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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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.
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.
So imagine our bodies as a tightly controlled system. Everything is connected and everything needs to work together in a specific way to help keep us alive and functioning. Harmful chemicals are so because they interact with something that interferes with the tightly controlled system. For example: cyanide goes into cells and stops them from producing energy. No energy means cell death, if enough cells die, tissues, then organs, then you die.
These chemicals are not cyanide, but any chemical has the potential to interfere with something it should not. Our bodies are sometimes able to compensate but you don’t want that. Bottom line, do not let unknown chemicals in your body if you can avoid it.
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.
I think one real risks is the bioaccumulation and biomagnification as the forever chemicals move up through the foodchains.
They might be completely safe at the level that everyone’s exposed to right now, but the issue with never going away is that the exposure levels will only keep going up.
Look at the case of the pesticide DDT in the USA. DDT is very safe (to most non-insects) at low levels, but it takes a very long time to break down.
What ended up happening is that the DDT sprayed on crops and farms would go into runoff or rodents and work it’s way into the ecosystem and start moving up the food chain. DDT accumulates in the bodies of fish and mice in normal levels, but animals higher in the food chain would consume dozens of these prey animals and it would start accumulating in higher levels in those animals.
In the case of DDT it was discovered that it was weakening the eggshells of Bald Eagles, and it nearly brought the animal to extinction.
Luckily, we were able to ban DDT in time, and it slowly broke down in the environment before the Bald Eagle went extinct, but a ‘forever chemical’ won’t be as easy to recover from.
The PFAS chemicals we know the most about are toxic at very low exposure levels to humans and wildlife. Some of them, like pfos are bioaccumulative, which means their concentration builds up in your cells over time.
Not all the toxicology is published, but PFOS scared a lot of people when they realized how low those levels were.
Medically, PFOS causes liver & thyroid damage, lowered fertility, increases obesity, hormone suppression and antibody suppression.
Each individual PFAS chemical has its own toxicology characteristics.
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.
I think one real risks is the bioaccumulation and biomagnification as the forever chemicals move up through the foodchains.
They might be completely safe at the level that everyone’s exposed to right now, but the issue with never going away is that the exposure levels will only keep going up.
Look at the case of the pesticide DDT in the USA. DDT is very safe (to most non-insects) at low levels, but it takes a very long time to break down.
What ended up happening is that the DDT sprayed on crops and farms would go into runoff or rodents and work it’s way into the ecosystem and start moving up the food chain. DDT accumulates in the bodies of fish and mice in normal levels, but animals higher in the food chain would consume dozens of these prey animals and it would start accumulating in higher levels in those animals.
In the case of DDT it was discovered that it was weakening the eggshells of Bald Eagles, and it nearly brought the animal to extinction.
Luckily, we were able to ban DDT in time, and it slowly broke down in the environment before the Bald Eagle went extinct, but a ‘forever chemical’ won’t be as easy to recover from.
So imagine our bodies as a tightly controlled system. Everything is connected and everything needs to work together in a specific way to help keep us alive and functioning. Harmful chemicals are so because they interact with something that interferes with the tightly controlled system. For example: cyanide goes into cells and stops them from producing energy. No energy means cell death, if enough cells die, tissues, then organs, then you die.
These chemicals are not cyanide, but any chemical has the potential to interfere with something it should not. Our bodies are sometimes able to compensate but you don’t want that. Bottom line, do not let unknown chemicals in your body if you can avoid it.
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