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B Is rainwater harmful for us?

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  1. Jun 13, 2016 #1
    I've heard people say that if you come back from the rain and you're soaking wet (because of the rain water), you should take a bath to prevent any kind of illness.

    However, how can it be that rainwater can cause you harm, but the water in your home cannot? Or maybe, how does your home water prevent the illness that you might've gotten from the rainwater?

    Thanks!
     
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  3. Jun 13, 2016 #2

    berkeman

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    "I've heard people say" is not a valid way to start a thread in the technical PF forums. Can you please point to a mainstream reference that makes this assertion?
     
  4. Jun 13, 2016 #3

    ProfuselyQuarky

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    Well, when rain falls, it has to pass through the atmosphere which can contain a variety of contaminants. The water can pick up these chemicals and unclean things. The cleanliness of rain water really depends on your environment (e.g. is the air around your area particularly polluted, etc.). In polluted areas, there would be a good amount of contaminants like sulfur dioxide. But it only makes sense to consider this for drinking water.

    You're most likely never going to get sick from touching rain water. I never heard that before. Anyway, if the water was so horribly bad that you have to take a shower or something, you shouldn't even live in such a region to start with.

    The water that comes from our faucets is obviously different! Before it gets to your house, it's cleaned and filtered. And, depending on the type of home you have, that entire system might possibly be within your property (i.e. if a well supplies your water source).
     
  5. Jun 13, 2016 #4

    fresh_42

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    The logic goes as follows:
    wet ⇒ loss of body temperature by evaporation ⇒ being cold ⇒ reduced capability of immune system ⇒ more difficulty to fight viruses.

    Temperature or wetness alone does not have any effect. You need to catch a virus, too.
     
  6. Jun 13, 2016 #5

    phinds

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    In many places it's not really different because it is ONLY filtered and that just takes out macro level gunk, not bio-organisms. In many places spring water (which is almost directly rain water) is considered better than water drawn from an aquifer by a well.
     
  7. Jun 13, 2016 #6
    Well, it was just some of my friends talking and I wondered whether they were right or not.
     
  8. Jun 13, 2016 #7
    :D All right, thanks a ton for your help!
     
  9. Jun 13, 2016 #8

    ProfuselyQuarky

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    Yes, you are right.
     
  10. Jun 13, 2016 #9

    ProfuselyQuarky

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    By the way, I wonder if the bacteria that lives in clouds would affect rain water in negative way?
     
  11. Jun 13, 2016 #10

    phinds

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    Yes, we understand that. The point is, that's not a good reference for this forum. I understand that you were just looking for some informed opinion on what your friends said, but the point is that this forum is not here to debunk random nonsense spouted by random people out in the world. If you had done some research on your own and did not find a satisfactory answer, then you would at least have some valid (presumably) citations from which to springboard your question.
     
  12. Jun 13, 2016 #11
    Will keep that in mind for my future posts, thanks.
     
  13. Jun 13, 2016 #12

    phinds

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    Good. I also understand, by the way, that this forum's rules can seem a bit unfriendly but they are not meant to be, they are just meant to keep the focus on established science.
     
  14. Jun 13, 2016 #13
    While not technically correct, rain water collected in a clean barrel, as well as that which directly lands on you for that matter, is not too far removed from being equivalent to distilled water. Certainly, it will contain some particulates from nucleation (formation of the rain drop) as well as travelling through the atmosphere but this will in no way bring the mineral content of the rain water anywhere near equivalent to ground water or municipal water sources.

    I believe the tale to wash up after being out in the rain has more to do with hygiene related ideas accumulated over the history of human-kind, that it was noticed somewhere people in prior times were more likely to become ill after being in the rain. However, we've recently noticed that there really isn't a cause-effect correlation between illness and rain exposure and more likely the tendency to become ill is due to the body's temperature lowering as a result of evaporation making it more susceptible to some pathogens it likely already had been exposed to.


    With regards to the issue of forum etiquette, I don't see this as much different than something like "my boss and I were arguing about some MIL-SPEC" application to our product. What are your thoughts?" type of topics that pop up now and then. Besides, now you are going to take the words of strangers and present those to your friends.
     
  15. Jun 13, 2016 #14

    phinds

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    Excellent points.

    Not clear what your intent is with this statement. Are you being supportive of the forum etiquette or dismissive of it?
     
  16. Jun 13, 2016 #15
    I'm only saying I've seen threads / topics started in a similar manner without any comment by others. Also, a quick perusal of the TOC doesn't suggest this is not acceptable; I could be wrong, though.
     
  17. Jun 13, 2016 #16

    phinds

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    Had it been unacceptable, berkeman would have closed the thread. He and I are just saying that it's not appropriate, which is different from unacceptable, and yes, I've also seen threads started in similar manners before without comment but that doesn't make them a good idea.
     
    Last edited: Jun 13, 2016
  18. Jun 13, 2016 #17

    berkeman

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    We like for folks to do some research on their own before asking questions here. That helps them to get better at answering their own questions (an important skill in life), and helps others to respond better to the posted question. In this case, the OP could have used a Google search to get some initial information, and then could have posted links to their reading with questions about whether the claims made sense.

    In general, threads that start with just "I heard that" don't go very well. OTOH, "I read that _______ at this link _______, and haven't been able to find much more info about it" would be a better thread starter... :smile:
     
  19. Jun 13, 2016 #18

    sophiecentaur

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    This thread has been very heavy in its way of dealing with a perfectly valid but, perhaps not expertly put, post.
    It is and always has been what we call a "popular misconception" and anyone who has had a Mum tell them to come indoors this minute because it's raining can sympathise with bringing the subject up on a reputable Physics Forum. Doesn't PF ever try to debunk wrong theories? The theory no longer applied to well heeled western town dwellers and 'explorers'.
    In these days of microfibre and breathable clothes and central heating, the main risk is no longer as relevant as it was in the 'olden days'. There was a (well documented) time when, if you got your clothes wet, you would be cold, due to evaporation for many hours / days even (approaching hypothermia) and been subject to real infections as your body resistance to infections was lowered. That would have happened with rain or pure distilled water. Having a (warm) bath and putting on dry clothes would reverse the process. Rich people would have had access to this treatment whereas their servants and tenants would have had to 'just get on with it' and their life expectancy would have been accordingly shorter.
    PS. I watched Leonardo DiCaprio in 'the Revenant' last night. How was he supposed to have avoided hypothermia? I should like to know. His clothes were ringing wet most of the time and the rivers were full of melted snow. Good film tho'.
     
  20. Jun 13, 2016 #19

    berkeman

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    Not usually -- we prefer to just post links to other locations on the web with the debunking info, and close the PF thread. Like we do all the time with PMM discussions.

    This discussion isn't too bad, though. I just wish the OP had put a bit more effort in before asking the question. :smile:
     
  21. Jun 14, 2016 #20
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