Long time lurker, first time poster. Yesterday my buddy’s girlfriend stated something that seems utterly ridiculous to me, but I can’t find any proof to refute her claim. She told me that water, in its pure form (without any minerals in it, 100% pure H2O), is deadly to humans. After having a good hard laugh, I told her she was full of it. I hopped online and so far I have been completely unable to find any credible (or even uncredible!) cites to refute her claim. I apologize for posting such a seemingly ludicrous question on The Straight Dope, but I need some help finding a few cites, thanks all!!!
The first question that comes to mind is just how pure it has to be to be lethal. As soon as it mixes with your saliva and stomach fluids it’s not pure anymore. As soon as it does anything it becomes impure. Also, what’s the LD50? In a way regular water could be seen as a mixture of “good water” with deadly pure water.
Maybe she thinks there are vital minerals that are only found in water, so that a person needs to drink a reasonable amount of impure water to survive. That could make some sense. However, I have never heard of such a thing. There is flouride which helps teeth but that’s not essential. I’d look at USDA documents about essential vitamins & minerals. There’s nothing about water nor are there warnings about drinking distilled or de-inozed water.
Get your affairs in order and then chug some distilled water right in front of her.
Well there is water intoxication.
http://en.wikipedia.org/wiki/Water_intoxication
Other than that, I cannot see what they could be talking about.
What you’re asking about is distilled water. You can buy this in the grocery store, and it’s perfectly safe to drink. Google the terms “distilled drinking water” to read to your heart’s content.
Does she have a particular claim you’d like us to address?
Thanks for all the cites folks, I agree that drinking distilled water isn’t dangerous, but then she throws cites like this at me, which I dont believe for a second.
That claims that distilled water is deadly because it absorbs more CO2 from the air and thus becomes more acidic. I don’t know if that’s true, but if it was a problem, a can of soda would kill ou since it’s pumped full of CO2 as well as having phosphoric acid. It may not be the best thing, but it’s not lethal.
I think calling that a cite is far too generous. It’s a collection of unsupported assertions.
You do realise you’ll never convince her, don’t you?
Yeah, pretty much. 
Bullshit. However…
There is a way for this to happen: if the water is pure heavy water, i.e., made with hydrogen that has additional neutrons, drinking this will kill you (professor told me this once, although I dunno how much you gotta drink). Ordinary water has some heavy water in it, but the percentage is very low, way too low to kill you.
Details on “heavy water” toxicity here: http://www.straightdope.com/mailbag/mheavywater.html
It’s surely not a quick and easy death…
This is patently false. But here are a few true things that could mislead a person:
- Many deionized water systems produce water that is chemically “pure” (meaning that no metals or ions would show up in an assay). But by definition, it also contains no chemicals that would kill bacteria. And water in such systems can sit in a cistern for a while before use. So, don’t go to a chemistry lab and suck off the deionized water tap; the bacterial contamination could make you quite ill even though the water would show as “pure” on an assay.
- There’s a difference between “pure” and “potable”. Just because water is purged of all contaminants doesn’t mean it tastes terribly good; it needs to be oxygenated somewhat. Of course you can drink underoxygenated water if it’s otherwise clean; you will just find it less palatable.
- There’s the old thing about hyponatremia where if you drink many gallons of water it will wash the sodium out of your body and you’ll have seizures or something. Technically that’s true, although it is not exactly true to say this is “poisoning”, it’s more like a nutrient deficiency.
- Tap water has fluoride and distilled water doesn’t, so if you only drink distilled water, obviously your teeth are not getting the fluoride goodies (more important for the kiddies though).
So, if you’re really trying to convince someone that pure water won’t kill them, you can present them with the above and say “perhaps this is what you really heard…”
Ho ho. If distilled water gets too acidic from absorbing CO2, then orange juice and carbonated drinks are weapons of mass destruction. Well, actually they’re not too good for you either, but if they were as bad as all that, we’d see mass graves next to convenience stores.
Only if inhaled in its room temperature state, or if it falls on your head below 32[sup]o[/sup]F. 
I tasted some once. It tasted the same as regular water, but it felt slightly thicker in my mouth - or at least I imagined that it did. (It actually is slightly more viscous, which you can tell if you’re preparing nuclear magnetic resonance samples in those thin glass tubes.)
:dubious: Um, if it’s full of deadly, deadly bacteria, then it probably wouldn’t show up as particularly pure on an assay. And what are those bacteria growing off of, if the water is so pure?
My statement was that “pure water can kill you” What I was referring to specifically was unnaturally pure H2O treated in a lab, NOT naturally occurring. For example: H2O created for the specific purpose of rinsing microchips and semiconductors. Most definitely NOT the distilled water you buy at your local grocery store. That still has impurities and non Hydrogen/ Oxygen elements in it; otherwise it would go for $500 a gallon and come in a glass container. I did not specify HOW MUCH it would take to kill you, or HOW LONG. It was just a $50 bet on whether my statement “(drinking) pure water can kill you” was correct…well DUH its correct.
Earlier Heavy water was mentioned (H2O with an extra neutron on the H) will kill you, so if it happened to be PURE heavy H2O my statement above would be correct, because it is PURE H2O and it CAN KILL YOU (although it would take a few days) – to the guy who drank it in the lab, a half a cup of 50% deuterium oxide wont kill you – which is probably the grade you had in your lab)
Hyponatremia is what CAN kill you from drinking too much water, and leaving your body low on salts. PURE water rapidly accelerates this process. Without ANY dissolved elements in the water, it can leach your body of salts. (Remember from chemistry a salt is simply a compound of metal and nonmetal, not necessarily nacl). Result: your brain swells (remember from chemistry what happens to your cells in a hypotonic solution) – you die.
The MSDS for water has the LD50 for a rat at >90mL/kg (orally)- This ALSO would make my statement above correct, but is not what I meant.
Again I am talking about 100% PURE H2O which can only be achieved in a chemistry lab, and even then can’t be 100% pure. I’m not even going to get into the H3O and OH ions that CAN ALSO KILL YOU – but aren’t defined as “water”
-Your Buddy’s EX-girlfriend
50% D2O wouldn’t have been remotely adequate for our purposes. I think it was 99% or so, but I wouldn’t swear to it - the bottle wasn’t brand new anyway, and D2O tends to mix with atmospheric water so it doesn’t remain pure for all that long. But judging by our nMR results, it was certainly far purer than 50%.
Cite? Certainly drinking enough pure water will kill you, as will drinking enough of what comes out of the tap. But I want actual evidence for this claim - as I read you, you’re suggesting that a toxic amount of pure water is somehow substantially less than a toxic dose of tap water. Since both are strongly hypotonic with respect to body cells, I don’t see how the minor quantity of dissolved minerals present in tap water is likely to make much difference in the long run.
Did this argument cause the boyfriend in question to be dumped?
If so, I’d say that while H[sub]2[/sub]O is only tangentially deadly, it can at least put a dampener on your love life.
In my HS chemistry lab we “made water” and to demonstrate that it was water the teacher swiped his finger across the inside of the beaker and drank it (the reaction only produced tiny droplets of water). So I think you’re wrong.
We’ve gotten this far on a thread regarding “pure water” without a single Dr. Strangelove quote? What the hell is wrong with you people?
Regarding the hazards of consumption of “pure” water, the claimant is taking is taking a nominally true statement–that “pure” unionized water will react with (or leech, if you prefer) a greater amount of salts before it comes to equilibrium–and using that statement to grossly and unjustifably exaggerate the health consequences of said substance. The statement “…I am talking about 100% PURE H2O which can only be achieved in a chemistry lab, and even then can’t be 100% pure,” implies that there is something uniquely deadly about “100% PURE H2O”, but that, say, 98% pure water combined with 2% tap water is somehow nontoxic. It’s not clear what the indicated threshold is here, but there’s no reason to believe that absolutely pure water is going to be significantly more hazardous than, say, distilled water, filtered water, or “pure rain water”.
As for hyponatremia, it is typically only a problem with people who are on long-term IV sustenance and, in rare cases, long distance runners who overhydrate without replunishing salts. The average person will have neither the appetite nor the volition to consume a sufficient amount of water–pure or otherwise–to deplete their body salt levels or dilute their blood to a life-threatening level.
The cite quoted above is absurd to the point of satire. To wit:
Distilled water is an active absorber and when it comes into contact with air, it absorbs carbon dioxide, making it acidic. The more distilled water a person drinks, the higher the body acidity becomes. According to the U.S. Environmental Protection Agency, “Distilled water, being essentially mineral-free, is very aggressive, in that it tends to dissolve substances with which it is in contact. Notably, carbon dioxide from the air is rapidly absorbed, making the water acidic and even more aggressive. Many metals are dissolved by distilled water.”
Well, yes, water is an “active absorber”; in fact, biochemists often refer to it as the universal solvent; it’s ability to readily form weak polar bonds and share hydrogens makes it valuable in many reactions, and its other material properties and ready availabilty and chemical simplicity make it ideal as a medium for the chemical processes of life. The notion that water will leach enough carbon or any other free element from the environment to become hazardously acidic, though, is laughable; a small amount of, say, CO[sub]2[/sub] might dissolve and form carbonic acid and reactive molecules like ethylene, amonia, et cetera, but it’s going to come to equilibrium quickly and with little concentration because these substances take too much energy to form spontaneously and are often to volitile to stay in state. Other claims stated in the article are equally spurious, but particularly perfidious is his comingling of the manifest health effects of soft drinks (with their profusion of carbonic acid, salts, organic compounds, stabilizers, et cetera) and unblended distilled water (which, despite the author’s implication, will not naturally form anything on the order of the amount of carbonic acid found in soft drinks). One might with equal logic complain of the health hazard of brass because it is used in the manufacture of firearm ammunition.
Now why don’t you just take it easy, Your Buddy’s EX-Girlfriend, and please make me a drink of grain alcohol and rainwater, and help yourself to whatever you’d like.
Stranger
(who is fighting to protect the purity and essence of our natural bodily fluids.)