Interestingly -- when it comes to toxicology it is not the substance that determines the poison but the dose. Water is still a toxin, we just have evolved ways to handle up to a certain amount of water per day before water poisoning takes hold. Everything is a toxin, we just have it in our bodies to handle some of it.

Wouldn't there be another word for this effect? It's not that water per se is toxic, is that eventually if you have a lot, your body "overflows". Being toxic is not an intrinsic property of the element, but is being derived by its quantity.

I would say water is a solvent rather than a toxin. The water we consume is just not pure water and has lots of minerals in it already diluting the solvency (?is this a real word) of the water. Truly pure water will strip the minerals right out of your hair: https://www.businessinsider.com/super-kamiokande-neutrino-de...

I would say that's not completely accurate either at a biological level. For example, if a neurotoxin merely disables sodium channels temporarily, that's different from a neurotoxin that somehow permanently disrupts or damages neurons (I believe some heavy metals work that way?). In the case of permanent damage, there is essentially almost no "safe dose", although I guess very small amounts will be negligible compared to background cell death. But you essentially want as little as possible, which is different from water, that goes from therapeutic to toxic at extreme amounts. (Not sure how TCE toxicity works)

Ethanol is only a "horrible toxin" if it's consumed in amounts that would be nearly or certainly lethal for any other solvent (save water). Human gut bacteria do not produce trichloroethylene.

As organic solvents go, ethanol is one of the safest — but it's too flammable for dry cleaners.