Multicellular organisms are highly parallel, trillions of cells in a human. Even inside a eukaryotic cell (gigantic compared to far smaller bacteria) there is a huge amount of parallelism and non-linearity like in some assembly line.

The discussions about some health consequences always come up with "death" as the binary outcome measure. This is so useless. There already is an effect for tiny amounts of molecules. Functions in cells work worse, and cells work worse. This affects all of your functions. Since you are only ever exposed to tiny amounts even when it accumulates - e.g. for heavy metals - all those small problems are either not noticed or attributed to age, which of course also advances.

I had the "benefit" of diagnosed mercury poisoning (gray zone - enough to warrant chelation treatment, university clinic researcher doctor who always forgot to send his - very moderate - bills unless I reminded him several times for a year each time, so no over-diagnosis for profit).

From a disappearing nodule in my thyroid that I had had for decades, unchanging, that suddenly disappeared within weeks of chelation to the great amazement of an endocrinologist who had recommended surgery and who ultra-sounded me twice because he could not believe it, to a huge long list of "minor" ailments that I had increased over the decades and that I had ignored and also attributed to age (I never bothered doctors, far from hypochondriac, never thought much of it), to my returning ability for abstract thought, to digestion going from delayed and stinky to perfect (really), from sleep problems to easy and perfect sleep, to never tired, soooo much went away. With the doctors permission and supervision I chelated far longer and far beyond what would have been justified officially, since it kept helping even though measured amounts were getting really tiny.

Only because I saw the contrast, which rarely anyone ever does because for most people it's a very very gradual slope downhill, or they believe it's "genes" or age, do I even consider environmental factors. I once saw a webpage from a decades-long inner medicine clinic doctor who opened a private practice - in which she offered purely psychological bullshit "treatments" that you see from "alternative medicine". Her reasoning, explained on her (old, clinic-time) website: It's either genes or psychology in her clinical experience, meaning you can hardly ever really do anything but mitigation. Environmental factors never entered her mind. (I have no doubt any cases she diagnoses as "real" will be referred to a clinic by her right away, so not critic on her person from me.)

Which make sense, because the science behind the many, many each very tiny amounts of chemicals and their influence is very hard. Diagnosing it on an individual level, and not just on a population level (the latter does not help a doctor when there is a concrete patient in front of them), is even harder. So as a public health administrator allocating funds I perfectly understand why it flies under the radar. Because individual doctors working with individual patients can't really do much of anything. That is then equated with "there is no problem" (or they would do something about it). Oh and the "they didn't die so it can't be so bad" attitude.

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Oh and by the way, completely non-scientific and my opinion after watching myself through many boring cycles:

- The common cold helps "getting stuff out". Significantly. I now wonder if eradicating it will have worse long-term outcomes for other issues. Also, not taking medicine to lower the symptoms for example for a good nights sleep might actually be better, the symptoms are part of that "getting stuff out". Yes it's very uncomfortable. It's horrible if you have to get up and go to work the next day.

- The best treatment by far are low stress (no alarms to wake you up to go to work when you would still sleep), sleep, rest as needed (during the day, just lying down and letting the mind go off somewhere - no reading or listening, the brain has to have "free time" to do things on its own - work from home is best!), walking (needed to get things moving, from my body experience the normal blood and ECF circulation is not sufficient.

- Changing sides left/right/left/right/... "I cannot find sleep" actually already is part of the brain's cleanup cycle! A lot of time spend in that phase may be an indicator that there is quite a bit. Clearly, having to get up for an early commute the next day adds stress and makes this hard to bear. But I recommend to accept it. It's a natural reaction, not something that should be suppressed. Yes it makes nights "work".

- The last 1-2 hours of sleep, that some (many) people find makes them more sleepy and groggy, are essential (okay, all phases are, but that's the one people like to skip).

- Being groggy after an afternoon nap is the same. Part of "getting stuff out".

You can call me out on any of this and I have no way to contradict you apart from anecdotes without any scientific value (nothing was measured, for example).