon.
It was irresponsible to release these things without fully testing the health consequences, and now they are so widespread that it is difficult to raise a rat with zero exposure as a comparison subject. I think it is most reasonable to be only mildly alarmed, the rate of cancer has mostly increased only mildly since the chemicals have been invented, and most of that increase is due to people getting fatter and living longer. But comparison is difficult- cigarette smoke and coal smoke was everywhere when these things were invented. Before cigarettes and coal were widespread, people died young of infectious disease, and medical diagnosis was wildly inaccurate, so we really have only a foggy idea what the cancer rate was before the year 1900.
Lots of great but long answers here. Our understanding can be boiled down to “they get in the way”.
Sometimes they get in the way because they look like a key, so the body puts them into a particular lock, but since they aren’t the real key the door doesn’t open.
Sometimes they get in the way like a bunch of cars at rush hour when you’re just trying to get to work.
These chemicals are small, but so is everything else in your body, and there isn’t any room for unnecessary stuff. It causes all sorts of confusion and mayhem.
So a great example of this and something that my labmates studied during my doctoral degree was the development of AGEs (Advanced Glycation End Products).
These occur when sugars react with the amines present on amino acids (primarily lysine and arginine). This reaction is EXTREMELY slow, non-enzymatic and IRREVESIBLE. In summary, glucose/other sugar can exist in a linear form (although this is an extreme minority <0.0001%), this linear form can react with proteins and form a large milieu of covalent adducts/modifications.
As you age, these adducts build up in your eyes, collagen and other long-lived tissues and your body has no way of clearing them – as most of the methods for protein digestion require enzymes and these modifications are completely resistant to enzymatic degredation.
Thus, many people hypothesize that wrinkles forming in your skin is partially due to the cross linking of collagen by AGEs overtime and your bodies inability to build/rebuild it.
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