SANITATION, ARTHROPOD AVOIDANCE, AND WATER DISINFECTION - Medicine for Mountaineering and Other Wilderness Activities - page 64

rapidlyitsometimesisthoughttobearepellent,andsomecommercialproductsarelabeled
repellents. When applied to clothing this agent has essentially no toxicity for humans.
A number of spray preparations are available. Clothing should be sprayed until damp
andallowedtodry.Sprayslasttwotothreewashings.Aftertheclothinghasdrieditisodor
free. Reportedly, approval is being sought for permethrin solutions in which clothing can
be soaked. Such applications should last forty to fifty washings.
WATER DISINFECTION
In recent years widespread microbial contamination of backcountry water sources in the
United States has been recognized. The single-cell Cryptosporidium parasite is essentially
ubiquitous,anditsuniversalpresencehasdictatedchangesinwaterdisinfectiontechniques
previously considered completely effective.
Developing countries build neither water systems that reliably supply uncontaminated
water for drinking and cooking nor sewage systems that prevent contamination of water
sources. Many residents are resistant to the organisms in the water as the result of continu-
ous contact since infancy, but deaths from diarrheal disease still number in the millions.
Most water in developing countries is contaminated. Tap water is usually contaminated,
even in the best hotels, although some establishments provide disinfected bottled water for
drinking. Tap water should not be used even for brushing teeth. Ice used to chill drinks is
usually unsafe. Even in remote areas, herdsmen and their cattle or sheep often contaminate
smallwildernessstreams.Allwaterthatistobeconsumedorusedinfoodpreparationmust
be disinfected.
Removing Particulate Material
River water, particularly glacial streams, often contains a large amount of suspended
particulate material that gives the water a “muddy” or terracotta color. (Glacial streams are
milky, gray, or grayish tan.) In the Grand Canyon and the upstream tributaries of the Co-
lorado River, the condition of the water depends on whether thunderstorms have recently
occurred upstream. The water is often clear. At other times, the Colorado is described as
“liquid mud,” and the silt can be removed from equipment only by vigorous scrubbing. It
frequently cannot be completely removed from clothing. Following a storm, side streams
are as muddy as the river.
If such water is placed in a container and allowed to stand, much of the suspended ma-
terial settles, although the process may take hours and the water may retain some color.
Filling buckets in the evening allows the water to be filtered the next morning. However,
allowing the water to stand may not be necessary. River water that appears quite muddy
can contain surprisingly little suspended material when viewed in small quantities, such as
in a water bottle or bucket.