Boiling
Boiling is the most reliable water treatment method on the trail. But boiling for how long? Signs on the trail warning hikers to boil water for 10 minutes appear to be excessive and a waste of fuel. After all, pasteurization (heating to only 143 degrees F for 30 minutes or 161 degrees F for 15 seconds) protects milk.
Ongerth's useful study showed that in water heated for 10 minutes, Giardia cysts were 100 percent destroyed at 158 degrees F. Most common bacteria respond similarly.
Bringing water to a rolling boil for one minute is good insurance and is recommended by many authorities. If as a last resort you must use pond water, which may be very turbid and contaminated with algae or particles, it is medically and esthetically advisable to prefilter water through one or two layers of cloth (for example, a handkerchief). Avoid pond scum, which sometimes contains toxins that have killed animals and may sicken people.
Iodine
Ongerth also demonstrated that iodine is an effective water disinfectant for Giardia when heating or filtration are not convenient or desired. The best of the soluble iodine preparations—Potable Aqua, Coghlan's Emergency Germicidal Drinking Water Tablets, and Polar Pure—were not as good for short treatment periods as either heat or filtration. Complete protection required eight hours contact in not-too-cold water (50 degrees F), although fairly good protection occurred in 30 minutes. Other iodine preparations, which included 2 percent tincture of iodine, were slightly less effective, but they were all effective after eight hours.
Halazone (no longer available) was the best of three chlorine preparations, which included commercial bleach. But all of these were much less effective than iodine; none gave complete protection even after eight hours. They are not recommended.
It is important to realize that the iodine action is highly temperature-dependent: The colder the water, the longer the time needed for purification. In any event, do not drink the water sooner than 10 minutes after treatment. The main problems with iodination are (1) it is recommended only for emergency use, (2) the water tastes bad (although the bad taste can be ameliorated with the use of pills available for that purpose), (3) it takes a lot of time, and (4) the iodination tablets have a limited shelf life.
The emergency use recommendation is based on the fact that although people with normal thyroid function can tolerate high amounts of iodine, if there is any thyroid deficiency, the iodine overload can cause problems. If you have any thyroid difficulty, consult your physician before using iodination for more than emergency purification of your water.
Treatment of Waterborne Diseases
Severe or prolonged diarrhea, gastrointestinal upset, nausea and vomiting suggest, among other possibilities, a diagnosis of waterborne infection caused by bacteria (E. coli, shigellosis [bacterial dysentery], typhoid, cholera), viruses (hepatitis A, rotaviruses, Norwalk-like viruses), protozoa (amebiasis, Giardiasis, Cryptosporidiosis), or other microorganisms. Diagnosis can be a difficult problem and if possible should be undertaken by a physician who can prescribe specific treatment for bacterial disease.
If diarrhea strikes on the trail, the symptomatic treatment includes drinking adequate fluids, taking Pepto-Bismol, and Imodium or Lomotil. I recommend carrying a few tablets of the latter two drugs.
Fortunately, most of the time the stomach, which secretes fairly concentrated hydrochloric acid and digestive enzymes, is an effective first line of defense against animate and inanimate intruders. However, hikers should neither count on this nor on the certainty that high mountain springs will escape contamination by animals or birds.
Always and only drink purified water!
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