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Rain is liquid water in the form of droplets that have condensed from atmospheric water vapor and then precipitated—that is, become heavy enough to fall under gravity.

After reading the article Drinking Rain Water, I was wondering about its effects on human health.

So my questions are:

  • Is rain water safe for drinking after being collected in a safe, clean pot or vessel?
  • If it is safe, is it beneficial for your health OR more beneficial than normal filtered tap water or water from other sources like wells?
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    As raindrops fall, they sweep a lot of particulate matter out of the air. Definitely less pure than filtered water or some spring water. (Source is an environmental engineering course I took years ago - I don't have a reference handy.) – James McLeod Jun 25 '17 at 15:56
  • @JamesMcLeod - Yes , You are correct but ,my question assumes that its collected in a safe hygenic pot or vessal before being used.Anyway I will add this in question. – SwiftPushkar Jun 25 '17 at 16:24
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    @SwiftPushkar I believe he was referring to the particulate matter it collects from the air as it falls ("As raindrops fall...out of the air"). The hygiene of the vessel it is collected in has nothing to do with those particulates, unless the vessel is equipped with something to filter them out. – Dennis Jun 27 '17 at 2:07
  • FYI, Tasmania bottles and sells rain water. – Ken Y-N Jun 28 '17 at 1:58
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  1. Untreated rain water from well maintained roofs is generally safe to drink. Consumption of rainwater collected from ground catching systems without treatment is not recommended due to high levels of microbial contamination.

Untreated roof runoff has been widely used for drinking purposes for many years with very few reports of serious health problems. While health risks may be small, recent findings suggest there is little room for complacency and every effort needs to be taken to minimize rainwater contamination. Compared with most unprotected traditional water sources, drinking rainwater from well maintained roof catchments usually represents a considerable improvement and even if it is untreated it is generally safe to drink.

A number of pathogens harmful to health and disease outbreaks linked to rainwater sources have been documented. While serious, these outbreaks are all isolated and comparatively rare incidents. Nevertheless, they do provide an important warning regarding the potential hazards associated with drinking rainwater from sources which are poorly located, constructed or maintained.

Keeping leaves and organic material from accumulating in the tank and gutters will also help to prevent the stored rainwater from becoming too acidic and potentially leaching lead or other heavy metals from the tank walls, fittings or sludge deposits into the water. Source: Is rainwater safe to drink? A review of recent findings

  1. Inadvertent or accidental drinking of small quantities of rainwater is highly unlikely to cause adverse health effects.

Of the epidemiological studies conducted on rainwater to date, 2 have compared rates of gastroenteritis between populations of children (presumably a more susceptible population), and these unblinded studies showed no increased risk of illness associated with rainwater consumption. Our blinded study supports this conclusion and further indicates that adults have no increased risk of illness. Our results therefore suggest that consumption of untreated rainwater does not significantly contribute to community gastroenteritis incidence. This has important implications: at a minimum, inadvertent or accidental ingestion of small quantities of rainwater during showering and other water usage activities is highly unlikely to cause adverse health effects. Source: Drinking Rainwater: A Double-Blinded, Randomized Controlled Study of Water Treatment Filters and Gastroenteritis Incidence.

However, caution is advised for elderly and immune-compromised individuals when drinking untreated rainwater collected from roofs due to presence of pathogens.

Current estimates of health risk suggests that it would be prudent to disinfect roof-harvested rainwater, such as by the installation of a UV disinfection unit, boiling, or other forms of disinfection, before using it as potable water, especially for drinking. This would be especially prudent for the elderly and immunocompromised. Maintenance of good roof and gutter hygiene and elimination of overhanging tree branches and other structures where possible to prevent the congregation of animals are also recommended. Inclusion of giardiasis in the notifiable disease list in Queensland should be considered, given that G. lamblia was found in rainwater tank samples. Source: Health Risk from the Use of Roof-Harvested Rainwater in Southeast Queensland, Australia, as Potable or Nonpotable Water, Determined Using Quantitative Microbial Risk Assessment

At least 50% of the roof-collected rainwater samples from private dwellings exceeded the minimal acceptable New Zealand standards for contamination and 41% of the samples showed evidence of heavy faecal contamination. The likely sources of the faecal contamination were faecal material deposited by birds, frogs, rodents and possums, and dead animals and insects, either on the roofs or in the gutters, or in the water tank itself.In a significant number of supplies where we found heavy faecal contamination there was evidence of lack of maintenance; inadequate treatment of the water; poorly designed delivery systems and storage tanks; and failure to adopt even simple physical measures to safeguard the water against microbiological contamination. Many of the organisms that have been isolated from contaminated roof water have the potential for human pathogenicity, which under certain conditions can lead to infection and possibly disease outbreaks, notably gastrointestinal diseases from pathogens such Salmonella, Campylobacter, Giardia and Cryptosporidium. Source: The microbiological quality of roof-collected rainwater of private dwellings in New Zealand

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Before rain hits the ground, it goes through the air and can pick up particles that you don't want to be drinking. How much of an issue this is will depend on where you are. Rain water in urban cities can be pretty bad:

In most industrialized urban areas, the atmosphere has often been polluted to such a degree that the rainwater itself is considered unsafe to drink (Thomas and Greene 1993). In the U.S. the drinking water within 48km of urban centres is not recommended unless no other source is available (Grove 1993). Heavy metals such as lead are potential hazards especially in areas of high traffic density or in the vicinity of heavy industries (Yaziz et. al 1989, Thomas and Greene 1993). Organic chemicals such as organochlorines and organophosphates used in biocides can also contaminate rainwater.
Is rainwater safe to drink? A review of recent findings

Besides cities, there's also some concern about pesticides:

Although serious atmospheric contamination of rainwater is normally limited to urban and industrial locations, studies in the northeastern United States revealing the presence of pesticides and herbicides in rainwater do give some cause for concern (Richards et. al. 1987).
Is rainwater safe to drink? A review of recent findings

However, the article says, for most areas, "levels of contamination of rainfall are low" and most of the time contamination is due to what the water touches after it falls or how it is transported/stored.

Your link gives some good advice: boil the water and pass it through a water filter before drinking.

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Is rain water safe for drinking?

I bet if you took two groups of people, and gave one rain water and the other no water at all, after a week, the members of the rain-water group would be in much better health than the other.

And in fact, millions of people do live entirely off rain water they collect from their own roofs.

The pertinent question is:

And is it anyway beneficial for health OR more beneficial than normal filtered tap water or water from other sources like wells.?

I found surprisingly little hard research into this, but one paper found that collection and storage practices could lead to both biologic and metallic contamination, concluding:

Although water from roof-collected rainwater harvesting systems was generally within drinking water standards, regular testing should be encouraged to avoid potential health problems.

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

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    You need some sources to support your claims. "I bet" doesn't count for anything on this site. – Mark Jun 25 '17 at 16:27
  • @Mark -- I was merely explaining why I chose not to answer the OP's first question. If you would like to contribute something useful, you could try answering it yourself. – Malvolio Jun 25 '17 at 16:54
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    @Malvolio If you didn't want to answer the first question, you shouldn't have "answered" it. You should remove that section. – Laurel Jun 25 '17 at 18:30

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