Welcome, guest [login | register]

Posted by Bill S on November 18, 2007 at 2:04:34 pm EST
In reply to Water purification in extreme conditions posted by Bill S on October 19, 2007 at 11:58:04 am EDT

Rockwell's paper, like a lot of stuff in the Loma Prietan (the chapter of the Sierra Club I am a member of) is old stuff. Many of the Loma Prietan articles are often "summarized" poorly from other sources. Tests of water in the Sierra and other parts of the US and Canada have been ongoing for many years by highly qualified researchers and reported in the journals of the Wilderness Medicine Society. Paul Auerbach's small book Medicine for the Outdoors and his much larger book written for physicians give good summaries of the current state of research.

The results have shown some very surprising results (surprising compared to what you would intuitively expect). Some streams and other water sources close to civilization and along heavily used trails within a couple miles of popular trailheads (in many cases, frequented by fishermen) have extremely LOW levels of giardia, crypto, viruses, various bacteria (like salmonella, shigella, e. coli and campylobacter), and other critters that cause problems. Other sources far into the backcountry, including sources at high altitude that are rarely visited by humans, show extremely HIGH concentrations of giardia, crypto, viruses, various bacteria, and other organisms, enough to cause problems from even a cup or two of the water. In other words, apparently safe sources, with water that appears clear to the eye, sometimes test as highly problematic. According to the research, there is no obvious explanation that could be used as a clue to the backcountry traveller. But, again referring to the research published in refereed journals, the overall risk from the backcountry water in most of North America is low, even from front-country water, with the majority of cases of intestinal problems coming from poor sanitation in the preparation of the food (people failing to wash their hands before handling the food). But, since there is no easily spotted clue to the purity of the water, the advice is to always take precautions, such as boiling (actually heating to 158F/70C or hotter, the temperature used for pasteurization of food products, is sufficient, though boiling for 3 minutes even at the lower boiling temperature at 18,000 ft provides a wide margin of safety, according to the WMS sources), chemical treatment, or filtering. (that's like saying the risk of a serious car accident is low for any given trip, but you still should wear your seatbelt for that one drunk driver who might veer into your lane).

As Dave says, though, my original question has to do with water treatment in the African bush, where the water sources are shared with various animals that do not practice LNT. I have also discovered that even bottled soft drinks in the area to which we are headed, do not necessarily guarantee purity.

Replies

View: flat | threaded

There have been no replies

Post a Reply

Before replying, please read the complete thread.