Why Not Just Drink the Water?
In the Great Outdoors, there are potentially four dangers of drinking
water straight from a source (assuming it's freshwater): chemical
pollutants, protozoa and larger parasites, bacteria, and viruses. In this
panel, we will first discuss a few of the
methods used in the backcountry to avoid these dangers, then give a brief
description of the toxins and pathogens found in water, and which method
is best suited to neutralizing each.
Methods of Purification
The oldest (and cheapest) method of purifying water is to boil it.
Boiling for five minutes will kill any biological hazards you could expect
to find. Most pathogens are actually long dead by the time the water
boils, but the five minute boil will g et them all (remember to add 1
minute to this time for each 1,000 feet above 10,000 feet). Boiling will
NOT neutralize chemical pollutants.
Chemical purification involves the use of iodine or chlorine to
kill the nasties in the water. This method is lightweight and relatively
inexpensive, but will not neutralize chemical toxins. In addition, you
must make sure that water at 25 deg. C (75deg. F) sits for 20-30 minutes
with iodine in it for purification to take place. If the water is colder
(as it usually is), you will need to let it sit longer - possibly
overnight for cold stream water. Warm the water against your body or even
on your stove if you want it to be purified faster. Once the appropriate
time has elapsed, the "band-aid" taste of iodine can be neutralized with a
small amount of ascorbic acid (vitamin C). Used properly, iodine will
kill most protozoa and all bacteria and viruses in water. After prolonged
use, some people develop thyroid problems, so be aware of this potential
side effect.
The latest rage in water purification is the use of filters, and a
large number of them are available .
There are a couple of things to bear in mind when shopping for filters.
First, only a system which includes a n iodine matrix will kill viruses
(see below). Second, a filter with pores larger than 0.2 microns - note
the location of the decimal point, as it is important - will let bacteria
through. The advantages of a filter are quick processing time (don't have
to wait for the pot to boil or the iodine to do its work) and
clean-tasting water (no iodine or vitamin C flavor). Some systems also
contain a carbon filter which will remove chemical toxins.
Finally, one system seldom used by hikers, but carried on seagoing
boats and possibly sea kayaks, is the reverse osmosis, or RO filter.
These systems are bulky, heavy, and expensive, but they will desalinate
seawater - a useful thing to be able to do
on a lifeboat, for example. Such filters will also remove all biological
contaminants, including viruses (viruses are considerably larger than the
exclusion limit of the RO filter).
What Might Hurt You
Chemicals in water could include inorganic contaminants (arsenic
and other heavy metals) or organic toxins (fertilizers and pesticides, for
example). In general, it is a bad idea to trust any purification system
to remove these, as even small quantit ies could ruin your day in a hurry.
The good news is that water sources in the backcountry are seldom
contaminated with appreciable levels of toxic chemicals. Take a good look
at the stream you're about to get water from. Are there fish in it? Is
there algae on the rocks? Crawdads on the bottom? Insects skimming the
surface? Plants growing along the banks? If yes, the water is probably
non-toxic, chemically speaking. If you're hiking in the desert, though,
and a trickle of water etching a groove in the rock is bubbling sulfur
from its barren depths, you should probably avoid it.
There are a number of parasites, both multicellular and
unicellular, which live in water. The most common ones in North America
are Giardia lamblia (see the CDC report later in this panel) and
Cryptosporidium. A good filter will remove both, and
boiling will kill them. Iodine is a reasonable second choice, but is a
bit chancy in water carrying Crypto. In third-world countries, the number
of parasites in the water is staggering, hence the hackneyed advice,
"Don't drink the water." Amoebae can cause dysentery ("Montezuma's
Revenge"), whipworm causes diarrhea and possible complications if not
treated, and roundworms (Ascaris lumbricoides) can be unpleasant, to
name a few. In some areas, such as the Philippines and Africa, you should
tr y to avoid ANY contact with river water, including swimming or washing
in unpurified water, as Schistosoma sp. is prevalent in these areas.
These tiny parasites bore directly into the skin, entering the bloodstream
and eventually setting up shop in either the intestine or the bladder. If left untreated or incorrectly diagnosed (a common problem, as symptoms only become manifest weeks or months after contact), the complications can be severe. As with Giardia, though, all of these parasites ar e removed by filtration or killed by boiling.
Bacteria are the second smallest pathogens in water, but they can
still be removed by a 0.2 micron filter. One frequently hears about water
being tested for Escherichia coli. While strains of this bacterium can be pathogenic, the vast majority are not, and it is, in fact, one of the species required in the intestine for digestion to occur (without bacteria, we would all die). Since it is present in large quantities in sewage, it is a good indicator strain to show when water has been contamina ted with sludge. There are plenty of other bacteria which are happy in the intestine, to the detriment of the host. All are sensitive to iodine treatment, are killed by boiling, and are removed by good filters.
The smallest parasites are viruses (please direct pointless
debates about whether or not they are "alive" to one of the sci.bio
groups). In true wilderness areas, pathogenic viruses are seldom found in
water, but the odds increase with population dens ity and poor sanitation
practices. Ordinary filters DO NOT remove viruses - in fact, Louis
Pasteur originally defined viruses as "filterable agents," meaning they
traveled easily through a 0.2 micron ceramic filter. Filters which have
an iodine matri x will kill viruses ("inactivate" them, if you prefer),
and iodine treatment will also work. Boiling is the most reliable way to
do away with viruses, though, and is strongly suggested in third-world
countries. The specific viruses you should worry about in water are
hepatitis A, rotaviruses, polioviruses, and echoviruses. All of these
will cause diarrhea, intestinal cramps, and discomfort about 48-72 hours
after contact, and complications could range from liver damage (for
hepatitis) to aseptic
meningitis and encephalitis (for echoviruses), and paralysis or death
(for polio). Yes, everyone is vaccinated against polio these days, but if
you were born before the vaccine, you could have problems with it.
Notes
1) Boiling your water is cheap and easy, and kills all known pathogens.
If you can manage the extra fuel necessary, this is the preferred method.
2) In the United States, you will seldom encounter anything in drinking
water which can kill you (make you sick, yes, but probably not kill you).
Be careful, but don't have a heart attack if you accidentally swallow some
unpurified stream water. The chances are thousands of times greater that
you will die in an automobile accident.
3) Anecdotal evidence which you see on the Net should largely be ignored,
especially the "I've used X method for 20 years and never had a problem"
variety. Since most water is not contaminated to begin with, just about
any method could appear to work for quite awhile.
4) This introduction was written by Alan Dove and edited by Eugene Miya
[well, I studied biological warfare] and Bill Tuthill. All three know the
subject matter, but this information is intended only for general
guidance. Anything that happens to you a s a result of following or not
following it is your own damned fault.
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