# Could chlorinated water be keeping us healthy? **URL:** \ **Category:** Factual Questions\ **Created:** [February 7, 2012, 6:44pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101 "2012-02-07T18:44:28Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [February 7, 2012, 6:44pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/1 "2012-02-07T18:44:28Z")
In Chicago, the water is pretty well chlorinated at the filtration plant to cut down on all the bacteria. But when it comes out of the tap, there’s sometimes still a hint of the smell of chlorine. If you let it stand, which we don’t, the chlorine diffuses out, of course. But is there a chance that the chlorine is helping us combat germs even when it is inside us after we drink it? ---
**Author:** ![Quercus](https://avatars.discourse-cdn.com/v4/letter/q/7ab992/32.png) [@Quercus](https://boards.straightdope.com/u/Quercus)\ **Post date:** [February 7, 2012, 7:10pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/2 "2012-02-07T19:10:35Z")
I don’t think excess chlorine helps once it’s swallowed. By the time food gets to the intestines, any excess chloride would be damaging the intestines or beneficial bacteria more than any nefarious germs. However, the slight excess chlorine does keep nasties from growing in the pipes. Treatment plants will intentionally use excess chlorine so there’s still some disinfection potential for the water in the pipes. ---
**Author:** ![johnpost](https://avatars.discourse-cdn.com/v4/letter/j/f17d59/32.png) [@johnpost](https://boards.straightdope.com/u/johnpost)\ **Post date:** [February 7, 2012, 7:22pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/3 "2012-02-07T19:22:02Z")
tap water should be left open for a day for the chlorine to come out before watering plants, it can be harmful to them if not. you can let drinking water set until not stinky for yourself. your body has good defenses for most of what insults you in terms of bugs, that is why there are so many people alive. ---
**Author:** ![Michael63129](https://avatars.discourse-cdn.com/v4/letter/m/3da27b/32.png) [@Michael63129](https://boards.straightdope.com/u/Michael63129)\ **Post date:** [February 7, 2012, 8:05pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/4 "2012-02-07T20:05:45Z")
> [@johnpost](#): > > your body has good defenses for most of what insults you in terms of bugs, that is why there are so many people alive. In fact, when you eat something, the hydrochloric acid in your stomach will kill most bacteria (HCL isn’t quite the same as chlorine, but free chlorine reacts with water to form HCL; note that the “chlorine” put in tap water is usually a compound that releases free chlorine, otherwise it reacts too fast; bleach can be used to purify water during a disaster when no clean water is available); as far as chlorine itself being harmful, I have never heard of chloride toxicity (eating too much salt, sodium chloride, is toxic from the sodium), aside from chlorine gas (which, as stated, forms HCL with water in your lungs) and when part of certain compounds (e.g. PCBs). Although, there are concerns that chlorine can form toxic compounds when it [reacts with certain organic molecules](http://en.wikipedia.org/wiki/Chlorination#Drawbacks), but the risk is considered to be much smaller than from pathogens: > [@](#): > > Disinfection by chlorination can be problematic, in some circumstances. Chlorine can react with naturally occurring organic compounds found in the water supply to produce compounds known as disinfection byproducts (DBPs). The most common DBPs are trihalomethanes (THMs) and haloacetic acids (HAAs). Due to the potential carcinogenicity of these compounds, drinking water regulations across the developed world require regular monitoring of the concentration of these compounds in the distribution systems of municipal water systems. The World Health Organization has stated that the “Risks to health from DBPs are extremely small in comparison with inadequate disinfection.” (some water supplies use alternatives like ozone, which has its own byproducts, since all of these are strong oxidizers and highly reactive) ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [February 7, 2012, 9:10pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/5 "2012-02-07T21:10:51Z")
Aren’t most large city water supplies disinfected with Chloramine? If so, no amount of sitting out is going to remove the chlorine. You need a product designed to break the chlorine/ammonia bond. > **[Chlorine vs. Chloramine: What's in Your Water?](https://www.thesprucepets.com/difference-between-chlorine-and-chloramine-1381900)** > > Get info on the difference between chlorine and chloramine, and learn how it affects your aquarium. ---
**Author:** ![The\_Hairy\_One](https://avatars.discourse-cdn.com/v4/letter/t/c57346/32.png) [@The\_Hairy\_One](https://boards.straightdope.com/u/The_Hairy_One)\ **Post date:** [February 7, 2012, 9:42pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/6 "2012-02-07T21:42:55Z")
Chlorine reacts with water to form both hydrochloric acid and hypochlorous acid. It is the undisassociated hypochlorous acid molecule that is the effective disinfectant species. The hydrochloric acid disassociates to chloride and hydrogen ions. The hydrogen ions are mopped up by the buffering capacity of the source water. I don’t know about the States, but in the UK major water treatment works add an excess of chlorine to disinfect, trim the chlorine concentration back, then sometimes converted to monochloramine by adding a carefully controlled dose of an ammonium salt. Monochloramine is less effective as a disinfectant that hypochlorite but is much more persistant - which is why it tends to be used in large distribution networks. It also has a less noticeable taste/odour. The persistence is also why it’s a problem for aquarium owners. ---
**Author:** ![purplehorseshoe](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/purplehorseshoe/32/2996_2.png) [@purplehorseshoe](https://boards.straightdope.com/u/purplehorseshoe)\ **Post date:** [February 8, 2012, 12:37am UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/7 "2012-02-08T00:37:54Z")
> [@johnpost](#): > > tap water should be left open for a day for the chlorine to come out before watering plants, it can be harmful to them if not. > > you can let drinking water set until not stinky for yourself. > > your body has good defenses for most of what insults you in terms of bugs, that is why there are so many people alive. The last part is true, of course, but the first two parts are not - see the two posts above mine. You can let that water sit open till the cows come home and it won’t make a lick of difference in most areas. That said, few plants are so incredibly delicate that they can’t tolerate the same levels we’re getting. Your average office ivy is much tougher than that. ---
**Author:** ![GiantRat](https://avatars.discourse-cdn.com/v4/letter/g/e47c2d/32.png) [@GiantRat](https://boards.straightdope.com/u/GiantRat)\ **Post date:** [February 8, 2012, 11:02am UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/8 "2012-02-08T11:02:59Z")
[quote=“Michael63129, post:4, topic:612101”] In fact, when you eat something, the hydrochloric acid in your stomach will kill most bacteria (HCL isn’t quite the same as chlorine, but free chlorine reacts with water to form HCL; note that the “chlorine” put in tap water is usually a compound that releases free chlorine, otherwise it reacts too fast; bleach can be used to purify water during a disaster when no clean water is available); as far as chlorine itself being harmful, I have never heard of chloride toxicity (eating too much salt, sodium chloride, is toxic from the sodium), aside from chlorine gas (which, as stated, forms HCL with water in your lungs) and when part of certain compounds (e.g. PCBs). This wins the “Longest Sentence Ever Award.” But the info is dead-on, so no complaints. But damn, that’s a long sentence. ---
**Author:** ![TruCelt](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/trucelt/32/523_2.png) [@TruCelt](https://boards.straightdope.com/u/TruCelt)\ **Post date:** [February 8, 2012, 3:13pm UTC](https://boards.straightdope.com/t/could-chlorinated-water-be-keeping-us-healthy/612101/9 "2012-02-08T15:13:29Z")
> [@purplehorseshoe](#): > > The last part is true, of course, but the first two parts are not - see the two posts above mine. You can let that water sit open till the cows come home and it won’t make a lick of difference in most areas. That said, few plants are so incredibly delicate that they can’t tolerate the same levels we’re getting. Your average office ivy is much tougher than that. Well, yes and no. Using water with the chloramine intact to water your plants is harmful in one way - it kills any nitrifying bacteria whch may be building up in the soil. Much like in an aquarium, there are micro-organisms in soil that can break down ammonia into nitrite, and then another set can break down the nitrite into non-toxic nitrate. (well, far, far, less toxic, high nitrate levels can still be problematic.) So if you’ve ever pulled an ailing plant out of it’s pot and been assaulted by a sickening ammonia scent, that’s what happened. Many aquarists swear by fish-water as the ultimate boon for houseplants, and it’s true we tend to have super-healthy ones. But I’ve offten wondered whether the fertilization levels are really high enough to matter, or if it’s just the de-chlorinated water that makes such a difference.