Water & Filtration

Regardless of the cause, the fact remains: A "clear" mountain stream can harbor all kinds of pollutants, bacteria, and protozoa that you don't want to meet up close and personal. The best known is Giardia lamblia, a waterborne protozoan that spends part of its life cycle in mammalian intestines and can make humans violently ill. Other microscopic ne'er-do-wells include Cryptosporidium, which causes giardia-like symptoms, and bacteria such as E. coli and Salmonella.