Ask A Scientist© Weather Archive

name         Joe
age          old

Question -   Why can't I drink rain water?
Joe,

Normally you could drink rainwater without becoming ill.
However, rainwater contains pollutants, soil, plant parts,
insect parts, bacteria, algae, and sometimes radioactive
materials that the rain/snow has washed out of the air.
If filtered with one of the filtering systems that you
can buy in stores nowadays, and then boiled, you could
probably drink the water safely.  However, it is safer yet
to get your water from municipal water supplies or from wells
that are frequently tested.

David Cook
Argonne National Laboratory
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Since ancient times, the only sources of natural water that are recognized
as safe to drink are rain water and water from deep wells.  The trick is
that the rain water must be carefully handled so that it does not become
contaminated.  If it runs along the ground, it's anybody's guess what sort
of microbes and toxic elements it will pick up.  But if you put a clean bowl
out in the rain to collect the rain water, there's no reason you can't drink
the water from it.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois
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Hi Joe,

The only reason I could think of where you can't drink rain water is if you
have no mouth.

OK, enough joking.  In some third world nations, they drain rooftop rain
gutters into barrels to collect water for drinking.  Rain water might be a
little bit acid compared to water out of the ground or from rivers, which
are somewhat neutralized from contact with minerals, so you'd be missing
some of those minerals.

If you live in a really polluted city, it might be a good idea not to drink
rain when it just starts, as it's washing out all the particulate material
in the air (car exhaust, diesel fumes, dust, etc).  Other than that, I
can't think of why you shouldn't be drinking it.

Don

Donald Yee Ph.D.                San Francisco Estuary Institute
180 Richmond Field Station,     1325 South 46th St. Richmond, CA  94804
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There is no essential reason why you can't drink rain water. I think the
concern about drinking rain water has to do with the fact that in our
non-pristine environment the raindrops may have picked up some contaminant
on the way down from the clouds.

Vince Calder
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Dear Joe-

Most likely, you ARE drinking rain water..!  The water that comes from the
tap in your home at some point in the past fell as rain water (or snow). It
may have flowed into the ground to become part of the groundwater supply, or
may have arrived in resevoirs via rivers and streams. Usually this water is
treated to remove impurities and harmful organisms.

But you can collect rainfall and drink it also. It should be collected and
handled under sterile conditions, however. Much of the world's water supply,
especially in the tropics, comes from rain water.

Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
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